Coating mesoporous alumina onto the macropore walls of monolithic α-Al2O3 and its use as catalyst support for preferential oxidation of CO

Abstract

Monolithic α-Al₂O₃ with a mesoporous Al₂O₃ layer coated onto its macropore walls was successfully prepared. Macroporous monolithic polystyrene foams were filled with alumina hydrosol followed by drying and high temperature calcination to obtain macroporous monolithic α-Al₂O₃ with good mechanical strength. The resulting macroporous alumina monolith was impregnated with an alumina sol solution containing Pluronic P123 as a mesoporous structure-directing agent. Following drying and calcination, a meso-macroporous monolithic alumina was obtained. The mesopores were assembled on the macropore walls, which elevated the specific surface area and the pore volume of the monoliths. The macropore walls had a measurable influence on the porosity of the mesoporous alumina on the walls. In the drying stage, the influence was ascribed to capillary force; in the calcination process, the influence was due to the confinement of the macropore walls to the mesoporous material. The prepared meso-macroporous alumina monolith was used as catalyst support for the preferential oxidation of CO in hydrogen-rich gases, and the monolith supported Pt–Ni catalyst showed high activity and selectivity for the reaction.