Reactive Distillation for Diaryl Carbonate Synthesis
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Solution Overview
Problem
Existing processes for preparing diaryl carbonates from dialkyl carbonates and aryl alcohols require high energy inputs, which is a limitation in terms of efficiency and cost-effectiveness.
Innovation Solution
A process utilizing three reactive distillation columns in series, where the top stream from the third column is recycled to the second, along with the introduction of dialkyl carbonate and aryl alcohol into the first column, and subsequent streams are processed through additional distillation columns to optimize energy usage and product recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the top stream from the third reactive distillation column is recycled to the first reactive distillation column (prior art process), then the process can operate continuously with all reactants present, but the energy requirements are high
Solution Approach 1:
The patent introduces a second reactive distillation column as an intermediary between the first and third columns. This intermediate column receives the top stream from the first column and feeds the bottom stream to the third column, allowing selective recycling of specific streams (top stream from third column to second column, and top stream from first column to second column) rather than direct recycling to the first column. This intermediary structure enables better energy management by optimizing where recycled streams are reintroduced into the system.
Solution Approach 2:
The patent changes the recycling parameters by modifying which column receives the recycled top stream from the third column (changing from first column in prior art to second column in the invention). This parameter change optimizes the energy balance of the system by reintroducing the recycled stream at a different stage in the process where it can be more effectively utilized, thereby reducing overall energy requirements while maintaining continuous operation.
2Use of energy by moving object
If three reactive distillation columns are used in series with top stream from third column recycled to second column, then energy requirements are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the distillation process into three separate reactive distillation columns instead of using a single integrated column or fewer columns. Each column performs a specific function in the series: the first column handles initial reactions, the second column receives recycled streams and continues the process, and the third column completes the conversion. This segmentation allows for optimized energy management through selective recycling while distributing the complexity across multiple specialized units rather than one complex integrated system.
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 significantly reduces the energy requirements for producing diaryl carbonates, as demonstrated by lower heating duties compared to traditional methods, thereby enhancing the process's efficiency and cost-effectiveness.
Implementation Method 1
introducing dialkyl carbonate and aryl alcohol into a first reactive distillation column; recovering from the first reactive distillation column a top stream comprising dialkyl carbonate and alkyl alcohol
Implementation Method 2
the first, second and third reactive distillation columns contain a catalyst
Implementation Method 3
In a first step transesterification of the dialkyl carbonate with the aryl alcohol takes place to yield alkyl aryl carbonate and alkyl alcohol
Implementation Method 4
In a second step disproportionation of the alkyl aryl carbonate takes place to yield diaryl carbonate and dialkyl carbonate
Data Source
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AI summary
The invention relates to a process for preparing a diaryl carbonate from a dialkyl carbonate and an aryl alcohol comprising: (a) introducing dialkyl carbonate and aryl alcohol into a first reactive distillation column; (b) recovering from the first reactive distillation column a top stream comprising dialkyl carbonate and alkyl alcohol and a bottom stream comprising alkyl aryl carbonate, aryl alcohol and dialkyl carbonate; (c) introducing the bottom stream from the first reactive distillation column into a second reactive distillation column; (d) recovering from the second reactive distillation column a top stream comprising dialkyl carbonate and a bottom stream comprising alkyl aryl carbonate, diaryl carbonate and aryl alcohol; (e) introducing the bottom stream from the second reactive distillation column into a third reactive distillation column; and (f ) recovering from the third reactive distillation column a top stream comprising aryl alcohol and a bottom stream comprising diaryl carbonate, wherein the top stream from the third reactive distillation column is recycled to the second reactive distillation column.