Pyrolysis Mechanism Study of Lignin Model Compounds by Synchrotron Vacuum Ultraviolet Photoionization Mass Spectrometry
Pyrolysis Mechanism Study of Lignin Model Compounds by Synchrotron Vacuum Ultraviolet Photoionization Mass Spectrometry
复制标题
同步加速器真空紫外光电离质谱法研究木质素模型化合物的热解机理
DOI：
10.1021/acs.energyfuels.5b02635
复制
发表时间：
2016-03-01
期刊：
影响因子：
5.3
通讯作者：
Wu, Jinhu
中科院分区：
文献类型：
--
作者：
He, Tao;Zhang, Yimeng;Wu, Jinhu
为了研究木质素的热解机理，在350-500 ℃下，利用同步辐射真空紫外光电离飞行时间质谱（SVUV PIMS）对两种α-O-4和一种完全取代的β-O-4木质素二聚体模型化合物进行了研究。碰撞减少的真空条件下，在原位特性，和“软”电离技术，该反应器系统允许直接检测的热自由基和高沸点化合物。对于α-O-4型化合物4-苄氧基苯酚（BOP）的热解，证实了苄基自由基、对半醌自由基、甲苯和联苄基的存在，为自由基主导机理提供了有力证据。对甲氧基取代的实验表明，对甲氧基取代能降低BOP的C-芳香-C α和醚C-芳香键的离解能。对于β-O-4型化合物愈创木基甘油-β-愈创木基醚（GGGE），在实验温度范围内，C-O均裂机理较小，协同反应占主导地位。此外，进行平行实验，以找到温度对产物分布的影响;它表明，高温导致的初级产品的进一步分解和醛和酮组分的增加。
To investigate the lignin pyrolysis mechanism, two a alpha-O-4 and one completely substituted beta-O-4 lignin dimeric model compounds were studied using in situ synchrotron vacuum ultraviolet photoionization time-of-flight mass spectrometry (SVUV PIMS) at 350-500 degrees C. The collision-reduced vacuum condition, in situ characteristic, and "soft" ionization technique of this reactor system allowed for the direct detection of thermolysis radicals and high-boiling-point compounds. For the alpha-O-4 compound 4-(benzyloxy)phenol (BOP) pyrolysis, benzyl radical, p-semiquinone radical, toluene, and bibenzyl were confirmed, supplying firm evidence for the free radical dominant mechanism. Experiments of the p-methoxy substituent on the hydroxyl position of BOP show that the p-methoxy substituent can lower the C-aromatic -C alpha and ether C-aromatic bond dissociation energies. For beta-O-4 compound guaiacylglycerol-beta-guaiacyl ether (GGGE), it is inferred that the C-O homolysis mechanism was minor and the concerted reaction dominated in the experimental temperature range. Also, parallel experiments were conducted to find the temperature effect on the product distribution; it reveals that a high temperature leads to the further decomposition of the primary products and an increase of the aldehyde and ketone components.