Thermodesorption spectra

The lattice gas model is used to elucidate the "diffusion order-disorder transition on catalyst surfaces [92-102]. Finally, as has been mentioned already, this model is important in decoding thermodesorption spectra. 

Let us emphasize the following as a rule, the literature lacks a strict discrimination between the structures that are formed at the microscopic and macroscopic levels. It is important to understand whether the terms "structure , "ordering and "islands refer to microstructures or macrostructures. Thus, the lattice gas model is aimed at accounting for the formation of microstructures, peculiarities in thermodesorption spectra, etc. 

It is shows the thermodesorption spectra of water, atomic and molecular oxygen mono-two-oxide from the surface of initial diamonds taken in 20-600°. Figure 7 shows the thermodesorption spectra of water from the.surface the initial diamond (1) and diamond after palladium precipication (2). It is seen from the figures that there is a great difference in quantity of water on the initial and modified surfaces of diamonds. The water quantity, which desorbed with precipication palladium diamond increased in 5. 

Figure 7. Thermodesorption spectra of water from the surface the initial nanodispersed diamond (1), the diamond after promouted palladium(2).

Figure 8 shows the thermodesorption spectra of atomic oxygen from the surface the initial diamond (1) and promoted palladium diamond (2). 

Figure 8 shows the thermodesorption spectra of atomic oxygen from the... 

The various TPR peaks may correspond to different active sites. One hypothesis assumed cyclization over metallic and complex (Section II,B,4) platinum sites (62e) the participation of various crystallographic sites (Section V,A) cannot be excluded either. Alternatively, the peaks may represent three different rate determining steps of stepwise aromatization such as cyclization, dehydrogenation, and trans-cis isomerization. If the corresponding peak also appears in the thermodesorption spectrum of benzene, it may be assumed that the slow step is the addition of hydrogen to one or more type of deeply dissociated surface species which may equally be formed from adsorbed benzene itself (62f) or during aromatization of various -Cg hydrocarbons. Figure 11 in Section V,A shows the character of such a species of hydrocarbon. 

Figure 6.19. Thermodesorption spectrum of the hydroxyl groups (m/e = 18) and oxygen (m/e = 32) bound to tin dioxide prior to treatment...

Figure 6.21. Thermodesorption spectrum of nickel oxide sinters exposed to air...

Figure 6.22. Oxygen thermodesorption spectrum as a function of adsorption temperature Ta...

Figure 6.28 gives the thermodesorption spectrum of four samples that were degassed at 250, 400, 500 and 600°C. These samples had initially been exposed to oxygen at 600°C. 

Figure 6.28. Thermodesorption spectrum of oxygen obtained with nickel oxide at 600°C and degassing at different temperatures Tp...

Figure 6.29. Thermodesorption spectrum obtained with nickel oxide after sulfur dioxide adsorption at 250°C samples 2 to 5...

Figure 7. The thermodesorption of hydrogen Figure 8. The thermal desorption spectrum...

Figure 12.21 Typical adsorption spectrum for pyridine on an alumina. Adsorption at 25 C and thermodesorption by steps up to 350°C.

Cryogenic trapping, an unselective enrichment technique, has been used in cryogenic traps and the heads of analytical columns for the purpose of focusing. By contrast, trapping by adsorption on solids can be very selective. A broad choice of sorbents with different enrichment behavior for organic compounds is commercially available. Selectivity is not limited to concentrated analytes, undesirable matrix compounds can also be removed as described in some exercises in the cleanup section. Alternatively, some mixtures of sorbents are available to cover substances with a broad substance spectrum. Sorbed substances can be mobilized by thermodesorption and elution. 

The Q-TG mass loss and the Q-DTG differential mass loss curves of liquids as a fiinction of temperature from the N-1, N-2 and N-3 carbon nanotube surfaces are presented in Figure 11. The characteristic inflections in the Q-DTG curves correspond to the individual stages of thermodesorption of the selected liquids from nanotube surfaces. The Q-DTG curve is a type of spectrum of thermodesorption process, describing the energetic states of polar and nonpolar molecules on the surface. The spectrum indicates long wide peaks with the minima near 70 (N-l/benzene), 115 (N-2/n-octane) and 120 C (N-3/n-butanol) and a few other small peaks. The data presented in Table 2 show that the samples are highly sensitive to water vapour because the mechanism of molecular adsorption depends largely on the activated surface centres. 

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