Absorption-Enhanced Methanol Steam Reforming for Low-Temperature Hydrogen Production with Carbon Capture

Abstract

Methanol is a prospective hydrogen storage medium that holds the potential to address the challenges of hydrogen storage and transportation. However, hydrogen production via methanol steam reforming faces several key obstacles, including high reaction temperature (e.g., 250–300 °C) and low methanol conversion (at <200 °C), while the purification procedure of hydrogen is commonly required to obtain high-purity H2. A novel method of H2 absorption-enhanced steam reforming of methanol is proposed to overcome the challenges mentioned above. The method involves the absorption and separation of H2 using an absorbent to facilitate the forward shift of the reaction equilibrium and enhance reaction performance. A thermodynamic analysis using the equilibrium constant method presents that the separation of H2 can improve the methanol conversion rate and the total H2 yield. The feasibility of the method is validated through experiments in a fixed-bed reactor (4 mm diameter, 194 mm length) under the conditions of 200 °C and 1 bar. In the experiments, 1 g of bulk catalyst (CuO/ZnO/Al2O3) and 150 g of bulk hydrogen absorbent (Aluminum-doped lanthanum penta-nickel alloy, LaNi4.3Al0.7 alloy) are sequentially loaded into the reactor. As a proof of concept, a CO2 concentration of 84.10% is obtained in the reaction step of the first cycle, and a gas stream with an H2 concentration of 81.66% is obtained in the corresponding regeneration step. A plug flow reactor model considering the kinetics is developed to analyze the effects of the number of cycles and H2 separation ratio on the enhancement performance. The method indicates a high potential for commercialization given its low reaction temperature, high-purity H2, and membrane-free design.