Bimodal Pore Catalyst for Ethylene Epoxidation Selectivity
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Solution Overview
Problem
Existing catalysts for the epoxidation of ethylene to ethylene oxide lack optimal selectivity due to inadequate pore size distribution and surface characteristics, particularly when promoted with rhenium, which affects their performance in the vapor phase oxidation process.
Innovation Solution
A catalyst with a bimodal pore size distribution, featuring a support with a first mode of pores ranging from 0.01 μm to 5 μm and a second mode from 5 μm to 30 μm, combined with a catalytically effective amount of silver and rhenium, and alkali metal promoters, enhances selectivity in the epoxidation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a catalyst with conventional pore size distribution is used, then the catalyst structure is simple and easy to manufacture, but the selectivity in epoxidation is insufficient
Solution Approach 1:
The patent applies porous materials with specifically engineered bimodal pore size distribution (first mode: 0.01-5 μm, second mode: 5-30 μm) to enhance catalyst performance. The dual-mode pore structure optimizes mass transport and reactant access to active sites, directly improving selectivity in epoxidation reactions while maintaining a manageable manufacturing process through controlled support fabrication.
2Manufacturing precision
If rhenium is added as a promoter to improve selectivity, then the catalytic performance is enhanced, but the catalyst composition becomes more complex
Solution Approach 1:
The patent employs composite materials by combining silver with rhenium promoter and alkali metal promoters on a porous support. This composite catalyst structure leverages the synergistic effects of multiple components: silver provides base catalytic activity, rhenium enhances selectivity through electronic and geometric effects, and alkali metals further modulate surface properties. The complex composition is justified by the significant selectivity improvement in epoxidation.
3Manufacturing precision
If the pore size distribution is optimized to improve selectivity, then the epoxidation performance is enhanced, but the manufacturing process becomes more difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling pore size distribution parameters (bimodal distribution with specific diameter ranges: 0.01-5 μm and 5-30 μm). This involves adjusting fabrication parameters such as porogen size, calcination temperature, and support synthesis conditions to achieve the desired pore structure. The systematic control of these parameters enables reproducible manufacturing of high-selectivity catalysts despite the complexity of pore structure engineering.
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 improved selectivity and performance in the epoxidation of ethylene to ethylene oxide, demonstrating enhanced catalytic properties such as selectivity, activity, and yield, by optimizing the pore structure and promoter distribution.
Implementation Method 1
a catalyst useful for the epoxidation of an olefin to an olefin oxide. More particularly, the invention pertains to an improved catalyst useful for the epoxidation of ethylene to ethylene oxide
Implementation Method 2
These catalysts typically comprise a porous refractory support such as alpha alumina, which has on its surface a catalytic amount of silver
Data Source
AI summary
The invention pertains to a catalyst useful for the epoxidation of an olefin. More particularly, the invention pertains to an improved catalyst useful for the epoxidation of ethylene to ethylene oxide. The catalyst has improved selectivity in the epoxidation process. The catalyst comprises a solid support having a surface, which has a first mode of pores which have a diameter ranging from about 0.01 μm to about 5 μm and having a differential pore volume peak in the range of from about 0.01 μm to about 5 μm. The surface then has a second mode of pores, different from the first mode of pores, which second mode of pores have a diameter ranging from about 1 μm to about 20 μm and have a differential pore volume peak in the range of from about 1 μm to about 20 μm. On the bimodal pore surface is a catalytically effective amount of silver or a silver-containing compound, a promoting amount of rhenium or a rhenium-containing compound, and a promoting amount of one or more alkali metals or alkali-metal-containing compounds.