Recycling fluoropolymers to acyl fluorides through shuttle catalysis

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Fluoropolymers are widely used but challenging to recycle.
• Efficient methods for recovering fluorine content from waste fluoropolymers are needed.
• Existing recycling methods often lack scalability or generate undesirable byproducts.

Purpose of the Study:

• To develop a catalytic chemical recycling process for fluoropolymers.
• To investigate the conversion of fluoropolymers into valuable acyl fluorides.
• To explore the potential for creating new fluorinated materials from recycled content.

Main Methods:

• Utilized a catalytic system of BF3·OEt2 and BF3·PCy3 for defluorination.
• Optimized reaction conditions using fluoroethane (HFC-161) as a model substrate.
• Applied the methodology to various pristine and post-consumer fluoropolymers, including PVDF from Li-ion batteries.
• Conducted mechanistic studies using spectroscopy and DFT calculations.
• Analyzed recycled materials using powder XRD, XPS, IR spectroscopy, DSC, and TGA.

Main Results:

• Successfully converted fluoropolymers into acyl fluorides by harvesting HF equivalents.
• Demonstrated scalability with a range of acid anhydrides, including acetic anhydride.
• Observed a decrease in PVDF crystallinity and loss of the α-phase upon defluorination.
• Introduced new unsaturated C=C and oxygen-containing functional groups, lowering thermal decomposition temperature.
• Showcased the recycling of PVDF from post-consumer Li-ion batteries.

Conclusions:

• The developed catalytic method offers an effective route for chemical recycling of fluoropolymers.
• This approach facilitates the recovery of fluorine content and the synthesis of acyl fluorides.
• The process allows for the creation of modified fluorinated materials with altered properties.
• The methodology holds promise for sustainable management of fluoropolymer waste.