(559a) Microstructured Reactors for Catalytic Reforming of Higher Hydrocarbons

Middle distillates such as diesel fuels are promising candidates as feedstock for reformer of fuel cell systems. For this purpose, the steam reforming reaction of hexadecane was experimentally investigated in an electrically heated microstructured test reactor. The microchannels were coated with a ceria support layer using a sol-gel method and impregnated with a rhodium catalyst. The results of the variation of reaction parameters were used to determine turnover frequencies and for the modelling of the steam reforming reaction. Furthermore a microstructured system reactor was built with a catalytic combustion side to supply the heat demand for the thermally integrated reforming reaction.

The diesel surrogate hexadecane was chosen for all the experiments in order to characterize the steam reforming reaction with a pure fuel and to model the reaction rate using the same substance. The following parameters were varied during the experimental measurements: reactor temperature (400-700°C), residence time (38-220ms) and steam to carbon ratio (S/C = 3-6). The influence of the additional feeding of product gases such as hydrogen, carbon dioxide and carbon monoxide was also studied. The software gProms is used to calculate the kinetic parameters of the reaction.

The test reactor was heated with eight heating cartridges supplying up to 300W each. The reforming part of the system reactor was scaled up by a factor of four in terms of catalytic surface area while maintaining the catalytic load (mole hexadecane per mole catalyst and second) and catalytic system (Rh/CeO₂) in comparison to the test reactor. The catalytic combustion in the system shall be performed with hydrogen or hydrocarbon gases over a palladium-rhodium catalyst and supplying up to 3kW_th of heat. The test reactor, its microchannels and the system reactor are presented in figure 1. The system reactor with its special heat management permits to consider start up and load changing behaviour of the reforming process.

The ongoing work examines in more detail diesel fuel reforming by considering reforming of a greater number of diesel fuel constituents and/or a synthetic diesel fuel which shall lead to the design of a diesel reformer system for an auxiliary power unit.

Fig. 1 Micro reformer, left side: electrically heated test reactor and its microchannels (SEM picture), right side: system reactor heated by catalytic combustion