Epoxidation Process Moderator Concentration Control
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Solution Overview
Problem
High selectivity catalysts in ethylene oxide production exhibit instability and shorter service life, requiring manual adjustments of moderator concentrations to maintain optimal selectivity, which can lead to inefficient steam production and increased operational costs due to the need for importing steam, especially in plants with limited utility capacity.
Innovation Solution
Operating the catalyst at selectivities below the maximum by increasing the moderator concentration above the optimal level, resulting in lower catalyst temperatures and improved stability, which enhances average selectivity and steam production over the catalyst's life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If moderator concentration is increased to maintain maximum selectivity, then selectivity is improved, but catalyst temperature decreases leading to reduced steam production and shorter service life
Solution Approach 1:
The patent applies parameter changes by deliberately operating the catalyst at selectivities below the maximum achievable level. This involves changing the operating parameters (selectivity setpoint, moderator concentration, temperature) from their traditional optimal values to sub-optimal values that balance multiple objectives including steam production and catalyst longevity.
Solution Approach 2:
The patent inverts the conventional approach by not maximizing selectivity but rather operating at reduced selectivity levels. Instead of pushing the catalyst to its selectivity maximum, the methodology deliberately operates below this maximum to achieve better overall process performance and catalyst stability.
2Manufacturing precision
If moderator concentration is increased to maintain maximum selectivity, then selectivity is improved, but steam production decreases requiring external steam imports
Solution Approach 1:
The patent changes the operating parameters from maximum selectivity conditions to sub-maximum selectivity conditions, which alters the heat of reaction and consequently increases steam production to meet plant requirements without external imports.
Solution Approach 2:
The patent converts what would traditionally be considered a negative (reduced selectivity) into a benefit by showing that operating below maximum selectivity actually improves overall process performance through increased steam production and better heat balance.
3Manufacturing precision
If manual adjustments of moderator concentration are made to maintain optimal selectivity, then selectivity is maintained, but operational complexity and costs increase
Solution Approach 1:
The patent enables the process to self-regulate by operating in a regime where the catalyst and process naturally maintain stable performance without requiring continuous manual intervention to adjust moderator concentrations for optimal selectivity.
Solution Approach 2:
Instead of continuously adjusting parameters to maintain maximum selectivity, the patent inverts the approach by setting a stable operating point below maximum selectivity that requires minimal adjustment, thereby reducing operational complexity.
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 leads to superior catalyst stability, longer service life, and more consistent steam production, improving overall plant economics and reducing the need for external steam imports by balancing the heat of reaction and steam generation.
Implementation Method 1
Gas phase oxidation of ethylene to form ethylene oxide by contacting a Re-containing silver-based catalyst with a feed that contains at least oxygen, ethylene and a moderator
Implementation Method 2
improved steam production, which improving overall plant economics and reducing the need for external steam imports by balancing the heat of reaction and steam generation
Data Source
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AI summary
A method for the epoxidation of an olefin comprising the steps of reacting a feed gas composition containing an olefin, oxygen, and a moderator having an optimal moderator concentration in the presence of an epoxidation catalyst at a first temperature and having a first selectivity; and increasing the optimal moderator concentration to a second moderator concentration and whereby the first selectivity is lowed to a second selectivity and the first temperature to a second temperature.