Silver Catalyst Promoters for Olefin Epoxidation Stability
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Solution Overview
Problem
Conventional silver-based epoxidation catalysts exhibit low selectivity and rapid deactivation in olefin epoxidation processes, leading to inefficient ethylene oxide production and increased operating costs, despite improvements in selectivity and stability being desirable for process efficiency.
Innovation Solution
A catalyst comprising a carrier with silver, a rhenium promoter, and a potassium promoter, where the carrier has low water leachable potassium and carbon dioxide is present in the reactor feed in quantities less than 2 mole percent, enhancing initial selectivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silver-based catalysts are used in olefin epoxidation, then the process is simple and cost-effective, but the selectivity towards olefin oxide is low and catalyst deactivation is rapid
Solution Approach 1:
The patent applies composite materials by combining silver with specific promoters (potassium, rhenium, tungsten, molybdenum, chromium, sulfur, phosphorus, boron) and supporting materials (alumina, silica, zirconia, titania, magnetite, gamma-alumina) to create a catalyst that simultaneously achieves high selectivity and stability. The composite structure allows the silver to maintain its catalytic activity while the promoters and supports prevent deactivation and improve reliability.
Solution Approach 2:
The patent employs parameter changes by optimizing the composition ratios of the catalyst components, specifically controlling the amount of potassium promoter (0.1-10 mmole/kg), rhenium promoter (0.01-5 mmole/kg), and other promoters within specific ranges. These parameter optimizations enable the catalyst to achieve both high selectivity and long-term stability, resolving the contradiction between productivity and reliability.
2Productivity
If highly selective epoxidation catalysts are used to improve selectivity, then olefin oxide production efficiency increases, but reaction temperature must be increased and catalyst deactivation rate increases
Solution Approach 1:
The patent uses parameter changes by carefully controlling the catalyst composition parameters, particularly the amounts of potassium promoter (0.1-10 mmole/kg) and rhenium promoter (0.01-5 mmole/kg), to achieve high selectivity at lower reaction temperatures. This compositional optimization allows the catalyst to maintain high productivity without requiring increased temperature, thereby avoiding the associated catalyst deactivation.
Solution Approach 2:
The patent introduces intermediary substances (promoters and supports) that mediate between the silver catalyst and the reaction conditions. These intermediaries modify the catalyst's properties to achieve high selectivity at lower temperatures, acting as a buffer that prevents direct correlation between high temperature and high selectivity, thus reducing catalyst deactivation rates.
3Productivity
If highly selective epoxidation catalysts are used to improve selectivity, then olefin oxide production efficiency increases, but catalyst deactivation rate increases
Solution Approach 1:
The patent applies composite materials by creating a multi-component catalyst system where silver is combined with specific promoters (potassium, rhenium, tungsten, molybdenum, chromium, sulfur, phosphorus, boron) and supports. This composite structure provides both high selectivity and extended catalyst life, as the promoters and supports work synergistically to maintain catalytic activity over time while preventing deactivation.
Solution Approach 2:
The patent ensures continuity of useful action by designing a catalyst system that maintains high selectivity and activity over extended periods. The promoters and supports are specifically selected to prevent catalyst deactivation, allowing the catalyst to continue producing olefin oxide efficiently throughout its operational life without significant loss of performance.
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 demonstrates improved selectivity, activity, and stability under low carbon dioxide conditions, leading to more efficient and cost-effective ethylene oxide production and extended catalyst life.
Implementation Method 1
In olefin epoxidation, a reactor feed containing an olefin and oxygen is contacted with a catalyst under epoxidation conditions. The olefin is reacted with oxygen to form an olefin oxide.
Implementation Method 2
The olefin is reacted with oxygen to form an olefin oxide.
Implementation Method 3
a catalyst comprising a carrier and, deposited on the carrier, silver, a rhenium promoter, and a potassium promoter
Data Source
AI summary
A process for the epoxidation of an olefin comprising contacting a reactor feed comprising an olefin, oxygen, and carbon dioxide, with a catalyst comprising a carrier and, deposited on the carrier, silver, a rhenium promoter, and a potassium promoter; wherein the carbon dioxide is present in the reactor feed in a quantity of at most 3 mole percent based on the total epoxidation reactor feed;the potassium promoter is deposited on the carrier in a quantity of at least 0.5 mmole/kg, relative to the weight of the catalyst; andthe carrier contains water leachable potassium in a quantity of less than 55 parts per million by weight, relative to the weight of the carrier;a process for preparing a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate, or an alkanolamine.