Purification of normal a-olefins by removal of dienes has been demonstrated previously in our laboratories by,T-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 H-2 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+-zeolitc, 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/H-2 at 120 degreesC 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.