Xylene isomerization side reactions over Beta zeolite: Disproportionation and transalkylation of C-8 aromatics and toluene

An experimental and parametric behavior study of disproportionation and transalkylation between C-8 aromatics and toluene were carried out over mono-functional acid Beta zeolite with a SiO2/Al2O3 ratio of 35(BEA35). The experiments were performed in liquid phase under the following conditions: 453, 473, and 493 K and 2.1 MPa. Ethylbenzene disproportionation and ethylbenzene-toluene transalkylation were identified as the main side reactions; therefore, the kinetics of both reactions were estimated. Both reactions were verified to be second order with no signs of competition for the adsorption sites under the studied conditions. Additionally, ethyl benzene disproportionation and ethylbenzene-toluene transalkylation, undergo through a deethylation-ethylation mechanism, the activation energies were 66 and 57 kJ/mol respectively. Furthermore, the existence of parallel reactions, as well as the feed concentration, showed no effect on the p-diethylbenzene selectivity. Selectivity towards the para-isomer was observed only at very low conversions. Finally, an analytical solution was developed for the system showing excellent agreement with the experimental data.