Supercritical fluids in mesopores—new insight using NMR

Supercritical fluids are an essential constitute of modern chemical industry. However, their optimal use in processes involving porous solids is rather limited due to our poor knowledge about their transport properties under confinements. By using the non-invasive pulsed field gradient NMR method, we directly assessed molecular diffusivities of n-pentane in mesopores at sub- and supercritical temperatures. The obtained results ultimately point out that criticality in pores occurs at lower temperatures than in the bulk liquid surrounding the porous solid. The data on molecular diffusivities and pore density may be self-consistently quantified using simple gas-kinetic arguments.