An apparatus for preferential oxidation of carbon monoxide in a reformate flow includes a reactor defining a flow path for a reformate flow; at least one catalyst bed disposed along the flow path; and a distributor for distributing oxygen from an oxygen source to the at least one catalyst bed, the distributor including a conduit positioned at least one of upstream of and through the at least one catalyst bed, the conduit having a sidewall permeable to flow of oxygen from within the conduit to the at least one catalyst bed.