No abstract

BACKGROUND Chemical recycling of waste poly(ethylene terephthalate) (PET) is an effective way to save energy and protect the environment. In this work, calcined sodium silicate was adopted as a novel solid base catalyst for methanolysis of PET for the first time. The effects of various parameters on the conversion of PET and the yield of dimethyl terephthalate (DMT) in the methanolysis process of PET were investigated. RESULTS The results showed that the conversion of PET could reach about 100% and the yield of DMT could reach about 95% under the following conditions: calcined sodium silicate, 5 wt%; molar ratio of methanol to PET, 5:1; reaction time, 30 min; reaction temperature, 200 °C. The higher the mass ratio of methanol to PET and the higher the temperature, the higher were the conversion of PET and the yield of DMT. In addition, the catalyst can be reused more than five times and has good catalytic activity. CONCLUSIONS Calcined sodium silicate has the advantages of low cost, simple fabrication method, high catalytic activity and environmental friendliness. The use of this solid base catalyst is a promising strategy for realizing the recycling of waste polyester. © 2022 Society of Chemical Industry (SCI).

Dimethyl carbonate (DMC) was synthesized from methanol and ethylene carbonate (EC) in a reactive distillation column by transesterification using different composite oxide catalysts. The catalysts were characterized by XRD, N2 adsorption‐ desorption, CO2‐TPD, and NH3‐TPD. The results show that the Zr−Al catalyst has the most strong base sites and weak acid sites compared with other catalysts. The synergistic effect of acid‐base sites makes it show excellent catalytic performance for DMC synthesis. The operation parameters including reflux ratio, feed molar ratio, liquid hourly space velocity (LHSV) and catalyst dosage were optimized by factorial design based on response surface methodology (RSM). The best optimization conditions was: reflux ratio=5.23 : 1, feed molar ratio=6.05 : 1, LHSV=0.48 h−1, catalyst dosage=119.04 ml, the relative error between measured value and predicted value is small, which indicated that the reliability of the optimized process is high.

The title compound has been synthesized and its crystal structure determined by X‐ray crystallographic method. The crystal is monoclinic, space group C2/c, with unit cell dimensions a=19.260 (3), b=11.217 (1), c=15.997 (1) Å; β=92.08 (2)° and Z=8. This is the first crystal structure determined in the series of bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one derivatives. The structure and the conformation of the cis‐cyclododecene moiety in this compound is demonstrated to be closely similar to the lowest energy conformer [lene 2333].

BACKGROUND: Whether waste polyethylene terephthalate (PET) can be effectively recycled is one of the main challenges of the current environmental problems. The hydrolysis of dimethyl terephthalate (DMT) to terephthalic acid (TPA) over Nb-modified HZSM-5 zeolite was studied. Nb/HZSM-5 zeolites with different loadings were prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, NH 3 -temperature programmed desorption and pyridine adsorption infrared spectroscopy. The effects of different reaction conditions on the conversion of DMT and TPA yield were investigated.RESULTS: The yield of TPA strongly depends on the reaction conditions and the loading of Nb. The niobium phase exists in the form of Nb 2 O 5 on the zeolite and interacts with the surface of HZSM-5 to produce the active site of Brønsted acid. The yield of TPA is closely related to the concentration of Brønsted acid sites. On 0.6Nb/HZSM-5 catalyst, the yield of TPA is highest, at about 94%.CONCLUSION: Nb/HZSM-5 catalyst has excellent catalytic activity and high stability for DMT hydrolysis. In addition, the product TPA prepared in this study can be directly applied to the current PET production supply chain, providing a promising catalytic route.