Characterization of Bio-oils Produced from Fast Pyrolysis of Corn Stalks in an Auger Reactor

• Published in: Energy & fuels 2012-06, Vol.26 (6), p.3816-3825
• Main Authors: Pittman, Charles U, Mohan, Dinesh, Eseyin, Anthonia, Li, Qi, Ingram, Leonard, Hassan, El-Barbary M, Mitchell, Brian, Guo, Hua, Steele, Philip H
• Format: Article
• Language: English
• Subjects: Augers; Combustion; Corn; Density; Gel permeation chromatography; Pyrolysis; Reactors; Wood
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef3003922

Corn stalks were converted to bio-oils by fast pyrolsis in an auger fed reactor at 400 and 450 °C. Both acid-pretreated and untreated corn stalks were pyrolyzed. Proximate and ultimate analyses of the corn stalk feeds and bio-oils were performed, and the bio-oils were characterized by gas chromatography/mass spectrometry (GC/MS), gel permeation chromatography (GPC), 13C and 1H NMR spectroscopy, pH, ash, and viscosity measurements, and solids content and water analyses. Corn stalks have lower lignin content than wood, leading to lower bio-oil yields, more water produced and different chemical compositions than pine wood bio-oil generated in the same auger reactor. Acid pretreatment of stalks increased the bio-oil yields and decreased the char yields at both pyrolysis temperatures. Acid-treated stalks had lower water content, and pH, viscosity, and filterable solid values were lower than those of bio-oil from untreated stalks. Several compounds found in the bio-oil from untreated stalks were not detected in the bio-oil from acid-treated stalks. Thirty two compounds were quantitated in the GC/MS analysis of the two bio-oils. Gel permeation chromatography analysis indicated the presence of a significant fraction of high boiling point compounds that did not pass through the GC columns with bio-oils from both pretreated and untreated stalks. Weight averaged molecular weights of 490 and 530 for acid-treated and untreated stalks, respectively, were indicated by GPC. Portable auger reactors might be used for local production of corn stalk bio-oils during harvest, thereby avoiding the need to transport bulky, low density corn stalk or stover biomass to biorefineries or power generation units.