Method and apparatus for making ultra-pure hydrogen

Ultra-high purity hydrogen is produced from a hydrogen stream containing impurities including carbon monoxide and carbon dioxide, by first depleting the stream of carbon monoxide and carbon dioxide, than passing it through a semipermeable membrane such as a palladium-silver membrane, to remove methane, water and other impurities. Preferably, a methanation catalyst is used in the first step to convert the carbon monoxide and carbon dioxide to methane and water. This stream, free of carbon monoxide and carbon dioxide, is then passed through the semipermeable membrane to separate the remaining impurities.