Synergy between shape selective and non-shape selective bifunctional zeolites modelled via the Single-Event MicroKinetic (SEMK) methodology

Abstract

In decane hydroisomerization the synergy effect between a non-shape selective Pt/NaHY and a shape selective Pt/H-ZSM-22 catalyst leads to enhanced total isomer yields. In a physical mixture of the two catalysts, monobranched isomers are formed through hydroconversion on Pt/H-ZSM-22. The latter undergo further isomerization on Pt/NaH-Y catalyst with mild activity to produce multibranched isomers while simultaneously suppressing cracked product formation. A Single-Event MicroKinetic (SEMK) model, obtained through addition of the models for the individual catalysts, is used to simulate the synergy effect. With an estimation of only the “catalyst descriptor” values for the individual catalysts using the data on the pure catalysts, the conversion and selectivity associated with the synergy effect can be well simulated without further adjustment of any other model parameters. The Pt/H-ZSM-22 catalyst used in this work is more active than Pt/NaH-Y for n-decane hydroconversion which is reflected in the protonation enthalpies for secondary carbenium ion formation, i.e., −62.9 kJ mol −1 on ZSM-22 compared to −54.3 on Y. According to the model, approximately 50% of the n-decane is transformed into 2-methyl nonane on Pt/H-ZSM-22 before conversion to multibranched isomers starts taking place on Pt/NaH-Y.