Carbon molecular sieve (show as right illustration) developed in the 1970s.It is type of new adsorbent as well as excellent non-polar carbon element material.The main component of carbon molecular sieves are elemental carbon show black solid cylinderical appearance wich contain a large quantity of micropores with a diameter of 0.28-0.36nm as well as a small quantity of macropores and mesopores (The macropres and mesopores are known as transition pore as well).As shown below,the specific surface area of micropore accounts for more than 90% of its total pore surface area and the specific surface area of the micropore exceed 1000m2/g normally.
The ability for air separation by carbon molecular sieve is relay on the diffusion rate of oxygen molecules and nitrogen molecules in the micropores of carbon molecular sieve.Due to the difference of relatived diffusion rate for various gas molecules of different dynamic diameter,therefore the components of gas mixtures can be separated effectively.
The internal micropore of commonly used carbon molecular sieves are between 0.28-0.36 nm.Oxygen dynamic diameter (0.346 nm) within the micropore size range,can quickly diffuse into the pore through the micropore orifice, while nitrogen dyniamic diameter (0.364 nm) is more difficult to pass through the micropore orifice, so that oxygen and nitrogen can be separated. Carbon dioxide dynamic diameter (0.33 nm) can also rapidly diffuse into the pore through the microporous orifice, which is a relatively strong adsorbed gas.