從廢棄寶特瓶發展PET跟新一代PEF的化學回收製程及循環經濟(2/3)

A circular economy is based on the principles of designingout waste and pollution, keeping materials and products inuse, and regenerating natural systems. In contrast to the"take-make-waste" linear model, a circular economy isrestorative and regenerative by design, not just recycling.Along with the search for solutions that can be scaled upfor a circular economy of plastics, it has been recognizedthat addressing the symptoms of plastic pollution throughclean-ups is not enough. Therefore, we need to move away from today's linear takemake-waste model, and to reuse plastics towards a circulareconomy for plastics, in which it never becomes waste orpollution.However, much of the plastic packaging is downcycled.Instead of making a new plastic package from an old one,the plastics are physically reprocessed into products oflesser quality or value which are not further recyclable.In Taiwan's polyester industry, several manufacturers havedeveloped techniques for PET recycling mainly based on aphysical method. Nevertheless, its recycling for other PETproducts with many ingredients and/or impurities cannot beachieved only by physical means alone. Chemical recyclingfits in with the principles of sustainable development,because it leads to the formation of raw materials (i.e.monomers) for reuse, and abates the impact of wastes on theenvironment. Obviously, a gap in PET recycling existsbetween Taiwan and the world. There is an urgent need ofdeveloping the methods of PET's chemical recycling forTaiwan's recycling industry, and a circular economy of PET.On the other hand, it is quite common to overlook theprocessing properties of recycled products.The aim of this proposal is three-fold:(1) to develop both glycolysis and alkaline hydrolysismethods for PET recycling, and to comprehensively comparethe two methods in more details for future processdevelopment,(2) to study on how to engineer product properties of TPAand BHET, after alkaline hydrolysis and glycolysis,respectively, for downstream operations, and(3) to develop methods for chemical recycling of PEF as apreventive measure for a circular economy of nextgeneration plastic bottles.For the 1st year, PET has been successfully depolymerizedby alkaline hydrolysis and glycolysis into TPA and BHET asmonomers, respectively. The obtained monomer products werefully characterized and subjected to solvent screening andsolubility determination. Given different operatingconditions and solvent uses, TPA crystals could be enlargedsignificantly to avoid undesired crystal attributes andpoor processability.For the 2nd year, alkaline hydrolysis of PET and thefollowing recovery of TPA, and glycolysis of PET and thefollowing separation and purification operations of BHEThave comprehensively been investigated. Their filtrationand drying characteristics have also been determined andcompared while good processability is important for thedevelopment of plastic recycling processes.