Kinetic study of ethanol reforming in a microreactor

We have demonstrated the successful application of a microchannel reactor to produce hydrogen by ethanol reforming. Microchannels coated with Rh/CeO2 catalyst were used at residence times of 9–42 ms. Reaction temperatures were 350–660 °C, and the steam to carbon ratio was varied between 2 and 4. Even with a low steam to carbon ratio of 2 it was possible to ensure low methane by-product concentrations below 1% by lowering the residence time in the microreactor to 9 ms. For temperatures above 625 °C, a H2 space time yield of 400 mmol g min−1 was reached, four times more than the highest values reported in the literature. Negligible coke formation was found in the metallic microreactor even at low steam to carbon ratios of 2. This can be attributed to superior heat supply compared to conventional reactors and the low acidity of the applied catalyst.The applied microreactor was suitable for the determination of kinetic data of the ethanol reforming reaction. It was shown that neither mass nor heat transport limitations falsify the experimentally determined kinetic parameters. Consequently, the excellent isothermal behaviour of the microchannel reactor is supposed to be responsible for a good fit of the calculated values of the selected models to the experimental results. The model and experiments were in good agreement for a wide range of ethanol and water partial pressures, steam to carbon ratios, and temperatures. Rate determining steps in the models were CO2 desorption, dissociative ethanol adsorption and reaction of adsorbed methane with steam from the gas phase for the identified main reactions, i.e. water gas shift, ethanol decomposition and methane steam reforming, respectively.

Graphical abstractIn a microchannel reactor it was possible to produce hydrogen by ethanol reforming even with a low steam to carbon ratio of 2 with low methane by-product concentrations below 1%. For temperatures above 625 °C, very high H2 space time yield of 400 mmol g min−1 was reached, four times more than the highest values reported in the literature.The applied microreactor was excellently suitable for the determination of kinetic data of the ethanol reforming reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide