Adsorption separation of carbon dioxide, methane and nitrogen on monoethanol amine modified beta-zeolite

A new type of composite adsorbents was synthesized by incorporating monoethanol airline (MEA) into beta-zeolite. The parent and MEA-functionalized beta-zeolites were characterized by X-ray diffraction (XRD), N-2 adsorption, and thermogravimetric analysis (TGA). The adsorption behavior of carbon dioxide (CO2), methane (CH4), and nitrogen (N-2) on these adsorbents was investigated at 303 K. The results show that the structure of zeolite was well preserved after MEA modification. In comparison with CH4 and N-2, CO2 was preferentially adsorbed on the adsorbents investigated. The introduction of MEA significantly improved the selectivity of both CO2/CH4 and CO2/N-2, the optimal selectivity of CO2/CH4 can reach 7.70 on 40 wt% of MEA-functionalized beta-zeolite (MEA(40)-beta) at 1 atm. It is worth noticing that a very high selectivity of CO2/N-2 of 25.67 was obtained on MEA(40)-beta. Steric effect and chemical adsorbate-adsorbent interaction were responsible for such high adsorption selectivity of CO2. The present MEA-functionalized beta-zeolite adsorbents may be a good candidate for applications in flue gas separation, as well as natural gas and landfill gas purifications.