Comparison of two MCM-41 grafted TEMPO catalysts in selective alcohol oxidation

A new heterogeneous system for catalytic oxidations has been developed by i mmobilising TEMPO onto ordered mesoporous silica (MCM-41-type). The immobil isation was performed according to different methods: (i) direct grafting o f the silica surface with 3-(trimethoxysilyl)propyloxy-TEMPO obtained by co upling LC-hydroxy-TEMPO and allyl bromide followed by hydrosilylation; (ii) coupling of 4-carboxy-TEMPO with 3-aminopropylsilane previously grafted on the mesoporous silica surface; (iii) coupling of the N-succinimide ester o f 4-carboxy-TEMPO with the same previously grafted 3-aminopropylsilane. Eff iciency and anchoring of the TEMPO were studied by various spectroscopic te chniques. The textural characteristics of the mesoporous support were prese rved during the different modifications. Catalytic tests on the use of the materials in the oxidation of primary alcohols proved their activity and st ability under the reaction conditions. (C) 2001 Elsevier Science B.V. All r ights reserved.