PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

Abstract

Several preparative factors which determine the properties of MoP/Al203 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 mdybdate 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 Al203 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.

Surface‐Dependent Activation of Model α‐Al2O3‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

“…This dopant is widely used in industrial formulations since there is general agreement that it leads to an increase in HDS activity [36–42] by reducing the interactions between the active phase and the support as phosphates block the basic surface Al‐OH sites that selectively interact with the Mo active phase. It has also been reported that phosphorus can improve Mo dispersion [43] . Nonetheless, this beneficial effect is highly dependent on the P‐loading and on the incorporation method.…”

“…It has also been reportedt hat phosphorusc an improveM od ispersion. [43] Nonetheless, this beneficial effect is highly dependento nt he P-loadinga nd on the incorporation method. For instance, co-impregnation of phosphorusa nd metal precursors modifies the chemical structure of the depositedp recursor by forming heteropolyanions, [19,38,40] which may have an effect both on Mo dispersion and posterior catalysta ctivation.…”

THE FUNCTION OF PHOSPHORUS , NICKEL AND H2S IN THE HDN OF PIPERIDINE AND PYRIDINE OVER NiMoP/Al2O3 CATALYSTS

“…It has been reported *Present address : Escuela de lngenieria Quimica, UMSNH, Mordia, Mich., Mexico that phosphorus not only enhances the solubility of molybdate by the formation of phosphomolybdate complexes and thus makes catalyst preparation easier (see references in ref. 7), but also that it increases the HDN activity of NiMolAlnOs catalysts (8-1 0). However, the beneficial catalytic effects of phosphorus were observed In studies of quinoline HDN, where not only C-N bond breaking, but also hydrogenation of benzene and pyridine rings are Involved in the reaction network and are needed prior to C-N bond breaking.…”

Study on the Hydrotreating Catalysts Containing Phosphorus of Coal Tar to Clean Fuels

“…In contrast, Eijsbouts et al [8] reported an increase in quinoline conversion to hydrocarbons and an increased selectivity for unsaturated nitrogen-free hydrocarbons with the addition of P in the NiMo/γ-Al 2 O 3 catalyst. Jian et al [9] also reported the boost effect of P on the HDN of ortho-propylaniline (OPA) and reached a decision that P caused the advantage adsorption of OPA on the catalyst because of the production of increased number of catalytic sites.…”