Silver Catalyst Calcination with Trace Oxygen for Ethylene Oxide
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Solution Overview
Problem
Existing silver catalysts for ethylene oxide production face challenges in achieving high efficiency and selectivity due to limitations in catalyst preparation methods, support materials, and promotional additives, particularly in the calcination process under inert atmospheres without sufficient oxygen.
Innovation Solution
A supported silver catalyst is prepared by impregnating an inert support with a silver-containing compound, an alkali metal, and a transition metal promoter, followed by calcination in a mixture of inert gas and molecular oxygen, optimizing the silver content, alkali metal, and transition metal amounts to enhance catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the support is calcined under an inert atmosphere without oxygen, then organic materials are removed and silver is converted to metallic silver, but catalyst selectivity and activity are insufficient
Solution Approach 1:
The patent changes the atmospheric composition parameter during calcination by introducing a small concentration of oxygen (50-500 ppm) into the inert atmosphere. This parameter modification allows the catalyst to achieve both proper silver reduction and improved selectivity/activity for ethylene oxide production, resolving the contradiction between complete organic removal and catalytic performance.
2Reliability
If air is used for calcination, then oxygen is available for oxidation reactions, but excessive oxygen causes complete combustion instead of selective epoxidation
Solution Approach 1:
The patent applies partial action by introducing only a small, controlled amount of oxygen (50-500 ppm) into the inert atmosphere during calcination. This partial oxygen presence is sufficient to improve catalyst selectivity and activity through controlled oxidation of surface species, but insufficient to cause complete combustion of ethylene, thus resolving the contradiction between achieving selective epoxidation and avoiding harmful complete combustion.
3Productivity
If the silver catalyst is highly active, then ethylene conversion is high, but catalyst life and stability are reduced
Solution Approach 1:
The patent modifies the calcination atmosphere composition parameter to include controlled oxygen (50-500 ppm in inert gas), which creates an optimal catalyst surface structure that achieves high ethylene conversion while maintaining improved catalyst life and stability. This parameter change resolves the contradiction between high productivity and extended catalyst duration.
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 results in improved catalyst selectivity and activity for ethylene oxide production, extending catalyst life and maintaining stability, as demonstrated by increased ethylene oxidation to ethylene oxide conversion.
Implementation Method 1
calcining the impregnated support by heating the impregnated support at a temperature of from 200 °C to 600 °C for a time sufficient to convert the silver in the silver containing compound to metallic silver
Implementation Method 2
the heating being conducted under an atmosphere comprising a combination of an inert gas and from 50 ppm to 500 ppm by volume of a gas of an oxygen containing oxidizing component comprising molecular oxygen
Implementation Method 3
a supported, metal promoted silver catalyst capable of oxidizing an alkene, preferably ethylene, with an oxygen containing gas in the vapor phase to produce alkylene oxide, preferably ethylene oxide
Data Source
Figure 1
AI summary
This invention relates to an improved process for preparing silver catalysts useful for the vapor phase production of ethylene oxide from ethylene and oxygen. An inert support is impregnated with a solution of a catalytically effective amount of a silver containing compound, a promoting amount of an alkali metal containing compound, and a promoting amount of a transition metal containing compound. The impregnated support is calcined by heating at a temperature of from about 200° C to about 600° C to convert the silver in the silver containing compound to metallic silver and to decompose and remove substantially all organic materials. The heating is conducted under an atmosphere comprising a combination of an inert gas and from about 10 ppm to about 5% by volume of a gas of an oxygen containing oxidizing component.