Vapor-phase reactions of catechol with dimethyl carbonate. Part I. O-methylation of catechol over alumina

The reaction of catechol (pyrocatechol) with dimethyl carbonate (DMC) on alumina was studied. The main product was guaiacol, the selectivity for it being ca. 70%. Addition of water to the feed considerably increased the catalytic activity and the yield of guaiacol. The conversion of catechol was 68% at time-on-stream of 1 h at 553 K, though it decreased to 35% at 5 h. Addition of carbon dioxide to the feed considerably decreased the catechol conversion, indicating that the basic sites on alumina are active centers for methylation. It is also demonstrated that DMC is a much more efficient methylating agent than methanol in the methylation of catechol over alumina. (C) 1998 Elsevier Science B.V.