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Issue 1, 2010
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A UV-Vis micro-spectroscopic study to rationalize the influence of Cl(aq) on the formation of different Pd macro-distributions on γ-Al2O3 catalyst bodies

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Abstract

The influence of the Cl(aq) concentration, solution pH and equilibration time on the PdCl42−(aq) dynamics and molecular structure after impregnation of γ-Al2O3 catalyst bodies has been studied using UV-Vis micro-spectroscopy. To do so, 0.2 wt% Pd catalysts have been prepared from acidic solutions (pH 1 and 5) of the Na2PdCl4 precursor salt with different amounts of NaCl. It was found that egg-shell catalysts are obtained when a less acidic pH (pH 5) is combined with [Cl(aq)] < 0.6 M and less than 24 h of equilibration time are implemented, while to achieve egg-white catalysts the solution pH should be 1. Moreover, by increasing the equilibration time up to 96 h, the egg-shell profiles vanish to provide a uniform Pd distribution, while the egg-white distribution becomes egg-yolk. Additionally, Pd complexes appeared with different molecular structures depending on the solution pH, equilibration time and macro-distribution achieved. The protocol developed to create different Pd macro-distributions has been applied to prepare two 1 wt% Pd/γ-Al2O3 egg-shell and egg-white catalysts. The Pd dynamics and molecular structure have been followed after impregnation, drying and calcination, demonstrating that the profiles created after impregnation are retained.

Graphical abstract: A UV-Vis micro-spectroscopic study to rationalize the influence of Cl−(aq) on the formation of different Pd macro-distributions on γ-Al2O3 catalyst bodies

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Article information


Submitted
31 Jul 2009
Accepted
05 Oct 2009
First published
07 Nov 2009

Phys. Chem. Chem. Phys., 2010,12, 97-107
Article type
Paper

A UV-Vis micro-spectroscopic study to rationalize the influence of Cl(aq) on the formation of different Pd macro-distributions on γ-Al2O3 catalyst bodies

L. Espinosa-Alonso, K. P. de Jong and B. M. Weckhuysen, Phys. Chem. Chem. Phys., 2010, 12, 97
DOI: 10.1039/B915753K

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