TPD Profile

Fig. 2. Deconvolution of TPD profile from 17%Ga203/Ga-M0R-115 (a) by using a profile from Ga203/Si02 (c) and two Gaussian functions (d and e). Profile b is the sum of c, dande.

Figures 3 and 5 give examples of hydrogen TPD profiles observed on both catalysts reduced at 473K. The more intense patterns concern the desorption of the hydrogen fixed on the solids during the reduction step (curve a) while the weaker peaks (curve b) are related to the hydrogen retained after readsorption at room temperature. Hydrogen adsorption is thus an activated process.

Figure 1 Mass spectrometer (MS) intensities versus surface temp ature in a rqnesentadve temperature programmed desorpticm (TPD) profile of methyl on a clean Ni(lOO) surface. Total exposure was 1 L. Adsorption temperature was 105 K and heating rate was 3 K/s. Methane is produced near 225 K.

Figure 3. Oxygen TPD profiles from the indicated preoxidised materials.

Figure 2 TPD profiles for the two commercial, 5 wt% Rh supported on y-A1203 catalysts.

Figure 28. O2-TPD profile of ZnGa204 and LaGaOs mixed oxides [108],...

Figure 3. NF13-TPD profiles of (a) W03/Ti02, (b) W03/Sn02, (c) W03/Fe203, (d) Ti02, (e) Sn02, (f) Fe203, and (g) WO3 used for Freon decomposition [55], Catalyst load 0.2 g. [Reproduced by permission of Elsevier fromMa, Z. Flua, W. M. Tang, Y. Gao, Z. J. Mol. Catal. A 2000,159, 335-345.].

The solid acidity of these atom-planted silicalites was examined by ammonia TPD measurement. The ammonia TPD profiles of all these metallosilicates showed one peak at a higher temperature than 453 K. Figure 4 shows the relationship between peak temperatures of ammonia TPD and wavenumber of IR absorption bands due to the acidic SiOH groups of atom-planted silicalites. A straight line was obtained. From these results, the order of strength of acid sites would be as follows ... 

Fig. 4. Relationship between peak temperature of ammonia TPD profiles and wave-number of IR adsorption band in OH stretching region for atom-planted zeolites.

The TPD profiles of Fig. 14 show that there are two types of adsorbed C2H4 on Pt(lll). These can be referred to as reversibly and irreversibly adsorbed. The reversibly adsorbed C2H4 is inferred to be coverage-depen-... 

Figure 2. NH3-TPD profiles of mesoporous materials, (a) NaAlMCM-41, (b) HA1MCM-41 and (c) PgM41...

The TPD profile for the 97.1% Mo03/A1203 sample nitrided at 973 K shows two N2 desorption peaks at 819 and 1001 K (Figure 17.1). The N2 desorption at low temperature was accompanied by H2 desorption. During... 

Fig. 16. TPD profiles of NH3 from various solid acids (a) CS2.5H0.5PW12O40, (b) H3PW12O40, (c) SO4 /Zr02, (d) SiOj-AljOj, (e) H-ZSM-5. Solid line NH3 (mle = 17) dotted line N2 (mle = 28). (From Ref. 127.)...

Figure 4.39 [95] shows the NH3-TPD thermograms corresponding to H-MOR, H-HEU, H-LTL, H-FAU, H-MFI, and CoAPO-5 (calcined). The TPD profiles of the samples show two different regions that can be assigned to weak and strong acid sites. 

For the generation of the FTIR-TPD profiles (A vs. T), the decrease in the intensity (absorbance) of one of the selected bands was monitored, during heating at a constant rate [97]... 

The FTIR-TPD profiles (A vs. T) for the desorption of benzene, toluene, and ethylbenzene from high-silica H-ZSM-5 is reported in Figure 4.40 [97], These results were fitted with the complementary error function, that is,... 

Figure 1. TPD profiles after reduction (792 K.) and subsequent cooling in H2.

In conclusion, the TPD spectra can be characterized by two broad peaks, one at 100° and the other at 450°. However, these could be made up of a combination of several different peaks. Assignments of these individual peaks to specific Pt states are hardly possible, but the broad TPD profile arises out of two possible causes either to structural changes in the Pt crystallite forms or to variation of Pt-alumina interactions due to the heterogeneity of the alumina surface. 

Figu re 17.2 Ar-TPD profiles of solid acids temperature programmed rate 2Kmin... 

---