Abstract
Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (i.e. SiO2, γ-Al2O3, TiO2, and ZrO2) were prepared by the impregnation method. The catalysts were characterized by N2 adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb2O3 and also the influence of the nature of the support were investigated. SiO2 supported Pd catalyst exhibited the highest surface area (192.6 m2/g) and pore volume (0.542 cm3/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO2, ZrO2, CeO2, and Nb2O5.
Highlights
The catalysis is considered one of the most important research areas in chemistry, related fields, industry and technology which provides new material and conditions to reduce the cost, as well as time and besides that looking for a new and alternative solution for treatment of wastes, catalytic materials have massive contribution to the environmental impact which influence in cleaning the air from toxic gases such as CO and NOx, water wastes, etc.At the end of 1970s Tauster and coworkers are connected to the strong metal-support interaction (SMSI), they perceived that the adsorption of H2 and CO to descend after some treatment of oxide-supported noble metal catalysts, most apparently for Pt supported on TiO2 [1] [2]
Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation
The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO2, ZrO2, CeO2, and Nb2O5
Summary
At the end of 1970s Tauster and coworkers are connected to the strong metal-support interaction (SMSI), they perceived that the adsorption of H2 and CO to descend after some treatment of oxide-supported noble metal catalysts, most apparently for Pt supported on TiO2 [1] [2]. SMSI is sometimes used in a more general sense by including support effects on metal dispersion, spatial distribution, and particle shape. This research effort may be justified in terms of a fundamental understanding of such a special phenomenon, and because of its implications in the design of specific preparation, characterisation, or catalytic applications of the metal/support system exhibiting this effect
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