A catalyst for preferentially reducing carbon monoxide in a hydrogen stream. The catalyst is formed from a chemical composition including a hexaaluminate, a metal hydroxide and a precious metal. The composition may be disposed on a support or may be extruded or cast into or onto a support. Incorporation of hexaaluminates allows inclusion of metal hydroxides that flux the active precious metal surface at higher temperatures than can aluminum oxide-based catalytic compositions, thereby enhancing resistance of the catalyst and monolithic support and increasing the durability and thermal range of the PROX catalyst. An additional advantage is that lesser amounts of precious metal oxides need be deposited onto the hexaaluminate, while retaining activity similar to aluminum oxide compositions.