2,3-Dichlorobutadiene Production via Segmented Dehydrochlorination and Chlorination
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Solution Overview
Problem
Current dehydrochlorination processes for producing 2,3-dichlorobutadiene-1,3 from 1,2,3,4-tetrachlorobutane result in significant formation of byproduct isomers with alpha-chlorine substituents, which are difficult to separate and lead to oxidative degradation of polymers, limiting conversion levels to maintain product purity and reducing yield.
Innovation Solution
A process involving dehydrochlorination of 1,2,3,4-tetrachlorobutane with an aqueous base followed by further chlorination with gaseous chlorine, under controlled conditions to selectively chlorinate byproducts while minimizing conversion of 2,3-dichlorobutadiene-1,3, allowing for isolation of a composition with at least 90% 2,3-dichlorobutadiene-1,3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dehydrochlorination reaction is carried out to high conversion, then yield of 2,3-dichlorobutadiene-1,3 is improved, but formation of byproduct isomers with alpha-chlorine substituents increases
Solution Approach 1:
The process is divided into two distinct stages: (1) dehydrochlorination reaction stage to produce 2,3-dichlorobutadiene-1,3 along with byproduct isomers, and (2) selective chlorination stage to convert byproduct isomers into easily separable compounds. This segmentation allows high conversion in the first stage without compromising final product purity, as the byproducts are treated separately in the second stage.
Solution Approach 2:
The byproduct isomers with alpha-chlorine substituents, which were previously considered harmful contaminants limiting conversion, are converted into beneficial intermediates through selective chlorination. These byproducts are transformed into compounds with different physical properties (higher boiling points) that can be easily separated from the desired product, thus converting the harmful effect into a benefit for purification.
2Manufacturing precision
If conversion is limited to maintain product purity, then byproduct formation is reduced, but yield and productivity decrease
Solution Approach 1:
The process separates the production and purification functions into two stages. The first stage operates at high conversion without purity constraints, maximizing yield. The second stage handles purification by selectively chlorinating byproducts, which are then easily separated. This segmentation resolves the contradiction by allowing high conversion while maintaining final product purity through post-reaction treatment.
Solution Approach 2:
The selective chlorination of byproduct isomers is performed as a preliminary purification step before final product isolation. By converting byproducts into compounds with distinctly different physical properties beforehand, the subsequent separation becomes straightforward, enabling high yield from the dehydrochlorination step while ensuring high final product purity.
3Productivity
If phase transfer catalysts are used to increase conversion, then reaction efficiency is improved, but byproduct isomer formation increases
Solution Approach 1:
The process segments the reaction and purification steps. Phase transfer catalysts can be used in the dehydrochlorination stage to achieve high conversion and efficiency. The resulting byproduct isomers are then selectively chlorinated in a separate stage, converting them into easily separable compounds. This segmentation allows the use of catalysts to boost productivity without compromising final product purity.
Solution Approach 2:
The byproduct isomers formed during catalyzed dehydrochlorination are converted into beneficial intermediates through selective chlorination. These chlorinated byproducts have different physical properties that facilitate easy separation from the desired 2,3-dichlorobutadiene-1,3, thus converting the harmful effect of increased byproduct formation into a benefit for purification.
4Ease of manufacture
If isomers with alpha-chlorine substituents are present in product, then separation difficulty increases, but polymerization performance deteriorates due to oxidative degradation
Solution Approach 1:
The byproduct isomers containing alpha-chlorine substituents are selectively chlorinated to form compounds with even higher chlorine content. These chlorinated byproducts have significantly different physical properties (higher boiling points) that make them easily separable from the desired product. Additionally, removing these isomers prevents their incorporation into polymer chains, thereby eliminating the source of oxidative degradation and improving polymer stability.
Solution Approach 2:
The process segments purification and polymerization protection functions. The selective chlorination step specifically targets and modifies byproduct isomers, separating them from the desired product through physical property differences. This segmentation ensures that only pure 2,3-dichlorobutadiene-1,3 proceeds to polymerization, protecting polymer stability while making separation easier.
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 high conversion and purity of 2,3-dichlorobutadiene-1,3 while minimizing the formation of isomers with alpha-chlorine substituents, enhancing the efficiency and economic viability of the production process.
Implementation Method 1
dehydrochlorination of 1,2,3,4-tetrachlorobutane with an aqueous base
Implementation Method 2
further chlorination with gaseous chlorine, under controlled conditions to selectively chlorinate byproducts
Data Source
AI summary
2,3-dichlorobutadiene-1,3 of high purity is produced from 1,2,3,4-tetrachlorobutane by a process comprising the steps of dehydrochlorination, chlorination of the reaction product obtained in the dehydrochlorination step and subsequent separation of a 2,3-dichlorobutadiene-1,3 composition from the reaction product of the chlorination step.