Research teams at Tokyo University of Agriculture and Technology and Tokyo Metropolitan University have developed a new catalytic reaction that decomposes plastic (polyester) into the raw material monomer.
Polyester is used in a wide range of applications such as textiles, tableware, beverage bottles, home appliances and agricultural materials, and is one of the plastics that are consumed in large quantities worldwide.Since the decomposition is mainly a method requiring strong bases, additives, high temperature and multiple steps, a more efficient decomposition method is required.
The researchers have repeated the ester structure of polyester produced by the reaction of a monomer (dicarboxylic acid) with a carboxylic acid bonded at both ends and a monomer (diol) with alcohols at both ends. I paid attention to that.If the ester structure can be replaced with low molecular weight alcohols such as methanol one after another, the methyl ester and diol of carboxylic acid, which is the raw material of polyester, can be completely decomposed.
Therefore, we decided to search for a catalyst that can efficiently proceed with this decomposition reaction, and when we investigated under various conditions, we found that a complex of lanthanum, a rare earth element, was effective.Polybutylene succinate, which is widely used among polyesters, quantitatively contains dimethyl succinate, which is a raw material for polyester, in methanol at a catalyst concentration of only 1 mol%, a reaction temperature of 90 ° C, and a reaction time of 4 hours. It is said that it could be decomposed into butanediol.
Similarly, ethylene polyadipate, polybutylene terephthalate, and polyethylene terephthalate (PET), which is a material for PET bottles, were also successfully decomposed. Since there has been no conventional method for decomposing PET using only an inexpensive catalyst and solvent, it can be said to be a highly practical reaction.In fact, it is said that even commercially available PET bottles could be completely decomposed into monomers at a catalyst concentration of 1 mol%, a reaction temperature of 150 ° C., and a reaction time of 4 hours.
Since this reaction can use commercially available methanol as a solvent and has the great advantage of being able to react in the air, it is expected that research will progress toward social implementation that will lead to the solution of the waste plastic problem (plastic waste problem).
Paper information:[Chemical Communications] La (III)-Catalysed Degradation of Polyesters to Monomers via Transesterifications
