Facile synthesis of CeO2-supported gold nanoparticle catalysts for selective oxidation of glycerol into lactic acid

This study explores a new synthetic route toward CeO2-supported gold nanoparticles catalysts (1, 3, and 5 wt.% Au) and their catalysis of the oxidation of glycerol at atmospheric pressure. Gold was loaded on a hydrothermally synthesized nanocrystalline CeO2 support (similar to 8 nm) via deposition-precipitation with urea (DPU). To obtain cerium oxide-supported gold nanoparticles, thermal reduction at 300 degrees C under flowing H-2 is currently popular. However, this method invariably forms small gold particles (<5 nm) even with higher gold loading. In the present study, Au/CeO2 catalysts prepared by DPU were reduced via a new method: chemical reduction with glycerol (CRG). Interestingly, the reduction of a gold-urea complex supported on ceria occurs at 25 degrees C, and the gold nanoparticles grow slowly. The resultant chemically reduced samples were compared with their hydrogen-reduced counterparts. The CRG method primarily generated gold particles with larger average sizes than the H-2 reduction method. Importantly, the CRG route enabled variation of the average gold nanoparticle size without requiring any other reagent, which is particularly advantageous for the Au/CeO2 system. The efficiency of these catalysts toward the aerobic oxidation of glycerol was tested. Accordingly, the selective oxidation of glycerol into lactate can be effectively catalyzed by Au/CeO2 catalysts at atmospheric pressure. The chemically reduced samples show increased lactate selectivity than the hydrogen-reduced samples due to the larger size of the gold particles. (C) 2013 Elsevier B.V. All rights reserved.