Improved Pore-Size Analysis of Carbonaceous Adsorbents

Abstract

An improvement was proposed for the pore-size analysis of active carbons based on low-temperature (77 K) nitrogen adsorption isotherms measured over a wide range of relative pressures (5 × 10−7–0.995). It was shown that the applicability of the Barrett, Joyner and Halenda (BJH) computational method based on the Kelvin equation could be extended significantly towards small mesopores and large micropores when a proper t-curve was used to represent the film thickness of nitrogen adsorbed on the carbon surface. It was proposed that the aforementioned t-curve be obtained from the nitrogen adsorption isotherm at 77 K on a macroporous carbon black by fitting its multilayer part to the calibrated t-curve for nitrogen adsorbed at 77 K on a macroporous silica. To date, the Harkins–Jura or Halsey t-curves have been used to describe the pressure-dependence of the film thickness. This appears to be inaccurate, especially in the range of low relative pressures. It was shown that this inaccuracy makes the pore-size analysis questionable. However, the t-curve proposed in this work gave the pore-size distribution functions for the carbons studied thereby reproducing the total pore volume and showing realistic behaviour in the range at the borderline between micropores and mesopores.

Synthesis and adsorption properties of colloid-imprinted mesoporous carbons using poly(vinylidene chloride-co-vinyl chloride) as a carbon precursor

“…The pore size distribution (PSD) curves presented in Fig. 3 were calculated from adsorption branches by the improved BJH method (Choma et al 2002(Choma et al , 2008a using the statistical film thickness (t-curve) for the carbon surface, BP280 carbon black (Kruk et al 1997). Each of the plots consists of a very sharp and narrow peak corresponding to the micropores and a broader peak attributed to mesopores.…”

“…The BJH method is based on the Kelvin equation, which correlates the capillary condensation pressure and pore diameter. In this method we used the statistical film thickness for the Cabot BP280 carbon black (Kruk et al 1997), which was obtained by fitting the reference isotherm on this carbon to the multilayer range of the t-curve established on the basis of MCM-41 materials (Choma et al 2002).…”

Soft-templating synthesis and adsorption properties of mesoporous carbons with embedded silver nanoparticles

“…The pore size distributions (PSDs) were calculated from the adsorption branch of nitrogen adsorption-desorption isotherms using the Barrett-Joyner-Halenda (BJH) method (Barrett et al 1951) improved by Kruk-Jaroniec-Sayari (KJS) (Kruk et al 1997b;Jaroniec and Solovyov 2006;Choma et al 2002;Kruk et al 1996). The BJH method is based on the Kelvin equation, which correlates the capillary condensation pressure with the pore diameter.…”

Development of Microporosity in Mesoporous Carbons

“…The BJH method is based on the Kelvin equation, which correlates the capillary condensation pressure and pore diameter. In this method we used the statistical film thickness for the Cabot BP280 carbon black [55], which was obtained by fitting the reference isotherm on this carbon to the multilayer range of the t-curve established on the basis of MCM-41 materials [57]. The pore width at the maximum of the BJH pore size distribution was used for characterization of the samples studied.…”