Propylene Oxide Purification via Extractive Distillation
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Solution Overview
Problem
Current methods for purifying propylene oxide from epoxidation reaction products, particularly those using titanium-containing zeolite catalysts, face challenges in achieving high purity while minimizing yield loss due to side-reactions with methanol and extractive solvents, resulting in unacceptable concentrations of impurities like methanol and aldehydes.
Innovation Solution
A novel process involving extractive distillation where a propylene oxide reaction product is introduced into a bottom section of a distillation zone with water introduced in the upper-half, allowing for a purified propylene oxide stream to be obtained with minimal yield loss, specifically maintaining less than 0.3 mole percent propylene oxide loss, and further refining to meet commercial grade purity standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extractive distillation is used to remove methanol and water from propylene oxide, then purity of propylene oxide is improved, but yield loss increases due to side-reactions with extractive solvent and methanol
Solution Approach 1:
The patent applies parameter changes by carefully controlling the bottoms temperature (60-100°C) and operating pressure during extractive distillation to minimize side-reactions between propylene oxide and methanol/water, thereby reducing yield loss while achieving the required purity specifications of ≤10 ppm methanol, ≤100 ppm water, and ≤30 ppm aldehydes
Solution Approach 2:
The patent uses water as an extractive solvent (intermediary) to selectively separate methanol and water from propylene oxide in the distillation column, allowing the propylene oxide to be recovered in high purity form while minimizing direct contact and reaction between propylene oxide and the harmful impurities
2Manufacturing precision
If conventional extractive distillation is used to purify propylene oxide, then methanol and water are removed, but purification difficulty remains due to high boiling point of glycols and formation of azeotropes
Solution Approach 1:
The patent utilizes phase transitions during extractive distillation, where water as the extractive solvent changes phase and selectively interacts with methanol and water impurities, allowing them to be separated from propylene oxide through controlled vaporization and condensation in the distillation column
Solution Approach 2:
The patent changes operating parameters including maintaining bottoms temperature between 60-100°C and controlling reflux ratios to optimize the separation of propylene oxide from methanol and water, overcoming the purification difficulties posed by azeotropes and high boiling point glycols
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 process effectively separates and purifies propylene oxide, achieving high efficiency with minimal loss to glycols and other heavies, resulting in a product meeting commercial grade purity standards with reduced methanol and water concentrations.
Implementation Method 1
A novel process involving extractive distillation where a propylene oxide reaction product is introduced into a bottom section of a distillation zone with water introduced in the upper-half
Implementation Method 2
water introduced in the upper-half section of said extractive distillation zone
Data Source
AI summary
A process of separating a purified propylene oxide from a crude epoxidation product produced, preferably, in an epoxidation reaction of propylene with hydrogen peroxide. The process involves removing bulk water, bulk methanol, and unreacted propylene from the crude epoxidation product and thereafter subjecting the resulting propylene oxide product to extractive distillation with water as an extraction solvent. Under distillation conditions, including a bottoms temperature of greater than about 55° C. and less than about 75° C., an overhead or side-cut distillate stream containing a purified propylene oxide is obtained with low yield loss of propylene oxide to propylene glycols and other glycol heavies. The purified propylene oxide can be further purified in a finishing distillation to obtain propylene oxide meeting commercial grade purity requirements.