Formation of monolayer of molybdena over alumina by unconventional slurry impregnation or solvent assisted spreading method

Abstract

Alumina supported molybdenum catalysts with variable loading and support particle size were prepared by the unconventional equilibrium adsorption in slurry MoO 3/water. The method can be named either slurry impregnation method, SIM (when compared with impregnation in ammonium molybdate solution) or solvent assisted spreading, SAS (when compared with thermal spreading of MoO 3). The maximum saturated adsorption loading achieved with alumina of surface area 172 m 2 g −1 and particle size 0.16–0.32 mm was 14.4 wt% MoO 3. No other crystalline phase beside γ-Al 2O 3 was found in XRD spectra of the catalysts. The XPS surface ratio Mo Al in oxide form and the thiophene hydrodesulphurization activity in sulphide form increased linearly with the overall composition up to saturated adsorption loading. The hydrodesulphurization activity of the SIM SAS catalysts of corresponding loading was comparable or better than the activity of conventional commercial MoO 3 Al 2O 3 catalyst. All this indicated that the monolayer type catalysts are obtained by SIM SAS method. The electron probe micro analysis of the SIM SAS catalyst prepared from extrudates (1.5 mm) confirmed uniform cross sectional distribution of molybdena. This proved that the SIM SAS method can be used not only for small support particles but also for usual extrudates or tablets. The relation and advantage of the SIM SAS method as compared with other methods of preparation of monolayer molybdena catalysts were discussed.