Abstract: The molar ratio of hydrogen and carbon monoxide in synthesis gas is changed by partially condensing at least a portion of the feed gas and separating the partially condensed feed mixture by non-fractionating phase separation. Preferably, the partially condensed feed mixture is separated by a first phase separation into a first liquid stream and a first vapor stream; the first vapor stream is partially condensed and separated by a second phase separation into a second liquid stream and a second vapor stream; the second vapor stream is warmed and expanded to provide refrigeration and partial condensation; and the expanded partially condensed stream is separated by a third phase separation to provide a third liquid stream and a third vapor stream. The synthesis gas product is at least partially derived from the third liquid stream and a portion of the third vapor stream.