PEBAX Membrane Catalyst Separation in Alkoxycarbonylation
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Solution Overview
Problem
Existing alkoxycarbonylation processes face challenges in separating homogeneous catalysts from product mixtures due to instability of membrane materials, particularly towards acids, and inadequate retention of reactants like alcohol, leading to complex downstream processing.
Innovation Solution
The process employs an acid-stable OSN membrane with a surface-active layer, allowing for the separation of catalysts and partial retention of reactants, followed by recycling the catalyst into the reaction zone, using a PEEK-based membrane that maintains stability and selectivity over extended periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide or polydimethylsiloxane membranes are used for catalyst separation, then catalyst retention is achieved, but long-term acid stability deteriorates
Solution Approach 1:
The patent changes the material parameter of the membrane from polyimide or polydimethylsiloxane to polyetherblockamide (PEBAX), which fundamentally alters the chemical stability properties while maintaining the separation function. This material substitution resolves the contradiction by providing both catalyst retention and long-term acid stability.
Solution Approach 2:
The invention uses composite membrane structures, specifically PEBAX which combines polyether and polyamide segments, creating a material that exhibits both good catalyst retention and enhanced acid stability. The composite nature of PEBAX allows it to overcome the limitations of single-material membranes.
2Reliability
If conventional membranes are used for catalyst separation, then catalyst is retained in retentate, but reactant retention deteriorates leading to complex downstream processing
Solution Approach 1:
The PEBAX membrane exhibits selective local quality by differentially interacting with different components in the reaction mixture. It shows high retention for catalyst molecules while allowing preferential passage of esters and partial retention of alcohols, creating a multi-functional separation effect that simplifies downstream processing.
Solution Approach 2:
The membrane performs multiple functions simultaneously: catalyst retention, ester enrichment in permeate, and alcohol partial retention in retentate. This multi-functionality eliminates the need for separate downstream processing steps to recover reactants and purify products.
3Productivity
If homogeneous catalysts are used in alkoxycarbonylation, then reaction efficiency is improved, but catalyst separation and recovery becomes difficult
Solution Approach 1:
The patent extracts the homogeneous catalyst from the product mixture using membrane filtration. The membrane selectively retains the catalyst in the retentate while allowing the ester product to pass into the permeate, achieving easy catalyst separation while maintaining the benefits of homogeneous catalysis.
Solution Approach 2:
The system enables catalyst recovery through membrane retention, allowing the expensive homogeneous catalyst to be recycled back into the reaction system. This prevents catalyst loss and maintains high reaction efficiency while simplifying the separation process.
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
This approach effectively recycles catalysts, reduces catalyst losses, and simplifies downstream processing by enriching esters in the permeate and retaining unreacted species, enhancing process efficiency and cost-effectiveness.
Implementation Method 1
carrying out a membrane separation to separate the homogeneous catalyst system from the liquid product mixture, whereby the homogeneous catalyst system and additionally unreacted hydrocarbon and/or unreacted alcohol, preferably unreacted alcohol, are enriched in the retentate and the ester formed is enriched in the permeate
Data Source
AI summary
The invention relates to a process for preparing an ester by alkoxycarbonylation of a C2 to C20 hydrocarbon having at least one multiple bond, preferably having at least one olefinic double bond, in which the homogeneous catalyst system used is separated from the product mixture by means of membrane separation and recycled into the reaction zone. In a development of the present invention, the ester thus formed is converted into another ester by transesterification.