Isocyanate Quenching Process with Segmented Solvent Streams
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Solution Overview
Problem
Existing isocyanate production processes face challenges with thermal instability of diisocyanates at high temperatures, leading to undesirable by-product formation and deposition issues during rapid cooling, which complicates the separation and purification of isocyanates.
Innovation Solution
A process involving phosgenation of primary amines in the gas phase, where the gaseous reaction product mixture is cooled with a quench liquid containing up to 50% organic solvent, followed by phase separation and introduction of a solvent stream with over 50% organic solvents into the collection zone or tank, reducing deposits and solvent content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gaseous reaction product mixture is rapidly cooled by injecting a quench liquid with high organic solvent content, then the condensation of isocyanate is improved, but deposits form in the quench zone and device complexity increases
Solution Approach 1:
The quenching process is divided into two distinct stages: first, rapid cooling with a quench liquid containing limited organic solvent (≤50 wt%) to condense isocyanate while minimizing deposits; second, washing with a separate solvent stream (>50 wt% organic solvent) to remove any deposited substances. This segmentation allows each stage to optimize for its specific function without the negative effects of the other.
Solution Approach 2:
A washing solvent stream acts as an intermediary substance that mediates between the quench zone and the collection zone. This solvent stream (>50 wt% organic solvent) washes the liquid phase to remove deposits, serving as a bridge that transfers cleaning function without requiring the quench liquid itself to have high solvent content.
2Manufacturing precision
If a quench liquid with high organic solvent content is used, then isocyanate condensation is enhanced, but the amount of solvent to be removed increases
Solution Approach 1:
The solvent removal burden is segmented between two functions: the quench liquid (≤50 wt% organic solvent) performs rapid cooling and initial condensation, while a separate washing solvent stream (>50 wt% organic solvent) performs final purification. This segmentation allows the system to achieve complete condensation without requiring the quench liquid itself to contain excessive solvent that would need removal.
Solution Approach 2:
The washing solvent stream, which contains >50 wt% organic solvent, is designed to be largely discarded or minimized after performing its washing function. By separating the washing function from the quenching function, the process can use a high-solvent stream for washing (which can be discarded) rather than requiring the quench liquid to have high solvent content (which would need to be recovered and removed from the product).
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 approach minimizes deposits in the quench zone, maintains product quality, and reduces the overall solvent usage, facilitating easier solvent removal and process efficiency.
Implementation Method 1
the gaseous reaction product mixture is cooled by contact with at least one stream of a quench liquid in a quench zone
Implementation Method 2
ensuring the most complete possible condensation of the isocyanate formed
Implementation Method 3
the mixture of reaction product mixture and quench liquid thus obtained is separated into a liquid and a gaseous phase in a collection zone
Data Source
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AI summary
The invention relates to a method for producing an isocyanate by phosgenating the corresponding primary amine in the gas phase, wherein the gaseous reaction product mixture is cooled by being brought into contact with at least one flow of a quenching liquid in a quenching zone, wherein the quenching liquid used in total comprises, based on the total mass, organic solvents in a proportion of maximally 50.0% by mass, and the remainder of up to 100% by mass consists of at least the isocyanate to be produced, thereby obtaining a mixture of the reaction product mixture and the quenching liquid. Furthermore, the mixture obtained in this manner of the reaction product mixture and the quenching liquid is separated into a liquid and a gaseous phase in a collection zone, and a liquid solvent intermediate flow comprising more than 50.0% by mass of organic solvents, based on the total mass of the liquid solvent intermediate flow, is conducted into the collection zone and/or into a collection tank arranged fluidically downstream of the collection zone for the liquid phase obtained in the collection zone.