Chlorophenoxycarboxylate Selective Chlorination via Dual Catalyst System
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Solution Overview
Problem
Current methods for producing chlorophenoxycarboxylate have poor chlorination selectivity, result in the production of highly toxic dioxins, and generate significant hazardous waste, posing environmental and health risks, with low yield and high processing costs.
Innovation Solution
A method involving selective chlorination of phenoxycarboxylate at the 2-position and/or 4-position using a Lewis acid catalyst A and a sulfur-containing catalyst B, supported on silica gel, which improves chlorination selectivity and avoids the formation of dioxins, allowing for continuous operation and efficient catalyst reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phenol is used as main raw material with chlorination, then chlorophenol is obtained, but the product has extremely unpleasant pungent odor resulting in poor manufacturing condition and poor chlorination selectivity
Solution Approach 1:
The patent changes the reaction parameters by using phenoxycarboxylate as raw material instead of phenol, and employs a dual catalyst system (Lewis acid catalyst A and catalyst B with specific structure) to achieve selective chlorination at 2-position and/or 4-position, obtaining chlorophenoxycarboxylate with over 99.5% selectivity and avoiding the odor and selectivity issues of conventional chlorination
Solution Approach 2:
The patent introduces phenoxycarboxylate as an intermediary compound that facilitates selective chlorination. The carboxylate group acts as a directing group that guides the chlorination to specific positions (2 and/or 4), thereby improving selectivity and avoiding the harmful effects associated with direct phenol chlorination
2Productivity
If condensation reaction is performed between chlorophenol and chlorocarboxylic acid under alkaline condition, then chlorophenoxycarboxylic acid is obtained, but dioxins are produced which are highly toxic and difficult to degrade
Solution Approach 1:
The patent converts the harmful condensation reaction that produces dioxins into a beneficial selective substitution reaction. By using phenoxycarboxylate as raw material and performing selective chlorination, the method achieves high product yield while completely avoiding dioxin formation, effectively converting a harmful process into a safe one
Solution Approach 2:
The patent inverts the conventional synthesis route by starting from phenoxycarboxylate and performing chlorination directly to obtain chlorophenoxycarboxylate, rather than the traditional route of chlorinating phenol to get chlorophenol and then condensing with chlorocarboxylic acid. This inversion eliminates the dioxin-producing condensation step while maintaining productivity
3Productivity
If conventional synthesis process is used, then chlorophenoxycarboxylate can be produced, but the process generates large amount of wastewater containing hydroxy carboxylic acid and salt waste, and hazardous waste containing chlorophenols and chlorophenoxycarboxylic acids
Solution Approach 1:
The patent extracts and eliminates the waste-generating steps from the synthesis process. By using phenoxycarboxylate as raw material and performing selective chlorination followed by direct esterification, the method avoids generating hydroxy carboxylic acid and salt waste, significantly reducing wastewater and hazardous waste while maintaining product production
Solution Approach 2:
The patent changes the reaction parameters and pathway to achieve atom economy. The selective chlorination at specific positions (2 and/or 4) with over 99.5% selectivity minimizes by-product formation, and the direct esterification without isolation of intermediate acid reduces waste generation, thereby improving productivity while minimizing substance loss
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
The method achieves chlorination selectivity of over 99.5%, reduces untransformed raw material and by-product content, and significantly enhances product yield and environmental safety by eliminating dioxin production and minimizing waste generation.
Implementation Method 1
subjecting a phenoxycarboxylate to a selective chlorination reaction at 2-position and/or 4-position with a chlorinating agent under effect of a catalyst A and a catalyst B to obtain a chlorophenoxycarboxylate; the catalyst A is a Lewis acid
Data Source
AI summary
Provided is a method for producing a chlorophenoxycarboxylate, comprising the following steps of: a phenoxycarboxylate under actions of a catalyst A and a catalyst B performing a selective chlorination of a chlorinating agent at a 2-position and/or a 4-position to obtain the chlorophenoxycarboxylate; the catalyst A is a Lewis acid; and the catalyst B has the following structure: R1′—S—R2′. The present disclosure redesigns the process route, and finely screens the catalyst and the chlorinating agent, thereby effectively improving the chlorination selectivity while avoiding the loss of the active ingredient, and the content of the obtained chlorophenoxycarboxylate can reach more than 98.5%, and the yield can reach more than 99%.