改进的密度泛函理论在活性炭孔径分布的应用

doi:10.3969/j.issn.0253-2417.2016.02.012

林产化学与工业 ›› 2016, Vol. 36 ›› Issue (2): 79-86.doi: 10.3969/j.issn.0253-2417.2016.02.012

改进的密度泛函理论在活性炭孔径分布的应用

王国栋¹, 蒋剑春^1,2, 孙康²

1. 南京林业大学化学工程学院, 江苏南京 210037;
2. 中国林业科学研究院林产化学工业研究所, 江苏南京 210042

收稿日期:2015-10-10 出版日期:2016-04-25 发布日期:2016-04-26
通讯作者: 蒋剑春,研究员,博士生导师,研究领域:生物质资源的综合利用研究;E-mail:bio-energy@163.com。 E-mail:bio-energy@163.com
作者简介:王国栋(1987—),男,新疆石河子人,博士生,主要从事活性炭孔道表征的应用研究
基金资助:
“十二五”国家科技支撑计划资助(2015BAD21B05);林业公益性行业科研专项(201404610);中国林科院林业新技术所基本科研业务费专项资金(CAFINT2013C02)

Application of Modified Density Functional Theory in Pore Size Distribution Model of Activated Carbon

WANG Guo-dong¹, JIANG Jian-chun^1,2, SUN Kang²

1. College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
2. Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China

Received:2015-10-10 Online:2016-04-25 Published:2016-04-26

摘要/Abstract

摘要： 为提高活性炭孔径分布模型的计算精度,以4种基于不同方法求解剩余自由能的密度泛函理论方法,计算孔径宽度在0.65~5 nm的狭缝孔对3种气体(CH₄,N₂和CO₂) 在压力为0.2~2 MPa,温度为298 K下的过剩吸附量,发现4种方法对CH₄和N₂气体计算结果相近,但对于CO₂气体,平均场近似法和泛函展开法的结果比加权密度近似法的结果偏低,说明对于CO₂气体,在自由能的计算中相互作用项的影响不可忽略,并且,经矩阵条件数分析,确定加权密度近似法WDA(Yu)在计算的精度和稳定性上都更适用于孔径分布地建立。使用6种数值方法对3种活性炭的3种气体吸附等温线拟合,结果表明,平均偏差均小于5%,且所建立的活性炭孔径分布模型可以对样品的微观结构进行半定量地比较。

关键词: 经典密度泛函理论应用, 平均场近似法改进, 多孔材料, 吸附积分方程, 孔径分布

Abstract: To improve the accuracy of Pore Size Distribution (PSD) for activated carbon, we adopt 4 kinds of Density Functional Theory (DFT) with different methods to calculate excess Helmholtz free energy. The excess adsorption of 3 kinds of gases (CH₄, N₂ and CO₂) in slit pore with the pore size in the range from 0.65 to 5 nm was obtained using the pressure of 0.2-2 MPa at 298 K. The results of methods are similar for CH₄ and N₂, but for CO₂, the results of MF and FMSA are underestimated comparing with the results of two DFT methods based on Weight Density Approximation. This means that correlation effect shall not be neglected in the excess Helmholtz free energy. WDA (Yu) with the smallest condition number of the kernel is more suitable for PSD study. Moreover, 6 numerical methods are used to fit 3 kinds of isotherms of 3 activated carbon samples with the average deviation between the fitting result and experiment data less than 5 %, and the required PSD models can be used to compare qualitatively for different samples.

Key words: application of classical density functional theory, modifications of mean field approximation, porous materials, adsorption integral equation, pore size distribution

中图分类号:

TQ35

王国栋, 蒋剑春, 孙康. 改进的密度泛函理论在活性炭孔径分布的应用[J]. 林产化学与工业, 2016, 36(2): 79-86.

WANG Guo-dong, JIANG Jian-chun, SUN Kang. Application of Modified Density Functional Theory in Pore Size Distribution Model of Activated Carbon[J]. Chemistry and Industry of Forest Products, 2016, 36(2): 79-86.

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改进的密度泛函理论在活性炭孔径分布的应用

Application of Modified Density Functional Theory in Pore Size Distribution Model of Activated Carbon

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