Preparation of molybdenum carbide catalyst and its hydrodesulfurization performance for thiophene
Molybdenum carbide catalysts were prepared by temperature-programmed reaction using CH_4/H_2 gas mixture to carburize molybdenum trioxide at different temperatures, then were characterized with XRD and BET. TG-DTA in-situ approach was used to investigate the carburizing reaction of MoO_3 in CH_4/H_2.The catalytic performance of molybdenum carbide catalysts was evaluated for hydrodesulfurization by using 5%(vol) thiophene as the model reactant under the conditions of 300—370℃, 3.0 MPa and space velocity 6 h -1. The results indicated that molybdenum carbide catalysts possessed much higher thiophene HDS activity than MoS_2, and the HDS conversion of thiophene reached 98% at 370℃. It was also found that the BET surface area of molybdenum carbide catalysts decreased and more free carbon deposited on the catalyst surface with increasing carburizing temperature.Furthermore the HDS activity for thiophene decreased. The carburizing reaction pathway of MoO_3 in CH_4/H_2 was MoO_3→MoO_2→MoO_xC_y→Mo_2C, and the proper carburizing temperature was 675℃ as determined by experiment in this paper.