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Apport de la simulation dans l'optimisation de l'analyse quantitative par microsonde électronique de catalyseurs hétérogènes

Abstract : Electron Probe Micro Analysis (EPMA) is frequently used to measure the local concentration of active elements in heterogeneous catalysts. However, when classical procedures are used, a significant deficit is observed both in local total concentration and mean total concentrations. A Monte Carlo program simulating measured intensities (characteristic lines and continuous background) has been written using PENELOPE routines. We have included in this program models taking into account the different physical phenomena likely to lead to the observed signal loss (insulating properties, roughness, porosity, energy loss at interfaces). Simulation results have shown that an important roughness (Ra>200nm) was the only parameter apt to lead to a significant total signal loss. This led us to inquire into another origin to explain the signal loss observed on mesoporous samples. Measurements conducted on a mesoporous alumina confirmed that measuring aluminum, oxygen and carbon leads to a correct total of concentrations. Signal loss is thus explained by the contamination of the sample during its preparation, the components of the embedding resin diffusing into the porosity and reacting with the reactive surface of the catalyst support. In the case of macroporous catalysts, local roughness effect is very important. The simulations have shown the efficiency of the Peak to Background method to correct these local roughness effects. Measurements conducted on reforming and hydrotreating catalysts have led to a correct total concentration and confirmed the contribution of the Peak to Background method to achieve local quantitative measurement.
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Submitted on : Friday, January 9, 2004 - 11:10:26 AM
Last modification on : Saturday, November 9, 2019 - 1:33:50 AM
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  • HAL Id : tel-00004130, version 1

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Loïc Sorbier. Apport de la simulation dans l'optimisation de l'analyse quantitative par microsonde électronique de catalyseurs hétérogènes. Catalyse. Université Montpellier II - Sciences et Techniques du Languedoc, 2001. Français. ⟨tel-00004130⟩

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