摘要
为了解木质素的热解机理,利用密度泛函理论B3LYP方法,在6-31++G(d,p)基组水平上对含有C_α位羰基的β-O-4型木质素二聚体模型化合物(3-羟基-1-(4-羟基苯基)-2-苯氧基-1-丙酮)的热解过程进行了理论计算和分析。结果表明,C_α位上的羰基取代基可大大降低C_β—O的键解离能,提高C_α—C_β的键解离能,使得C_β—O的键解离能比C_α—C_β低91.5 k J/mol,因此该二聚体主要通过C_β—O键均裂的方式发生热解反应,其主要酚类热解产物是苯酚和4-羟基苯甲醛,次要产物是4-羟基苯乙酮,生成4-羟基苯甲醛的动力学最优路径是R7-a,其反应能垒为236.6 k J/mol。
In order to understand the pyrolysis mechanism of lignin,3-hydroxy-1-（ 4-hydroxyphenyl）-2-phenoxypropan-1-one with C_αcarbonyl group was selected as a β-O-4 type lignin model dimer,and its pyrolysis process was theoretically calculated by density functional theory methods at B3 LYP level with 6-31 ＋ ＋ G（ d,p） basis set. The calculation results indicated that the carbonyl substituent on the C_αdramatically could significantly decrease the bond dissociation energy（ EBD） of C_β—O,while the bond dissociation energy of C_α—C_βwas augmented. The bond dissociation energy of C_β—O was 91. 5 k J/mol lower than that of C_α—C_β. Thus,it could be deduced that the dimer was mainly decomposed through the homolytic cleavage of the C_β—O linkage,and major phenolic pyrolytic products of phenol and 4-hydroxybenzaldehyde,minor parts of 4-hydroxyacetophenone were formed in this process. The R7-a kinetic way was considered as the optimum way to form 4-hydroxybenzaldehyde,and the energy barrier was236. 6 k J / mol.
出处
《林产化学与工业》
EI
CAS
CSCD
北大核心
2016年第1期20-26,共7页
Chemistry and Industry of Forest Products
基金
国家火炬计划项目(2013GH561645)
国家自然科学基金资助项目(51276062)
