Competitive Hydrodechlorination and Hydrodeazotization on Unsupported Sulfide Catalysts Synthesized in Situ

The catalytic activity of an unsupported nickel-promoted tungsten disulfide catalyst prepared in situ in the reaction medium was studied in the competitive hydrodechlorination of 1,4-dichlorobenzene and hydrodeazotization of quinoline. The morphology and phase composition of the catalyst were studied by x-ray photoelectron spectroscopy and transmission electron microscopy. This study indicated the presence of nickel sulfide, nickel chloride and a mixed NiWS phase on the surface of the tungsten disulfide catalyst. A considerable decrease in catalyst activity was noted during the concurrent hydrodechlorination and hydrodeazotization reactions, leading to a decrease in the extent of hydrodechlorination of 1,4-dichlorobenzene. The loss of catalyst activity was attributed to the strong adsorption of nitrogen-containing compounds as well as the accumulation of quinolinium salts on the catalyst surface.