Pore size independent regioselective cyclohexylation of ethylbenzene

Abstract

Al-MCM-41 (Si/Al = 52 and 105) and Al-MCM-48 (Si/Al = 47 and 102) molecular sieves were synthesised by hydrothermal method. These materials and commercial HY zeolite were characterised by XRD, BET, 27Al MAS-NMR, pyridine adsorbed FT-IR and ICP-AES techniques. The vapour phase cyclohexylation of ethylbenzene (EB) with cyclohexene was carried out between 200 and 400 °C over all the catalysts. The major products were found to be p-cyclohexyl ethylbenzene ( p-CEB) and o-cyclohexyl ethylbenzene ( o-CEB). The activity of the catalysts followed the order Al-MCM-41 (52) > Al-MCM-41 (105) > Al-MCM-48 (47) > Al-MCM-48 (102) > HY. Al-MCM-41 and Al-MCM-48 are more active than HY although the density of acid sites of the former catalysts is less than the latter. This is due to the large pore size of Al-MCM-41 and Al-MCM-48 catalysts that permits simultaneous entry of more reactants into the pores and expulsion of products freely out of the pores. Al-MCM-41 catalysts are more active than Al-MCM-48 catalysts due to more density of acid sites on the channel surface of Al-MCM-41. The selectivity of p-CEB is higher than o-CEB due to less steric hindrance for its formation. The effects of feed ratio and WHSV on ethylbenzene conversion and product selectivities were evaluated in the above reaction.