Process for the removal of oxygen from a gas mixture comprising oxygen, at least one olefin, hydrogen, carbon monoxide and optionally at least one alkyne, the ratio of oxygen:hydrogen in the gas mixture being 1 part by volume of oxygen to at least 5 parts by volume of hydrogen. The process comprises contacting the gas mixture with a catalyst in a reaction zone under conditions sufficient to oxidise at least a portion of the hydrogen and to oxidize at least a portion of the carbon monoxide and without significant hydrogenation of the at least one olefin. The catalyst comprises at least one metal or oxide of a metal from the 10.sup.th group of the Periodic Table of Elements, the metal or oxide of the metal being supported on an oxide support, provided that the catalyst also comprises tin.