Preparation and properties of filled monolayer of MoO_3 deposited on Al_2O_3 supports by solvent-assisted spreading

摘要

Catalysts MoO_3/Al_2O_3 were prepared by solvent-assisted spreading method,which is the reaction of Al_2O_3 support with the slurry of MoO_3 in water.Fifteen Al_2O_3 supports with surface area S_BET in the range of 11-279 m~2 g~(-1)were used.The method belongs to equilibrium adsorption impregnation methods and provides the catalysts with filled monolayer of molybdena species;the formation of bulk MoO_3 and Al_2(MoO_4)_3 is avoided.The saturated adsorption loading,corresponding to filled monolayer loading,linearly increased with S_BET and the mean density of filled monolayer calculated from the slope was 3.4Mo nm~~(-2).The deposited-filled monolayer was X-ray amorphous.Two reduction peaks were observed by temperature-programmed reduction.Their position was independent of Al_2O_3 surface area indicating the same quality of filled monolayer in all catalysts.The samples were sulfided and their activity in hydrodesulfurization(HDS)of thiophene(TH)at the pressure of 1 MPa and temperature 280-4-00 deg C was tested.Activation energy of all samples was similar and their activity increased linearly with saturated adsorption loading;that again proves the same quality of filled monolayer independently of S_BETof Al_2O_3.It was found with four Al_2O_3 that the catalysts prepared by solvent-assisted spreading were equally or more active(by up to 37%,depending on Al_2O_3)as compared with the corresponding catalysts prepared by conventional impregnation using(NH_4)_6Mo_7O_24 solution.