Mechanochemical methanolysis of polyethylene terephthalate using calcium oxide as solid base catalyst: a case study

Area of Science:

• Materials Science
• Chemical Engineering
• Sustainable Chemistry

Background:

• Polyethylene terephthalate (PET) is a widely used plastic facing recycling challenges.
• Conventional PET recycling often involves high temperatures, which can be energy-intensive.
• Developing alternative, lower-energy depolymerization methods is crucial for sustainable plastic management.

Purpose of the Study:

• To investigate the feasibility of producing dimethyl terephthalate (DMT) from PET using planetary ball milling.
• To determine the optimal reaction parameters for this mechanochemical depolymerization process.
• To compare the findings with conventional thermochemical methods.

Main Methods:

• Utilizing planetary ball milling for the mechanochemical depolymerization of PET.
• Employing calcium oxide (CaO) as a catalyst.
• Conducting the reaction at ambient temperature.
• Analyzing the yield and purity of the obtained dimethyl terephthalate.

Main Results:

• Achieved a high yield of 83% for dimethyl terephthalate (DMT).
• Identified optimal catalyst loading and milling parameters.
• Demonstrated that optimal conditions differ significantly from heat-driven processes.
• The process was studied as a case study, with findings not generalized for broader conditions.

Conclusions:

• Planetary ball milling with CaO offers an effective route for PET depolymerization at ambient temperature.
• Mechanochemical conditions for optimal DMT yield vary from those in thermal methods.
• This approach presents a potential low-temperature alternative for PET chemical recycling.