Dehydration of fructose into 5-hydroxymethylfurfural in a biphasic system using EDTA as a temperature-responsive catalyst

The widely available reagent ethylenediaminetetraacetic acid (EDTA) was used as a temperature-responsive catalyst to produce 5-hydroxymethylfurfural (HMF) from fructose. Using this catalyst, a remarkable HMF yield of 89 ± 3% was achieved in a water-MIBK biphasic system containing polyvinylpyrrolidone (PVP) and 2-butanol. The pH of the reaction system based on EDTA as a catalyst was shown to be temperature-responsive. Moreover, the EDTA catalyst could be recycled simply by cooling the reaction liquid to room temperature due to its temperature-dependent solubility in water. A slight decrease in the yield of HMF (from 89 ± 3 to 81 ± 2%) was observed after EDTA repeated use for five cycles, and a yield of 88 ± 2% was achieved again after purification of the recycled EDTA via recrystallization with NaOH/HCl. The FTIR spectrum of recycled EDTA was almost the same as that of fresh catalyst, and TG analysis showed the decomposition temperature of EDTA is about 260 °C. Furthermore, a leaching test revealed that only 4.3 ± 0.2% of the initial EDTA was lost after five-time reuse.