The role of carbon deposition in the gas phase transesterification of dimethylcarbonate and phenol over TiO2/SiO2 catalyst

Abstract

The transesterification of dimethylcarbonate and phenol has been studied in a continuous gas phase reactor over TiO2 supported on SiO2. Initially, only undesired side reaction products were formed at high rates. After several hours of induction period, desired methylphenylcarbonate was formed selectively at a reduced, bur stable rates. This dramatic change in selectivity during the initial period of the reaction was caused by carbon deposition on the Catalyst that deactivated selectively the highly reactive catalytic sites responsible for the side reactions. Temperature-programmed reactions of dimethylcarbonate and phenol by themselves or together over TiO2/SiO2 clarified the reaction pathways of the transesterification, especially during the initial period the reaction. The induction period was greatly shortened when the catalyst was pretreated with dimethylcarbonate at the reaction temperature. X-ray photoelectron spectroscopy, X-ray diffraction and N-2 adsorption were employed for catalyst characterization. (C) 2000 Elsevier Science B,V. All rights reserved.