甲烷在层状石墨烯和活性炭上的吸附平衡

以吸附式天然气（ANG）吸附剂的工程应用为目的，以0-10 MPa、283.15-303.15 K甲烷在层状石墨烯（GS（3D），比表面积2062 m²/g）和活性炭SAC-01（比表面积1507 m²/g）上的吸附平衡数据作分析。首先，在77.15 K下由氮气吸附表征样品的孔径大小及分布（PSD）和比表面积。其次，选择极低压力下的吸附平衡数据标定亨利定律常数，确定甲烷在两吸附剂上的极限吸附热，并由维里方程和10-4-3势能函数计算甲烷与两吸附剂壁面之间的相互作用势。最后，依据测试的甲烷在吸附剂上的高压吸附平衡数据，比较了Langmuir系列方程的关联数据后的拟合精度，并由绝对吸附量计算了甲烷的等量吸附热。结果表明，甲烷在GS（3D）和活性炭SAC-01上的平均极限吸附热为23.07、20.67 kJ/mol；283.15 K下甲烷分子与GS（3D）和活性炭SAC-01之间的交互作用势ε_sf/k为67.19、64.23 K，与洛伦混合法则的计算值64.60 K相近；Toth方程关联甲烷在活性炭SAC-01和GS（3D）上吸附平衡数据的拟合累计相对误差为0.25%和2.29%；甲烷在活性炭SAC-01和GS（3D）上的等量吸附热平均值为16.8和18.3 kJ/mol。相对于活性炭SAC-01，比表面积和微孔容积均较高的GS（3D）对甲烷的吸附更具有优势。

Adsorption equilibrium of methane on layered graphene sheets and activated carbon

In order to develop a new kind of adsorbent for the storage of natural gas by adsorption, the activated carbon SAC-01 and the layered graphene GS(3D), which have a specific surface area about 2062 m²/g and 1507 m²/g, respectively,were comparatively studied as per adsorption equilibrium data measured at the temperature of 283.15-303.15 K and the pressure of 0-10 MPa. The pore size distribution (PSD) and BET specific surface area of the GS(3D) and the activated carbon were firstly determined by analyzing adsorption isotherms of nitrogen at 77.15 K through Horvath-Kawazoe equation calculation. The Henry law constant was used to calculate the limit isosteric heat of methane adsorption in correspondence with the low surface coverage, the interaction potentials between methane molecule and the surface of two adsorbents were then plotted by employing Virial equation and 10-4-3 potential function. The adsorption data, which were volumetrically measured under high pressures, were correlatively fitted by Langmuirian equations through nonlinear regression. Toth equation with the highest accuracy in predicting adsorption data was then used to calculate the absolute adsorption amount, which was finally employed to calculate the isosteric heat of adsorption via Clausius-Clapeyron equation. The result shows that the limit isosteric heat of methane adsorption on the GS(3D) and the activated carbon is about 23.07 and 20.67 kJ/mol, respectively, and the corresponding interaction potential ε_sf/k between methane molecule and the GS(3D) or the activated carbon is about 67.19 and 64.23 K at temperature 283.15 K, respectively, which are similar to 64.60 K determined by Lorenz-Berthelot mixing law. The accumulated relative error of the Toth equation for predicting the adsorption equilibrium of methane on the activated carbon and GS(3D) is 0.25% and 2.29%, respectively, and the mean isosteric heat of methane adsorption on the GS(3D) and the activated carbon is about 18.3 and 16.8 kJ/mol, respectively. It suggests that the GS (3D) with a larger specific surface area and micro-pore volume takes more advantages in methane adsorption in comparing with the activated carbon.