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Structural evolution of calcium-exchanged (NH4)2SiF6-dealuminated Y zeolite after various chemical treatments |
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| Authors: | L Cherif F-Z El-Berrichi A Bengueddach P Tougne J Fraissard |
| Institution: | a Laboratoire de Catalyse et Synthèse Organique, University of Tlemcen, Tlemcen, Algeria b Laboratoire de Chimie des Matériaux, University of Oran, Oran, Algeria c Laboratoire SIEN-Physique Quantique, CNRS FRE 2312, E.S.P.C.I., 10 rue Vauquelin, 75231, Paris Cedex 05, France d Université Pierre et Marie Curie, Laboratoire SIEN-Chimie des Surfaces, CNRS FRE 2312, 4 place Jussieu, 75252, Paris Cedex 05, France |
| Abstract: | The structural evolution of Y zeolite (Si/Al 2.17) weakly dealuminated by hexafluorosilicate (Si/Al 3.13), denoted YD, and exchanged with calcium (CaYD), has been studied after acid–base treatments at 80 °C close to the cation exchange conditions. The stability of the samples was followed by X-ray diffraction and solid-state NMR of 29Si and 27Al; YD zeolite was completely destroyed by treatment with acid pH 2.5 and suffered serious degradation on treatment with alkali at pH 11.8. The introduction of calcium improved the stability of the zeolite in acid and base. In acid CaYD was not destroyed until pH 1. At pH 2, silicon and aluminium were extracted and an amorphous phase was formed. Base treatment at pH 13 did not affect the calcium-exchanged zeolite. |
| Keywords: | Zeolite Extra-framework silicon and aluminium Dealumination |
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