Catalytic properties of amorphous Silica-alumina prepared using dicarboxylic and tricarboxylic acids as matrix in catalytic cracking of n-Dodecane

Abstract

Amorphous silica-aluminas were prepared by the sol-gel method using carboxylic acids, malic acid (MA), succinic acid and citric acid, and the reactivity for catalytic cracking was investigated. When the ratio of MA/TEOS (tetraethoxysilane) increased, surface area, pore volume and pore diameter increased and mesopores were formed. The maximum total conversions of n-dodecane were around 30% with the single amorphous silica-alumina. In contrast, the total conversion reached 91% with the single beta-zeolite. To investigate the reactivity of amorphous silica-alumina as a matrix, mixed catalysts consisting of zeolite, amorphous silica-alumina and binder (alumina sol) were prepared. The product distribution changed compared with the single zeolite or silica-alumina, and comparable activity tothat of zeolite was obtained although the mixed catalysts included only 1/4 of zeolite. Mixed catalysts using amorphous silica-alumina with mesopores (MA122-5) exhibited higher ratio of multibranched to single-branched products in the gasoline fraction (C5-C11) than single zeolite. The effect of the addition of 1-dodecene and 1-methylnaphthalene was alsoinvestigated.