Titania outgassing

The experimental material was a sample of rutile on which a layer of tnicrocrystalline titania had been deposited. Isotherms of nitrogen were determined on the original material outgassed at 1S0°C and on samples that had been outgassed at 25°, 150° or 250°C respectively after being charged with n-nonane. 

Fig. 4.15 a,-plots for the adsorption of nitrogen on a sample of microporous titania, before and after nonane treatment. Curve (A), before nonane pre-adsorption curves (B), (C), (D) after nonane pre-adsorption, followed by outgassing at (B) 250° (C) 150°C (D) 25°C. The a,-plots were based on standard nitrogen isotherms having the same c-values as the isotherms of... 

A detailed study of the physical and chemical adsorption of water on three xerogels, ferric oxide, alumina and titania, as well as on silica (cf. p. 272) has been carried out by Morimoto and his co-workers. Each sample was outgassed at 600°C for 4 hours, the water isotherm determined at or near 20°C, and a repeat isotherm measured after an outgassing at 30 C. The procedure was repeated on the same sample after it had been evacuated at a... 

To see that this is true, qualitative models of the titania surface produced following each of the three pretreatments used in this study (i.e., evacuation at 600 K, evacuation at 720 K, and hydrogen reduction at 720 K) are developed below on the basis of earlier studies of Ti02 surfaces (5-6,10-22). Surface Type I Following outgassing at about 600 K the Ti02 surface should be almost entirely free of molecular water (except on the rutile fraction), but about one half of the surface should be covered... 

Figure 1. FT-IR spectra of the surface species arising from adsorption of toluene (A), o-xylene (B), m-xylene (C) and p-xylene (D) on vanadia-titania. Full lines after outgassing at 350 K.

Gas Adsorption. Gas-phase infrared spectroscopy studies (37-39) of titania surfaces have revealed that surface cation sites on titania are dehydrated on outgassing between 150 and ca. 250 °C. Surface dehydrox-... 

Figure 13. Differential energies of adsorption of nitrogen at 77 K plotted against nitrogen surface coverage. The outgassing temperature is indicated for each set of curves. Adsorbents were titania (curve A), titania with 0.6 wt %DS silica coating (curve B), and titania with 2.6 wt %DS silica coating (curve C).

FIGURE 52.14 Adsorption isotherms of water vapor (at 25°C) on titania (o) and 0.6 wt% DS-coated titania ( ). The outgassing temperature was 150°C. (Reproduced with permission from reference 42. Copyright 1986.)... 

---