Hydrodechlorination of 1,4-Dichlorobenzene over Unsupported Sulfide Catalysts

• Published in: Petroleum chemistry Vol. 62; no. 11; pp. 1334 - 1342
• Main Authors: Dzhabarov, E. G., Petrukhina, N. N.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-11-2022; Springer; Springer Nature B.V
• Subjects: Catalysts; Chemical synthesis; Chemistry; Chemistry and Materials Science; Chlorine; Conversion; Dichlorobenzene; Hydrodechlorination; Hydrogen; Hydrogen chloride; Industrial Chemistry/Chemical Engineering; Nickel sulfide; Photoelectrons; Selectivity; Sulfides; sulfide catalyst; hydrodechlorination; unsupported catalyst; 1,4-dichlorobenzene; dispersed phase catalysis
• ISSN: 0965-5441; 1555-6239
• DOI: 10.1134/S0965544122110032

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 WO
x
S
y
in the first cycle and WO
3
in the fifth cycle, and nickel occurred in the NiS, Ni–W–S, and Ni
2+
forms. Transmission electron microscopy showed the formation of fine-dispersed particles of NiS and WS
2
.