Adsorption-membrane hybrid system for ethanol steam reforming: Thermodynamic analysis

In this study, an adsorption-membrane hybrid system in which a carbon dioxide adsorbent is used to remove undesired carbon dioxide and a membrane is applied for hydrogen separation is theoretically investigated with the aim to improve the performance of an ethanol steam reforming. A thermodynamic analysis of such the system was performed and compared with a membrane reactor and an adsorptive reactor. It was found that the removal of hydrogen by membrane separation has higher impact on the reformer performance than the carbon dioxide capture by adsorption. The adsorption-membrane hybrid system for ethanol steam reforming gives the highest hydrogen yield. Considering a possibility for carbon formation, the simulation results showed that the use of membrane for pure hydrogen production increases the trend toward carbon formation. This is due to an increase in carbon monoxide concentration in the reaction zone that promotes the Boudouard reaction. In contrast, the use of carbon dioxide adsorbent reduces the formation of carbon as carbon monoxide is less generated in the system.