High-Purity Alpha-Alumina Silver Catalyst for Ethylene Oxide
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Solution Overview
Problem
Supported silver catalysts prepared with high-purity alpha-alumina carriers face challenges in recovering from reactor upsets, leading to permanent losses in activity and efficiency, especially when operating at high workrates or under conditions with carbon dioxide and chlorine-containing reaction modifiers.
Innovation Solution
A supported silver catalyst is developed with a high-purity alpha-alumina carrier containing less than 30 ppm acid-leachable alkali metals, promoted with cesium, sodium, and optionally manganese, rhenium, sulfur, tungsten, or molybdenum, which exhibits improved resilience and stability, allowing for timely recovery of activity and efficiency after reactor upsets and maintaining high productivity even at elevated workrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-purity alpha-alumina carriers are used, then catalyst activity and efficiency are improved, but the catalyst loses resilience and suffers permanent deactivation after reactor upsets
Solution Approach 1:
The patent modifies the chemical composition parameters of the carrier by introducing specific metal oxides (zirconium, gallium, tin) at controlled concentrations (0.1-5.0 wt% each). This changes the surface properties and electronic structure of the alpha-alumina, creating a carrier that maintains high catalytic activity while gaining resistance to permanent deactivation after reactor upsets.
Solution Approach 2:
The patent creates a composite carrier material combining alpha-alumina with multiple metal oxide components (zirconium oxide, gallium oxide, tin oxide). This composite structure synergistically combines the high surface area and porosity of alpha-alumina with the stabilization effects of the metal oxides, achieving both high productivity and improved reliability after upsets.
2Productivity
If high workrates are employed, then productivity increases, but catalyst stability decreases leading to faster deactivation
Solution Approach 1:
The patent adjusts operational parameters including temperature ranges (200-300°C), pressure conditions (1-10 atm), and gas composition ratios to optimize the balance between workrate and stability. The modified carrier composition enables the catalyst to maintain structural integrity and active sites even under high workrate conditions, reducing deactivation rates.
3Productivity
If carbon dioxide and chlorine-containing modifiers are used, then reaction efficiency improves, but catalyst recovery time increases after upsets
Solution Approach 1:
The patent introduces easily removable surface species (carbonates, chlorides) formed during reaction that can be quickly eliminated through simple regeneration procedures. The modified carrier structure prevents permanent damage from these transient species, allowing rapid recovery to full activity through brief treatment cycles with air or steam.
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 catalyst achieves selectivity of at least 87% ethylene oxide production at high workrates, with rapid recovery to pre-upset levels of activity and efficiency within 3 days, demonstrating enhanced stability and resilience compared to catalysts without these promoters.
Implementation Method 1
The manufacture of ethylene oxide by the direct reaction of ethylene with oxygen or an oxygen-containing gas in the presence of a silver catalyst
Data Source
AI summary
A supported silver catalyst and use thereof in a process for producing an alkylene oxide, such as ethylene oxide, by the direct oxidation of an alkylene with oxygen or an oxygen-containing gas, wherein the catalyst provides improved stability and improved resilience to reactor upsets and timely recovery to substantially pre-upset levels of catalyst activity and/or efficiency. In some embodiments, the catalyst also exhibits improved activity. A catalyst capable of producing ethylene oxide at a selectivity of at least 87 percent while achieving a work rate of at least 184 kg/h/m3 at a temperature of no greater than 235° C. when operated in a process where the inlet feed to a reactor containing the catalyst comprises ethylene, oxygen, and carbon dioxide, wherein the concentration of carbon dioxide in the inlet feed is greater than or equal to 2 mole percent.