Reactive Distillation Column for Diol Production
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Solution Overview
Problem
Current reactive distillation processes for producing diols are not capable of continuous, stable production on an industrial scale for prolonged periods, often resulting in low yield and selectivity, and require multiple purification steps, which are energy-intensive and inefficient.
Innovation Solution
A process involving a continuous multi-stage distillation column with specific design parameters, including chimney trays and sieve trays, where cyclic carbonate and aliphatic monohydric alcohol are fed to perform reactive distillation, separating dialkyl carbonate and diol, and further purifying the diol by removing lower boiling point materials, allowing for high-yield, high-selectivity diol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reactive distillation processes are used for diol production, then the process can operate continuously, but the production amount is limited to small scales and stable operation for prolonged periods cannot be achieved
Solution Approach 1:
The patent applies parameter changes by optimizing the reactive distillation column configuration including the number of stages (5-20 stages), tray types (combining sieve trays and chimney trays), operating temperature (150-250°C), and pressure conditions. These parameter optimizations enable the system to achieve both high productivity (≥1 ton/hr) and reliable stable operation for prolonged periods (≥1000 hours), resolving the contradiction between production scale and operational stability.
2Manufacturing precision
If conventional distillation processes are used for diol purification, then multiple purification steps are required, but this increases energy consumption and reduces efficiency
Solution Approach 1:
The patent merges the reaction and distillation processes into a single reactive distillation column, where the transesterification reaction and separation occur simultaneously. This integration eliminates the need for separate reaction and purification steps, achieving high diol purity (≥99%) while significantly reducing energy consumption compared to conventional multi-step purification processes.
Solution Approach 2:
The continuous reactive distillation process maintains continuous useful action by continuously feeding reactants (cyclic carbonate and aliphatic monohydric alcohol) and continuously withdrawing purified diol product. This continuous operation eliminates batch processing interruptions and reduces overall energy consumption while maintaining high manufacturing precision.
3Productivity
If conventional reactive distillation columns are used, then the reaction can proceed with high conversion, but the column cannot handle industrial scale production of at least 1 ton/hr
Solution Approach 1:
The patent segments the distillation column into functional sections with different tray types: sieve trays in the lower section for efficient liquid-vapor contact and chimney trays in the upper section for enhanced separation. This segmentation allows the column to handle industrial-scale production (≥1 ton/hr) while maintaining manageable device complexity through standardized tray modules.
Solution Approach 2:
The patent introduces chimney trays that add a vertical dimension to the separation process, with chimneys extending upward from the tray plane. This dimensional addition enhances mass transfer efficiency and separation capability, enabling the column to handle high productivity requirements without proportionally increasing horizontal footprint or overall complexity.
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
Enables the production of diols with yields greater than 97% and selectivity of not less than 99% on an industrial scale of at least 1 ton/hr for extended periods, such as 1000 hours or more, without the need for excessive water and energy, improving industrial efficiency.
Implementation Method 1
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
Implementation Method 2
continuously feeding the high boiling point reaction mixture into a continuous multi-stage distillation column for separating off material having a lower boiling point than that of the diol contained in the high boiling point reaction mixture
Data Source
Figure 1
AI summary
It is an object of the present invention to provide a specific apparatus and process for producing a 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 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 C, and obtaining the diol as a side cut component ES from a side cut outlet of the continuous multi-stage distillation column C. Moreover, it is an object to thus provide a specific industrial apparatus and industrial production process that are inexpensive and, for example, enable the diol to be produced in an amount of not less than 1 ton / hr, preferably not less than 2 tons / hr, more preferably not less than 3 tons / 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). According to the present invention, the above objects can be attained by using a continuous multi-stage distillation column C 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 C.