基于EPR检测技术的木质素模型化合物催化热解反应机理

Catalytic Pyrolysis Reaction Mechanism of Lignin Model Compounds Based on EPR Detection Technology

针对生物质三大组分中最难分解的木质素,选取了愈创木酚及香兰素作为其模化物,为明晰其催化热解机理以实现对催化热解定向调控进行指导,采用电子顺磁共振(EPR)检测技术,结合Py-GC/MS的分析,研究了愈创木酚及香兰素催化热解的反应机理及反应路径.结果表明:以HZSM-5为催化剂,催化剂与反应物质量比为2∶1时,催化热解对于反应物的热解效果均优于非催化热解,愈创木酚催化热解主要液相产物有呋喃类、酚类、单环芳烃和多环芳烃.对于香兰素的催化热解产物主要为芳烃类、酚类和醛类.在催化热解过程中通过EPR技术可检测到甲基自由基的存在.依据自由基反应,分别梳理了愈创木酚及香兰素的催化热解机理及反应路径.

For the lignin which is the most difficult to decompose among the three major components of biomass,guaiacol and vanillin were selected as their model compounds.In order to clarify their catalytic pyrolysis mechanism and further guide the catalytic regulation of catalytic pyrolysis,electronic paramagnetic resonance(EPR)detection combined with Py-GC/MS analysis was used to study the catalytic pyrolysis reaction mechanism and reaction path of guaiacol and vanillin.Results show that when HZSM-5 is used as the catalyst and the mass ratio of catalyst to reactant is 2∶1,catalytic pyrolysis has better pyrolysis effect on the reactants than noncatalytic pyrolysis.The main liquid-phase products of guaiacol catalytic pyrolysis are furans,phenols,monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons.The catalytic pyrolysis products of vanillin are mainly aromatic hydrocarbons,phenols and aldehydes.The presence of methyl radicals can be detected by EPR during the catalytic pyrolysis process.Based on the free radical reaction,the catalytic pyrolysis mechanism and reaction path of guaiacol and vanillin are sorted out,respectively.