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Comprehensive Utilization of Hemicellulose and Cellulose To Release Fermentable Sugars from Corncobs via Acid Hydrolysis and Fast Pyrolysis

Jiang, Liqun, Wu, Nannan, Zheng, Anqing, Liu, Anqi, Zhao, Zengli, Zhang, Fan, He, Fang, Li, Haibin
ACS sustainable chemistry 2017 v.5 no.6 pp. 5208-5213
acid hydrolysis, alkaline earth metals, biomass, biorefining, cellulose, corn cobs, cost effectiveness, fermentation, lignocellulose, polymers, pyrolysis, raw materials, sugars, sulfuric acid, temperature, xylan
Conversion of lignocellulose to sugars suitable for microbial fermentation is an outstanding obstacle in developing biorefinery. Both hemicellulose and cellulose fractions are polymers of sugars and thereby primary candidates for fermentable sugars production. In this study, the flexibility of an integrated biomass conversion process was offered. The hemicellulose of corncobs was utilized to release fermentable sugars by sulfuric acid hydrolysis first. The remaining solid residue from acid hydrolysis, containing a lot of cellulose, was further used to produce levoglucosan by fast pyrolysis. This process appeared to present several advantages: (i) Almost all of hemicellulose (99.7%) was hydrolyzed, and the yield of xylan was achieved 86.1%. (ii) The alkali and alkaline earth metals, which had negative catalytic influence on levoglucosan formation, were nearly and completely (93.7%) removed by acid pretreatment. (iii) A preferential degradation of hemicellulose and amorphous cellulose during acid hydrolysis resulted in accumulation of crystalline cellulose of acid-pretreated biomass, which was favorable for levoglucosan production. (iv) The yield of levoglucosan increased by 450.0% for acid-pretreated corncobs (37.4%) compared with that of raw material (6.8%). The effectiveness to enhance levoglucosan yields ranged as high as 63.4%. Further increase in sulfuric acid concentration (0–10%) and temperature (30–120 °C) in acid pretreatment prior to fast pyrolysis could enhance levoglucosan formation. Consequently, this strategy, which utilized simple chemical regents to overcome biomass recalcitrance and liberate fermentable sugars while also remaining cost-effective, has the potential to underlie a biorefinery.