Effect of microwave double absorption on hydrogen generation from methanol steam reforming

Hydrogen generation from steam reforming of methanol (SRM) with a CuO/ZnO/Al₂O₃ catalyst was investigated in the study; particular emphasis was placed on the reactions of SRM exposed to an environment with microwave irradiation. By virtue of the double absorption of microwaves by both the reagents and the catalyst, the experiments suggested that the SRM could be heated and triggered rapidly within a short time, and the methanol conversion from SRM with microwave heating was high compared to that with conventional heating. The obtained results also indicated that, when the reaction temperature was as high as 250 °C, thermodynamic equilibrium governed the SRM, whereas the reaction was kinetically controlled for the temperature lower than 250 °C. Contrary to Le Châtelier's principle, it was noted that an increase in S/C ratio decreased methanol conversion. This can be explained by the fact that water absorbs microwave irradiation stronger than methanol. The performance of the SRM was evaluated based on the carbon conservation method and the nitrogen tracer method. It was found that the latter was also capable of providing an accurate prediction on methanol conversion, even though the flow rate of the product gas was not measured.