Multi-stage, isothermal CO preferential oxidation reactor

A multistage isothermal reactor for the selective reaction between CO and O.sub.2 in a H.sub.2 -rich gas flowing through said reactor to reduce the CO content of the gas to a suitable level which is not toxic to a fuel cell catalyst comprising:

• a housing;
• a plurality of catalyzed heat exchangers serially arranged within said housing in the direction of flow of said gas through said reactor for promoting said reaction in a series of progressive steps in which the CO content of the gas is incrementally reduced from one catalyzed heat exchanger to the next as the gas flows through said heat exchangers, said heat exchangers each comprising a plurality of thermally conductive barriers separating each heat exchanger into a plurality of first channels through which separate streams of said gas flow, and a plurality of second channels through which a coolant flows, said first channels having inlet ends for admitting said gas into said first channels and outlet ends for exhausting said gas from said first channels, said barriers each having (a) a catalyzed first surface confronting a said first channel, and (b) a second surface confronting a said second channel for contacting said coolant in said second channel to extract heat from said catalyzed first surface and maintain said heat exchanger at a substantially constant temperature suitable to promoting said reaction and discouraging the formation of CO from the reverse reaction of CO.sub.2 with H.sub.2, said first surface of one barrier and said first surface of the next adjacent barrier being spaced one from the other by at least one divider, said divider and said first surfaces together defining a said first channel for a first of said heat exchangers and a said first channel for a second of said heat exchangers that is contiguous said first heat exchanger, said first channels of said contiguous heat exchangers being substantially coplanar with each other;
• a mixing chamber between the outlet ends of the first channels of the heat exchanger that is immediately upstream of the chamber and the inlet ends of the heat exchanger that is immediately down stream of the chamber to receive and substantially homogenize said streams exiting said upstream heat exchanger so as to distribute any unreacted O.sub.2 and CO in said streams substantially uniformly throughout said gas before said gas enters said downstream heat exchanger, said chamber being configured to substantially reverse the direction of flow of said gas exiting said outlet ends and entering said inlet ends.