Spatially resolved Raman and UV-visible-NIR spectroscopy on the preparation of supported catalyst bodies: Controlling the formation of H 2PMo11CoO405- inside A1 2O3 pellets during impregnation

Abstract

The physicochemical processes that occur during the preparation of CoMo-Al2O3 hydrodesulfurization catalyst bodies have been investigated. To this end, the distribution of Mo and Co complexes, after impregnation of γ-A12O3 pellets with different CoMoP solutions (i.e., solutions containing Co, Mo, and phosphate), was monitored by Raman and UV-visible-NIR microspectroscopy. From the speciation of the different complexes over the catalyst bodies, insight was obtained into the interaction of the different components in the impregnation solution with the A1 2O3 surface. It is shown that, after impregnation with a solution containing H2PMo11CoO405-, the reaction of phosphate with the A12O3 leads to the disintegration of this complex. The consecutive independent transport of Co 2+ complexes (fast) and Mo6+ complexes (slow) through the pores of the A12O3 is envisaged. By the addition of extra phosphate and citrate to the impregnation solution, the formation of the desired heteropolyanion can be achieved inside the pellets. Ultimately, the H 2PMo11CoO405- distribution could be controlled by varying the aging time applied after impregnation. The power of a combination of spatially resolved spectroscopic techniques to monitor the preparation of supported catalyst bodies is illustrated. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.