Gas separation techniques
Gas separation and liquefaction

This recent technique uses so-called semi-permeable membranes, which have the property of allowing certain molecules to pass through more easily than others (selective permeation). Selectivity is not solely a function of molecule size, which however plays a major role when sizes are very different: the case of obtaining pure hydrogen from mixtures containing N ₂ , CH ₄ , CO, Ar, etc. The hydrogen that has passed through the membrane constitutes the permeate; its purity can reach 99.9%.

Figure 2 shows the components that make up...