Silicon carbide (SiC) nanotubes are elegant nanoporous materials with excellent properties, such as high thermal stability and high mechanical strength compared to their carboneous counterparts, carbon naotubes (CNT). Related to gas separation processes at high temperature and pressure, SiC nanotubes are of great interest in the advanced technological processes such as hydrogen production, hydrogen storage and supercritical adsoprtion separation. Understanding the effect of the structural factors (i.e, the nanotube diameter and chirality) that control adsorption and separation capability of these materials at high pressures and temperatures is of vital importance for improving the separation factor of both amorphous and crystaline SiC materials.

We employ atomistic simulations to examine the adsorption and diffusion of a variety of gases in SiC nanotubes as a function of the pressure, the tube diameter, and chirality. The impact of the nanotube structure on the self-diffusivities of N2, H2, CO2, methane and butane are evaluated in types (n,0) and (n,n) nanotubes. The self-diffusivites generally depend on the pressure; however, our simulations showed a marked effect of channel chirality on the pressure-dependence of the self-diffusivities. These insights are highly valuable for undestanding the transport properties, as well as for interpretation of separation capability of SiC-based nanotubes and membranes.