Alkylation of toluene with propylene in supercritical carbon dioxide over chemical liquid deposition HZSM-5 pellets

Alkylation of toluene with propylene in supercritical carbon dioxide over the parent and modified HZSM-5 pellets was carried out in a packed bed in this study. The modification was done by adding a mixture Of SiCl4 and hexane to the parent HZSM-5 pellets containing 14% water. The experimental data showed that much more p-cymene could be yielded using the modified HZSM-5 pellets, exhibiting shape-screening character. When the toluene feed and the molar ratio of toluene to propylene in supercritical carbon dioxide were kept the same as that in the gas phase, it was found that 50% more of p-cymene could be generated and the cracking of propylene was significantly reduced under supercritical operations, indicating more efficient operation and more effective utilization of propylene. From a systematic study of the effects of operating variables on p-cymene yield and selectivity for the use of 4 g of the modified HZSM-5 pellets, the most appropriate operating conditions were found to be a temperature of 523 K, a pressure of 11.72 MPa, a weight hourly space velocity of 4.6 (g of toluene)/(g of catalyst)/h, and a molar ratio of toluene to propylene of 7.7. These appropriate conditions were influenced by the reaction mechanism and solubilizing capability of supercritical carbon dioxide toward reactants and products.