Kim Minjune, Su Yaqiong, Fukuoka Atsushi, Hensen Emiel J M, Nakajima Kiyotaka
Institute for Catalysis, Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo 0010021, Japan.
Inorganic Materials Chemistry, Schuit Institute of Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600, MB, Eindhoven, The Netherlands.
Angew Chem Int Ed Engl. 2018 Jul 2;57(27):8235-8239. doi: 10.1002/anie.201805457. Epub 2018 Jun 1.
The utilization of 5-(hydroxymethyl)furfural (HMF) for the large-scale production of essential chemicals has been largely limited by the formation of solid humin as a byproduct, which prevents the operation of stepwise batch-type and continuous flow-type processes. The reaction of HMF with 1,3-propanediol produces an HMF acetal derivative that exhibits excellent thermal stability. Aerobic oxidation of the HMF acetal with a CeO -supported Au catalyst and Na CO in water gives a 90-95 % yield of furan 2,5-dicarboxylic acid, an increasingly important commodity chemical for the biorenewables industry, from concentrated solutions (10-20 wt %) without humin formation. The six-membered acetal ring suppresses thermal decomposition and self-polymerization of HMF in concentrated solutions. Kinetic studies supported by DFT calculations identify two crucial steps in the reaction mechanism, that is, the partial hydrolysis of the acetal into 5-formyl-2-furan carboxylic acid involving OH and Lewis acid sites on CeO , and subsequent oxidative dehydrogenation of the in situ generated hemiacetal involving Au nanoparticles. These results represent a significant advance over the current state of the art, overcoming an inherent limitation of the oxidation of HMF to an important monomer for biopolymer production.
5-(羟甲基)糠醛（HMF）用于大规模生产重要化学品的应用在很大程度上受到副产物固体腐殖质形成的限制，这阻碍了分步间歇式和连续流工艺的运行。HMF与1,3-丙二醇的反应生成一种具有优异热稳定性的HMF缩醛衍生物。在水中，用CeO负载的Au催化剂和Na₂CO₃对HMF缩醛进行有氧氧化，从浓溶液（10 - 20 wt%）中可得到90 - 95%产率的呋喃-2,5-二甲酸，这是生物可再生能源行业中一种日益重要的商品化学品，且不会形成腐殖质。六元缩醛环抑制了浓溶液中HMF的热分解和自聚合。由密度泛函理论（DFT）计算支持的动力学研究确定了反应机理中的两个关键步骤，即缩醛部分水解为5-甲酰基-2-呋喃羧酸，涉及CeO上的OH和路易斯酸位点，以及随后原位生成的半缩醛的氧化脱氢，涉及Au纳米颗粒。这些结果代表了相对于当前技术水平的重大进步，克服了将HMF氧化为生物聚合物生产重要单体的一个固有限制。
