Comparison of the properties and catalytic activity of commercially and laboratory prepared Mg/Al mixed oxides in aldol condensation of cyclohexanone with furfural

摘要

In recent years, for deeper understanding of the behavior of various heterogeneous catalysts, aldol condensation of acetone and furfural has been researched in detail. In this article, the carbonyl reactants are represented by cyclohexanone and furfural as the platform chemicals for synthesis the fundamental building blocks for future biorefineries. Our main goal was toexplore the structural and acid-base properties and to compare them with catalytic characteristics of Mg/Al mixed oxides in aldol condensation of cyclohexanone with furfural. Theaforesaidbasic heterogeneous catalysts were obtained by the calcination of commercially and laboratory prepared hydrotalcites with different molar ratios (1:1-5:1). Theirphysicochemical properties were determined based onseveral analytical methods: XRD,ICP-OES, SEM, N-2 physisorption, TGA, TGA-MS, DRIFT, TPD-CO2 and TPD-NH3. Through XRD, it was found that as-synthesized laboratory hydrotalcites had the pure crystalline hydrotalcite structure while commercial ones contained also the brucite andMgO phases. Byusing TPD-CO2 and TPD-NH3, themeasured values, especially the total amount of basic sites, provided the best correlation with the catalytic activity of investigated catalysts. Comparable conversions of furfural (ca. 87%) were achieved on laboratory and commercial mixed oxides with the Mg/Al molar ratio 1:1 and 3:1, respectively. They had noobvious difference inselectivity to FCH (about 20%) whereas the commercial samples showed higher selectivity to F2CH (26% at max conversion) than the laboratory ones (17%).