title: Quantitative investigation of free radicals in bio-oil and their potential role in condensed-phase polymerization.
abstract: We report on the quantitative analysis of free radicals in bio-oils produced from pyrolysis of cellulose, organosolv lignin, and corn stover by EPR spectroscopy. Also, we investigated their potential role in condensed-phase polymerization. Bio-oils produced from lignin and cellulose show clear evidence of homolytic cleavage reactions during pyrolysis that produce free radicals. The concentration of free radicals in lignin bio-oil was 7.5×10(20)  spin g(-1), which was 375 and 138 times higher than free-radical concentrations in bio-oil from cellulose and corn stover. Pyrolytic lignin had the highest concentration in free radicals, which could be a combination of carbon-centered (benzyl radicals) and oxygen-centered (phenoxy radicals) organic species because they are delocalized in a π system. Free-radical concentrations did not change during accelerated aging tests despite increases in molecular weight of bio-oils, suggesting that free radicals in condensed bio-oils are stable.
authors: Bioeconomy Institute, Iowa State University, 1140E Biorenewables Research Lab, Ames, IA 50010 (USA), Fax: (+1) 515-294-3091; Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA 50010 (USA).
authors: Kwang Ho
authors: KH
authors: Kim
authors: Xianglan
authors: X
authors: Bai
authors: Sarah
authors: S
authors: Cady
authors: Preston
authors: P
authors: Gable
authors: Robert C
authors: RC
authors: Brown
mesh_terms: D056804:Biofuels; D005609:Free Radicals / Q000737:chemistry; D008031:Lignin / Q000737:chemistry; D058105:Polymerization; D013997:Time Factors
chemical_list: D056804:Biofuels; D005609:Free Radicals; C036909:lignocellulose; D008031:Lignin
keywords: biomass; cleavage reactions; epr spectroscopy; polymerization; radicals