Cu(I)-Y-zeolite as a superior adsorbent for diene/olefin separation

Purification of normal α-olefins by removal of dienes has been demonstrated previously in our laboratories by π-complexation using Ag⁺ ion-exchanged zeolite (Ag-Y) or AgNO₃/SiO₂ sorbent. Although Ag-Y could purify 1-butene/1,3-butadiene effectively, the purification performance was degraded by H₂ and/or H₂S poisoning. A new sorbent for 1-butene/1,3-butadiene purification was developed in this study by ion-exchange of Cu²⁺ cations into Y-zeolite followed by reduction of Cu²⁺ to Cu⁺. The performance of the Cu⁺-zeolite, Cu(I)-Y or Cu-Y, was found to be superior to that of Ag-Y. Cu-Y exhibited higher diene/ olefin separation factors than Ag-Y by approximately an order of magnitude. Furthermore, unlike Ag-Y, exposure to H₂S/H₂ at 120 °C had virtually no effect on 1,3-butadiene/1-butene adsorption, indicating the excellent poisoning resistance of Cu-Y. XPS and EPR analyses showed that half of the Cu²⁺ cations in Cu-Y underwent autoreduction to Cu⁺ either in vacuo or in He, resulting in the same purification capability with Cu-Y obtained by reduction with CO.