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. Graphical Abstract: [Figure not available: see fulltext.]