Start-up of thermally-integrated microchannel reformers with a noble metal reforming catalyst

The wash coating process produces a porous layer on all surfaces of the foam, which layer forms a base for the catalyst coating. The interstices as well as the outside surfaces of the open cell foam monolith are wash coated and are also catalyzed. Since the catalyst beds are of minimal size and weight they are especially suited to vehicular applications where size and weight are critically important, and because vehicle applications require rapid start-up capability that is closely dependent on the size and weight of the components. Small, light-weight catalyst and reactant beds can be rapidly heated with a minimum energy input. Heat is generated internally in the reformer catalyst bed due to the addition of air to the process gas stream, which is a fuel-steam mixture. Thus, there is no need to spread the reforming catalyst along large heat transfer surfaces as is required with a conventional steam reformer. The use of an open cell foam monolith as the catalyst support bed can increase the catalyzed surface area of the support bed by a factor of at least three, depending on the pore size of the foam catalyst support bed. Use of the foam support bed can also reduce the volume of the bed by a factor of at least three, and can reduce the weight of the bed by an even greater factor, as compared to a pelletized catalyst bed. The increased open volume results in a much lower pressure drop across the catalyst bed than can be achieved with a pelletized bed. Start-up of the thermally-integrated microchannel reformer can be achieved by either pre-heating the bed with a hot gas, such as steam, or by fabricating either the entire monolith or just the inlet section with a conductive resistance monolith element. The resistance element can be connected to an electrical source such as a car battery which will enable the monolith to reach operating temperatures within less than twenty seconds. The inlet portion of the catalyst bed is operable to bum oxygen and a minor amount of the fuel gas so as to raise the temperature of the inlet portion of the catalyst bed. This raises the temperature of the gas stream to temperatures which provide enhanced conversion of the fuel stream to a high hydrogen-content gas. Minimal oxygen requirements serve to inhibit carbon formation in the catalyst bed. Other carbon formation-suppressing catalyst bed components such as calcium oxide, lanthanum oxide, and cerium oxide, for example, could also be used. For a methanol fuel, the subsequent reforming section of the catalyst bed is provided with a conventional copper, copper-zinc or noble metal reforming catalyst, or a combination of a copper or copper-zinc reforming catalyst, and a noble metal reforming catalyst.