Synthesis of high performance hydroxyapatite-gold catalysts for CO oxidation

Catalysts for low temperature CO oxidation were prepared by decorating hydroxyapatite (HAp) ceramic foam scaffolds with highly dispersed gold nanocrystals using a deposition-precipitation (DP) process. Catalytic activity, microstructure and crystallinity were studied as a function of reagent pH (4-12) and aging time (10, 30,60 min) for powders and porous supports. Superior products with small (<= 5 nm) gold crystals distributed homogeneously over HAp foam were obtained at pH 8-9. Larger crystal sizes and colloidal gold agglomeration appeared at longer aging times. The optimized catalyst prepared by reaction at pH 9 for 30 min showed 100% CO conversion to CO2 at 150 degrees C. The Au-HAp composite demonstrated excellent durability by retaining structural and crystallographic integrity with no loss of activity when tested at 65 degrees C out to 166 h.