Sorption enhanced steam reforming of ethanol for hydrogen production, over Mg/Al hydrotalcites modified with K

Abstract

Sorption-enhanced ethanol steam reforming is an interesting alternative, to produce high purity H2. In this study, potassium promoted hydrotalcites are compared for sorption-enhanced ethanol steam reforming reaction under cyclic operation, performing sorbent regeneration at reaction temperature which is a great advantage to reduce process energy requirements. It is found that potassium promoted hydrotalcites have higher CO2 sorption capacity compared to unpromoted ones, due to the higher concentration of intermediate and strong basic sites. The hydrotalcite modified with 15 wt% potassium shows the best performance on multicyclic CO2 sorption-desorption (sorption capacity = 0.167 molCO2/kgsorbent). Therefore, there is an optimum loading of potassium, for which the opposite effects of reduction in surface area and enhanced basicity are balanced. Finally, potassium promoted hydrotalcites are tested under cyclical ethanol reforming process with simultaneous adsorption of CO2 followed by regeneration in N2 at reaction temperature (500 °C). At short reaction times (<5 min), H2 purities higher than 95% are achieved, with CO2 purities near 0%.