Preparation of catalytic cordierite monoliths for the selective oxidation of carbon monoxide

Abstract

The objective of this study was to investigate the state-of-the-art preparation methods for environmentally friendly, engineered, multi-channeled catalysts called monoliths and to develop a preparation procedure for cordierite monolithic Pt-Co-Ce-Al2O3 catalysts used for the preferential oxidation of CO in a hydrogen-rich environment. In this comparative study, monolithic catalysts were prepared by applying a layer of alumina support on to the walls of a cordierite monolithic carrier, termed as wash-coating, and then impregnating active components. The monoliths were wash-coated with alumina using three different methods, namely, colloidal coating, slurry coating and aluminum nitrate coating. Metal precursor solutions containing Pt-Co-Ce were impregnated over alumina wash-coated monoliths. Catalyst compositions were determined by atomic absorption spectrometry. Total surface area measurements, environmental scanning electron microscopy (ESEM) and optical microscopy were employed to physically characterize the catalysts prepared. The most promising monolithic catalyst preparation method was determined to be colloidal coating. Colloidal alumina coated and Pt-Co-Ce impregnated monolithic catalysts were tested for the preferential CO oxidation reaction in a micro-reactor flow system under a total flow of 100 cm3 min–1 using reaction temperatures in the 383-443 K range and typical feed compositions. The monolithic catalyst was found to exhibit the highest catalytic activity towards CO oxidation approaching 100 per cent CO conversion at a temperature of 443 K in a feed containing 1.0 volume per cent CO, 1.0 volume per cent O2 and 60.0 volume per cent H2 and balance helium.