A Facile Synthesis Route to AuPd Alloys for the Selective Oxidation of 5- Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

Synthesis of 2,5-furandicarboxylic acid (FDCA) can be achieved via catalytic oxidation of 5-Synthesis of 2,5-furandicarboxylic acid (FDCA) can be achieved via catalytic oxidation of 5-hydroxymethylfurfural (5-HMF), in which both base and catalyst play important roles. This work presents the development of a simple synthesis method (based on a commercial parent 10 wt.% Pd/C catalyst) to prepare the bimetallic AuPd alloy catalysts (i.e., Au@Pd/C) for selective 5-HMF
oxidation to FDCA. When using the strong base of NaOH, Pd and Au cooperate to promote FDCA formation when deployed either separately (physical mixture of the monometallic Au/C and Pd/C catalysts) or ideally alloyed (Au@Pd/C), with full 5-HMF conversions and FDCA yields of 66% vs. 77%, respectively. However, NaOH also promoted the formation of undesired by-products, leading to poor mass balances (<81%). Comparatively, under weak base conditions (using NaHCO3), an
increase in Au loading in the Au@Pd/C catalysts enhanced the 5-HMF conversion rate and FDCA productivity (due to the enhanced carbonyl oxidation capacity) with high mass balances of >97%. Yet, the excessive Pd content in the Au@Pd/C catalysts was not beneficial to promote the FDCA formation.hydroxymethylfurfural (5-HMF), in which both base and catalyst play important roles. This work presents the development of a simple synthesis method (based on a commercial parent 10 wt.% Pd/C catalyst) to prepare the bimetallic AuPd alloy catalysts (i.e., Au@Pd/C) for selective 5-HMF oxidation to FDCA. When using the strong base of NaOH, Pd and Au cooperate to promote FDCA formation when deployed either separately (physical mixture of the monometallic Au/C and Pd/C catalysts) or ideally alloyed (Au@Pd/C), with full 5-HMF conversions and FDCA yields of 66% vs. 77%, respectively. However, NaOH also promoted the formation of undesired by-products, leading to poor mass balances (<81%). Comparatively, under weak base conditions (using NaHCO₃), an increase in Au loading in the Au@Pd/C catalysts enhanced the 5-HMF conversion rate and FDCA productivity (due to the enhanced carbonyl oxidation capacity) with high mass balances of >97%. Yet, the excessive Pd content in the Au@Pd/C catalysts was not beneficial to promote the FDCA formation.