Coal Seams as an In-Situ Filter for Hydrogen Separation

Abstract Coal exhibits a selective sorption mechanism, making it a potential natural filtration system for gas purification. This study explores the use of coal seam gas reservoirs for the simultaneous separation and storage of carbon dioxide (CO2) from a mixture of hydrogen (H2) and CO2, the main products of Steam Methane Reforming (SMR). In this work, we present the results of two experimental tests, conducted on a core sample from the Bowen Basin. First, we measured and characterized H2 sorption onto the coal sample. Then, we performed a proof-of-concept experiment—a binary-component coreflooding test— to assess the competitive sorption behavior of H2 and CO2. The sorption measurements confirmed the low affinity of coal to H2, consistent with earlier observations in the literature. We also compared the results of H2 sorption with the CO2 sorption measurements of the same core sample. The comparison demonstrated that the coal sorption capacity for CO2 is approximately seven times greater than its capacity for H2 at a pressure of 10 MPa. The coreflooding test verified that a similar sorption contrast can be expected when the coal is exposed to a mixture of H2 and CO2. For this test, first, we equilibrated the sample with pure hydrogen and then continuously injected a mixture of H2 and CO2 with a molar ratio of 4:1. The coreflooding process showed that the injected CO2 displaced the adsorbed H2, despite its lower partial pressure, and an efficient CO2 separation and storage from this mixture, was achieved. These findings highlight the potential of coal seams for dual-purpose CO2 storage and gas purification. The results suggest that coal's selective sorption can be potentially exploited for CO2 capture and storage, thereby contributing to the improvement of the sustainability of hydrogen production from fossil fuels with carbon capture, utilization and storage (CCUS).