Catalytic Hydrogenation/Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran.

Recent developments in transformations of biobased 5-hydroxymethylfurfural to 2,5-dimethylfuran, a potential liquid fuel, are critically summarized. The highest yield of 2,5-dimethylfuran (more than 98 %) from 5-hydroxymethylfurfural are obtained over bimetallic Cu-Co supported on carbon at 180 °C under 5 bar hydrogen in 2-propanol and over Ni supported on mesoporous carbon at 200 °C under 30 bar hydrogen in water in a batch reactor. The desired catalyst should have relatively high metal dispersion and some acidity to facilitate both hydrogenation and hydrogenolysis. However, overhydrogenation and overhydrogenolysis forming 2,5-dimethyltetrahydrofuran and methylfuran, respectively, should be suppressed. Furthermore, a hydrophobic support is more selective than oxide-based support. After a careful adjustment of the residence time in a continuous reactor it is also possible to produce high yields of 2,5-dimethylfuran even over Pt/C. The main challenges limiting the industrial feasibility of these reactions are relatively low initial reactant concentration, catalyst deactivation by sintering, leaching and coking. In addition to selection of optimum reaction conditions and catalyst properties, kinetic modelling was also summarized.