Recovery of propylene from off-gas of bulk polypropylene plants by pressure swing adsorption

Recovering propylene from the off-gas (C₃H₆/C₃H₈/N₂ ternary system) of polypropylene plants by pressure swing adsorption (PSA) with NJ adsorbent which was loaded with cuprous cation was studied. The static adsorption equilibrium of the C₃H₆/C₃H₈/N₂ ternary system on the NJ adsorbent was measured. The effects of different pressure, residence time and overhead process on the dynamic adsorption to propylene were investigated. The results show that the separation factor of propylene and propane is 1.72 under the conditions of residence time 2.4 min and adsorption pressure 0.6 MPa. The experimental results of PSA with three-column showed that the NJ adsorbent had good PSA performance at room temperature, the recovery of propylene reached more than 96% with the purity of more than 88% (φ).