Hydrodeoxygenation of Fructose to 2,5-Dimethyltetrahydrofuran Using a Sulfur Poisoned Pt/C Catalyst

Fructose has been hydrodeoxygenated to 2,5-dimethyltetrahydrofuran using a sulfided Pt/C catalyst. The reaction was carried out in a stirred reactor at 10.3 MPa H-2 and 175 degrees C which allowed a 10% fructose solution to be converted in 2 h. The selectivity was greatly enhanced by using ethanol as solvent with 95% ethanol giving 50% DMTHF versus 9% in water. The only intermediate found along the reaction pathway was 2,5-hexanedione. This is presumed to be hydrogenated to 2,5-hexanediol which then ring closes to DMTHF. Molecular simulation at the B3LYP/6-311++G(2df,2p) level was used to propose a reaction pathway from fructose to 2,5-hexanedione and then to explain the preference for the cis isomer of DMTHF.