An Evaluation of Published Kinetic Models. for Vapor Phase Methanol Conversion to Dimethyl Ether over the H-ZSM-5 Catalyst

The published kinetic models for methanol etherification over ZSM-5 zeolite were evaluated against our own experimental data. The process was investigated over a synthesized H-ZSM-5 zeolite using a laboratory fixed-bed reactor. The experiments were carried out at atmospheric pressure, temperatures of 170-270 degrees C, methanol feed concentrations up to 15 mol %, and gas phase velocity (WHSV) values in the range of 15-48 h(-1). The results showed a decrease of methanol conversion with respect to feed methanol concentration, with the single reaction product obtained in significant concentrations being dimethyl ether (no secondary products were observed in significant concentrations). The methanol conversion measurements were compared with theoretical predictions based on the main kinetic models published for methanol etherification over ZSM-5 zeolites with different acidities. As none of the published models fitted satisfactorily with our experimental data, we re-estimated the parameters of the tested models and applied a discrimination procedure in order to identify the most suitable one. The best quality of the fit was obtained by using an LH kinetic model based on the associative surface reaction mechanism. The adequacy of this kinetic model was confirmed by statistical and thermodynamic consistency criteria.