Mn-TiO2 oxide catalyst has been studied intensively for selective catalytic reduction (SCR) of NO with NH3 due to its extraordinarily good low-temperature performance. However, the mechanism of SCR on Mn-TiO2 still remains unclear, especially with regard to the decomposition pathway of the NH2NO intermediate and the reason for the decreasing N2 selectivity with the increasing of temperature. In this work, we attempt to provide a molecular level understanding of these questions via a combination of DFT and experimental study. A complete catalytic cycle of the SCR reaction was proposed based on a model in which Mn is doped into the TiO2(101) surface by quantum-chemical DFT+U calculations. In situ DRIFTS experiments were performed to provide evidence to the important intermediates as proposed in the reaction mechanism. The doping Mn enhances NH3 adsorption and activation due to its lower conduction band. NH2NO can decompose into N2 and H2O fast via a concerted H migration step. The decreasing selectivity with rising temperature can be explained by the deep oxidation of NH3. This study provides atomic-scale insights into the catalytic cycle and the important role of doping Mn in NH3–SCR reaction on Mn-TiO2 catalysts, which is of significance for the design of high activity low-temperature SCR catalysts.

•Different crystal alumina were synthesized from two sources of AlCl3 and Al(NO3)3.•The correlation between different crystal forms with HDS efficiency was discussed.•The NiMo/δ2-Al2O3 catalyst showed the best hydrotreating performance.•The synergy of texture property and MSI attributed to high activity of catalysts.•HDS and HDN efficiencies followed: NiMo/δ-Al2O3 > NiMo/γ-Al2O3 > NiMo/θ-Al2O3.A series of alumina with different crystal structures from γ-Al2O3 to θ-Al2O3 has been synthesized by precipitation method using aluminum nitrate and aluminum chloride hexahydrate, and the corresponding NiMo/Al2O3 catalysts were prepared based on above different alumina. The typical physic-chemical properties of the supports and series catalysts were characterized with XRD, BET, UV–Vis DRS, Py-IR, Raman and XPS characterization methods, and their catalytic activities were tested for FCC diesel hydrodesulfurization. The catalytic system was tested in hydrodesulfurization reactions of FCC diesel under atmospheric and high pressure (5 MPa). The NiMo/δ-Al2O3 catalyst prepared by aluminum nitrate exhibited the highest HDS and HDN efficiencies, 99.4% and 99.3% respectively, which were mainly ascribed to the concentrated pore size distribution, moderate MSI and higher degree of sulfidation.

•Boron doping increases both the surface acidity and surface basicity of carbon nitride.•Boron doped carbon nitride is active for cycloaddition of CO2 to epoxides.•Supporting on BA-15 gives conversion/selectivity >95% under solvent-free conditions.•A mechanism based on acid-base duality for CO2 cycloaddition reaction is proposed.•DFT calculations support the mechanism from the view point of energy.The cycloaddition of CO2 and epoxides to yield cyclic carbonate under solvent-free conditions is an eco-friendly way to utilize CO2 in environmental science and green chemistry. In this paper, we report that boron doped carbon nitride (BCN) is highly active and selective for such reactions. BCN, especially if supported on mesoporous silica SBA-15 (i.e., B0.1CN/SBA-15), shows above 95% conversion and selectivity for cycloaddition of CO2 and styrene oxide (SO) to yield styrene carbonate (SC), even under solvent-free conditions. That is mainly due to the acid-base duality induced by B doping, which enables the co-activation of CO2 and epoxide. A mechanism based on acid-base duality is proposed, where CO2 is activated on the basic >NH sites and SO is on the acidic −B(OH)2 sites through a hydrogen bonding. The co-activated CO2 and SO react with each other to yield the SC. Density functional theory (DFT) calculations were conducted to support the mechanism, which show that the co-adsorption of CO2 and SO on BCN is energetically favorable and the reaction follows the Langmuir-Hinshelwood mechanism. The BCN with acid-base duality provides an option for cheap, green and efficient catalysts for CO2 utilization.Download high-res image (173KB)Download full-size image

•Bifunctional catalysts of AuPd core-shell NPs decorated 3DOM TiO2 were fabricated by one-pot method.•The slow photon effect of 3DOM structure can enhance the light-harvesting efficiency.•Bimetallic AuPd NPs can promote the separation efficiency of photo-generated charge carrier.•AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction.•The molar ratio of Au/Pd can adjust photocatalytic activity and selectivity for CO2 reduction.The photocatalytic conversion of CO2 and H2O into value-added chemicals using sunlight is significant to solve energy crisis and environmental problems. In this work, a series of novel bifunctional catalysts of core-shell structured AuPd nanoparticles decorated 3DOM TiO2 (AuPd/3DOM-TiO2) w were successfully fabricated via a facile one-pot method of gas bubbling-assisted membrane reduction (GBMR). AuPd/3DOM-TiO2 catalysts show uniform 3D ordered macroporous structure, and the slow photon effect of 3DOM-TiO2 as a photonic crystal can enhance light-harvesting efficiency. AuPd nanoparticles are highly dispersed on the surface of 3DOM-TiO2 carrier. Since bimetallic AuPd nanoparticles with the relatively low Fermi level have good capacity of trapping electron, they can efficiently promote the separation of photogenerated electron-hole pairs in TiO2. The AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction with H2O to CH4 under light irradiation. Among the studied catalysts, Au3Pd1/3DOM-TiO2 catalyst exhibits the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 18.5 μmol g−1 h−1 and its selectivity to CH4 production by CO2 reduction is 93.9%. The possible mechanism of AuPd/3DOM-TiO2 catalysts for photocatalytic CO2 reduction is also proposed, and it would guide further design and synthesis of high efficient photocatalysts for CO2 reduction with H2O.Download high-res image (196KB)Download full-size image

•LaCoO3/ɤ-Al2O3/cordierite monolith catalyst was prepared by two-step method.•Alumina-washcoated catalysts presented a more uniform and more stable washcoat.•The weight loss for LaCoO3/ɤ-Al2O3/cordierite was less than 1 wt.%.•3DOM LaCoO3/ɤ-Al2O3/cordierite catalysts were prepared for the first time.•Nano LaCoO3/ɤ-Al2O3/cordierite catalyst gave the highest activity for soot combustion.The novel catalysts of LaCoO3/ɤ-Al2O3/cordierite monolith, LaCoO3/SiO2/cordierite monolith, LaCoO3/TiO2/cordierite monolith were prepared by using aluminum oxide, silicon dioxide and titanium dioxide nanoparticles as washcoat and monolithic cordierite as the monolithic ceramic substrate.The obtained samples were characterized by means of XRD, SEM, EDS, BET, and ultrasonic vibration test (Medi II Pselecta). The surface area of the cordierite monolith-supported LaCoO3/ɤ-Al2O3 is larger than those of LaCoO3/SiO2 and LaCoO3/TiO2. The coating of alumina, silica oxide and titania nanoparticles could increase the surface area of monolithic cordierite and also endue the coated layer with engineered structure. The results of thermal treatment experiment indicate that the good thermal stability of the ɤ-Al2O3 coating on the cordierite. The ultrasonic vibration test results showed that the washcoat was adhered to the substrate strongly. The weight loss for the samples LaCoO3/ɤ-Al2O3/cordierite (the most desired preparation protocol in this study) eventually reached about 3%, which was considered as a low weight loss.The LaCoO3/ɤ-Al2O3/cordierite monolith catalysts were successfully prepared by coating ready-made 3DOM LaCoO3 (perovskite-type oxides) catalysts onmonolithic cordierite substrate with a dip-coating method by employing aluminasol for the first time. The catalytic activities of a series of monolithic catalystsLaCoO3/ɤ-Al2O3/cordierite, LaCoO3/ɤ-Al2O3/cordierite (3DOM-catalysts), LaCoO3/SiO2/cordierite, LaCoO3/TiO2/cordierite were evaluated for soot combustion. Thenano LaCoO3/ɤ-Al2O3/cordierite catalysts gave the highest catalytic activity for soot combustion among the studied catalysts. The T10, T50, T90 over the LaCoO3/ɤ-Al2O3/cordierite catalyst were 199.4 °C, 340.5 °C, 405.3 °C, respectively, and sco2m was 99.9%.Coating and Catalytic Performance of LaCoO3/Washcoat/Cordierite Monolith Catalysts for Soot Oxidation.Download high-res image (108KB)Download full-size image

Micro–mesoporous composite Beta-KIT-6 (BK) material with cubic Iad mesoporous structure was synthesized, and then a NiMo/BK hydrodesulfurization (HDS) catalyst was prepared using BK as a support. Four kinds of model sulfides with different structures and molecular sizes, including thiophene, benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene, were chosen as the reactant probe molecules. The intra-particle diffusion effects on HDS of these four different model sulfides were investigated systematically over the novel NiMo/BK micro–mesoporous-supported catalyst under HDS reaction conditions. The changing rules of the catalyst effective factor (η) and effective diffusion coefficient (De) of model sulfides were investigated. The results showed that the η values of NiMo/BK catalyst in the HDS of different reactant molecules are higher than those of the traditional NiMo/Al2O3 owing to excellent mass transfer ability of the well-ordered NiMo/BK catalyst, and the De values decreased with the increasing molecular sizes of model sulfur-containing compounds. The relationship of effective diffusion coefficient (De) with molecule diameter to pore diameter ratio (λ) was further determined. Restrictive factors were correlated by F(λ) = (1 − λ)3.15 for NiMo/BK and F(λ) = (1 − λ)3.67 for NiMo/Al2O3 catalyst, indicating that large pore size is beneficial to the diffusion of macromolecular reactants.

The catalytic performance in heterogeneous catalytic reactions consisting of solid reactants is strongly dependent on the nanostructure of the catalysts. Metal-oxides core–shell (MOCS) nanostructures have potential to enhance the catalytic activity for soot oxidation reactions as a result of optimizing the density of active sites located at the metal–oxide interface. Here, we report a facile strategy for fabricating nanocatalysts with self-assembled Pt@CeO2−δ-rich core–shell nanoparticles (NPs) supported on three-dimensionally ordered macroporous (3DOM) Ce1−xZrxO2via the in situ colloidal crystal template (CCT) method. The nanostructure-dependent activity of the catalysts for soot oxidation were investigated by means of SEM, TEM, H2-TPR, XPS, O2-isothermal chemisorption, soot-TPO and so on. A CeO2−δ-rich shell on a Pt core is preferentially separated from Ce1−xZrxO2 precursors and could self-assemble to form MOCS nanostructures. 3DOM structures can enhance the contact efficiency between catalysts and solid reactants (soot). Pt@CeO2−δ-rich core–shell nanostructures can optimize the density of oxygen vacancies (Ov) as active sites located at the interface of Pt–Ce1−xZrxO2. Remarkably, 3DOM Pt@CeO2−δ-rich/Ce1−xZrxO2 catalysts show super catalytic performance and strongly nanostructure-dependent activity for soot oxidation in the absence of NO and NO2. For example, the T50 of the 3DOM Pt@CeO2−δ-rich/Ce0.8Zr0.2O2 catalyst is lowered down to 408 °C, and the reaction rate of the 3DOM Pt@CeO2−δ-rich/Ce0.2Zr0.8O2 catalyst (0.12 μmol g−1 s−1) at 300 °C is 4 times that of the 3DOM Pt/Ce0.2Zr0.8O2 catalyst (0.03 μmol g−1 s−1). The structures of 3DOM Ce1−xZrxO2-supported Pt@CeO2−δ-rich core–shell NPs are decent systems for deep oxidation of solid reactants or macromolecules, and this facile technique for synthesizing catalysts has potential to be applied to other element compositions.

We successfully synthesized 3D ordered macroporous (OM) Pt@CeO2−x/ZrO2 catalysts by a co-precipitation method. This series of catalysts have a well-defined 3D-OM structure. We investigated the activity of the 3D-OM Pt@CeO2−x/ZrO2 catalysts with different shell thicknesses, and systematically studied the adsorption and desorption of NO on the 3D-OM Pt@CeO2−x/ZrO2via in situ DRIFTS. The 3D-OM support enhances the contact efficiency between the solid reactant and catalyst, while the Pt@CeO2−x core–shell nanoparticles with strong Pt–CeO2−x interaction lead to a larger number of active species. With increasing the Ce/Pt molar ratio, the thickness of the shell becomes larger and the activity of Pt@CeO2−x/ZrO2 becomes lower. Among the as-prepared core–shell catalysts tested, the 3D-OM Pt1.0@CeO2−x/ZrO2-1 catalyst with the proper thickness of CeO2−x nanolayer shell showed the highest catalytic activity for soot combustion.

Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.

Mn-promoted CeO2 is a promising catalyst for the low temperature selective catalytic reduction of NO by NH3. We investigated the mechanism of this reaction for a model in which Mn cations are doped into the CeO2(111) surface by quantum-chemical DFT+U calculations. NH3 is preferentially adsorbed on the Lewis acid Mn sites. Dissociation of one of its N–H bonds results in the key NH2 intermediate that has been experimentally observed. NO adsorption on this NH2 intermediate results in nitrosamine (NH2NO) that can then undergo further N–H cleavage reactions to form OH groups. The resulting N2O product is desorbed into the gas phase and can be re-adsorbed through its O atom on an oxygen vacancy in the ceria surface, resulting from water desorption. Water desorption is the most difficult elementary reaction step. This redox mechanism involves doped Mn as Lewis acid sites for ammonia adsorption and O vacancies in the ceria surface to decompose N2O into the desired N2 product.

A series of vanadium-incorporated mesoporous materials V-KIT-6 with different vanadium contents were synthesized by combining a direct hydrothermal method with a pH adjusting method and applied as catalysts for the oxidative dehydrogenation of propane. The structures of the catalysts were characterized by various techniques including N2 adsorption–desorption, XRD, TEM, SEM, UV-vis DRS, H2-TPR and Raman spectroscopy. The results reveal that the pH value plays a key role in the structure of the catalysts and the incorporated content of vanadium in the synthesis process of V-KIT-6 materials. The framework-incorporation of various contents of vanadium under mild acidic conditions (pH = 5) preserves the well-defined 3D interconnected mesoporous features of KIT-6 and promotes the dispersion of vanadium oxide species. The V-KIT-6 catalysts show much higher catalytic selectivity and productivity to propylene in the oxidative dehydrogenation of propane than the corresponding supported vanadium catalyst. The highest selectivity sum of C2H4 + C3H6 (70.2%) is obtained over the 5V-KIT-6 catalyst; meanwhile, a high space-time yield (STYC3H6) of 3.91 kgpropylene kgcat−1 h−1 is obtained. The superior catalytic performance of the V-KIT-6 catalysts in the oxidative dehydrogenation of propane can be ascribed to the high concentration of highly dispersed active sites as well as the favorable property of mass transfer and accessibility of the active sites to the reactant molecules in the 3D interconnected mesopores.

Methanation and reverse water-gas shift reaction are two important reactions that could happen simultaneously during the process of CO2 reduction. Exploiting new catalysts with high selectivity towards one single process is highly desirable. It has been shown that isolated-Rh/TiO2 can selectively generate CO rather than CH4. A molecular level understanding would provide more insight into catalyst design for CO2 reduction. In the present contribution, the density functional theory method was employed to study the CO2 reduction reaction by H2 based on a Rh1/TiO2 (101) model. The co-adsorbed CO2 and H2 on the Rh atom can react with each other to form CO. The inhibition of further H2 adsorption on the CO pre-adsorbed Rh atom stops the following sequential hydrogenation of CO. This can explain the experimentally observed high selectivity of Rh1/TiO2 to CO. Different co-adsorption properties can be understood by the frontier orbital charge density symmetry matching principle. The same method has been extended to other metal systems (Ru, Pd and Pt) to identify candidate catalysts with high selectivity for CO2 reduction. Similar adsorption properties of isolated Pd with Rh may induce high selectivity towards CO. These results are expected to provide a prediction to find new selective catalysts for CO2 reduction.

•Different mesoporous silica materials have been successfully synthesized.•Highly ordered SBA-16@hexane with ultra-large pore sizes were obtained.•The synthesis mechanism of those mesoporous silica materials was discussed.•NiMo/Al-SBA-16@hexane with largest pores exhibited the highest DBT HDS efficiency.Ultra-large mesoporous silica materials using different micelle expanders including hexane, cyclohexane, 1,3,5-triisopropylbenzene and 1,3,5-triethylbenzene, have been successfully synthesized by the template of polymer surfactant of P123 (Aldrich, EO20PO70EO20). Among all the used micelle expanders, highly ordered cubic mesoporous silica material (SBA-16@hexane) with ultra-large pore size was obtained by using hexane. All the obtained samples were well characterized by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), nitrogen adsorption–desorption, UV–vis diffuse reflectance spectroscopy (DRS), H2-TPR, pyridine-FTIR, 27Al MAS NMR, GC–MS and Raman. The synthesis mechanism was also proposed. Compared with the conventional SBA-16 (6.31 nm) synthesized taking polymer surfactant of F127 (propylene oxide block copolymer) as the template, the as-synthesized SBA-16@hexane had a pore diameter of 15.1 nm with a highly ordered mesostructure, which was the largest one among all the reported pore sizes of SBA-16 materials. The corresponding hydrodesulfurization (HDS) catalysts of NiMo/Al-SBA-16@hexane, NiMo/γ-Al2O3, and NiMo/Al-SBA-16 were prepared by using different supports respectively, furthermore, their HDS performances were evaluated adopting dibenzothiophene (DBT) as the probe reactant. The DBT HDS efficiencies over these catalysts followed the order: NiMo/Al-SBA-16@hexane > NiMo/γ-Al2O3 > NiMo/Al-SBA-16. The high activity of NiMo/Al-SBA-16@hexane can be attributed to the superior diffusivity of the novel support of SBA-16@hexane with ultra-large pore size.

Engineering a bimetallic system with complementary chemical properties can be an effective way of tuning catalytic activity. In this work, CO oxidation on CeO2(111)-supported Pd-based bimetallic nanorods was investigated using density functional theory calculations corrected by on-site Coulomb interactions. We studied a series of CeO2(111)-supported Pd-based bimetallic nanorods (Pd–X, where X = Ag, Au, Cu, Pt, Rh, Ru) and found that Pd–Ag/CeO2 and Pd–Cu/CeO2 are the two systems where the binding sites of CO and O2 are distinct; that is, in these two systems, CO and O2 do not compete for the same binding sites. An analysis of the CO oxidation mechanisms suggests that the Pd–Ag/CeO2 system is more effective for catalyzing CO oxidation as compared to Pd–Cu/CeO2 because both CeO2 lattice oxygen atoms and adsorbed oxygen molecules at Ag sites can oxidize CO with low energy barriers. Both the Pd–Ag and Pd–CeO2 interfaces in Pd–Ag/CeO2 were found to play important roles in CO oxidation. The Pd–Ag interface, which combines the different chemical nature of the two metals, not only separates the binding sites of CO and O2 but also opens up active reaction pathways for CO oxidation. The strong metal–support interaction at the Pd–CeO2 interface facilitates CO oxidation by the Mars–van Krevelen mechanism. Our study provides theoretical guidance for designing highly active metal/oxide catalysts for CO oxidation.

The reaction mechanism of selective catalytic reduction (SCR) of NO with NH3 on W-doped CeO2 catalysts was systematically investigated using density functional theory calculations corrected by on-site Coulomb interactions (DFT+U). A complete catalytic cycle was proposed, which consists of four steps, namely (i) Lewis acid site reaction, (ii) Brønsted acid site reaction, (iii) oxygen vacancy reaction, and (iv) catalyst regeneration. The calculated key intermediates in these four steps are in good agreement with previous experimental results, which indicates that our suggested catalytic cycle is rational. The catalytic nature of W-doped CeO2 catalysts for NH3-SCR reaction was discussed by analyzing the role of oxygen vacancy, the synergistic effect between surface acidity and reducibility, and the difference from NH3-SCR reaction on V2O5-based catalysts. Our results show that the oxygen vacancy on the surface which creates two Ce3+ cations plays a critical catalytic role in the NH3-SCR reaction, where adsorbed N2O22– species can be readily formed and then acts as a precursor for SCR reaction, opening a unique reaction pathway. The formation of adsorbed NO2 species on W-doped CeO2 facilitates the SCR reaction via Langmuir–Hinshelwood mechanism with a relative low energy barrier. This study provides atomic-scale insights into the catalytic cycle and the important role of oxygen vacancy in NH3-SCR reaction on W-doped CeO2 catalysts, which is of significance for the design of highly active ceria-based SCR catalysts.

A series of photocatalysts of three-dimensionally ordered macroporous (3DOM) TiO2-supported core–shell structured Pt@CdS nanoparticles were facilely synthesized by the gas bubbling-assisted membrane reduction-precipitation (GBMR/P) method. All the catalysts possess a well-defined 3DOM structure with interconnected networks of spherical voids, and the Pt@CdS core–shell nanoparticles with different molar ratios of Cd/Pt are well dispersed and supported on the inner wall of uniform macropores. The 3DOM structure can enhance the light-harvesting efficiency due to the increase of the distance of the light path by enhancing random light scattering. And the all-solid-state Z-scheme system with a CdS(shell)–Pt(core)–TiO2(support) nanojunction is favourable for the separation of photogenerated electrons and holes because of the vectorial electron transfer of TiO2 → Pt → CdS. 3DOM Pt@CdS/TiO2 catalysts exhibit super photocatalytic performance for CO2 reduction to CH4 under simulated solar irradiation. Among the as-prepared catalysts, the 3DOM Pt@CdS/TiO2-1 catalyst with the moderate thickness of a CdS nanolayer shell shows the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 36.8 μmol g−1 h−1 and its selectivity for CH4 production by CO2 reduction is 98.1%. The design and versatile synthetic approach of the all-solid-state Z-scheme system on the surface of 3DOM oxides are expected to throw new light on the fabrication of highly efficient photocatalysts for CO2 reduction to hydrocarbon.

A series of PtSnAl/SBA-15 catalysts were prepared by incipient-wetness impregnation and their catalytic performance was tested for propane dehydrogenation. The catalysts were characterized by XRF, XRD, BET, TEM, UV-vis DRS, NH3-TPD, O2-TPO, 27Al MAS-NMR, XPS and in situ Raman analyses. The addition of aluminum enhances the interaction of the Sn support and consequently stabilizes the oxidation state of Sn during the propane dehydrogenation reaction. The acid centers formed by aluminum addition show close contact with metal centers (Pt), which favors the synergistic effect of the bifunctional active centers. High catalytic performance over PtSnAl0.2/SBA-15 was obtained, and one-pass propane conversion and propene selectivity are 55.9% and 98.5%, respectively. Moreover, the in situ Raman results indicated the faster coke formation rate of PtSnAl0.4/SBA-15 than that of PtSnAl0.2/SBA-15, which may be accelerated by strong acid sites by excess aluminum addition.

A series of cadmium sulfide (CdS)/triptycene-based polymer (NTP) nanocomposites was fabricated via a facile precipitation process by using Cd(OAc)2, Na2S, and prefabricated NTP as raw materials. The photocatalytic hydrogen-generating capabilities of the novel CdS-NTP nanocomposites have been investigated in the presence of a sacrificial reagent. After hybridization with NTP, the rate of visible-light-driven hydrogen production of CdS-NTP is 10 times higher than that of pure CdS prepared under the same conditions. The photocorrosion of CdS is simultaneously suppressed and the composites show high stability. The high surface area and stable covalent structure of NTP confines the CdS quantum dots and prevents aggregation, thus increasing the catalytically active sites and enhancing the photocatalytic performance of the hybrid nanocomposites. This work demonstrates a high potential of using porous triptycene-based materials to develop multifunctional porous materials for semiconductor-based photocatalytic hydrogen evolution.

Three-dimensionally ordered macroporous (3DOM) SiO2 was synthesized by a colloidal crystal template (CCT) method, and 3DOM SiO2-supported transition metal oxides catalysts were prepared by a facile incipient-wetness impregnation method. The as-prepared catalysts show well-defined three-dimensionally ordered macroporous structures. The transition metal oxides formed different sizes of nanoparticles and loaded onto 3DOM SiO2. The as-prepared catalysts show high catalytic activities for soot combustion. Among the studied catalysts, the 3DOM MnOx/SiO2 catalyst (molar ratio of Mn to Si is 1:4) shows the highest catalytic activity among the studied catalysts, e.g. T10, T50 and T90 are 297, 355 and 393 °C, respectively, and SmCO2 is 95.5%. The catalytic performances of 3DOM SiO2-supported transition metal oxide catalysts are mainly controlled by three factors: the macroporous effects of the 3DOM structure, the redox properties of transition metal oxides and the sizes of transition metal oxide NPs. 3DOM SiO2-supported transition metal oxide catalysts are promising for practical applications in soot combustion owing to high activity and low cost.

Aluminum-modified 3D mesoporous TUD-1 materials (denoted as Al-TUD-1, abbreviated as AT) were successfully synthesized by a sol–gel method using TEA and TEAOH as the co-template. Several analytical techniques such as XRD, N2 physisorption, TEM, NH3-TPD, H2-TPR and UV-vis DRS were used to characterize the typical physico-chemical properties of Al2O3–AT composite supports and their corresponding catalysts. The characterization results indicated that most of the aluminum species was partially incorporated into the framework of the TUD-1 silicate network, and the as-synthesized material had a uniform pore size distribution, high surface area and high pore volume. The catalytic performances of hydrotreating were evaluated by using PetroChina Hohhot petrochemical company FCC diesel as the feedstock. Among the series catalysts of NiMo/Al2O3–AT-m, the catalyst with 30 m% AT in the support exhibited the highest HDS conversion, which was as high as 97.42%. Moreover, the influence factors in the synthetic process of the Al modified TUD-1 such as Si/Al ratio, heat treatment time and heat temperature were systematically studied and the corresponding supported NiMo series catalysts showed good hydrotreating performances. The catalyst with the Si/Al ratio of 50 in AT, heat treatment time of 18 h and heat treatment temperature of 180 °C exhibited the highest HDS (97.56%) and HDN (99.63%) efficiencies, respectively.

A series of PtSn/SBA-15 catalysts with different metal loading amounts were prepared by an incipient-wetness impregnation method and their catalytic performances were tested for propane dehydrogenation. The catalysts were characterized by means of XRD, BET, TEM, UV-Vis DRS, O2-TPO, H2-TPR, XPS and Raman spectroscopy. The catalytic activity for propane dehydrogenation increases with an increase in the loading amount of metal, and it remained stable when the Pt loading amount reached 1 wt%. It is found that the state of Pt or Sn in the catalysts varies with changes in metal loading. When the loading of Pt and Sn exceed a certain amount (Pt 1 wt% and Sn 2 wt%), the state of Pt and Sn changes apparently with the more oxidative Pt and more reduced Sn. The changes of the state of Pt and Sn influence the catalytic performance of these catalysts. Moreover, the size of the PtSn nanoparticles increases with increasing amounts of Pt and Sn, which also results in a change in the catalytic performance. The Pt1Sn2/SBA-15 catalyst shows the highest initial activity, which results from an increased amount of active sites, the high dispersion of PtSn nanoparticles and the favorable state of the Pt and Sn species.

Understanding the interfacial effects of metal/support catalysts is of great significance in heterogeneous catalysis. In this work, we performed density functional theory calculations corrected by on-site Coulomb interactions (DFT+U) to study CO oxidation on a CeO2(111)-supported Pd nanorod. Three different reaction mechanisms for CO oxidation were systematically studied, namely the Pd–Ce3+ dual sites mechanism, the Mars-van Krevelen (M-vK) mechanism, and the Pd-only mechanism. On the basis of energetic analysis, we concluded that the dominant reaction pathway at low temperatures is the Pd–Ce3+ dual sites mechanism, whereas the M-vK mechanism would be dominant at higher temperatures. The interfacial effects play a crucial role and strongly affect the catalytic activity in these two mechanisms. The origin of the interfacial effects can be understood by analyzing the geometric and electronic properties. From the geometric perspective, the interaction between Pd nanorod and ceria support elongates the Ce–O bonds at the interface, enhancing the mobility and activity of interfacial lattice O atoms. From the electronic perspective, there occurs electron transfer from the Pd nanorod to the interfacial Ce4+ cation, leading to the formation of Ce3+, and subsequent electron transfer from Ce3+ to the adsorbed O2 at the Pd–Ce3+ dual sites significantly promotes the formation of active oxygen species for CO oxidation. Our study provides atomic-scale insights into the nature of active sites and the interfacial effects that determine CO oxidation on Pd/CeO2 catalysts.

CoMo catalysts supported on Beta-MCM-48 were prepared by different impregnation methods and calcination conditions with the addition of citric acid (CA). The addition of citric acid resulted in an increase of the catalytic activities in gasoline hydroupgrading, which was correlated to the formation of Mo–CA complexes, leading to higher MoS2 dispersion degrees and more amounts of Co–Mo–S active phases. The as-synthesized catalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and the corresponding catalytic performance of FCC gasoline hydroupgrading was evaluated. The results showed that different impregnation methods and calcination conditions had a certain influence on their catalytic performance. In this research, CA-CoMo/ABM48-S catalyst obtained by two-step impregnation method and air-calcination had the shortest average length of 3.0 nm and the moderate stacking degree of 2.6, therefore, it made a good balance in hydrodesulfurization (HDS), hydroisomerization and aromatization activities, as a result it exhibited the highest HDS efficiency (95.0 %) and the lowest RON loss (0.5 unit).

Perovskite oxides with formula ABO3 or A2BO4 are a very important class of functional materials that exhibit a range of stoichiometries and crystal structures. Because of the structural features, they could accommodate around 90% of the metallic natural elements of the Periodic Table that stand solely or partially at the A and/or B positions without destroying the matrix structure, offering a way of correlating solid state chemistry to catalytic properties. Moreover, their high thermal and hydrothermal stability enable them suitable catalytic materials either for gas or solid reactions carried out at high temperatures, or liquid reactions carried out at low temperatures. In this review, we addressed the preparation, characterization, and application of perovskite oxides in heterogeneous catalysis. Preparation is an important issue in catalysis by which materials with desired textural structure and physicochemical property could be achieved; characterization is the way to explore and understand the textural structures and physicochemical properties of the material; however, application reflects how and where the material could be used and what it can solve in practice, which is the ultimate goal of catalysis. This review is organized in five sections: (1) a brief introduction to perovskite oxides, (2) preparation of perovskite oxides with different textural structures and surface morphologies, (3) general characterizations applied to perovskite oxides, (4) application of perovskite oxides in heterogeneous catalysis, and (5) conclusions and perspectives. We expected that the overview on these achievements could lead to research on the nature of catalytic performances of perovskite oxides and finally commercialization of them for industrial use.Keywords: catalysis; characterizations; perovskite oxide; preparation; surface morphology

Hierarchical porous materials especially the silica-based ones are undergoing rapid development due to potential applications in the fields of catalysis, adsorption, separation, and biomedical processes. Although various synthesis methods involving emulsions, colloids, and surfactants have been reported, synthesis of hierarchical porous silicas (HPS) with complex mesophase transformations by using a four-component microemulsion (surfactant/cosurfactant/oil/water) templating approach is still challenging. Herein, we have successfully synthesized porous silica materials by introducing n-butanol (Bu) as the cosurfactant and 1,3,5-trimethylbenzene (TMB) as the oil component in a four-component P123–n-butanol–1,3,5-trimethylbenzene–water system. By simply increasing the molar ratio of Bu to TMB continuously while keeping a fixed mass of TMB in the mean time, mesophase transformations, progressing from mesocellular foam (MCF) via a vesicle-like structure to an ordered 2D hexagonal structure (SBA-15), can be observed. Moreover, an opposite phase transformation process was also proved by gradually increasing the molar ratio of TMB to Bu by maintaining a certain value for the Bu content in the initial system. All the mixed phase silica materials including hexagonal–vesicle, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type show hierarchically porous structures. The mechanism for the mesophase transformation was proposed and a micelle/microemulsion method with bimodal templates was put forward to form hierarchical porous silicas with a mixed phase of the MCF–disordered-SBA-15-type structure. Furthermore, a series of Al-containing mesoporous silicas with different structures (hexagonal, vesicle, MCF, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type) were used as catalyst supports for dibenzothiophene hydrodesulfurization. The NiMo/Al-hierarchical porous silica catalyst with pore structures of MCF–disordered-SBA-15-type displayed the best hydrodesulfurization performance among all the studied catalysts.

The Pd–Ce–Zr solid solution catalysts were in situ synthesized by a sol-evaporation induced self-assembly (SEISA) method. The catalytic performances of the as-prepared catalysts for CO oxidation and their physicochemical properties were investigated with various characterization techniques. The catalysts with low doping amount of Pd exhibited unique thermal stability and high activity toward CO oxidation. The CO oxidation activities of the catalysts showed a volcano type relationship with the content of Pd doping in Ce–Zr oxides. Pd–Ce0.8Zr0.2O2 with 1.0% Pd doping gave the highest catalytic activity. Its CO complete conversion temperature was 110 °C with a turnover frequency of 1.52 s–1. Density functional theory (DFT) calculations suggested strong effects of Pd doping on the crystal structure, charge distribution and formation of oxygen vacancy of the Ce-based catalysts. The calculations also suggested that CO oxidation on Pd doped Ce-based catalysts follows Eley–Rideal mechanism, and the direct reaction of CO with a surface oxygen atom appears to be the main pathway of the oxidation.

Three-dimensionally ordered macroporous (3DOM) MnxCe1–xOδ oxides with different ratios of Mn to Ce were successfully synthesized by colloidal crystal template (CCT) method, and 3DOM Pt/Mn0.5Ce0.5Oδ with varied Pt loadings were prepared by in situ ethylene glycol (EG) reduction method. 3DOM MnxCe1–xOδ supports exhibited well-defined 3DOM nanostructure, and Pt nanoparticles (NPs) with 1–2 nm size were evenly dispersed on the inner walls of uniform macropores. Among 3DOM MnxCe1–xOδ catalysts, 3DOM Mn0.5Ce0.5Oδ showed excellent catalytic activity for soot combustion; i.e., T50 is 358 °C and SCO2m is 94.2%. 3DOM Pt/Mn0.5Ce0.5Oδ catalysts exhibited higher activity than 3DOM MnxCe1–xOδ and 3 wt % Pt/Mn0.5Ce0.5Oδ showed the highest catalytic activity for soot combustion (T50 is 342 °C and SCO2m is 96.7%). Macropores effect, synergistic effects between Mn and Ce, and synergistic effects between Pt and Mn0.5Ce0.5Oδ support are contributed to high catalytic activities of as-prepared catalysts.

3D ordered macroporous (3DOM) TiO2 was synthesized by the method of colloidal crystal template (CCT) using tetrabutyl titanate as precursor solution, and the photocatalysts of the 3DOM TiO2-supported CeO2 nanolayer with different weight ratios of CeO2 to TiO2 were successfully prepared by the gas bubbling-assisted membrane precipitation (GBMP) method. The catalysts were systematically characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury intrusion porosimetry (MIP), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectra (PL). The slow light effect of photonic crystal (3DOM structure) can enhance absorption efficiency of solar irradiation. Moreover, the introduction of CeO2 nanolayers can effectively extend the photoresponse from UV to visible region and improve the separation of photogenerated electron–hole pairs. The photocatalytic activities for the reduction of CO2 with H2O were evaluated by the production of main product (CO). 3DOM CeO2/TiO2 photocatalysts exhibit high catalytic activity for the photocatalytic reduction of CO2 with H2O under simulated solar irradiation.

The ultrafine Ce-based oxide nanoparticles with different element dopings (Zr, Y) were synthesized by the method of micropores-diffused coprecipitation (MDC) using ammonia solution as the precipitation agent. The activities of the catalysts for soot oxidation were evaluated by the temperature-programmed oxidation (TPO) reaction. Ce-based oxides prepared in this study exhibited high catalytic activity for soot oxidation under the condition of loose contact between soot particles and catalysts, and the catalytic activity of ultrafine Ce0.9Zr0.1O2 nanoparticle for soot combustion was the highest, whose T10, T50 and SCO2m was 364, 442 °C and 98.3%, respectively. All catalysts were systematically characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brumauer-Emett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). It was indicated that the MDC method could prepare the ultrafine Ce-based oxide nanoparticles whose the crystal lattice were perfect, and the BET surface area and average crystal size of the ultrafine nanoparticles changed with the different element dopings (Zr, Y). The H2-TPR measurements showed that the ultrafine Ce-based oxide nanoparticles with the doping-Zr cation could be favorable for improving the redox property of the catalysts.The nanostructure effect of ultrafine Ce-based oxide nanoparticle catalysts can enhance the catalytic activity for soot combustion through improving the contact efficiency between soot particles and catalysts

•Novel porous material of L-SBA-15(LS) was synthesized using solid silica–alumina.•LS based catalyst exhibited superior HDS efficiency and preserving ability of RON.•The synergy between texture and acidity of LS improved the catalytic performance.A micro/mesoporous composite L-SBA-15 (LS) material was successfully in situ synthesized using low-cost solid silica–alumina microspheres by a two-step hydrothermal crystallization method, and the as-synthesized material was used as support additive to prepare the hydro-upgrading catalyst for fluid catalytic cracking (FCC) gasoline. LS and the corresponding catalyst CoMo/LS-γ-Al2O3(CoMo/LSA) were characterized by means of XRD, SEM, TEM, nitrogen adsorption, 27Al MAS NMR and Py-FTIR. The physicochemical properties of the CoMo/LSA were compared with those of CoMo/Al2O3 catalyst and the ones incorporated with other different support additives such as zeolite L, SBA-15 and Al-SBA-15. The characterization results demonstrated that LS possessed the typical characteristics of mesoporous silica SBA-15 and microporous zeolite L. The textural properties of the composite material were dramatically improved and the results of acidity measurements indicated that LS exhibited a high acid amount and an appropriate Brönsted and Lewis acid distribution. The catalyst CoMo/LSA showed superior hydro-upgrading catalytic performances, i.e., excellent hydrodesulfurization (HDS), hydroisomerization, aromatization activities and a good preserving ability of the octane number, which can be attributed to the hierarchically porous structure and the properly acidic properties of LS. Thus, LS has potential application for clean gasoline upgrading.Graphical abstractMicro/mesoporous composite L-SBA-15(LS) was successfully synthesized using low-cost solid silica–alumina microspheres. The corresponding catalyst CoMo/LS-γ-Al2O3(CoMo/LSA) was introduced to the reaction process of FCC gasoline hydro-upgrading, and exhibited excellent hydrodesulfurization performance and a good preserving ability of octane number.

Pd nanoparticles were well dispersed on a new triptycene-based microporous polymer support by the gas bubbling-assisted membrane reduction (GBMR) method. The stability of Pd nanoparticles is improved by the porous support, and the materials show excellent performance for CO oxidation.

As a newly developed synthetic method, urothermal synthesis was employed to construct a series of photoluminescent lanthanide–organic frameworks based on a flexible ligand. Eight new lanthanide compounds, namely Ln2(obb)3(e-urea)(H2O) [Ln = Er (1), Yb (2), Ho (3); obb = 4,4′-oxybisbenzoic acid, e-urea = ethyleneurea], Ln2(obb)3(e-urea)(H2O)3 [Ln = Tb (4), Dy (5), Eu (6)], La2(obb)3(H2O)1.5(e-urea) (7) and [Sm2(obb)3(H2O)5]·(H2O) (8), have been synthesized under urothermal reactions and structurally characterized by single-crystal X-ray diffraction. Compounds 1, 2 and 3 are isostructural and possess three-dimensional structures with (3,3,4,5,5)-connected new topology, while compounds 4, 5 and 6 are almost identical in structure with the space group P21/n and display an unusual (4,4,5)-connected topology. Compound 7 is a unique two-dimensional structure with the centrosymmetric space group Pbca and possesses a (4,4,7,7)-connected new topology. Different from the above-mentioned seven frameworks (1–7), compound 8 features a three-dimensional framework with unprecedented (3,4,4,5,6)-connected new topology. In these compounds, the structural variations were rationalized by the effect of lanthanide contraction, the effect of e-urea as the structure-directing agent and the different coordination modes of the flexible obb ligand. The luminescent properties of compounds 4 and 6 have been studied in the solid state at room temperature, and both of them display metal-based luminescence.

Presented here is a new strategy for the synthesis of metallamacrocycles (MC[n]) with different ring-size and guest selectivity via integrating a flexible trinuclear metal unit and a bridging organic ligand, and further body-centered cubic packing of these MCs results in the formation of three microporous MOFs for potential application in gas storage.

A rare two-dimensional (2D) La(III) chiral hybrid organic–inorganic coordination polymer [La2(D-cam)2(CH3COO)2(DMA)4] (1 D-H2cam = D-camphoric acid; DMA = N,N-dimethylacetamide) based on paddle-wheel subunit has been solvothermally prepared and structurally characterized by single-crystal X-ray diffraction. Compound 1 exhibits a rare low-connected layered structure with sql topology, and further stacking of layers leads to a 3D supramolecular framework. The thermogravimetric behavior and chiral nature of 1 have been also investigated. The solid-state circular dichroism(CD) measurements with the Cotton effects at λmax = 280 nm apparently show that the bulk sample of 1 is homochiral.Presented here is a novel two-dimensional (2D) La(III) coordination polymer constructed from paddle-wheel subunits, which exhibits a rare layered structure with sql topology and homochiral environment.Highlights► A novel two-dimensional (2D) La(III) coordination polymer constructed from paddle-wheel subunits ► A rare layered structure with 4-connected sql topology ► The bulk sample of 1 possessing homochiral environment

We have investigated the mechanism of M(CO)5 (M = Fe, Ru, Os) catalyzed water gas shift reaction (WGSR) by using density functional theory and ab initio calculations. Our calculation results indicate that the whole reaction cycle consists of six steps: 1 → 2 → 3 → 4 → 5 → 6 → 2. In this stepwise mechanism the metals Fe, Ru, and Os behave generally in a similar way. However, crucial differences appear in steps 3 → 4 → 5 which involve dihydride M(H)2(CO)3COOH– (4′) and/or dihydrogen complex MH2(CO)3COOH– (4). The stability of the dihydrogen complexes becomes weaker down the iron group. The dihydrogen complex 4_Fe is only 11.1 kJ/mol less stable than its dihydride 4′_Fe at the B3LYP/II(f)++//B3LYP/II(f) level. Due to very low energy barrier it is very easy to realize the transform from 4_Fe to 4′_Fe and vice versa, and thus for Fe there is no substantial difference to differentiate 4 and 4′ for the reaction cycle. The most possible key intermediate 4′_Ru is 38.2 kJ/mol more stable than 4_Ru. However, the barrier for the conversion 3_Ru → 4′_Ru is 23.8 kJ/mol higher than that for 3_Ru → 4_Ru. Additionally, 4′_Ru has to go through 4_Ru to complete dehydrogenation 4′_Ru → 5_Ru. The concerted mechanism 4′_Ru → 6_Ru, in which the CO group attacks ruthenium while H2 dissociates, can be excluded. In contrast to Fe and Ru, the dihydrogen complex of Os is too unstable to exist at the level of theory. Moreover, we predict Fe and Ru species are more favorable than Os species for the WGSR, because the energy barriers for the 4 → 5 processes of Fe and Ru are only 38.9 and 16.2 kJ/mol, respectively, whereas 140.5 kJ/mol is calculated for the conversion 4′ → 5 of Os, which is significantly higher. In general, the calculations are in good agreement with available experimental data. We hope that our work will be beneficial to the development and design of the WGSR catalyst with high performance.

A series of catalysts of three-dimensionally ordered macroporous (3DOM) Ce0.8Zr0.2O2-supported gold nanoparticles with controllable sizes were successfully synthesized by the facile method of gas bubbling-assisted membrane reduction (GBMR). All the catalysts possess well-defined 3DOM structures, which consist of interconnected networks of spherical voids, and the Au nanoparticles are well dispersed and supported on the inner wall of the uniform macropore. The relationship between Au particle sizes and the ability to adsorb and activate oxygen was characterized by means of O2-TPD and XPS. The results show that the active oxygen species (O−) and gold ions with oxidation state of Au+ are essential for soot oxidation reaction. 3DOM Au0.04/Ce0.8Zr0.2O2catalyst with Au particle size of 2–3 nm has the strong capability of adsorption and activation of oxygen. Thus, it exhibits super-catalytic activity for diesel soot oxidation, especially at low temperature. The reaction pathways of catalytic soot oxidation in the presence or absence of NO can be outlined as follows: at low temperature (<250 °C), the catalytic performance of supported Au catalyst is dependent on the Au particle sizes. At relatively high temperature (>250 °C), the catalytic activity is strongly related to the NO gas, because NO2 derived from NO oxidation is used as intermediate to catalyze soot oxidation.

Nanocomposite K–Co–CeO2 catalysts were synthesized by the controllable micropore-diffused co-reaction method. Due to the size-match nanometre effect between CeO2 support and active components and formation of NO2, these cheap nanocomposite catalysts exhibit super catalytic performances which are as good as a supported Pt catalyst under loose contact conditions for soot combustion.

The microstructure with open, interconnected macropores of 3DOM Ce1−xZrxO2, successfully prepared using PMMA colloidal crystal as template and cerium nitrate and zirconium oxide chloride as raw materials, facilitates the contact between soot and catalysts and results in much higher catalytic activity for diesel soot combustion than the corresponding disordered macroporous catalysts.

Polymeric carbon nitride is reported to be a promising candidate in environmental catalysis for NO decomposition carried out at elevated temperature. Theoretical calculations support a mechanism where Lewis basic site of g-C3N4 can donate electrons to the adsorbed NO, decreasing the bond order of N–O thus facilitating the reaction.

A series of HZSM-5 zeolites modified by different amounts of phosphorus (P/HZSM-5) were prepared, and their catalytic performances for the coupling reaction of methanol and C4 hydrocarbons to light olefins were investigated. The results indicated that P/HZSM-5 is a highly efficient catalyst for the transformation of methanol and 1-butene to propene with low-energy consumption. At the temperature of 550 °C, the maximum yield of propene was achieved at 44.0%, which was 7.4 and 4.5% higher than those on 1-butene catalytic cracking and methanol to olefins (MTO), respectively. X-ray photoelectron spectroscopy (XPS) characterization on the catalyst showed that P bonds to the HZSM-5 zeolite framework through oxygen. The enhanced coupling performances can be correlated to the combined effects of matching of the co-feedings and the suitability of the P/HZSM-5 catalyst.

Nanometric CeO2-supported perovskite-liked La1.7Rb0.3CuO4 oxide catalysts with different loading amounts were obtained by the method of ultrasonic-assisted incipient-wetness impregnation. All of the catalysts were calcined at 700 °C for 6 h and characterized by means of BET, XRD, IR, and UV−vis−NIR. These materials were tested for the simultaneous removal of NOx and soot in the temperature range from 200 to 600 °C. As compared to nanometric CeO2 support particles (nmCeO2) or pure La1.7Rb0.3CuO4 perovskite-liked catalyst, the catalytic activities of all of the supported catalysts were remarkably enhanced. The temperatures for soot combustion of Tm decreased and the productivities of N2 increased, and the activities of the catalysts increased with the perovskite-liked oxide loading amount. On the basis of in situ DRIFT characterization, NO oxidation, and O2-TPD results, a reaction mechanism for the simultaneous removal of NOx and soot over (La1.7Rb0.3CuO4)x/nmCeO2 was proposed.

Two different ways, including an in situ synthetic method and a mechanical mixing method, were used to combine zeolite USL (ultra stable L) with alumina for preparation of a new composite support material of hydrotreating catalyst. The physicochemical properties of samples were characterized by means of XRD, N2 physisorption, SEM, FT-IR, 27Al MAS NMR, NH3-TPD, H2-TPR, and UV−vis DRS. Composite supports containing different contents of zeolite USL and Al2O3 were prepared by in situ synthetic method based on a modified pH-swing method, which showed a higher specific surface area, pore volume, as well as average pore diameter compared with the supports prepared via a mechanical mixing method. Corresponding NiW/γ-Al2O3−USL series catalysts were obtained by the incipient-wetness impregnation method, and the activities of these catalysts for FCC diesel hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) were evaluated in a high-pressure microreactor system. The assessment results indicated that the catalyst with 10 m% USL in the support prepared by the in situ method showed the highest HDS and HDN conversions, which reached a maximum of 99.3% and 94.1% for HDS and HDN, respectively. In addition, the swing pH method plays an important role in preparation of the Al2O3 support, and NiW/γ-Al2O3(P) (prepared by the swing pH method) catalyst also gave better performance for the HDS and HDN of diesel oil. These activities were much higher than those over a kind of industrial catalyst of RN10 and were also better than the corresponding catalyst in which the support was obtained by the mechanical mixing method.

The physicochemical properties and combustion characteristics of model soot (i.e., Printex U) and diesel particulates with different origins were compared. Their elemental composition and structures were determined using several kinds of techniques including element analysis, infrared spectroscopy (IR), X-ray fluorescence spectroscopy (XRF), and X-ray photoelectron spectroscopy (XPS), and their different reactivities were measured by a number of temperature-programmed oxidation (TPO) experiments. It was found that the Brunauer−Emmett−Teller (BET) surface area of the particulates increased with the increase of the amount of adsorbed hydrocarbons. The main element components of model carbon were basically consistent with those of the practical diesel particulates, including C, H, O, etc. However, their element contents and surface properties were very different. The major ingredient of Printex U was carbon, and its content reached 92%; however, the carbon content of diesel particulates was about 65−74%, and the contents of O, H, and N in the diesel particulates were about 3−10 times as much as those of Printex U. TPO results showed that the diesel particulates could be more easily removed than Printex U by the combustion method, and the combustion temperatures for both Printex U and diesel particulates could be lowered when catalysts were present. Printex U is very well-suited as a kind of model soot for the study on the combustion performances of the soot fraction of diesel particulates.

A novel micro- and mesoporous composite molecular sieve (denoted as LMC) was synthesized by using the nanocrystal clusters of zeolite L as the precursor and a cation surfactant cetyltrimethylammonium bromide (CTAB) as the template. The physicochemical properties of samples were characterized by means of X-ray diffraction (XRD), nitrogen-adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared spectroscopy (FTIR), and Fourier transform infrared spectroscopy of pyridine adsorption (Py-FTIR). The results showed that composite molecular sieve LMC was synthesized by the self-assembly of zeolite L nanocrystal clusters under the template effect of CTAB. In addition, surface area, pore volume, and pore size of LMC significantly increased in comparison to those of conventional microporous zeolite L. The results measured by Py-FTIR showed that LMC had an appropriate acid amount and acid distribution. For evaluation of fluid catalytic cracking (FCC) gasoline hydrodesulfurization (HDS), the catalyst that introduced material LMC exhibited the excellent performances of desulfurization, isomerization, aromatization, olefin retention, and preserving the research octane number (RON) value compared to the catalyst that introduced ordinary microporous zeolite L or mesoporous Al-MCM-41 and used bare alumina as the support. The excellent catalytic performances of the catalyst should be attributed to the appropriate acidity distribution and open pore structure of material LMC.

A series of fluorinated HZSM-5 zeolites (F/HZSM-5) were prepared by immersing the zeolites with different concentrations of NH4F solution, and their performances for the catalytic cracking of naphtha to produce light olefins were investigated. The results indicated that F-modified HZSM-5 zeolites are effective catalysts for the cracking of naphtha to light olefins. At the temperature of 600 °C, the yields of propene and ethene were achieved at 36.4 and 20.2%, which were 7.3 and 4.3% higher than those over parent HZSM-5 zeolite, respectively. The physicochemical features of F/HZSM-5 catalysts were characterized by means of X-ray diffraction (XRD), Brunauer−Emmett−Teller (BET), temperature-programmed desorption of ammonia (NH3-TPD), Fourier transform infrared (FTIR) spectra of adsorbed pyridine, etc. The results indicated that fluorine (F) modification not only regulates the pore characteristics of the HZSM-5 zeolites but also modulates the amount of acid sites, especially the amount of Brönsted (B) acid. Consequently, F modification with suitable content was favorable for increasing the conversion of naphtha and enhancing the selectivity to light olefins.

Al2O3−TiO2 and Al2O3−TiO2−SiO2 (denoted as AT and ATS) composite oxides were synthesized by the sol−gel method, which were used as supports for bimetallic Pt−Pd catalysts. The typical physicochemical properties of the catalyst samples were characterized by means of N2 adsorption, UV−vis diffuse reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The diesel hydrodearomatization (HDA) and hydrodesulfurization (HDS) activities of the catalysts were evaluated using a microreactor system. In comparison to the Pt−Pd/AT catalysts, all of the Pt−Pd/ATS catalysts showed much higher HDA activities. A 100 h test showed that the Pt−Pd/ATS catalyst had a high equilibrium HDA activity, with 432 ppm sulfur diesel. The enhanced HDA activity and sulfur tolerance of Pt−Pd/ATS were likely attributed to the incorporations of Ti and Si into Al2O3, which optimized the interaction between the catalyst support and active metals.

Single-component sorption/diffusion of methane, ethane, propane, n-butane, isobutane, cyclohexane, and toluene in ZSM-5 and USY zeolites has been measured by a chromatographic method in the temperature range of 373−598 K. It is shown that the adsorption equilibrium constants decreased with the increase of the temperature, while it increased with the increase of the atomic number of carbon in the adsorbate molecule. The adsorption energies increased with the increase of molecular weights of the adsorbate molecules. The adsorption energy follows the order: methane < ethane < propane < n-butane < cyclohexane < toluene. The diffusivities in the micropore were larger at higher temperatures. The diffusivities in the micropore increased with the decrease of critical sizes of adsorbate molecules, for example, ethane > propane > n-butane > cyclohexane > toluene. The diffusion coefficients are found to be influenced by the critical molecular size, electronic effect, and configuration of sorbate molecules. In comparison to the diffusion data in ZSM-5 and USY zeolites, it is confirmed that the zeolite channel also plays a vital controlling/deciding role in the penetration and diffusion.

A series of hydrodesulfurization (HDS) catalysts of Ni−W supported on γ-Al2O3-MB (denoted as AMB) composites with various amounts of H-type β zeolite (denoted as MB) synthesized from kaolin were prepared. The samples were characterized by means of N2 physisorption, XRD, SEM, TPR, HRTEM, XPS, and FT-IR spectroscopy of pyridine adsorption. The characterization results showed that, compared with NiW/Al2O3, the addition of MB reduced the interaction between W and the support. The addition of MB made the WS2 slabs grow larger and the stacking degree become higher. The addition of MB also enhanced the overall acidity of AMB supports and led to an increase in the ratio of Brönsted acid of the NiW catalysts. W exhibited higher sulfidation extent in MB-containing NiW/AMB3 catalyst than that in NiW/Al2O3. The fluidized catalytic cracking (FCC) diesel HDS activity changed with the addition of varying amounts of MB on NiW/AMBi catalysts. The optimal MB content was 32 wt % in composite AMB support. A higher deep HDS efficiency was achieved on NiW/AMB3 than that of traditional NiW/Al2O3. Higher HDS activity of NiW/AMB3 was attributed to the appropriate ratio of Brönsted acid to Lewis acid and/or the enhanced hydrogenation activity. For NiW/AMB3 catalyst, the effect of operation conditions on the degree of HDS of FCC diesel was investigated. The ultradeep desulfurization of FCC diesel oil, in which the sulfur content is below 10 ppm, could be obtained under the optimal operation conditions: T = 360 °C, P = 5 MPa, LHSV = 1 h−1, and H2/oil = 600.

The highly active (La0.9K0.1CoO3)x/nmCeO2 catalysts consisting of comparably sized La0.9K0.1CoO3 active component and CeO2 support nanoparticle were studied on the catalytic combustion of soot by temperature-programmed oxidation (TPO) technique. The properties of oxygen species and the redox performances of catalysts were investigated by the method of O2-TPD and H2-TPR. During TPO process, all supported oxide catalysts showed lower Tm than the corresponding nanometer CeO2 support or pure La0.9K0.1CoO3 perovskite. The best catalytic activity was obtained over (La0.9K0.1CoO3)20/nmCeO2 catalyst (Tm= 354 °C), and its catalytic activity for the combustion of soot is as good as supported Pt catalysts. During the catalytic combustion of soot, the surface α oxygen species should play an important role. The formation of surface oxygen-containing complexes (SOC) may be one of the key intermediate species according to the results of in situ DRIFT, and NO2 released by surface nitrate species remarkably promote the soot oxidation.

A systematic and comparative study of the decomposition procedures of unsupported and Al2O3-supported Co(NO3)2·6H2O, as well as the reduction procedures of bulk Co3O4 and Al2O3-supported Co3O4 was carried out. A series of decomposition products of bulk and Al2O3-supported Co(NO3)2·6H2O, and bulk cobalt oxides (Co3O4 and CoOOH) and Al2O3-supported Co3O4 (Co/Al2O3 catalysts) were prepared by the methods of calcination, deposition-precipitation, and incipient-wetness impregnation. The bulk and supported samples were characterized by different techniques, including XRD, UV−vis−NIR, TG-DTA, gas analyzer, and H2-TPR. The results show that the CoO species first appears in the calcination process of bulk Co(NO3)2·6H2O decomposition, and then CoO is oxidized to form Co3O4. CoO-Al2O3 composite oxide first appears in the calcination process of Al2O3-supported Co(NO3)2·6H2O decomposition. CoO disperses on the surface of Al2O3 support at first and then forms a multilayer with the decomposition of Co(NO3)2. Finally, CoO-Al2O3 composite oxide, which is very difficult to be reduced to metal Co, was oxidized to Co3O4. Particularly, it is thoroughly analyzed that the attribution of each reduction peak in the H2-TPR profiles of a series of Al2O3-supported Co-based catalyst. Moreover, it is a first semiquantitative study on the formation process of CoO in the course of calcination of bulk Co(NO3)2·6H2O and Al2O3-supported Co(NO3)2·6H2O, by introducing parameter α. In addition, the reduction mechanisms of bulk Co3O4 and Al2O3-supported Co3O4 were studied in detail, too. The reduction performance of Al2O3-supported Co3O4 is different from that of the bulk Co3O4, because of the strong interaction between Co3O4 and Al2O3 support. The activation energies for the two transformations from bulk Co3O4 to CoO and from CoO to Co are 80 and 53 kJ/mol, respectively. However, the activation energies for the two transformations from Al2O3-supported Co3O4 to CoO-Al2O3 and from CoO-Al2O3 to Co are 90 and 95 kJ/mol, respectively. So the H2-TPR profile of Al2O3-supported Co3O4 exhibits two apparent peaks, whereas the H2-TPR profile of bulk Co3O4 exhibits the incorporated trend of two peaks.

UV-Raman spectroscopy was used to study the molecular structures of TiO2 or ZrO2-supported vanadium oxide catalysts. The real time reaction status of soot combustion over these catalysts was detected by in-situ UV-Raman spectroscopy. The results indicate that TiO2 undergoes a crystalline phase transformation from anatase to rutile phase with the increasing of reaction temperature. However, no obvious phase transformation process is observed for ZrO2 support. The structures of supported vanadium oxides also depend on the V loading. The vanadium oxide species supported on TiO2 or ZrO2 attain monolayer saturation when V loading is equal to 4 (4 is the number of V atoms per 100 support metal ions). Interestingly, this loading ratio (V4/TiO2 and V4/ZrO2) gave the best catalytic activities for soot combustion reaction on both supports (TiO2 and ZrO2). The formation of surface oxygen complexes (SOC) is verified by in-situ UV Raman spectroscopy and the SOC mainly exist as carboxyl groups during soot combustion. The presence of NO in the reaction gas stream can promote the production of SOC.

The nanometric La1−xKxCoO3 (x = 0–0.30) perovskite-type oxides were prepared by a citric acid-ligated method. The catalysts were characterized by means of XRD, IR, BET, XPS and SEM. The catalytic activity for the simultaneous removal of soot and nitrogen oxides was evaluated by a technique of the temperature-programmed oxidation reaction. In the LaCoO3 catalyst, the partial substitution of La3+ at A-site by alkali metal K+ enhanced the catalytic activity for the oxidation of soot particle and reduction of NOx. The La0.70K0.30CoO3 oxides are good candidate catalysts for the simultaneous removal of soot particle and NOx. The combustion temperatures for soot particles over the La0.70K0.30CoO3 catalyst are in the range from 289 to 461 °C, the selectivity of CO2 is 98.4% and the conversion of NO to N2 is 34.6% under loose contact conditions. The possible reasons that can lead to the activity enhancement for the K-substitution samples compared to the unsubstituted sample (LaCoO3) were given. The particle size has a large effect on its catalytic performance for the simultaneous removal of diesel soot and nitrogen oxides.

A kind of metakaolin materials with big pores was prepared from natural kaolin clays. The prepared metakaolin was introduced into alumina as composite support for hydrotreating application. A series of nickel–tungsten catalysts (NiO 2.9 wt%, WO3 27.2 wt%) supported on alumina-metakaolin, alumina-titania and bare alumina also were prepared. Electron microprobe analysis including SEM and TEM, BET and temperature programmed desorption of NH3 were used for the samples characterization. Their hydrodesulfurization (HDS) activity for diesel were evaluated and compared. The results showed that NiW/alumina-metakaolin had excellent HDS activity and alumina-metakaolin support could be a good candidate support for hydrotreating catalysts.

As a novel catalyst system for the selective oxidation of low alkanes, mesoporous SBA-15-supported potassium catalysts were firstly employed for the selective oxidation of propane to oxygenates by using molecular oxygen as oxidant. It was found, compared with bare mesoporous SBA-15, that the selectivities to the oxygenates including formaldehyde, acetaldehyde, acrolein and acetone were remarkably enhanced over Kx/SBA-15(K:Si = x:100, mol) catalysts, and the main products were acrolein and acetone. At 500 °C, the yield of the oxygenates can reach 464% over K3.0/SBA-15, which is the highest value over SBA-15–supported potassium catalysts. The catalysts were characterized by XRD and BET techniques. The results demonstrated that the catalytic performance was strongly dependent on the potassium content of the catalysts. Furthermore, the highly dispersed potassium on the catalyst surface was shown to be important to orientate the reaction toward the production of oxygenates. The obtained results showed that mesoporous structure, uniform pore sizes and appropriate pore surface area were favorable for the selective oxidation of propane. The samples with moderate amount of potassium promoted the selectivity to the oxygenates.

Several systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with different ratios of SiO2/Al2O3 (25,38,50,80, and 150) were prepared and they were characterized by means of X-ray diffraction (XRD), UV–Vis, NH3-TPD and BET techniques. The results indicated that, compared with uncalcined HZSM-5 zeolites, the total acid amounts, acidic site density and acidic strength of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts obviously decreased, while those of weak acid amounts obviously enhanced with the decrease of SiO2/Al2O3 molar ratio. When the ratio of SiO2/Al2O3 is less than 50, the three systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with same ratio of SiO2/Al2O3 gave similar and high isobutane conversions. However, when the ratio of SiO2/Al2O3 was equal to or greater than 80, these three systems of catalysts possessed different altering tendencies of isobutane conversions, thus their isobutene conversions were different. High yields of light olefins were obtained over the FeHZSM-5 and CrHZSM-5 zeolite catalysts with high ratio of SiO2/Al2O3 (≥80). The ratio of SiO2/Al2O3 has large effects on the surface area, and acidic characteristics of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolites catalysts, and thus further affect their catalytic performances for isobutane cracking. That is the nature of SiO2/Al2O3 ratio effect on the catalytic performances.

SBA-15 supported Mo catalysts (Moy/SBA-15) were prepared by an ultrasonic assisted incipient-wetness impregnation method. The physical and chemical properties of the catalysts were characterized by means of N2-adsorption-desorption, XRD, TEM, UV-Vis, Raman, XANES and H2-TPR. The results showed that a trace amount of MoO3 was produced on high Mo content samples. Turn-over frequency (TOF) and product selectivity are dependent on the molybdenum content. Both Mo0.75/SBA-15 and Mo1.75/SBA-15 catalysts give the higher catalytic activity and the selectivity to the total aldehydes for the selective oxidation of C2H6. At the reaction temperature of 625 °C, the maximum yield of aldehydes reached 4.2% over Mo0.75/SBA-15 catalyst. The improvement of the activity and selectivity was related with the state of MoOx species.Among the series Mox/SBA-15 catalysts, the low Mo loading is beneficial to the formation of isolated tetra-coordination molybdenum species, these species are beneficial to the formation of total aldehydes in the selective oxidation of C2H6.Download full-size image

Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of α-NiMoO4 and β-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoO4 was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogenation of propane in comparison with bulk NiMoO4.The vacuum nanocasting method was employed to enhance the capillary force. Ordered mesoporous NiMoO4 material was successfully synthesized. Ordered mesoporous NiMoO4 shows better catalytic performance for ODHP than bulk NiMoO4.Download full-size image

Three-dimensionally ordered macroporous (3DOM) Ce1−xZrxO2-supported gold nanoparticle catalysts were successfully synthesized by the gas bubbling-assisted membrane reduction (GBMR) method. Au nanoparticles with similar sizes are well dispersed and supported on the inner walls of uniform macropores. The active oxygen species (O2-, O−) over 3DOM Au/Ce1−xZrxO2 catalysts are derived from the two approaches: one is direct activation of oxygen on the surface of gold nanoparticles and the other is derived from strong metal–support interaction in which Ce-based supports serve as a reservoir for oxygen in the oxidation reaction. 3DOM Au/Ce1−xZrxO2 catalysts exhibited good catalytic performance for soot combustion, which is strongly related to the role of supports including the structures, the Ce/Zr ratios and the active oxygen supply pathways. The reaction pathways of soot combustion can be classified by two regions. At the low temperature, the soot particles are direct oxidized by active oxygen species migrated from the surface of supported Au catalysts. At the relatively high temperature, the catalytic activity for soot combustion is strongly related to intermediate reactant of NO2 derived from NO oxidation.Graphical abstractThe catalytic activities of 3DOM Au/Ce1−xZrxO2 materials for soot oxidation are strongly related to the metal (Au)-supports (Ce) interaction. At low temperature, the soot particles are direct oxidized by active oxygen species migrated from the surface of supported Au catalysts. At high temperatures, the combined effects of active oxygen species and NO2 enhance the rate of soot combustion.Download high-res image (162KB)Download full-size imageHighlights► 3DOM Au/Ce1−xZrxO2 catalysts with the similar size of Au particle were synthesized by GBMR method. ► The catalysts exhibited high catalytic activities (T10 and SCO2) for soot combustion. ► The catalytic activity depended on the amount of active oxygen species. ► The soot combustion process over 3DOM catalyst was observed by “in situ” TEM images. ► The interaction between the Au nanoparticle and supports were systematically investigated.

V-doped SBA-16 catalysts (V-SBA-16) with 3D nanocage mesopores have been successfully synthesized by a modified one-pot method under weak acid condition. The obtained materials were characterized by means of small angle XRD, N2 adsorption–desorption, TEM, UV–Vis and UV-Raman spectroscopy. These characterization results indicated that well-order mesoporous structures were maintained even at higher vanadium loadings and high concentration of VOx species were incorporated into the framework of SBA-16 support. The catalytic performances of V-SBA-16, V/SBA-16 and V/SiO2 catalysts were comparatively investigated for the oxidative dehydrogenation of ethane to ethylene. The highest selectivity to ethylene of 63.3% and ethylene yield of 25.6% were obtained over 1.0V-SBA-16 catalyst. The superior catalytic performance of V-SBA-16 catalysts could be attributed to the presence of isolated framework VOx species, the unique structure of SBA-16 support and weak acidity. Moreover, V/SiO2 catalyst exhibited relatively poor catalytic activity duo to the formation of V2O5 nanoparticles on the surface of SiO2 support and the low dispersion of VOx species. These results indicated that the catalytic performances of the studied catalysts were strongly dependent on the vanadium loading, the nature and neighboring environment of VOx species and the structure of support.Download high-res image (217KB)Download full-size imageThe V-SBA-16 catalyst exhibited a superior catalytic performance of ODHE compared with V/SBA-16 and V/SiO2 catalysts. The improvement of catalytic activity for V-SBA-16 catalyst was ascribed to the incorporated V into the framework of SBA-16.

Mo-incorporated SBA-15 (Mo-SBA-15) catalysts with different Mo:Si molar ratios were synthesized by a direct hydrothermal method, and SBA-15-supported Mo catalysts (Mo/SBA-15 and K-Mo/SBA-15) were prepared by an incipient-wetness impregnation method. The structures of the catalysts were characterized by means of N2 adsorption–desorption, XRD, TEM, FT-IR, and UV-Raman, and their catalytic performance for the oxidation of ethane was tested. Turnover frequency and product selectivity are strongly dependent on the molybdenum content and catalyst preparation method. Furthermore, the addition of potassium promotes the formation of isolated tetra-coordination molybdenum species and potassium molybdate. The K/Mo-SBA-15 catalysts possess much higher catalytic selectivity to acetaldehyde in the selective oxidation of ethane than the supported molybdenum catalysts (Mo/SBA-15 or K-Mo/SBA-15). The highest selectivity of CH3CHO + C2H4 68.3% is obtained over the K/Mo-SBA-15 catalyst. Analysis of kinetic results supports the conclusion that ethane oxidation is the first-order reaction and ethane activation may be the rate-determining step for the oxidation of ethane. Ethylene is a possible intermediate for acetaldehyde formation.Potassium-modified K/Mo-SBA-15 catalysts give supercatalytic performance for the selective oxidation of ethane to acetaldehyde and ethylene. The maximum yields of acetaldehyde and ethylene can reach 10.2% and 19.9%, respectively.Download high-res image (30KB)Download full-size image

•A novel Mo-incorporated KIT-6 catalyst was synthesized by a one-pot co-assembly method.•Mo-KIT-6 gave a high concentration of framework-isolated MoOx and anchored them firmly.•In situ Raman results showed that Mo-KIT-6 has a good redox ability to regenerate the reduced MoOx.•In situ Raman results showed that Mo-KIT-6 has strong carbon deposition resistance and stability.•The maximal yield of acrolein reached 25.9% over 0.25 K/0.1Mo-KIT-6 catalyst.A series of novel molybdenum-incorporated mesoporous silica catalysts (Mo-KIT-6) were successfully synthesized by a one-pot co-assembly method. For comparison, corresponding mesoporous KIT-6-supported molybdena catalysts (Mo/KIT-6) were also prepared by the impregnation method. For Mo-KIT-6 catalysts, the molybdenum was substituted into the framework of the KIT-6 support, which contributed to obtaining high concentrations of highly dispersed and isolated active sites and to anchoring the active sites firmly. We determined the identity of the active sites of Mo-KIT-6 catalysts as Mo oxide units with more anchoring MoOSi bonds than in the corresponding Mo/KIT-6 at elevated temperature. The Mo-KIT-6 catalysts possess appropriate redox properties, high stability, and a strong ability to resist carbonaceous species formation, which was confirmed by in situ UV Raman results. Furthermore, the addition of K to Mo-KIT-6 catalyst further promoted the formation of acrolein, and the maximum single-pass yield of acrolein reached 25.9%.Download high-res image (168KB)Download full-size image

•A novel composite of ZSM-5/KIT-6 (ZK-W) was synthesized by enwrapping method.•NiMo/ZK-W catalyst exhibited superior activity in the HDS of 4,6-DMDBT.•3,6-DMDBT and 3,7-DMDBT were detected simultaneously in HDS of 4,6-DMDBT.•HDS of 4,6-DMDBT occurs mainly through isomerization route over NiMo/ZK-W.•A reaction network for the HDS of 4,6-DMDBT was proposed over NiMo/ZK-W.A novel composite material ZSM-5/KIT-6 (ZK-W) was synthesized by enwrapping nano-sized ZSM-5 zeolite crystals with mesoporous KIT-6 silica. This composite was used as catalyst support for NiMo sulfide in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The NiMo/ZK-W catalyst showed the highest HDS activity and its 4,6-DMDBT conversion was about double that of a conventional NiMo/Al2O3 catalyst at 320 °C, 4.0 MPa, and LHSV of 150 h−1 and on the basis of sulfur. The superior catalytic performance of NiMo/ZK-W is related to the synergistic effect of the excellent diffusion through the hierarchical porous structure and the suitable Brønsted acid sites. 3,6-DMDBT and 3,7-DMDBT, two isomers of 4,6-DMDBT, were identified simultaneously for the first time in the HDS products of 4,6-DMDBT over the NiMo/ZK-W catalyst. The NiMo/ZK-W catalyst exhibited a superior isomerization ability, and 4,4′-dimethylbiphenyl was the main product, indicating that the isomerization pathway is the main reaction route. A new reaction network of 4,6-DMDBT HDS over NiMo/ZK-W catalyst was proposed.Download high-res image (138KB)Download full-size image

•One-step synthesis of supported Au@Pt NPs is realized by GBMR method.•Amounts of active oxygen species are increased by synergistic effect of Au core and Pt shell.•The contact between soot particles and catalysts is improved by 3DOM support.•3DOM Au@Pt/CZO catalysts exhibit super catalytic performance for soot combustion.•Pt shell can improve the stability of supported Au(core)-based catalysts.Supported Au@Pt core–shell nanoparticles (NPs) were successfully synthesized on three-dimensionally ordered macroporous (3DOM) oxides by a one-step gas bubbling-assisted membrane reduction (GBMR) method. The Au@Pt core–shell NPs were highly dispersed on the pore wall of oxides and the Pt shell was obtained by direct epitaxial overgrowth on the surface of the Au core. The multifunctional nanocatalysts were used for diesel soot oxidation. 3DOM structure facilitates the contact between soot particles and catalysts, and the synergetic effect of the Au core and Pt shell significantly increases the surface concentration of active O2− species. 3DOM Ce0.8Zr0.2O2-supported Au@Pt core–shell NP catalyst is one of the best catalysts reported so far for soot oxidation under “loose” contact between soot and catalyst. The stability of the Au-based catalysts for soot oxidation is also improved due to the formation of an Au@Pt core–shell structure.Graphical abstractDownload high-res image (85KB)Download full-size image

Micro-mesoporous composite material Beta-KIT-6 (BK) with the BEA microporous structure and cubic Ia3d mesoporous structure was synthesized and used as catalyst support for the hydrodesulfurization of dibenzothiophene. The composite material possessed both KIT-6 and Beta structures. NiMo/BK had similar acidity as NiMo/Beta and possessed more acid sites and stronger acidity than NiMo/KIT-6 and NiMo/SBA-15. NiMo/BK showed the highest dibenzothiophene hydrodesulfurization activity among all the catalysts that were studied, and the dibenzothiophene conversion on NiMo/BK was about 2–3 times that of NiMo/Al2O3. The acidity of NiMo/BK enhanced the activity of the direct desulfurization pathway more significantly than that of the hydrogenation pathway. Cyclohexen-1-yl-benzene was detected as intermediate of the hydrogenation pathway. NiMo/KIT-6 exhibited higher activity than NiMo/SBA-15 due to the superior mass transfer ability of the cubic Ia3d mesoporous structure.Micro-mesoporous composite material of Beta-KIT-6 (BK) was successfully synthesized. Superior mass transfer property combined with suitable acidity make Beta-KIT-6-supported NiMo an excellent catalyst for the hydrodesulfurization of dibenzothiophene.Download high-res image (119KB)Download full-size image

The typical physico-chemical properties and their hydrodesulfurization activities of NiMo/TiO2-Al2O3 series catalysts with different TiO2 loadings were studied. The catalysts were evaluated with a blend of two kinds of commercially available diesels in a micro-reactor unit. Many techniques including N2-adsorption, UV–vis DRS, XRD, FT-Raman, TPR, pyridine FT-IR and DRIFT were used to characterize the surface and structural properties of TiO2-Al2O3 binary oxide supports and the NiMo/TiO2-Al2O3 catalysts. The samples prepared by sol–gel method possessed large specific surface areas, pore volumes and large average pore sizes that were suitable for the high dispersion of nickel and molybdenum active components. UV–vis DRS, XRD and FT-Raman results indicated that the presence of anatase TiO2 species facilitated the formation of coordinatively unsaturated sites (CUS) or sulfur vacancies, and also promoted high dispersion of Mo active phase on the catalyst surfaces. DRIFT spectra of NO adsorbed on the pure MoS2 and the catalysts with TiO2 loadings of 15 and 30% showed that NiMo/TiO2-Al2O3 catalysts possessed more CUS than that of pure MoS2. HDS efficiencies and the above characterization results confirmed that the incorporation of TiO2 into Al2O3 could adjust the interaction between support and active metals, enhanced the reducibility of molybdenum and thus resulted in the high activity of HDS reaction.

TiO2-Al2O3 binary oxide supports were obtained by sol–gel methods from Tetra-n-butyl-titanate and pseudoboehmite/aluminium chloride resources. The typical physico-chemical properties of NiW/TiO2-Al2O3 catalysts with different TiO2 loadings and their supports were characterized by means of BET, XRD and UV–vis DRS, etc. The BET results indicated that the specific surface areas of NiW/TiO2-Al2O3 catalysts were as higher as that over pure γ-Al2O3 support, and the pore diameters were also large. The XRD and UV–vis DRS analyzing results showed that the Ti-containing supported catalysts existed as anatase TiO2 species and the incorporation of TiO2 could adjust the interaction between support and active metal, and impelled the higher reducibility of tungsten. The hydrodesulphurization (HDS) performance of the series catalysts were evaluated with diesel feedstock in a micro-reactor unit, and the HDS results showed that NiW/TiO2-Al2O3 catalysts exhibited higher activities of ultra deep hydrodesulphurization of diesel oil than that of NiW/Al2O3 catalyst. The optimal TiO2 content of NiW/TiO2-Al2O3 catalysts was about 15 m%, and the corresponding HDS efficiency could reach to 100%. The sulphur contents of diesel products over NiW/TiO2-Al2O3 (from pseudoboehmite/AlCl3) catalysts with suitable TiO2 content could be less than 15 ppmw, which met the sulphur regulation of Euro IV specification of ultra clean diesel fuel.

Micro-mesoporous composite material Beta-SBA-15 (BS) with the Beta structure and SBA-15 mesoporous structure was synthesized and used as catalyst support for hydrodesulfurization (HDS) of dibenzothiophene (DBT). The supports and catalysts were characterized by various techniques including XRD, nitrogen adsorption, SEM, TEM, 27Al MAS NMR, and Pyridine-FTIR. The characterization results demonstrated that NiMo/BS had similar acidity to NiMo/Beta, and possessed more acid sites and stronger acidity than NiMo/SBA-15 and NiMo/Al2O3. Activity evaluation results showed that NiMo/BS exhibited the highest DBT HDS activity among all the catalysts that were studied, and the DBT conversion on NiMo/BS was about 1.6 times as much as that on NiMo/Al2O3 at weight time of 0.75 g min mol−1. The better catalytic performance of NiMo/BS was attributed to the superiorities of the pore structure and large amounts of acid sites of micro-mesoporous BS.Graphical abstractThe synthesized material (Beta/SBA-15) possessed both the SBA-15 mesostructure and the BEA microporous structure. NiMo/BS catalysts exhibited high catalytic activity for the HDS of DBT.Download high-res image (286KB)Download full-size imageHighlights► Beta-SBA-15 material possesses both the SBA-15 mesopores and the BEA micropores was synthesized. ► Beta-SBA-15-supported NiMo catalysts exhibited super catalytic performance for the HDS of DBT. ► The influence of acidic of Beta-SBA-15-supported catalyst on the DBT HDS reaction was discussed.

The nmCeO2 and Ce0.8M0.2O2 (M = Sm, Zr, V) nanoparticles were prepared by the method of microwave-assisted heating decomposition. Their catalytic performances for diesel soot oxidation were investigated with temperature-programmed oxidation reaction (TPO). Spectroscopic techniques (XRD, Raman, UV-Vis DRS and FT-IR) were utilized to characterize the structures of nmCeO2 and Ce0.8M0.2O2 catalysts. The results show that the structures of the catalysts depend on the different doped ions. Ce0.8Sm0.2O2 and Ce0.8Zr0.2O2 still preserved a face-centered cubic fluorite structure of CeO2. However, CeVO4 crystallite was formed as V doping (Ce0.8V0.2O2). Nanometer CeO2, Ce0.8Sm0.2O2 and Ce0.8Zr0.2O2 exhibited higher catalytic activity than conventional CeO2 and Ce0.8V0.2O2 for soot combustion due to the nanometer effect and the good contact between the catalyst and soot. For soot oxidation, nmCeO2 is mainly active components. However, the doping of Sm or Zr could remarkably improve the thermal stability of nmCeO2, and the doping of Sm or V could enhance the ability to resist SO2 poison of catalysts.Graphical abstractThe catalytic combustion of soot over Ce-based nanoparticles was a gas–solid–solid three-phase complex reaction. Different doping ions and reaction gas remarkably affect the catalytic performances of materials.Download high-res image (178KB)Download full-size imageHighlights► Ce-based nanoparticles were synthesized by means of microwave-assisted heating decomposition. ► The influence of NOx and SO2 on catalytic performances was investigated by the in situ DRIFT method. ► The redox and catalytic property of CeO2 is strongly influenced by doping different valent ions.

To be used as the unique sources of silica and alumina, kaolin clay was pretreated by different kinds of acids including H2SO4, HCl and H3PO4. Through evaluating the synthesis factors of the kaolin clay pretreatment and the crystallization of beta zeolite systematically, the optimal conditions were obtained, i.e., using HCl concentrations of 8.2 mol/L to process kaolin clay at 96 °C for 3 h, and the optimal H2O/SiO2 of 3–4, TEAOH/SiO2 ratio of 0.06, Na2O/SiO2 ratio of 0.05 for crystallizing at 170 °C more than 16 h. The typical physico-chemical properties of samples were characterized by the techniques of XRD, N2-adsorption and FT-IR. The supported NiMo/Beta-Al2O3 series catalysts with different beta contents were prepared and evaluated in a fixed bed microreactor with FCC diesel. HDS results indicated that NiMo/Beta-Al2O3 series catalysts exhibited higher HDS activities compared with the conventional NiMo/Al2O3 catalysts, and S in the best product obtained over the catalyst with beta content of 32% was 8.4 μg g−1 which met the S regulation of ultra clean diesel in Euro-V specification. Combined with the sulfur distributions by GC–PFPD method, it could be found that the incorporation of acidic zeolite in the support could favor the deep removal of sulfur compounds.Graphical abstractHigh crytallinity of beta, as shown in the figure above, was in situ synthesized from kaolin clay as the unique sources of silica and alumina. NiMo/Beta-Al2O3 catalyst with beta content of 32 m% exhibited higher HDS activity (99.4%) compared with NiMo/Al2O3 (98.7%), and S in the best product was 8.4 μg g−1 which met Euro-V specification.Download high-res image (188KB)Download full-size imageHighlights► High crytallinity of beta was in situ synthesized from kaolin clay. ► NiMo/Beta-Al2O3 catalyst exhibited higher HDS activities compared with NiMo/Al2O3. ► S in the best product was 8.4 μg g−1 which met Euro-V specification.

•A highly efficient Au@CdS/MIL-101 heterostructure was synthesized.•The Au@CdS/MIL-101 heterostructure presents a higher H2 evolution rate.•The H2 evolution rate of Au@CdS/MIL-101 is 2.6 times higher than that of pure CdS.•The enhanced performance is ascribed to MIL-101 and surface plasmon resonance of Au.A novel and highly efficient three-component Au@CdS/MIL-101 heterostructure was successfully synthesized. The MIL-101(Cr) with large surface area was introduced as a matrix for the well-dispersed growth of Au nanoparticles, and the CdS was selectively coated on the Au nanoparticles. Under visible light irradiation, the Au@CdS/MIL-101 heterostructure presents superior hydrogen evolution rate over the pure CdS, CdS/MIL-101 and Au/MIL-101 composites. The Au@CdS/MIL-101 heterostructure exhibits an unusual H2 production rate of 250 μmol h−1/10 mg, which is 2.6 times higher than that of pure CdS. The performance enhancement of Au@CdS/MIL-101 heterostructure can be attributed to the following reasons: (i) the large surface area of MIL-101(Cr) can effectively disperse the Au and CdS nanoparticles, resulting in more active adsorption sites and reaction centers. (ii) the strong surface plasmon resonance absorption of Au could accelerate the charge transfer and extend the light response spectrum of CdS. This three-component Au@CdS/MIL-101 heterostructure combining the large surface area of MOF and the surface plasmon resonance of Au into a single structure may provide a potential way to design highly efficient and solar-energy-harvesting photocatalysts.

A series of Al2O3–ZrO2 composite supported NiMo catalysts with various ZrO2 contents were prepared. Several techniques including XRD, SEM, N2 physisorption, H2-TPR, and UV–vis DRS were used for typical physico-chemical properties characterization of the ZrO2–Al2O3 composite supports and their NiMo/ZrO2–Al2O3 catalysts. The test results showed that the composite supports prepared by the chemical precipitation method existed as amorphous phase in the samples with insufficient contents of ZrO2, and the incorporation of ZrO2 into supports provided a better dispersion of NiMo species, which made their reductions become easier. The pyridine-adsorbed FT-IR results indicated that the Lewis acid sites of catalysts increased significantly by the introduction of ZrO2 into the supports. The activities of these catalysts for diesel oil hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) were evaluated in a high pressure micro-reactor system. The results showed that the ZrO2–Al2O3-supported NiMo catalysts with suitable ZrO2 contents exhibited much higher catalytic activities than that of Al2O3-supported one, and when the ZrO2 contents were 15% and 5%, the NiMo/Al2O3–ZrO2 catalysts presented the highest HDS and HDN activities, respectively.

A new type of zeolite beta (denoted as MB) with multi-pore system was synthesized by using in situ synthesized method from kaolin mineral in this study. NiW/Al2O3–MB and NiW/TiO2–Al2O3–MB catalysts were prepared and the hydrodesulfurization (HDS) activities of these catalysts were evaluated with FCC diesel feed. The samples were characterized by N2 physisorption, XRD, SEM, TPR, FT-IR spectroscopy of pyridine adsorption, HRTEM and XPS techniques. The HDS results showed that the MB-containing catalyst exhibited much higher HDS conversion (98.7%) than that of NiW/γ-Al2O3 (97.5%). The incorporation of TiO2 into the composite supports further increased the HDS conversion (99.3%) of NiW/TiO2–Al2O3–MB. The higher HDS activity was mainly associated with the appropriate ratio of B/L (Brönsted acid/Lewis acid) and the enhanced hydrogenation activity.

The nanometric La2−xKxCuO4 oxide catalysts with K2NiF4-type structure were prepared by auto-combustion method using citric acid as a ligand and an adjusting agent of particle-size and morphology. The structures and physico-chemical properties of these perovskite-like oxides were examined by means of XRD, FT-IR, H2-TPR and chemical analysis. The catalytic activities for the simultaneous removal of soot and NOx were evaluated by a technique of the temperature-programmed oxidation reaction (TPO). In the La2−xKxCuO4 catalysts, the partial substitution of K for La at A-site leads to the increase of the concentrations of Cu3+ and oxygen vacancy. Thus, it enhances the catalytic activity for simultaneous removal of NOx and diesel soot, and the optimal substitution amount of potassium x is equal to 0.5 among these samples. T10, T50, T90 are 376, 438, 487 °C and PN2 is 22%, respectively, for simultaneous removal of NOx and soot particulates over the La1.5K0.5CuO4 catalyst under loose contact conditions between the catalyst and soot.

Three-dimensionally ordered macroporous (3DOM) La1−xKxCoO3 (x = 0–0.3) perovskite-type oxide catalysts with large pore sizes and interconnected macroporous frameworks were successfully synthesized by a novel method of carboxy-modified colloidal crystal templates (CMCCT). The obtained catalysts were characterized by means of XRD, FT-IR, SEM, TEM, BET, XPS, and H2 TPR. The detailed preparation process was investigated using in situ TG–DSC, Raman, and EDS analyses. The sp2-hybridized carbon atoms of the modified polymer templates can be converted to sturdy amorphous carbon materials by calcination under an inert atmosphere to prevent the macrostructure from collapsing. The active site densities of catalysts were determined by isothermal anaerobic titration, and their turnover frequency (TOF) values were then calculated. The catalytic performances for soot combustion were evaluated using temperature-programmed oxidation (TPO) reaction technology. 3DOM La1−xKxCoO3 catalysts exhibited catalytic activities as high as that of noble metal Pt catalysts under loose contact conditions.Graphical abstractThe three-dimensionally ordered macroporous perovskite La1−xKxCoO3, prepared using a novel carboxy-modified colloidal crystal template, shows excellent performance in catalytic for soot combustion.Download high-res image (69KB)Download full-size imageHighlights► A novel method of carboxy-modified colloidal crystal templating was reported. ► 3DOM La1−xKxCoO3 catalysts were firstly synthesized. ► The preparation process of 3DOM catalyst was investigated by means of in situ TG–DSC. ► The active site density of catalyst was determined by isothermal anaerobic titration. ► The catalyst exhibited the catalytic activity as high as that of Pt catalyst.

The ultrasmall Ag nanoparticles supported on silica were prepared by a novel and facile method, which was based on the introduction of the functional monomer salicylaldimine Schiff base into a SiO2 matrix. The ultrasmall silica-supported Ag nanoparticles were characterized by means of XRD, TEM, UV–Vis, XPS and BET, and tested for CO oxidation. It was found that the catalytic oxidation of CO over the ultrasmall Ag nanoparticle catalysts was a strong size dependent reaction and the Ag particle size in a range of 3–5 nm was favorable for CO oxidation.Download full-size imageResearch Highlights►The ultrasmall SiO2-supported Ag nanoparticles were prepared by a novel and facile method. ►The CO oxidation catalyzed by the ultrasmall Ag nanoparticles was a strong size dependent reaction. ►The Ag nanoparticle size in a range of 3–5 nm was favorable for the CO catalytic oxidation.

A series of HZSM-5 zeolites modified by different amounts of phosphorus (P/HZSM-5) were prepared. The physicochemical features of P/HZSM-5 catalysts were characterized by means of XRD, BET, NH3-TPD, FT-IR spectra of adsorbed pyridine, etc., and their performances for the catalytic cracking of the mixed C4 alkanes to produce light olefins were investigated. The results indicated that phosphorus (P) modification not only modulated the amount of acidic sites and the percentage of weak acidic sites in total acidic sites, but also regulated the acid type, i.e., the ratio of L/B (Lewis acid/Brönsted acid). The introduction of P also altered the basic characteristics of HZSM-5 which was evidenced by CO2-TPD analysis. Consequently, P modification with suitable amount was favorable for enhancing the selectivity to light olefins, especially to propene. At the temperature of 650 °C, the maximum yields of propene and ethene were achieved 25.6 and 33.9%, which were higher than those over parent HZSM-5 by 7 and 4.5%, respectively. Aromatics yield was found to be decreased with the increasing P loading due to the reduction of strong acid and the formation of new basic site which inhibited the hydrogen transfer reaction. All this indicates that P-modified HZSM-5 zeolites are effective catalysts for the cracking of mixed C4 alkanes to produce more light olefins.P-modified HZSM-5 was highly effective catalyst for the catalytic cracking of the mixed C4 alkanes to produce light olefins. The fact that P addition could modify both the acidic and basic characteristics of HZSM-5 (see figure) which in turn promoted its catalytic performance, will throw new light on the design of novel catalysts for light olefins.

We successfully synthesized 3D ordered macroporous (OM) Pt@CeO2−x/ZrO2 catalysts by a co-precipitation method. This series of catalysts have a well-defined 3D-OM structure. We investigated the activity of the 3D-OM Pt@CeO2−x/ZrO2 catalysts with different shell thicknesses, and systematically studied the adsorption and desorption of NO on the 3D-OM Pt@CeO2−x/ZrO2via in situ DRIFTS. The 3D-OM support enhances the contact efficiency between the solid reactant and catalyst, while the Pt@CeO2−x core–shell nanoparticles with strong Pt–CeO2−x interaction lead to a larger number of active species. With increasing the Ce/Pt molar ratio, the thickness of the shell becomes larger and the activity of Pt@CeO2−x/ZrO2 becomes lower. Among the as-prepared core–shell catalysts tested, the 3D-OM Pt1.0@CeO2−x/ZrO2-1 catalyst with the proper thickness of CeO2−x nanolayer shell showed the highest catalytic activity for soot combustion.

A series of cadmium sulfide (CdS)/triptycene-based polymer (NTP) nanocomposites was fabricated via a facile precipitation process by using Cd(OAc)2, Na2S, and prefabricated NTP as raw materials. The photocatalytic hydrogen-generating capabilities of the novel CdS-NTP nanocomposites have been investigated in the presence of a sacrificial reagent. After hybridization with NTP, the rate of visible-light-driven hydrogen production of CdS-NTP is 10 times higher than that of pure CdS prepared under the same conditions. The photocorrosion of CdS is simultaneously suppressed and the composites show high stability. The high surface area and stable covalent structure of NTP confines the CdS quantum dots and prevents aggregation, thus increasing the catalytically active sites and enhancing the photocatalytic performance of the hybrid nanocomposites. This work demonstrates a high potential of using porous triptycene-based materials to develop multifunctional porous materials for semiconductor-based photocatalytic hydrogen evolution.

Polymeric carbon nitride is reported to be a promising candidate in environmental catalysis for NO decomposition carried out at elevated temperature. Theoretical calculations support a mechanism where Lewis basic site of g-C3N4 can donate electrons to the adsorbed NO, decreasing the bond order of N–O thus facilitating the reaction.

Pd nanoparticles were well dispersed on a new triptycene-based microporous polymer support by the gas bubbling-assisted membrane reduction (GBMR) method. The stability of Pd nanoparticles is improved by the porous support, and the materials show excellent performance for CO oxidation.

Presented here is a new strategy for the synthesis of metallamacrocycles (MC[n]) with different ring-size and guest selectivity via integrating a flexible trinuclear metal unit and a bridging organic ligand, and further body-centered cubic packing of these MCs results in the formation of three microporous MOFs for potential application in gas storage.

Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.

A series of photocatalysts of three-dimensionally ordered macroporous (3DOM) TiO2-supported core–shell structured Pt@CdS nanoparticles were facilely synthesized by the gas bubbling-assisted membrane reduction-precipitation (GBMR/P) method. All the catalysts possess a well-defined 3DOM structure with interconnected networks of spherical voids, and the Pt@CdS core–shell nanoparticles with different molar ratios of Cd/Pt are well dispersed and supported on the inner wall of uniform macropores. The 3DOM structure can enhance the light-harvesting efficiency due to the increase of the distance of the light path by enhancing random light scattering. And the all-solid-state Z-scheme system with a CdS(shell)–Pt(core)–TiO2(support) nanojunction is favourable for the separation of photogenerated electrons and holes because of the vectorial electron transfer of TiO2 → Pt → CdS. 3DOM Pt@CdS/TiO2 catalysts exhibit super photocatalytic performance for CO2 reduction to CH4 under simulated solar irradiation. Among the as-prepared catalysts, the 3DOM Pt@CdS/TiO2-1 catalyst with the moderate thickness of a CdS nanolayer shell shows the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 36.8 μmol g−1 h−1 and its selectivity for CH4 production by CO2 reduction is 98.1%. The design and versatile synthetic approach of the all-solid-state Z-scheme system on the surface of 3DOM oxides are expected to throw new light on the fabrication of highly efficient photocatalysts for CO2 reduction to hydrocarbon.

A series of vanadium-incorporated mesoporous materials V-KIT-6 with different vanadium contents were synthesized by combining a direct hydrothermal method with a pH adjusting method and applied as catalysts for the oxidative dehydrogenation of propane. The structures of the catalysts were characterized by various techniques including N2 adsorption–desorption, XRD, TEM, SEM, UV-vis DRS, H2-TPR and Raman spectroscopy. The results reveal that the pH value plays a key role in the structure of the catalysts and the incorporated content of vanadium in the synthesis process of V-KIT-6 materials. The framework-incorporation of various contents of vanadium under mild acidic conditions (pH = 5) preserves the well-defined 3D interconnected mesoporous features of KIT-6 and promotes the dispersion of vanadium oxide species. The V-KIT-6 catalysts show much higher catalytic selectivity and productivity to propylene in the oxidative dehydrogenation of propane than the corresponding supported vanadium catalyst. The highest selectivity sum of C2H4 + C3H6 (70.2%) is obtained over the 5V-KIT-6 catalyst; meanwhile, a high space-time yield (STYC3H6) of 3.91 kgpropylene kgcat−1 h−1 is obtained. The superior catalytic performance of the V-KIT-6 catalysts in the oxidative dehydrogenation of propane can be ascribed to the high concentration of highly dispersed active sites as well as the favorable property of mass transfer and accessibility of the active sites to the reactant molecules in the 3D interconnected mesopores.

Mn-promoted CeO2 is a promising catalyst for the low temperature selective catalytic reduction of NO by NH3. We investigated the mechanism of this reaction for a model in which Mn cations are doped into the CeO2(111) surface by quantum-chemical DFT+U calculations. NH3 is preferentially adsorbed on the Lewis acid Mn sites. Dissociation of one of its N–H bonds results in the key NH2 intermediate that has been experimentally observed. NO adsorption on this NH2 intermediate results in nitrosamine (NH2NO) that can then undergo further N–H cleavage reactions to form OH groups. The resulting N2O product is desorbed into the gas phase and can be re-adsorbed through its O atom on an oxygen vacancy in the ceria surface, resulting from water desorption. Water desorption is the most difficult elementary reaction step. This redox mechanism involves doped Mn as Lewis acid sites for ammonia adsorption and O vacancies in the ceria surface to decompose N2O into the desired N2 product.

Methanation and reverse water-gas shift reaction are two important reactions that could happen simultaneously during the process of CO2 reduction. Exploiting new catalysts with high selectivity towards one single process is highly desirable. It has been shown that isolated-Rh/TiO2 can selectively generate CO rather than CH4. A molecular level understanding would provide more insight into catalyst design for CO2 reduction. In the present contribution, the density functional theory method was employed to study the CO2 reduction reaction by H2 based on a Rh1/TiO2 (101) model. The co-adsorbed CO2 and H2 on the Rh atom can react with each other to form CO. The inhibition of further H2 adsorption on the CO pre-adsorbed Rh atom stops the following sequential hydrogenation of CO. This can explain the experimentally observed high selectivity of Rh1/TiO2 to CO. Different co-adsorption properties can be understood by the frontier orbital charge density symmetry matching principle. The same method has been extended to other metal systems (Ru, Pd and Pt) to identify candidate catalysts with high selectivity for CO2 reduction. Similar adsorption properties of isolated Pd with Rh may induce high selectivity towards CO. These results are expected to provide a prediction to find new selective catalysts for CO2 reduction.

Hierarchical porous materials especially the silica-based ones are undergoing rapid development due to potential applications in the fields of catalysis, adsorption, separation, and biomedical processes. Although various synthesis methods involving emulsions, colloids, and surfactants have been reported, synthesis of hierarchical porous silicas (HPS) with complex mesophase transformations by using a four-component microemulsion (surfactant/cosurfactant/oil/water) templating approach is still challenging. Herein, we have successfully synthesized porous silica materials by introducing n-butanol (Bu) as the cosurfactant and 1,3,5-trimethylbenzene (TMB) as the oil component in a four-component P123–n-butanol–1,3,5-trimethylbenzene–water system. By simply increasing the molar ratio of Bu to TMB continuously while keeping a fixed mass of TMB in the mean time, mesophase transformations, progressing from mesocellular foam (MCF) via a vesicle-like structure to an ordered 2D hexagonal structure (SBA-15), can be observed. Moreover, an opposite phase transformation process was also proved by gradually increasing the molar ratio of TMB to Bu by maintaining a certain value for the Bu content in the initial system. All the mixed phase silica materials including hexagonal–vesicle, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type show hierarchically porous structures. The mechanism for the mesophase transformation was proposed and a micelle/microemulsion method with bimodal templates was put forward to form hierarchical porous silicas with a mixed phase of the MCF–disordered-SBA-15-type structure. Furthermore, a series of Al-containing mesoporous silicas with different structures (hexagonal, vesicle, MCF, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type) were used as catalyst supports for dibenzothiophene hydrodesulfurization. The NiMo/Al-hierarchical porous silica catalyst with pore structures of MCF–disordered-SBA-15-type displayed the best hydrodesulfurization performance among all the studied catalysts.

Nanocomposite K–Co–CeO2 catalysts were synthesized by the controllable micropore-diffused co-reaction method. Due to the size-match nanometre effect between CeO2 support and active components and formation of NO2, these cheap nanocomposite catalysts exhibit super catalytic performances which are as good as a supported Pt catalyst under loose contact conditions for soot combustion.

The microstructure with open, interconnected macropores of 3DOM Ce1−xZrxO2, successfully prepared using PMMA colloidal crystal as template and cerium nitrate and zirconium oxide chloride as raw materials, facilitates the contact between soot and catalysts and results in much higher catalytic activity for diesel soot combustion than the corresponding disordered macroporous catalysts.

A series of PtSnAl/SBA-15 catalysts were prepared by incipient-wetness impregnation and their catalytic performance was tested for propane dehydrogenation. The catalysts were characterized by XRF, XRD, BET, TEM, UV-vis DRS, NH3-TPD, O2-TPO, 27Al MAS-NMR, XPS and in situ Raman analyses. The addition of aluminum enhances the interaction of the Sn support and consequently stabilizes the oxidation state of Sn during the propane dehydrogenation reaction. The acid centers formed by aluminum addition show close contact with metal centers (Pt), which favors the synergistic effect of the bifunctional active centers. High catalytic performance over PtSnAl0.2/SBA-15 was obtained, and one-pass propane conversion and propene selectivity are 55.9% and 98.5%, respectively. Moreover, the in situ Raman results indicated the faster coke formation rate of PtSnAl0.4/SBA-15 than that of PtSnAl0.2/SBA-15, which may be accelerated by strong acid sites by excess aluminum addition.