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

Monolithic alpha-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 alpha-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.