NOVELTY - Method-I of using a catalyst body able to support gas flow through it and having a catalyst for promoting a catalytic reaction of a component of a first gas and being able to be regenerated by a second gas, comprises: providing at least the first gas and second gas; and repeatedly moving successive parts of the catalyst body into communication with the first gas and then with the second gas, where the part of the catalyst body in communication with the first gas causes the component of the first gas to be reacted as the first gas passes though and exits the part of the catalyst body.    USE - The method is useful for promoting a catalytic reaction of a component of a first gas and a second gas using a catalyst body having a catalyst to support gas flow, where the catalyst body is useful in an fuel cell system (claimed), preferably proton exchange membrane fuel cell applications.    ADVANTAGE - The method promotes the catalytic reaction of the gas component in a simple manner without interrupting the oxidation of carbon monoxide using compact catalyst body.    DETAILED DESCRIPTION - Method-I of using a catalyst body able to support gas flow through it and having a catalyst for promoting a catalytic reaction of a component of a first gas and being able to be regenerated by a second gas, comprises: providing at least the first gas and second gas; and repeatedly moving successive parts of the catalyst body into communication with the first gas and then into communication with the second gas; where, the part of the catalyst body in communication with the first gas causes the component of the first gas to be reacted as the first gas passes though and exits the part of the catalyst body; and the part of the catalyst body in communication with the second gas has the catalyst of that part regenerated as the second gas passes through and exits the part. INDEPENDENT CLAIMS are included for:    (1) a catalyst body for use in an fuel cell system, where the catalyst body is formed from a ceramic corderite structure having pores and coated with a catalyst; and    (2) a method of making a catalyst body for use in a fuel cell system comprising preparing a solution of a binder and a M-octahedral molecular sieve (OMS)-2 catalyst, and applying the solution to a ceramic corderite structure having pores to coat the structure.    DESCRIPTION OF DRAWING(S) - The figure shows a proton exchange membrane fuel cell system using an oxidizer assembly for oxidizing carbon monoxide.    Fuel supply (3)    Reformer (4)    Shift reactor (5)    Oxidizer (6)    Oxidant supply assembly. (7)