A process for removing gaseous contaminants from a feed gas stream that comprises a gaseous product and gaseous contaminants, comprising: providing the feed gas stream, cooling the feed gas stream to a temperature at which liquid phase contaminant is formed as well as a gaseous phase rich in gaseous product, separating the two phases by means of a gas/liquid separator, and introducing the gaseous phase rich in gaseous product into a cryogenic separation device that comprises a freezing zone and a distillation zone positioned below the freezing zone, and removing from the cryogenic separation device a bottom stream rich in liquid phase contaminant and lean in gaseous product, and a top stream rich in gaseous product and lean in gaseous contaminant. The invention further includes a device for carrying out the present process, the purified gas stream, and a process for liquefying a feed gas stream.