2019 Volume 58 Issue 6 Pages 633-643
The near infrared (NIR) spectroscopy has been applied to analyze the catalyst and adsorbent surfaces. Since H2O molecules were hardly stabilized on the SiO2 surface, the hydrogen bond networks of H2O cluster on the SiO2 surfaces was almost similar to liquid phase H2O. In contrast, H2O molecules were largely stabilized on the TiO2 or Al2O3 surfaces. Thus, the H2O clusters on the TiO2 or Al2O3 surfaces had more complicated hydrogen bond networks as compared to liquid phase H2O. We have further discussed the correlation between the hydrophilic/hydrophobic properties and the surface wettability. Then, the NIR measurements for the SiO2 and cellulose adsorbents grafted with organic functional groups clearly showed the typical absorption bands due to NH2, CH3, and CH2 groups. The alkyl or aminopropyl grafted SiO2 adsorbed drastically smaller amounts of H2O molecules as compared to the pristine SiO2. While the alkyl grafted cellulose showed still hydrophilic surface character because the pristine cellulose was highly hydrophilic. Finally, the NIR spectroscopy enabled the simultaneous analyses of NH3, NH4+ and H2O adsorbed on zeolite surfaces.
