Industrial & Engineering Chemistry Research, Vol.48, No.21, 9383-9393, 2009
Alkylation of Xylenes with Isopropyl Alcohol over Acidic Clay Supported Catalysts: Efficacy of 20% w/w Cs2.5H0.5PW12O40/K-10 Clay
The alkylation of xylenes with propylene or isopropyl alcohol (IPA) over solid acid catalysts results in the formation of isopropyl xylenes (dimethyl cumenes). However, the use of propylene as an alkylating agent at very high temperatures leads to coke formation, which results in deactivation of the catalyst. The present work covers evaluation of acidic clay-supported catalysts and sulfated zirconia. A variety of solid acid catalysts such as K-10 clay, sulfated zirconia, Filtrol-24, 20% w/w dodecatungstophosphoric acid (H3PW12O40, DTP) supported oil K-10 clay, and 20% w/w cesium-substituted dodecatungstophosphoric acid (Cs2.5H0.5PW12O40, Cs-DTP) supported oil K-10 clay under much milder conditions. The best catalyst to achieve maximum conversion and selectivity was determined to be 20% w/w Cs-DTP/K-10 clay The reactions were conducted in the liquid phase at relatively low reaction temperatures (160-190 degrees C). The reaction was performed without using any solvent, and the process subscribes to the principles of green chemistry. The catalytic activity has the following order 20% w/w Cs-DTP/K-10 clay (most active) > 20% w/w DTP/K-10 clay > Filtrol-24 > sulfated zirconia > K-10 clay (least active). The desired product could be efficiently obtained, with selectivities up to 95% at all isopropanol conversion of 98% after 2 h over 20% w/w Cs-DTP/K-10 clay. This process call be a replacement for the existing processes that are based on zeolites, where high temperature and pressure are required. A systematic investigation of the effects of various operating parameters wits accomplished and a mathematical model is developed to describe the reaction pathway and validated against experimental results. An overall second-order kinetic equation was used to fit the data, tinder the assumption that all the species are weakly adsorbed oil the catalytic sites.