Vapor-phase catalytic reactions of alcohols over bixbyite indium oxide

Vapor-phase catalytic reactions of several alcohols were investigated over In2O3. In2O3 showed stable catalytic activity in the dehydration of terminal diols, such as 1,4-butanediols and 1,5-pentanediol, to produce unsaturated alcohols, such as 3-buten-1-ol and 4-penten-1-ol, respectively, with selectivities higher than 70 mol%. Although the dehydration of 1,3-diols, such as 1,3-propanediol and 1,3-butanediol. also proceeded over In2O3, the catalytic activity decreased with time on stream because of dehydrogenation followed by retro aldol reaction of the resulting dehydrogenated products. in contrast, in the reaction of monoalcohols, such as 1-butanol and 2-octanol, dehydrogenation dominantly proceeded to produce butanal and 2-octanone. respectively. Although In2O3 has cubic bixbyite crystal structure that is the same as those of heavy rare earth oxides, the catalytic activity of In2O3 was similar to that of cubic fluorite CeO2 with redox property, rather than those of heavy rare earth oxides with acid-base property. Redox sites of In2O3 are concluded to be active centers for the dehydration of diols to produce unsaturated alcohols. (C) 2009 Elsevier B.V. All rights reserved.