Cracking of cyclohexane by high Si HZSM-5

• Published in: Applied catalysis. A, General General, 2010-03, Vol.375 (2), p.213-221
• Main Authors: Slagtern, Åse, Dahl, Ivar M., Jens, Klaus J., Myrstad, Trond
• Format: Article
• Language: English
• Subjects: Aluminum; Catalysis; Chemistry; Cracking; Cyclohexane; Ethene; Exact sciences and technology; Fracture mechanics; General and physical chemistry; Ion-exchange; Olefins; Reaction kinetics; Selectivity; Silicon; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites; Zeolites: preparations and properties
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2009.12.032

Cracking of cyclohexane has been performed over a HZSM-5 catalyst with Si/Al ratios 28, 85 and 200, in the temperature region 400–650 °C and with partial pressures of cyclohexane up to 2 bar. The cracking kinetics for Si/Al = 200 can be adequately modelled by simple first order kinetics. Olefins and benzene appear to be the primary products from the cracking reaction, while alkanes and higher aromatics behave as secondary products. Combined selectivities of ethene + propene increase with increasing temperature, and more than 60% selectivity can be reached. Under the reaction conditions very rapid equilibration of olefins heavier than ethene is obtained. The addition of hydrogen to the cracking feed has only a small influence on the rate of formation of saturated compounds. Cracking of cyclohexane at a partial pressure of up to 2 bar over HZSM-5 catalysts with Si/Al ratios 28, 85 and 200 in the temperature region 400–650 °C can, at selected conditions, give more than 60% combined ethene/propene selectivity. The cracking kinetics of the Si/Al = 200 catalyst can be adequately modelled by simple first order kinetics. Olefins and benzene appear to be the primary products of the cracking reaction, while alkanes and higher aromatics behave as secondary products. Under the reaction conditions very rapid equilibration of C 2+ olefins is obtained. The addition of hydrogen to the cracking feed has only a small influence on the rate of formation of saturated compounds.