Effective adsorptive removal of trace CO2 from olefin using alkanolamine-polyethylenimine-functionalized fumed silica

The purification of gaseous olefins, such as C 2 H 4 and C 3 H 6 , requires the efficient removal of trace CO 2 impurities. However, the development of ideal adsorbents with high CO 2 /olefin selectivity has remained a challenge. In this study, we synthesized a novel adsorbent, denoted as PEI/DEA@FS, by modifying fumed silica (FS) with a combination of polyethylenimine (PEI) and diethanolamine (DEA). At 298 K and 0.0004 bar, PEI/DEA@FS presented the highest CO 2 adsorption capacity among previously studied adsorbents, with a value of 2.12 mmol/g. Notably, PEI/DEA@FS demonstrated very high ideal adsorption solution theory selectivity for CO 2 /C 2 H 4 (>10 10 ) and CO 2 /C 3 H 6 (>10 7 ) at 298 K and 0.01 bar. Breakthrough experiments revealed its excellent separation performance, producing olefins (C 2 H 4 and C 3 H 6 ) with ultra-high purity (>99.9%) from a CO 2 /olefin (1/99) mixture. Moreover, PEI/DEA@FS exhibited outstanding stability over 20 adsorption and desorption cycles, and its CO 2 adsorption performance remained almost unchanged under 75% relative humidity in the feed stream.