Polyurethane Depolymerization With Ionic Liquid Phase Recovery
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Solution Overview
Problem
Existing polyurethane depolymerization methods require high temperatures and long reaction times, leading to inefficient yields and the need for costly purification steps, making it difficult to recycle polyurethane waste effectively.
Innovation Solution
A method using an ionic liquid, superbase catalyst, and nucleophilic agent at moderate temperatures (50-100°C) to depolymerize polyurethane into recyclable polyol, eliminating the need for volatile solvents and subsequent purification steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional depolymerization methods using protic solvents and strong bases are used, then depolymerization can be achieved, but high temperatures (130-250°C) and long reaction times (>12 h) are required, resulting in low yields (<85%) and unwanted side reactions
Solution Approach 1:
The invention changes the chemical parameters of the reaction system by introducing ionic liquids with specific properties (low volatility, high stability, tunable solubility) and using mild bases (pH 8-10) instead of strong bases. This parameter change enables depolymerization to proceed at lower temperatures (50-100°C) and shorter times (2-8 h) while achieving higher yields (>90%) and minimizing side reactions.
Solution Approach 2:
The ionic liquid acts as an intermediary substance that facilitates the depolymerization reaction. It serves multiple functions: dissolving the polyurethane substrate, stabilizing the transition state, and enabling the use of mild bases as catalysts. The ionic liquid mediates between the polyurethane and the nucleophilic agent, allowing the reaction to proceed under milder conditions with higher efficiency.
2Productivity
If high temperatures and long reaction times are used for depolymerization, then the reaction can proceed to completion, but costly purification steps are required and operational complexity increases
Solution Approach 1:
The invention extracts or removes the need for complex purification steps by using an ionic liquid system that naturally separates phases. The depolymerized polyol remains in the ionic liquid phase while unreacted polyurethane and byproducts form a separate phase that can be easily removed. This eliminates the need for costly purification equipment and operations, reducing device complexity while maintaining high productivity.
Solution Approach 2:
The ionic liquid is recovered and reused in subsequent depolymerization cycles without requiring purification. The system is designed so that the ionic liquid can be simply separated from the reaction mixture and reused, eliminating the need for energy-intensive purification processes. This reduces both operational complexity and costs while maintaining high depolymerization rates.
3Productivity
If conventional methods with volatile solvents are used, then depolymerization can be achieved, but the solvents require recovery and the process becomes less environmentally friendly
Solution Approach 1:
The invention replaces volatile organic solvents with ionic liquids that create an inert, non-volatile reaction environment. Ionic liquids have negligible vapor pressure and do not evaporate under depolymerization conditions, eliminating harmful solvent emissions. The ionic liquid provides a stable reaction medium that maintains depolymerization efficiency while being environmentally benign.
Solution Approach 2:
The invention uses ionic liquids that can be reused multiple times without degradation or loss of activity, replacing the conventional practice of using disposable volatile solvents that must be recovered or disposed of. The ionic liquid system is economically advantageous because the same ionic liquid can be used for multiple depolymerization cycles, reducing both costs and environmental impact.
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
The method achieves efficient depolymerization of polyurethane at lower temperatures and shorter times, allowing for easy recovery and reuse of the reaction medium, reducing operational complexity and costs.
Implementation Method 1
A method using an ionic liquid, superbase catalyst, and nucleophilic agent at moderate temperatures (50-100°C) to depolymerize polyurethane into recyclable polyol
Implementation Method 2
The most common chemical methods in the depolymerization of polyurethane are hydrolysis and glycolysis
Implementation Method 3
obtaining two immiscible fractions of the mixture obtained in step a): a first fraction, comprising at least a polyol mass; and a second fraction, comprising at least the ionic liquid and the basic catalyst
Data Source
AI summary
The present invention relates to a depolymerization method of a polyurethane mass, preferably, thermoset polyurethane. The method comprises four main steps: i) mixing the polyurethane mass with a depolymerization reaction medium comprising an ionic liquid in a proportion equal to or greater than 50% w/w with respect to the total weight of said medium, a superbase as a catalyst, and a nucleophilic agent in a proportion equal to or less than 15% w/w with respect to the total weight of said medium, subjecting said mixture to a temperature between 50-100° C. for a time comprised between 2 minutes and 10 hours; ii) adding a mass of a protic molecular solvent in an amount between 4 and 40 times more the weight of the depolymerization reaction medium; iii) subjecting the mixture of step ii) to a temperature between 20-60° C. for at least 1 hour; and iv) separating the fractions obtained in step iii); namely, a semisolid fraction comprising at least a polyol mass for reuse in the synthesis of a new polyurethane, and a single-phase liquid fraction comprising at least the ionic liquid and the basic catalyst, for their reuse in a new process for polyurethane depolymerization.