Hydrogenation over boehmite/γ-Al2O3 catalysts

Abstract

On refluxing in 1 mol dm^–3 sodium acetate solution at 373 K for up to 27 h, the surface of γ-Al₂O₃ is transformed to boehmite, AlOOH. Samples of AlOOH/γ-Al₂O₃ produced on drying are able to adsorb hydrogen dissociatively and catalyse the hydrogenation of pent-1-ene and buta-1,3-diene at and above ambient temperature without further pretreatment. Maxima in activity for isomerisation of pent-1-ene occur after shorter times of acetate treatment than the maxima in hydrogenation activity. The activity of such catalysts is only temporarily diminished by acetylene and carbon monoxide, and is unaffected by the presence of oxygen. However, they are poisoned by HCl, but may be regenerated by the action of steam. Two types of site may be involved in alkene hydrogenation; the first adsorbing hydrogen and initiating spillover to the second type of site where the alkene is adsorbed and hydrogenation occurs. These may be anionic oxygen and Lewis acid sites respectively which may be located at the interface between the boehmite and γ-Al₂O₃ phases.