Chemical methods and biological enzymes, who is the latecomer?- Jiaxing Fuda Chemical Fibre Factory

Driven by the world's "double carbon" goal and brand owners' recycling traceability policies, the chemical recycling of recycled polyester (PET) is moving from the laboratory to the center of the industrial stage. Different from physical recycling that only changes the physical form, chemical methods can remove impurities and "restore native-level performance" through the path of depolymerization-purification-repolymerization, truly realizing the closed-loop cycle of "textile to textile" and "bottle to bottle". At present, the world's chemically recycled PET has entered a critical stage of large-scale implementation, dominance by giants, and differentiation of technical routes. Among the many chemical depolymerization routes, the DMT method (dimethyl terephthalate route) and the BHET method (bishydroxyethyl terephthalate route) are two relatively mainstream technical directions. Both have their own characteristics in terms of process logic, product form, economy and adaptability, and are outlining the technical landscape of the recycled polyester industry.

The comparison between recycled polyester DMT and BHET processes is as follows:

Comparison of process parameters of recycled polyester DMT and BHET
Comparative item	BHET (ethylene glycol hydrolysis)	DMT (BHET transesterification method)
Number of reaction stages	1 stage depolymerization	Stage 2: Alcoholysis and transesterification
core solvent	Ethylene glycol (single solvent)	Ethylene glycol methanol dual solvent
Can it be directly aggregated?	High-purity BHET goes directly into the polymerization kettle	It must be transesterified to form BHET before it can be polymerized.
Impurity treatment	Crystal impurity removal, medium dye retention capacity	Multi-tower distillation and recrystallization, strong color and impurity removal capabilities, suitable for heavily polluted waste textiles
Equipment investment	Low investment in single unit, no methanol distillation tower	Equipped with methanol distillation and DMT precision distillation, high equipment investment

It can be seen that BHET 比 DMT There is one less transesterification process, so the process is shorter, the cost and energy consumption are lower, and the entry barrier is also lowered. Therefore, new projects in future chemical methods There are many BHET methods.

At present, there are also regenerated chemical fiber factories that purchase chemically regenerated chips, with prices ranging from 11,000 to 15,600, to make differentiated functional fibers. However, some customers have reported that the results are not as good as expected. The quality of 15000-15600 is slightly better and the color is whiter, but the quality of other products is generally poor. At the same time, the price of CCF index 3A white slices is 6,650 yuan/ton, the price of recycled slices is 7,800 yuan/ton, and the price of raw semi-gloss slices is around 7,200 yuan/ton. A comparison shows that the actual price comparison is full. If there is no T2T concept, the current willingness to pay is low. However, with the upgrading of technology, the cost of chemical methods is gradually decreasing.

The biological enzymatic method uses degrading enzymes as depolymerization catalysts to depolymerize PET into PTA and MEG monomers under mild conditions (normal temperature and pressure or medium temperature) , currently in the pilot stage, is also a regeneration development direction that the market is paying great attention to.

A summary and comparison of the three paths are as follows:

Current benchmarking dimensions	Bioenzymatic method	BHET chemical method	DMT chemical method
reaction conditions	Normal temperature and pressure, no high temperature and high pressure	Medium temperature and normal pressure	Multi-stage temperature control, high energy consumption
product	rPTA EG	BHET	DMTEG
Processing costs	On the high side (intermediate experimental stage)	medium	高
Energy consumption	低	medium	高
Raw material adaptation	Able to handle complex waste materials that are difficult to handle with traditional chemical methods without the need to remove impurities such as dyes and additives in advance	It can handle various forms of waste PET such as cloth, film, bottles, etc., and has requirements for raw material cleanliness.	It has strong depolymerization and purification capabilities for raw materials with high impurity content such as blended fibers, colored PET, dye-containing textile waste, etc.
Scale maturity	Transition from pilot testing to mass production (2026-2028)	Complete commercialization and peak production expansion	Mature but investment is high, expansion of production is cautious

To sum up, in the short term, Relying on the advantages of low cost and integration, BHET has become the mainstream of chemical regeneration and production expansion, while DMT has maintained its differentiated market by relying on miscellaneous material adaptation and export premium. , the two chemical routes jointly divide the domestic chemical reproduction capacity. Biological enzymes are limited by the cost of enzyme preparations and are in the intermediate experimental stage, rapidly penetrating into the segmented waste textile field. In the long term, with continuous technological breakthroughs and two-way cost reductions through chemical and biological enzymatic methods, the cost of recycling recycled polyester will be reconstructed and the industry will shift from more physical recycling to chemical closed-loop regeneration.