Page 8 - 《橡塑技术与装备》英文版2025年12月

HINA RUBBER/PLASTIC TECHNOLOGY AND EQUIPMENT

2 Experimental section 3.1 Effect of reaction time on yield
2.1 Catalyst Preparation Under the conditions of a mass ratio of 4:1:0.04 of
Catalyst preparation: Silicates and diols are reacted in ethylene glycol: PET: catalyst and a reaction temperature
organic solvents, and the reaction products are separated of 200 ℃, PET bottle fragments of the same specification
from the solvent, filtered, washed, dried, and ground to and particle size were mixed at the same stirring rate
obtain silanol catalysts. with different reaction times. The calculated reaction
2.2 Experimental Methods yield results are shown in Figure 2. It was verified that
After cleaning, drying, and crushing the waste plastic PET depolymerization time is short, the reaction is not
packaging bottles, they are placed inside the bottles and sufficient, and the chain breakage is not sufficient. More
stirred with ethylene glycol. When the temperature inside un depolymerized PET residue is filtered out, resulting in a
the bottles reaches about 100 ℃, a catalyst is added to low BHET yield.With the extension of reaction time, it can
the bottles. After the catalyst is evenly dispersed, dry be observed that most of the PET is depolymerized, but
nitrogen is used to replace the air in the bottles and raise the chromaticity of the reaction system gradually deepens
the temperature to 200 ℃.Boiling ethylene glycol is with the extension of reaction time, and the yield of BHET
refluxed back into the bottle until the reaction is complete. does not increase significantly with the extension of time,
The heating is turned off, and the reaction material is tending to remain unchanged. However, it also brings an
kept stirred and refluxed. When the room temperature increase in reaction energy consumption. Therefore, the
cools to around 100 ℃, the stirring and reflux are turned optimal reaction time is controlled at 200 ℃.
off.Quickly filter the material into distilled water at
approximately 90 ℃, wash the flask with hot water, and
combine the washing water with the filtered liquid.The
needle shaped BHET is prepared by cooling the filtered
solution at 0-5 ℃ for 15 hours, followed by crystallization,
filtration, cleaning, and drying
2.3 Reaction principle
The principle of ethylene glycol decomposition is
the solvent decomposition of PET, where the ester bonds
of polyester chains are replaced by hydroxyl groups of
ethylene glycol under certain temperature and catalyst
Figure 2 Yield of PHET at different reaction times
conditions.The main dissociation reaction equation of this
method is shown in Figure 1. 3.2 Effect of reaction temperature on yield
O O Under the conditions of a mass ratio of 4:1:0.04 of
C C O CH 2 CH 2 O + HO OH ethylene glycol: PET: catalyst and a reaction temperature
n
PET ethyleneglycol of 200 ℃, PET bottle fragments of the same specification
O O and particle size were mixed at the same stirring rate for
HO H 2 C H 2 C O C C O CH 2 CH 2 OH different reaction times. The calculated reaction yield
results are shown in Figure 3. It was verified that PET
BHET
Figure 1 Structural formula of ethylene glycol depolymerization was not sufficient at low reaction
alcoholysis PET reaction temperatures, and unreacted PET residue was filtered
out, resulting in a decrease in yield.By increasing the
3 Results and Discussion reaction temperature, it can be observed that the reflux
flow of ethylene glycol in the reaction bottle gradually

·2· Vol.51，No.12