Oxidation Catalyst Noble Metal Leaching PMIDA
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Solution Overview
Problem
Existing catalysts for the oxidation of N-(phosphonomethyl)iminodiacetic acid (PMIDA) to N-(phosphonomethyl)glycine suffer from noble metal leaching and the formation of undesirable by-products, such as formaldehyde, which reduces yield and introduces toxicity.
Innovation Solution
Development of oxidation catalysts comprising a carbon support with a noble metal, such as platinum, and a promoter like iron or cobalt, with controlled metal particle size distribution and composition to minimize leaching and by-product formation, including a process for preparing these catalysts by depositing the noble metal and promoter on the carbon support and heating it in a non-oxidizing environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a noble metal is deposited on the carbon support to catalyze the oxidation reaction, then the catalytic activity is improved, but noble metal leaching increases under acidic conditions
Solution Approach 1:
The patent changes the chemical state of the noble metal from a reduced form to an oxidized form by controlling the preparation conditions (oxidizing atmosphere during calcination). This parameter change transforms the noble metal into a more stable oxidized state that resists leaching under acidic reaction conditions, while maintaining catalytic activity through the redox cycle during the oxidation reaction.
Solution Approach 2:
The patent creates a composite catalyst system consisting of noble metal particles dispersed on a carbon support matrix. The carbon support provides structural stability and acidity control, while the noble metal provides catalytic activity. The synergistic interaction between these two components achieves both high catalytic activity and reduced metal leaching.
2Loss of substance
If activated carbon alone is used as catalyst, then noble metal leaching is eliminated, but formaldehyde by-product formation increases
Solution Approach 1:
The patent merges the advantages of both carbon-based catalysts (low metal leaching) and noble metal catalysts (high selectivity and activity) by depositing a small amount of oxidized noble metal on the carbon support. This combined system eliminates the harmful formaldehyde by-product through the noble metal's ability to catalyze complete oxidation, while the carbon support prevents significant metal leaching.
Solution Approach 2:
The carbon support acts as an intermediary that modulates the reaction environment. It provides a stable matrix that controls the release of oxygen and intermediates, preventing the formation of formaldehyde while allowing the noble metal to function effectively. The carbon support mediates between the noble metal catalyst and the reactants, optimizing the reaction pathway.
3Object-generated harmful factors
If the noble metal is used to oxidize formaldehyde to carbon dioxide and water, then by-product formation is reduced, but noble metal loss to reaction solution increases
Solution Approach 1:
The patent changes the oxidation state of the noble metal from reduced to oxidized form during preparation. This parameter change creates a more stable noble metal species that is less prone to dissolution in the acidic reaction medium, thereby reducing metal loss while maintaining the ability to catalyze formaldehyde oxidation.
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 catalysts exhibit reduced noble metal leaching and lower formation of unwanted by-products, leading to improved yield and stability in the oxidation of PMIDA to N-(phosphonomethyl)glycine, enhancing the efficiency and selectivity of the reaction.
Implementation Method 1
oxidation catalysts comprising a carbon support having deposited thereon a noble metal and optionally one or more promoters... catalyzing the oxidative cleavage of PMIDA substrates
Implementation Method 2
carbon support having deposited thereon a noble metal... metal particles at a surface of the carbon support
Implementation Method 3
heating it in a non-oxidizing environment... removing the oxides from the surface of the carbon catalyst
Data Source
AI summary
This invention relates to the field of heterogeneous catalysis, and more particularly to oxidation catalysts including carbon supports having deposited thereon a noble metal and one or more optional promoters and to methods for their preparation. The invention further relates to the field of heterogeneous catalytic oxidation reactions, including the preparation of secondary amines by the catalytic oxidation of tertiary amines, such as the oxidation of an N-(phosphonomethyl)iminodiacetic acid to produce an N-(phosphonomethyl)glycine product.