Kim Kwang Ho, Bai Xianglan, Cady Sarah, Gable Preston, Brown Robert C
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).
ChemSusChem. 2015 Mar;8(5):894-900. doi: 10.1002/cssc.201403275. Epub 2015 Feb 11.
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.
我们通过电子顺磁共振光谱法对纤维素、有机溶剂法木质素和玉米秸秆热解产生的生物油中的自由基进行了定量分析。此外，我们还研究了它们在凝聚相聚合中的潜在作用。木质素和纤维素产生的生物油在热解过程中显示出明显的均裂反应证据，产生了自由基。木质素生物油中自由基的浓度为7.5×10(20) 自旋 g(-1)，分别比纤维素和玉米秸秆生物油中的自由基浓度高375倍和138倍。热解木质素的自由基浓度最高，可能是碳中心（苄基自由基）和氧中心（苯氧基自由基）有机物种的组合，因为它们在π体系中离域。尽管生物油分子量增加，但在加速老化试验中自由基浓度并未改变，这表明凝聚生物油中的自由基是稳定的。
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