Genesis of HDT catalysts prepared with the use of Co2Mo10HPA and cobalt citrate: Study of their gas and liquid phase sulfidation

• CoMo catalysts prepared with the use of Co2Mo10HPA and cobalt citrate.
• Gas phase sulfided catalyst had higher cobalt content in CoMoS active phase and promoter ratio than liquid sulfided one.
• Gas phase sulfided catalyst had higher initial HDS activity than liquid sulfided one.
• Liquid phase sulfided catalyst was more resistant to the accelerated deactivation.

Genesis of alumina supported hydrotreating (HDT) catalysts prepared with the use of decamolybdodicobaltate heteropolyanion (Co2Mo10HPA) and cobalt citrate during their sulfidation processes and deactivation in diesel HDT has been investigated. The sulfidation stage was studied for two procedures: gas phase sulfidation by H2S/H2 and liquid phase treatment by a mixture of dimethyldisulfide in diesel at various temperatures and durations. The catalysts have been studied by N2 adsorption, thermogravimetric analysis, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy methods. The catalysts were tested in HDT of mixture of 70 wt.% straight run gas oil with 16 wt.% light cycle oil and 14 wt.% light coker gas oil. Mechanisms of the active phase formation in the course of gas and liquid phase sulfidation processes have been established. It was found that gas phase sulfidation led to formation of the CoMoS active phase with higher cobalt content comparing to liquid sulfidation of the catalyst and initial activity of the gas phase treated catalysts in diesel HDT was also higher than catalysts subjected to liquid sulfidation. Catalytic examination after accelerated deactivation conditions showed that the liquid phase sulfided sample was more resistant to the deactivation. Probably it is due to stabilization of active phase particles by coke formed intensively during liquid phase sulfidation. The results were discussed using the recently developed concept of interlayer dynamics of the active sites of the CoMoS phase.

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