Membrane-Supported Catalyst Separation in Epoxidation

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Solution Overview

Problem

The separation of homogeneous catalysts from organic reaction mixtures, particularly in the epoxidation of cyclic, unsaturated C12 compounds with hydrogen peroxide, is challenging due to the instability of nanofiltration membranes in organic solvents and the lack of suitable membrane materials for this specific application.

Innovation Solution

A method using membranes with a separating-active layer composed of cross-linked silicone acrylates, polydimethylsiloxane, and/or polyimide for the separation of homogeneous catalyst systems, allowing for the enrichment of catalysts in the retentate, with the option of using composite membranes that include support materials and specific phase transfer reagents like esterquats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional nanofiltration membranes are used for separating homogeneous catalysts from organic reaction mixtures, then catalyst recovery is enabled, but the membrane stability deteriorates in organic solvents

Engineering Contradiction:

Improvemembrane stabilityVSAvoidsuitability for organic solvent applications

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the chemical composition parameters of the membrane material from conventional aqueous-stable polymers to organic-solvent-resistant materials including crosslinked silicone acrylates, polydimethylsiloxane, and polyimide. This parameter change enables the membrane to maintain stability and functionality in organic reaction media while performing catalyst separation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite membrane structures combining multiple materials (crosslinked silicone acrylates, polydimethylsiloxane, and/or polyimide) to achieve both mechanical integrity and chemical resistance in organic solvents. The composite nature allows synergistic properties that neither material alone could provide for this specific application

Inventive Principle:

Principle #40Composite materials

2Reliability

If homogeneous catalysts are used for epoxidation reactions, then catalytic activity is improved, but separation from reaction mixtures becomes difficult

Engineering Contradiction:

Improvecatalytic activityVSAvoidseparation difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent introduces a phase transfer reagent as an intermediary substance that facilitates the transfer of the homogeneous catalyst from the aqueous phase to the organic phase where the epoxidation reaction occurs. This intermediary enables the catalyst to function in the organic phase while maintaining its homogeneous nature, and the membrane can then separate it based on phase distribution

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces conventional mechanical separation methods (centrifugation, filtration) with membrane-based separation that exploits the unique properties of the catalyst system in the organic phase. The membrane separation mechanism substitutes physical mechanical forces with selective permeability based on molecular size and interaction with the membrane material

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables the efficient recovery and reuse of homogeneous catalysts, maintaining catalytic activity, and achieving high retention rates of transition metal catalysts, such as tungsten, molybdenum, and vanadium derivatives, in the retentate, facilitating economical and continuous epoxidation processes.

Implementation Method 1

In the size exclusion mechanism, the retained dissolved components are prevented from penetrating the membrane due to steric effects. The separation therefore depends on the size of the dissolved components and the average pore size of the membrane.

Methodology Applied

Scientific EffectSize exclusion: Molecular Sieve

Implementation Method 2

In the size exclusion mechanism, the retained dissolved components are prevented from penetrating the membrane due to steric effects.

Methodology Applied

Scientific EffectSteric effects:

Implementation Method 3

Extensive research activities have led to the realization that membranes which contain crosslinked silicone acrylates and/or polydimethylsiloxane and/or polyimide as a separating-active layer are suitable for separating such a catalyst system from the reaction mixture

Methodology Applied

Scientific EffectSelective permeability: Semipermeable Membrane

Data Source

PatentEP2946831B1Membrane-supported catalyst separation in the epoxidation of cyclic, unsaturated c12 compounds for example cyclododecene (CDEN)

Publication Date: 2019.02.20 EVONIK OPERATIONS GMBH

Figure 1

AI summary

The present invention relates to a process for separating homogeneous catalyst systems from organic reaction mixtures. It aims to provide a process that can be used in reaction mixtures for the epoxidation of cyclic, unsaturated C12 compounds. This objective is achieved by using a membrane whose separation-active layer comprises cross-linked silicone acrylates and/or polydimethylsiloxane (PDMS) and/or polyimide.