物理化学学报 >> 2022, Vol. 38 >> Issue (10): 2205027.doi: 10.3866/PKU.WHXB202205027

所属专题: 生物质催化转化

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Lewis酸催化纤维素制乳酸机理研究

郝睿1, 关伟翔1,*(), 刘菲1, 张磊磊1, 王爱琴1,2,*()   

  1. 1 中国科学院大连化学物理研究所, 中国科学院航天催化与新材料重点实验室, 辽宁 大连 116023
    2 中国科学院大连化学物理研究所催化基础国家重点实验室, 辽宁 大连 116023
  • 收稿日期:2022-05-12 录用日期:2022-06-01 发布日期:2022-06-06
  • 通讯作者: 关伟翔,王爱琴 E-mail:wxguan@dicp.ac.cn;aqwang@dicp.ac.cn
  • 基金资助:
    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)

Reaction Mechanism of Cellulose Conversion to Lactic Acid with Lewis Acid Catalysts

Rui Hao1, Weixiang Guan1,*(), Fei Liu1, Leilei Zhang1, Aiqin Wang1,2,*()   

  1. 1 CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning Province, China
    2 State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning Province, China
  • Received:2022-05-12 Accepted:2022-06-01 Published:2022-06-06
  • Contact: Weixiang Guan,Aiqin Wang E-mail:wxguan@dicp.ac.cn;aqwang@dicp.ac.cn
  • About author:Aiqin Wang, E-mail: aqwang@dicp.ac.cn. Tel.: +86-411-84379348
    Weixiang Guan, E-mail: wxguan@dicp.ac.cn
  • Supported by:
    the National Key R&D Program of China(2018YFB1501602);National Natural Science Foundation of China(22132006);the China Postdoctoral Science Foundation(2021M690149)

摘要:

乳酸是制备可降解聚合物聚乳酸的主要单体。利用秸秆等原生生物质为原料经过化学催化转化制备乳酸对于碳减排具有重要意义。本工作利用同位素核磁和质谱详细探究了不同Lewis酸(Y3+,Sc3+,Al3+)催化纤维素制乳酸的反应选择性和机理。发现葡萄糖异构化为果糖的过程是决定纤维素制乳酸多步串联反应最终选择性的关键步骤,并明确了1, 3-二羟基丙酮生成乳酸经历了烯醇互变异构过程而非经典的1, 2-shift机理。

关键词: 纤维素, 葡萄糖, 果糖, 乳酸, Lewis酸, 烯醇互变

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.

Key words: Cellulose, Glucose, Fructose, Lactic acid, Lewis acid, Keto-enol tautomerization

MSC2000: 

  • O643