Aerobic oxidation of 1,6-hexanediol to adipic acid over Au-based catalysts: the role of basic supports

Abstract

1,6-Hexanediol is one of the most relevant building blocks originating from biomass and it transforms into adipic acid for polymer synthesis. Herein, we examine the selective oxidation of 1,6-hexanediol to adipic acid over Au-based catalysts, in the aqueous phase, under base-free conditions. Particularly, the absence of a base allows the neutralization step at the end of the reaction to be avoided. The influences of various supports (MgO, BaO, NiO, and TiO₂) and substrate/gold molar ratios were studied. Under the conditions used, the leaching of Mg in the mixture of MgF₂ and MgO was limited by diluting the basic sites in the support. The highest selectivity to adipic acid (43%) was achieved at 110 °C under 15 bar of air in the presence of 2 wt% Au/0.6MgF₂–0.4MgO.