Atomic simulation of Xe and Kr separation in silica-templated amorphous mesoporous carbons CMK-3 and CMK-5

Abstract

We perform a molecular simulation study on adsorption and separation of the noble gases Xe and Kr in silica-templated amorphous mesoporous carbons (CMK) materials. We generate the atomic models of CMK-3 and CMK-5 materials by adsorbing carbon in a model MCM-41 pore. Our carbon structures can capture the surface roughness and the disordered nature of the carbon rods and carbon pipes as reported in the experiment. The adsorption isotherms and isosteric heats of pure gases have been examined further. We find that the existence of the carbon interconnections between nanorods for CMK-3 and between nanopipes for CMK-5 will reduce the excess uptakes of the noble gases, whereas the isosteric heats are favoured in the materials with interconnections. The carbon interconnections are not advantageous to the adsorption storage of pure gases, but they can improve the separation ability of Xe for gas-mixture adsorption. The effects of temperature and concentration on the Xe separation are investigated and it is shown that the selectivities of Xe in the CMK-5 materials are insensitive to the two factors. We also find that both gas storage and separation of CMK materials are comparable to IRMOF-1 and UMCM-1 metal-organic frameworks.

Keywords:

• Adsorption separation
• CMK-3 and CMK-5
• xenon and krypton