The thermodynamic analyses were done to better understand the catalyst preparation and sulfidation processes. Chemical potential diagrams were used to evaluate the stability/reactivity of the metal, sulfides, oxides, and sulfates using the thermodynamic data base. For the NiMo(CoMo) and NiW/Al_2O_3 catalysts, these analyses suggested a priori that the catalyst treating conditions, such as temperature, p(O_2) and p(H_2O) in calcination, and such as temperature, p(H_2S)/p(H_2) and p(H_2O) in sulfidation, influenced significantly the solid-gas and solid-solid phases interactions among the active components, promoters and γ-Al_2O_3 supports. These thermodynamic analyses would be very useful for designing/selecting the catalytic materials and for optimizing the calcination/sulfidation/hydrotreating-reaction conditions.
