In this study, we found that the phenylhydroxylamine intermediate could desorb more easily from an Ir surface than from a Pt surface, which is beneficial for inhibiting the over-hydrogenation of phenylhydroxylamine to aniline. On the other hand, the Brφnsted acid functionalized ionic liquids with sulfonic acid and bisulfate anions were acidic enough to catalyze the Bamberger rearrangement to form p-aminophenol from phenylhydroxylamine. On this basis, a new catalytic system constructed by Ir/C and Brφnsted acid functionalized ionic liquid was applied, for the first time, to the one-pot hydrogenation of nitrobenzene to p-aminophenol. Our results indicate that the PAP selectivity of Ir/C and [SO3H-bmim][HSO4] Brφnsted functionalized ionic liquid was far more than that of the traditional Pt/C and sulfuric acid catalyst system. Furthermore, the dually functionalized ionic liquid ([HSO3-b-N-Bu3][HSO4]) can be used simultaneously as an acid catalyst and also as a surfactant, due to its higher lipophilicity. Therefore, our new catalytic system has unique advantages in the hydrogenation of nitrobenzene to p-aminophenol.

Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride (MA) to gamma-butyrolactone (GBL). Thus, Pd/C catalysts modified with different Sn loadings were synthesized, and characterized by XRD, XPS, TEM and elemental mapping. The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0–1.0 synthesized in the process of preparation. The maximum reaction rate was 0.57 mol-GBL/(mol-Pd min) and selectivity was 95.94% when the Sn/Pd mass ratio was 0.6. It might be attributed to the formation of Pd2Sn alloy and less amounts of Pd-SnOx sites.Download high-res image (77KB)Download full-size imageThe types of alloy phase and the amounts of the surface Pd-SnO(x) sites altered along with Sn/Pd mass ratios from 0–1.0 synthesized in the process of preparation. The maximum reaction rate was 0.57 mol-GBL/(mol-Pd min) and selectivity was 95.94% when the Sn/Pd mass ratio was 0.6. It might be attributed to the formation of Pd2Sn alloy and less amounts of Pd-SnO(x) sites.

•Ageing times have great influence on the surface properties and the catalytic performance.•The specific reaction rate formed a volcano curve with increasing aging time.•The Co3O4 aged for 8 h exhibited the best catalytic performance.•High catalytic activity strictly correlated to the surface ATetrahedral/AOctahedral.A series of Co3O4 catalysts were prepared by a facile precipitation method just changing the aging time and tested for methane combustion. It was found that the activity for the reaction increased firstly and then decreased with increasing aging time in the form of a volcano curve. The Co3O4 aged for 8 h (Co3O4-8) exhibited the best catalytic performance with the specific reaction rate (Rs) of 25.91 nmol s−1 m−2 at 340 °C, which was 29.5 times than Co3O4-96 sample, although the Co3O4-8 catalyst showed the minimum BET surface area and the largest particle size. The XPS and Raman results indicated that the Co3O4-8 catalyst possessed the highest ratio of ATetrahedral/AOctahedral at the surface of the catalyst. H2-TPR and in situ XRD results also confirmed the Co3O4-8 catalyst behaved with excellent high-temperature reduction ability. In combination with the activity performance, the Co3O4-8 catalyst had the best performance of methane combustion due to abundant active tetrahedral Co2+ cationic species. The long-term stability tests demonstrated that the step of aging in the process of preparation can improve water tolerance of Co3O4 catalyst for methane combustion.

•The content of ZrO2 significantly influences the ratio of ATetrahedral/AOctahedral and the surface active oxygen species.•ZrO2Co3O4 composite oxide with 2% ZrO2 exhibits better reducibility and presented best catalytic performance.•High activity ascribed to high surface areas, ATetrahedral/AOctahedral and surface active oxygen species.A series of ZrO2 modified Co3O4 catalysts prepared by co-precipitation method were characterized by XRD, Raman, SEM, XPS and H2-TPR, and used in the catalytic combustion of lean methane at low temperature. XRD and Raman results demonstrate that ZrO2Co3O4 is in the form of a Zr-Co-O solid solution. XPS result indicates that the content of ZrO2 in ZrO2Co3O4 composite oxide has a significant influence on the concentration of Co2+ in tetrahedral site (ATetrahedral/AOctahedral) and the surface active oxygen species, which are correlated to the activity of methane combustion. H2-TPR result shows that the ZrO2(2)-Co3O4 composite oxide exhibits better reducibility. Compared with pure Co3O4, the ZrO2(2)-Co3O4 composite oxide presented the highest activity with T90 of 335 °C. All these characterizations suggest that high activity in the lean methane combustion could be ascribed to high surface areas, ATetrahedral/AOctahedral and surface active oxygen species.

A novel Pd–P–C framework structure was fabricated by supporting Pd on a P-doped carbon layer coated with activated carbon. A P-doped carbon layer was generated via calcination of sodium hypophosphite and ethanediol under inert gas atmosphere. The catalysts were characterized by Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and were evaluated in the selective hydrogenation of p-CNB to p-CAN. The results indicate that the carbon layer generated via calcination of ethanediol presents a higher disordered structure and then the P-doped carbon layer becomes more ordered due to the formation of a P–C framework. Some electrons were transferred from C atoms adjacent to the P atoms to P atoms, which favors the formation of stable Pd–P species such as the Pd15P2 phase. Pd in the Pd–P–C framework structure possesses electron-rich properties resulting from electron transfer from C atoms to Pd atoms via P atoms, which induces the formation of electron-rich hydrogen (H−) when hydrogen was absorbed on the Pd particles. The produced electron-rich H− might prefer the nucleophilic attack on the nitro group rather than the electrophilic attack on the C–Cl bond. We suggest that it is responsible for the superior selectivity of up to 99.9% to p-CAN for the hydrogenation of p-CNB. The catalytic performance of the Pd particles supported on the P-doped carbon layer remains unchanged after five cycles indicating excellent stability.

The catalytic conversion of benzene and methanol to alkyl aromatic products is a promising way of converting nonpetroleum sources to fine chemicals. Ethylbenzene is the major by-product, which is still difficult to suppress. Besides, coke deposition on ZSM-5 catalysts is of serious concern on account of its impact on the catalyst deactivation and consequent loss in the production yield. In this study, Pt@ZSM-5 catalysts were synthesized using in situ hydrothermal synthesis techniques. The resultant catalysts exhibit a higher activity (60.1%) in comparison with impregnated Pt/ZSM-5 catalysts (56.3%), which is ascribed to the preservation of the pore volume and surface area in the resulting material. Notably, thanks to the high dispersion of Pt particles within the ZSM-5 nanocrystals, the Pt@ZSM-5 catalysts show superior anti-coking performance without deactivation after 300 h on stream, along with a high suppression ability towards the formation of ethylbenzene (<0.01%). Meanwhile, the confinement within the ZSM-5 crystals protects the Pt clusters from sintering and coalescence during thermal regeneration treatments. Such novel Pt@ZSM-5 catalysts exhibit excellent activity, remarkable stability and outstanding recyclability, thus providing an opportunity for benzene alkylation with methanol towards industrial production.

•Organic aqua regia (OAR) is a greener alternative to aqua regia to activate Au/AC catalysts.•Au(H2O)/AC(OAR) gave excellent catalytic performance for acetylene hydrochlorination.•OAR treatment affected the chemical state and dispersion of Au NPs.•Residual sulfur and nitrogen species may help stabilize the active cationic Au3+ species.In this paper, we demonstrate that the less toxic, relatively safe, and recyclable organic aqua regia (OAR) can be employed as a greener alternative solvent to conventional aqua regia to activate Au/AC catalysts for the hydrochlorination of acetylene. We show that Au-based catalysts prepared with HAuCl4 as precursor can be prepared initially in water (Au(H2O)/AC). Although catalysts prepared from aqueous HAuCl4 showed poor activity, it can be significantly enhanced by catalyst activation in OAR (Au(H2O)/AC(OAR)). In contrast to the catalyst activation procedure using aqua regia (Au(aq)/AC), we demonstrate that the new activation procedure leads to both improved activity and stability of the resulting Au(H2O)/AC(OAR) catalyst. Further analyses of X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) show that the variations of Au particle size and chemical state caused by OAR treatment promote Au oxidation and high dispersion. In addition, temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) indicated that the presence of residual sulfur and nitrogen species may help stabilize the cationic Au3+ species and generate a catalyst less prone to deactivation by increasing the reduction temperature of the Au3+ species and enhancing the adsorption of hydrogen chloride over the Au(H2O)/AC(OAR) catalyst. These results suggest that OAR can be substituted for conventional solvents to activate Au/AC catalysts for the hydrochlorination of acetylene.Download high-res image (90KB)Download full-size image

Mercuric chloride supported on activated carbon (HgCl2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl2 by sublimating from the surface of activated carbon causes the irreversible deactivation of mercury catalyst and environmental pollution. In this work, a ligand coordination approach based on the Principle of Hard and Soft Acids and Bases (HSAB) was employed to design more stable low-mercury catalyst. The low-mercury catalysts (4% HgCl2 loading) were prepared by using HgCl2 and potassium halides (KX, X = Cl, I) as precursors. The HgCl2-4KI/AC catalyst showed best catalytic stability than HgCl2/AC and HgCl2-4KCl/AC in the hydrochloriantion of acetylene. HgCl2 could form more stable complex with KI, K2HgI4 as the main active component of the HgCl2-4KI/AC catalyst. The characterizations of XRD and EDX analysis illustrated that the active component of HgCl2-4KI/AC was highly dispersed on the surface of activated carbon. The sublimation rates of HgCl2 from the catalysts verified that the active component with larger stability constant had better thermal stability. Using Hg(II) complexes with high stability constant as the active component may be the research direction of developing highly stable low-mercury catalyst for the hydrochlorination of acetylene.Download high-res image (73KB)Download full-size image

The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Brönsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.Download high-res image (109KB)Download full-size image

•One-step synthesis of B-doped mesoporous carbon as supports of Pd nanoparticles•Hydrodechlorination using formic acid-formate solutions as hydrogen source•The synergetic effects of Pd nanoparticles, mesoporous structure and B-dopedB-doped ordered mesoporous carbon (BOMC) was used as support to immobilize Pd nanoparticles and exhibited an excellent catalytic performance for the liquid phase catalytic hydrodechlorination of 4-chlorophenol (4-CP) using aqueous formic acid-formate solutions as hydrogen source. BOMC was synthesized via one-step hydrothermal route using boric acid as a boron source and resorcinol/hexamethylenetetramine as a carbon source by a self-assembly process with Pluronic F127 in aqueous solutions. The Pd/BOMC catalyst exhibited an excellent catalytic activity and stability which might be due to the synergetic effects between the stabilized Pd nanoparticles and the mesoporous structure of B-doped supports.

Using high-valent Au(III) catalysis is highly desirable in many reactions; however, it is plagued by the poor stability of Au(III) complexes. Still, conventional catalysts need high Au content makes the high price and demand for Au is one of the major obstacles limiting their large-scale application. Here we demonstrate that stable and catalytically active Au(III) complexes can be obtained using Supported Ionic Liquid Phase (SILP) technology. The resulting heterogeneous Au–IL/AC catalysts combine the advantages of the catalytic species being stabilised in the Au(III) form by forming a Au(III)–IL complex and the need for a less expensive metal catalyst because the active component can be better developed in a homogeneous reaction medium. When used in acetylene hydrochlorination reaction, this catalyst displayed an excellent specific activity and superior long-term stability. Under the same reaction conditions, the Au(III)–IL/AC catalyst shows higher activity and stability towards the vinyl chloride monomer (VCM) than IL-free Au/AC (C2H2 conversion = 72.1% at 180 °C compared to 16.1% without IL). It also delivered stable performance within the conversion of acetylene, reaching more than 99.4%, and there was only a 3.7% C2H2 conversion loss after running for 300 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 30 h−1. Its exceptional ability to maintain the high activity and stability further demonstrated the potential for the replacement of Hg-based catalysts for acetylene hydrochlorination.

Ethylbenzene is the major side product in benzene alkylation with methanol and it is difficult to be suppressed over hierarchical porous ZSM-5. Moreover, the separation of ethylbenzene from xylene still remains a great challenge. Our research indicated that ethylbenzene formation could be highly suppressed by changing the Si/Al ratio of the catalyst. Hierarchical porous ZSM-5 catalysts with different Si/Al ratios were prepared via reducing the amount of Al in the solvent evaporation assisted dry gel conversion method. In this method, tetra-n-propylammonium hydroxide was used as the direct agent to create micropores, and hexadecyltrimethoxysilane was added to create additional porosities by forming organic assemblies which occupied a certain space between zeolitic walls. The catalyst with a Si/Al ratio of 1800 could achieve high benzene conversion (59.5%) and high xylene selectivity (39.0%) as well as excellent suppression of ethylbenzene formation (<0.1%).

A dicyandiamide (DCDA)-additive impregnation method was used to prepare SiO2 supported Co catalyst (i.e. Co/SiO2-CN). The addition of DCDA molecules could produce nitrogen-doped carbon species with predominant pyrrolic nitrogen atoms on the SiO2 support. The nitrogen-doped carbon species formed not only improved the reduction of Co3O4 particles, but also facilitated the electron transfer from the pyrrolic nitrogen atoms to neighboring metallic Co0 particles during reduction on the Co/SiO2-CN catalyst, in contrast to the conventional impregnation derived Co/SiO2-IWI sample. Such an effect ameliorated the electron-deficient state of metallic Co0 particles that existed on the Co/SiO2-IWI catalyst and was favorable to CO dissociation. As a result, the DCDA-additive method derived Co/SiO2 shows a higher turnover frequency value than the conventional Co/SiO2-IWI catalyst in the Fischer–Tropsch synthesis reaction.

The advantage of visible-light photocatalysis lies in its use of clean, renewable, cheap visible light as a driving force. Recently heterogeneous visible light photocatalysts have drawn much attention due to their nature of easy recycling and simple chemical work-up. Immense effort has been devoted to the application of solar energy in the field of energy regeneration such as hydrogen production and the reduction of carbon dioxide. Recently, solar energy has also captured much attention in organic synthesis due to its unique advantages. This paper will review the state-of-the-art progresses in the application of heterogeneous visible-light photocatalysis in organic synthesis through four sections: oxidation of alcohols, oxidation of amines, carbon–carbon bond formation reactions, and carbon–hetero bond formation reactions.

Commercialization of acetylene hydrochlorination using AuCl3 catalysts has been impeded by its poor stability. We have been studying that nitrogen-modified Au/NAC catalyst delivered a stable performance which can improve acetylene hydrochlorination activity and has resistance to catalytic deactivation. Here we show that nitrogen and sulfur co-doped activated carbon supported AuCl3 catalyst worked as efficient catalysts for the hydrochlorination of acetylene to vinyl chloride. Au/NSAC catalyst demonstrated high activity comparative to Au/AC catalyst. Furthermore, it also delivered stable performance within the selectivity of acetylene, reaching more than 99.5%, and there was only a 3.3% C2H2 conversion loss after running for 12 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 1480 h−1. The presence of the sulfur atoms may serve to immobilize/anchor the Au and also help prevent reduction and sintering of the Au and hence improve the catalytic activity and stability. The excellent catalytic performance of the Au/NSAC catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.Nitrogen and sulfur co-doped activated carbon supported AuCl3 as efficient catalyst for acetylene hydrochlorination.

Activated carbon-supported mercuric chloride (HgCl2) is used as an industrial catalyst for acetylene hydrochlorination. However, the characteristic of easy sublimation of HgCl2 leads to the deactivation of the catalyst. Here, we showed that the thermal stability of the Hg/AC catalyst can be evidently improved when CsCl is added into the Hg/AC catalyst. Compared with the pure Hg/AC catalyst, the sublimation rate of HgCl2 from the Hg–Cs/AC catalyst decreased significantly and the Hg–Cs/AC catalyst showed better catalytic activity and stability in the reaction. This promoting effect is related to the existence of cesium mercuric chlorides (CsxHgyClx+2y) highlighted by XRD, HR-TEM and EDX analyses. Thus, reacting HgCl2 with alkali chlorides to form alkali-mercuric chlorides may be a key to design highly efficient and thermally stable mercuric chloride catalyst for hydrochlorination reactions.CsCl can interact with HgCl2, forming a new compound, CsxHgyClx+2y. The addition of CsCl changes the existing form of the Hg atoms in the catalyst, resulting in the improvement of the thermal stability and catalytic efficiency of the mercuric chloride catalyst under reaction conditions.

Commercialization of acetylene hydrochlorination using AuCl3 catalysts has been impeded by its poor stability. We have been studying CsCl as a promoter, which can improve acetylene hydrochlorination activity and has resistance to catalytic deactivation. InIII added to the Au–CsI/AC catalysts worked as efficient catalysts for the hydrochlorination of acetylene to vinyl chloride. A series of trimetallic catalysts (1AuxInIII4CsI/AC with x = 0.5, 1, 2, 3) were prepared and assessed for their ability to promote hydrochlorination of acetylene. The enhancement of stability observed for a Au/InIII/CsI weight ratio of 1:1:4 was particularly remarkable. It delivered stable performance within the conversion of acetylene, reaching more than 92.8%, and there was only 3.7% C2H2 conversion loss after running for 50 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 1480 h−1. Moreover, the 1Au1InIII4CsI/AC catalyst delivered stable performance with an estimated lifetime exceeding 6520 h at a C2H2 hourly space velocity of 50 h−1. H2-TPR, TEM, HCl-TPD, C2H2-TPD, XPS and TGA techniques were further applied to reveal the structural information on the Au–InIII–CsI/AC catalysts. The results reveal that the addition of InCl3 increased the electron density of Au3+ species via electron transfer from the In atoms to the Au3+ center which can increase the adsorption of hydrogen chloride and therefore improve the catalytic stability. These results demonstrate that the addition of metal additives CsCl and InCl3 results in a synergistic effect to enhance the activity and the stability of Au-based catalysts. The excellent catalytic performance of the 1Au1InIII4CsI/AC catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.

ZSM-5 materials with different SiO2/Al2O3 ratios (25, 50 and 80) were used as supports to prepare ZSM-5-supported CoRu Fischer–Tropsch synthesis (FTS) catalysts. The presence of polyethylene glycol molecules in the solution could deposit most of the Co3O4 particles on the exterior surface of the ZSM-5 support, leading to a high extent of reduction in the prepared CoRu/ZSM-5 catalysts. The use of ZSM-5 with a high alumina content (SiO2/Al2O3 = 25, 50) facilitated the production of more Brønsted acid sites on the supported CoRu catalysts, however, dealumination was favored during the preparation of these catalysts. The defects formed in the framework preferred to interact with the metallic Co0 particles in the reduced CoRu/ZSM-5 catalysts. The resultant electron-deficient Co0 sites thereby strongly adsorbed H species, resulting in the lower turnover frequency (TOF) in the FTS reaction. Decreasing the SiO2/Al2O3 ratio to 80 reduced the number of Brønsted acid sites on the catalyst, however, it avoided the unexpected dealumination. As a result, although the reduced CoRu/ZSM-5 catalyst with a SiO2/Al2O3 ratio of 80 had lower selectivity of gasoline-range hydrocarbons, it showed an about 2-fold higher TOF value than the reduced CoRu/ZSM-5 catalysts (SiO2/Al2O3 = 25, 50) in the FTS reaction.

1,1-Dichloroethene has many applications in industrial production and it holds great promise in developing a vapor phase catalytic dehydrochlorination process. We synthesized a carbon nitride material by dissolving dicyandiamide in N,N-dimethylformamide (DMF) as a precursor and using SBA-15 as a template. A carbon nitride material with a mesoporous structure and textured pores has been obtained and then characterized by N2-adsorption measurements, XRD, HRTEM, EDS and FT-IR. A mesoporous carbon nitride material with a surface area of 350 m2 g−1 and pore volume of 0.72 cm3 g−1 was fabricated, which also possessed triazine N heterocycles with extra amino groups. It is an outstanding heterogeneous base catalyst in the selective catalytic dehydrochlorination of 1,1,2-trichloroethane into 1,1-dichloroethene reaction with a maximum 1,1,2-trichloroethane conversion of 23.96% and maximum 1,1-dichloroethene selectivity of 100%. A total of 110 h stability experiment of the catalyst was provided and the selectivity stayed above 99% all through the experiment and the conversion remained no less than 15% for 35 h.

The synthesis of a vinyl chloride monomer (VCM) from acetylene hydrochlorination is a highly attractive coal-based route using mercury chloride (HgCl2) as the catalyst. On reducing the use of mercury and with increasing concerns about environmental issues, searching for alternative catalysts has gained interest in recent years. However, to achieve high yield and stability using a mercury-free catalyst in this reaction is a substantial challenge. We approach this question by probing a Cu-added AuCs/AC catalyst working as a highly active, stable and cost-effective catalyst for this reaction. Introducing Cu into the catalyst significantly increased the activity and stability compared to a bicomponent AuCs/AC catalyst, underscoring a remarkable synergistic effect of the three metals. The particularly remarkable enhancement of activity was observed for the catalyst with a Au/Cu/Cs weight ratio of 1:1:4 (Au = 0.25 wt%), which provided a high turnover frequency of 73.8 min−1 based on Au. Further experiments showed that the AuCuCs/AC catalyst delivered a stable performance during a 600 h test with the conversion of acetylene maintaining more than 98.8% at a C2H2 gas hourly space velocity of 50 h−1 and the estimated lifetime exceeding 6540 h. After a careful characterization of the AuCuCs/AC catalyst and additional catalytic tests, we concluded that the observed enhanced catalytic performance could be associated with the enhanced dispersion of Au particles, the stabilization of Au in the state of Au3+ and facile substrate C2H2 molecule desorption. Compared with the commercial high content HgCl2 catalyst (Hg = 12 wt%), this low content AuCuCs/AC catalyst (Au = 0.25 wt%) has similar activity, higher stability, relative low cost and environmental friendliness, meaning it has potential as an alternative to the HgCl2 catalyst for commercial production of VCM.

Supported noble-metal sulphide catalysts have attracted extensive scientific interest for their good selectivity in selective hydrogenation. However, the application of noble-metal catalysts is limited due to their lower activity, leading to harsh reaction conditions and poor conversion during hydrogenation reactions. In this study, Pd/C was sulphidized by H2S to prepare a series of core–shell structured Pd@PdxSy/C catalysts, which were characterized by BET, EDS, XPS, XRD and CO chemisorption to investigate the influences of sulphidation temperature, sulphidation time and sulphidation atmosphere on the structure of the resulting catalysts. The sulphidation of Pd/C at low temperatures resulted in a core–shell structured catalyst, Pd@PdxSy/C; with increasing sulphidation temperature, the size of Pd0 as the core decreased, and the thickness of palladium sulphides as the shell increased correspondingly. When the sulphidation temperature reached 150 °C, the resulting catalyst transformed to a complete palladium sulphide catalyst, PdxSy/C. The structure of Pd@PdxSy/C sulphidized at 30 °C was independent of sulphidation time and sulphidation atmosphere. The sulphidized catalysts were applied to the reductive alkylation of PADPA and MIBK to DBPPD. The sulphidized catalysts presented a much higher selectivity for DBPPD compared with Pd/C, and Pd@PdxSy/C showed higher activity than PdxSy/C; moreover, the greater amount of PdxSy content in the resulting catalyst led to a lower activity.

The effect of MgO and Pd modification on the catalytic performance of hierarchical porous ZSM-5 for benzene alkylation with methanol was investigated. The results indicated that the introduction of MgO could reduce the Brönsted acid sites which suppressed the side reaction of methanol to olefins and in turn effectively promoted the alkylation of benzene. However, the single modification of MgO could not completely suppress the formation of ethylbenzene and coke. Doping a small amount of Pd had a positive effect on inhibiting the generation of ethylbenzene and coke, which could be attributed to the hydrogenation of ethylene into ethane on Pd. The dual modified catalyst (MgO and Pd) exhibited high benzene conversion (56%) and xylene selectivity (39.1%), and the lowest ethylbenzene selectivity (0.13%) and coke content (0.4 wt%).

The regioselective addition of α-aminoalkyl radicals to 2,3-allenoates by visible-light-mediated electron transfer using 1 mol% of Ru(bpy)3(BF4)2 as a photocatalyst was successfully established. This photoredox protocol is a simple and effective method for the synthesis of unsaturated γ-aminobutyric ester derivatives.

Here we report a novel catalyst consisting of 400 ppm Ru and 4.24 wt% Cu supported on carbon nanotubes for the hydrochlorination of acetylene. We observed a synergy between Ru and Cu and obtained a highly active catalyst. The TOF of Cu400Ru/MWCNTs was higher than that of the HgCl2 catalysts.

In the challenging acetylene hydrochlorination to vinyl chloride over Au-based catalysts, Au–CsI catalysts are substantially more active and stable than their monometallic counterparts. Here we describe a novel nitrogen-modified activated carbon supported Au–CsI catalyst (1Au4CsI/NAC) that delivers stable performance for acetylene conversion reaching 90.1% and there was only 1.5% C2H2 conversion loss after 50 h under the reaction conditions of C2H2 hourly space velocity 1480 h−1. After a careful characterization of all the catalysts, we concluded that the nitrogen atoms’ influence on the stability of the Au–CsI catalysts correlates with the strengthening of the adsorption of hydrogen chloride to the catalyst and consequently inhibits Au3+ reduction under the reaction conditions.

The competitive reaction of methanol to olefins is difficult to be suppressed in benzene alkylation with methanol over hierarchical porous ZSM-5. The influence of ZnO content and different atmospheres on the catalytic performance of hierarchical porous ZSM-5 catalyst was investigated. The results indicated that the introduction of ZnO could form the Lewis acid sites of zinc species (ZnOH+) at the expense of the Brönsted acid sites, and the reduction of strong Brönsted acid would help to suppress the side reaction of methanol to olefins. However, the presence of ZnOH+ could catalyze the dehydrogenation reaction of light hydrocarbons to olefins which would result in the formation of coke under the nitrogen atmosphere, while the hydrogen atmosphere could inhibit the dehydrogenation ability of ZnOH+.

A simple and efficient method to prepare large and uniform palladium particles supported on oxygen-poor activated carbon is reported in this paper. Heat-treatment of Pd/C under H2 atmosphere removes the most oxygen-containing groups from the activated carbon, and results in large and uniform Pd particles with their average size about 17 nm. This catalyst was used for the solvent-free selective hydrogenation of o-chloronitrobenzene to o-chloroaniline (o-CAN). The large palladium particles improve the selectivity of o-CAN up to 99.8 %, and the oxygen-poor activated carbon exhibits a lipophilicity to decrease the resistance to the mass transfer of reactants. This catalyst shows great potential industrial application for the green and efficient synthesis of o-CAN.

Sulfur deactivation is a serious problem which largely limits the industrial application of noble metals as catalysts. Here we report a thermal oxidation method to regenerate sulfone poisoned Pd/C catalyst applied in the hydrogenation of sodium-m-nitrobenzene sulfonate (SNS). It was found that the initial activity of Pd/C catalyst could be substantially recovered after treating it in air at temperatures as low as 100 °C. And the catalyst could be reused for at least 20 times without the significant loss of activity. The properties of deactivated and regenerated catalysts were studied in detail by BET measurement, X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and Fourier transform infrared spectroscopy (FT-IR). The results indicated that the main surface sulfur species found on deactivated and regenerated Pd surfaces were Sn and sulfate (SO4), respectively. The change of the valence of sulfur species was found to be the key factor influencing the catalytic activity of the Pd-based catalyst.

The main goal of this work is to study the relationship between the surface chemistry of activated carbon (AC) and the performance of respective gold-supported catalysts in the acetylene hydrochlorination. For this purpose, a set of modified activated carbons with different levels of oxygenated groups on the surface, but with no major differences in their textural parameters, was prepared. A strong effect of the surface chemistry of activated carbon on the Au/AC catalytic activity was observed. Comparison of characterizations, catalytic results, and DFT calculations suggests that phenol, ether, and carbonyl groups on activated carbon surface are the key members governing the unique catalytic activity and stability of Au3+ catalysts. The comprehensive experimental and theoretical study of the surface chemistry of Au3+ supported on activated carbon support is believed to be of great benefit for the rational design of gold–carbon composite catalysts for acetylene hydrochlorination.

Carbon nanotube (CNTs) and activated carbon (AC) supported Pd and Ni catalysts were prepared for the (in situ) hydrogenation of phenol to cyclohexanone and cyclohexanol. The hydrophobic/hydrophilic properties of the catalysts were tailored by pretreating the carbonaceous support with HNO3 at various conditions and characterized by X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and transmission electron microscopy (TEM). The catalytic results suggested that Pd and Ni supported on CNTs show significantly higher activity than that supported on ACs. Pretreating the CNTs with HNO3 increases the local hydrophilicity of the active phase (by introducing oxygenated groups), which result in an increase in the cyclohexanone selectivity and strongly decrease the phenol conversion. The first-principles density functional theory calculation suggested that the adsorption/desorption behaviors of phenol, methanol, H2O, and cyclohexanone on the catalysts might be influenced highly by the hydrophobic/hydrophilic properties. The hydrophilic catalysts show high selectivity in cyclohexanone by lower conversion in phenol or vice versa.

Halogenated anilines have a wide range of applications in the production of pharmaceuticals and agrochemical substances, and thus it is of great importance to develop highly active and selective catalysts for the hydrogenation of halogenated nitrobenzenes. We approach this challenge by probing noble metal/non-noble metal oxide nanoparticles (NPs) catalysts. Carbon-supported Pd/SnO2 catalysts were synthesized by the chemical reduction method, and their catalytic activity was evaluated by the hydrogenation reaction of 2,4-difluoronitrobenzene (DFNB) to the corresponding 2,4-difluoroaniline (DFAN), showing a remarkable synergistic effect of the Pd and SnO2 NPs. The as-prepared Pd/SnO2/C catalysts were characterized using TEM, XRD, H2 TPD and XPS techniques. Modifications to the electronic structure of the Pd atoms through the use of SnO2 led to the suppression of the hydrogenolysis of the CF bond and the acceleration of nitrosobenzene (DFNSB) conversion and consequently, resulted in the inhibition of the formation of reactive by-products and may be responsible for the enhancements observed in selectivity.Pd/SnO2 catalysts were successfully prepared on carbon support, and the activity and selectivity of the Pd/SnO2/C catalyst were improved significantly.

This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C catalyst, minor amount of water reduces the induction time, increases the reaction rate and reaction TOFs. Water might enhance the diffusion, adsorption and dissociation of H2 on Pd catalysts.Minor amount of water has a significant role in enhancing the solvent-free hydrogenation of halogenated nitrobenzenes.

Mediated by visible light-induced photoredox catalysis and free of other catalysts, a new and efficient synthesis of methylene-bridged bis-1,3-dicarbonyl derivatives has been developed. A variety of N-methyl tertiaryamines and 1,3-dicarbonyl compounds were investigated in this reaction.Under catalyst free conditions in aqueous media, methylene-bridged bis-1,3-dicarbonyl derivatives were successfully prepared by a novel and efficient method using visible-light photocatalytic oxidation of N-methyl tertiaryamines.

Catalyzed by Ru(bpy)3(BF4)2, the photoredox coupling of tertiary amines with acrylate derivatives including Baylis–Hillman adducts under visible light irradiation was successfully established. The scope of the substrates was broad, and thus an array of γ-aminobutyric ester derivatives was obtained in moderate to good yields.

The selective hydrogenation of halogenated nitrobenzene (HNB) has been a great important chemical reaction in the fine chemical productions. In this study, the effect of metal particle size on the selective hydrogenation of HNB over Pd/C catalysts has been extensively investigated through the combination of theoretical (density functional theory calculations, DFT) and experimental methods. DFT calculations showed that the reaction barriers for dechlorination strongly depend on the type of reaction sites (terrace or edge), while the hydrogenation reaction barriers are nearly the same on different sites, which indicates that Pd nanoparticle size significantly affects the catalyst selectivity. Moreover, Pd nanoparticles with different sizes (from 2.1 to 30 nm) supported on activated carbon were synthesized using the methods developed by our group. In a 500 mL reactor, the selectivity is over 99.90% when the Pd nanoparticles are bigger than 25 nm. Finally, the industrial applications of the proposed catalyst were evaluated in several pilot factories. This study provides useful information on controlling the selectivity of other similar reactions catalyzed by noble-metal nanocatalysts.

Supported palladium sulfide catalysts are of great interest in selective hydrogenation reactions. In this work, “Pd4S”, “Pd3S”, “Pd16S7” and “PdS” supported on activated carbon were selectively synthesized by tailoring the H2-assisted sulfidation of Pd/C with H2S at 150–750 °C, and were characterized by means of XRD, XPS, TEM, HRTEM, EDS, BET and H2-TPR techniques. The results indicated that the sulfidation atmosphere, the sulfidation temperature and the metal–support interaction all played important roles in determining the crystal structure and composition of the PdxSy/C catalysts, which in turn gave different catalytic performances in the synthesis of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) by the reductive N-alkylation of aromatic amines. PdS/C showed the highest selectivity (>97%) and stability among all the PdxSy/C catalysts.

For carbon supported Pd catalysts, the surface properties of activated carbons (ACs) are closely related with the Pd particle size. In this study, phenolic groups were adjustably introduced on ACs by hydrothermally treating ACs under different temperatures (433–513 K). Pd/ACs catalysts were prepared by the wetness impregnation method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, and H2-temperature-programmed reduction (TPR). The results revealed that the size of Pd nanoparticles (NPs) was highly dependent upon the amount of phenolic groups. The density functional theory (DFT) study suggested that the enhanced binding between palladium clusters and surface functional groups (SFGs) modified carbon nanotubes (CNTs) in the sequence: CNTs–O > CNTs–OH > CNTs–COOH > CNTs. Both the experimental and theoretical results suggested that phenolic groups on the surface of ACs play a vital role in the stabilization of Pd NPs, which provides insight into how to treat/or choose carbon supports for the preparation of small noble metal particles.

A series of diphenyl-sulfide (Ph2S)-immobilized Pd/C catalysts (Pd–Ph2S(x)/C) were prepared using the wetness-impregnation and immobilization method. Pd–Ph2S(x)/C catalysts employed for the hydrogenation of o-chloronitrobenzene showed very high selectivity. The structure of Pd–Ph2S(x)/C with different molar ratio of ligand (x-values) was characterized by XPS and TG–DSC–MS. The results suggest a “saturated” surface ratio of Ph2S/Pd (about 0.3) was formed on the Pd–Ph2S(x)/C catalysts surface. The Ph2S immobilized on the Pd particle is quite stable, and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K. The possible catalytic mechanism of the Pd–Ph2S(x)/C catalyst was also discussed.A diphenyl-sulfide (Ph2S)-immobilized Pd/C catalytic system (Pd–Ph2S(x)/C) was developed and employed for the hydrogenation of o-chloronitrobenzene showed very high selectivity. The possible mechanism for the enhanced selectivity of the Pd–Ph2S(x)/C catalyst was proposed.

Promoted by diethyl azodicarboxylate, a novel and highly stereoselective synthesis of cis-β-enaminones via oxidative dehydrogenation and hydration of the substituted propargylamines was realized. The possible mechanism was also proposed.

Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics. The selectivity of above 99.9% to aromatic haloamines can be achieved at the conversion of 100%. The results of H2–TPD and FT-IR experiments show that Ni−H+ species possessing the properties of Lewis acid site on the surface of Raney Ni could be responsible for the hydrodehalogenation. When Raney Ni was treated by dicyandiamide, Ni−H+ species interacted with N atom from the dicyandiamide. This interaction was stable even at reaction temperature, which reduced the possibility to form the intermediate state of ArCl⋯H+Ni−. And then CCl bond could not be polarized and activated. The hydrodechlorination process was suppressed effectively.

A novel egg-shell Pd–S catalyst with palladium metal as the core and a membrane of palladium sulfide as the surface has been prepared by sulphidizing Pd/C with H2S. This catalyst is effective for the reductive alkylation of p-amino diphenylamine (PADPA) and methylisobutyl ketone (MIBK) to afford N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenedianine (DBPPD) with conversion up to 99.42% and selectivity to 97.46%. Comparing with the other common palladium sulfide catalysts, the membrane of palladium sulfide on the surface and the core of palladium metal cause the Pd on the surface of the new catalyst in a lower sulfur coordination, which improves its activity. Our result indicates that this new egg-shell Pd–S/C is an efficient hydrogenation catalyst.

A NiRu/SiO2 catalyst was prepared by a new method. The presence of polyethylene glycol (PEG) molecules allows their oligomer groups to interact with the metallic ions in the liquid, which creates small NiO particles (∼6 nm) that closely contact with RuO2 particles, while the PEG-free process forms large NiO particles (∼11 nm) with separated RuO2 on SiO2 after calcination in air. The formation of close contacts between NiO and RuO2 particles improves the promotional efficiency of Ru. Therefore, small NiO particles can be reduced at lower temperature than that of large NiO particles on SiO2, a finding that contrasts with the dispersion–reducibility dependence inherent to the oxide-supported nickel-based catalyst. This leads to smaller Ni particles (∼11 nm) on the PEG-additive-derived NiRu/SiO2-CP catalyst, in contrast to NiRu/SiO2-C (∼28 nm) catalyst prepared by the PEG-free process. In the methanation reaction, the NiRu/SiO2–CP catalyst has a lower initial turnover frequency (TOF) per mole of surface Ni, however, it shows better long-term stability. Instead, as a result, the NiRu/SiO2-CP catalyst has a higher TOF after reaction for 30 h than the NiRu/SiO2-C catalyst, which deactivates due to the deposition of less reactive carbon species.

N-Heterocyclic carbene (NHC) catalyzed direct carbonylation of dimethylamine leading to the formation of DMF was successfully accomplished under metal-free conditions. The catalytic efficiency was investigated and the turnover numbers can reach as high as >300. The possible mechanism was also proposed.

Reaction performances of hydrogen generated from aqueous-phase reforming (APR) of methanol or ethanol were investigated in hydrogenation of phenol, o-cresol and p-tert-butylphenol, over a Raney Ni or Pd/Al2O3 catalyst, respectively. The properties of the adsorbed hydrogen from aqueous-methanol/-ethanol, and H2-gas were studied by means of temperature-programmed surface reaction in liquid phase and temperature-programmed desorption. The results shown that the selectivities of cyclohexanone are 20.5% and 96.1%, 27.4% and 92.4%, and 12.6% and 71.1% in the hydrogenation of phenol with hydrogen from APR of methanol, APR of ethanol, and H2-gas over the Raney Ni and Pd/Al2O3 catalyst, respectively. The limited amount of adsorbed hydrogen from the APR of methanol or ethanol favors the formation of cyclohexanone, but excessive amounts of adsorbed hydrogen from H2-gas favors the formation of cyclohexanol in hydrogenation of phenol.

Selectivity difference between hydrogenation of acetophenone over carbon nanotubes (CNTs) and commercial activated carbons (ACs) supported Pd catalysts has been investigated. The selectivity of α-phenylethanol over the Pd/CNTs catalyst is significantly higher than that over the Pd/ACs. The optimal yield of α-phenylethanol over the Pd/CNTs catalyst is 94.2% at 333 K under atmospheric H2 pressure for 255 min, but it is only 47.9% over the Pd/ACs catalyst. HRTEM characterization and density functional theory (DFT) study of the two catalysts suggested that the defects of the carbon support are the main anchoring sites for Pd nanoparticles. Additionally, mechanistic study of the acetophenone hydrogenation over the two catalysts suggested that the different adsorption modes of reaction intermediates (products) on the two kinds carbon supported Pd nanoparticles are responsible for the dramatic selectivity difference.Graphical abstractThe catalytic hydrogenation of acetophenone over the Pd/CNTs catalyst shows significantly higher (-phenylethanol selectivity than that over the Pd/ACs catalyst due to the different adsorption modes of the reaction intermediates on the two kinds of catalysts.Highlights► High selective acetophenone hydrogenation over Pd/CNTs was observed. ► Selectivity of α-phenylethanol is ∼95% on Pd/CNTs and ∼5% on Pd/ACs. ► Pd nanoparticles were mainly adsorbed on the defects of both the CNTs and ACs support. ► Different adsorption modes of the α-phenylethanol on Pd nanoparticle lead to the selectivity difference.

In situ hydrogen from aqueous-methanol, instead of H2 or CO, was used to synthesize imines with a high selectivity from nitroarenes and carbonyl compounds over an Au–Pd/Al2O3 catalyst.

Promoted by CuCl/CCl4, a variety of sulfonyl azides and tertiary amines were successfully coupled to give sulfonyl amidine derivatives in good to excellent yields. A possible mechanism for this reaction is discussed.

Au/FeOx–TiO2, prepared by deposition–precipitation method, is an efficient and stable catalyst for the liquid phase selective hydrogenation of phthalic anhydride to phthalide under mild reaction conditions.

A route for the direct synthesis of N,N-dimethylaniline from nitrobenzene and methanol was developed through the sequential coupling of the hydrogen production from methanol, hydrogenation of nitrobenzene to produce aniline, and N-methylation of aniline over a pretreated Raney-Ni® catalyst (at 443 K in methanol). A high yield of N,N-dimethylaniline up to 98% was obtained by the proposed methodology. In this process, aniline was produced from in-situhydrogenation of nitrobenzene with hydrogen generated from methanol, or transfer hydrogenation of nitrobenzene with methanol as donor, while methanol acted as a hydrogen source, alkylating reagent and solvent, simultaneously. Additionally, a plausible mechanism of this one-pot reaction process has been described.

The hydrogenation of phenol to cyclohexanol under mild conditions (∼340 K) was achieved over Raney Ni catalyst in the aqueous phase. The adsorption–desorption properties of the reactants (phenol and H2) and the products (cyclohexanone and cyclohexanol) on the Raney Ni catalyst are different in the aqueous phase and the organic phase. The hydrogenation rate of phenol is improved because the Raney Ni catalyst adsorbs more H2 and phenol in water than in methanol. Meanwhile, the higher uptakes of H2 and the lower desorption rates for cyclohexanone on the Raney Ni catalyst in the aqueous system result in the further hydrogenation of cyclohexanone to cyclohexanol.

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and PN2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%–4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine.

A resource recycling technique of hydrogen production from the catalytic degradation of organics in wastewater by aqueous phase reforming (APR) has been proposed. It is worthy of noting that this technique may be a potential way for the purification of refractory and highly toxic organics in water for hydrogen production. Hazardous organics (such as phenol, aniline, nitrobenzene, tetrahydrofuran (THF), toluene, N,N-dimethylformamide (DMF) and cyclohexanol) in water could be completely degraded into H2 and CO2 with high selectivity over Raney Ni, and Sn-modified Raney Ni (Sn-Raney-Ni) or Pd/C catalyst under mild conditions. The experimental results operated in tubular and autoclave reactors, indicated that the degradation degree of organics and H2 selectivity could reach 100% under the optimal reaction conditions. The Sn-Raney-Ni (Sn/Ni=0.06) and Pd/C catalysts show better catalytic performances than the Raney Ni catalyst for the degradation of organics in water into H2 and CO2 by the aqueous phase reforming process.

The thermal chemistry of perfluoroethyl iodide (C2F5I) adsorbed on Cu(1 1 1) has been investigated by temperature-programmed reaction/desorption (TPR/D), reflection-absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS). I 4d and F 1s XPS spectra show that dissociative adsorption of C2F5I to form the surface-bound perfluroethyl (Cu–C2F5) moieties occurs at very low temperature (T < 90 K), while the C–F bond cleavage in adsorbed perfluroethyl (Cu–C2F5) begins at ca. 300 K. XPS and TPR/D studies further reveal that the reactions of βCF3αCF2(ad) on Cu(1 1 1) are strongly dependent on the surface coverage. At high coverages (⩾0.16 L exposure), the adsorbed perfluroethyl (Cu–C2F5) evolves, via α-F elimination, into the surface-bound tetrafluoroethylidene moieties (CuCF–CF3) followed by a dimerization step to form octafluoro-2-butene (CF3CFCFCF3) at 315 K as gas product. The surface-bound (Cu–C2F5) decomposes preferentially, at low coverages (⩽0.04 L), via consecutive α-F abstraction to afford intermediate, trifluoroethylidyne (CuCCF3), resulting in the final coupling reaction to yield hexafluoro-2-butyne (CF3CCCF3) at 425 K. However, at middle coverages (ca. 0.08–0.16 L exposure), the adsorbed perfluroethyl (Cu–C2F5) first experiences an α-F elimination and then prefers to loss the second F from β position to yield the intermediate of Cu–CF2–CFCu (μ-η,η-perfluorovinyl), which may further evolve into hexafluorocyclobutene (CF2CFCFCF2) at 350 K through cyclodimerization reaction. Our results have also shown that the surface reactions to yield the products, CF3CFCFCF3 and CF3CCCF3, obey first-order kinetics, whereas the formation of CF2CFCFCF2 follows second-order kinetics.

On the basis that endothermic aqueous-phase reforming of oxygenated hydrocarbons for H2 production and exothermic liquid phase hydrogenation of organic compounds are carried out under extremely close conditions of temperature and pressure over the same type of catalyst, a novel liquid system of catalytic hydrogenation has been proposed, in which hydrogen produced from aqueous-phase reforming of oxygenated hydrocarbons is in situ used for liquid phase hydrogenation of organic compounds. The usage of active hydrogen generated from aqueous-phase reforming of oxygenated hydrocarbons for liquid catalytic hydrogenation of organic compounds could lead to increasing the selectivity to H2 in the aqueous-phase reforming due to the prompt removal of hydrogen on the active centers of the catalyst. Meanwhile, this novel liquid system of catalytic hydrogenation might be a potential method to improve the selectivity to the desired product in liquid phase catalytic hydrogenation of organic compounds. On the other hand, for this novel liquid system of catalytic hydrogenation, some special facilities for H2 generation, storage and transportation in traditional liquid phase hydrogenation industry process are yet not needed. Thus, it would simplify the working process of liquid phase hydrogenation and increase the energy usage and hydrogen productivity.

In this study, diphenyl sulfide (Ph2S) was employed to prepare a series of Ph2S-modified Pd/C catalysts (Pd–Ph2S/C). Catalyst characterization carried out by Brunner–Emmet–Teller (BET), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and CO chemisorption uptake measurements suggested a chemical interaction between Ph2S and Pd. The ligand was preferably absorbed on the active site of Pd metal but after increasing the amount of Ph2S, the adsorption of Ph2S on Pd metal tended to be saturated and the excess of Ph2S partially adsorbed on the activated carbon. A part of Pd atoms without adsorbing any Ph2S still existed, even for the saturated Pd–Ph2S/C catalyst. The Pd–Ph2S/C catalysts exhibited a good selectivity of p-chloroaniline (p-CAN) in the hydrogenation of p-chloronitrobenzene (p-CNB). However, the chemisorption between Ph2S and Pd was not so strong that part of Ph2S was leached from Pd–Ph2S/C catalyst during the hydrogenation, which caused the decline of the selectivity of p-CAN over the used Pd–Ph2S/C catalyst. Resulfidation of the used Pd–Ph2S/C catalyst was effective to resume its stability, and the regenerated Pd–Ph2S/C catalyst could be reused for at least ten runs with a stable catalytic performance.

Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials. For instance, the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide. In this study, the chemisorption of sulfur on the surface of deactivated Pd/C was detected by energy dispersive spectrometer and X-ray photoelectron spectroscopy. Sulfur compounds poison the Pd/C catalyst and increase the formation of azo deposit, reducing the activity of catalyst. We report a mild method to regenerate the Pd/C catalyst: wash the deposit by N,N-dimethylformamide and oxidize the chemisorbed sulfur by hot air. The regenerated Pd/C catalyst can be reused at least ten runs with stable activity.

Nitrided hierarchical porous ZSM-5 was synthesized by nitridation of hierarchical porous ZSM-5 with flowing ammonia at elevated temperature. The samples were characterized by XRD, SEM, Nitrogen sorption isotherms, NH3-TPD and Py-IR, and evaluated in alkylation of benzene and methanol. The result indicated that the high specific surface area of parent ZSM-5 was maintained, while the Brönsted acidity was effectively adjusted by nitridation. Moreover, the high suppression of ethylbenzene was observed on nitrided catalyst and this could be attributed to the decrease of Brönsted acidity which suppressed the methanol to olefins reactions.The acidity of hierarchical porous ZSM-5 was effectively adjusted via nitridation and the catalytic performance in benzene alkylation with methanol was improved.

Activated carbon was tested as metal-free catalyst for hydrochlorination of acetylene in order to circumvent the problem of environment pollution caused by mercury and high cost by noble metals. Oxygen-doped and nitrogen-doped activated carbons were prepared and characterized by XPS, TPD and N2 physisorption methods. The influences of the surface functional groups on the catalytic performance were discussed base on these results. Among all the samples tested, a nitrogen-doped sample, AC-n-U500, exhibited the best performance, the acetylene conversion being 92% and vinyl chloride selectivity above 99% at 240 °C and C2H2 hourly space velocity 30 h− 1. Moreover, the AC-n-U500 catalyst exhibited a stable performance during a 200 h test with a conversion of acetylene higher than 76% at 210 °C at a C2H2 hourly space velocity 50 h− 1. In contrary, oxygen-doped catalyst had lower catalytic activities. A linear relationship between the amount of pyrrolic-N and quaternary-N species and the catalytic activity was observed, indicating that these nitrogen-doped species might be the active sites and the key in tuning the catalytic performance. It is also found that the introduction of nitrogen species into the sample could significantly increase the adsorption amount of acetylene. The deactivation of nitrogen-doped activated carbon might be caused by the decrease of the accessibility to or the total amount of active sites.The surface oxygenated groups introduced by liquid phase oxidizing process played a negligible role to affect catalytic performance, while the nitrogen species introduced by urea calcination did play a significant role and could be active site for hydrochlorination of acetylene. Take into the correlation between nitrogen species and catalytic performance consideration, the conclusion could be drawn that pyrrolic-N and quaternary-N might be the active sites and the key tuning catalytic performance.Download full-size image

A series of carboxylated long chain polyethylene glycols (abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid. These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes. The factors affecting their catalytic properties, e.g. relative molecular mass of polyethylene glycol, reaction temperature, platinum content, and type of alkenes, have been studied. It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain, and increased with reaction temperature. Moreover, these catalysts could be reused several times without a noticeable decrease in activity or selectivity. The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.

Promoted by diethyl azodicarboxylate, a novel and highly stereoselective synthesis of cis-β-enaminones via oxidative dehydrogenation and hydration of the substituted propargylamines was realized. The possible mechanism was also proposed.

In situ hydrogen from aqueous-methanol, instead of H2 or CO, was used to synthesize imines with a high selectivity from nitroarenes and carbonyl compounds over an Au–Pd/Al2O3 catalyst.

A novel Pd–P–C framework structure was fabricated by supporting Pd on a P-doped carbon layer coated with activated carbon. A P-doped carbon layer was generated via calcination of sodium hypophosphite and ethanediol under inert gas atmosphere. The catalysts were characterized by Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and were evaluated in the selective hydrogenation of p-CNB to p-CAN. The results indicate that the carbon layer generated via calcination of ethanediol presents a higher disordered structure and then the P-doped carbon layer becomes more ordered due to the formation of a P–C framework. Some electrons were transferred from C atoms adjacent to the P atoms to P atoms, which favors the formation of stable Pd–P species such as the Pd15P2 phase. Pd in the Pd–P–C framework structure possesses electron-rich properties resulting from electron transfer from C atoms to Pd atoms via P atoms, which induces the formation of electron-rich hydrogen (H−) when hydrogen was absorbed on the Pd particles. The produced electron-rich H− might prefer the nucleophilic attack on the nitro group rather than the electrophilic attack on the C–Cl bond. We suggest that it is responsible for the superior selectivity of up to 99.9% to p-CAN for the hydrogenation of p-CNB. The catalytic performance of the Pd particles supported on the P-doped carbon layer remains unchanged after five cycles indicating excellent stability.

A NiRu/SiO2 catalyst was prepared by a new method. The presence of polyethylene glycol (PEG) molecules allows their oligomer groups to interact with the metallic ions in the liquid, which creates small NiO particles (∼6 nm) that closely contact with RuO2 particles, while the PEG-free process forms large NiO particles (∼11 nm) with separated RuO2 on SiO2 after calcination in air. The formation of close contacts between NiO and RuO2 particles improves the promotional efficiency of Ru. Therefore, small NiO particles can be reduced at lower temperature than that of large NiO particles on SiO2, a finding that contrasts with the dispersion–reducibility dependence inherent to the oxide-supported nickel-based catalyst. This leads to smaller Ni particles (∼11 nm) on the PEG-additive-derived NiRu/SiO2-CP catalyst, in contrast to NiRu/SiO2-C (∼28 nm) catalyst prepared by the PEG-free process. In the methanation reaction, the NiRu/SiO2–CP catalyst has a lower initial turnover frequency (TOF) per mole of surface Ni, however, it shows better long-term stability. Instead, as a result, the NiRu/SiO2-CP catalyst has a higher TOF after reaction for 30 h than the NiRu/SiO2-C catalyst, which deactivates due to the deposition of less reactive carbon species.

Supported palladium sulfide catalysts are of great interest in selective hydrogenation reactions. In this work, “Pd4S”, “Pd3S”, “Pd16S7” and “PdS” supported on activated carbon were selectively synthesized by tailoring the H2-assisted sulfidation of Pd/C with H2S at 150–750 °C, and were characterized by means of XRD, XPS, TEM, HRTEM, EDS, BET and H2-TPR techniques. The results indicated that the sulfidation atmosphere, the sulfidation temperature and the metal–support interaction all played important roles in determining the crystal structure and composition of the PdxSy/C catalysts, which in turn gave different catalytic performances in the synthesis of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) by the reductive N-alkylation of aromatic amines. PdS/C showed the highest selectivity (>97%) and stability among all the PdxSy/C catalysts.

N-Heterocyclic carbene (NHC) catalyzed direct carbonylation of dimethylamine leading to the formation of DMF was successfully accomplished under metal-free conditions. The catalytic efficiency was investigated and the turnover numbers can reach as high as >300. The possible mechanism was also proposed.

Commercialization of acetylene hydrochlorination using AuCl3 catalysts has been impeded by its poor stability. We have been studying CsCl as a promoter, which can improve acetylene hydrochlorination activity and has resistance to catalytic deactivation. InIII added to the Au–CsI/AC catalysts worked as efficient catalysts for the hydrochlorination of acetylene to vinyl chloride. A series of trimetallic catalysts (1AuxInIII4CsI/AC with x = 0.5, 1, 2, 3) were prepared and assessed for their ability to promote hydrochlorination of acetylene. The enhancement of stability observed for a Au/InIII/CsI weight ratio of 1:1:4 was particularly remarkable. It delivered stable performance within the conversion of acetylene, reaching more than 92.8%, and there was only 3.7% C2H2 conversion loss after running for 50 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 1480 h−1. Moreover, the 1Au1InIII4CsI/AC catalyst delivered stable performance with an estimated lifetime exceeding 6520 h at a C2H2 hourly space velocity of 50 h−1. H2-TPR, TEM, HCl-TPD, C2H2-TPD, XPS and TGA techniques were further applied to reveal the structural information on the Au–InIII–CsI/AC catalysts. The results reveal that the addition of InCl3 increased the electron density of Au3+ species via electron transfer from the In atoms to the Au3+ center which can increase the adsorption of hydrogen chloride and therefore improve the catalytic stability. These results demonstrate that the addition of metal additives CsCl and InCl3 results in a synergistic effect to enhance the activity and the stability of Au-based catalysts. The excellent catalytic performance of the 1Au1InIII4CsI/AC catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.

ZSM-5 materials with different SiO2/Al2O3 ratios (25, 50 and 80) were used as supports to prepare ZSM-5-supported CoRu Fischer–Tropsch synthesis (FTS) catalysts. The presence of polyethylene glycol molecules in the solution could deposit most of the Co3O4 particles on the exterior surface of the ZSM-5 support, leading to a high extent of reduction in the prepared CoRu/ZSM-5 catalysts. The use of ZSM-5 with a high alumina content (SiO2/Al2O3 = 25, 50) facilitated the production of more Brønsted acid sites on the supported CoRu catalysts, however, dealumination was favored during the preparation of these catalysts. The defects formed in the framework preferred to interact with the metallic Co0 particles in the reduced CoRu/ZSM-5 catalysts. The resultant electron-deficient Co0 sites thereby strongly adsorbed H species, resulting in the lower turnover frequency (TOF) in the FTS reaction. Decreasing the SiO2/Al2O3 ratio to 80 reduced the number of Brønsted acid sites on the catalyst, however, it avoided the unexpected dealumination. As a result, although the reduced CoRu/ZSM-5 catalyst with a SiO2/Al2O3 ratio of 80 had lower selectivity of gasoline-range hydrocarbons, it showed an about 2-fold higher TOF value than the reduced CoRu/ZSM-5 catalysts (SiO2/Al2O3 = 25, 50) in the FTS reaction.

Using high-valent Au(III) catalysis is highly desirable in many reactions; however, it is plagued by the poor stability of Au(III) complexes. Still, conventional catalysts need high Au content makes the high price and demand for Au is one of the major obstacles limiting their large-scale application. Here we demonstrate that stable and catalytically active Au(III) complexes can be obtained using Supported Ionic Liquid Phase (SILP) technology. The resulting heterogeneous Au–IL/AC catalysts combine the advantages of the catalytic species being stabilised in the Au(III) form by forming a Au(III)–IL complex and the need for a less expensive metal catalyst because the active component can be better developed in a homogeneous reaction medium. When used in acetylene hydrochlorination reaction, this catalyst displayed an excellent specific activity and superior long-term stability. Under the same reaction conditions, the Au(III)–IL/AC catalyst shows higher activity and stability towards the vinyl chloride monomer (VCM) than IL-free Au/AC (C2H2 conversion = 72.1% at 180 °C compared to 16.1% without IL). It also delivered stable performance within the conversion of acetylene, reaching more than 99.4%, and there was only a 3.7% C2H2 conversion loss after running for 300 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 30 h−1. Its exceptional ability to maintain the high activity and stability further demonstrated the potential for the replacement of Hg-based catalysts for acetylene hydrochlorination.

Ethylbenzene is the major side product in benzene alkylation with methanol and it is difficult to be suppressed over hierarchical porous ZSM-5. Moreover, the separation of ethylbenzene from xylene still remains a great challenge. Our research indicated that ethylbenzene formation could be highly suppressed by changing the Si/Al ratio of the catalyst. Hierarchical porous ZSM-5 catalysts with different Si/Al ratios were prepared via reducing the amount of Al in the solvent evaporation assisted dry gel conversion method. In this method, tetra-n-propylammonium hydroxide was used as the direct agent to create micropores, and hexadecyltrimethoxysilane was added to create additional porosities by forming organic assemblies which occupied a certain space between zeolitic walls. The catalyst with a Si/Al ratio of 1800 could achieve high benzene conversion (59.5%) and high xylene selectivity (39.0%) as well as excellent suppression of ethylbenzene formation (<0.1%).

A dicyandiamide (DCDA)-additive impregnation method was used to prepare SiO2 supported Co catalyst (i.e. Co/SiO2-CN). The addition of DCDA molecules could produce nitrogen-doped carbon species with predominant pyrrolic nitrogen atoms on the SiO2 support. The nitrogen-doped carbon species formed not only improved the reduction of Co3O4 particles, but also facilitated the electron transfer from the pyrrolic nitrogen atoms to neighboring metallic Co0 particles during reduction on the Co/SiO2-CN catalyst, in contrast to the conventional impregnation derived Co/SiO2-IWI sample. Such an effect ameliorated the electron-deficient state of metallic Co0 particles that existed on the Co/SiO2-IWI catalyst and was favorable to CO dissociation. As a result, the DCDA-additive method derived Co/SiO2 shows a higher turnover frequency value than the conventional Co/SiO2-IWI catalyst in the Fischer–Tropsch synthesis reaction.

The advantage of visible-light photocatalysis lies in its use of clean, renewable, cheap visible light as a driving force. Recently heterogeneous visible light photocatalysts have drawn much attention due to their nature of easy recycling and simple chemical work-up. Immense effort has been devoted to the application of solar energy in the field of energy regeneration such as hydrogen production and the reduction of carbon dioxide. Recently, solar energy has also captured much attention in organic synthesis due to its unique advantages. This paper will review the state-of-the-art progresses in the application of heterogeneous visible-light photocatalysis in organic synthesis through four sections: oxidation of alcohols, oxidation of amines, carbon–carbon bond formation reactions, and carbon–hetero bond formation reactions.