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Excessive emission of CO2 into the atmosphere has severely impacted the global ecological environment. Converting CO2 into valuable chemicals and fuels is of great significance for sustainable development. However, low activity and undesirable selectivity often result from the inherent inertness of CO2. Herein, K- or/and Zn-modified Fe-based catalysts were prepared by an incipient-wetness impregnation method for CO2 hydrogenation via a cascade reaction. The results indicate that K species exist as K2O while Zn species exist as ZnFe2O4. In the CO2 hydrogenation pathway, K2O facilitates the adsorption of CO2 and restrains the adsorption of H2, accelerating the transformation of CO2 into C2–C4 olefins rather than paraffins while Zn species promote the dispersion of Fe species, leading to improved activity. Synergistically, a K- and Zn-modified Fe-based catalyst (2Zn–10K–Fe/Al) shows excellent catalytic CO2 hydrogenation activity, achieving a CO2 conversion of 77% which is 1.8 times that (42%) of the unmodified Fe-based catalyst (Fe/Al). Our catalyst also shows a significantly promoted selectivity to C2–C4 olefins of 17% in comparison with the Fe/Al catalyst (0%). It is envisioned that such a binary effect of elements might contribute to the low-cost and industrial production of Fe-based catalysts for selective CO2 conversion. [ABSTRACT FROM AUTHOR]

There has been a rapid rise in interest regarding the advantages of support materials to protect and immobilise molecular catalysts for the carbon dioxide reduction reaction (CO2RR) in order to overcome the weaknesses of many well‐known catalysts in terms of their stability and selectivity. In this Review, the state of the art of different catalyst‐support systems for the CO2RR is discussed with the intention of leading towards standard benchmarking for comparison of such systems across the most relevant supports and immobilisation strategies, taking into account these multiple pertinent metrics, and also enabling clearer consideration of the necessary steps for further progress. The most promising support systems are described, along with a final note on the need for developing more advanced experimental and computational techniques to aid the rational design principles that are prerequisite to prospective industrial upscaling. [ABSTRACT FROM AUTHOR]

Alkylation of benzene with pure propane under flow condition has been investigated on a series of monometal gallium and bimetal gallium-platinum modified H-ZSM-5 zeolites with different acidity. The catalysts have been intensively characterized by XRD, XPS, TPR and IR spectroscopy. The chemical states of Ga and Pt have been studied and correlated with catalytic performances of these materials. The coke deposition on catalysts has been evaluated. It was found that the catalytic activity, product distribution and reaction path depend strongly on zeolite acidity and Pt content. With increasing the Si/Al ratio, the benzene conversion decreases and products distribution changes. Main reaction products for high acidity catalysts (lower Si/Al ratio) are toluene, ethylbenezene (EB) and xylenes, indicating that the cracking of propane is favored over its dehydrogenation. For the samples with low acidity, the formation of cumene and propylbenzenes (PrBz) is enhanced. Bimetal GaPt samples show high catalytic activity and selectivity to cumene. Pt promoted Ga-ZSM-5 catalysts show low concentration of coke like polyolefines and polycondensed aromatics, because platinum has a role of the entrance for hydrogen spillover which prevents or moderates coke deposition. Bimetal GaPt samples could be very efficient catalysts for cumene production from benzene alkylation using propane as alkylating agent. It is established that part of platinum in the bimetal samples is in zero valent state and most probably form big metal particles. [Copyright &y& Elsevier]

Bifunctional catalysts are widely applied for many important reactions as the synergetic effect of two types of active sites remarkably improves catalysis performance. However, their bifunctionality has not been fully exploited since the proximity of bifunctional catalysts is hard to control. Herein, we demonstrate a bifunctional ZSM-5@Al 2 O 3 catalyst with a core-shell structure and a nano-scale proximity by in-situ growth of γ-Al 2 O 3 nanosheets on the surface of ZSM-5 crystals for methanol conversion. The nano-scale proximity endows the catalyst with higher reaction activity and C 2 –C 3 olefins yield (53 %) in comparison to the catalysts with micro-scale proximity (20 %) and millimeter-scale proximity (27 %), which can be attributed to the fluent transport of the reaction intermediates between two types of active sites. This strategy for constructing bifunctional catalysts with nano-scale proximity is conducive to understanding the relationship between proximity and catalytic performance in methanol conversion. [Display omitted] • Bifunctional ZSM-5@Al 2 O 3 catalysts with core-shell structure were synthesized. • The proximity of dual-active sites was precisely controlled. • The nano-scale proximity enabled catalysts with superb performance. [ABSTRACT FROM AUTHOR]

Abstract: Materials, consisting of H3+ x PMo12− x V x O40 heteropolyacids (HPAs) with x =0–3, supported on a HMS mesoporous pure-silica molecular sieve, have been prepared by means of dry impregnation method and characterized by elemental analysis, X-ray diffraction, transmission and diffuse reflectance (DR) FT-IR, Raman and X-ray photoelectron spectroscopies, nitrogen physisorption and thermal analysis (TG–DTA). The HPA/HMS compositions with HPA loadings from 10 to 50wt.% display uniformly sized mesopores. HPA retains the Keggin structure on the HMS surface and forms finely dispersed HPA species over the whole range of HPA loadings, crystal phases being absent even at 50wt.%. Results demonstrate that HPA/HMS exhibit a higher catalytic activity than bulk heteropolyacids in propene oxidation by molecular oxygen. Furthermore, the supported species allow for an enhanced oxidation catalytic activity (formation of acrolein, acetaldehyde and acetic acid) compared to the mother catalysts. The catalytic performance exhibited by H3+ x PMo12− x V x O40/HMS catalysts was attributed to the fine dispersion of H3+ x PMo12− x V x O40 species on the HMS mesoporous material via physical adsorption. The HPA/HMS systems, with strong acid sites, high redox power and a regular mesoporous distribution, are promising catalysts for the oxidative reactions. [Copyright &y& Elsevier]

Abstract: The wet impregnation of ammonium heptamolybdate onto silica–alumina is used to prepare MoO3/SiO2–Al2O3 heterogeneous metathesis catalysts. The preparation is inspected in details in conjunction with physico-chemical characterization tools with the aim to identify the parameters that dictate the genesis of active and inactive metathesis species. The effects of the MoO3 loading and of the calcination temperature are systematically explored. The samples are characterized by N2-physisorption, ICP-AES, XRD, Raman, 27Al MAS-NMR and XPS and evaluated in the metathesis of propene to butene and ethene. Particular attention is brought to the interaction of the mesoporous silica–alumina support with the active component, to the decomposition of the precursor salt and to the location of the molybdenum oxide phase with respect to the pores of the support. It is shown that the temperature of calcination influences markedly the performances of the catalyst. High temperature treatments are necessary to decompose efficiently the Mo salt precursor. In the metathesis of propylene, the performances are levelling off when the MoO3 loading is increased above ∼8wt.%. This effect is correlated to the build up of MoO3 crystals and of Al2(MoO4)3 at relatively high loading. [Copyright &y& Elsevier]

Abstract: Biofuel production from vegetable oil is potentially a good alternative to conventional fossil derived fuels. Moreover, liquid biofuel offers many environmental benefits since it is free from nitrogen and sulfur compounds. Biofuel can be obtained from biomass (e.g. pyrolysis, gasification) and agricultural sources such as vegetable oil, vegetable oil sludge, rubber seed oil, and soybean oil. One of the most promising sources of biofuel is vegetable oil sludge. This waste is a major byproduct of vegetable oil factories. It consists of triglycerides (61%), free fatty acid (37%) and impurities (2%). The hydrocarbon chains of triglycerides and free fatty acid are mainly made up of C16 (30%) and C18 (36%) hydrocarbons. The others consist of C12–C17 hydrocarbon chains. Transesterification can help in converting vegetable oil sludge into biofuel. The disadvantage of this method is that a large amount of methanol is required. The alternative method for this conversion is catalytic cracking. The objective of this research is to evaluate and compare the pyrolysis process with cracking catalytic reaction of vegetable oil sludge by Micro-activity test MAT 5000 of Zeton-Canada. A ZSM-5/MCM-41 multiporous composite (MC-ZSM-5/MCM-41), was successfully synthesized using silica source extracted from rice husk. The material has the MCM-41 mesoporous structure, and its wall is constructed by ZSM-5 nanozeolite crystals. The porous system of the material includes pores of the following sizes: 5Å (ZSM-5 zeolite), 40Å (MCM-41 mesoporous material), and another porous system whose diameter is in the range of 100–500Å (mesoporous system) formed by the burning of organic compounds that remain in the material during the calcination process. This pore system contributes to an increase in the catalytic performance of synthesized material. The results of vegetable oil sludge cracking reaction show that the product consists of fractions such as dry gas, liquefied petroleum gas (LPG), gasoline, light cycle oil (LCO), and (heavy cycle oil) HCO, which are similar to those of petroleum cracking process. MC-ZSM-5/MCM-41 catalyst is efficient in the catalytic cracking reaction of vegetable oil sludge as it has higher conversion and selectivity for LPG and gasoline products in comparison to the pyrolysis process. Product distribution (% of oil feed) of cracking reaction over MC-ZSM-5/MCM-41 is coke (3.4), total dry gas (7.0), LPG (31.1), gasoline (42.4), LCO (8.9), HCO (7.2); and that of pyrolysis are coke (19.0), total dry gas (9.3), LPG (16.9), gasoline (28.8), LCO (13.7), and HCO (12.3). These results have indicated a new way to use agricultural waste such as rice husk for the production of promising catalysts and the processing of vegetable oil sludge to obtain biofuel. [Copyright &y& Elsevier]

Abstract: Mesoporous particles and 1D nanorods of cerium oxides have been prepared by modifying the hydrothermal route of a surfactant-assisted controllable synthesis. Mesoporous cerias were obtained in a sealed glass vessel under continuous stirring, while ceria nanorods were obtained in a Teflon-lined autoclave without stirring. The mesoporous cerias did not show long-range mesoscopic organization, exhibiting a broad mesopore size distribution in the region 8–15nm. A BET surface area of 100m2/g with a total pore volume of 0.33cm3/g is obtained for as-synthesized mesoporous ceria. The ceria nanorods exhibit a cubic crystalline structure after calcination, having the lengths in the range of 150–300nm and diameters in the range of 10–25nm. The growth direction of ceria nanorods is along [110]. A surface area of above 50m2/g is obtained in the calcined nanorods. These synthesized ceria materials were used as supports of nano-sized gold catalysts, prepared by deposition–precipitation method. Their catalytic activity was evaluated by the low-temperature water-gas shift reaction. The gold/mesoporous ceria catalytic system exhibited higher catalytic activity than gold/ceria nanorods. It is revealed that the mesoporous and nanostructured cerias are of much interest as potential supports for gold-based catalysts that are effective for low-temperature water-gas shift reaction. [Copyright &y& Elsevier]

Abstract: New gold catalytic system prepared on ceria-modified mesoporous titania (CeMTi) used as water-gas shift (WGS) reaction catalyst is reported. Mesoporous titania (MTi) was synthesized using surfactant templating method through a neutral [C13(EO)6–Ti(OC3H7)4] assembly pathway. Ceria modifying additive was deposited on MTi by deposition precipitation (DP) method. Gold-based catalysts with different gold content (1–5wt.%) were synthesized by DP of gold hydroxide on mixed metal oxide support. The supports and the catalysts were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N2 adsorption analysis and temperature-programmed reduction (TPR). The catalytic behavior of the gold-based catalysts was evaluated in WGS reaction in a wide temperature range (140–300°C) and at different space velocities and H2O/CO ratios. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity of the new gold/ceria-modified mesoporous titania catalysts was compared with that of gold catalysts supported on simple oxides CeO2 and mesoporous TiO2, as well as gold/ceria-modified titania and reference catalyst Au/TiO2 type A (World Gold Council). A high degree of synergistic interaction between ceria and mesoporous titania and a positive modification of structural and catalytic properties by ceria has been achieved. It is clearly revealed that the ceria-modified mesoporous titania is of much interest as potential support for gold-based catalyst. The Au/ceria-modified mesoporous titania catalytic system is found to be efficient catalyst for WGSR. [Copyright &y& Elsevier]

Single-crystalline α-Mn2O3 nanorods with diameters 60–130 nm and lengths ranging 0.7–2.5 μm, as well as single-crystalline Mn3O4 particles, have been prepared through a simple and facile preparation method of ammonia-hydrothermal treatment of commercial granular/bulky MnO2, which involves no catalysts or templates and is capable for large-scale preparation. [Copyright &y& Elsevier]

Review: 584 refs. [ABSTRACT FROM AUTHOR]