Researchers discover cellulose conversion benefits of ionic liquid
Eugene Chen, professor of chemistry, and Xianghong Qian, an assistant professor of mechanical engineering, discovered that ionic liquids-salts that melt at low temperatures-mixed with a suitable amount of water convert biomass directly to sugars. They made the discovery unexpectedly while examining the effects of ionic liquids as solvents when used together with acid catalysts, according to Chen. "We discovered that [ionic liquid]-water mixtures are actually trifunctional, serving as solvent (IL), reagent (water), and catalyst (intrinsic, suitable acidity of the IL-water mixture)," he said.
The acidity of ionic liquid-water mixtures Chen and Qian discovered was previously unrecognized but is now found suitable for conversion of biomass into sugars without common side reactions or additional catalysts. The process also eliminates environmental concerns over acids, creates a homogenous reaction, and has high conversion yields, along with the benefits of using a recyclable material.
"ILs are currently expensive, so they must be recovered, recycled and reused," Chen said. "We have demonstrated the recyclability of ILs in the conversion process albeit in a small, laboratory scale."
After conversion to sugars, the next step is to use a metal catalyst to convert the sugars to 5-hydroxylmethyl furfural (HMF), which leads to biofuel with considerably higher energy density than current ethanol-based biofuel, Chen said. But the ionic liquid solvents can also convert the biomass directly to HMF in the presence of the metal catalyst, he added.
A paper on the work was published in the American Chemical Society journal Energy & Fuels. The next goal in the research is to investigate and increase the conversion of lignocellulosic biomass, such as untreated corn stover and pine wood, into sugars and HMF, Chen said.