Carbon molecular sieves from hardwood carbon pellets. The influence of carbonization temperature in gas separation properties

The influence of carbonization temperature in the preparation of hardwood carbon molecular sieves (CMS) has been studied. The textural characterization of the obtained materials included adsorption isotherms of CO2, C2H6 and n-C4H10 to obtain the micropore size distribution. Adsorption kinetics of CH4, CO2, C3H6 and C3H8 were measured in all materials to determine their behavior as molecular sieves. Results confirm that the carbonization temperature of this hardwood has a very significant effect on the resulting CMS separation properties. The increase in the wood's carbonization temperature reduced the CMS micropore size distribution. Consequently, high carbonization temperatures (1000 °C) are required to obtain good CH4/CO2 separation, while a low carbonization temperature (700 °C) is best for C3H6/C3H8 separation. The differences in separation properties of these materials could be explained by a partial blocking of the micropore entrance produced by disorganized carbon migrating from the internal structure (chars) and by the additional binder used to prepare the CMS.