Physical adsorption of gases at high pressure. IV. An improvement of the Dubinin—Astakhov adsorption equation

Isotherms of adsorption of A, N3, CH4, and CO2 on molecular sieving carbon (MSC-5A) were measured at temperatures of 25, 50, and 75°C and pressures up to 170 atm. Further, low pressure adsorption studies of N2 on the same adsorbent were carried out at 0, −78, and −196°C to supplement the high pressure data. Experimental results showed that almost all high pressure adsorption isotherms had their respective maxima. This fact indicates that the observed adsorption is an apparent adsorption. Thus, taking the thermal expansion of an adsorbed phase into consideration, the true adsorption was evaluated from the observed apparent adsorption. Analyses of experimental data were carried out on the basis of the adsorption potential theory, and an improved form of Dubinin-Astakhov adsorption equation was proposed: InWWo = ∑n=1n=∞ kn(ϵβ)n. Predictions of the adsorption isotherms of high pressure gases on MSC-5A were carried out by means of the proposed method. The results demonstrated that the new adsorption equation is capable of predicting adsorption data obtained under wider ranges of experimental conditions.