Temperature-programmed desorption curves

Fig. 7. Typical temperature-programmed desorption curve for HD from an olivine surface as a function of surface temperature. Curves are for exposure times to the H and D beams of (bottom to top) 0.07, 0.1, 0.25, and 0.55min (Pirronello et al., 1997a).

L. Liu, L. Zhao, H. Sun, Simulation of NH3 temperature-programmed desorption curves using an ah initio force field,). Phys. Chem. C 113 (2009) 16051-16057. 

Figure 10. Temperature programmed desorption curve of water on hematite (012) from Henderson et al. (1998) at various coverages. Peak at 158 K is from ice formed at coverages in excess of 1 monolayer. Note first-order coverage-independent behavior of desorption peak at 353 K.

Figure 5. Ammonia temperature-programmed desorption curves of various titanium oxide samples.

Accessibility to Cu sites was determined by temperature programmed desorption of NO (NO TPD), using an experimental setup similar to that used for TPR, except the detector was a quadrupole mass spectrometer (Balzers QMS421) calibrated on standard mixtures. The samples were first activated in air at 673 K, cooled to room temperature in air, and saturated with NO (NO/He 1/99, vol/vol). They were then flushed with He until no NO could be detected in the effluent, and TPD was started up to 873 K at a heating rate of 10 K/min with an helium flow of 50 cm min. The amount of NO held on the surface was determined from the peak area of the TPD curves. 

Fig. 11. The temperature programmed desorption spectra for CO from Fe(lOO) following adsorption at 180 K. Curves (a)-(e) are arranged in order of increasing initial coverage by CO 45).

Fig. 4 (a) Stepwise dehydrocyclization of -hexane (21, 62). (b) Temperature programmed desorption of benzene originating from various adsorbates over Pt-AljOs. Temperature of adsorption 25°C. Rate of heating 23°C per minute. Detector monopolar mass spectrometer, the ordinate corresponds to the I intensity of mass number 78, in arbitrary units. For clarity, the thermodesorption curves for other compounds (starting hydrocarbon) hexene from hexa-dienes and hydrogen have not been shown (62c). 

Figure 13 Experimental (left) and simulated (right) temperature-programmed desorption spectra for COjRh( 100). The values on the right of each set of curves indicate initial coverages. The thin curves on the right are simulated spectra with the lateral interactions switched off. The heating rate is 5 Kjs ...

Figure 16 Simulated and experimental temperature-programmed desorption spectra for OlPt(lll). The solid lines are experimental spectra. The crosses indicate simulated spectra for a model of the lateral interactions with nearest and next-nearest pair interactions, and also a linear 3-particle interaction. The O2 is formed from two atoms at next-nearest-neighbor positions. The kinetic parameters are — 206.4 kj/mol, v = 2.5 x 10 s a = 0.773, cpxN — 19.9 kjjmol, tp NN = 5.5 kjjmol, and (punear = 6.1 kJImol. In each plot the curves from top to bottom are for initial oxygen coverage of 0.194, 0.164, 0.093, and 0.073 ML, respectively. The heating rate is 8 Kjs ...

The temperature programmed desorption profile for the adsorption of butadiene in place of cis-2-butene is shown in Fig. 1, curve c. Two sets of products are observed. The product below 210°C is unreacted butadiene, and the products above 210°C are carbon dioxide and water. The similarity in the evolution of the combustion products of butene and butadiene is an indication that their combustion proceeds via similar reaction mechanisms. The similarity in the desorption of butadiene suggests that in butene adsorption, butadiene desorption is desorption limited. Indeed, that both butene and butadiene adsorb on the same type of sites has been confirmed by sequential adsorption experiments. The results are shown in Table III. It was found that if the C4 hydrocarbons are adsorbed sequentially without thermal desorption between adsorptions, the amounts of the final desorption products are the same as those in experiments where only the first hydrocarbon... 

Fig. 2.9 Examples of temperature-programmed desorption following zeroth-, first- and second-order kinetics. Each curve corresponds to a different initial coverage of the adsorbate. Ag/Ru(001) Silver forms islands on the ruthenium substrate. Desorption of Ag from the edges of these islands gives rise to zeroth-order kinetics note the exponential increase of the low-temperature sides of the peak, as expected from Eq. (2-15). Desorption from the second layer of silver occurs at lower temperatures, indicating that Ag-Ag bonds are weaker than Ag-Ru bonds [20]. CO/Rh(111) At coverages...

FIGURE 20 Amount of NH3 adsorbed on acid sites measured by temperature-programmed desorption. The three curves show different acid site distributions for the same catalyst composition prepared by different methods. 

Fig. 2.12 Temperature programmed desorption (TPD) curves for the desorption of hydrogen from platinum catalysts. I) Full TPD curve II) curve after partial desorption, cooling and then reheating. (Drawn using data from Ref. 44).

The sample pre-treatment as well as adsorption and desorption experiments were performed with a flow rate of 100 cm rnin-i that was passed through a quartz reactor (U-type) containing 1 g of bentonite meshes. The sample was first pre-treated under N2 flow at 473 K for 30 minutes than adsorption was carried out using the model mixture flow until saturation was reached in order to obtain breakthrough curves. The gas mixture was switched again to pure N2 flow, to proceed with isothermal desorption xmtil o-xylene concentration at the reactor outlet reached zero. This step was followed by a subsequent linear heating in order to perform Temperature Programmed Desorption (TPD) experiment. 

Ammonia temperature programmed desorption (NH3-TPD) curves were recorded by placing 1.5 g of zeolite particles (60x140 mesh) into a tube furnace and heated to 125°C. Aimnonia was supplied to the zeolite in dry air at a concentration of 1,000 mg/m (1,450 ppm) and a flow rate of 2 L/min. The aimnonia flow was terminated once the effluent concentration equaled the feed concentration, and clean air was subsequently purged through the zeohte imtil ammonia was no longer detected in the effluent. The temperature was then... 

One of the alternative methods for assessment of the porosity of solids within the mesopore range was proposed at the beginning of 90s (see reference [449] and references therein). The method consists of the measurements of temperature programmed desorption of liquids wetting the porous solid perfectly. Experimentally obtained desorption curves representing the weight loss of the... 

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