Alkylation of toluene with isopropyl alcohol catalyzed by Ce-exchanged NaX zeolite

The industrially important cymene synthesis was carried out by toluene isopropylation over cerium-exchanged NaX zeolite. The modification of NaX zeolite by cerium exchange was found to enhance the catalytic activity of the zeolite to a considerable extent. The reactions were carried out in a fixed-bed flow reactor at atmospheric pressure with nitrogen as the carrier gas. The reaction conditions were optimized by varying temperature, reactants mole ratio and space-time. It was observed that in the isopropylation of toluene, the isopropyltoluene fraction contained both para and meta isomers. There was no ortho-cymene in the product stream. Alkylation studies at 433-513 K showed a decrease in p-cymene selectivity with increase in reaction temperature and increased formation of diisopropyl toluene at lower temperature. A systematic and detailed kinetic study was carried out for the alkylation reaction. From the product distribution pattern, a kinetic model for the reactions was proposed by following Langmuir-Hinshelwood approach. The kinetic and adsorption parameters of the rate equation were determined by non-linear regression analysis. The apparent activation energy for the main reaction was found to be 48.12 kJ/mol. (c) 2005 Elsevier B.V. All rights reserved.