Cu-Modified Zeolite Catalyst Segmentation for Methane Oxidation
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Solution Overview
Problem
The selective oxidation of methane to useful products is hindered by a selectivity-conversion limit due to the ease of continued oxidation of partially oxidized CH4-derived products, limiting methane conversion to around 0.01% and decreasing selectivity with increasing conversion.
Innovation Solution
A catalytic composition comprising a Cu-modified zeolite as the first catalyst for oxidizing methane to an intermediate, followed by a second catalyst for a coupling reaction with a co-reagent, where the rate of diffusion of the co-reagent is lower than the intermediate, preventing over-oxidation and facilitating alkylation or etherification reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If methane conversion is increased, then productivity improves, but selectivity deteriorates due to over-oxidation of intermediate products
Solution Approach 1:
The catalytic system is segmented into two distinct catalysts: a first catalyst (Cu-modified zeolite) for selective methane oxidation to intermediates, and a second catalyst for coupling reactions. This segmentation allows each catalyst to perform its specific function optimally, preventing over-oxidation while maintaining high conversion.
Solution Approach 2:
The patent introduces an intermediate species that is rapidly transferred from the first catalyst to the second catalyst. This intermediary mechanism prevents the intermediate from undergoing further oxidation, effectively decoupling conversion from selectivity loss.
Solution Approach 3:
The use of porous zeolite materials with controlled pore sizes and diffusion rates creates a physical environment where intermediates are rapidly transported out of the first catalyst's pores before over-oxidation can occur, while co-reagents are excluded or slowed down.
2Device complexity
If a single catalyst is used for both oxidation and coupling, then device complexity is reduced, but manufacturing precision deteriorates due to inability to control selective oxidation
Solution Approach 1:
The catalytic system is divided into two specialized catalysts with distinct functions: the first catalyst performs selective oxidation while the second performs coupling reactions. This functional segmentation enables precise control over selectivity that a single catalyst cannot achieve.
Solution Approach 2:
The patent employs a composite catalytic system combining two different catalyst materials, each optimized for its specific reaction step. This composite approach leverages the strengths of each material to achieve overall high selectivity and conversion.
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
This approach enhances methane conversion and selectivity to desirable products like toluene, surpassing previous limits by minimizing over-oxidation and maintaining high selectivity even at higher methane conversions, using readily available oxidants at mild conditions.
Implementation Method 1
a first catalyst capable of catalytically oxidizing a reactant to provide an intermediate
Implementation Method 2
a second catalyst capable of a coupling reaction between (a) an intermediate resulting from a reaction of a reactant at the first catalyst, and (b) a co-reagent
Implementation Method 3
a rate of diffusion of the co-reagent within the cages and/or pores of the first catalyst is lower than a rate of diffusion of the intermediate within the cages and/or pores of the first catalyst
Data Source
AI summary
Catalytic compositions and sequential catalytic methods are generally described. In some embodiments, a composition comprises a first catalyst comprising a Cu-modified zeolite, and a second catalyst capable of a coupling reaction between (a) an intermediate resulting from a reaction of a reactant at the first catalyst, and (b) a co-reagent, wherein a rate of diffusion of the co-reagent within one or more cages and/or pores of the first catalyst is lower than a rate of diffusion of the intermediate within the one or more cages and/or pores of the first catalyst.