Silver Catalyst Selectivity via Fluoride Carrier and CO2 Control
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Solution Overview
Problem
Silver-based catalysts used in olefin epoxidation processes face challenges in maintaining high selectivity and stability over time, requiring increased reaction temperatures that can lead to equipment limitations and reduced product yield.
Innovation Solution
A process using a catalyst with a silver component and a high-selectivity dopant, such as rhenium, deposited on a fluoride-mineralized carrier, which maintains high selectivity and stability by controlling carbon dioxide levels in the feed below 2 mole-%, achieving selectivity greater than 85% and extending catalyst life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reaction temperature is increased to maintain olefin oxide production as the catalyst ages, then the productivity is maintained, but the selectivity to the desired olefin oxide decreases
Solution Approach 1:
The patent modifies the chemical composition parameters of the catalyst by incorporating specific dopants (rhenium at 0.1-3.0 mmole/kg, alkali metals at 0.01-1.0 mmole/kg) and using a fluoride-mineralized carrier, which changes the catalyst's intrinsic properties to maintain high selectivity across a wider temperature range and extended operational period
Solution Approach 2:
The patent creates a composite catalyst system combining silver (0.5-5.0 mmole/kg) with multiple dopant elements (rhenium, alkali metals) on a fluoride-mineralized alumina carrier, where the synergistic interaction between components maintains both activity and selectivity during aging
2Productivity
If the reaction temperature is increased to maintain olefin oxide production, then the productivity is maintained, but the equipment tolerance is exceeded and catalyst stability decreases
Solution Approach 1:
The patent optimizes the catalyst's chemical composition to enhance its thermal stability and resistance to deactivation, allowing the process to operate at lower temperatures for extended periods without exceeding equipment tolerance limits
Solution Approach 2:
The patent uses dopant levels that exceed conventional amounts (particularly rhenium up to 3.0 mmole/kg and fluoride treatment) to create an over-engineered catalyst with enhanced stability margins, allowing operation well within equipment temperature limits while maintaining productivity
3Loss of substance
If carbon dioxide is recovered and recycled in the feed, then the loss of substance is reduced, but the carbon dioxide accumulates and reduces catalyst performance
Solution Approach 1:
The patent identifies carbon dioxide concentration as a critical parameter affecting catalyst performance and establishes optimal ranges (0.1-5.0% by volume) that balance CO2 recycling benefits with catalyst selectivity maintenance, preventing accumulation to harmful levels
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
The process achieves high initial peak selectivity and improved stability, allowing for longer catalyst use and increased olefin oxide production with selectivity maintained above 90% even after significant cumulative production.
Implementation Method 1
The catalyst comprises silver, usually with one or more additional elements deposited therewith, on a carrier, typically an alpha-alumina carrier. The olefin is reacted with oxygen to form an olefin oxide.
Implementation Method 2
a catalyst comprising a silver component and a high-selectivity dopant deposited on a fluoride-mineralized carrier
Implementation Method 3
The olefin oxide may be reacted with water to form a 1,2-diol
Implementation Method 4
with an alcohol to form a 1,2-diol ether, or with an amine to form an alkanolamine
Data Source
AI summary
A process is provided for the epoxidation of an olefin comprising the steps of: contacting a feed comprising an olefin and oxygen with a catalyst comprising a silver component and a high-selectivity dopant deposited on a fluoride-mineralized carrier; and producing a product mix comprising an olefin oxide, wherein the concentration of carbon dioxide in the feed is less than about 2 mole-%, relative to the total feed.