Thionocarbamate Synthesis via Phase Transfer Catalyst
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Solution Overview
Problem
Current methods for preparing thionocarbamate and co-producing 2-mercaptoethanol and O-alkylthioethyl xanthate face challenges such as low yield, environmental pollution, and complex processes, with existing synthesis methods being inefficient and difficult to scale up due to high catalyst solubility, by-product recycling issues, and instability of reagents.
Innovation Solution
A method involving an esterification reaction of xanthate with 2-haloethanol followed by an aminolysis reaction to produce thionocarbamate and 2-mercaptoethanol, with subsequent alkali washing for separation and acid washing to obtain high-purity products, allowing for the recycling of by-products and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the one-step catalytic synthesis process is used to prepare thionocarbamate, then the operation is simple and reaction steps are fewer, but the product yield is not high, catalysts completely enter the water phase and are difficult to recover, and a large amount of industrial wastewater is produced
Solution Approach 1:
The patent uses phase transfer catalyst (such as tetrabutylammonium bromide) as an intermediary substance that facilitates the reaction between reagents in different phases (organic and aqueous). The catalyst transfers reactants across the phase boundary, enabling the reaction to proceed efficiently while the catalyst itself remains in the organic phase and can be easily recovered, thus resolving the contradiction between simple operation and high yield.
2Ease of manufacture
If the one-step catalytic synthesis process is used, then the operation is simple and reaction steps are fewer, but catalysts such as nickel sulfate and palladium chloride have high solubility, which completely enter the water phase during the reaction, and are difficult to recover
Solution Approach 1:
The patent employs phase transfer catalyst that exhibits different solubility characteristics in different phases. The catalyst is specifically selected to be soluble in the organic phase but not in the aqueous phase, creating a localized concentration difference that enables easy separation and recovery. This local quality difference between phases allows the catalyst to remain in the organic layer after reaction, solving the recovery difficulty while maintaining operational simplicity.
3Productivity
If the dimethyl sulfate process is used, then the operation is simple and reaction efficiency is high, but due to the instability of dimethyl sulfate, it will be rapidly hydrolyzed into sulfuric acid and methanol in water, which makes it difficult to popularize in practical production
Solution Approach 1:
The patent changes the reaction parameters by using phase transfer catalyst and conducting the reaction in a two-phase system with controlled conditions. This approach maintains high reaction efficiency while avoiding the hydrolysis problem of dimethyl sulfate. The phase transfer catalyst enables the reaction to proceed efficiently at lower temperatures and shorter times, preventing the instability issue while maintaining productivity.
4Ease of manufacture
If the process of esterification and ammonolysis of xanthate is used, then the process has enough raw materials, simple process and easy mastering of production technology, but the by-product of sodium thioglycolate dissolves in the water phase, which is difficult to recycle and causes environmental problems
Solution Approach 1:
The patent converts the harmful environmental by-product (sodium thioglycolate) into a useful product (2-mercaptoethanol) through acidification treatment. The by-product that was previously difficult to recycle and environmentally problematic is now transformed into a valuable chemical intermediate with market value, thus converting the harm into benefit while maintaining process simplicity.
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 achieves high-purity thionocarbamate and O-alkylthioethyl xanthate production with improved yield and reduced environmental pollution, enabling efficient mineral flotation and recycling of by-products, thus enhancing economic value and operational simplicity.
Implementation Method 1
reacting xanthate and 2-haloethanol to prepare an ester product
Implementation Method 2
reacting the ester product with fatty amine to obtain a mixture product of thionocarbamate and 2-mercaptoethanol
Implementation Method 3
washing the mixture product with alkali to separate and obtain the thionocarbamate product
Implementation Method 4
washing the aqueous phase with acid to obtain a 2-mercaptoethanol product
Data Source
AI summary
The invention belongs to the field of mineral flotation collector materials, and particularly discloses a method for preparing thionocarbamate. In the preparation process, xanthate and 2-haloethanol are esterified to obtain O-alkyl-S-hydroxyethyl xanthate, and then O-alkyl-S-hydroxyethyl xanthate and fatty amine are reacted to obtain a mixture of thionocarbamate and 2-mercaptoethanol. The mixture of thionocarbamate and 2-mercaptoethanol is washed with alkali, and the oil phase and water phase are separated. The oil phase and water phase are thionocarbamate and 2-hydroxyethylthiolate, respectively, and 2-mercaptoethanol is obtained by washing with an acid. 2-alkylthioethanol is obtained by reacting 2-hydroxyethanethiolate with alkyl halide, and then with carbon disulfide and alkali to prepare O-alkylthioethyl xanthate. Thionocarbamate, 2-mercaptoethanol and O-alkylthioethyl xanthate prepared by this method possess high yield and high purity. The process is green and environmentally friendly, and is beneficial to the industrialization of co-production.