Adsorption study of CO2/CH4 and CO2/N2 binary mixtures on titanosilicates ETS-10 and SrETS-10; industrial application aspects

Abstract

Despite the outstanding features of the titanosilicate ETS-10 and some studies done on CO2 adsorption so far, there is a lack of coherent information to evaluate its potential industrial application in CO2 separation from natural gas and flue gas. In this work, ETS-10 and SrETS-10 were synthesized and characterized by PXRD, SEM, DTA, EDX, and BET. Pure gas adsorption isotherms of CO2, CH4, and N2 at 298 K were obtained by the constant-volume method. The obtained adsorption data were fitted with Langmuir and UNILAN isotherm models. The CO2/CH4 selectivity (yCO2 = 0.05) predicted by Ideal Adsorption Solution Theory (IAST) was 67.54 and 35.65 for ETS-10 and SrETS-10, respectively, while the CO2/N2 selectivity (yCO2 = 0.04) was 94.64 and 99.94. The Pseudo-Nth-Order (PNO) and micropore diffusion model were used to evaluate the CO2 adsorption kinetics and diffusivity of the adsorbents. The results showed that both ETS-10 and SrETS-10 exhibited fast kinetics for CO2 adsorption, but SrETS-10 had a slightly smaller diffusion coefficient (DC/rC2 = 0.01494 and 0.01458 s−1 for ETS-10 and SrETS-10, respectively) resulting in a slower adsorption rate than ETS-10. The regenerability of ETS-10 and SrETS-10 was studied and it was found that for ETS-10 about 79.07% and 96.32% of the capacity can be regenerated by applying vacuum and heating, respectively and also 79.67% of the SrETS-10 capacity can also be regenerated by applying vacuum. From the results of this work with an approach of industrial application, it was concluded that ETS-10 and SrETS-10 can be used in a combined PSA and TSA process for CO2 separation.