Quantifying the adsorption of flowing gas mixtures in porous materials by remote detection NMR

Traditional adsorption measurements are carried out at static conditions for a single gas component, and multi-component adsorption measurements are challenging and time-consuming. Here we introduce an efficient remote detection NMR method for in situ analysis of adsorption of flowing gas in mesoporous materials. We investigated adsorption of continuously flowing propane and propene gases as well as their mixture in packed beds of controlled pore glass and silica gel materials. Remote detection provided from 300 to 700 -fold sensitivity enhancement as compared to a direct experiment carried out by a large coil around the packed bed. The unique time-of-flight information obtained using this method was utilized in flow velocity determination, and the velocities were converted into amount of adsorbed gas. As the detection was performed outside the packed bed region, the spectra were not influenced by the porous materials. Because resonances of each gas component were well-resolved in the spectra, the amount of adsorption of each gas component could be determined from the same data, measured in a few minutes.