Engineers at the University of Wisconsin-Madison have developed a two-stage process for converting biomass-derived sugar into 2,5-dimethylfuran (DMF), a liquid transportation fuel with 40% greater energy density than ethanol.
The work by Professor James Dumesic and his research team, reported in the 21 June issue of the journal Nature, leverages the process they developed last year for the production of the chemical intermediate hydroxymethylfurfural (HMF) from sugar. (Earlier post.)
In addition to its higher-energy content, DMF also addresses other ethanol shortcomings. DMF is not soluble in water and therefore cannot become contaminated by absorbing water from the atmosphere. DMF is stable in storage and, in the evaporation stage of its production, consumes one-third of the energy required to evaporate a solution of ethanol produced by fermentation for biofuel applications.
The first stage of the DMF process is the conversion of sugar to HMF in water using an acid catalyst in the presence of a low-boiling-point solvent. The solvent extracts HMF from water and carries it to a separate location. Although other researchers had previously converted fructose to HMF, Dumesic’s research group made a series of improvements that raised the HMF output and made the HMF easier to extract. For example, the team found that adding salt (NaCl) dramatically improves the extraction of HMF from the reactive water phase and helps suppress the formation of impurities.
The next step is the conversion of HMF to DMF over a copper-based catalyst. The conversion removes two oxygen atoms from the compound lowering the boiling point and making it suitable for use as transportation fuel. Salt, while improving the production of HMF, presented an obstacle in the production of DMF by contributing chloride ions that poisoned the conventional copper chromite catalyst. The team instead developed a copper-ruthenium catalyst providing chlorine resistance and superior performance.
Dumesic says more research is required before the technology can be commercialized. For example, while its environmental health impact has not been thoroughly tested, the limited information available suggests DMF is similar to other current fuel components.
There are some challenges that we need to address, but this work shows that we can produce a liquid transportation fuel from biomass that has energy density comparable to petrol.—James Dumesic
Earlier this month, a team of researchers at the Pacific Northwest National Laboratory (PNNL) reported in the journal Science on their work to convert glucose directly to HMF. (Earlier post.)
"“Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates”; Yuriy Román-Leshkov, Christopher J. Barrett, Zhen Y. Liu and James A. Dumesic; Nature 447, 982-985 (21 June 2007) | doi:10.1038/nature05923