Ormond Thomas K, Baraban Joshua H, Porterfield Jessica P, Scheer Adam M, Hemberger Patrick, Troy Tyler P, Ahmed Musahid, Nimlos Mark R, Robichaud David J, Daily John W, Ellison G Barney
National Renewable Energy Laboratory , 15013 Denver West Parkway , Golden , Colorado 80401 , United States.
Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309-0215 , United States.
J Phys Chem A. 2018 Jul 19;122(28):5911-5924. doi: 10.1021/acs.jpca.8b03201. Epub 2018 Jul 3.
The nascent steps in the pyrolysis of the lignin components salicylaldehyde ( o-HOCHCHO) and catechol ( o-HOCHOH) were studied in a set of heated microreactors. The microreactors are small (roughly 1 mm ID × 3 cm long); transit times through the reactors are about 100 μs. Temperatures in the microreactors can be as high as 1600 K, and pressures are typically a few hundred torr. The products of pyrolysis are identified by a combination of photoionization mass spectrometry, photoelectron photoion concidence mass spectroscopy, and matrix isolation infrared spectroscopy. The main pathway by which salicylaldehyde decomposes is a concerted fragmentation: o-HOCHCHO (+ M) → H + CO + CH═C═O (fulveneketene). At temperatures above 1300 K, fulveneketene loses CO to yield a mixture of HC≡C-C≡C-CH, HC≡C-CH-C≡CH, and HC≡C-CH═C═CH. These alkynes decompose to a mixture of radicals (HC≡C-C≡C-CH and HC≡C-CH-C≡CH) and H atoms. H-atom chain reactions convert salicylaldehyde to phenol: o-HOCHCHO + H → CHOH + CO + H. Catechol has similar chemistry to salicylaldehyde. Electrocyclic fragmentation produces water and fulveneketene: o-HOCHOH (+ M) → HO + CH═C═O. These findings have implications for the pyrolysis of lignin itself.
在一组加热的微反应器中研究了木质素成分水杨醛（邻羟基苯甲醛，o-HOCHCHO）和儿茶酚（邻苯二酚，o-HOCHOH）热解的初始步骤。微反应器很小（内径约1毫米×长3厘米）；通过反应器的停留时间约为100微秒。微反应器中的温度可高达1600 K，压力通常为几百托。热解产物通过光电离质谱、光电子光电离符合质谱和基质隔离红外光谱相结合的方法进行鉴定。水杨醛分解的主要途径是协同断裂：o-HOCHCHO（+M）→H + CO + CH═C═O（富烯酮烯）。在温度高于1300 K时，富烯酮烯失去CO生成HC≡C-C≡C-CH、HC≡C-CH-C≡CH和HC≡C-CH═C═CH的混合物。这些炔烃分解为自由基（HC≡C-C≡C-CH和HC≡C-CH-C≡CH）和H原子的混合物。H原子链反应将水杨醛转化为苯酚：o-HOCHCHO + H → CHOH + CO + H。儿茶酚具有与水杨醛相似的化学性质。电环化断裂产生水和富烯酮烯：o-HOCHOH（+M）→HO + CH═C═O。这些发现对木质素本身的热解有影响。
