Kinetic modeling and thermodynamic analysis of toluene disproportionation reaction over ZSM-5 based catalysts

The aim of this work was to carry out an experimental study along with kinetic and thermodynamic analysis for the toluene disproportionation reaction under actual industrial operating conditions. The toluene disproportionation reaction was carried out under pressurized hydrogen and over three different ZSM-5 based catalysts, namely, ZSM-5, 3%Mo on ZSM-5, and 3%Mo on ZSM-5/Mordenite. The influence of reaction temperature and catalyst composition on conversion and product distribution was investigated. A network of reversible reactions and elementary rate laws reflecting the product distribution, including xylene isomers and other products, were proposed and validated using the obtained experimental data. The thermodynamic parameters were estimated using a chemical process simulation package (Aspen HYSYS), while numerical and statistical methods were used to estimate the kinetic parameters. A notable agreement between the model predictions and the experimental data was obtained. The Mo-impregnated, mordenite-containing catalyst (3%Mo on ZSM-5/Mordenite) was found to be the most active catalyst, presumably due to the additional metallic-active sites that were readily accessible through the mordenite's large pores compared to the plain ZSM-5 catalyst. In addition, the most active catalyst was found to have the lowest activation energies and lead to conversions that were limited thermodynamically.