Temperature programmed oxidation TPO

The activity of catalyst will gradually decline during application, and one of the reasons is the aggradation of carbon on catalyst surface. TPO technology is an effective way to study the formation mechanism of carbon deposition. For example, TPO is used to study Pt/Al203 catalyst for the mechanism of carbon deposition. TPO shows two peaks after the carbon deposition on surface of Pt/A Os, that is, Toi 440°C, To2 530°C. After the catalyst was deposited with carbon, it was partially oxidized (that is, the oxidation of deposition carbon of the first peak at 440°C), where the adsorption amount of H2 almost equals the fresh catalyst, and the activity of the catalyst is almost recovered. This proves that the carbon deposition takes place on surface of Pt metal, from which it can be inferred that the oxidation peak at high temperatures corresponds to the oxidation of carbon deposited on support. 

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TEM observation and elemental analysis of the catalysts were performed by means of a transmission electron microscope (JEOL, JEM-201 OF) with energy dispersion spectrometer (EDS). The surface property of catalysts was analyzed by an X-ray photoelectron spectrometer (JEOL, JPS-90SX) using an A1 Ka radiation (1486.6 eV, 120 W). Carbon Is peak at binding energy of 284.6 eV due to adventitious carbon was used as an internal reference. Temperature programmed oxidation (TPO) with 5 vol.% 02/He was also performed on the catalyst after reaction, and the consumption of O2 was detected by thermal conductivity detector. The temperature was ramped at 10 K min to 1273 K. 

Figure 9. Temperature programmed oxidation (TPO) data showing CO2 evolution m/e = 44) of thermally deposited carbon from a Cu-Ce02-YSZ SOFC anode material after exposure to n-butane for 30 min (solid line) and a graphite powder sample (dashed line). (Reprinted with permission from ref 172. Copyright 2003 The Electrochemical Society, Inc.)...

The catalytic coke produced by the activity of the catalyst and simultaneous reactions of cracking, isomerization, hydrogen transfer, polymerization, and condensation of complex aromatic structures of high molecular weight. This type of coke is more abundant and constitutes around 35-65% of the total deposited coke on the catalyst surface. This coke determines the shape of temperature programmed oxidation (TPO) spectra. The higher the catalyst activity the higher will be the production of such coke [1],... 

Swann et al. [9] used isotopic labeling and temperature-programmed oxidation (TPO) (ex situ) approaches to show that the carbon which had formed during the C02 reforming of methane may have derived from both CH4 and C02. 

The H/C ratio of the coke deposits was quantified by temperature programmed oxidation (TPO) in a 1 % oxygen helium mixture. Temperature was raised to 850° C at a heating rate of 10° min 1. The calculations of the H/C ratio involved the results from the measurements of carbon dioxide production and oxygen uptake (according to Ref. [8]). Coke deposits were also characterized by thermogravimetry and transmission electron microscopy. 

When the system is used in pulse mode, it allows the measurement of heats of adsorption of a gaseous reactant on a solid or interaction heats between a gaseous reactant and pre-adsorbed species. When used as a flow reactor, it allows the kinetic study of catalytic reactions as well as the study of the activation or the aging of the catalyst. This is also a suitable system to perform calorimetric temperature programmed reduction (TPR), temperature programmed oxidation (TPO) or temperature programmed desorption (TPD) experiments. In addition to calorimetry, temperature programmed desorption (TPD) of adsorbed probe molecules can in principle also be used to estimate heats of adsorption [19]. 

Temperature Programmed Oxidation (TPO) is useful for characterising the nature of deposits containing carbon (coke) in the case of a deactivated catalyst... 

I. Temperature-programmed oxidation TPO- and coke distribution on catalyst functions... 

Fig. 3. Temperature-programmed oxidation (TPO) data for used catalysts with different Pt loadings. The first peak is for coke deposited on the metal function and the second for coke on acid function.

The deactivation of a Pt-Re/AI203-d reforming catalyst was studied at moderate pressure using n-heptane as feed. A reactor which allows the analysis of the reaction products along the catalyst bed and the discharge of deactivated catalyst in discrete sections was used in this study. The coke was characterized by temperature-programmed oxidation (TPO). 

Carbon deposits corresponding to the first peak can be removed by temperature programmed oxidation (TPO). After this simple treatment, the activity and selectivity arc... 

The nature of the coke produced with Che three catalysts after the sarne run length la seen in the temperature programmed oxidation (TPO) profiles shown in Figure 4. The first peak at around 450 has been ascribed to coke associated with Pt sites and is linked to deactivation. The second peak at about 580 C is associated with coke on the alumina support (ref. 1,4,5). Clearly the "PC" peak is larger for the Pt alone catalyst despite that the total coke level Is lower than for Pt-Re it Is also larger than Pt-Sn, but here the total coke level is smaller. The size of the Pt peaks compares well with the nown deactivation characteristics of the three different catalysts. 

Temperature programmed oxidation (TPO) was performed by burning the obtained coked catalyst in 1%02 in an He atmosphere. The heating rate was 10°C/min. CO2 produced was measured using a gas chromatograph equipped with a TCD and an on-line gas sampling valve. 

Temperature-programmed reduction (TPR) experiments were carried out in a conventional TCD system using 10 ml min of an H2 (5 wt%)-N2 gaseous mixture at a constant heating rate of 6 K min from room temperature up to 1073 K. Temperature-programmed oxidation (TPO) profiles were obtained using a mixture of O2 (6 %v/v)-N2 and... 

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