In additional experiments, the team tested how well their method compared to acid, a common way to break down cellulose. The metal chlorides-ionic liquid system worked ten times faster than the acid and at much lower temperatures. In addition, the paired metal chloride catalysts allowed Zhang's research team to avoid using another compound under investigation, a mineral acid, that is known to degrade HMF.
Optimizing their method, the team found that they could consistently achieve a high yield of HMF -- the method converted about 57 percent of the sugar content in the cellulose feedstock to HMF through this single step process. The team recovered more than 90% of the HMF formed, and the final product from the process was 96% pure.
In addition, the metal chlorides and ionic liquid could be reused multiple times without losing their effectiveness. Being able to recycle the materials will lower the cost of HMF production.
"This paper is a tremendous breakthrough. By combining the cellulose-breakdown and sugar-conversion steps, we are very close to a single-step method of converting raw biomass into a new platform chemical -- a chemical you can readily turn into a transportation fuel or for synthesis of plastics and other useful materials," said PNNL geochemist and study coauthor Jim Amonette. "Advances like this can help reduce our dependence on fossil fuels."
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory