A process for obtaining purified carbon monoxide from a gaseous mixture of hydrogen and carbon monoxide and one or more additional impurities to be removed by one or more vapor-liquid separation devices is provided which includes the steps of providing a feed stream of the gaseous mixture, cooling and partially condensing the feed stream to partially separate the feed stream into at least one hydrogen rich vapor substream and at least one carbon monoxide rich liquid substream, withdrawing a first and a second substream from one of the carbon monoxide rich substreams, passing the first substream through a first expansion valve to let down the pressure to a pressure nominally the same as that of a vapor-liquid separation device downstream, vaporizing the second substream using a heat exchange device to produce a third substream at a pressure substantially above that of the vapor-liquid separation device, passing the third substream through a work extraction device to provide a substantial portion of all refrigeration for cooling for the process, feeding the third substream to the vapor-liquid separation device, and withdrawing substantially purified carbon monoxide from the vapor-liquid separation device. A similar apparatus is also disclosed.