Spent Polyurethane Hydrogenation via Base Metal Catalysts
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Solution Overview
Problem
Current recycling processes for spent polyurethanes, particularly toluenediisocyanate-based polyurethanes, face challenges such as low catalyst turnover-activity, use of expensive precious metals, and undesired side reactions when attempting to depolymerize into valuable monomeric compounds like polyamines and polyols, with solvents like DMSO posing difficulties due to side product formation and separation issues.
Innovation Solution
A hydrogenation process for spent polyurethanes using a homogeneous transition metal catalyst complex from groups 7, 8, or 9 of the periodic table, in a non-reducible solvent with a dipole moment of 10·10−30 C·m or less, at elevated temperatures and pressures, to produce polyamines and polyols, allowing for their reintegration into the value chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If homogeneous transition metal catalyst complexes from groups 7, 8, or 9 are used for hydrogenation of spent polyurethanes, then catalytic activity and conversion efficiency are improved, but catalyst cost increases due to use of precious metals
Solution Approach 1:
The patent changes the parameter of catalyst metal selection from precious metals (groups 7-9) to base metals (groups 3-6, 11-13, 21-30), achieving similar catalytic activity through parameter optimization in metal choice, ligand structure, and reaction conditions
Solution Approach 2:
The patent replaces expensive precious metal catalysts with cheaper base metal catalysts that can be used in homogeneous systems, accepting that these catalysts may require more frequent replacement or regeneration while significantly reducing overall process cost
2Productivity
If DMSO is used as solvent for hydrogenation reaction, then reaction conversion is improved, but side product formation and separation difficulty increase
Solution Approach 1:
The patent extracts and removes DMSO from the reaction system, replacing it with alternative solvents that do not undergo hydrogenation to form dimethylsulfide side products, thereby eliminating the harmful effect while maintaining reaction efficiency
Solution Approach 2:
The patent converts the problematic property of DMSO (susceptibility to hydrogenation) by selecting solvents with similar beneficial properties (high boiling point, good solubility) but without the harmful side reaction tendency, turning the selection criterion into an advantage
3Productivity
If DMSO is used as solvent, then reaction conversion is improved, but separation of solvent from products becomes difficult due to high boiling point
Solution Approach 1:
The patent removes DMSO from the solvent system and replaces it with solvents that have lower boiling points and easier separation characteristics, eliminating the separation bottleneck while maintaining high conversion through alternative solvent selection
4Productivity
If elevated temperatures are used for hydrogenation, then reaction rate and conversion are improved, but energy consumption and risk of side reactions increase
Solution Approach 1:
The patent replaces thermal energy input with catalytic action, using sophisticated catalyst designs (homogeneous transition metal complexes with specific ligands) that enable the reaction to proceed at lower temperatures through enhanced catalytic activity rather than relying solely on thermal activation
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 process achieves higher conversions and avoids the drawbacks of previous methods by using less expensive catalysts and non-reducible solvents, facilitating the recovery of both polyols and aromatic compounds, thus enhancing the economic and environmental sustainability of polyurethane recycling.
Implementation Method 1
hydrogenating the spent polyurethanes in a hydrogen atmosphere in the presence of at least one homogeneous transition metal catalyst complex
Implementation Method 2
in the presence of at least one homogeneous transition metal catalyst complex
Data Source
AI summary
Spent polyurethanes are returned to the value chain by hydrogenating the spent polyurethanes in a hydrogen atmosphere in the presence of at least one homogeneous transition metal catalyst complex, wherein the transition metal is selected from metals of groups 7, 8, 9 and 10 of the periodic table of elements according to IUPAC, to obtain a polyamine and a polyol. The hydrogenation is carried out at a reaction temperature of at least 120° C. in a non-reducible solvent having a dipole moment of 10-1030 C·m or less.