Copper sorbents which are resistant to the reduction by hydrogen are used as a guard bed for an acetylene conversion zone. The adsorbents include cuprous oxide, cupric oxide, copper metal, and a halide and are pre-reduced prior to be loaded into the guard bed. The sorbents can remove contaminants that would poison selective hydrogenation catalysts used for a selectively hydrogenating acetylenic compounds in an olefin stream. The sorbents may also selectively hydrogenate the acetylenic compounds.