Reactions of d-fructose in water at temperatures up to 400 °C and pressures up to 100 MPa

Reactions of d-fructose in water at high temperatures (350 and 400 °C) and pressures (up to 100 MPa) were studied using a flow reactor. High temperature (400 °C) and moderate pressure (40 MPa) conditions enhanced the yields of retro-aldol related products such as glyceraldehyde, dihydroxyacetone and pyruvaldehyde. High temperature, high pressure conditions enhanced retro-aldol reactions and water related reactions such as hydrolysis and dehydration. Comparison between d-fructose and d-glucose experiments showed that higher yields for 5-HMF were obtained starting from d-fructose than d-glucose. Surprisingly, higher yields of furfural were obtained starting from d-glucose than from d-fructose which is contrary to reaction pathways in the hydrothermal literature. Based on the experimental results, a possible reaction scheme is proposed for water catalyzed (i) benzilic acid rearrangement reactions from pyruvaldehyde to lactic acid and (ii) retro-aldol reaction from d-glucose to furfural.