Temperature-programmed oxidation technique

T Hattori, R L Burwell, Jr., Role of carbonaceous deposits in the hydrogenation of hydrocarbons on platinum catalysts. Journal ofPhysical Chemistry 83 241-249, 1979. C A. Querini, S C Fung, Temperature programmed oxidation technique kinetics of coke-02 reaction on supported metal catalysts. Applied Catalysts A 117 53-74, 1994. 

Other temperature-programmed techniques include Temperature Programmed Oxidation and Sulfidation (TPO and TPS) for investigating oxidation and sulfidation behaviour, and Temperature Programmed Desorption (TPD) (also called Thermal Desorption Spectroscopy [TDS]), which analyses gases desorbed from the surface of a solid or a catalyst on heating. 

Coking with cyclopentane. This reaction was carried out under 0.9 bar hydrogen and 0.1 bar cyclopentane at 500°C for one hour. Coke deposition was analyzed by temperature-programmed oxidation (TPO) following flie technique described earlier [6]. 

Coke was characterized by Temperature-Programmed-Oxidation (TPO). These experiments were carried out using a modified unit. The CO2 produced during the coke burning is converted to CBU, in a methanator reactor. A H2 stream is fed to this reactor, which is loaded with a Ni catalyst, in order to quantitatively convert CO2 into CH4. This compound is then continously monitored by a flame ionization detector (FID). With this configuration the sensitivity and resolution of the classical TPO technique is greatly improved. Typically, 10 mg... 

The dehydrogenation reaction produces acetone and hydrogen, and is dominant over basic oxides ( ) The dehydration reaction produces propene and water, and is dominant over acidic oxides. It would be interesting to see if the competition between these two pathways depend on the exposed crystal planes of ZnO. We report here the results of such an investigation. 2-Propanol was decomposed on ZnO single crystal surfaces by the temperature programmed decomposition technique. To assist the interpretation of data, the temperature programmed desorption of propene and acetone were also studied. 

In the last decade, there has been an increase in the research effort in this field. Coke characterization has been included in many papers where deactivation is a major issue. Several characterization techniques have been used to study coke deposits and to obtain information regarding reaction mechanism, deactivation mechanism, and regeneration conditions. One of the most widely used techniques is temperature-programmed oxidation. Because of its simplicity and utility, this technique has been widely accepted and used in the characterization of coke in a large variety of catalytic systems. 

They investigated both the fresh and spent catalysts by using temperature programmed reduction technique. The bimetallic catalysts exhibit much lower Au reduction temperature compared to Au/Fc203. The X-ray diffraction measurements show that there is no evidence for mixed metal species (Au-Ru) either in fresh or spent catalysts. TPR analysis of the spent Au-Ru/iron oxide catalyst revealed the presence of the reduction signal due to AU Oy species at a Tmax of 155 °C, which suggests the lowering in the reduction temperature which is found at 161 °C in the Au-Ru/iron oxide fresh catalyst. 

Copper-based catalysts are of considerable importance for industrial reactions, e. g. partial oxidation reactions. This contribution reports on a broad study of the catalytic activity of copper in model redox reactions, e. g. methanol oxidation and oxidative coupling of methane. In addition the interaction of Cu with these reactive gases was investigated by thermoanalytic techniques (TG/DTA, DSC), temperature programmed oxidation and reduction (TPO/tpR) and thermal desorption spectroscopy (TDS). Scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD) was additionally used to characterise the copper catalyst before and after catalytic action. 

Temperature-programmed oxidation (TPO) is an equally valuable technique for investigating the oxidation kinetics and mechanisms of reduced materials. The cyclic application of TPR and TPO provides information on the redox behavior of catalytic materials, for example, of catalysts for selective catalytic oxidations. 

Coke Characterization. Temperature-programmed-oxidation (TPO) is the most widely used technique to characterize coke. In this technique, an inert gas containing low concentration of O2 is passed through a cell with the coked catalyst sample, while linearly increasing the temperature. The amount of CO2 is monitored either by a GC-TCD, mass spectrometer, or by methanation-FID (100). 

Itkis and his coworkers have recently compared different characterization methods, i.e., scanning electron microscopy [SEM], TEM, thermogravimetry (TGA], Raman, and near infrared [NIR] spectroscopy, in order to determine the optimum combination of these techniques to get reliable and accurate information about the purity of the CNT studied. They conclude that the combination of TGA and Raman spectroscopy is quite satisfying. In the same field, Herrera et al. reported a successful use of in situ temperature programmed oxidation [TPO] and Raman spectroscopy to reach the same goal. 

When coupled to MS, the thermogravimetric equipment can be used as a Temperature Programmed Oxidation (TPO) or/and a Temperature Programmed Desorption (TPD) technique to follow catalytic oxidation processes [62]. 

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