Biomass into chemicals: One pot-base free oxidative esterification of 5-hydroxymethyl-2-furfural into 2,5-dimethylfuroate with gold on nanoparticulated ceria

2,5-Dimethylfuroate (DMF) is a valuable biomass derivative that can replace oil dependent PET polymers. 5-Hydroxymethyl-2-furfural (HMF) has been selectively converted into DMF (99mol% yield) under mild conditions (65–130°C, 10bar O2) in the absence of any base, by using gold nanoparticles on nanoparticulated ceria. The catalyst can be reused several times without any loss of activity or selectivity. The absence of metal leaching has been checked by the three-phase test. A full reaction scheme has been established and it has been found that the rate-limiting step of the reaction is the alcohol oxidation into aldehyde. After this, the reaction proceeds via aldehyde conversion into hemiacetal and further oxidation into the corresponding ester. Additionally, the effect of temperature, substrate-to-catalyst ratio, alcohol and water has been studied in an attempt to explain the catalytic behaviour of the Au–CeO2.