Product Distribution in Degradation of Polypropylene over Silica-Alumina and CaX Zeolite Catalysts

Abstract

Abstract The composition of degradation products of polypropylene, especially liquid fraction, formed over silica-alumina and CaX zeolite catalysts was investigated extensively. The catalysts gave almost the same product distribution as a function of carbon number at the initial stages of the reaction. The liquid fractions were rich in the same isoalkanes and aromatics as those contained in the gasoline fraction. Most of the isoalkanes were methyl-branched, while the aromatics consisted mainly of those with one or more methyl groups. The catalytic degradations involved extensive aromatization, isomerization and hydrogen transfer as secondary reactions. The difference in catalytic behaviors between silica-alumina and CaX was most remarkable in coke deposition on the catalysts and more deposition on CaX led to greater saturation of the products. The H/C ratio of the products was regarded as a good measure for the degree of coke formation on the catalyst surfaces.