ON THE ISSUE OF USING THE DUBININ–RADUSHKEVICH–ASTAKHOV EQUATION IN CALCULATING ISOTHERMS OF H2, CO2, CO IN THE PRESSURESWING ADSORPTION PROCESS FOR HYDROGENRECOVERY ON BLOCK ZEOLITES 13X

Abstract

The calculation of adsorption isotherms of synthesis gas components in the process of pres-sure swing adsorption (PSA) for hydrogen extractionon zeolite adsorbents is traditionally carried out using the Langmuir equation or equations derived from it. Its disadvantage consists in the necessity to obtain experimental adsorption isotherms for each gas in the gas mixture on the used adsorbent. This approach is expensive, especially in the case of multicomponent mixtures, such as synthesis gas. The paper demonstrates the prospects of an alternative method for calculating ad-sorption isotherms of H2, CO2, CO gases in the PSA process for hydrogen extracionfrom synthesis gas on block zeolites 13X using the Dubinin–Radushkevich–Astakhov (DRA) equation. Using zeo-lites 13X made by three samples, experimental adsorption isotherms of H2, CO2, CO at temperatures of 293 and 323 K, and adsorption isotherms of N2ata boiling point of 77.35 K were obtained. Using experimental isotherms, the problems of parametric identification were solved, and the parameters of the DRA equation for H2, CO2, CO gases on block zeolites 13X were determined. It has been found that the calculation of adsorption isotherms of H2, CO2, CO gases on zeolites 13X, the char-acteristics of which fall within the ranges of the limiting adsorption volume 0.258–0.296 cm3/g and the characteristic adsorption energy 10279–13395 J/mol, respectively, can be correctly carried out using the DRA equation in the temperature range of 293–323 K and the pressure range of 0–30 atm.In this case, the maximum value of the mismatch between the experimental gas isotherms and those calculated by the DRA equation is 14.69% for H2; the minimum value is 1.81% for CO2. Certain affinity coefficients make it possible to calculate the adsorption isotherms of H2, CO2, CO gases in the obtained ranges of the limiting adsorption volume and characteristic adsorption energy using only one isotherm of the standard gas (N2) on the zeolite 13X used. The versatility of the DRA equation can be used to calculate the adsorption isotherms of various gases, mixtures, and adsor-bents in cyclic adsorption processes.