Ethylene Oxide Production Scaled Selectivity Optimization
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Solution Overview
Problem
Conventional silver-based catalysts used in ethylene oxide production exhibit limited selectivity and require frequent replacement due to aging, making it challenging to maintain optimal operation, especially when production parameters change.
Innovation Solution
The method employs scaled selectivity values and reaction temperature adjustments to determine and maintain optimal operation by comparing actual selectivity and temperature to reference conditions, allowing for adjustments in reaction temperature and catalyst chloriding effectiveness to maximize ethylene oxide production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silver-based catalysts are used in ethylene oxide production, then the process can operate with simpler catalyst composition, but the selectivity is limited to below 85.7% and frequent catalyst replacement is required
Solution Approach 1:
The patent employs composite catalyst materials comprising silver, rhenium, and at least one further metal (such as caesium, potassium, or lithium) to achieve high selectivity above 85.7%. This composite approach combines multiple elements with complementary properties: silver provides the base catalytic activity, rhenium enhances selectivity, and the alkali/alkaline earth metals fine-tune the catalytic performance, thereby resolving the contradiction between selectivity and composition simplicity.
Solution Approach 2:
The patent changes the chemical composition parameters of the catalyst by introducing specific metal ratios and quantities. The catalyst contains silver at 5-20 wt%, rhenium at 0.1-5 wt%, and further metals at controlled amounts, with these parameter adjustments enabling selectivity to exceed the conventional 85.7% limit while maintaining operational reliability.
2Productivity
If reaction temperature is increased to maintain ethylene oxide production rate during catalyst aging, then production rate can be maintained, but selectivity becomes undesirably low and catalyst lifetime ends
Solution Approach 1:
The patent implements a control system that continuously monitors selectivity and production rate, providing feedback to adjust operating parameters. When catalyst aging causes selectivity to decline, the system detects this change and adjusts the reaction temperature or promoter concentration accordingly, preventing the need to increase temperature to unsafe levels and extending catalyst lifetime while maintaining productivity.
Solution Approach 2:
The patent employs dynamic adjustment of operating conditions based on catalyst age and performance. Rather than using fixed temperature settings, the system dynamically modifies reaction temperature and promoter concentration in response to real-time catalyst state, allowing optimal balance between productivity and selectivity throughout the catalyst's operational life.
3Reliability
If gas phase promoter concentration is increased to maintain selectivity, then selectivity can be maintained at lower temperatures, but activity declines linearly requiring temperature increase or production rate reduction
Solution Approach 1:
The patent changes the promoter concentration parameter within an optimized range (50-500 ppmv) rather than using excessive amounts. This controlled parameter adjustment, combined with the specific catalyst composition containing rhenium and further metals, achieves high selectivity without the linear activity decline associated with conventional catalysts, thereby maintaining both reliability and productivity.
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 continuous optimization of ethylene oxide production, reducing the need for frequent catalyst replacement and maintaining high selectivity even when production parameters change, thereby improving process efficiency and extending catalyst life.
Implementation Method 1
The production of ethylene oxide generally occurs via the catalytic epoxidation of ethylene in the presence of oxygen. Conventional silver-based catalysts used in such processes provide a relatively lower efficiency or 'selectivity'
Data Source
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AI summary
Disclosed herein are methods of using scaled selectivities to assist in determining whether changes to the value of a target ethylene oxide production parameter—such as ethylene oxide production rate—used in the process of epoxidizing ethylene with a high-selectivity catalyst, have caused the process to move away from optimal operation. If the deviation from optimal operation has not worsened, it is generally unnecessary to perform a full optimization study even if the value of a target ethylene oxide production parameter has changed, which reduces or eliminates process disturbances caused by carrying out such studies. Methods are also disclosed which use both scaled selectivities and scaled reaction temperatures. If scaled selectivities reveal that a change in the value of a target ethylene oxide production parameter has moved the process away from optimal operation, scaled reaction temperatures can, under certain conditions, provide an indication of the directions in which the reaction temperature and/or overall catalyst chloriding effectiveness should be changed to move toward optimal operation. If a change in the value of a target ethylene oxide production parameter has improved the scaled selectivity, the scaled reaction temperature may also be used to guide further adjustments which may further improve scaled selectivity.