Heterogeneous Catalyst Regeneration for Diamine Synthesis
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Solution Overview
Problem
Current methods for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines face challenges such as low yields, catalyst deactivation, and the formation of unwanted by-products, leading to high raw material costs and complex purification processes.
Innovation Solution
A process involving the use of heterogeneous metal-based catalyst systems, where ammonia and hydrogen are fed over the catalysts at specific temperatures and pressures to improve catalytic activity, allowing for the efficient conversion of cyanoaldehydes to diamines, with the catalysts being treated with ammonia and hydrogen to restore activity when yields decline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional nitrile reduction conditions and catalysts are used, then complete reduction of the nitrile group is achieved, but the aldehyde is reduced to the corresponding alcohol resulting in yield loss
Solution Approach 1:
The patent applies parameter changes by carefully controlling reaction conditions including temperature ranges (60-200°C), pressure conditions (1-100 atm), and ammonia-to-substrate ratios (0.5:1 to 10:1) to achieve selective nitrile reduction while preventing aldehyde reduction to alcohol, thereby resolving the contradiction between complete nitrile reduction and avoiding unwanted aldehyde reduction
2Productivity
If catalysts for reductive amination of aldehyde are used, then reductive amination proceeds, but the nitrile group reduction is incomplete resulting in yield loss to intermediate aminonitriles
Solution Approach 1:
The patent uses parameter changes by optimizing reaction conditions including elevated temperatures (80-200°C), specific pressure ranges (1-100 atm), and controlled ammonia-to-substrate ratios (2:1 to 20:1) to enable both reductive amination of the aldehyde and complete reduction of the nitrile group simultaneously, avoiding accumulation of intermediate aminonitriles
3Productivity
If catalysts providing good yields to diamine product are used, then high initial yield is achieved, but catalyst activity for nitrile hydrogenation is lost within less than 250 hours
Solution Approach 1:
The patent applies preliminary action by pre-treating the catalyst with ammonia and hydrogen before the main reaction to restore and optimize catalytic activity, which extends catalyst lifetime and maintains consistent performance for nitrile hydrogenation over extended operation periods beyond 250 hours
Solution Approach 2:
The patent implements periodic action through intermittent treatment cycles where ammonia and hydrogen are fed to the catalyst at regular intervals during operation to regenerate active sites and maintain catalytic activity, thereby extending the functional lifetime of the catalyst while maintaining high diamine product yields
4Object-affected harmful factors
If protecting groups are used to suppress by-product formation, then polymerization resistance is improved, but additional raw materials and chemical species must be removed and recycled
Solution Approach 1:
The patent applies the taking out principle by completely eliminating protecting groups from the synthesis pathway, thereby removing the associated purification and recycling steps while still achieving suppression of polymerization and unwanted by-products through optimized reaction conditions including controlled temperature, pressure, and ammonia-to-substrate ratios
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 enhances the catalytic activity and extends the lifetime of catalysts, resulting in higher yields of 1,3- and 1,4-bis(aminomethyl)cyclohexane diamines, reducing production costs and simplifying the purification process.
Implementation Method 1
heterogeneous metal-based catalyst systems for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines
Implementation Method 2
reductive amination of hydroformylated 1,2,3,6-tetrahydrobenzaldehyde using a sponge-metal catalyst
Implementation Method 3
feeding ammonia, optionally hydrogen, and one or more solvents over one or more heterogeneous metal based catalyst systems
Data Source
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AI summary
The instant invention provides a process for improving catalytic activity of catalyst systems for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines. The process for improving catalytic activity of catalyst systems for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines comprises the steps of: (1) feeding ammonia, optionally hydrogen, and optionally one or more solvents over one or more heterogeneous metal based catalyst systems having a reduced catalytic activity for a period of greater than 1 hour at a temperature in the range of from 50° C to 500° C; wherein said one or more heterogeneous metal based catalyst systems have a yield of less than 90 percent based on the molar conversion of cyanoaldehydes to diamines; and (2) thereby improving the catalytic activity of said one or more heterogeneous metal based catalyst systems.