Process to prepare a diluted hydrogen gas mixture

A process to prepare a diluted hydrogen gas mixture starting from a gas mixture comprising hydrogen and carbon monoxide by

• (i) converting part of the carbon monoxide in said gas mixture to hydrogen and carbon dioxide by means of a catalyzed water gas shift reaction to obtain a shifted gas;
• (ii) separating hydrogen from said shifted gas by means of a membrane to obtain the hydrogen comprising gas at the permeate side of the membrane and a carbon dioxide comprising gas at the retentate side of the membrane, wherein at the permeate side of the membrane a sweep gas comprising nitrogen, steam or natural gas or a mixture thereof is provided;
• (iii) cooling the carbon dioxide comprising gas to obtain liquid carbon dioxide and a gas mixture of non-condensable gasses;
• and
• (iv) separating the liquid carbon dioxide from the non-condensable gasses;
• wherein the non-condensable gasses are used to supplement the sweep gas at the permeate side of the membrane in step (ii).