Regulation of multilayer long crystalline MoS₂ by NiO-modified Al₂O₃ for improved hydrodesulfurization of COS

Activated alumina-based composite oxide support is a commonly used support in hydrodesulfurization (HDS) catalysts, which not only retains the performance advantages of each component in the composite oxide support, but also significantly improves the defects of a single activated alumina support, such as the strong metal-support force of interaction. In this study, NiO-Al₂O₃ composite support was prepared by introducing NiO-modified Al₂O₃, and MoS₂/NiO-Al₂O₃ catalysts were prepared for the hydrodesulfurization of COS by liquid phase reduction method. In the COS hydrogenation reaction, the MoS₂/NiO-Al₂O₃ catalyst achieved complete conversion of COS at 220 °C and showed more than 99.9% H₂S selectivity. In stability tests, the catalyst maintained a COS conversion of over 99% throughout the 23-h hydrogenation reaction. Various characterization results show that the NiO-Al₂O₃ composite support prepared by introducing NiO-modified Al₂O₃ weakens the metal-support interaction force between MoS₂ and NiO-Al₂O₃ composite support, which is conducive to the synthesis of MoS₂ with multilayer and long wafer structures. And it can significantly increase the formation rate of MoS₂ to 87.9%, which greatly improves the active site content of the catalyst. Furthermore, the dual modulation of MoS₂ and Al₂O₃ by NiO modulated the surface alkalinity of the catalysts and promoted the formation of a large number of active edge sites in the MoS₂/NiO-Al₂O₃ catalysts, which in turn significantly improved the HDS performance of the catalysts. In addition, EPR characterization combined with experiments showed that the sulfur vacancies are the active sites for catalytic COS hydrodesulfurization over MoS₂-based catalysts.