Selective toluene ethylation in supercritical CO2 using chemical liquid deposition modified HZSM-5 pellets

Pellets consisting of the para-selective HZSM-5 crystals prepared by the chemical liquid deposition (CLD) with tetraethyl orthosilicate (TEOS) were used as the catalyst for alkylation of toluene with ethylene in supercritical carbon dioxide. The pellets were formed by compressing the CLD modified HZSM-5 crystals with and without addition of the binder alumina. When the binder was used, the CLD was applied again right after the compression. For the addition of 0.1 ml of TEOS per gram of pellet, p-ethyltoluene yield and selectivity were found to be sufficiently close to those using the modified crystals and the compressed pellets without containing the binder. The alkylation was carried out in a tubular reactor packed with the prepared HZSM-5 pellets. From a study of the operating variables including temperature, pressure, weight hourly space velocity of toluene, and molar ratio of toluene to ethylene, the highest yield and selectivity of p-ethyltoluene were determined as 70 and 97%, respectively, at a temperature of 623 K, a pressure of 13.1 MPa, a weight hourly space velocity of 5.0 (g of toluene)/(g of catalyst)/h and a molar ratio of toluene to ethylene of 5. The obtained results indicate a pronounced shape-screening effect of the prepared HZSM-5 pellets and an applicability of using supercritical CO2 as the carrier.