非局域密度泛函理论表征活性炭孔径分布的改进算法

An improved method to determine PSD of activated carbon by using non-local density functional theory

为提高由NLDFT计算值确定活性炭孔径分布(PSD)的精度,根据测得的77K氮在非石墨化碳黑BP460和椰壳活性炭K05上的吸附数据,比较了吸附空间及壁面结构采取不同假设对计算结果的影响。结果表明,常规将活性炭吸附空间近似为无限尺寸的石墨化碳黑表面构成的狭缝孔,并由Lorenz-Berthelot混合法则确定相互作用参数,计算值在较低压力区域和试验值之间的偏差明显;而将吸附壁面结构近似为非石墨化碳黑,并由表面粗糙度和石墨晶格分布的误差函数修正相互作用参数后,计算结果和试验值吻合良好。分析结果时发现,归一化方法和考虑周边吸附质分子作用的加权函数是影响NLDFT计算结果准确性的关键因素。

For improving the accuracy of PSD of the activated carbon determined by non-local density functional theory（NLDFT）,adsorption isotherms of nitrogen at 77K on non-graphitized thermal carbon black BP460 and activated carbon were measured to evaluate the interaction parameters of fluid-fluid and fluid-solid.Results show that using a graphitized thermal carbon black as a reference system and fitting parameters by Lorenz-Berthelot mixing rule bring about a poor correlation between the results from experiment and the theory,however good correlations occur if the pore wall surface of the activated carbon is identical to a non-graphitized carbon black.Results also reveal that introduction of the surface roughness and the error function for the dispersion of the solid mass are beneficial to the accurate determination of interaction parameters.Conclusions are drawn that regularization method for determining the parameters from experimental adsorption isotherms is crucial to the accuracy of fluid-solid potentials,and those fitted under a reference system of a non-graphitized carbon black can be used to model adsorption in slit pores and generate a set of local isotherms,which can accordingly be used to determine the PSD function of activated carbon.