Adsorption of carbon dioxide at high pressure over H-ZSM-5 type zeolite. Micropore volume determinations by using the Dubinin-Raduskevich equation and the "t-plot" method

In this paper, a study of the adsorption of carbon dioxide at high pressure and at the temperatures of 273 K and 293 K in H-ZSM-5 zeolite is reported. The results show that the measured adsorption isotherms obey the Dubinin-Raduskevich equation and the invariance condition of temperature is fulfilled. This implies that adsorption in this zeolite is not a surface process, but is rather a volume filling. The proposed methodology for the analysis of the experimental adsorption data allows the determination of the micropore volume (W-0) and the characteristic energies (E). An experimental value of W-0 equal to 0.184 cm(3)/g is obtained in good agreement with the literature. The "t-plot" method, adapted for the first time in this work to the adsorption of carbon dioxide is also used in order to calculate the micropore volume. A value of W-0 equal to 0.163 cm(3)/g is obtained in very good agreement with those found using the "t-plot" method and the universal t-equation for the adsorption of nitrogen at 77 K. (C) 2007 Elsevier Inc. All rights reserved.