Carbon integral honeycomb monoliths as support of copper catalysts in the Kharasch–Sosnovsky oxidation of cyclohexene

Abstract

Carbon integral honeycomb monoliths prepared from a natural coal were employed as support of copper catalysts for organic synthetic purposes. In particular good to excellent yields (60–100% as function of the carboxylic acid employed) were obtained in the preparation of allylic esters by the Kharasch–Sosnovsky oxidation of cyclohexene. Different characterization techniques such as chemical analysis by Inductively Coupled Plasma Spectroscopy, nitrogen physisorption, X-ray Diffraction with Rietveld analysis, X-ray Photoelectron and Raman Spectroscopies, Temperature-Programmed Reduction and Scanning Electron Microscopy allowed finding that key parameters such as textural properties, degree of copper precursor decomposition and active phase homogeneity and dispersion can be modulated as function of a simple synthetic variable: the method used to dry the monoliths after impregnation with the metal precursor, either conventional or using microwaves. The results obtained allow understanding the key role of the nature and chemical surrounding (O2 anions or OH groups) of Cu2+ ions in the catalytic activity in the reaction investigated as well as the operating deactivation mechanisms. The use of the structured catalysts here proposed also opens up an interesting alternative to homogeneous catalysis in the field of organic synthesis.