Adsorption and Diffusion of Oxygen, Nitrogen, Methane and Argon in MolecularSieve Carbons

摘要

Equilibrium adsorption and diffusion data for oxygen, nitrogen, methane and argonin carbon molecular sieves 3A and 5A at 0C, 30C and 50C were obtained at pressures up to 13 Bar using a high-pressure Cahn electrobalance. On a molar basis, methane had the highest adsorption capacity among the four gases studied both in 3A and 5A molecular sieve carbons. Oxygen and nitrogen had approximately the same equilibrium adsorption capacity. Equilibrium adsorption data were represented by a Langmuir equation and the Vacancy Solution Model (VSM). The VSM appears to give a good fit of the experimental data while the representation of the experimental data by the Langmuir equation showed deviation, especially at high pressures. The isosteric heats of adsorption were found to increase slightly with an increase in surface coverage. The values were slightly higher on 3A than on 5A for all the gases except argon. Kinetic data showed that oxygen has the highest diffusion rate and methane the lowest. Diffusivities increased with temperature. Keywords: Adsorption; Diffusion rate; Molecular sieve carbons; Langmuir equation; Vacancy solution model; Kinetic data; Isotherm; Isosteric heat of adsorption. (JES)