The Characterization of Porous Solids by NMR

We are using a novel NMR method, that has been developed in our laboratory and employs the depression of the freezing point (Delta T-m) of confined liquid within porous media, to investigate the effect of pre-drying silica with average pore diameter ranging from 60 Angstrom to 1000 Angstrom. Cyclohexane was the confined liquid. Pre-drying was found to affect only the smallest pores. A study to compare partially filled and over-filled samples showed that the average Delta T-m for partially filled samples is greater than for over-filled. We have also investigated the use of water as the absorbed liquid and compared results with those obtained from cyclohexane studies. Reasonable agreement was found but cyclohexane was more sensitive, The method is fast and is suitable for monitoring pore size distributions in the range of 50-1000 Angstrom.