Intermittent H12MDA Production with Low Trans-Trans Isomer
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Solution Overview
Problem
Existing methods for producing diaminodicyclohexylmethane (H12MDA) struggle to achieve a low amount of the thermodynamically stable trans-trans isomer due to high-temperature reactions and complex separation processes, leading to increased production costs and reduced catalyst efficiency.
Innovation Solution
The method involves controlling the hydrogenation reaction of 4,4'-diaminodiphenyl methane (MDA) in an organic solvent at specific temperature and pressure conditions, stopping the reaction when hydrogen consumption reaches 85-99.5% of theoretical, and recycling un-reacted materials to optimize the selectivity of H12MDA and reduce the trans-trans isomer content, using rhodium- or ruthenium-supported catalysts with controlled concentrations of MDA and hexamethylene diamine (H6MDA).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature hydrogenation reaction is performed to achieve complete conversion of MDA, then production capacity is improved, but the amount of trans-trans isomer increases due to thermodynamic equilibrium
Solution Approach 1:
The patent applies partial action by stopping the hydrogenation reaction at 85-99.5% conversion of MDA, rather than allowing complete conversion. This prevents the system from reaching thermodynamic equilibrium where trans-trans isomer predominates (50%), thereby maintaining lower trans-trans isomer content (below 22.25%) while still achieving high production capacity through continuous operation and recycling of unreacted materials.
Solution Approach 2:
The patent employs preliminary action by using a pre-hydrogenation treatment with a nickel catalyst before the main hydrogenation with ruthenium catalyst. This preliminary step removes impurities that would otherwise poison the expensive ruthenium catalyst, extending its life and maintaining its ability to produce low trans-trans isomer content products consistently over time.
2Productivity
If the reaction is extended to reach complete conversion, then productivity is improved, but catalyst activity deteriorates rapidly due to poisoning by impurities
Solution Approach 1:
The patent applies preliminary action by using a pre-hydrogenation treatment with a nickel catalyst before the main hydrogenation with ruthenium catalyst. This preliminary step removes impurities that would otherwise poison the expensive ruthenium catalyst, extending its life and maintaining its ability to produce low trans-trans isomer content products consistently over time.
Solution Approach 2:
The nickel catalyst serves as an intermediary that performs the function of removing impurities from the feedstock before the main reaction. This protective intermediary role allows the expensive ruthenium catalyst to operate without direct exposure to poisoning impurities, thereby maintaining its activity and reliability throughout the production process.
3Manufacturing precision
If complex separation processes are used to remove trans-trans isomer, then manufacturing precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent applies partial action by stopping the hydrogenation reaction at 85-99.5% conversion of MDA, rather than allowing complete conversion. This prevents the system from reaching thermodynamic equilibrium where trans-trans isomer predominates (50%), thereby maintaining lower trans-trans isomer content (below 22.25%) while still achieving high production capacity through continuous operation and recycling of unreacted materials.
Solution Approach 2:
The patent extracts the problematic trans-trans isomer formation by controlling the reaction to stop before thermodynamic equilibrium is reached. By taking out the isomerization step that would otherwise occur during extended reaction time or high-temperature operation, the process inherently produces low trans-trans isomer content product without requiring complex downstream separation equipment.
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 approach effectively controls the trans-trans isomer content in H12MDA to below 22.25 wt%, increases catalyst efficiency, reduces production costs, and enhances production capacity by restraining competing reactions and polymer formation, while being compatible with previous catalyst modification methods.
Implementation Method 1
subjecting MDA as a raw material to a hydrogenation reaction in an organic solvent at a reaction temperature of 50-230°C and under hydrogen pressure of 10-300 bar in the presence of a catalyst to generate H12MDA
Implementation Method 2
hydrogenation reaction of 4,4'-diaminodiphenyl methane (MDA) in an organic solvent at specific temperature and pressure conditions
Data Source
AI summary
The present invention discloses a method for intermittently producing 4,4′-diaminodicyclohexyl methane (H12MDA) with a low amount of the trans-trans isomer thereof, which comprises: controlling the reaction process by stopping the reaction when, except for a solvent, the reaction solution comprises MDA of 0-5 wt % and H6MDA of 1-20 wt %; and b) separating the reaction solution obtained from step a) by conventional means to obtain H12MDA product with desired purity, and allowing the un-reacted material and intermediate product to be recycled to the reactor after being accumulated. The method of the present invention decreases the amount of the trans-trans isomer in H12MDA, increases the yield of the reaction, and reduces the production cost. The present invention also provides a post treatment process of the reaction mixture.