Preparation of sulphide catalysts for heteroatom elimination in hydrocarbon refining

Abstract

Sulphide catalysts containing Co, Ni, Mo and/or W catalyse hydrogenolysis of carbon sulphur/nitrogen/oxygen bonds and they are widely used in the hydrodesulphurization (HDS) of petroleum fractions. The HDS process produces H₂S, which is subsequently partially oxidized to water and elemental sulphur in the Claus process. Nevertheless, this process can be overflowed with H₂S. Sulphide catalysts are therefore investigated for the direct thermo-catalytic decomposition of H₂S to form H₂ and elemental sulphur. This work tailors on a novel and straightforward preparation method of the unsupported form of Co/MoS₂, Ni/MoS₂, Ni/WS₂ and Ni/MoWS₂ catalysts. The aqueous slurry of CoCO₃.Co(OH)₂ or 2NiCO₃.3Ni(OH)₂·4H₂O reacts with MoS₂, WS₂ or MoS₂+WS₂ during milling in a planetary mill. After drying and re-sulphidation, the catalyst is characterised by its specific surface area (S_BET), free sulphur vacancies (O₂ up-take), crystalline size of molybdenite and/or tungstenite (D_XRD), activity in thiophene (Th) and 4,6-dimethyldibenzothiophene (4,6DMDBT) HDS, and activity in thermo-catalytic decomposition of H₂S. We concluded that the prepared catalysts are active in Th and 4,6DMDBT hydrodesulphurization, and thermo-catalytic decomposition of H₂S. The Ni/WS₂ is the most active in all reactions and also the most selective to direct desulphurization (DDS) during the 4,6DMDBT HDS. WS₂ best suits the studied preparation method.