The Synthesis Of Diethyl Carbonate By Vapor Phase Oxidative Carbonylation Of Ethanol Over Supported CuCl₂-PdCl₂-KCl/AC Catalyst

Diethyl carbonate (DEC) is one of the important carbonate esters and offerswidely prospects of intermediate in organic synthesis as a "environmentally benignchemistry" substitute of toxic phosgene. One promising usage of DEC is found to begasoline and diesel fuel additive as methyl tert-butyl (MTBE) replacement for itscompetitive chemical properties. The synthesis of DEC by vapor phase directoxidative carbonylation of ethanol was evaluated as "green technology" route withmild condition, unharmful byproduct and high atomic economy. It was carried outbased on the system of the CuCl2-PdCl2-KCl/AC loaded catalyst in this paper.The influence of various pre-treatments for activated carbon supports on thecatalytic performance was mainly studied. It increased from a 15.8% conversion ofethanol and STY value of target DEC of 194.3 (g-DEC/(l-cat h)) to about 30% and440 (g-DEC/(l-cat h)). The best molar ratio of Cu/OH was 1. From FTIR, XPS andXRD analysis, the active phase was found to be improved by support pre-treatmentsfor the increased surface oxygen-containing groups, especially C-O bond.The optimal loadings of Cu and K contents were 9wt% and 8.5wt%, respectively.The influence of solvent was also investigated. Methanol solvent made PdCl2 smallerfor dispersion while ammonia solvent restrained side reaction and brought longercatalyst lifetime.The effect of various chlorides based on the Wacker type CuCl2-PdCl2/ACcatalyst as promoters was also evaluated. The significant variety on the catalystactivities was closely related with the KCl promoter. XRD XPS and SEM analysisshowed that KCl was contributed to the transformation to α-Cu2Cl(OH)3 and PdOactive phases. Alkali metal K is in more favor of Schottky lattice vacancy andstrengthens the capture ability for reactant's electron through the empty zone from thecorporative action of Cu and Pd transition elements. The improved DEC synthesisperformance was attributed to the existence of CO as coordinating group for PdO andKCl effect by the reaction mechanism analysis.