CINDECA   05422
CENTRO DE INVESTIGACION Y DESARROLLO EN CIENCIAS APLICADAS "DR. JORGE J. RONCO"
Unidad Ejecutora - UE
artículos
Título:
ATR-FTIR Study of the Decomposition of Acetic Anhydride on Fosfotungstic Wells-Dawson Heteropoly Acid Using Concentration-Modulation Excitation Spectroscopy
Autor/es:
ALEJO AGUIRRE; ADRIAN L.. BONIVARDI; SILVANA MATKOVIC; LAURA BRIAND; SEBASTIÁN E. COLLINS
Revista:
TOPICS IN CATALYSIS
Editorial:
SPRINGER/PLENUM PUBLISHERS
Referencias:
Lugar: New York; Año: 2011 vol. 54 p. 229 - 229
ISSN:
1022-5528
Resumen:
The decomposition of acetic anhydride in liquid phase on a fosfotungstic Wells-Dawson heteropoly acid (HPA) was investigated by in situ ATR-FTIR spectroscopy. Transient and concentration-modulation excitation spectroscopy (MES) experiments in combination with phase-sensitive detection (PSD) were used to monitor the solid-liquid interface. The MES method is based on the periodic variation of a parameter of the reaction media such as, the reactant concentration. That periodic alteration causes varying infrared signals of the surface adsorbed species that are subsequently demodulated with the PSD methodology. Thus, the separation of the static signals from the changing ones is achieved, and species with different response can be observed in the spectra. Using MES-PSD coupled with ATR-FTIR, acetic anhydride was observed to decompose to acetic acid, acetate and acyl [CH3C(O)+] species, involving Brønsted acid sites of the HPA catalyst. The CH3C(O)+ is a very unstable intermediate species and it is the key intermediate in the Friedel-Crafts acylation reactions. Moreover, the acetate groups are spectator species since remain strongly adsorbed on the catalyst surface and do not further react.
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