Nature of the active sites in Al-MCM-41 nano-structured catalysts for the selective rearrangement of cyclohexanone oxime toward epsilon-caprolactam

Vaschetto, EG; Pecchi, GA; Casuscelli, SG; Eimer, GA

Keywords: Al contents, Al-MCM-41, Silanol nests, Acidic strength, epsilon-Caprolactam

Abstract

Al-MCM-41 type nano-structured catalysts with different Al contents were prepared by direct hydrothermal synthesis. All the materials were characterized by XRD, N-2 adsorption, TEM, SEM, ICP-OES, FT-IR and adsorption of pyridine coupled to FT-IR spectroscopy. The relationship between the Al contents in the synthesis gel and final solid, the degree of Al introduction in tetrahedral coordination into the framework, the formation of nest silanols and the relative density of the acidic hydroxyl sites has been exhaustively analyzed. We could corroborate that hydroxyl groups present in silanol nests are the direct responsible of the weakly acid character of our materials. Moreover, a critical concentration of framework Al seems to be necessary to generate such nests, after which the acid sites density is strongly increased, according the framework Al amount increasing. The enhancement in the density of acidic nest silanols (active sites for the selective rearrangement of cyclohexanone oxime toward epsilon-caprolactam) reached by increasing the Al content, permitted to us achieve a cyclohexanone oxime conversion about 66%. The epsilon-caprolactam selectivity was 100% for all the evaluated catalysts, indicating that the acidic strength was kept sufficiently weak to not catalyze the forrriation of by-products. (C) 2014 Elsevier Inc. All rights reserved,

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Título según WOS: Nature of the active sites in Al-MCM-41 nano-structured catalysts for the selective rearrangement of cyclohexanone oxime toward epsilon-caprolactam
Título según SCOPUS: Nature of the active sites in Al-MCM-41 nano-structured catalysts for the selective rearrangement of cyclohexanone oxime toward ?-caprolactam
Título de la Revista: MICROPOROUS AND MESOPOROUS MATERIALS
Volumen: 200
Editorial: Elsevier
Fecha de publicación: 2014
Página de inicio: 110
Página final: 116
Idioma: English
DOI:

10.1016/j.micromeso.2014.08.030

Notas: ISI, SCOPUS - ISI