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°C. The Au-HAp composite demonstrated excellent durability by retaining structural and crystallographic integrity with no loss of activity when tested at 65°C out to 166 h.
- CO oxidation
- Deposition-precipitation process
- Gold nanocrystal