Primary Products in Hydrocarbon Cracking over Solid Acidic Catalysts under Very Mild Conditions: Relation to Cracking Mechanism

• Published in: Journal of catalysis Vol. 180; no. 1; pp. 101 - 105
• Main Author: Kissin, Yury V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15-11-1998; Elsevier
• Subjects: Catalysis; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Reaction intermediate; Catalytic reaction; Hydrocarbon; Mild operating conditions; Isomerization; Zeolite; Experimental study; Bronsted site; Molecular sieve; Heterogeneous catalysis; Gas chromatography; Olefin; Formation mechanism; Catalyst
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1006/jcat.1998.2254

This note analyzes primary products (reaction products with the same carbon atom numbers as in feeds) produced in cracking reactions of several C7–C9isoalkanes over zeolite-based catalysts under very mild conditions, at 150–250°C and at high [feed] : [catalyst] ratios, and discusses formation mechanisms of these products. Primary products from methyl-substituted alkanes at low temperatures are predominantly isoolefins with the same skeleton structures as in feed alkanes. A chemical mechanism which was earlier proposed to describe formation of light cracked products from isoalkanes [J. Catal.163, 50–62 (1996)] is well suited to describe the formation of the primary cracked products as well. This mechanism includes a reaction between an isoalkane and the Brønsted center on the catalyst surface with the formation of a transient hydrosiloxonium ion Si–O+(H)–C. The ion undergoes a hydrogen atom abstraction from the C–H bond in the β-position to O+with the formation of an olefin molecule which, in turn, rapidly isomerizes via the carbocationic mechanism.