Temperature programmed reduction TPR

TPR technique is the reduction process under the conditions of a constant temperature rising rate. If the sample is reduced with the increasing of temperature, the concentration of hydrogen in the gas changes with temperature. The change of the concentration of hydrogen with temperature is recorded, and the curve of TPR is obtained. 

A pure metal oxide has a specific reduction temperature which can be used to express as a qualitative indicator of the oxide. When two kinds of oxides are mixed, then they cannot produce chemical reactions with each other. Each metal oxide keeps its specific reduction temperature which can be expressed by. On the other hand, if the two oxides create a solid-state chemical reaction before reduction, the characteristic reduction temperature of each oxide will be changed. 

A variety of metal catalysts are commonly used with their oxides as precursors. The oxide may undergo chemical reaction with support, and reactions may take place between the components in multi-component metal catalysts during preparation process. Thus, TPR peaks of each oxide will be different from its pure oxides. In other words, the interaction between metal components and support or between metal components can be studied by TPR method for metal catalysts. The sensitivity is so high that it can detect the reduction reaction with consumption of only 10- mol H2. 

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Catalysts were characterized using SEM (Hitachi S-4800, operated at 15 keV for secondary electron imaging and energy dispersive spectroscopy (EDS)), XRD (Bruker D4 Endeavor with Cu K radiation operated at 40 kV and 40 mA), TEM (Tecnai S-20, operated at 200 keV) and temperature-programmed reduction (TPR). Table 1 lists BET surface area for the selected catalysts. 

Temperature-programmed reduction TPR was used to determine the reduction behaviors of the catalyst samples. It was carried out using 50 mg of a sample and a temperature ramp from 35 to 800°C at 5°C/min. The carrier gas was 5% H2 in Ar. A cold trap was placed before the detector to remove water produced during the reaction. 

In this work, the catalytic reforming of CH4 by CO2 over Ni based catalysts was investigated to develop a high performance anode catalyst for application in an internal reforming SOFC system. The prepared catalysts were characterized by N2 physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). 

Physical properties of the prepared catalysts were measured by an adsorption analyzer [Quantachrome Co., Autosorb-lC]. The structure of prepared catalysts were investigated by XRD [Simmazdu Co., XRD-6000] with a Cu-Ka radiation source (X = 1.54056 A), voltage of 40.0 kV, ciurent of 30.0 mA and scan speed of 5.0 deg/min. Also, temperature-programmed reduction (TPR) profiles of the samples were investigated by a sorption analyzer [Micromeritics Co., Autochem II] and obtained by heating the samples from room temperature to 1100°C at a rate of lOTl/min in a 5 % H2/Ar gas flow (50 ml/min). 

Surface areas were determined from the adsorption isotherms of nitrogen at 77 K, using a Micromeritics ASAP 200 instrument. Powder X-ray diffraction patterns were obtained with a CGR theta 60 instrument using CuKa monochromated radiation. Reducibility and the amount of Cu species were determined by temperature programmed reduction (TPR) with H2 (H2/Ar 3/97, vol/vol). The experimental set up has been described previously [6]. 

In this study butyl acetate (AcOBu) was hydrogenolysed to butanol over alumina supported Pt, Re, RePt and Re modified SnPt naphtha reforming catalysts both in a conventional autoclave and a high throughput (HT) slurry phase reactor system (AMTEC SPR 16). The oxide precursors of catalysts were characterized by Temperature-Programmed Reduction (TPR). The aim of this work was to study the role and efficiency of Sn and Re in the activation of the carbonyl group of esters. 

Temperature programmed reduction (TPR) experiments. TPRs were performed for each material using a quartz reactor tube (4 mm i d ), in which a 100 mg sample was mounted on loosely packed quartz wool. Samples were predried overnight at 120 °C. The sample was heated at 5 °C /min up to 700 °C under 20 mL/min flow of a 2 1 mixture of H2 Ar. 

One way in which cobalt dispersion can be increased is the addition of an organic compound to the cobalt nitrate prior to calcination. Previous work in this area is summarized in Table 1.1. The data are complex, but there are a number of factors that affect the nature of the catalyst prepared. One of these is the cobalt loading. Preparation of catalysts containing low levels of cobalt tends to lead to high concentrations of cobalt-support compounds. For example, Mochizuki et al. [37] used x-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) to identify cobalt silicate-like species in their 5% Co/Si02 catalysts modified with nitrilotriacetic acid (NTA). The nature of the support also has... 

Van t Blik H.F.J. and Prins R. 1986. Characterisation of supported cobalt and cobalt-rhodium catalysts. 1. Temperature-programmed reduction (TPR) and oxidation (TPO) of Co-Rh/Al203. J. Catal. 97 188-99. 

Temperature-programmed reduction (TPR) gives information on the reduction behavior of the Co catalysts. The spectra were recorded by the instrument ChemBET 3000 (Quantachrome Instruments) equipped with a thermal conductivity detector. Before analysis the samples were dried overnight (at least 12 h) at 373 K. The reduction was carried out in a hydrogen mixture of 10% H2 in Ar with a heating rate of 10 K/min. 

The aim of this work was to apply combined temperature-programmed reduction (TPR)/x-ray absorption fine-structure (XAFS) spectroscopy to provide clear evidence regarding the manner in which common promoters (e.g., Cu and alkali, like K) operate during the activation of iron-based Fischer-Tropsch synthesis catalysts. In addition, it was of interest to compare results obtained by EXAFS with earlier ones obtained by Mossbauer spectroscopy to shed light on the possible types of iron carbides formed. To that end, model spectra were generated based on the existing crystallography literature for four carbide compounds of... 

Temperature-programmed reduction (TPR) profiles of fresh catalyst samples were obtained using a Zeton Altamira AMI-200 unit. Calcined fresh samples were first heated and purged in flowing argon to remove traces of water. TPR was performed using 30 cc/min 10% H2/Ar mixture referenced to argon. The ramp was 5°C/min from 50 to 1,100°C, and the sample was held at 1,100°C for 30 min. 

Structural characterization of the prepared Co/alumina catalysts was studied by using the following techniques Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR), H2 chemisorption by temperature-programmed desorption (TPD) with 02 pulse reoxidation, and powder x-ray diffraction (XRD). 

Catalysts used in the temperature programmed reduction (TPR) study were granular and are described in Table II. These catalysts were made by... 

Temperature Programmed Reduction (TPR) Studies. In the TPR studies, a gas mixture of 2% H2 in Ar is passed over powdered samples of the calcined catalysts. The catalysts are held in the middle of a 5-mm diameter, 0.4-m long quartz reactor with... 

Temperature-Programmed Reduction Studies. The temperature programmed reduction (TPR) system, built in-house, is shown schematically in Figure 2. The same system was also used for temperature programmed desorption studies. The TPR profiles were determined by heating samples (50 mg) at a rate of 5 °C per minute from 50 °C to 950 °C. The temperature was then held at 950 °C until the reduction was completed. The reducing gas was 6 % H2 in N2, and the... 

Fischer-Tropsch (FT) process is used for the production of hydrocarbon fuels. The process uses synthesis gases CO and H2O. It is shown that cobalt/alumina-based catalysts are highly active for the synthesis. The process is also used to convert coal to substitute or synthetic natural gas (SNG). The use of Fe-based catalysts is also believed to be attractive due to their high FT activity. HRTEM has played a major role in the study of phase transformations in Fe Fischer-Tropsch during temperature programmed reduction (TPR) using both CO and H2 (Jin et al 2000, Shroff et al 1995). TiClj/MgC -based (Ziegler-Natta) catalysts are used for polymerization of alkenes (Kim et al 2000) and EM is used to study the polymerization (Oleshko et al 2002). 

These structural changes are accompanied by significant reactivity modifications of the surface vanadia species. The addition of the surface potassium oxide species decreases the reducibility of the surface vanadia species in temperature programmed reduction (TPR) studies and the TOF for methanol oxidation.23,50 The most likely reason for this behavior is that the surface potassium oxide species is intimately coordinated to the bridging V-O-Support bond and retards its participation in these redox processes. Thus, all oxidation reactions, involving one surface vanadia site as well as dual surface vanadia-acidic sites, will be retarded by the surface potassium oxide additive. The basic properties of the surface potassium oxide additive may also affect the product selectivity by... 

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