Catalytic activity and selectivity of NaOH-doped γ-aluminas. Dehydration and dehydrogenation of 3-pentanol

Abstract

The catalytic activity of the γ-alumina surface has been investigated using infra-red spectroscopy and interpreted in terms of strong and weak Brønsted-acid sites and Lewis-acid sites. Doping of the γ-alumina with NaOH was used to eliminate Brønsted-acid sites. The influence of the two types of sites upon catalytic activity and selectivity was shown with studies of the simultaneous dehydration and dehydrogenation of 3-pentanol on pure γ-alumina or on several doped aluminas of varying NaOH content. Although the fractional activity of the weak Brønsted-acid sites is greater than that for the Lewis-acid sites, the differences in catalytic behaviour are considerably larger and are attributed to reduced accessibility of the Lewis-acid sites. The selectivity exhibited towards the two reactions was shifted from dehydration to dehydrogenation by eliminating Brønsted-acid sites.