Hydrogenation Catalyst Regeneration via Feed Switching
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Solution Overview
Problem
Existing methods for continuous production of 4,4'-diamino-dicyclohexyl methane (H 12 MDA) face low catalyst productivity and increased costs due to catalyst deactivation, requiring shutdown for regeneration and separate equipment for catalyst restoration.
Innovation Solution
A method involving the hydrogenation of 4,4'-diamino-diphenyl methane (MDA) using a Rh/Al2O3 and Ru/Al2O3 catalyst system, where the feed is switched between 4,4'-MDA and a mixture of 2,4'-MDA and 4,4'-MDA to maintain high catalyst activity and productivity, allowing for on-line catalyst regeneration without system shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous hydrogenation is conducted using a supported ruthenium catalyst, then 4,4'-H 12 MDA can be produced continuously, but catalyst activity decreases over time requiring shutdown for regeneration
Solution Approach 1:
The patent implements continuous catalyst regeneration during the hydrogenation process by periodically switching between fresh catalyst and spent catalyst beds, ensuring uninterrupted production while maintaining catalyst activity. This allows the useful action of hydrogenation to continue without shutdowns.
Solution Approach 2:
The patent recovers active catalyst from spent catalyst by transferring it to a fresh catalyst bed, where it is reactivated by the hydrogenation reaction conditions. This discarding and recovering of catalyst activity eliminates the need for shutdowns and separate regeneration equipment.
2Reliability
If catalyst regeneration is performed using separate equipment and procedures, then catalyst activity can be restored, but device complexity and operational difficulty increase
Solution Approach 1:
The patent merges the catalyst regeneration function with the existing hydrogenation reaction system by using the same reactor and reaction conditions. The regeneration occurs in-situ during normal operation, eliminating the need for separate regeneration equipment and procedures.
Solution Approach 2:
The hydrogenation reaction system itself provides the service of regenerating the catalyst by transferring active catalyst species from spent to fresh catalyst beds using the reaction conditions already present, without requiring external regeneration systems.
3Productivity
If high conversion of 4,4'-MDA is achieved, then productivity increases, but catalyst deactivation occurs faster
Solution Approach 1:
The patent segments the catalyst system into multiple beds, with at least one fresh catalyst bed and one spent catalyst bed. This allows the system to maintain high conversion by periodically switching between beds, extending the overall service life of the catalyst system while preserving high productivity.
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 enhances catalyst productivity, maintains high yield and trans-trans-isomer content of 4,4'-H 12 MDA, and reduces production costs by continuously regenerating the catalyst during operation, improving catalytic efficiency and process simplicity.
Implementation Method 1
hydrogenation of 4,4'-diamino-diphenyl methane (MDA) using a Rh/Al2O3 and Ru/Al2O3 catalyst system
Implementation Method 2
hydrogenation of 4,4'-diamino-diphenyl methane (MDA)
Data Source
AI summary
Disclosed is a method for preparing diamino-dicyclohexyl methane (H12MDA) by hydrogenation of diamino-diphenyl methane (MDA). In the process, 4,4'-MDA used as the starting material is firstly hydrogenated to prepare 4,4'-H12MDA. When the activity of the catalyst is reduced, the feed is switched from 4,4'-MDA to the mixture of 2,4'-MDA and 4,4'-MDA, and then when the conversion is stabilized, the feed is switched to 4,4'-MDA again. The deactivated catalyst is activated on line by switching the feed to the mixture of 2,4'-MDA and 4,4'-MDA. 4,4'-H12MDA having the trans-trans isomer content of 16~24wt% is produced, and the mixture of 2,4'-H12MDA and 4,4'-H12MDA is also produced, wherein the content of 2,4'-H12MDA in the mixture is 4~15 wt%.