Pore size distribution model derived from a modified DR equation and simulated pore filling for nitrogen adsorption at 77 K Original Research Article

The Dubinin–Radushkevich (DR) equation has been used extensively to characterize microporous materials. However, it assumes a continuous pore filling mechanism and does not reduce to Henry’s law at low adsorptive pressures. In this study, we modify the DR equation by introducing adsorption density and the correlation between pore filling pressure and critical pore size for N2 adsorption at 77 K. This modified DR equation is used as the local isotherm in the generalized adsorption isotherm (GAI) to interpret N2 adsorption isotherm at 77 K. To solve the GAI, a modified normal distribution is developed and used as a distribution function of pore size on the domain [0, ∞). Pore size distribution (PSD) analyses of several adsorbent samples are carried out using this model. The results are found comparable with other popular PSD methods (e.g. MP, JC, HK and DFT).