Identification of Reaction Pathways and Kinetic Modeling of Olefin Interconversion over an H-ZSM-5 Catalyst

Abstract

Kinetic investigations with a commercial H-ZSM-5 catalyst were performed to enable the modeling of the interconversion reactions of olefins in a temperature range from 420 to 490 °C. Different olefin feedstocks ranging from C2 up to C7 were investigated using a Berty-type reactor. Additional mixed olefin feedstock experiments were performed to obtain improved information about the bimolecular reaction pathways. The experiments include a wide range of conversions to cover the full range of typical industrial process conditions. The reaction pathways and the rate law approach of olefin cracking were analyzed systematically to identify a suitable and comprehensive model structure. A lumped kinetic model with 11 interconversion reactions based on a Langmuir–Hinshelwood–Hougen–Watson approach is found to be the best trade-off between accuracy and model complexity. The comparison between the model and experiments demonstrates that the kinetic model can predict the olefin behavior with a high accuracy for mixed as well as single olefin feedstock. A detailed kinetic model for the formation of side products has also been derived but will be discussed separately in another publication on hydrogen transfer on H-ZSM-5. Compared to existing kinetic models, the kinetic model proposed in this work shows distinct advantages because of the use of mixed feedstock, the widest range of conversions investigated so far, the use of a gradient-free and isothermal Berty-type reactor, and high-performance online gas chromatography analytics.