Differential adsorption of H2S/CH4 by bituminous coal and its competitive adsorption properties

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 500; p. 157447
• Main Authors: Li, Jinluo, Ge, Shaocheng, Liu, Shuo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2024
• Subjects: adsorption; Adsorption characteristics; China; coal; Coalbed methane; Competitive adsorption; energy; H2S; heat; molecular dynamics; molecular models; Molecular simulation; occupations; temperature; China; Molecular simulation; H2S; Competitive adsorption; Adsorption characteristics; Coalbed methane
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.157447

•A combined experimental and molecular study was conducted to investigate the adsorption of H2S and CH4 in coal.•Both H2S and CH4 were found to follow Langmuir’s model, with their adsorption influenced by pressure and temperature.•Under identical conditions, H2S exhibited 2.43 times higher adsorption compared to CH4.•Molecular simulations revealed that H2S displayed a stronger affinity towards coal surfaces.•The presence of H2S in gas mixtures enhanced its own adsorption while reducing the adsorption of CH4. To investigate the adsorption characteristics and competitive adsorption patterns of H2S and CH4 in coal seams, we conducted a combined experimental and molecular simulation study using Ningxia Shuangma bituminous coal as the research subject. The experiments examined the adsorption of single-component H2S and CH4 gases at different temperatures and pressures, while the molecular model of bituminous coal was used to analyze the adsorption patterns of binary gas mixtures under competing conditions. Our experimental results demonstrate that both H2S and CH4 follow Langmuir’s model, with their saturated adsorption positively correlated with pressure but negatively correlated with temperature. Moreover, under identical conditions, H2S exhibits 2.43 times higher saturated adsorption than CH4. Molecular simulations reveal that temperature has a greater impact on H2S compared to CH4; both gases undergo reversible physisorption, where isosteric heat of adsorption decreases linearly with increasing amount of adsorbate molecules; interaction energy for H2S is larger in absolute value than that for CH4, indicating its stronger affinity towards coal surfaces; regarding binary component adsorption, an increase in proportion of H2S within the gas mixture leads to higher saturation adsorptions for both the mixture itself and individual H2S molecules while decreasing saturation adsorption for CH4; Coal adsorption selectivity factor for H2S/CH4 > 1. The preferential occupation of high-energy adsorption sites is more likely to be observed for H2S. The adsorption capacity and competitive adsorption capacity of H2S were greater than that of CH4.