Electrochemical Dehalogenation of Waste PVC for Halogenated Product Synthesis

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Solution Overview

Problem

Current recycling methods for PVC are inefficient due to the challenges of separating PVC from other plastics, the hazardous nature of its degradation products, and the difficulty in utilizing its chlorine content, leading to low recycling rates and environmental concerns.

Innovation Solution

A method involving the use of waste PVC as a source for in situ generation of HCl through electrochemical dehalogenation, where PVC is admixed with an organic compound and an electrolyte, exposed to a negative voltage in an electrochemical cell, generating reactive halogen species that can halogenate organic compounds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If thermal activation or stoichiometric strong bases are used for PVC dechlorination, then the hydrocarbon content of PVC can be recovered, but the chlorine content becomes waste and requires hazardous conditions

Engineering Contradiction:

Improvechlorine content recoveryVSAvoidhazardous conditions

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful HCl release during PVC degradation into a useful reagent for halogenation reactions. By using electrochemical methods to generate HCl in situ from waste PVC, the previously harmful byproduct becomes a valuable resource for synthesizing organochlorine compounds, eliminating waste chlorine while avoiding hazardous thermal or chemical treatment conditions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces thermal activation and stoichiometric strong base methods with electrochemical activation. Instead of using high temperatures (250°C) or hazardous chemical reagents, the invention uses electrical current to directly dechlorinate PVC, generating HCl under mild, controllable conditions that are safer and more environmentally friendly

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If complete separation of PVC from other plastics is performed, then recycling quality can be maintained, but the process becomes challenging and costly

Engineering Contradiction:

Improverecycling qualityVSAvoidseparation process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent creates a universal electrochemical processing method that can handle mixed plastic waste containing PVC without requiring complete separation. The electrochemical dechlorination selectively targets chlorine-containing polymers regardless of other plastic components present, allowing direct processing of mixed waste streams while maintaining product quality and eliminating complex separation infrastructure

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention allows waste PVC to serve itself as the reagent for HCl generation. The chlorine atoms already present in the PVC polymer chain are used to generate HCl for halogenation reactions, eliminating the need for external chlorine sources or complex separation processes to isolate pure PVC before recycling

Inventive Principle:

Principle #25Self-service

3Productivity

If mechanical recycling is used for PVC, then material can be reused, but the plasticizing additives contaminate other recycled plastics

Engineering Contradiction:

Improverecycling rateVSAvoidadditive contamination

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the harmful plasticizing additives (phthalates) from the PVC waste stream through the electrochemical process. These additives are separated from the polymer matrix during the dechlorination and halogenation process, preventing their contamination of other recycled plastics while allowing the PVC to be recycled at higher rates

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method allows for the effective utilization of PVC's chlorine content, generating reactive halogen species for synthetic applications, such as pharmaceutical production, while also producing partially dechlorinated PVC products with potential industrial uses, thus enhancing recycling efficiency and reducing environmental hazards.

Implementation Method 1

the halogen containing polymer is dehalogenated by the cathode to generate a halogen anion

Methodology Applied

Scientific EffectElectrochemical reduction: Electrolysis

Implementation Method 2

the halogen anion is formed into a reactive halogen species by the anode

Methodology Applied

Scientific EffectElectrochemical oxidation: Electrolysis

Data Source

PatentUS20240327323A1Methods of Treating of Halogen- Containing Waste Plastic to Produce Halogenated Products

Publication Date: 2024.10.03 THE RGT UNIV OF MICHIGAN

AI summary

A method for halogenation of an organic compound with a halogen from a waste source comprising a halogen containing polymer includes admixing waste source with the organic compound, a solvent, and an electrolyte, wherein the solvent swells and/or dissolves the halogen containing polymer in the waste source; and exposing the admixture to a negative voltage in an electrochemical cell comprising a cathode and an oppositely disposed anode. The halogen containing polymer is dehalogenated by the cathode to generate a halogen anion. The halogen anode is formed into a reactive halogen species by the anode. The halogen species reacts with the organic compound to halogenate the organic compound