山梨醇快速热解特性与反应机理研究

Reaction characteristics and mechanisms of sorbitol fast pyrolysis

本研究结合快速热解实验和密度泛函理论(DFT)计算,深入探究了山梨醇快速热解主要产物的生成机理与竞争关系。结果表明,山梨醇快速热解产物主要包括:小分子产物羟基乙醛(HAA)、羟基丙酮(HA)等,呋喃类产物糠醛(FF)、1-(2-呋喃基)-乙酮(2-FE)等和脱水糖产物异山梨醇(IS)。小分子产物HA和HAA生成路径的反应能垒较低,因此,产率最高,且HA生成过程中伴随着HAA的生成。呋喃类产物2-FE和FF生成能垒相对较高,其能量最优路径与小分子产物生成路径具有相同中间体,但竞争性较弱,因而产率低于小分子产物。脱水糖产物IS生成路径较为简单,不与其他产物共享相同中间体,但反应能垒很高,导致产率很低。本研究为山梨醇选择性热解的机理研究和技术开发奠定了一定的理论基础。

In the present study,the fast pyrolysis characteristics of sorbitol were deeply explored and the formation mechanism of the main products was revealed using fast pyrolysis experiments and density functional theory(DFT)calculations.The results show that the fast pyrolysis of sorbitol mainly produces low molecular weight products such as hydroxyacetaldehyde(HAA)and hydroxyacetone(HA),furan-based products such as furfural(FF)and 1-(2-furanyl)-ethanone(2-FE),and anhydrosugar product(isosorbitol(IS)).The yield of HA and HAA products is the highest,due to their lower overall energy barriers.Notably,the generation of HA and HAA are simultaneous.The formation of furan-based products 2-FE and FF needs to overcome relatively higher overall energy barriers,despite that some intermediates also appear in the formation of HA and HAA.Hence,the yields of furan-based products are lower than those of low molecular weight products.The reaction intermediates for formation of anhydrosugar IS are different from those of HA/HAA and 2-FE/FF.The overall energy barrier is high that leads to a very low yield of IS.This study provides a theoretical insight into the mechanism research and technique development for selective pyrolysis of sorbitol.