An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

doi:10.1016/j.cjche.2017.09.021

Chinese Journal of Chemical Engineering ›› 2018, Vol. 26 ›› Issue (3): 551-559.DOI: 10.1016/j.cjche.2017.09.021

• Chemical Engineering Thermodynamics • 上一篇下一篇

An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

Guodong Wang^1,2, Jianchun Jiang^1,3, Kang Sun³, Jianzhong Wu²

1 College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
2 Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA;
3 Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry, Nanjing 210042, China

收稿日期:2017-06-03 修回日期:2017-09-22 出版日期:2018-03-28 发布日期:2018-04-18
通讯作者: Jianzhong Wu
基金资助:
Supported by the National Sci-Tech Support Plan (2015BAD21B05) and China Scholarship Council (201408320127).

An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

Guodong Wang^1,2, Jianchun Jiang^1,3, Kang Sun³, Jianzhong Wu²

1 College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
2 Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA;
3 Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry, Nanjing 210042, China

Received:2017-06-03 Revised:2017-09-22 Online:2018-03-28 Published:2018-04-18
Contact: Jianzhong Wu
Supported by:
Supported by the National Sci-Tech Support Plan (2015BAD21B05) and China Scholarship Council (201408320127).

摘要/Abstract

摘要： Amorphous carbon materials play a vital role in adsorbed natural gas (ANG) storage. One of the key issues in the more prevalent use of ANG is the limited adsorption capacity, which is primarily determined by the porosity and surface characteristics of porous materials. To identify suitable adsorbents, we need a reliable computational tool for pore characterization and, subsequently, quantitative prediction of the adsorption behavior. Within the framework of adsorption integral equation (AIE), the pore-size distribution (PSD) is sensitive to the adopted theoretical models and numerical algorithms through isotherm fitting. In recent years, the classical density functional theory (DFT) has emerged as a common choice to describe adsorption isotherms for AIE kernel construction. However, rarely considered is the accuracy of the mean-field approximation (MFA) commonly used in commercial software. In this work, we calibrate four versions of DFT methods with grand canonical Monte Carlo (GCMC) molecular simulation for the adsorption of CH₄ and CO₂ gas in slit pores at 298 K with the pore width varying from 0.65 to 5.00 nm and pressure from 0.2 to 2.0 MPa. It is found that a weighted-density approximation proposed by Yu (WDA-Yu) is more accurate than MFA and other non-local DFT methods. In combination with the trapezoid discretization of AIE, the WDA-Yu method provides a faithful representation of experimental data, with the accuracy and stability improved by 90.0% and 91.2%, respectively, in comparison with the corresponding results from MFA for fitting CO₂ isotherms. In particular, those distributions in the feature pore width range (FPWR) are proved more representative for the pore-size analysis. The new theoretical procedure for pore characterization has also been tested with the methane adsorption capacity in seven activated carbon samples.

关键词: Non-local density functional theory, Amorphous porous materials, Pore size characterization, Gas adsorption, Adsorption integral equation

Abstract: Amorphous carbon materials play a vital role in adsorbed natural gas (ANG) storage. One of the key issues in the more prevalent use of ANG is the limited adsorption capacity, which is primarily determined by the porosity and surface characteristics of porous materials. To identify suitable adsorbents, we need a reliable computational tool for pore characterization and, subsequently, quantitative prediction of the adsorption behavior. Within the framework of adsorption integral equation (AIE), the pore-size distribution (PSD) is sensitive to the adopted theoretical models and numerical algorithms through isotherm fitting. In recent years, the classical density functional theory (DFT) has emerged as a common choice to describe adsorption isotherms for AIE kernel construction. However, rarely considered is the accuracy of the mean-field approximation (MFA) commonly used in commercial software. In this work, we calibrate four versions of DFT methods with grand canonical Monte Carlo (GCMC) molecular simulation for the adsorption of CH₄ and CO₂ gas in slit pores at 298 K with the pore width varying from 0.65 to 5.00 nm and pressure from 0.2 to 2.0 MPa. It is found that a weighted-density approximation proposed by Yu (WDA-Yu) is more accurate than MFA and other non-local DFT methods. In combination with the trapezoid discretization of AIE, the WDA-Yu method provides a faithful representation of experimental data, with the accuracy and stability improved by 90.0% and 91.2%, respectively, in comparison with the corresponding results from MFA for fitting CO₂ isotherms. In particular, those distributions in the feature pore width range (FPWR) are proved more representative for the pore-size analysis. The new theoretical procedure for pore characterization has also been tested with the methane adsorption capacity in seven activated carbon samples.

Key words: Non-local density functional theory, Amorphous porous materials, Pore size characterization, Gas adsorption, Adsorption integral equation

Guodong Wang, Jianchun Jiang, Kang Sun, Jianzhong Wu. An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption[J]. Chinese Journal of Chemical Engineering, 2018, 26(3): 551-559.

Guodong Wang, Jianchun Jiang, Kang Sun, Jianzhong Wu. An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption[J]. Chin.J.Chem.Eng., 2018, 26(3): 551-559.

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An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

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