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 (W0) and the characteristic energies (E). An experimental value of W0 equal to 0.184 cm3/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 W0 equal to 0.163 cm3/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.