物理化学学报2022，Vol.38Issue(10)：57-64,8.DOI:10.3866/PKU.WHXB202205027
Lewis酸催化纤维素制乳酸机理研究
Reaction Mechanism of Cellulose Conversion to Lactic Acid with Lewis Acid Catalysts
摘要
Abstract
Because fossil fuels are continuously depleted,valorization of biomass into valuable liquid products and chemicals is of great significance yet it remains challenging.Among many biomass-derived products,lactic acid is one of the most important renewable monomers for preparing the degradable polymer polylactic acid.The use of raw biomass to produce lactic acid through catalytic conversion is an attractive approach.In this work,the catalytic reaction performance and mechanism of different Lewis acids(Y3+,Sc3+,and Al3+)for the production of lactic acid from cellulose were investigated in detail by isotopic nuclear magnetic resonance(NMR)and mass spectrometry.The production of lactic acid from cellulose includes tandem and competing reactions.The order of catalytic activity for the one-pot conversion of cellulose into lactic acid is as follows:Y3+＞Al3+＞Sc3+.The main tandem reactions involve the hydrolysis of cellulose into glucose,the isomerization of glucose into fructose(the order of catalytic activity,the same below:Y3+＞Al3+,Y3+＞Sc3+),the cleavage of fructose via a retro-aldol reaction to glyceraldehyde(GLY)and 1,3-dihydroxyacetone(DHA)(Sc3+＞Y3+＞Al3+),and the conversion of DHA or GLY to the final product lactic acid(Al3+＞Y3+＞Sc3+).It was found that the process of glucose isomerization to fructose was the key step to the final selectivity of the tandem reaction of cellulose conversion to lactic acid,and it was clarified that the production of lactic acid from DHA underwent a keto-enol(K-E)tautomerization process rather than a classical 1,2-shift process.First,DHA was transformed into GLY via the isomerization process,then the adjacent hydroxyl group of GLY was removed in the form of water to produce an α,β-unsaturated species.After that,the α,β-unsaturated species underwent K-E tautomerization to generate unsaturated aldehyde-ketone intermediates.Meanwhile,a molecule of water was added to aldehyde-ketone intermediates to obtain a diol product,the hydrogen atom at the methine position was transferred and the lactic acid was finally obtained through the K-E tautomerization process.The in-depth understanding of the reaction mechanism presented in this work will help to design more selective catalysts for cellulose conversion into value-added oxygen-containing small molecule chemicals.关键词
纤维素/葡萄糖/果糖/乳酸/Lewis酸/烯醇互变Key words
Cellulose/Glucose/Fructose/Lactic acid/Lewis acid/Keto-enol tautomerization分类
化学化工引用本文复制引用
郝睿,关伟翔,刘菲,张磊磊,王爱琴..Lewis酸催化纤维素制乳酸机理研究[J].物理化学学报,2022,38(10):57-64,8.基金项目
The project was supported by the National Key R&D Program of China(2018YFB1501602),National Natural Science Foundation of China(22132006),and the China Postdoctoral Science Foundation(2021M690149).国家重点研发计划(2018YFB1501602),国家自然科学基金(22132006),中国博士后科学基金(2021M690149)资助 （2018YFB1501602）
