Zhang Bo, Liu Ping, Huang Zhuoran, Liu Jingji
College of Safety Engineering, Chongqing University of Science and Technology, Chongqing 401331, PR China.
Hangzhou Dianrun Chemical Co., LTD, Hangzhou 311200, PR China.
ACS Omega. 2023 Mar 9;8(11):10303-10313. doi: 10.1021/acsomega.2c07910. eCollection 2023 Mar 21.
Coal-based activated carbon is an ideal adsorbent for concentrating CH from coalbed methane and recovering CO from industrial waste gas. In order to upgrade the environmentally protective preparation technology of coal-based activated carbons and clarify the adsorption equilibrium and diffusion rules of CH, CO, and N in these materials, we prepared granular activated carbon (GAC) via air oxidation, carbonization, and physical activation using anthracite as the raw material. Also, we measured the adsorption isotherms and adsorption kinetic data of GAC by the gravimetric method and characterized its surface chemical properties. According to the results, GAC had abundant micropore structures with a pore size mainly in the range of 5.0-10.0 Å, and its surface was covered with plentiful oxygen-containing functional groups. The specific pore structure and surface chemical properties could effectively improve the separation and purification effects of GAC on CH and CO. In the temperature range of 278-318 K, the equilibrium separation of CH/N by GAC with a coefficient between 3 and 4 could be achieved. Also, the CO/CH separation coefficient decreased with the increase in temperature but remained around 3. The bivariate Langmuir equation could describe the adsorption behaviors of GAC on CH/N, CO/N, and CH/CO. With the increase in the concentrations of CH and CO in the gas phase, the difference between the adsorption capacity of CH or CO and that of N became greater. The change of the gas ratio did not affect the characteristics of preferential adsorption of CH and CO. At different temperatures (278, 298, and 318 K), the diffusion coefficients of CH, N, and CO at various pressure points showed predominately a small variation without an obvious trend. These results demonstrated that the separation of CH/N, CO/N, and CH/CO by the activated carbon could only rely on the equilibrium separation effect rather than the kinetic effect.
煤基活性炭是从煤层气中浓缩CH以及从工业废气中回收CO的理想吸附剂。为了提升煤基活性炭的环保制备技术，并阐明CH、CO和N在这些材料中的吸附平衡及扩散规律，我们以无烟煤为原料，通过空气氧化、碳化和物理活化制备了颗粒活性炭（GAC）。此外，我们采用重量法测定了GAC的吸附等温线和吸附动力学数据，并对其表面化学性质进行了表征。结果表明，GAC具有丰富的微孔结构，孔径主要在5.0 - 10.0 Å范围内，其表面覆盖有大量含氧官能团。特定的孔结构和表面化学性质能够有效提高GAC对CH和CO的分离提纯效果。在278 - 318 K温度范围内，GAC对CH/N的平衡分离系数在3至4之间。此外，CO/CH分离系数随温度升高而降低，但仍保持在3左右。二元朗缪尔方程可以描述GAC对CH/N、CO/N和CH/CO的吸附行为。随着气相中CH和CO浓度的增加，CH或CO与N的吸附容量差值变得更大。气体比例的变化不影响CH和CO的优先吸附特性。在不同温度（278、298和318 K）下，CH、N和CO在各压力点的扩散系数变化较小，无明显趋势。这些结果表明，活性炭对CH/N、CO/N和CH/CO的分离仅依赖于平衡分离效应，而非动力学效应。
