Isocyanate Reactive Distillation Column Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for preparing isocyanate compounds, such as toluenediisocyanate, hexamethylenediisocyanate, and isophoronediisocyanate, face inefficiencies in equipment productivity, operating rate, energy efficiency, and yield due to hydrodynamic instabilities and pressure pulsations in distillation columns, leading to suboptimal reaction conditions and fouling.
Innovation Solution
A process involving a reaction step under pressure with phosgene and an organic solvent, followed by a reactive distillation step, where the reaction mixture is separated into gas and liquid streams, with the gas stream introduced mid-column and the liquid preheated before distillation, allowing for improved separation and decomposition of carbamyl chlorides, reducing hydrochloric acid presence, and optimizing the distillation process to enhance productivity and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional phosgenation and distillation process is used, then isocyanate compound can be produced, but equipment productivity and operating rate are reduced due to hydrodynamic instabilities and pressure pulsations
Solution Approach 1:
The process is segmented into distinct stages: phosgenation reaction step followed by a separate reactive distillation step. This segmentation allows each step to be optimized independently, with the distillation column receiving pre-treated feed that minimizes hydrodynamic instabilities and pressure pulsations, thereby improving both productivity and operating rate.
Solution Approach 2:
The reaction mixture is pre-treated in the phosgenation step before entering the distillation column. This preliminary action ensures that the feed to the distillation column has appropriate composition and conditions, preventing operational issues during distillation and enabling continuous operation at high productivity without interruptions for maintenance.
2Use of energy by moving object
If conventional distillation process is used, then isocyanate can be obtained, but energy efficiency is low and reaction yield optimization is limited
Solution Approach 1:
The distillation column combines separation function with reaction function in a reactive distillation process. The decomposition of carbamyl chlorides to isocyanates occurs within the distillation column, merging two operations into one. This reduces energy consumption compared to separate reaction and distillation steps, while simultaneously optimizing reaction yield through controlled conditions and in-situ product removal.
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 increases the productivity of the reactive distillation column by 40-50%, reduces fouling and maintenance needs, and allows for independent optimization of reaction yield and distillation column operation, achieving better energy efficiency and higher isocyanate purity.
Implementation Method 1
a preheating step of the liquid stream (F 2) at a temperature between 100°C and 250°C
Implementation Method 2
a stream distillation operation (F 4) designed to obtain: at the bottom of the distillation, (F 10), the expected isocyanate in the organic solvent and residual phosgene, at the top of the distillation, a gaseous phase (F 6) including phosgene and hydrochloric acid
Implementation Method 3
This results in the near-total decomposition of carbamyl chlorides before the stream enters the distillation column
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The subject of the present invention is a method for preparing an isocyanate compound. The invention relates more particularly to the preparation of a diisocyanate compound from the corresponding diamine compound. The invention is directed preferentially towards the preparation of toluene diisocyanate, of hexamethylene diisocyanate and of isophorone diisocyanate. The method for preparing an isocyanate compound according to the invention, which comprises a stage of reacting an amine compound and phosgene, under pressure, in the presence of an organic solvent; a stage of reactive distillation under pressure, is characterized in that it comprises, at the end of the phosgenation operation, a stage of separating the reaction mixture (F1) resulting from the phosgenation stage into a gas stream (F3) and a liquid stream (F2) essentially comprising the isocyanate precursors in the organic solvent, and a stage of preheating the liquid stream (F2) to a temperature of between 100°C and 250°C, before being conveyed to the distillation operation.