Isocyanate Production via Diaryl Carbonate Segmentation
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Solution Overview
Problem
Current methods for producing isocyanates using diaryl carbonates and amine compounds face challenges such as low yield, difficulty in separating and purifying the target product due to the formation of numerous by-products, and inefficient industrial processes, particularly when using alkyl polyamines which result in complex reaction mixtures and side reactions.
Innovation Solution
A process involving the reaction of diaryl carbonates with amine compounds to form aryl carbamates, followed by transferring the reaction mixture to a thermal decomposition vessel where the aryl carbamates undergo thermal decomposition to produce isocyanates, with specific conditions and solvents used to enhance yield and purity, including the use of aromatic hydroxy compounds as solvents and controlled temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If diaryl carbonates are reacted with alkyl polyamines to produce aryl carbamates, then the target compound can be obtained, but numerous urea compound by-products are formed making separation and purification extremely difficult
Solution Approach 1:
The patent divides the synthesis process into two distinct stages: first forming aryl carbamates from diaryl carbonates and alkyl polyamines, then separately removing urea by-products through a dedicated purification step using a solvent system. This segmentation allows each stage to be optimized independently, solving the contradiction between achieving high purity and avoiding complex separation processes.
Solution Approach 2:
The patent introduces a solvent system (comprising water and an organic solvent) as an intermediary medium to facilitate the removal of urea by-products. The solvent acts as a mediator that selectively dissolves or precipitates urea compounds, enabling efficient separation without requiring complex purification equipment or multiple processing steps.
2Productivity
If the reaction is carried out to high conversion, then yield of aryl carbamate improves, but side reactions increase producing more urea by-products
Solution Approach 1:
The patent performs the aryl carbamate formation reaction first to achieve high conversion, then applies a preliminary purification action using a solvent system before thermal decomposition. This preliminary removal of urea by-products prevents them from interfering with subsequent decomposition reactions and ensures high purity of the final isocyanate product.
Solution Approach 2:
The patent extracts and removes urea by-products from the reaction mixture using a solvent system comprising water and an organic solvent. This extraction step separates the desired aryl carbamate from unwanted urea compounds, allowing high conversion to be achieved without compromising final product purity.
3Productivity
If phosgene method is used to produce isocyanates, then production efficiency is high, but toxic phosgene and corrosive hydrogen chloride are generated requiring special handling
Solution Approach 1:
The patent replaces the harmful phosgene method with an alternative route using diaryl carbonates and amine compounds. This conversion eliminates toxic phosgene and corrosive hydrogen chloride from the process, while maintaining high production efficiency through the thermal decomposition of aryl carbamates to produce isocyanates.
Solution Approach 2:
The patent uses diaryl carbonates as a disposable raw material that can be readily converted to aryl carbamates and then decomposed to isocyanates. This approach eliminates the need for expensive and complex phosgene handling equipment, detoxification systems, and corrosion-resistant apparatus, thereby maintaining productivity while eliminating harmful factors.
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 allows for continuous and efficient production of isocyanates over a long period, improving yield and reducing the formation of by-products, thus overcoming the limitations of previous methods and enabling more effective industrial application.
Implementation Method 1
the aryl carbamate to a thermal decomposition reaction to thereby obtain the isocyanate
Data Source
AI summary
An object of the present invention is to provide a process that enables isocyanate to be produced stably over a long period of time and at high yield without encountering problems of the prior art during production of isocyanate without using phosgene. The present invention provides an isocyanate production process including the steps of: obtaining a reaction mixture containing an aryl carbamate having an aryl group originating in a diaryl carbonate, an aromatic hydroxy compound originating in a diaryl carbonate, and a diaryl carbonate, by reacting a diaryl carbonate and an amine compound in the presence of a reaction solvent in the form of an aromatic hydroxy compound; transferring the reaction mixture to a thermal decomposition reaction vessel; and obtaining isocyanate by applying the aryl carbamate to a thermal decomposition reaction, wherein the reaction vessel in which the reaction between the diaryl carbonate and the amine compound is carried out and the thermal decomposition reaction vessel for the aryl carbamate are different.