A system and process for acetylene selective hydrogenation of an ethylene rich gas stream. An ethylene rich gas supply comprising at least H2S, CO2, CO, and acetylene is directed to a first treatment unit for removing H2S and optionally CO2 from the gas stream. A CO oxidation reactor is used to convert CO to CO2 and form a CO-depleted gas stream. A second treatment unit removes the CO2 from the CO-depleted gas stream and an acetylene selective hydrogenation treats the CO-depleted gas stream.