Defoamer Injection in Methanol Distillation Column
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Solution Overview
Problem
The separation efficiency of methanol from a mixture comprising methanol and water in a continuous distillation column, following the epoxidation of propene with hydrogen peroxide using a silicalite catalyst and methanol solvent, is impaired by foam formation, which has not been recognized in prior art.
Innovation Solution
Adding a liquid defoamer with a surface tension lower than methanol and forming a separate liquid phase at or above the feed point in the distillation column, specifically a polydimethylsiloxane-based defoamer with low solubility and low surface tension, to prevent foam formation and enhance separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a continuous distillation column is used to separate methanol from a mixture comprising methanol and water, then separation efficiency and column capacity are improved, but foam formation occurs inside the column which severely impairs separation efficiency and column capacity
Solution Approach 1:
A defoamer substance is introduced as an intermediary agent into the distillation column to eliminate the harmful foam formation. The defoamer acts as a mediator between the liquid phases, reducing surface tension and preventing foam stability, thereby restoring the column's separation efficiency and capacity without interfering with the methanol-water separation process
2Manufacturing precision
If a defoamer is added to suppress foam formation, then separation efficiency is improved, but the defoamer must have specific properties (low solubility and low surface tension) which limits the choice of defoamers
Solution Approach 1:
The invention specifies critical parameter ranges for the defoamer substance: solubility in the feed stream must be less than 10 mg/kg at 25°C and surface tension at the liquid-air interface must be less than 22 mN/m at 20°C. By defining these parameter thresholds, the invention narrows the selection criteria to ensure effective foam suppression while maintaining separation efficiency, transforming an open-ended material selection problem into a constrained optimization with clear specifications
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 addition of the defoamer effectively suppresses foam formation, improving the separation efficiency and capacity of the methanol distillation column by maintaining a second liquid phase rich in defoamer, resulting in a product with at least 90% methanol overhead and 90% water bottoms.
Implementation Method 1
a liquid defoamer having a solubility in the feed stream of less than 10 mg/kg at 25 °C and a surface tension at the liquid air interface of less than 22 mN/m at 20 °C
Implementation Method 2
a continuously operated methanol distillation column providing an overhead product comprising at least 90 % by weight methanol and a bottoms product comprising at least 90 % by weight water
Data Source
AI summary
In a process for the epoxidation of propene, comprising the steps: reacting propene with hydrogen peroxide in the presence of a titanium silicalite catalyst and a methanol solvent; separating non-reacted propene and propene oxide from the resulting reaction mixture to provide a solvent mixture comprising methanol and water in a combined amount of at least 90 % by weight; and feeding this solvent mixture as a feed stream to a continuously operated methanol distillation column at a feed point in the middle section of said column to provide an overhead product comprising at least 90 % by weight methanol and a bottoms product comprising at least 90 % by weight water; the addition of a liquid defoamer, having a solubility in the feed stream of less than 10 mg/kg at 25°C and a surface tension at the liquid air interface of less than 22 mN/m at 20 °C, at or above the feed point in an amount exceeding the solubility of the liquid defoamer in the feed stream suppresses foam formation in the methanol distillation column.