ESR Investigation of Active Sites in Ru/CeO2 Solids

Abstract

Two Ru/CeO 2 catalysts with Ru loadings of 1.65 and 5 wt% were prepared by wet impregnation. The adsorption of propylene or toluene led to two different ESR signals corresponding to two different catalytic sites. These two sites are present among the well dispersed ruthenium oxide species that reduce at *74°C. One site is un-reactive unless activated to remove adsorbed water while the second site is reactive at room temperature. Both sites are easily regenerated under oxidative atmosphere at 200°C. These two sites are optimally obtained for calcination temperatures in the 500-600°C interval and a Ru loading of 1.65 wt%. For Ru5Ce, the same reactive sites are present along with agglomerated ruthenium oxide species that are less reactive in oxidation reactions. Graphical Abstract2500 2750 3000 3250 3500 3750 4000 S 3

Surface basicity mediated rapid and selective adsorptive removal of Congo red over nanocrystalline mesoporous CeO2

“…CeO2 is one of the most widely employed semiconducting metal oxide in the field of catalysis and environmental remediation [1][2][3][4][5] , mainly due to (i) its high abundance and low cost 6 , (ii) wide band-gap, non-toxicity and high stability 7 , (iii) tendency for oxygen uptake into the lattice and the possibility of reversible transition redox system between Ce +3 and Ce +4 8, 9 and (iv) the chance of formation of solid solutions with other oxides 6 . CeO2 has already emerged as a promising choice for a wide range of catalytic processes such as; promoter in threeway catalysts in automobiles 10,11 , solid oxide fuel cells 12,13 , reforming of hydrocarbons [14][15][16] , water gas shift reaction [17][18][19] , CO oxidation [20][21][22] , catalytic combustion of volatile organic compounds (VOC's) [23][24][25][26] , hydrogenation of alkynes 27,28 , syngas conversion to alcohols 29 , thermochemical water splitting 30,31 , photocatalysis [32][33][34] etc. Nevertheless, efforts to further improve its catalytic efficiency are still in progress 35 .…”