•Nanostructured CuFeMg-LDHs/CFs composites were synthesized by co-precipitation.•CuFe bimetallic nanoparticles were obtained by reducing CuFeMg-LDHs/CFs.•The catalysts show good activity and selectivity for higher alcohols synthesis.•The promote effect of CFs was studied.•The deactivation reason of the CuFe bimetallic catalysts was investigated.Higher alcohols synthesis (HAS) has attracted widespread attention since higher alcohols have a significant potential to be used as fuel additives and other intermediates for chemical feed stocks. HAS is a strong exothermal reaction which could lead to the formation of hotspots on the catalysts. CuFe based catalysts, in which the synergistic effect of Cu and Fe is critical, are one of the most promising catalysts. However, the stability of the catalysts and the selectivity to higher alcohols would be largely deteriorated by the hotspots. Based on the excellent thermal conductivity of carbon fibers (CFs) and the uniform distribution of metal ions in layered double hydroxides (LDHs), nanostructured CuFeMg-LDHs/CFs composites was synthesized by co-precipitation in this work and used for higher alcohols synthesis. After in situ reduction, the small-sized uniformly dispersed CuFe bimetallic nanoparticles were obtained, which contributes to the formation of C2+ alcohols. As a consequence, the resultant CuFeMg-LDHs/CFs composite exhibited better catalytic performance and higher selectivity to C2+ alcohols than the pristine CuFeMg-LDHs did. After a 500 h reaction test, the resultant catalyst showed a certain degree of deactivation, which was mainly attributed to the separation of Cu and Fe species.

•YRh0.5Fe0.5O3 with perovskite structure was loaded on ZrO2 by using citrate complexing method.•The formation of YRh0.5Fe0.5O3 is much favorable for generating Rh-Fe alloy NPs..•YRh0.5Fe0.5O3/ZrO2 exhibited good activity and high selectivity to alcohols.•Among the alcohols, the mass fraction of ethanol was 74%.•The formation of Rh-Fe alloys favors the improvement of the selectivity to ethanol.Traditional Rh-Fe catalysts usually exhibit high alkane or methanol selectivity due to the existence of mono iron and rhodium in the catalysts, and thus the selectivity to higher alcohols is low. To overcome this problem, in this work, YRh0.5Fe0.5O3 with perovskite structure was loaded on ZrO2 by using the citrate complexing method and used for higher alcohols synthesis. Compared with RhOx/ZrO2, YRhO3/ZrO2 and Rh-FeOx/ZrO2, the prepared YRh0.5Fe0.5O3/ZrO2 exhibited better activity and higher selectivity to higher alcohols, the mass fraction of higher alcohols in the total alcohols is more than 80%, especially ethanol occupied 74%. The high selectivity and activity of YRh0.5Fe0.5O3/ZrO2 are attributed to the formation of the homogeneous and highly dispersed Rh-Fe alloys. YRh0.5Fe0.5O3/ZrO2 also showed very good stability. More importantly, this preparation scheme can be extended for the preparation of other multi-component nano alloy catalysts.Download high-res image (143KB)Download full-size image

The critical problem for CO methanation catalysts to produce synthetic natural gas is deactivation due to carbon deposition and/or sintering of the active components. It was reported that Ni/La2O3 has better resistance to sintering and can eliminate the carbon deposited via lanthanum containing compound. However, the lanthanum oxide has low surface area, mechanical strength and stability. To overcome this problem, a new scheme has been proposed in this study by supporting the perovskite-type oxide of LaNiO3 on SiO2. Nickel and lanthanum ions are evenly dispersed at atomic level in the nanocrystallites of LaNiO3, after reduction highly dispersed small Ni nanoparticles were supported on La2O3 which spread on SiO2. Thus, Ni/La2O3 was loaded on SiO2. The catalysts were characterized by means of BET, XRD, HRTEM + EDX, H2 chemisorption, ICP, and TGA techniques, and their catalytic performances were measured for CO methanation from syngas to generate CH4. The prepared catalyst derived from LaNiO3/SiO2 showed very good catalytic performance, especially showed very high resistance towards carbon deposition and nickel sintering. The NiO-La2O3/SiO2 prepared by common incipient-wetness impregnation method was investigated for comparison. This method can be extended for loading other catalysts, for that a lot of metallic ions can be acted as the ions of perovskite-type oxides.

To improve the anti-sintering and anti-carbon deposition ability of the supported metallic nano catalysts, a new scheme for designing and preparing catalysts for CO methanation is presented in this work. In the scheme, a series of xLaNiO3/ZrO2 (x = 15%, 20%, 25%) catalysts were prepared according to the citrate complexing method. The catalysts were characterized by using BET, XRD, H2-chemisorption, H2-TPR, and TEM technologies. After reduction, the LaNiO3/ZrO2 catalyst precursor preferred to form Ni nanoparticles highly dispersed on ZrO2 and modified with La2O3. Compared with the catalyst prepared by the traditional impregnation method, the Ni/La2O3–ZrO2 derived from LaNiO3/ZrO2 showed a higher dispersion of Ni on ZrO2 and exhibited higher CO conversion and CH4 selectivity. Meanwhile, the LaNiO3/ZrO2 catalyst showed excellent stability owing to the significant improvement in both anti-carbon deposition and anti-sintering. The catalyst prepared according to this scheme intensified the interaction between Ni and La2O3, thus favoring the synergistic effect of La2O3 and Ni, which led to the high dispersion of Ni nanoparticles as well as the very good anti-sintering and anti-carbon deposition ability.

Nanostructured CuCo-LDH/CNT composites were successfully synthesized according to the co-precipitation method and firstly used for higher alcohol synthesis. The structural characterization and morphological observation demonstrated that CuCo-LDHs were in situ grown on the CNTs surface, and the CNTs support favored the dispersion of LDHs; meanwhile, a mechanism for growing the LDHs on CNTs was proposed, and the reported methods could be expanded to prepare other LDHs/CNT composites. After reduction, due to the strong interaction between CuCo-LDHs and CNTs, Cu–Co alloy, nanoparticles with small and uniform size were obtained and highly dispersed on the Al2O3 matrix and CNTs surface. In particular, the high thermal conductivity of CNTs suppressed the formation of hot spots, thus effectively inhibited the generation of hydrocarbons and CO2. The resultant CuCo-LDHs/CNTs composite exhibited better catalytic performance and higher selectivity to C2+ alcohols than the pristine LDHs did, which turned out to be one of the best catalysts for HAS.

•The deactivations of Cu–Co/ZrO2 for higher alcohols synthesis were investigated.•Phase separation and volatilization of cobalt are the major causes for the catalyst deactivation.•Sintering and coke deposition are not responsible for the deactivation.•Co2C might suppress the decomposition of Cu–Co alloy and volatilization of cobalt.The deactivations of Cu–Co alloy nanoparticles supported on ZrO2 for higher alcohols synthesis from syngas were investigated. The catalysts after reaction for 200 and 1500 h were compared and characterized by using N2 adsorption and desorption, X-ray diffraction, transmission electron microscopy, energy dispersive spectrometer, inductively coupled plasma mass spectrometry and thermo gravimetric analysis techniques. The characterization results showed that the deactivation of the Cu–Co/ZrO2 catalyst in the reaction period of 200–1500 h was mainly attributed to cobalt volatilization in the form of its carbonyl at the reaction temperature. Sintering of the Cu–Co alloy and coke deposited on the catalyst surface could hardly be observed, meaning that sintering and coke deposition are not responsible for the deactivation of the catalyst. At the same time, the formation of Co2C on the surface of Cu–Co alloy might play a protective role for the decomposition of Cu–Co alloy and the volatilization of carbonyl cobalt. According to the results, some possible recommendations were proposed for the design of Cu–Co-based catalysts.Deactivation of the Cu–Co/ZrO2 catalyst was mainly attributed to volatilization of cobalt species. Co2C might play a protective role for the decomposition of Cu–Co alloy and volatilization of cobalt species.

A series of layered double hydroxides (LDHs) with different Cu/Co ratios were prepared according to the co-precipitation method and used as catalyst precursors for higher alcohol synthesis. The prepared samples were characterized by XRD, TPR, SEM, TEM and BET techniques. After calcination, the LDHs were transformed into a mixture of CuO, Co3O4, CuCo2O4 and alumina, and these oxides were mixed uniformly with sizes of several nanometers. For the sample with a ratio of Cu/Co = 1/2, the copper and cobalt species are mainly in the CuCo2O4 phase. In the reduction process, the superior mixed copper and cobalt species in nanoscale were reduced to Cu–Co alloy, which was confirmed by the XRD and TEM results. The prepared bimetallic catalysts showed high activity, good stability and very high selectivity to C2+ alcohols. With the best catalyst, CO conversion of 51.8%, selectivity to alcohols of 45.8% and 94.3 wt% of C2+OH in the total alcohols were obtained at 250 °C, 3 MPa and GHSV of 3900 mL (gcat h)−1.

LaFeO3 supported Cu–Co bimetallic catalysts with high surface area and mesoporosity were prepared by impregnation combined with nanocasting method, and the resulting catalysts were used for higher alcohol synthesis (HAS) from syngas. These catalysts were characterized by using N2 adsorption and desorption, X-ray diffraction, temperature programmed reduction, transmission electron microscopy and energy dispersive spectrometry techniques. The results showed that the catalysts were highly active and selective to higher alcohols, and meanwhile stable for HAS. Characterization results indicated that Cu–Co was in the state of a solid solution alloy in the reduced catalysts, and the formation of Cu–Co alloy led to the high selectivity to higher alcohols. The elements in the catalysts were uniformly mixed and in interaction, thus sintering of the nanoparticles in the catalysts was restricted, resulting in a good stability. The high activity was mainly attributed to the high surface area and mesoporosity. Compared with Cu–Co/LaFeO3 prepared by conventional methods, Cu–Co/LaFeO3 with higher surface area and mesoporosity exhibited better activity and higher selectivity to higher alcohols. This design scheme may be applied to other bimetallic catalysts, and many transition metal ions can act as the lattice ions of perovskite-type oxides besides copper and cobalt.

•Small Ni–Co alloy nanoparticles were highly dispersed on the MgAlOx nanosheets.•The catalysts were prepared by calcining and reducing the MgNiCo/Al-LDH precursor.•MgNiCo/Al-LDH precursor was in situ grown on the macropores' walls of the γ-Al2O3.•The catalysts exhibited excellent catalytic performance for ethanol steam reforming.•The porous structure with the open access is beneficial for the mass transfer.The nanoparticles of Ni–Co alloy/MgAlOx nanosheets were supported on monolithic macroporous γ-Al2O3 by calcining and reducing a layered double hydroxide which contains elements of Mg, Ni, Co and Al. This precursor was in situ grown on the macropores’ walls of the γ-Al2O3 support by sharing the sole Al source. The catalysts and their precursors were characterized by using the techniques of XRD, TPR, TEM, SEM, ICP-OES, TG and N2 adsorption/desorption. The results indicate that small Ni–Co alloy nanoparticles were highly dispersed on the MgAlOx nanosheets and the porous structure with the open access of active sites should be beneficial for the mass transfer. The resultant catalysts exhibited excellent catalytic performance for ethanol steam reforming. The new preparation approach described here provides a practical and efficient method to support nano-bimetallic catalysts. The results suggest that this type of material possesses tremendous potential for future applications.

A novel preparation method for supported bimetallic alloy nanoparticles was investigated in this work. LaCoxNi1−xO3 with perovskite structure was prepared according to the citrate complexing method. Metal Ni and Co could be obtained by reducing the perovskite precursors, and the characterization results from X-ray diffraction, temperature programmed reduction and transmission electron microscopy indicated that nanoparticles of Ni–Co solid solution alloy with size of around 12 nm were formed. As a lot of metal ions can enter into perovskite lattice, this method should be extended to prepare various bimetallic or polymetallic nanoparticles. The resultant catalysts of Ni–Co alloy supported on La2O3 presented high activity and good stability for steam reforming of ethanol. Carbon deposition and sintering of the metal nanoparticles were investigated. After 10 hours' running at the relatively low reaction temperature of 550 °C, Co-rich catalysts showed some deactivation, which was ascribed to carbon deposition. The cobalt sites in the catalysts were inclined to form amorphous carbon, while the nickel sites tended to generate filamentous carbon, and the former led to more severe deactivation. At the relatively high reaction temperature of 700 °C, the bimetallic alloy catalysts presented better anti-sintering ability than the monometal catalysts.

•A new scheme for designing and preparing catalysts is presented.•Co–Cu alloy nanoparticles can be highly dispersed on La2O3-doped ZrO2.•The catalysts show excellent performance for the higher alcohol synthesis.A new scheme for designing and preparing the catalyst for higher alcohol synthesis was presented in this work. According to the scheme, a series of zirconia-supported LaCo1 − xCuxO3 catalysts were prepared by impregnating ZrO2 with a mixed solution composed of ions of copper, cobalt and lanthanum and citric acid. The catalysts were characterized by using XRD, TEM, BET, H2-TPR and XPS techniques. After reduction, the catalyst precursor favored to form nanoparticles of Co–Cu alloy highly dispersed on ZrO2 and modified with La2O3. The metal nanoparticles of Cu–Co alloy together with ZrO2 modified with La2O3 contributed to the excellent selectivity of higher alcohols as well as the very good stability.Structure evolutions of LaCo1 − xCuxO3/ZrO2 catalysts treated at different conditions.

•Ru nanoparticles can be highly dispersed on K-doped meso–macroporous SiO2.•The size of Ru particle has an obvious effect on the catalytic activity of K-Ru/SiO2.•K-Ru/meso–macroporous SiO2 is highly active and selective for CO-PROX.In this work, highly dispersed Ru nanoparticles which had a uniform small nanoparticle size were supported on K-promoted meso–macroporous SiO2 by using the simple impregnation method. The effect of the size of Ru nanoparticle on the catalytic performance for the preferential oxidation of CO (CO-PROX) in H2-rich gases was investigated. Meanwhile, the related mechanism on size effect was discussed. The catalysts were characterized by using techniques of transmission electron microscopy, temperature-programmed reduction and CO-chemisorption. The results indicate that the K-promoted Ru/SiO2 catalyst with the size of metal Ru particles at about 7 nm showed obviously higher turnover frequency (TOF) than that of K-Ru/SiO2 with smaller size of Ru particles of around 2 nm. As for oxidizing CO to CO2 on specific weight of ruthenium, the catalyst with the smaller size of metal Ru exhibited better performance owing to its much higher specific surface area of metal Ru. The catalyst with the smaller size of Ru nanoparticles showed much better methanation formation resistance for CO and CO2. The K-promoted and highly dispersed Ru on SiO2 exhibited excellent activity and selectivity for the CO-PROX reaction.

•A simple method for loading bimetal nano particles on metal oxide has been developed.•The alloy nano particles of Ni–Co were loaded on La-doped LaFeO3.•Ni–Co/La2O3–LaFeO3 showed very good catalytic performance for ethanol steam reforming.•The bimetal catalyst showed better anti-sintering ability than the mono-metal catalysts.Perovskite-type oxide (PTO) of LaFeO3 supported Ni–Co bimetallic catalysts were prepared by citric acid complexation-impregnation method and were used for the steam reforming of ethanol (SRE) to produce hydrogen. The anti-sintering and anti-coking properties of the catalysts for the reaction have been investigated and compared with the monometal catalysts. The catalysts were characterized by using temperature programmed reduction, X-ray diffraction, transmission electron microscopy and thermal analysis techniques. The results indicate that the catalyst was both highly selective to hydrogen and very stable for SRE reaction. Characterization results indicated that Ni–Co was in the state of solid solution alloy. Comparing with corresponding monometal catalysts, the bimetal catalyst exhibited better anti-sintering ability and similar anti-carbon deposition ability. The valuable information indicated in this work is that based on the special characters of PTO, bimetal nano-particles can be supported on metal oxides, which should be a new and promising method for preparing supported bimetal catalysts.

•NiO supported on solid solution was made according to citrate complexing method.•LaNiO3 supported on ceria was prepared by using impregnation method.•Both of the catalysts showed excellent performance for ethanol steam reforming.•The investigated catalysts showed very good anti-sintering ability.•Oxygen vacancies presented better ability to remove carbon than La2O2CO3.Two schemes for design and preparation of Ni–La–Ce oxide catalysts for steam reforming of ethanol were proposed in this work. The one via citrate complexing method was designed as NiO supported on ceria-lanthanum oxide (CL) solid solution, in which the strong interaction between NiO and CL solid solution was beneficial to inhibit the aggregation of NiO particles, and the abundant of oxygen vacancies existed in CL solid solution was in favor of carbon elimination from catalyst surface. The other was schemed as LaNiO3 with perovskite structure loaded on CeO2 support by using impregnation method, in which the particles of metal Ni derived from reduction of LaNiO3 were highly dispersed, and the formation of La2O2CO3 in the reaction process could act as the carbon scavenger. Both of the catalysts exhibited very good performance for steam reforming of ethanol (SRE), complete C2H5OH conversion was obtained with 70.3% of H2 selectivity at 400 °C over the catalyst obtained from former method and complete C2H5OH conversion was achieved at 450 °C with 67% of H2 selectivity over the catalyst from latter method. The catalyst made according to the citrate complexing method was more active for SRE and more selective for H2 production. Both of the catalysts displayed very good anti-sintering ability which was tested at 650 °C and at a high space velocity of 180,000 ml gcat−1 h−1 with reaction mixture of H2O/C2H5OH = 3 in mole ratio. The results indicated that both of oxygen vacancy and La2O2CO3 possessed the ability to remove the deposited carbon, and compared with La2O2CO3 the oxygen vacancy could reduce one third more of the carbon deposited according to TG tests.

•Pt–Ni alloy preferentially adsorbed on the surface of graphene rather than on SiO2.•Graphene-SiO2 monolith possesses the advantages providing by hierarchically porous.•Pt–Ni/Graphene-SiO2 catalysts show superior low-temperature activity for CO-PROX.In this work, nanoparticles of Pt–Ni alloy were supported on a new kind of composite which composed of graphene sheets and meso-macroporous SiO2, and the composite supported Pt–Ni catalyst was applied to the preferential oxidation of CO (CO-PROX) in H2-rich gases. The bimetallic Pt–Ni alloy catalyst was characterized by using techniques of SEM, TEM, XRD, TPR, CO chemisorptions and XPS. The catalyst showed excellent catalytic performance for CO-PROX with high activity at low temperature, high selectivity and very good stability, which was attributed to the following characters of the catalyst: Pt–Ni nanoparticles were in alloy state and highly dispersed, Pt–Ni nanoparticles were preferentially loaded on the surface of graphene sheets, and the meso-macroporosity of the composite markedly improved the mass transferring ability. This is a case study, and this kind of catalysts can be extended to other gas–solid catalytic reactions.

Hexaaluminate (HA) has been in-situ prepared by sharing the aluminum ions from Al2O3 intermediate layer (IML) supported on the FeCrAl alloy foil. The results show that the HA is vertically embedded in Al2O3 IML, and compared with Al2O3 IML, the obtained HA-Al2O3 composite IML shows better adhesion stability.

La1−xCaxFe1−xCoxO3 (x = 0.3, 0.5) perovskite-type oxide catalysts prepared by citric acid method were used for the steam reforming of ethanol (SRE) and oxidative steam reforming of ethanol (OSRE) to produce hydrogen. The anti-sintering and anti-coking properties of the catalysts for these two reactions have been investigated. The catalysts were characterized by temperature programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and thermal analysis techniques. The results indicated that the catalyst was highly selective to hydrogen, as well as very stable for OSRE reaction. The cobalt ions in the perovskite structure could be reduced to nanoparticles of metallic cobalt under the reduction atmosphere; the nano metallic cobalt could be oxidized and went back into the lattice of the perovskite structure under the oxidation atmosphere. The nanoparticles of metallic cobalt on the used catalyst could also be oxidized back into the perovskite structure. In the reaction process of OSRE, the cobalt species was possibly cycling as nanoparticles of metallic cobalt and cobalt ions in the perovskite structure, leading to its high anti-sintering stability.

Monolithic α-Al2O3 with a mesoporous Al2O3 layer coated onto its macropore walls was successfully prepared. Macroporous monolithic polystyrene foams were filled with alumina hydrosol followed by drying and high temperature calcination to obtain macroporous monolithic α-Al2O3 with good mechanical strength. The resulting macroporous alumina monolith was impregnated with an alumina sol solution containing Pluronic P123 as a mesoporous structure-directing agent. Following drying and calcination, a meso-macroporous monolithic alumina was obtained. The mesopores were assembled on the macropore walls, which elevated the specific surface area and the pore volume of the monoliths. The macropore walls had a measurable influence on the porosity of the mesoporous alumina on the walls. In the drying stage, the influence was ascribed to capillary force; in the calcination process, the influence was due to the confinement of the macropore walls to the mesoporous material. The prepared meso-macroporous alumina monolith was used as catalyst support for the preferential oxidation of CO in hydrogen-rich gases, and the monolith supported Pt–Ni catalyst showed high activity and selectivity for the reaction.

Nanorods (NR) and nanoparticles (NP) of ceria were prepared by hydrothermal synthesis method and used as catalyst support to load cobalt for steam reforming of ethanol (SRE). The catalysts were characterized by using temperature programmed reduction, X-ray diffraction, transmission electron microscopy and thermal analysis techniques. CeO2 NP had relatively smaller particle size and larger surface area, and CeO2 NR could form more oxygen vacancies. For SRE reaction, Co/CeO2 NP was more active and exhibited a little better anti-sintering ability, while Co/CeO2 NR showed obviously better anti-carbon deposition ability. The larger surface area and higher dispersion of cobalt oxide resulted in the higher activity for Co/CeO2 NP catalyst. Meanwhile, the stronger interaction between cobalt species and ceria was attributed to the better anti-sintering ability for Co/CeO2 NP. The improvement of the anti-carbon deposition for Co/CeO2 NR was owing to the generation of oxygen vacancies from the ceria nanorods.TEM images of Co/CeO2 with different morphologies (a) Co/CeO2 NP; (b) Co/CeO2 NR

In this work, perovskite-type oxides La1−xCaxFe0.7Ni0.3O3 were prepared by using a citrate complex method. The catalysts were employed in the reactions of steam reforming of ethanol (SRE) and oxidative steam reforming of ethanol (OSRE) to produce hydrogen. A reduction–oxidation cycle was proposed to overcome the problems of active component sintering and carbon deposition encountered in SRE reaction. In the ex-situ reactions, highly dispersed surface nickel particles formed during the reduction of La1−xCaxFe0.7Ni0.3O3, while during the introduction of an oxidative atmosphere these particles could be oxidized and restored back into the perovskite bulk. Owing to the existence of this segregation–incorporation cycle of nickel species in the perovskite oxides, the sintering of nickel particles under OSRE was found depressed effectively. Besides, this work proved that the oxygen in the feed is helpful to the elimination of deposited carbon. It seems promising for overcoming the problems of the active component sintering and carbon deposition in SRE reaction by regulating the redox ability of the perovskite-type oxides and the feed composition.

A series of carbon nano-tubes supported platinum-nickel catalysts were prepared and used for CO preferential oxidation in H2-rich streams. The catalysts were characterized by using N2-adsorption, XRD, HRTEM, H2-TPD and H2-TPR techniques. Effects of platinum and nickel loading amount, CO2 and H2O in the feed stream on the activity and selectivity over the catalysts were investigated. The results of catalytic performance tests show that the carbon nano-tubes supported Pt–Ni catalysts are very active and highly selective at low temperature for CO preferential oxidation in 1 vol. % CO, 1 vol. %O2, 50 vol. % H2 and N2 gases. Adding 12.5 vol. % of CO2 into the feed gases has slight negative influence on CO conversion. Adding 15 vol. % of H2O leads to a little decrease of CO conversion at the temperature range of 100–120 °C, which is proposed to be caused by capillary wetting of water in the micro-pores of carbon nano-tubes. As the reaction temperature is higher, adding water can improve CO conversion. The characterization results indicate that platinum species are in nano-particles uniformly dispersed on the carbon nano-tubes surface. There are two kinds of nickel species, one is interacted with platinum and likely to form Pt–Ni alloy in reduction process, the other is much highly dispersed on carbon nano-tubes and strongly interacted with the supports. The high activity of the catalysts is attributed to the interaction between Pt and Ni with the formation of Pt–Ni alloy.

Meso–macro-porous monolithic Pt–Ni/Al2O3 catalysts with platinum and nickel in interaction and in a highly dispersed state have been successfully prepared, and the obtained catalysts are highly efficient for CO removal from hydrogen rich gases via preferential oxidation; the results show that preparing catalysts to meso–macro-porous monolithic structure is a promising way for the miniaturization of CO removing reactor.

Meso–macroporous alumina supported CuO–CeO2 catalysts were prepared by citrate, urea combustion and impregnation methods. The effect of loading methods on the microstructure of the catalysts, the interaction between copper and ceria and the catalytic performance for preferential oxidation of CO in hydrogen-rich gases was investigated. The prepared monolithic catalysts were characterized by using techniques of N2 adsorption and desorption, SEM, XRD, HRTEM and TPR. The results showed that the loading methods markedly influenced the catalyst structure and the catalytic performance. The citrate and urea combustion methods favored the formation of the interaction between copper and ceria. Compared with the urea combustion method, the citrate method led to smaller ceria particles on the alumina support. The meso–macroporous monolithic catalysts prepared by the citrate method maintained the structural characteristics of the highly active CuO–CeO2 catalysts, and showed good catalytic performance in CO preferential oxidation in the simulated reformate gases containing water and CO2.

LaFeyNi1−yO3 perovskite-type oxide supported highly dispersed NiO catalysts were prepared by one-step citric-complexing method, and applied to the steam reforming of ethanol for hydrogen production. NiO/LaFeO3 prepared by impregnation was also presented for comparison. The XRD and TEM results indicate that one-step citric-complexing method is a simple as well as an effective way for producing well-dispersed NiO particles supported on perovskite oxides. The dispersive NiO particles tend to interact with the perovskite oxide and partially incorporate into the perovskite structure, leading to the formation of LaFeyNi1−yO3 and some resultantly separated Fe ions onto the perovskite surface. The smaller the NiO particles are, the easier the incorporation is. The catalystic performance tests showed that the high activities of NiO/LaFeyNi1−yO3 were attributed to the metallic Ni with high dispersion. The CH4 selectivity was sensitive to the particle sizes of supported Ni, and the smaller nickel particles favor the lower amount of methane formed. Characterizations of used catalysts indicated that the sintering of nickel particles was not significant even at the high reaction temperature. The LaFeyNi1−yO3 supported nickel catalysts exhibited very good carbon deposition resistance, which could be ascribed to the highly dispersed Ni particles and the formation of oxygen vacancies in LaFeyNi1−yO3 due to the partial substitution of Ni ions for Fe ions.

The perovskite type oxides (PTO) supported Ni catalysts were prepared by one step citrate complexing method and were applied to steam reforming of ethanol (SRE). The catalysts were characterized by X-ray diffraction (XRD), oxygen temperature-programmed desorption (O2-TPD), temperature programmed reduction (TPR), thermal analysis (TG), mass spectrometer (MS), physical adsorption for specific surface areas and hydrogen chemical adsorption for metal surface areas. The perovskite oxide without substitution is LaFe1−yNiyO3. For the samples substituted by Sr or Ca, as indicated by the XRD results, the calcium and strontium were successfully introduced into the La site of the LaFe1−yNiyO3. The Ca substitution in LaFeyNi1−yO3 perovskite leads to the enrichment of oxygen vacancies, and some of released oxygen species is resulted from the reduction of the Fe4+ into Fe3+ in the perovskite. Although the enrichment of oxygen vacancies was also observed for the samples with Sr substitution, the insertion of Sr into the perovskite lowers the dispersion of metallic Ni, leading to a poor SRE activity. The correlation between the oxygen vacancies and the stability for SRE indicates that the surface oxygen vacancies and the promoted bulk oxygen species, as the results of the La site substitution, restrain the carbon formation and facilitate the carbon elimination. The surface oxygen vacancies as well as lattice oxygen vacancies are beneficial for the reaction between water and hydrocarbon species on the catalyst surface, reducing carbon containing intermediates and accelerating eliminating reaction of the deposited carbon. In sum, the A site doped perovskite La1−xCaxFe1−yNiyO3 supported nickel catalysts exhibit very good stability for SRE, due to the surface and bulk oxygen vacancies.

Macro-porous monolithic γ-Al2O3 was prepared by using macro-porous polystyrene monolith foam as the template and alumina sol as the precursor. Platinum and potassium were loaded on the support by impregnation method. TG, XRD, N2 adsorption–desorption, SEM, TEM, and TPR techniques were used for catalysts characterization, and the catalytic performance of macro-porous monolithic Pt/γ-Al2O3 and K–Pt/γ-Al2O3 catalysts were tested in hydrogen-rich stream for CO preferential oxidation (CO-PROX). SEM images show that the macropores in the macro-porous monolithic γ-Al2O3 are interconnected with the pore size in the range of 10 to 50 μm, and the monoliths possess hierarchical macro-meso(micro)-porous structure. The macro-porous monolithic catalysts, although they are less active intrinsically than the particle ones, exhibit higher CO conversion and higher O2 to CO oxidation selectivity than particle catalysts at high reaction temperatures, which is proposed to be owing to its hierarchical macro-meso(micro) -porous structure. Adding potassium lead to marked improvement of the catalytic performance, owing to intrinsic activity and platinum dispersion increase resulted from K-doping. CO in hydrogen-rich gases can be removed to 10 ppm over monolithic K–Pt/γ-Al2O3 by CO-PROX.

In this work, a series of Ni/CexTi1−xO2 catalysts were prepared by an impregnation-co-precipitation method and the influences of Ce/Ti ratios on the catalytic performance and carbon deposition were investigated for H2 production by steam reforming of ethanol (SRE). The structural properties of the catalysts were characterized by N2 adsorption, X-ray diffraction, TPR and TG–DTA techniques. The results showed that the catalytic activities and coking resistant behaviors were affected by the structural properties in Ni/CexTi1−xO2 catalysts. Ni species mainly existed in the form of NiTiO3 in the NiO/CexTi1−xO2 catalysts before reduction. Metal nickel produced after reduction from NiTiO3 was highly dispersed, which was the key active component. The catalysts were very active for SRE and exhibited good anti-sintering ability. The formation of Ce–O–Ti solid solution improved redox capability of CeO2. Both high dispersion of Ni0 reduced from NiTiO3 and the formation of Ce–O–Ti solid solution were beneficial for the catalyst performance in Ni/CexTi1−xO2 catalyst.

This work describes a new technique, sol-pyrolysis method, for depositing CuO–CeO2on FeCrAl honeycomb supports. The monolithic catalysts prepared by the method presented good adhesion stability in ultrasonic and thermal shock tests. The principle of the deposition and the role of the support were studied and analyzed by SEM, XRD, TG-DTA, TPR and XPS techniques. The results showed that the active components adhered to the support via three stages. High surface energy of the crystal nuclei and the interaction between the active components and the support promoted adhesion stability. Moreover, the presence of the support influenced distribution and interaction of the active components, but had no obvious effect on catalytic performance. The CuO–CeO2/Al2O3/FeCrAl monolithic catalysts were applied for the preferential oxidation of carbon monoxide in rich-hydrogen gases and revealed high activity and good selectivity under the presence of 15%CO2 and 10%H2O.

Co3O4-CeO2 catalysts prepared by the co-precipitation method have been studied for the preferential oxidation of carbon monoxide in hydrogen. Effects of the cobalt contents and calcination temperature on Co3O4-CeO2 were investigated, and the Co3O4-CeO2 catalyst containing 80 wt.% Co3O4 calcined at 350°C exhibited the highest activity and good selectivity. The influence of the components of the feeding gas (H2, CO2 and H2O) on the preferential oxidation of carbon monoxide had also been tested. The tested results showed that the negative effect of H2 was much weaker than that of H2O and CO2.

Monolithic macroporous Pt/CeO2/Al2O3 catalysts were prepared using concentrated emulsions synthesis route, and the obtained samples were characterized with SEM, TG, TEM, XRD and TPR techniques. These monolithic catalysts were applied to water gas shift (WGS) reaction in reformed gases. The SEM and TEM results indicated that the monoliths possessed macroporosity, and that the platinum particles homogeneously dispersed on the supports with the particle size in the range of 1–2 nm. The reducibility of the catalysts was characterized by TPR method, and it was shown that the monolithic PtOx/CeO2/Al2O3 exhibited the similar reducibility property to that of the particle PtOx/CeO2 reported in literatures. The CO conversion over the monolithic catalysts is higher than that over micro-reactor catalysts for WGS reaction in the reformed gases conditions, indicating that the monolithic macroporous catalysts is a potential new route for miniaturization of WGS reactor.

Three-dimensionally ordered macro-porous (3DOM) Pt/TiO2 catalysts were prepared by template and impregnation methods, and the resultant samples were characterized by using TG-DTA, XRD, SEM, TEM, and TPR techniques. The catalytic performance for water-gas shift (WGS) reaction was tested, and the influences of some conditions, such as reduction temperature of catalysts, the amount of Pt loadings and space velocity on catalytic performance were investigated. It was shown that Pt particles were homogeneously dispersed on 3DOM TiO2. The reduction of TiO2 surface was important for the catalytic performance. The activity test results showed that the 3DOM Pt/TiO2 catalysts exhibited very good catalytic performance for WGS reaction even at high space velocity, which was owing to the better mass transfer of 3DOM porous structure besides the high intrinsic activity of Pt/TiO2.

•Structures of Cu@Co and Co@Cu can be developed and controlled.•Cu–Co/La2O3–SiO2 catalysts show good activity for higher alcohols synthesis.•Different performance can be found with different structures of Cu and Co.Meso–macroporous SiO2 supported LaCo0.7Cu0.3O3 were prepared by impregnation method and used as catalysts for higher alcohols synthesis (HAS) from syngas. These catalysts were characterized by using BET, H2-TPR, XRD, SEM, TEM and XPS techniques. By reducing the catalysts, bimetallic nanoparticles with core–shell structure supported on SiO2–La2O3 were made, and the structure of the nano bimetal could be adjusted via controlling the reduction conditions. The supported bimetal with cobalt as the core and copper as the shell favored the alcohols synthesis, while the bimetal with copper as the core and cobalt as the shell generated more hydrocarbons. The thus prepared bimetal catalysts exhibited very good catalytic performance for HAS from syngas.Download high-res image (175KB)Download full-size image

•La0.95Ce0.05Co0.7Cu0.3O3/ZrO2 catalyst has showed good activity and high selectivity to ethanol.•After reaction for 1000 h, the catalyst was covered by a membrane-like coating.•Carbon deposition is the main reason for the deactivation of the catalyst.A new scheme was proposed to intensify interactions between copper with cobalt and between CuCo with the promoters, namely, the ions of copper, cobalt, lanthanum and cerium were confined into La0.95Ce0.05Co0.7Cu0.3O3 with perovskite structure and were supported on zirconia. The catalyst was prepared by impregnation method and used for ethanol synthesis (ES) from syngas and was characterized by using XRD, TG, BET, XPS, ICP-MS and TEM techniques. La0.95Ce0.05Co0.7Cu0.3O3/ZrO2 showed very good catalytic performance with selectivity to total alcohols higher than 60% and selectivity to ethanol about 50% in the total alcohols. After reduction, clusters composed of CuCo alloy nanoparticles, ceria and lanthanum oxide was formed and loaded on zirconia. Investigation on the variation of the catalyst structure with reaction time showed that with the reaction going on, the clusters spread over the surface of ZrO2 and at last, all the clusters fused together to form a membrane loaded on the ZrO2 and the whole catalyst was covered by a membrane-like coating formed by Co2C. The characterization results showed that the carbon deposition was the main reason for the deactivation of La0.95Ce0.05Co0.7Cu0.3O3/ZrO2 catalyst. This catalyst design scheme could be extended for preparing a lot of catalyst for many reactions.Figure optionsDownload full-size imageDownload high-quality image (129 K)Download as PowerPoint slide

In this paper, Co3O4/CeO2 catalysts for steam reforming of ethanol (SRE) were prepared by co-precipitation and impregnation methods. The catalysts prepared by co-precipitation were very active and selective for SRE. Over 10%Co3O4/CeO2 catalyst, ethanol conversion was close to 100% and hydrogen selectivity was about 70% at 450 °C. The catalysts were characterized by X-ray diffraction, temperature-programmed reduction (TPR) and BET surface area measurements. The preparation method influenced the interaction between cobalt and CeO2 evidently. The incorporation of Co ions into CeO2 crystal lattice resulted in weaker interaction between cobalt and ceria on catalyst surface. In comparison with catalysts prepared by impregnation, more cobalt ions entered into CeO2 lattice, and resulted in weaker interaction between active phase and ceria on surface of Co3O4/CeO2 prepared by co-precipitation. Thus, cobalt oxides was easier to be reduced to metal cobalt which was the key active component for SRE. Meanwhile, the incorporation of Co ions into CeO2 crystal lattice was beneficial for resistance to carbon deposition.

Meso–macro-porous monolithic Pt–Ni/Al2O3 catalysts with platinum and nickel in interaction and in a highly dispersed state have been successfully prepared, and the obtained catalysts are highly efficient for CO removal from hydrogen rich gases via preferential oxidation; the results show that preparing catalysts to meso–macro-porous monolithic structure is a promising way for the miniaturization of CO removing reactor.