Liquid-phase alkylation of benzene with octenes over Y zeolites: Kinetic modeling including acidity descriptors

A fundamental microkinetic model is presented for the alkylation of benzene with octenes in liquid phase over Y zeolites with Si/Al ratios 5.8, 13, and 30. The model describes simultaneously the olefin isomerization and benzene alkylation reactions on the fresh catalysts, that is, in the absence of coke formation. The reaction mechanism considers adsorbed octenes reacting with benzene from the liquid phase. Protonation of phenyloctanes are considered quasi-equilibrated. Protonation of olefins and surface alkylations are considered as non-quasi-equilibrated. Activation energies of 46 kJ mol−1 and 70 kJ mol−1 are obtained for olefin protonation and surface alkylation, respectively. Standard protonation enthalpies of −33 kJ mol−1 and −92 kJ mol−1 are obtained for the protonation of 1-octene and 2-phenyloctane, respectively. Introduction of two catalyst descriptors allows to describe the influence of the acid properties of the Y zeolites on conversion and product yields. The concentration of acid sites is obtained from ammonia TPD. The change in standard protonation enthalpy relative to a reference Y zeolite, Δ(ΔHpro), accounts for the effect of the zeolite’s average acid strength on the stability of the intermediates and the activation energies and is estimated by regression to experimental data. For the three Y zeolites, a variation in standard protonation enthalpy of 7 kJ mol−1 is found.

Liquid-phase alkylation of benzene with octenes over HY zeolites can be described by a kinetic model based on an Eley–Rideal type mechanism, carbenium-ion chemistry, and the concept of multiple non-quasi-equilibrated steps.Figure optionsDownload high-quality image (167 K)Download as PowerPoint slideHighlights
► Olefin isomerization and benzene alkylation paths are described simultaneously.
► Model describes quantitatively the influence of changes in zeolite acid properties.
► Zeolite average acid strength influences concentration of surface carbenium ions.