Reactive Distillation Column Layout for Stable Dialkyl Carbonate Output
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Solution Overview
Problem
Existing methods for producing dialkyl carbonate and diol in industrially large quantities through reactive distillation systems face insufficient productivity and stability, as described in Patent Document 1.
Innovation Solution
A method involving a continuous multi-stage distillation column with specific dimensions, tray configurations, and catalyst composition is employed, allowing for stable and higher productivity of dialkyl carbonate and diol production, with a homogeneous catalyst of alkali metal and ethylene glycol, and optimized feed and withdrawal points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional continuous multi-stage distillation column is used for producing dialkyl carbonate and diol, then the production process can be maintained, but the productivity is insufficient relative to the apparatus size
Solution Approach 1:
The patent applies parameter changes by optimizing the column dimensions (length L and inner diameter D) and tray configurations (active area percentage and open area percentage) to achieve higher productivity. Specifically, the column length is set to 1,500-12,000 cm, inner diameter to 120-3,000 cm, with upper stage trays having 1-10% active area and 1-5% open area, middle stage trays having 20-40% active area and 2-6% open area, and lower stage trays having 30-50% active area and 3-8% open area. These parameter optimizations enable the system to produce 4.5 tons or more of dialkyl carbonate per hour and 2.7 tons or more of diol per hour.
2Productivity
If the column length and inner diameter are increased to improve productivity, then more product can be produced, but the apparatus size and complexity increase
Solution Approach 1:
The patent resolves this contradiction by establishing optimal parameter ranges that maximize productivity without excessive apparatus size. The column length L is optimized to 1,500-12,000 cm and inner diameter D to 120-3,000 cm, creating a balanced design. The tray configurations with specific active area and open area percentages further optimize the volume utilization, achieving high productivity (4.5 tons dialkyl carbonate/hr, 2.7 tons diol/hr) without requiring excessively large apparatus.
3Productivity
If tray active area and open area percentages are optimized to improve mass transfer efficiency, then reaction and distillation efficiency increase, but the tray structure complexity increases
Solution Approach 1:
The patent applies parameter changes to optimize tray structures without excessive complexity. The upper stage trays are designed with 1-10% active area and 1-5% open area, middle stage trays with 20-40% active area and 2-6% open area, and lower stage trays with 30-50% active area and 3-8% open area. These optimized parameters enhance mass transfer efficiency and reaction-distillation performance while maintaining manageable tray structure complexity.
Solution Approach 2:
The patent applies local quality by designing different tray configurations for different stages of the column. Each stage (upper, middle, lower) has tailored active area and open area percentages optimized for its specific function in the reaction-distillation process, improving overall efficiency without requiring uniform complex structures throughout.
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
The method achieves stable production of dialkyl carbonate and diol at enhanced rates, exceeding previous methods by 1.3 times, with high selectivity and yield, for prolonged periods up to 5,000 hours.
Implementation Method 1
carrying out reaction and distillation simultaneously in the column; continuously withdrawing a low boiling point reaction mixture containing the produced dialkyl carbonate in a gaseous form from an upper portion of the column; and continuously withdrawing a high boiling point reaction mixture containing the diol in a liquid form from a lower portion of the column
Implementation Method 2
a homogeneous catalyst is present; the homogeneous catalyst consists of a mixture of an alkali metal and ethylene glycol, and a mass ratio of the alkali metal to the ethylene glycol (alkali metal/ethylene glycol) in the homogeneous catalyst is 0.05 to 0.5
Data Source
AI summary
The method for industrially producing a dialkyl carbonate and a diol, in which the dialkyl carbonate and the diol are continuously produced through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising the steps of: continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present; carrying out reaction and distillation simultaneously in the column; continuously withdrawing a low boiling point reaction mixture containing the produced dialkyl carbonate in a gaseous form from an upper portion of the column; and continuously withdrawing a high boiling point reaction mixture containing the diol in a liquid form from a lower portion of the column, where the method satisfies specific requirements.