木质素模化物苯二酚的裂解实验与芳基开环机理分析

Pyrolysis of benzenediol as lignin molds compounds and mechanism analysis of aryl ring-opening reactions

以邻苯二酚、对苯二酚和间苯二酚为木质素模化物进行居里点裂解实验,利用气相色谱仪和气相-质谱联用仪进行产物检测.实验结果显示:对苯二酚裂解首先形成1,4-苯醌,开环后主要生成CO(1.6%,质量分数,以下同)和C 2烃(2.7%)、C 4烃(2.8%);邻苯二酚在670℃可检测到苯乙烯,开环产物主要为C 4烃(5.2%)和CO(3.1%);间苯二酚开环反应后,CO和CO 2产量均较高,分别为2.2%和1.7%,且C 1烃~C 5烃无明显偏向(1.1%~2.2%),其开环反应涉及CO和CO 2两条反应路径,裂解过程较为复杂.基于3种苯二酚裂解产物的分布情况,分析木质素裂解过程中芳基的开环反应机理及羟基相对位置对芳基开环反应的影响.

Catechol,hydroquinone and resorcinol were used as lignin model compounds,and pyrolyzed in a Curie point pyrolyzer.Products were detected by gas chromatograph(GC)and gas chromatograph/mass spectrum(GC/MS).Results showed that hydroquinone was pyrolyzed to form 1,4-benzoquinone which was decomposed to generate CO(1.6%,mass fraction,the following are the same as),C 2 hydrocarbon(2.7%)and C 4 hydrocarbon(2.8%)via ring-opening reactions.Catechol was pyrolyzed to form C 4 hydrocarbon(5.2%)and CO(3.1%)via ring-opening reactions at a lower temperature,and styrene was detected at 670℃indicating ring-opening reactions occurred.The yields of CO and CO 2 were 2.2%and 1.7%from resorcinol pyrolysis,and the yield of C 1 to C 5 hydrocarbon was similar between 1.1%to 2.2%.CO and CO2 were two main gases formed from the resorcinol pyrolysis,indicating that complex reactions occurred.Based on the products distribution of three benzenediols,the mechanism of aryl ring-opening reactions was analyzed with considering the effect of relative position of hydroxyl group.