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Abstract  

The quantitative interpretation of X-ray fluorescence (XRF) data is often difficult because of matrix effects. The intensity of fluorescence measured for a given element is not only dependent on the element's concentration, but also on the mass absorption coefficients of the sample for the excitation and fluorescence radiation. Also, there are interelement effects in which high-energy fluorescence from heavier elements is absorbed by ligher elements, with a resulting enhancement of their fluorescence. Recent theoretical treatments of this problem have shown that X-ray fluorescence data can be corrected for these matrix effects by calculations based on first principles. Fundamental constants, available in atomic physics data tables, are the only parameters needed. It is not necessary to make empirical calibrations. In this paper we report the application of this correctional procedure to alloys and alumina-supported catalysts. We also discuss how it may be applied to other matrices. A description is given of a low-background spectrometer which uses monochromatic AgKα radiation for excitation. Matrix corrections by first principles can be easily applied to data from instruments of this type because fluorescence excitation cross-sections and mass absorption coefficients can be accurately defined for monochromatic radiation.

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to gold catalysts. The increases in the particle size observed on Nb 2 O 5 can be explained considering its lower surface area and deposition mechanism of colloids over the support. On Nb 2 O 5 supported catalysts, the addition of gold to iridium

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, Piedigrosso P, Colomer JF, Mukhopadhyay K, Doome R et al. Synthesis of single- and multi-wall carbon nanotubes over supported catalysts, Appl. Phys. A 1998; 67: 11–22. Doome R. Synthesis of

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Introduction The Fischer–Tropsch (FT) synthesis is a process of hydrocarbon production from carbon monoxide and hydrogen. Cobalt-supported catalysts are currently preferred over Fe-based systems due to their superior

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prone to recycling difficulty [ 10 ], though this type of catalyst has shown excellent catalytic performance in homogeneous reactions with a wide variety of substrates [ 11 ]. Generally, supported catalysts are simply prepared by the impregnation of

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. The interaction of Pd with Mn 2 O 3 results in good catalytic activity of the catalyst. The catalytic activity of the doped catalysts was compared with supported catalysts. Stability studies were performed and the catalytic activity was tested in the

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homogeneous catalysts and simultaneously avoiding its disadvantages like handling and reusability. These supported catalysts have often shown high catalytic activities in comparison to unsupported analogues due to the better interaction of active sites with

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Fischer–Tropsch synthesis, isomerization, esterification reactions [ 8 , 9 ], synthesis of biodiesel and catalytic purification of automobile exhaust, etc. [ 10 , 11 ]. Research indicates that the performance of zirconia supported catalysts is superior

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on continuous flow processes using scCO 2 and supported catalysts, see: (a) Stouten , S. C. ; Noël , T. ; Wang , Q. ; Hessel , V. Chem. Eng. Process. 2014 , 83 , 26 – 32 ; (b

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. Obviously, the metal loading was controlled at 3.0 wt%. After loading, compared with activated carbon, the BET surface area of supported catalysts decreased slightly, since the metal with big particle size partially blocked the micro-pores in the activated

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