Iowa State University (ISU) researchers and their colleagues at the Iowa Energy Center have developed a novel process for converting cellulose and related materials to high-value chemicals with low molecular weights. The biomass conversion process is based on the chemistry of supercritical fluids.
Methods to hydrolyze cellulose and related carbohydrate materials for production of small molecules often require the use of harsh or expensive reagents such as strong acids or enzymes since cellulose is usually not soluble in conventional solvents and is also refractory to chemical or biological treatments. Conventional acid hydrolysis methods have also suffered from the high cost of building corrosion resistant plants, acid recovery, and generation of chemical wastes.
The ISU method, which involves heating under pressure a mixture of cellulose and low-molecular-weight alcohol, does not require pretreatment of the starting material and can be used to produce ethylene glycol, propylene glycol and other low molecular weight materials without the use of expensive reagents, metal catalysts, hydrogen gas or enzymes. In addition, this method produces alkyl glucosides and levoglucosan that can be converted into glucose for subsequent production of ethanol and other products.
All this happens without the use of any expensive reagents such as acids, enzymes, catalysts or hydrogen gas, ISU Professor Walter Trahanovsky said. The process even works when there are impurities in the biomass.
The ISU team has demonstrated efficient conversion of cellulose to ethylene glycol, propylene glycol, glucosides, and levoglucosan under laboratory conditions, and ISU is seeking partners interested in commercializing this technology. The Iowa State University Research Foundation Inc. has filed for a patent of the technology.
Trahanovsky and colleagues were studying the reactions of cellulosic materials in alcohols at high temperatures and pressures using nuclear magnetic resonance spectroscopy. Early experiments produced the expected sugar derivatives. Additional work, however, clearly revealed significant yields of ethylene glycol and propylene glycol.
It was a real surprise. These products were unexpected, so we never looked for them. But they were always there.—Walter Trahanovsky
Uses for ethylene glycol include auto antifreeze, polyester fabrics and plastic bottles. Propylene glycol has many uses, including as a food additive, a solvent in pharmaceuticals, a moisturizer in cosmetics and as a coolant in liquid cooling systems.
The research has been supported by grants from the Iowa Energy Center. Other Iowa State researchers who have contributed to the project include Ronald Holtan, a postdoctoral research associate in chemistry; Norm Olson, the project manager of the Iowa Energy Center’s BECON facility near Nevada; Joseph Marshall, a former graduate student; and Alyse Hurd and Kyle Quasdorf, former undergraduate students. Trahanovsky said the research team is still working to develop and improve the conversion technology.