Relationship between activation energy and pre-exponential factor normalized by the number of Brønsted acid sites in cracking of short chain alkanes on zeolites

Abstract

The rates of the reaction of C3 to C8 linear and C4 and C5 monomethyl-branched alkanes catalysed by various zeolites (FAU, *BEA, MFI and MOR) were analysed. The pre-exponential factor, normalized by the number of Brønsted acid sites, showed a compensatory change in the activation energy. The lower activation energy gave a lower pre-exponential factor, indicating the compensation effect between the activation energy and entropy. The relationship between the pre-exponential factor and the activation energy was common in the reaction of butane, pentane, hexane, octane and 2-methylbutane over various catalysts, while propane and 2-methylpropane had pre-exponential factors lower than those observed in the reactions of other alkanes.