Fan Yuyang, Lei Ming, Zhang Zhengxue, Kong Xiangchen, Xu Weicong, Han Yue, Li Ming, Liu Chao, Xiao Rui
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
Bioresour Technol. 2021 Dec;342:125944. doi: 10.1016/j.biortech.2021.125944. Epub 2021 Sep 14.
Whether lignin benzyl hydroxyl shielding could promote its pyrolysis to phenolic compounds was investigated in this paper. Lignin benzyl hydroxyl was first preoxidized by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and stabilized by propionaldehyde respectively, then pyrolysis was conducted with milled wood lignin as a control. Organic stable radicals in pyrolytic chars were further detected to reveal lignin pyrolysis chemistry. Results showed that benzyl hydroxyl shielding process weakened lignin thermal stability, and decreased liquid yields regardless of the frequency of lignin β-O-4 linkages. In addition, char yield grew after benzyl hydroxyl shielding. Radical concentration was inversely proportional to β-O-4 content which indicated the non-negligible impact of shielded benzyl hydroxyl on lignin pyrolysis. Furthermore, gases from propionaldehyde stabilized lignin quenched its radicals. This work confirmed that lignin β-O-4 linkages and shielded benzyl hydroxyl both played the great role in radical-mediated pyrolysis, but the enhancement of liquid products could not be achieved via benzyl hydroxyl shielding.
本文研究了木质素苄基羟基屏蔽是否能促进其热解生成酚类化合物。首先用2,3-二氯-5,6-二氰基-1,4-苯醌对木质素苄基羟基进行预氧化，并用丙醛进行稳定化处理，然后以磨木木素为对照进行热解。进一步检测热解炭中的有机稳定自由基，以揭示木质素的热解化学过程。结果表明，苄基羟基屏蔽过程削弱了木质素的热稳定性，且无论木质素β-O-4键的频率如何，均降低了液体产率。此外，苄基羟基屏蔽后焦炭产率增加。自由基浓度与β-O-4含量成反比，这表明被屏蔽的苄基羟基对木质素热解有不可忽视的影响。此外，丙醛稳定化木质素产生的气体淬灭了其自由基。这项工作证实，木质素β-O-4键和被屏蔽的苄基羟基在自由基介导的热解中都起着重要作用，但通过苄基羟基屏蔽无法实现液体产物的增加。
