Chemical recycling of hydrofluorocarbons by transfer fluorination

Key findings from this study

• The study found that treatment of hydrofluorocarbons with potassium bases generates anhydrous potassium fluoride suitable for transfer fluorination reactions.
• The researchers demonstrate that recycled fluoride sources enable one-pot synthesis of sulfonyl fluorides, aryl fluorides, alkyl fluorides, and p-block fluorides.
• The authors report that industrial fluorochemicals including refrigerants, anesthetics, and battery additives undergo successful chemical recycling by this mechanism.
• The study established technical feasibility at multiple production scales through batch (50 g) and continuous flow (1.5 g h-1) demonstration.

Overview

The study presents a chemical recycling approach for fluorochemicals through transfer fluorination. Treatment of hydrofluorocarbons with potassium bases (KHMDS or KOtBu) rapidly generates anhydrous potassium fluoride. This fluoride source subsequently participates in one-pot syntheses to generate diverse fluorinated molecules.

Methods and approach

Hydrofluorocarbons undergo defluorination when exposed to potassium bases under controlled conditions. The resulting potassium fluoride then transfers to various substrates in unified synthetic sequences. Mechanistic aspects received investigation via density functional theory calculations. Scalability was evaluated using batch chemistry (50 g scale) and continuous flow methods (1.5 g h-1).

Results

The transfer fluorination process converts industrially relevant fluorochemicals into usable fluoride sources while enabling synthesis of downstream products. Recycled substrates encompass hydrofluorocarbons, hydrofluoroolefins, fluoroethers (including anesthetics and battery electrolyte additives), perfluoroctanoic acid, and poly(vinylidene) difluoride. The resulting potassium fluoride constructs sulfonyl fluorides, aryl fluorides, alkyl fluorides, and p-block element fluorides in single synthetic operations.

Density functional theory calculations clarified key aspects of the fluorine transfer mechanism. Both batch and flow-based approaches demonstrated technical feasibility at increased scales. The flow chemistry variant maintained a throughput of 1.5 g h-1, suggesting capacity for larger-scale implementation.

Implications

This recycling strategy addresses environmental and health concerns associated with fluorochemical production. Conversion of waste fluorochemical stocks into fluorinating reagents eliminates separate synthesis pathways and reduces material losses. The approach particularly benefits sectors reliant on refrigerants and specialized fluorinated compounds where material recovery economics favor closed-loop processes.

Scalable protocols enable transition from laboratory demonstrations to industrial application. Flow-based production offers advantages for continuous manufacturing environments. Broadened availability of fluoride sources through recycling pathways may reduce dependency on energy-intensive industrial fluorine chemistry production.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.