New acrylic monolithic carbon molecular sieves for O_2/N_2 and CO_2/CH_4 separations

摘要

The modification of activated carbon fibres prepared from a commercial textile acrylic fibre into materials with monolithic shape using phenolic resin as binder was studied. The molecular sieving properties for the gas separations CO_2/CH_4 and O_2/N_2 were evaluated from the gas uptake volume and selectivity at 100 s contact time taken from the kinetic adsorption curves of the individual gases. The pseudo-first order rate constant was also determined by the application of the LDF model. The samples produced show high CO_2 and O_2 rates of adsorption, in the range 3-35 x 10~ -3 s~ and in most cases null or very low adsorption of CH_4 and N_2 which make them very promising samples to use in PSA systems, or similar. Although the selectivity was very high, the adsorption capacity was low in certain cases. However, the gas uptake in two samples reached 23 cm~3 g~- for CO_2 and 5 cm~3 g~- for O_2, which can be considered very good. The materials were heat-treated using a microwave furnace, which is a novel and more economic method, when compared with conventional furnaces, to improve the molecular sieves properties.