Continuous Reactive Distillation for High-Purity Diol Production
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Solution Overview
Problem
Current reactive distillation processes for producing high-purity diols face challenges in achieving stable, long-term industrial-scale production with high yield and selectivity, often resulting in low purity and efficiency due to fluctuations in composition, temperature, and pressure, especially when handling large amounts.
Innovation Solution
A process involving continuous multi-stage distillation columns with specific structural parameters and chimney trays is used to separate and purify diols, allowing for the continuous production of high-purity diols from cyclic carbonates and aliphatic monohydric alcohols, with a catalyst present in the reactive distillation column to enhance reaction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reactive distillation is used to produce diols from cyclic carbonates and aliphatic monohydric alcohols, then high conversion can be achieved, but stable continuous production for prolonged periods at industrial scale has not been attained
Solution Approach 1:
The patent segments the reactive distillation column into multiple functional sections: a reaction section with catalyst-containing packing for chemical conversion, and a distillation section for separating products. This segmentation allows independent optimization of reaction conditions and separation conditions, enabling stable continuous operation at industrial scale while maintaining high conversion rates.
2Productivity
If reactive distillation is used to produce diols, then high conversion can be achieved, but the purity of the diol product remains insufficient
Solution Approach 1:
The patent extracts the diol product continuously from the reaction zone through a side draw or bottom withdrawal in the distillation section. By separating the product removal function from the reaction function, the system achieves both high conversion (through continuous reactant feeding) and high purity (through continuous product extraction that prevents byproduct contamination).
Solution Approach 2:
The patent employs catalyst-containing packing in specific zones of the reactive distillation column, creating local catalytic activity where needed. This localized catalysis ensures high conversion rates at the reaction site while the distillation section maintains product purity through controlled separation, resolving the contradiction between conversion rate and product purity.
3Productivity
If existing reactive distillation processes are operated at industrial scale, then large amounts of diol can be produced, but fluctuations in composition, temperature, and pressure occur
Solution Approach 1:
The patent implements continuous monitoring and control of temperature, pressure, and composition parameters in the reactive distillation column. By maintaining optimal operating conditions through feedback control, the system achieves stable continuous production at industrial scale without the fluctuations that plague existing processes. The reflux ratio and feed rates are adjusted dynamically to maintain product specification.
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 enables the stable production of high-purity diols with yields exceeding 97% and purities of 99.9% or higher for extended periods, overcoming previous limitations in industrial-scale diol production by maintaining high efficiency and selectivity.
Implementation Method 1
material having a lower boiling point, than that of the diol is distilled off from the high boiling point reaction mixture using a continuous multi-stage distillation column
Implementation Method 2
a cyclic carbonate and an aliphatic monohydric alcohol are continuously fed into a reactive distillation column, and carrying out reactive distillation
Data Source
Figure 1
AI summary
It is an object of the present invention to provide a specific apparatus and process for producing a high-purity diol by taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, continuously feeding the starting materials into a continuous multi-stage distillation column A in which a catalyst is present, carrying out reactive distillation in the column A, continuously withdrawing a low boiling point reaction mixture AT containing a produced dialkyl carbonate and the aliphatic monohydric alcohol from an upper portion of the column A in a gaseous form, continuously withdrawing a high boiling point reaction mixture AB containing a produced diol from a lower portion of the column A in a liquid form, continuously feeding the high boiling point reaction mixture AB into a continuous multi-stage distillation column C, distilling off material having a lower boiling point than that of the diol contained in the high boiling point reaction mixture AB as a column top component CT and / or a side cut component Cs so as to obtain a column bottom component CB, continuously feeding the column bottom component CB into a continuous multi-stage distillation column E, and obtaining the diol as a side cut component Es from a side cut outlet of the continuous multi-stage distillation column E. Moreover, it is an object to thus provide a specific industrial apparatus and industrial production process that are inexpensive and, for example, enable the high-purity diol to be produced in an amount of not less than 1 ton / hr stably for a prolonged period of time (e.g. not less than 1000 hours, preferably not less than 3000 hours, more preferably not less than 5000 hours). The above objects can be attained by using a continuous multi-stage distillation column E having a specified structure, and withdrawing a liquid component from the side cut outlet, which is installed at the bottom of a chimney tray having a specified structure installed in an enrichment section of the continuous multi-stage distillation column E.