CO2／N2／O2及H2O分子在褐煤中的吸附行为模拟
Simulation of the adsorption behavior of CO2 / N2 / O2 and H2 O molecules in lignite
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摘要: 为考察 CO2 ，N2 ，O2 气体和 H2 O 分子与褐煤中含氧官能团的吸附机理，采用密度泛函理 论(DFT)和巨正则蒙特卡罗(GCMC)模拟方法，对褐煤中各含氧官能团的静电势、CO2，N2，O2 和 H2 O分子与褐煤中含氧官能团的吸附能、气体在褐煤中的吸附等温线、等量吸附热及扩散系数进行 了研究。 结果表明:各含氧官能团静电势最大值的大小顺序为 Ph—OH>Ph—COOH>R—COOH> R—OH>Ph(R)—C=O>R2—C=O>Ph—O—R>R—O—R;最小值的大小顺序为 Ph—O—R>Ph— OH>R—O—R>Ph—COOH>R—COOH>R2—C=O>Ph(R)—C=O>R—OH。 吸附能计算结果表 明，H2O分子与各含氧官能团的吸附稳定性大于N2，O2，CO2。 由于H2O分子与—COOH之间存在 双氢键，导致 H2 O 分子与—COOH 的吸附稳定性强于与—OH，—O—以及—C=O 的吸附稳定性。 对于基团—OH 和—O—，当 O 原子未与苯环相连时，O 原子更易成为氢键受体。 与—OH， —O—，—C=O 相比，—COOH 与 N2 ，O2 和 CO2 分子的吸附能力较强。 除 R2 —C 程敢，李玉龙，张梦妮，等.CO2 /N2 /O2 及 H2O 分子在褐煤中的吸附行为模拟J.煤炭学报，2021，46(S2):960-696. 作者中心 专栏征稿 征稿方向 投稿须知 下载中心 专家中心 审稿指南 自荐审稿 在线期刊 过刊浏览 网络首发 下载排行 双语出版Abstract: In order to investigate the adsorption mechanism of N2 ，O2 ，CO2 ，H2 O molecules on oxygen⁃containing func⁃ tional groups (OFGs) of lignite，the density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulation method were used to study the electrostatic potential (ESP) of OFGs，the adsorption energy of H2O，N2，O2， CO2 molecules and OFGs，and the adsorption isotherms，isosteric adsorption heat，diffusion coefficients of N2，O2，CO2 in lignite.The results show that the order of the maximum ESP of each OFG is Ph—OH>Ph—COOH>R—COOH>R— OH>Ph(R)—C =O>R2—C=O>Ph—O—R>R—O—R;the order of the minimum ESP is Ph—O—R>Ph—OH> R—O—R>Ph—COOH>R—COOH>R2—C=O>Ph(R)—C=O>R—OH.The adsorption energy calculation results show that the adsorption stability of H2 O and OFGs is greater than that of N2 ，O2 ，and CO2 .Double hydrogen bonds ex⁃ ist between H2 O and —COOH，resulting the adsorption stability of H2 O and —COOH is more stable than that of H2 O and —OH，—O—，—C=O.For—OH and —O— groups，the O atom is easy to act as the hydrogen bond receptor when it is not connected to the benzene.Compared with —OH，—O— and —C=O，—COOH has the strongest adsorption capacity for CO2 ，O2 and N2 .Except for R2 —C=O and Ph—OH，the absolute value of adsorption energy of CO2 and each OFG is greater than that of O2;except for R—O—R，the absolute value of the adsorption energy of O2 and each OFG is greater than that of N2.The relationship between the adsorption amount of gas molecules in lignite is CO2 >O2 >N2 at the same pressure and temperature;the adsorption capacity of gases decreases at 298 K to 348 K.The adsorption isotherms of the three gases in the lignite structure model are in good agreement with Langmuir adsorp⁃ tion model.At the temperature of 298 K，323 K，and 348 K，the isosteric adsorption heat of CO2 is between 31- 32 kJ / mol，and the isosteric adsorption heats of O2 and N2 are between 18-20 kJ / mol.Molecular dynamics calculation results show that the diffusion coefficient (D) of CO2，O2，N2 molecules in the lignite structure model is 1.0×10-5，8. 78×10-5 and 1.17×10-4 cm2 / s，respectively.
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