HMF synthesis in aqueous and organic media under ultrasonication, microwave irradiation and conventional heating

5-Hydroxymethyl furfural (HMF) is known as a noteworthy platform in a biorefinery concept. HMF was prepared via fructose dehydration in aqueous and organic media, using three methods, i.e., conventional heating, ultrasonication and microwave irradiation. Water, methyl isobutyl ketone (MIBK), methyl ethyl ketone and ethyl acetate were used as media for HCl-catalyzed synthesis of HMF. FTIR and 1H-NMR spectroscopies were used for analysis. The synthesis yield and selectivity were investigated to optimize variables such as fructose concentration, catalyst dosage, temperature, irradiation power, solvent, and the reaction atmosphere. It was found that the yield in the organic media was superior to that of the aqueous ones. In addition, nitrogen atmosphere favored higher yield than air, due to lack of HMF oxidation. As conclusion, the highest yields of the conventional, ultrasonicated and microwave-assisted reactions were 87, 53, and 38%, respectively. In the reactions ultrasonically promoted, the reaction time scale was highly reduced from hours to minutes. The yield was varied with treatment times, so that ultrasonication was recognized to be the best approach in terms of yield, while the microwave method was the fastest one. Selectivity varied from 60 to 90% depending the reaction media and promotion method.