Nature of activity and selectivity of catalysts based on dealuminized zeolites Communication 2. Activity of dealuminized Y zeolites and mordenite in cracking straight-chain hydrocarbons

Abstract

1. Cracking rates of the n-alkanes pentane, hexane, decane, and hexadecane on the H forms of dealuminized Y zeolite and mordenite have been measured, and also the heats of adsorption of ammonia and the diffusivity of 2,2,4-trimethylpentane. 2. As the degree of dealuminization is increased, the zeolite activity passes through a maximum. In the cracking of alkanes with different chain lengths on the faujasites, the optimal degree of dealuminization is the same for all of the alkanes. In the case of the mordenites, the lower the molecular weight of the alkane, the greater is the degree of dealuminization required to obtain an effective cracking catalyst. 3. Diffusional factors do not play a decisive role, and the activity of the zeolites, both in the primary fragmentation reaction and in the secondary hydrogen distribution reaction, is determined by the changes in their acidity upon dealuminization.