PREPARATION OF UNIFORMLY DISPERSED MoP/AL2o3 CATALYSTS

Publisher Website
Google Scholar
Abstract
Several preparative factors which determine the properties of MoP/Al2O3 catalyst have been studied. With sequential impregnation, the Mo dispersion is always worse than with co‐impregnation, while in co‐impregnation the pH of the impregnating solution should be properly adjusted according to the P content. Since both molybdate and phosphate ions interact strongly with the alumina surface, they can adsorb directly at the pore mouths and inhibit other ions to enter the pores. Especially in the case of sequential impregnation, this results in a non‐uniform distribution of Mo and P over the alumina particles. In the case of co‐impregnation, with controlled pH and enough phosphoric acid, phosphomolybdate ions are formed which interact less strongly with the alumina surface. In that case, Mo can reach the inside part of the alumina particles and attain a uniform distribution. Also the Al2O3 particle size influences the Mo dispersion. Smaller particles have more outer surface and therefore it is easier for the molybdate and phosphate ions to diffuse to the centers of the pores, so that there is less chance that bulk Mo compounds are formed.