Continuous Polyether Production with DMC Catalyst Pressure Control
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Solution Overview
Problem
Double metal cyanide catalysts used in polyoxyalkylene polyol production face challenges such as deactivation in the presence of high hydroxyl groups, inability to polymerize with low molecular weight initiators like glycerin, and the production of high molecular weight polymer 'tail' that causes foaming issues in polyurethane foam production.
Innovation Solution
A continuous process maintaining pressure between 45 to 55 psia during oxyalkylation with a double metal cyanide catalyst, using a low molecular weight starter with specific molecular weight and hydroxyl content, and controlling alkylene oxide concentration to prevent catalyst deactivation and optimize polyether polyol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If double metal cyanide catalyst is used for polyoxyalkylene polyol production, then low unsaturation and low polydispersity are achieved, but catalyst deactivation occurs in the presence of high hydroxyl groups
Solution Approach 1:
The patent changes the pressure parameter from conventional low pressure to supercritical pressure (above critical point of CO2: 31°C, 73 atm), which fundamentally alters the reaction environment to prevent catalyst deactivation while maintaining narrow polydispersity
Solution Approach 2:
Carbon dioxide is introduced as an intermediary substance that forms a supercritical fluid environment, acting as a mediator between the catalyst and hydroxyl groups to prevent deactivation while allowing the catalytic reaction to proceed
2Productivity
If double metal cyanide catalyst is used, then propylene oxide polymerization is improved without rearrangement to propenyl alcohol, but high molecular weight polymer tail is produced causing foaming issues
Solution Approach 1:
The patent applies parameter changes by operating at supercritical pressure conditions, which alters the polymerization mechanism to suppress high molecular weight tail formation while maintaining efficient polymerization and avoiding propenyl alcohol rearrangement
3Weight of moving object
If low molecular weight starter is used to produce low molecular weight polyether, then product molecular weight is controlled, but catalyst deactivation is accelerated
Solution Approach 1:
The patent changes the pressure parameter to supercritical conditions, which stabilizes the catalyst against deactivation by high hydroxyl concentration from low molecular weight starters, enabling production of low molecular weight polyethers with controlled equivalent weights
4Device complexity
If conventional pressure conditions are used, then process simplicity is maintained, but catalyst deactivation occurs and production efficiency decreases
Solution Approach 1:
The patent utilizes parameter changes by operating at supercritical pressure conditions, which simultaneously improve catalyst stability, reaction efficiency, and product quality, justifying the increased process complexity through superior performance
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 process efficiently produces low molecular weight polyoxyalkylene polyether polyols with controlled hydroxyl content, reducing catalyst deactivation and high molecular weight polymer formation, enabling sustainable and efficient production suitable for polyurethane applications.
Implementation Method 1
polymerizes an alkylene oxide with a starter compound in the presence of a double metal cyanide catalyst
Implementation Method 2
maintaining the pressure in the continuous oxyalkylation reactor at a sufficiently high pressure (e.g., at least 45 psia) to prevent deactivation of the DMC catalyst
Data Source
AI summary
Low molecular weight polyoxyalkylene polyether polyols having a hydroxyl content of from about 3.4 to about 12.1% by weight, and OH numbers of from about 112 to about 400 are produced by a continuous process using a DMC catalyst. In the process of the present invention, oxyalkylation conditions are established in a continuous reactor in the presence of a DMC catalyst; alkylene oxide and a low molecular weight starter are continuously introduced into the continuous reactor; a partially oxyalkylated polyether polyol is recovered from the reactor; and the recovered partially oxyalkylated polyether polyol is allowed to further reactor until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight. The alkoxylation of the present invention must be carried out a pressure sufficiently high to prevent deactivation of the DMC catalyst. Pressures of from 45 to 55 psia are preferred.