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贾进章，邢迎欢，李斌，等. 基于蒙特卡罗的硫化氢吸附−扩散机理[J]. 煤炭学报，2024，49(2)：845−864. DOI: 10.13225/j.cnki.jccs.ST23.1285
引用本文: 贾进章，邢迎欢，李斌，等. 基于蒙特卡罗的硫化氢吸附−扩散机理[J]. 煤炭学报，2024，49(2)：845−864. DOI: 10.13225/j.cnki.jccs.ST23.1285
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JIA Jinzhang，XING Yinghuan，LI Bin，et al. Research on the adsorption-diffusion mechanism of hydrogen sulfide based on Monte Carlo simulation[J]. Journal of China Coal Society，2024，49(2)：845−864. DOI: 10.13225/j.cnki.jccs.ST23.1285
Citation: JIA Jinzhang，XING Yinghuan，LI Bin，et al. Research on the adsorption-diffusion mechanism of hydrogen sulfide based on Monte Carlo simulation[J]. Journal of China Coal Society，2024，49(2)：845−864. DOI: 10.13225/j.cnki.jccs.ST23.1285
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基于蒙特卡罗的硫化氢吸附−扩散机理

Research on the adsorption-diffusion mechanism of hydrogen sulfide based on Monte Carlo simulation

    摘要
  • 摘要: 为了明确硫化氢(H2S)在煤中吸附扩散的微观动力学机理，揭示不同温度、压力对煤吸附H2S分子吸附扩散特性的影响机制，基于巨正则蒙特卡罗(GCMC)、分子动力学(MD)和密度泛函理论(DFT)方法，利用Material Studio软件研究了温度在273.15～313.15 K、压力1～1 000 kPa时H2S在气肥煤大分子模型中的吸附扩散特征。结果表明：温度由273.15 K升至313.15 K时，H2S的饱和吸附量由38.34 mL/g降至31.85 mL/g，降低了16.93%，当压力为1 kPa时，温度对吸附量的影响最为敏感。温度为293.15 K时，压力由1 kPa升至1 000 kPa时，最可几相互作用能由−39.391 kJ/mol升至−34.301 kJ/mol，随着压力的增加，最可几相互作用能先快速增加，后缓慢增加。在吸附H2S过程中，H2S的等量吸附热在36.63～41.43 kJ/mol内，为物理吸附，等量吸附热随着吸附量的增加呈现出负指数变化；H2S的吉布斯自由能ΔG为−3.57～−24.57 kJ/mol，吸附熵ΔS为−0.126～−0.194 8 kJ/(mol·K)，随吸附量升高ΔG和ΔS的绝对值线性降低，H2S的吸附自发性和系统的混沌程度均降低。H2S与气肥煤的相互作用能为−492.47～−3 390.95 kJ/mol，以范德华能为主，占总能量的58.67%，以静电能为辅，占41.33%，随着吸附量的增加，相互作用能绝对值增加，吸附量与相互作用能的变化具有一致性。H2S与羧基的相互作用最强，羟基次之，H2S在—OH、—COOH、—C=O周围存在双层吸附。温度由273.15 K升至313.15 K，H2S分子的扩散系数由1.066×10−10 m2/s升至2.025×10−10 m2/s，温度升高会导致原本闭合的孔吼孔道打开，增加裂隙的连通性，温度升高，增加H2S分子平均自由程，使得H2S扩散能力增强，H2S扩散活化能为11.206 kJ/mol。H2S相对体积分数分布呈现多峰结构，H2S在气肥煤大分子模型中呈层状结构分布。H2S的极限吸附热为42.898 kJ/mol，H2S与煤体上—OH、—COOH、—C=O活性基团产生氢键作用，H2S在吸附初期存在微弱的化学吸附。

     

    Abstract: In order to clarify the microscopic dynamics mechanism of hydrogen sulfide (H2S) adsorption and diffusion in coal, and to reveal the influence mechanism of different temperatures and pressures on the molecular adsorption and diffusion characteristics of coal adsorbed H2S, based on the Giant Canonical Monte Carlo (GCMC), Molecular Dynamics (MD), and Density Functional Theory (DFT) methods, the adsorption-diffusion characteristics of H2S in the gas-fertilized coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 1 to 1 000 kPa were investigated using Material Studio software. The results showed that the saturated adsorption of H2S decreased from 38.34 mL/g to 31.85 mL/g at an increase in temperature from 273.15 K to 313.15 K, which is a 16.93% decrease. The effect of temperature on adsorption is most sensitive when the pressure is 1 kPa. The most significant interaction energy increased from −39.391 kJ/mol to −34.301 kJ/mol when the pressure was increased from 1 kPa to 1 000 kPa at a temperature of 293.15 K. With the pressure increased, the most significant interaction energy increased first rapidly and then slowly. During the adsorption of H2S, the isocratic heat of adsorption of H2S was in the range of 36.63−41.43 kJ/mol, which is a physical adsorption. The isocratic heat of adsorption showed a negative exponential change with increasing adsorption volume. The Gibbs free energy ΔG of H2S was from −3.57 to −24.57 kJ/mol, and the entropy of adsorption ΔS was from −0.126 to −0.194 8 kJ/(mol·K). The absolute values of ΔG and ΔS linearly decreased with increasing adsorption amount, and the adsorption spontaneity of H2S and the chaos of the system decreased. The interaction energy of H2S with gas-fertilized coal was ranged from −492.47 to −3 390.95 kJ/mol, which was dominated by van der Waals’ energy accounting for 58.67% of the total energy, and supplemented by electrostatic energy accounting for 41.33%. As the adsorption capacity increased, the absolute value of interaction energy increased, and the changes in adsorption capacity and interaction energy were consistent. H2S interacted most strongly with the carboxyl group, followed by the hydroxyl group. Double layer adsorption of H2S occurred around —OH, —COOH, —C=O. The temperature was increased from 273.15 K to 313.15 K. The diffusion coefficient of H2S molecules was increased from 1.066×10−10 m2/s to 2.025×10−10 m2/s, and the activation energy of diffusion was 11.206 kJ/mol. An increase in temperature can lead to the opening of previously closed pores and channels, increasing the connectivity of cracks. As the temperature rises, it increases the average free path of H2S molecules, enhancing their diffusion ability. The limiting heat of adsorption of H2S was 42.898 kJ/mol. The H2S concentration distribution showed a multi-peak structure, and H2S was distributed in a laminar structure in the gas-fertilized coal macromolecule model. H2S had hydrogen bonding with —OH, —COOH, and —C=O reactive groups on the coal body, and there was a weak chemisorption of H2S in the early stage of adsorption.

     

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