Kinetic Study of Xylene Isomerization Reaction and Ethylbenzene Conversion on Mo-Pt@ZSM5 Catalyst

This research theoretically studies xylene isomerization on the Mo-Pt@ZSM5 catalyst. The inlet stream composition is similar to the actual current in the petrochemical unit. The empirical data are gas-phase compositions in the temperature range 370 oC to 400 oC in the catalytic reactor. Two suitable kinetic models were proposed for catalytic reactions, one incorporating adsorption terms and the other mass transfer coefficients into the rate equations. The model's predictions are acceptable compared to the laboratory error of about 1%. Using a genetic algorithm, surface adsorption equilibrium constants appearing in the denominator of the first model were evaluated for metaxylene as Km = 0.0012, and for ethylbenzene as Keb = 0.0379. In the second model, the meta and ortho mass transfer coefficients are equal, and βM = 1.514×106 cm3/(gcat.h), and βEB = 6.847×105 cm3/(gcat.h), ​are derived using a genetic algorithm. The rate constants in both models are k3 = 0.0561 molei/(gcat.h), k9 = 0.0285 molei/(gcat.h), and Arrhenius constants are k07 = 1417 molei/(gcat.h), E7 = 35592 J/mol, k011 = 3.156×107 molei/(gcat.h), and E11 = 1.283×105 J/mol. The results show that, as expected, the metaxylene and orthoxylene decrease along the reactor, and the concentration of paraxylene increases. The results of the second model showed that the mass transfer resistance can be ignored for xylenes. But, in the case of ethylbenzene, mass transfer resistance has a greater effect. Therefore, both models have the same precision; however, they provide different information about the adsorption and mass transfer of components.