Ni-Doped Ag Epoxidation Catalyst for Higher Ethylene Oxide Selectivity
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Solution Overview
Problem
Existing alkene epoxidation processes using Ag-based catalysts on low surface area α-Al2O3 suffer from low ethylene oxide selectivity and conversion, necessitating energy-intensive separation and recycle processes, with a need for methods to enhance selectivity and conversion.
Innovation Solution
A heterogeneous catalyst formulation featuring Ni-doped Ag single atom alloy nanoparticles supported on α-Al2O3, which promotes selective oxygen species for ethylene oxide formation, achieving >85% selectivity and high ethylene conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Ag-based catalysts on low surface area α-Al2O3 are used for alkene epoxidation, then the catalyst is simple and cost-effective, but ethylene oxide selectivity and conversion are low
Solution Approach 1:
The patent applies composite materials by combining Ag nanoparticles with Ni dopants and In/Ga promoters to create a bimetallic catalyst system. This composite structure integrates the catalytic activity of Ag with the oxygen activation capabilities of Ni and the promotional effects of In/Ga, achieving superior ethylene oxide selectivity (>85%) and conversion performance compared to monometallic Ag catalysts.
Solution Approach 2:
The patent employs local quality by creating single-atom dispersed Ni dopants within the Ag nanoparticle matrix. This localized distribution of Ni atoms at specific sites within the Ag structure provides targeted catalytic enhancement for oxygen activation and ethylene oxide formation, while maintaining the overall Ag framework for catalytic activity and selectivity.
2Productivity
If higher conversion is achieved, then productivity increases, but unwanted secondary reactions and combustion of EO increase
Solution Approach 1:
The patent applies parameter changes by optimizing the catalytic composition through precise control of Ni:Ag atomic ratios (1:100 to 1:1000) and In/Ga content (0.01-5 wt%). These parameter optimizations modify the catalyst's electronic and geometric properties to favor epoxidation pathways while suppressing combustion reactions, enabling high conversion with maintained selectivity.
Solution Approach 2:
The patent uses In/Ga promoters as intermediary species that mediate between the Ag-Ni catalytic system and the reaction environment. These promoters modify the oxygen species formation and facilitate selective epoxidation while preventing direct combustion pathways, acting as a protective intermediary that maintains selectivity at high conversion 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 Ni-doped Ag catalysts significantly increase ethylene oxide selectivity to >85% while maintaining high conversion, mitigating unwanted secondary reactions and reducing energy consumption.
Implementation Method 1
Ni atoms dispersed in the Ag nanoparticles promote generation of selective oxygen species leading to the formation of ethylene oxide over the undesired product, carbon dioxide
Implementation Method 2
The catalytic oxidation of ethylene by molecular oxygen (O2) is executed in industry using Ag-based catalysts supported on low surface area α-Al2O3
Data Source
AI summary
A composition of matter useful for catalyzing an alkene epoxidation reaction using molecular oxygen (O2) as an oxidant. including a plurality of structures comprising nanostructures or microstructures each comprising a coinage metal: and a plurality of single oxophilic metal atoms. The oxophilic metal is characterized by an oxide formation enthalpy being more exothermic than that of the coinage metal. In one or more examples. the oxophilic atom comprises nickel and the coinage metal comprises silver, and a concentration of the nickel increases selectivity to greater than 85% for the epoxidation reaction CH2═CH2+½O2→(CH2)2O over combustion of ethylene forming carbon dioxide. and for an ethylene conversion of greater than 5%.