Carbon molecular sieves for gas separation processes

The development and commercialization of carbon molecular sieves (CMS) are closely connected with the development of pressure swing adsorption (PSA) processes for the separation of gases. It was already known in the 1960s that certain carbonaceous materials have a molecular sieving effect similar to that of the well known zeolitic molecular sieves. The effect was observed during basic research on anthracite and bituminous coal which are both known to be porous. However, the separation effect, e.g. for oxygen/nitrogen, was very small. It was not until the 1970s that large-scale production of uniform quality CMS suitable for commercial application in PSA processes was established. Nowadays, different types of CMS are successfully used in PSA plants, e.g. for the generation of nitrogen from air, for the production of methane from biogases, and for the recovery of hydrogen from coke oven and steam reforming gases^1–4.