Study the Acidity Surface Effects on the Dispersion of Molybdena on Alumina Catalyst

The modification of catalyst structures can be very important for achieving high activities, selectivity s, and stabilities. Acidity (pH) is one method that can be used for this purpose. Dispersion is mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. Supported molybena (M0O3) catalysts were prepared by impregnating support alumina (AI2O3) with an aqueous solution at different pH s (6, 9, 11) of ammonium hepta molybdate, to yield final materials containing 8, 12 and 16 wt % of M0O3/ AI2O3 catalysts. After stirring for 3 h, the excess water was slowly evaporated at 100°C. Prior to calcination, the impregnated supports were further dried at 120°C for 24 h. The products thus obtained were calcined at 600 °C for 2 h in static atmosphere of air. Thermal analysis, X-ray powder diffractogram and Infrared spectroscopy for support (AI2O3) and supported (M0O3) catalysts were investigated. The results suggest formation of highly dispersed M0O3 on the surface of AI2O3 8 wt%, at pH 6, 12 wt%, at pH 9 and 16%, at pH 11. This indicted that, a poor dispersion of M0O3 on AI2O3 surface at low pH. Since, at low pH = 6 the form of small M0O3 crystallites was observed at 8 wt%. Whereas, at high pH = 11 the form of small M0O3 crystallites was observed at 16 wt%. These conclusions can be reorganized on the basis of the different surface chemical properties of the oxide support and nature of oxide supported