IR SPECTRA OF ADSORPTION ON SILICA GEL FOR ACETONITRILE, TETRAHYDROFURAN, DIETHYL ETHER AND METHANOL-d DILUTED IN SUPERCRITICAL CARBON DIOXIDE

Recently, we used a Fourier transform infrared (FTIR) spectroscopic technique for investigating the molecular states of the physically adsorbed organic solvents (methanol, acetone or triethylamine) diluted in supercritical CO 2 on hydroxyl group (SiOH) of a silica gel surface as a function of pressure (Jin et al., 1996). In the present work, additional spectral data are presented by altering the organic solvents into acetonitrile, tetrahydrofuran, diethyl ether and methanol-d. The tetrahydrofuran and diethyl ether have the same ether oxygen atom, but they are different in structure, cyclic or linear. Acetonitrile is known to form weak hydrogen-bonds with OH groups. The methanol-d is chosen to investigate the fraction of the surface OH groups because the exchange reaction of the OD and the OH groups occurs at room temperatures (Hambleton et al., 1965; Kiselev and Lygin, 1962)