A cerium oxide modified Al2O3(Ce-Al2O3)and a macro-mesoporous Al2O3(M-Al2O3),which are both rich in pentahedrally coordinated Al3+,are synthesized via a low-temperature combustion method and a solvothermal method,respectively.MoP catalysts are obtained through temperature-programmed method to reduce the supported molybdenum phosphate precursors prepared via an impregnation method.The hydrodesulfurization performances of MoP catalysts are evaluated through using dibenzothiophene(DBT)as model sulfur-containing compound.It is indicated that the P/Mo molar ratio in the phosphate precursor required for the formation of phase-pure MoP over M-Al2O3 is between 1 and 1.2.The conversion of DBT over MoP catalysts drops in the order of MoP(1)/SiO2＞MoP(1)/Ce-Al2O3＞MoP(1.2)/M-Al2O3.It is demonstrated by the kinetic study that the hydrodesulfurization activation energy of DBT over MoP(1)/Ce-Al2O3 is nearly same as that over MoP(1.2)/M-Al2O3,both are much lower than that over MoP(1)/SiO2.Over these MoP catalysts,the selectivity of the direct desulfurization pathway increases with the rising temperature.At a relatively low temperature(e.g.280℃),the desulfurization of DBT occurs mainly through the hydrogenation pathway;while at a high temperature(e.g.360℃),both the direct desulfurization and hydrodesulfurization pathways play an equal role.
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