Polycarbonate Ether Polyol Synthesis via Segmented DMC Catalyst Activation
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Solution Overview
Problem
Existing methods for preparing polycarbonate ether polyols and high molecular weight polyether carbonates face limitations, including low carbon dioxide content, high pressure requirements, and restricted use of lower molecular weight starters, which increase operational costs and complexity, and are not suitable for industrial-scale production under safe conditions.
Innovation Solution
A method involving a double metal cyanide (DMC) catalyst system that allows for the continuous or semi-continuous addition of starters and epoxides, enabling the incorporation of carbon dioxide from the beginning of the reaction, thereby increasing carbon dioxide content and allowing the production of a wide range of molecular weight polyols without the need for pre-activation of the catalyst, reducing pressure requirements and operational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a DMC catalyst is used to prepare polyether carbonate polyols, then the reaction can proceed with epoxide and carbon dioxide, but the carbon dioxide content is low and high pressures (40-50 bar) are required
Solution Approach 1:
The patent divides the reaction process into two distinct stages: (1) catalyst activation stage where only epoxide is added to activate the DMC catalyst without CO2 incorporation, and (2) polymerization stage where both epoxide and CO2 are added to build the polyol with high CO2 content. This segmentation allows the catalyst to be fully activated before CO2 incorporation begins, enabling high CO2 content at lower pressures
Solution Approach 2:
The patent performs preliminary catalyst activation by adding epoxide to the DMC catalyst before introducing carbon dioxide. This preliminary action ensures the catalyst is in its optimal activated state, which enables subsequent CO2 incorporation to proceed efficiently at lower pressures while achieving high CO2 content in the final product
2Reliability
If an initial amount of epoxide is added to pre-activate the catalyst, then the reaction can proceed safely, but the carbon dioxide content is inherently lowered because the first segment contains only polyether linkages
Solution Approach 1:
The patent extracts the catalyst activation function from the CO2 incorporation process by dedicating the first stage solely to activation using epoxide, then separately introducing CO2 in the second stage. This separation ensures that the initial safety-driven activation step does not compromise the final CO2 content, as CO2 is systematically incorporated throughout the second stage to achieve the desired high CO2 content in the final polyol
3Reliability
If higher equivalent weight starters are used, then the catalyst activation is not inhibited, but the method is limited to higher molecular weights and cannot incorporate significant CO2 into lower molecular weight polyols
Solution Approach 1:
The patent implements dynamic control of reactant addition rates and sequences during the two-stage process. By controlling the rate of epoxide and CO2 addition in the second stage, the system can accommodate a wide range of starter molecular weights, allowing both low and high molecular weight polyols to be produced with high CO2 content, thus providing versatility across different molecular weight ranges
4Stress or pressure
If a batch method with all epoxide entered at the start is used, then low pressure operation (5-10 bar) is possible with high CO2 content, but the highly exothermic reaction cannot be safely controlled
Solution Approach 1:
The patent segments the reactant addition process into controlled stages:第一阶段 activates the catalyst with epoxide alone, and第二阶段 systematically adds both epoxide and CO2. This segmentation prevents the simultaneous presence of all reactants that would cause runaway exothermic reactions, while still achieving the low pressure (5-10 bar) and high CO2 content benefits of the batch method
Solution Approach 2:
The patent maintains continuous controlled addition of epoxide and CO2 during the second stage, ensuring the reaction proceeds at a controlled rate that manages exothermic heat generation. This continuous controlled action allows the system to operate at low pressures while safely managing the exothermic nature of the reaction and achieving high CO2 content
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 enables the production of polycarbonate ether polyols with higher carbon dioxide content under safer, lower pressure conditions, facilitating the use of lower molecular weight starters and expanding the range of molecular weights achievable, thus improving efficiency and scalability in industrial production.
Implementation Method 1
Polycarbonate ether polyols can be made by the catalytic addition of epoxides and carbon dioxide to a starter (compounds with H-functionality). One method of preparing polyether carbonate polyols is by using a double metal cyanide (DMC) catalyst.
Implementation Method 2
The remaining epoxide and carbon dioxide is then metered into the reaction in slowly to control the highly exothermic reaction and enable safe operation.
Data Source
AI summary
The method of preparing the polycarbonate ether polyol or high molecular weight polyether carbonate using controlled addition of materials during polymerisation includes the steps of:mixing catalyst of formula(I), double metal cyanide (DMC) catalyst and optionally carbon dioxide and/or solvent with epoxide and optionally starter compound and/or carbon dioxide; ormixing DMC catalyst and optionally starter compound, carbon dioxide and/or solvent with epoxide and optionally carbon dioxide and/or solvent; ormixing epoxide, catalyst of formula(I), starter compound and carbon dioxide and optionally solvent; ormixing catalyst of formula (I), DMC catalyst and optionally starter compound, epoxide, carbon dioxide and/or solvent to form in each case a mixture (α); andadding one or more of starter compound, epoxide, carbon dioxide, catalyst of formula(I), DMC catalyst and/or solvent to mixture (α) to form mixture (β) comprising starter compound, epoxide, carbon dioxide, catalyst of formula(I), DMC catalyst and optionally solvent,