Nanofiltration Membrane Separating Polypropylene Oxide Impurities
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Solution Overview
Problem
Existing membrane separation methods for removing poly(propylene oxide) from propylene oxide suffer from low and unstable selectivity and permeate flow, leading to inconsistent quality of propylene oxide suitable for polyurethane foam production, with ultrafiltration membranes fouling and having low poly(propylene oxide) rejection rates.
Innovation Solution
Employing non-porous or nanofiltration membranes with average pore sizes of 0 to 5 nm, which are resistant to propylene oxide and operate using a solution-diffusion mechanism, reducing fouling and maintaining stable separation performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrafiltration membranes are used for membrane separation, then the process can be implemented, but the selectivity and permeate flow become low and unstable
Solution Approach 1:
The patent applies porous nanofiltration membranes with controlled pore sizes of 0.5-5 nm to achieve size-based separation. The porous structure allows propylene oxide molecules to pass through while retaining larger poly(propylene oxide) molecules, providing both stable selectivity and maintained permeate flow without the fouling issues of ultrafiltration membranes
Solution Approach 2:
The patent changes the key parameter of membrane pore size from the larger pores of ultrafiltration membranes to the smaller, controlled pores of nanofiltration membranes (0.5-5 nm). This parameter change enables effective rejection of poly(propylene oxide) while maintaining propylene oxide permeation, resolving the contradiction between selectivity and productivity
2Reliability
If ultrafiltration membranes are used, then membrane separation can be performed, but membrane fouling occurs and rejection rate decreases
Solution Approach 1:
The patent uses nanofiltration membranes with optimized pore sizes (0.5-5 nm) that are small enough to reject poly(propylene oxide) molecules effectively but large enough to allow propylene oxide passage. The controlled porosity prevents fouling by minimizing the interaction between the membrane and contaminants while maintaining high rejection rates
Solution Approach 2:
The patent extracts and removes the harmful poly(propylene oxide) impurities from the propylene oxide stream through the nanofiltration membrane. The membrane selectively retains the harmful high molecular weight compounds while allowing the desired propylene oxide to pass through, achieving both high rejection and fouling resistance
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 use of non-porous or nanofiltration membranes achieves stable and high poly(propylene oxide) rejection rates, minimizing membrane fouling and ensuring consistent permeate quality, enabling the production of high-quality propylene oxide for both moulded and slabstock polyurethane foams.
Implementation Method 1
non-porous or nanofiltration membranes with average pore sizes of 0 to 5 nm, which are resistant to propylene oxide and operate using a solution-diffusion mechanism
Data Source
Figure 1
AI summary
The invention relates to a process for removing poly(propylene oxide) from propylene oxide by membrane separation, wherein a membrane having an average pore size of from 0 to 5 nm is used. In said process, a liquid feed comprising propylene oxide and poly(propylene oxide) may be separated by the membrane into a permeate comprising propylene oxide and either no poly(propylene oxide) or poly(propylene oxide) at a concentration which is lower than the poly(propylene oxide) concentration in the feed, and a retentate comprising propylene oxide and poly(propylene oxide) at a concentration which is higher than the poly(propylene oxide) concentration in the feed.