(668d) Thermal Deconstruction Opens Biomass for Acid Hydrolysis to Sugars

Lindstrom, J. K., Iowa State University
Ciesielski, P. N., National Renewable Energy Laboratory
Peterson, C., Iowa State University
Proano-Aviles, J., Iowa State University
Gable, P. A., Iowa State University
Brown, R. C., Iowa State University
We have explored thermal deconstruction, which involves rapidly heating then cooling biomass in an inert environment before complete pyrolysis can occur. While we produce some bio-oil and light gases, solid or liquid phase reactions greatly modify our biomass. As shown through our microscopy and chemical analysis, thermal deconstruction cracks the biopolymers and loosens their lignocellulosic structure. This change allows molecules to diffuse more readily into and out of the biomass. Additionally, we have proven that as the biopolymers fragment into oligomers they become more susceptible to further depolymerization reactions. In particular, when cellulose is thermally deconstructed it rapidly forms anhydro-oligosaccharides—oligosaccharides where the reducing end has dehydrated. We can hydrolyze these oligomers to glucose under more mild conditions than required for untreated cellulose. Dilute sulfuric acid catalyzes hydrolysis—primarily in cellulose and hemicellulose oligomers—producing glucose and xylose, which can be fermented to ethanol or other products. Our process allows for higher monosaccharide yields than those obtainable from fast pyrolysis.