5-羟甲基糠醛热解行为的理论研究

Theoretical Study on Pyrolysis Behavior of 5-HMF

采用密度泛函理论方法B3LYP/6-31G++(d,p)对5-羟甲基糠醛(5-HMF)的热解反应机理进行量子化学理论研究。研究结果表明:5-HMF可以脱去羟基侧链生成糠醛,反应能垒为322.8 kJ/mol;也可脱去醛基侧链生成2-糠醇,反应能垒为375.4 kJ/mol,说明在5-HMF的热解过程中糠醛的出现比2-糠醇要早。糠醛进一步热解可发生开环生成苯环,反应能垒为370.8 kJ/mol,说明呋喃环能够发生脱氧环化反应。5-HMF直接发生开环反应有水参与时生成链式烯醇类物质,无水参与时生成链式烯酮类物质,有/无水分子参与的反应能垒分别为287.6和279.1 kJ/mol,说明水分子的参与不利于5-HMF的开环。

The mechanism of 5-hydroxymethylfurfural(5-HMF)pyrolysis was studied by density functional theory B3LYP/6-31G++(d,p).The results show that the energy barrier of generating furfural by hydroxy side chain removal of 5-HMF is 322.8 kJ/mol,and the energy barrier of 2-furfuryl alcohol by aldehyde group side chain removal of 5-HMF is 375.4 kJ/mol.It is indicated that the appearance of furfuryl is earlier than 2-furfural in the pyrolysis process of 5-HMF.Further pyrolysis of furfural can occur the ring-opening reaction to form benzene ring with the reaction energy barrier of 370.8 kJ/mol,which explains that the furan ring can undergo deoxygenation and cyclization reaction.5-HMF can directly generate ring-opening reaction in the case of H 2 O participation or without H 2 O participation to obtain enol compounds or enone compounds.The energy barrier of ring-opening reaction with H 2 O participation is 287.6 kJ/mol,and the energy barrier of ring-opening reaction without H 2 O participation is 279.1 kJ/mol.Thus,the participation of water molecules is not conducive to the ring opening of 5-HMF.