Amine Catalyst Purification via Enamine Formation
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Solution Overview
Problem
Current methods, such as fractional distillation, are ineffective in separating N,N,N'-trimethylbis(aminoethyl)ether from its undesirable co-product N,N,N',N'-tetramethylbis(aminoethyl)ether, which are both tertiary amine compounds of similar structure and molecular weight, limiting the purification of amine catalysts used in polyurethane production.
Innovation Solution
A process involving the reaction of a mixture of these amines with a carbonyl compound to form an enamine, which is then separated and converted back to the desired amine, allowing for the effective separation and purification of N,N,N'-trimethylbis(aminoethyl)ether from N,N,N',N'-tetramethylbis(aminoethyl)ether using carbonyl compounds like cyclohexanone, followed by hydrolysis to reform the purified amine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fractional distillation is used to separate N,N,N'-trimethylbis(aminoethyl)ether from N,N,N',N'-tetramethylbis(aminoethyl)ether, then the separation process is simple, but the separation effectiveness is insufficient due to similar molecular weights and structures
Solution Approach 1:
The patent introduces a carbonyl compound as an intermediary reagent that selectively reacts with the secondary amine group of N,N,N'-trimethylbis(aminoethyl)ether to form an enamine intermediate. This intermediary enables differentiation between the two amine compounds based on their chemical reactivity rather than physical properties, achieving effective separation through subsequent distillation of the enamine from the unreacted di-tertiary amine.
Solution Approach 2:
The patent changes the chemical state parameter of the amine compounds by converting the secondary amine group into an enamine through reaction with carbonyl compound. This parameter change (from secondary amine to enamine) creates sufficient volatility difference to enable separation by distillation, overcoming the limitation of similar molecular weights and structures.
2Manufacturing precision
If carbonyl compound reaction is used to form enamine for separation, then the purification purity is high, but the process complexity increases due to additional reaction and conversion steps
Solution Approach 1:
The patent performs a preliminary chemical modification by reacting the amine mixture with carbonyl compound before separation. This preliminary action converts the target compound into an enamine with distinct physical properties, enabling effective separation. The preliminary chemical transformation is followed by separation and then reversal to recover the pure amine product.
Solution Approach 2:
The patent temporarily discards the original amine structure by converting it to an enamine intermediate for separation purposes. After separation, the enamine is recovered and converted back to the original amine, effectively recovering the purified target compound. This temporary structural change enables separation that would otherwise be impossible.
3Manufacturing precision
If high levels of tetramethyl product are produced, then the catalyst purity is improved, but the yield of desired trimethyl product decreases
Solution Approach 1:
The patent converts the harmful effect of tetramethyl product formation (which reduces desired product yield) into a beneficial separation handle. The tetramethyl product, which was previously an unwanted impurity, now serves as the unreacted starting material in the separation process, allowing selective recovery of the desired trimethyl amine through enamine formation and subsequent hydrolysis.
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 method enables high purity separation of N,N,N'-trimethylbis(aminoethyl)ether, achieving up to 99.9% purity with minimal residual tetramethyl derivative, making it suitable for use as a polyurethane catalyst, and is not feasible through fractional distillation alone.
Implementation Method 1
contacting a mixture of the first amine and the di-tertiary amine with a carbonyl compound capable of forming an enamine such that the carbonyl compound reacts with the first amine to form an enamine
Implementation Method 2
separating the enamine from the di-tertiary amine
Implementation Method 3
subsequently converting the enamine to the first amine
Data Source
AI summary
A process for the separation of a first amine having a tertiary amine group and a secondary amine group such as N,N,N'-trimethyIbis(aminoethyl)ether from a di-tertiary amine such as N,N,N',N'-tetramethylbis(aminoethyl)ether, comprising: contacting a mixture of the first amine and the di-tertiary amine with a carbonyl compound capable of forming an enamine such that the carbonyl compound reacts with the first amine to form an enamine; separating the enamine from the di-tertiary amine; and subsequently converting the enamine to the first amine.