The present invention relates to compositions for use at start-up a reformer of a fuel cell system. In particular, this invention includes emulsion compositions comprising hydrocarbon fuel, water and surfactant for use at start-up of a reformer of a fuel cell system.
Fuel cell systems employing a partial oxidation, steam reformer or autothermal reformer or combinations thereof to generate hydrogen from a hydrocarbon need to have water present at all times to serve as a reactant for reforming, water-gas shift, and fuel cell stack humidification. Since water is one product of a fuel cell stack, during normal warmed-up operation, water generated from the fuel cell stack may be recycled to the reformer. For start-up of the reformer it is preferable that liquid water be well mixed with the hydrocarbon fuel and fed to the reformer as an emulsion. The current invention provides emulsion compositions suitable for use at start-up of a reformer of a fuel cell system.
One embodiment of the invention provides emulsion compositions suitable for use at start-up of a reformer of a fuel cell system comprising hydrocarbon, water and surfactant.
In a preferred embodiment, the emulsion composition is a bicontinuous emulsion comprising a coexisting mixture of at least 80 vol % of a water-in-hydrocarbon macro-emulsion and from 1 to 20 vol % of a hydrocarbon-in-water micro-emulsion.
In another embodiment of the invention is provided a method to prepare a bicontinuous emulsion comprising a coexisting mixture of at least 80 vol % of a water-in-hydrocarbon macro-emulsion and from 1 to 20 vol % of a hydrocarbon-in-water micro-emulsion comprising mixing hydrocarbon, water and surfactant at low shear.
In yet another embodiment is a bicontinuous emulsion composition comprising a coexisting mixture of at least 80 vol % of a water-in-hydrocarbon macro-emulsion and from 1 to 20 vol % of a hydrocarbon-in-water micro-emulsion.