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Type: Artigo de periódico
Title: Tuning The Acidic Properties Of Aluminas Via Sol-gel Synthesis: New Findings On The Active Site Of Alumina-catalyzed Epoxidation With Hydrogen Peroxide
Author: Rinaldi R.
Fujiwara F.Y.
Holderich W.
Schuchardt U.
Abstract: This study answers several pending questions about alumina-catalyzed epoxidation with aqueous 70 wt% H2O2. To evaluate the effect of the water-to-aluminum tri-sec-butoxide molar ratio, this was systematically changed from 1 to 24. The xerogels were calcined at 450 °C and gave different γ-Al2O3's with distinct textural and acidic properties. A combination of 27Al MAS NMR and TPD-NH3 results of calcined aluminas allowed us to assign the type Ia Al{single bond}OH sites as the catalytic sites for epoxidation. The type Ib Al{single bond}OH sites have no function in catalytic epoxidation, because ethyl acetate poisons these sites. The strong acid sites of types IIa, IIb, and III Al{single bond}OH groups are responsible for the undesired H2O2 decomposition and decreased oxidant selectivity. © 2006 Elsevier Inc. All rights reserved.
Rights: fechado
Identifier DOI: 10.1016/j.jcat.2006.08.024
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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