Semi-Batch Polyol Production via DMC Catalyst Activation
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Solution Overview
Problem
The production of low molecular weight polyoxyalkylene polyols using DMC catalysts faces challenges such as catalyst deactivation, especially with high hydroxyl group concentrations and low molecular weight initiators like glycerin, leading to inefficiencies and high molecular weight polymer formation, which complicates the foaming process and increases production costs.
Innovation Solution
A semi-batch process involving a mixture of double metal cyanide catalyst and initial starter, activated with a propylene oxide and ethylene oxide block, followed by continuous introduction of starters and additional alkylene oxide blocks, with a space time yield of greater than or equal to 250 kg/m³, to enhance catalyst activity and maintain reaction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalyst concentration is increased to prevent deactivation, then catalyst activity is improved, but production cost increases
Solution Approach 1:
The patent applies preliminary action by adding a base catalyst before the DMC catalyst in a sequential addition process. The base catalyst is introduced first to activate the DMC catalyst, which then performs the main oxyalkylation reaction. This preliminary activation step ensures the DMC catalyst remains active throughout the reaction, preventing deactivation without requiring excessive catalyst concentrations, thus resolving the contradiction between maintaining catalyst activity and reducing catalyst cost.
2Productivity
If reaction temperature is increased to improve reaction rate, then productivity is improved, but color formation and negative effects increase
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst system from conventional base catalysts to DMC catalysts, which fundamentally changes the reaction conditions. This catalyst change allows the reaction to proceed at lower temperatures (typically 80-150°C) while maintaining high reaction rates and productivity, thereby avoiding color formation and other temperature-related harmful effects.
3Reliability
If high molecular weight tail is produced, then catalyst activity is maintained, but foaming process difficulty increases
Solution Approach 1:
The patent applies the taking out principle by selectively removing or avoiding the formation of high molecular weight tail through optimized reaction conditions and catalyst selection. By using DMC catalysts with controlled activity and optimizing the oxyalkylation process parameters, the patent prevents the formation of excessive high molecular weight polymers that would complicate the foaming process, while still maintaining sufficient catalyst activity for efficient production.
4Weight of moving object
If starter concentration is increased to achieve low molecular weight products, then product molecular weight is reduced, but catalyst deactivation increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a base catalyst as an intermediary substance that activates the DMC catalyst before the main reaction. This intermediary activation step allows the system to handle high concentrations of starter (for low molecular weight products) without causing immediate catalyst deactivation, as the DMC catalyst is already activated and protected by the base catalyst presence.
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 accelerates catalyst activation, maintains catalyst activity, and reduces the need for special raw material handling, such as ultra-low water levels, while producing polyols with hydroxyl numbers ranging from 200 to 500, thus improving the efficiency and cost-effectiveness of low molecular weight polyoxyalkylene polyol production.
Implementation Method 1
a semi-batch process for the production of low molecular weight polyoxyalkylene polyols. This semi-batch process oxyalkylates one or more starters in the presence of a DMC catalyst
Data Source
AI summary
This invention relates to a semi-batch process for producing low molecular weight polyoxyalkylene polyols. These polyoxyalkylene polyols are characterized by hydroxyl numbers of from 200 to 500. In accordance with the invention, the first alkylene oxide block used to activate the DMC catalyst comprises from 50% to 100% by weight of propylene oxide and from 0% to 50% by weight of ethylene oxide; and the second alkylene oxide block comprises from 50% to 100% by weight of propylene oxide and from 0% to 50% by weight of ethylene oxide. A continuously added starter is present. Optionally, a third alkylene oxide block can be added. The addition of the second alkylene oxide block and of the third alkylene oxide block when present is completed with a space time yield of greater than or equal to 250 kg/m3/hr.