FLY-ASH MEDIATED REACTIONS OF PHENOL AND MONOCHLOROPHENOLS - OXYCHLORINATION, DEEP OXIDATION, AND CONDENSATION

Monochlorophenols are smoothly oxidized to carbon dioxide and carbon monoxide when vapors in air are passed over fixed beds of municipal waste incinerator fly ash at 625-725 K. Simultaneously polychlorinated benzenes, monobenzofurans, and dibenzo-p-dioxins are formed with a large fraction of the original chlorine concentrated in these products. Fly ash catalyzed oxychlorination of phenol in the presence of HCl at 425-725 K resulted in the formation of chlorinated phenols which, in turn, were converted above 625 K into mainly CO2 and the (poly)chloroarenes mentioned above. In contrast, under similar conditions, (chlorinated) benzenes are inert. Deep oxidation and oxychlorination of phenol have also been studied using an oxidation catalyst (CuO on alumina) or a commercial oxychlorination catalyst (basically, CuCl2 on alumina). Results were comparable but, in neither case, chlorinated dibenzo-p-dioxins were detected. Kinetic data are presented and analyzed, and reaction mechanisms and the practical relevance of our results are discussed.