Isocyanate Gas-Phase Quenching with Low-Solvent Recycle
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Solution Overview
Problem
Existing methods for producing isocyanates in the gas phase face challenges such as deposit formation in the quenching area, high solvent content leading to energy-intensive separation, and complexity in separating isocyanate from gaseous streams due to vapor generation, which complicates downstream processing and can result in apparatus blockages.
Innovation Solution
A process involving phosgenation of primary amines in the gas phase, where the gaseous reaction product mixture is cooled with a quenching liquid containing a maximum of 25% organic solvents by mass, with part of the condensed mixture recycled as quenching liquid, allowing for efficient phase separation and reduced solvent content in the condensation product, thereby minimizing deposits and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If quenching liquid with high organic solvent content is used to cool the gaseous reaction product mixture, then complete condensation of isocyanate is achieved, but deposit formation in the quenching area increases and energy consumption for solvent separation increases
Solution Approach 1:
The invention changes the compositional parameter of the quenching liquid by limiting organic solvent content to a maximum of 25% by mass, with the remainder being 100% by mass of the isocyanate to be produced. This parameter change reduces deposit formation while maintaining condensation effectiveness through the use of pure isocyanate as the primary quenching medium.
Solution Approach 2:
The invention implements a self-service mechanism where part of the condensed reaction product mixture after further cooling is used as the quenching liquid. This creates a closed loop where the process product itself serves as the cooling medium, eliminating the need for external solvents and reducing deposit formation.
2Manufacturing precision
If quenching liquid with high organic solvent content is used to cool the gaseous reaction product mixture, then complete condensation of isocyanate is achieved, but energy consumption for solvent separation increases
Solution Approach 1:
The invention changes the compositional parameter of the quenching liquid by limiting organic solvent content to a maximum of 25% by mass. This reduction in solvent content directly decreases the energy required for solvent separation in downstream processing, while condensation completeness is maintained through optimized quenching conditions.
Solution Approach 2:
By using the condensed reaction product mixture itself as the quenching liquid, the process eliminates the need for large amounts of external solvents that would require energy-intensive separation. The system serves itself by recycling the product as the cooling medium.
3Productivity
If quenching liquid with high organic solvent content is used, then isocyanate condensation is efficient, but downstream processing complexity increases due to vapor generation
Solution Approach 1:
The invention changes the compositional parameter of the quenching liquid to contain a maximum of 25% by mass organic solvent. This parameter change reduces vapor generation in downstream processing, simplifying separation equipment requirements and reducing processing complexity while maintaining condensation efficiency.
4Quantity of substance
If high proportion of organic solvents is used in quenching liquid, then isocyanate solubility is improved, but apparatus blockages due to deposit formation increase
Solution Approach 1:
The invention changes the compositional parameter of the quenching liquid by limiting organic solvent to a maximum of 25% by mass. This parameter change reduces the solubility of isocyanate in the quenching liquid, promoting controlled condensation while minimizing deposit formation that causes apparatus blockages.
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 effectively reduces deposit formation, minimizes solvent content in the condensation product, simplifies further processing, and decreases energy consumption by enabling efficient isocyanate recovery with low solvent usage, enhancing the overall process efficiency and apparatus integrity.
Implementation Method 1
the gaseous reaction product mixture is cooled and partially condensed by bringing it into contact with at least one stream of a quenching liquid
Implementation Method 2
the gaseous reaction product mixture is cooled and partially condensed by bringing it into contact with at least one stream of a quenching liquid
Data Source
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AI summary
The invention relates to a method for producing isocyanates by phosgenating the corresponding primary amines in the gas phase, wherein the raw gaseous reaction product mixture is cooled and partially condensed by being brought into contact with at least one flow of a quenching liquid, and using a part of the condensed reaction product mixture as a component, optionally the only component, of the at least one flow of the quenching liquid after an additional cooling process. The quenching liquid used in total comprises, based on the total mass, organic solvents in a proportion of maximally 25% by mass, and the remainder of up to 100% by mass consists of at least the isocyanate to be produced. Furthermore, the reaction product mixture components which are not condensed under the influence of the quenching liquid are freed of isocyanate components in a scrubber column, and a scrubber liquid- and isocyanate-containing liquid flow is obtained with, based on the total mass, a content of organic solvents of 0.0% by mass up to 10% by mass, in particular 0.0% by mass up to 5.0% by mass.