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Green catalysts with Earth-abundant metals accelerate production of biobased plastic

 Tokyo Institute of Technology and Japan Science and Technology Agency (JST) announced on 7 January, 2019 that the scientists at the Institute have developed and analyzed a novel green catalyst to produce biobased plastic. The research team was led by Prof. Michikazu Hara and succeeded in synthesizing 2,5-Furandicarboxylic acid (FDCA) from biobased 5-hydroxymethyl furfural (HMF) by using optimized manganese dioxide (MnO2) catalyst. The results were published in Journal of the American Chemical Society*.

 Currently used plastics are mostly made from non-renewable fossil resources and the alternative renewable natural resources are desired to replace them. Polyethylene furanoate (PEF) is synthesized from FDCA, and has the possibility to replace non-renewable and widely used polyethylene terephthalate (PET), because of the similarity in their properties. FDCA is made through the oxidation of biobased HMF via 5-formyl-2-furancarboxylic acid (FFCA) as an intermediate product, however, the use of catalyst containing precious metals has been required.

 The research team found that a certain type of MnO2 nano-crystal can effectively catalyze the oxidation reaction of HMF to produce FDCA without the precious metals. Since several types of crystal structure have been known in MnO2, computational analyses and theoretical considerations on the oxidation reaction are carried out for various MnO2 crystal structures. Because, in the oxidation process, oxygen atoms are transferred from MnO2 to the reaction products (i.e.: FFCA and FDCA), oxygen vacancy formation in MnO2 was found to be crucial and the higher catalytic activity of MnO2 can be achieved by crystal structure with lower vacancy formation energy. Consequently, β-MnO2 was selected and synthesized as nano-particles by the original crystallization method devised by the team. Oxidation of HMF in water solution under the presence of β-MnO2 catalyst showed the yield of FDCA improved from 28% to 86% compared to the conventional MnO2 catalyst, while the yield of FFCA decreased from 58% to 1%.

* Eri Hayashi, Yui Yamaguchi, Keigo Kamata, Naoki Tsunoda, Yu Kumagai, Fumiyasu Oba, and Michikazu Hara, "Effect of MnO2 Crystal Structure on Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid", Journal of the American Chemical Society, Article ASAP, DOI: 10.1021/jacs.8b09917; Publication Date (Web): January 7, 2019