催化学报 ›› 2019, Vol. 40 ›› Issue (4): 534-542.DOI: 10.1016/S1872-2067(19)63319-X

• 论文 • 上一篇    下一篇

Al(CF3SO3)3催化选择性氧化甘油转化为甲酸

孔康, 李迪帆, 马文保, 周青青, 唐国平, 侯震山   

  1. 华东理工大学化学与分子工程学院, 工业催化研究所, 先进材料重点实验室, 上海 200237
  • 收稿日期:2018-11-10 修回日期:2019-01-25 出版日期:2019-04-18 发布日期:2019-03-14
  • 通讯作者: 侯震山
  • 基金资助:

    国家自然科学基金(21773061,21373082);上海市教委科研创新项目(15ZZ031).

Aluminum(III) triflate-catalyzed selective oxidation of glycerol to formic acid with hydrogen peroxide

Kang Kong, Difan Li, Wenbao Ma, Qingqing Zhou, Guoping Tang, Zhenshan Hou   

  1. Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2018-11-10 Revised:2019-01-25 Online:2019-04-18 Published:2019-03-14
  • Supported by:

    The authors are grateful for support from the National Natural Science Foundation of China (21773061, 21373082), and the Innovation Program of Shanghai Municipal Education Commission (15ZZ031).

摘要:

化石能源的日渐紧缺以及在使用过程中带来的环境污染引起了世界范围内学术界和工业界的密切关注,而生物柴油作为一种环境友好的可再生资源,可以替代化石能源,具有非常好的发展前景.虽然生物柴油生产过程中会产生大量甘油副产物,但是甘油也是一种重要的生物质平台分子,可用于生产多种高附加值的化学品.为了提高甘油的利用价值,同时探索一条高产率制备甲酸的可替代路径,本文研究了一个在较温和条件下,以三氟甲磺酸盐为催化剂,过氧化氢为氧化剂,将甘油选择性氧化为甲酸和乙醇酸的催化体系.结果表明,金属阳离子的催化活性与它们的水解常数(Kh)和内含水配体取代的交换速率常数(水交换速率常数,WERC)之间存在密切的相关性,适当的水解常数和较高的水交换速率常数有利于甘油氧化反应.在考察的多种金属三氟甲磺酸盐中,三氟甲磺酸铝(Ⅲ)是甘油选择性氧化为甲酸最有效的催化剂.在温度为70℃,反应12h的条件下,甲酸收率可达72%.另外,反应体系中甘油、催化剂和H2O2的比例对甘油氧化产物分布有一定影响.一系列实验研究表明,催化体系中产生的Lewis酸和Brønsted酸存在协同作用,具有适当Lewis酸和Brønsted酸比例的金属盐呈现出良好的催化性能,催化剂过度水解可降低其催化活性.Al(OTf)3原位水解过程中产生的Lewis酸性物种[Al(OH)x]n+和Brønsted酸物种CF3SO3H是催化甘油转化的活性中心,另外在H2O2存在下产生的Al过氧物种可能是甘油氧化的活性中心.反应动力学和1H NMR研究表明,在甘油转化为甲酸的过程中,甘油酸、乙醇酸和乙酸可能是反应的中间产物,可以继续氧化转化为甲酸.该催化剂体系同样适用于其他生物平台分子选择性氧化转化为有机羧酸,并且能够在甘油氧化反应中多次循环使用.Al(OTf)3作为简单易得的催化剂具有高效的催化性能和优异的循环使用性能,这将为甘油选择性氧化转化为高附加值产品开辟一种新的方法.

关键词: Al(OTf)3, 甘油, 过氧化氢, 选择性氧化, 甲酸

Abstract:

Glycerol is a by-product of biodiesel production and is an important readily available platform chemical. Valorization of glycerol into value-added chemicals has gained immense attention. Herein, we carried out the conversion of glycerol to formic acid and glycolic acid using H2O2 as an oxidant and metal (Ⅲ) triflate-based catalytic systems. Aluminum(Ⅲ) triflate was found to be the most efficient catalyst for the selective oxidation of glycerol to formic acid. A correlation between the catalytic activity of the metal cations and their hydrolysis constants (Kh) and water exchange rate constants was observed. At 70℃, a formic acid yield of up to 72% could be attained within 12 h. The catalyst could be recycled at least five times with a high conversion rate, and hence can also be used for the selective oxidation of other biomass platform molecules. Reaction kinetics and 1H NMR studies showed that the oxidation of glycerol (to formic acid) involved glycerol hydrolysis pathways with glyceric acid and glycolic acid as the main intermediate products. Both the[Al(OH)x]n+ Lewis acid species and CF3SO3H Brønsted acid, which were generated by the in-situ hydrolysis of Al(OTf)3, were responsible for glycerol conversion. The easy availability, high efficiency, and good recyclability of Al(OTf)3 render it suitable for the selective oxidation of glycerol to high value-added products.

Key words: Aluminum(III) triflate, Glycerol, Hydrogen peroxide, Selective oxidation, Formic acid