Temperature-programmed oxidation analysis

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 1.13 shows a diagram of a xsorb automated system used to conduct chemisorption measurements, volumetric analysis, temperature programmed reduction, temperature programmed oxidation, etc. 

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). 

This work presents a detailed study of coke deposition on Pt/Nb20s catalysts which were deactivated with n-heptane dehydrogenation. Temperature programmed Oxidation (TPO) allowed to the identification of different coke oxidation zones which are related to the distribution of carbonaceous species on the support and on the metallic sites. Chemical analysis of soluble coke was performed allowing to a better understanding of the deactivation processes on niobia supported catalysts. 

The spent catalysts were characterized by chemical analysis (carbon content), temperature programmed oxidation coupled to a mass spectrometer (TPO/MS) and thermal analysis (DTA and TG). The samples were also submitted to extraction of soluble coke in a soxhiet apparatus with n-hexane and dichloromethane for 24h, after being treated with fluoridric acid (40%) at room temperature (2h), followed by reflux with hydrocloric acid (36%) for 2h. The extracts were analyzed by gas-chromatography-mass spectrometry (GC/MS), Fourier transformer infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV) and X ray diffraction. The insoluble fraction was analyzed by X ray diffraction and FTIR. 

Temperature-programmed oxidation (TPO) measurements were performed in a CRY-1 DTA equipment connected with a gas chromatograph (GC) for effluent gas analysis. The amount of CO2 produced was measured at a temperature programmed rate of 20 °C/min. A 10 vol. % oxygen in N2 was introduced at a flow rate of 15ml/min. 

Temperature programmed oxidation (TPO) tests were also performed for the two series of catalysts and their respective supports by registering the sample weight during the thermal process. The analysis of those curves not only allowed accurate determination of the metal loading in the samples (Table 12.1), but also provided some structural information related to the ability of the Pt surface to catalyze the oxidation of the carbon at its periphery. The differential thermogravimetric (DTG) profiles obtained (Figure 12.18) show how the presence... 

FIGURE 12.18 Differential thermogravimetric analysis curves during the temperature programmed oxidation (DTG-TPO) of the Pt/CB catalysts (a) and their supports (b). Heating rate 25Kmin . ... 

The kinetic model is also valid for other systems with temperature programming, such as temperature programmed oxidation (TPO), differential scanning calorimetry (DSQ, and thermogravimetric or differential analysis (ATG, ATD), as we shall see. 

Starting from iron acetate or iron nitrate salts and following the neutral and oxidative pathways, a separated analysis of iron (2+, 2.5+, 3+)-calcium oxide and iron (2+, 2.5+, 3+)-magnesium oxide will be useful also to clarify the nature of the iron-dolomite interaction. The Fe/substrate catalysts have been characterized by X-Ray diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Oxidation (TTO), and Mdssbauer analysis. XRD and TPR experimental conditions, as well as the microreator used in catalytic tests, have been described previously [Di Felice et al., 2009], whereas Mossbauer spectroscopy and TPO are briefly illustrate here. 

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