IBN Team Uses Imidazolium Salts in Catalyst System to Convert Sugars into HMF Biohydrocarbon Fuel Intermediate

12 December 2008

The NHC-Cr catalytic system has produced the highest reported HMF yields yet from both fructose and glucose. Click to enlarge.

Scientists at the Institute of Bioengineering and Nanotechnology (IBN) in Singapore have used imidazolium salts (IMSs) to develop a new efficient catalytic system for converting sugars into 5-hydroxymethylfurfural (HMF), a key intermediate compound that can be used to produce bio-derived hydrocarbon fuels. Commonly used as solvents for various organic reactions, imidazolium salts are room-temperature ionic liquids that are chemically stable and have low vapor pressure.

In a separate study, IBN researchers uncovered new redox properties of IMSs, which suggest that they could play an important role in disease prevention and treatment. A paper on the IMS-based catalytic system was published in Angewandte Chemie International Edition; a paper on the study of the redox properties of IMSs was published in the Journal of the American Chemical Society.

HMF and its 2,5-disubstituted furan derivatives can replace key petroleum-based building blocks, and there are several known catalysts that are active in the dehydration of sugars to form HMF. However, most of them also produce side reactions that form undesired byproducts, and rehydrate HMF to form acid. The use of these catalysts has often been constrained to simple sugar feedstock such as fructose as they have not been able to efficiently convert glucose, a more abundant and stable sugar source.

With IMSs as the starting point, IBN researchers developed NHC-metal (N-heterocyclic carbene) complexes as catalysts to transform sugars into HMF. These offer a great deal of flexibility as the catalytic activity may be modified by changing specific properties of the NHC. The researchers were able to extract HMF easily as the sole product. IBN’s new catalyst achieved the highest reported yields of HMF so far, for both fructose and glucose feedstocks.

Our HMF yields were as high as 96% for fructose and 81% for glucose. As both the catalyst and the ionic liquid can be recycled, our technology is more environmentally friendly and would potentially lead to cost savings in the biofuel manufacturing process.

—Dr Yugen Zhang

Prof. James Dumesic and his colleagues at the University of Wisconsin have shown an overall carbon yield from fructose to C₇-C₁₅ alkanes of 58-69% for HMF-acetone systems, and of 79-94% from various furfurals. Dumesic and his team produced alkanes of higher targeted molecular weight by first converting sugars into furfural compounds through dehydration reactions and by producing ketones and aldehydes through carbonyl formation reactions. Subsequent dehydration reactions lead to the removal of oxygen by production of water, and reduction reactions lead to the hydrogenation of the double bonds formed by dehydration. Hydrogen required for the reactions is produced from the sugar and water by evolution of CO₂. (Earlier post.)

Resources

• G. Yong, Y. Zhang and J. Y. Ying (2008) Efficient Catalytic System for the Selective Production of 5-Hydroxymethylfurfural from Glucose and Fructose. Angewandte Chemie International Edition, 47 (2008) 9345-9348 doi: 10.1002/anie.200803207