Pyrolysis is a promising way to convert biomass into fuels and chemicals. This reaction is complex and inevitably involves a cascade of radical reactions that lead to char formation, in which some radicals become trapped and stabilized. Their nature is difficult to characterize, and in this respect computational chemistry can be a strong supplementary tool to electron spin resonance spectroscopy and other experimental methods. Here biomass char radicals and oxidation reactivity are studied experimentally, and density functional theory is used to predict the thermodynamic stability and g-values of carbon- and oxygen-centered radicals of polyaromatic char models including defect structures. Hydroxylated and especially certain dihydroxylated structures provide exceptional stabilization of oxygen-centered radicals. Hydrogen bonding plays a crucial role, and it is proposed that hydrogen atom transfer couples radical localizations. This is a new proposal on the structural requirements for stabilization of char radicals, which impacts our understanding of pyrolysis mechanisms and char reactivity.

中文翻译：

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稳定的基自由基的性质：结构和氢键键合要求的ESR和DFT研究。

热解是一种将生物质转化为燃料和化学物质的有前途的方法。该反应是复杂的，不可避免地涉及自由基反应的级联，导致形成焦炭，其中一些自由基被捕获并稳定下来。它们的性质难以表征，在这方面，计算化学可以成为电子自旋共振光谱法和其他实验方法的有力补充工具。在这里，对生物质炭自由基和氧化反应性进行了实验研究，并使用密度泛函理论预测了包括缺陷结构在内的多芳烃炭模型中以碳和氧为中心的自由基的热力学稳定性和g值。羟基化，尤其是某些二羟基化的结构提供了以氧为中心的自由基的出色稳定性。氢键起着至关重要的作用，并且提出氢原子转移耦合自由基的局部化。这是关于稳定炭自由基的结构要求的新建议，这影响了我们对热解机理和炭反应性的理解。