Hydrodechlorination of 1,4-Dichlorobenzene over Unsupported Sulfide CatalystsстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 17 апреля 2024 г.
Аннотация:A number of unsupported NiMo, CoMo, and NiW sulfide catalysts synthesized in situ from oil-soluble precursors were investigated in hydrodechlorination of 1,4-dichlorobenzene. The unsupported NiW and NiMo sulfide catalysts exhibited the highest activity; after seven hours on stream in a batch-type reactor at 320°C and 4 MPa hydrogen, both catalysts achieved 99% conversion of 1,4-dichlorobenzene, and the selectivity towards chlorine-free products reached 99 and 78%, respectively. Under identical conditions, the CoMo(S) catalyst provided lower conversion (88%) with 100% selectivity. In contrast, under similar conditions a commercial NiW(S) catalyst exhibited comparable conversion with lower selectivity (95%), and a commercial NiMo(S) catalyst provided 82% conversion and 53% selectivity. The activity of the synthesized unsupported catalysts remained unchanged even after five cycles of reuse, whereas the commercial catalysts deactivated due to the destruction of the support when interacting with hydrogen chloride. The study revealed the optimum hydrodechlorination conditions in the presence of unsupported sulfide catalysts and identified the effects of the promoter to active metal ratio on conversion and selectivity. For the NiW(S) catalysts, it was found using X-ray photoelectron spectroscopy that tungsten was mostly present as WOxSy in the first cycle and WO3 in the fifth cycle, and nickel occurred in the NiS, Ni–W–S, and Ni2+ forms. Transmission electron microscopy showed the formation of fine-dispersed particles of NiS and WS2.