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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: 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: 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]