Unsupported Molybdenum Carbide and Nitride Catalysts for Polychlorinated Biphenyls Hydrodechlorination

Abstract

Unsupported Mo carbide and Mo nitride catalysts have been synthesized by temperature programmed synthesis, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction and desorption and N2 physisorption. These solid compounds have been tested for the hydrodechlorination (HDCl) of polychlorinated biphenyls (PCBs) at 1 bar in a fixed bed reactor. The Mo carbides and the corresponding Mo nitride phases showed a catalytic activity higher than a conventional HDS catalyst consisting of alumina-supported NiMo sulfides (*35 %). Aroclor 1260 HDCl conversion results were related to spilt-over hydrogen species that were proposed to favor the hydrogenolysis of C–Cl bond on refractory phases. The original PCBs broad distribution changed almost completely to non-chlorinated biphenyl on the carbide and nitride catalysts.