Removal of C2H4 from a CO2 Stream by Using AgNO3-Modified Y-Zeolites

Removal of C 2 H 4 from a CO 2 stream is very important in ultrapurification of CO 2 for its application and utilization. However, it is difficult to remove C 2 H 4 completely from a CO 2 stream via conventional cryogenic distillation because the volatility of C 2 H 4 is similar to that of CO 2 . Another choice is the catalytic combustion method, but it is an energy-inefficient process, especially when it is coupled with the cryogenic distillation. Selective adsorption for removing C 2 H 4 might be a promising alternative. A great effort has been made in C 2 H 4 /C 2 H 6 separation and recovery of C 2 H 4 . There were, however, few reports about the removal of a trace amount of C 2 H 4 from a CO 2 stream. In this study, the AgNO 3 -modified NaY and HY zeolites are prepared and their adsorption performances are evaluated via a series of experiments of fixed-bed adsorption, frontal chromatographic adsorption, and temperature-programmed desorption (TPD). The structure of the sliver salt after being impregnated onto the supports has been characterized by thermogravimetric/differential thermal analysis, X-ray diffraction, and transmission electron microscopy. The experimental results show that both NaY and HY have poor adsorption selectivities of C 2 H 4 from the C 2 H 4 /CO 2 stream because of a stronger competition of CO 2 with C 2 H 4 for the physical adsorption sites, and AgNO 3 /NaY and AgNO 3 /HY, favored by their strong chemical adsorption sites, Ag ions, are able to remove C 2 H 4 from the CO 2 stream effectively.