Characterization of CoMo-Al₂O₃ Catalyst by Combination Technique of Temperature-programmed Sulfiding and Electron Spin Resonance (TPS-ESR)

Abstract

CoMo-Al₂O₃ catalyst was characterized with a combination technique of temperature-programmed sulfiding (TPS) and electron spin resonance (ESR). The behavior of the MoO₃ loaded over the surface of Al₂O₃ obtained from TPS has been compared with that of Mo⁵⁺ observed with ESR at isothermal and elevated temperatures. The Mo⁶⁺ in the MoO₃ supported is easily reduced with H₂S+H₂ under very mild conditions and transformed into Mo⁵⁺ as an intermediate. This Mo⁵⁺ peak drastically decreased around 200°C with H₂S desorption, and H₂ consumption appeared simultaneously in the TPS profile. These results suggest that the Mo⁵⁺ species observed with ESR associates with sulfur from H₂S.