Temperature-programmed reduction characterization

Temperature-Programmed Reduction for Solid Materials Characterization, Alan Jones and Brian McNichol... 

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. 

A. Jones and B.D. McNicol (eds.), Temperature Programmed Reduction for Solid Materials and Characterization, New York M. Dekker, 1986... 

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). 

T. H. Tsai, J. W. Lane, and C. S. Lin Temperature-Programmed Reduction for Solid Materials Characterization, Alan Jones and Brian McNichol Catalytic Cracking Catalysts, Chemistry, and Kinetics,... 

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. 

The catalysts were characterized by inductively coupled plasma emission spectroscopy (ICP-ES Perkin Elmer Optima 3300RL) to determine cobalt content, x-ray diffraction (XRD Bruker A-500) with crystallite size determination using the Rietveld method, and temperature-programmed reduction (Zeton Altamira AMI-200) using 30 ml/min 10% H2/Ar and a ramp rate of 10°C/min. Surface area... 

Temperature-programmed reduction combined with x-ray absorption fine-structure (XAFS) spectroscopy provided clear evidence that the doping of Fischer-Tropsch synthesis catalysts with Cu and alkali (e.g., K) promotes the carburization rate relative to the undoped catalyst. Since XAFS provides information about the local atomic environment, it can be a powerful tool to aid in catalyst characterization. While XAFS should probably not be used exclusively to characterize the types of iron carbide present in catalysts, it may be, as this example shows, a useful complement to verify results from Mossbauer spectroscopy and other temperature-programmed methods. The EXAFS results suggest that either the Hagg or s-carbides were formed during the reduction process over the cementite form. There appears to be a correlation between the a-value of the product distribution and the carburization rate. 

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). 

The results from this "temperature programmed reduction" indicate that there are two regimes as indicated in Figure 16. In Regime 1, at temperatures above 1050°F there is virtually complete removal of SO2 under the conditions of our test. In Regime 2, characterized by the step jump downward at 1050°F in the amount of SO2 adsorbed in successive cycles, there is only partial removal of SO2. This observation suggests two kinds of surface sulfate species present on this material, one easily and another more difficultly removed as indicated by Andersson (47). 

Mg pyrovanadate (Mg2V207) was also found to be a selective catalyst for this reaction (30). A later study further showed that the catalytic performance of Mg2V207 was insensitive to the method of preparation, such that there were only minor differences whether or not the oxide contained small amounts of potassium (25). In contrast, the presence of K in Mg orthovanadate degraded its selectivity noticeably. Temperature-programmed reduction with H2 and electrical conductivity characterization in the presence of propane showed that Mg pyrovanadate could be reduced by both H2 and propane faster than Mg orthovanadate containing K (31). 

Temperature Programmed Reduction. Temperature-programmed reduction (TPR), one of the indirect analysis methods, yielded data that suggested that Sn was not reduced to zero-valent state (10,16). Burch (15) has reviewed early work on the characterization of this type of catalyst. Lieske and Volter (21) reported, based on the results obtained from TPR studies, that a minor part of the tin is reduced to the metal, and this Sn(O) combined with Pt to form "alloy clusters" but the major portion of the tin is reduced to only the... 

Temperature-programmed reduction (TPR) is normally used in the characterization of catalysts [18,91-93], In general, to carry out a TPR experiment, a reducing gas mixture, typically 5% hydrogen in nitrogen, flows continuously over the sample [92], The gas flow rate can be varied precisely using either built-in controls or an optional mass flow controller accessory. 

Kinetic studies focus on the selection of an adequate rate expression and determination of the unknown rate parameters it contains (eq 1). Generally, the rate is not measured directly but is derived from a measured quantity, conversion or concentration, at given operating conditions such as catalyst amount and feed rate. Apart from kinetic studies to determine the rate equation, other purposes of measuring rates are comparison of various catalyst formulations in screening of new catalysts, the time-dependent behavior of the catalyst actvity to predict its long term performance and to characterize catalysts such as in temperature programmed reduction (TPR) or sulphidation (TPS) studies. 

It was appreciated at the outset that the characterization of these materials would be an altogether more difficult problem than that of EUROPT-1, by reason of the lower metal content, and the bimetallic nature of EUROPT-4. It was hoped that study of the latter would help resolve some of the questions concerning the intimacy of mixing of the two metals in the functioning catalyst, but these queries have been only partially answered. Temperature programmed reduction (TPR) studies have confirmed the sensitivity of the reduction profile to experimental conditions and sample pretreatment but, notwithstanding reports in the liter-... 

Details of characterization by x-ray and electron diffraction, transmission electron microscopy and XPS are given elsewhere ( ). Temperature programmed reduction (TPR) studies using a 3%H2/N2 gas mixture, were performed on 40 mg catalyst samples in a tubular furnace (heating rate 10 C/min), using TCD and FID detection. Prior to TPR, the sample was heated in air at a specified temperature for 3h. 

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