A process for purifying various hydrocarbon streams using a composite adsorbent is disclosed. The adsorbent contains a zeolite, an alumina and a metal component. The metal component (M.sub.add) is present in an amount (over and above the amount of exchangeable M metal in the zeolite) at least 10 mole % the stoichiometric amount of metal (M) (expressed as the oxide) needed to balance the negative charge of the zeolite lattice. In a specific application an adsorbent comprising zeolite X, alumina and sodium is used to purify an ethylene stream in order to remove CO.sub.2, H.sub.2S, methanol, and other S- and O-containing compounds from the stream.