OXIDATIVE CATALYSIS OF CHLORINATED HYDROCARBONS BY METAL-LOADED ACID CATALYSTS

Complete catalytic oxidation of methylene chloride in air was studied over concentration and temperature ranges from 1000 to 2000 ppm and 300 to 475°C, respectively. Three different supported zeolite catalysts, HY, CrY, and CeY, were prepared and their activities and selectivities investigated for the above reaction. Conversions varied from 17 to 99%, with catalytic activity decreasing in the order: CrY > HY > CeY. The oxygen chemisorption and the acidity values of the catalysts showed similar trends. Differences in oxidizability to higher valence states (CrY > CeY) and cation sizes (Ce3+ > Cr3+). were probable reasons behind the higher activity of the CrY. A dual site mechanism for the oxidation process, involving adsorption of chlorocarbon at Brønsted sites and adsorption of oxygen at cationic sites, was found feasible. The presence of water (about 27,000 ppm) in the feed stream reduced conversion between 10 and 60%, depending upon catalyst and temperature, and appeared to temporarily deactivate the catalysts. The selectivity among the catalysts was quite similar, with HCl and CO being the only major products. © 1991.