Synthesis of a high surface area monolayer MoO3/MgO catalyst in a (NH4)(6)Mo7O24/MgO/methanol slurry, and its hydrodesulfurization activity

High surface area MoO3/MgO catalysts (200-270 m(2) g(-1)) have been prepared by the reaction of MgO with the impregnation slurry (NH4)(6)Mo7O24/methanol. Molybdena was deposited and NH3 was evolved. The texture of water sensitive MgO was stable in the slurry. The impregnation reaction was limited to the MgO surface at 25 degrees C where each Mo atom occupied about 0.24-0.28 nm(2) at saturation. However, impregnation probably continued into subsurface layers of MgO at 65 degrees C where the saturation loading corresponded to 0.13-0.16 nm(2) per Mo atom. Gradual penetration of molybdena into MgO extrudates indicated that the surface reaction between dissolved (NH4)(6)Mo7O24 and MgO was fast and the rate determining step of impregnation was dissolution or diffusion of (NH4)(6)Mo7O24. The MoO3/MgO catalysts were prepared using various particle sizes of MgO, various loadings of MoO3, different temperatures and impregnation times. The activity of the best MoO3/MgO catalysts in the hydrodesulfurization of benzothiophene was similar to the activity of the commercial conventional hydrodesulfurization catalyst MoO3/Al2O3.