Studies on the Selectivity Between O-Alkylation versus C-Alkylation of Phenol with Cyclohexene Using Nanocrystalline Beta Zeolite

Abstract

The alkylation of phenol with cyclohexene using acid catalysts results in the generation of both O-alkylated and C-alkylated products, all of which hold significant utility across diverse industries. Cyclohexyl phenyl ether is utilized as a fragrant compound in perfumery applications. Through dehydrogenation, it transforms into diphenyl oxide (DPO), a significant chemical intermediate. In the current research nanocrystalline zeolite Beta was synthesised by vacuum-concentration coupled hydrothermal technique using tetraethyllammonium hydroxide templates and the catalytic performance was analysed for the alkylation of phenol with cyclohexene. Various parameters like reactant mole ratio, catalyst amount and temperature were assessed for better conversion of cyclohexene and desired product selectivity. The findings demonstrate that the catalyst effectively improves the conversion of cyclohexene while enhancing the selectivity of desired products. High efficiency of the catalyst is attributed due to its favourable structural characteristics, including its nano sized particles with open pore structure. The catalyst displayed up to ~96% conversion of cyclohexene ~55% selectivity towards the major product, cyclohexyl phenyl ether at optimal reaction conditions. Activation energy of the phenol alkylation with cyclohexene was calculated from the measured rate constant at various temperatures and was found to be 22.9 kJ/mol. There is negligible decline in percent conversion after reusing the catalyst for up to five runs.