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Aerobic Oxidation of 5‐(Hydroxymethyl)furfural Cyclic Acetal Enables Selective Furan‐2,5‐dicarboxylic Acid Formation with CeO 2 ‐Supported Gold Catalyst
Author(s) -
Kim Minjune,
Su Yaqiong,
Fukuoka Atsushi,
Hensen Emiel J. M.,
Nakajima Kiyotaka
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201805457
Subject(s) - acetal , furfural , chemistry , furan , furfuryl alcohol , catalysis , organic chemistry , humin , dicarboxylic acid , cationic polymerization , hydroxymethyl , fertilizer , humic acid
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 2 ‐supported Au catalyst and Na 2 CO 3 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 2 , 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.