Micro-crystalline molybdenum sulfide prepared by mechanical milling as an unsupported model catalyst for the hydrodesulfurization of diesel fuel

摘要

Micro-crystalline molybdenum sulfide(MoS_2)was prepared by mechanical milling as an unsupported model catalyst for hydrodesulfurization(HDS)of diesel fuel,was prepared by mechanical milling.The catalytic function of the micro-crystallite was analyzed on the basis of the data from XRD measurements,TEM observations,and activity measurements.During the activity measurements,desulfurization of 4,6-dimethyldibenzothiophene(4,6-DMDBT)was carried out at 320 deg C in an autoclave initially charged with 5 MPa of hydrogen.The desulfurizing kinetics was evaluated for the unsupported MoS_2 in comparison with an industrial catalyst,alumina-supported cobalt-molybdenum sulfide.The unsupported MoS_2 was more able to enhance the desulfurizing kinetics for 4,6-DMDBT than the industrial catalyst under the equivalent weight of molybdenum,while the unsupported MoS_2 was inferior to the industrial catalyst in desulfurizing dibenzothiophene(DBT).Since the major catalyzed reaction was the hydrogenative desulfurization for the unsupported MoS_2,it was an appropriate catalyst for 4,6-DMDBT,which was desulfurized under steric hindrance.Catalyst fouling was analyzed on the basis of the data from the real HDS reaction with diesel fuel in a down-flow tubular reactor,at 330-360 deg C with 1.5-3.0 h~(-1)under 5 MPa of hydrogen.The deposited carbon and the nitrogen constituents fouled the unsupported MoS_2 more seriously than was the case for the industrial catalyst.