Volume 30: Urban Energy Systems towards Carbon Neutrality

Absorption-enhanced methanol steam reforming for low-temperature hydrogen production with carbon capture Xiao Li, Lingzhi Yang, Yong Hao

Abstract

Methanol is an ideal medium for hydrogen storage and transportation, and is expected to play a crucial role for the low carbon energy system in the foreseeable future. However, hydrogen derivation from methanol (via steam reforming) is faced by critical barriers including high reaction temperature (e.g., 250-300°C) and low methanol conversion (65% at < 200°C), and hydrogen purification process is usually indispensable for deriving high-purity H2. We propose a new method of H2 absorption-enhanced methanol steam reforming to tackle such challenges. The effectiveness of the method is further verified by a prototype reactor sequentially filled with bulk catalyst (CuO/ZnO/Al2O3) and bulk hydrogen absorbent (LaNi4.3Al0.7 alloy), tested at 200°C and 1 bar conditions. As H2 is absorbed by the alloy, both the reforming reaction and water-gas shift reaction are shifted forward, effectively enhancing the conversion of methanol. High-purity H2 is derived by regenerating the alloy under inert gas purge at 200°C, 700 mL min-1. During the 10 min reaction step, the H2 can be nearly completely separated. Furthermore, high purity hydrogen (~85% molar concentration) can be obtained in the regeneration step. Simulations considering the catalytic reaction kinetics further demonstrate the intensification effect of the absorption-enhanced method with different number of cycles and H2 separation ratios. Major advantages of the new method, including low reaction temperature, high-purity H2, non-precious material and membrane-less design, indicate great potentials for commercial applications. The remarkably reduced temperature also opens up wide possibilities of integrating with solar thermal energy and industrial waste heat for sustainable H2 production with significantly reduced CO2 footprint at the same time.

Keywords Hydrogen, methanol, absorption-enhanced reforming, CO2 capture, low-temperature