Supported Metal Catalysts with Segmented Pore Properties
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Solution Overview
Problem
Conventional catalysts for the oxidation of N-(phosphonomethyl)iminodiacetic acid (PMIDA) and other substrates face inefficiencies in metal utilization, leading to excessive noble metal leaching and by-product formation, due to the distribution and size of pores in porous substrates, which affects catalyst performance and activity.
Innovation Solution
The development of catalysts with a particulate carbon support, where a first metal with higher electropositivity is deposited, and a second noble metal is deposited by displacement, forming a core-shell structure or near-monolayer distribution to enhance metal utilization and reduce leaching, using methods that include pore blocking agents to control metal deposition and promote efficient metal usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional catalysts with porous substrates are used, then catalyst surface area is increased, but metal utilization efficiency deteriorates and noble metal leaching increases
Solution Approach 1:
The catalyst structure is segmented into distinct functional zones: hydrophobic regions (pores) for substrate concentration and hydrophilic regions (surface) for metal deposition and catalysis. This segmentation allows the substrate to be concentrated in the pores while the metal catalyst operates efficiently on the surface, resolving the contradiction between surface area and metal utilization.
Solution Approach 2:
Different regions of the catalyst substrate are given different properties: the pore regions are made hydrophobic to concentrate non-polar substrates, while the surface regions are made hydrophilic to attract and deposit metal catalysts. This local differentiation of properties optimizes both substrate access and metal utilization efficiency.
2Area of stationary object
If conventional catalysts with porous substrates are used, then catalyst surface area is increased, but noble metal leaching increases
Solution Approach 1:
The catalyst structure is segmented into distinct functional zones: hydrophobic regions (pores) for substrate concentration and hydrophilic regions (surface) for metal deposition and catalysis. This segmentation allows the substrate to be concentrated in the pores while the metal catalyst operates efficiently on the surface, resolving the contradiction between surface area and metal utilization.
Solution Approach 2:
The patent employs a sacrificial metal layer (e.g., copper or zinc) that is inexpensive and can be readily replaced. This sacrificial layer prevents noble metal leaching by acting as a barrier, and when it does leach, it does so preferentially, protecting the valuable noble metal catalyst from loss.
3Productivity
If conventional catalysts are used, then catalyst activity is maintained, but by-product formation increases
Solution Approach 1:
Different regions of the catalyst substrate are given different properties: the pore regions are made hydrophobic to concentrate non-polar substrates, while the surface regions are made hydrophilic to attract and deposit metal catalysts. This local differentiation of properties optimizes both substrate access and metal utilization efficiency.
Solution Approach 2:
The hydrophobic pore regions act as intermediaries that concentrate the substrate before it reaches the catalytic sites. This pre-concentration in a controlled environment promotes selective oxidation reactions and reduces unwanted side reactions, thereby decreasing by-product formation while maintaining high catalyst activity.
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 approach results in catalysts that are more active and efficient in oxidizing PMIDA and other substrates, with reduced noble metal leaching and by-product formation, achieving improved metal utilization and catalytic performance.
Implementation Method 1
the pore blocking agent having at least one dimension relative to the opening of the pores such that the pore blocking agent is preferentially retained within the pores
Implementation Method 2
a first metal is deposited onto a support (e.g., a porous carbon support) to provide one or more regions of a first metal at the surface of the support
Implementation Method 3
a second metal is deposited at the surface of the one or more regions of the first metal by displacement of the first metal, wherein the electropositivity of the first metal is greater than the electropositivity of the second metal
Implementation Method 4
use of catalysts prepared as detailed herein in catalytic oxidation reactions, such as oxidation of a substrate selected from the group consisting of N-(phosphonomethyl)iminodiacetic acid or a salt thereof, formaldehyde, and/or formic acid
Data Source
AI summary
Generally, the present invention relates to improvements in metal utilization in supported, metal-containing catalysts. For example, the present invention relates to methods for directing and/or controlling metal deposition onto surfaces of porous substrates. The present invention also relates to methods for preparing catalysts in which a first metal is deposited onto a support (e.g., a porous carbon support) to provide one or more regions of a first metal at the surface of the support, and a second metal is deposited at the surface of the one or more regions of the first metal. Generally, the electropositivity of the first metal (e.g., copper or iron) is greater than the electropositivity of the second metal (e.g., a noble metal such as platinum) and the second metal is deposited at the surface of the one or more regions of the first metal by displacement of the first metal. The present invention further relates to treated substrates, catalyst precursor structures and catalysts prepared by these methods. The invention further relates to use of catalysts prepared as detailed herein in catalytic oxidation reactions, such as oxidation of a substrate selected from the group consisting of N-(phosphonomethyl) iminodiacetic acid or a salt thereof, formaldehyde, and/or formic acid.