Palladium-Gold Catalyst Synthesis Using Basic Solution
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Solution Overview
Problem
Existing supported catalysts for vehicle emission control, particularly those containing palladium and gold, require hazardous reducing agents like sodium borohydride and hydrazine for metal particle formation, which pose handling and disposal challenges, and lack effectiveness in treating vehicle emissions containing CO and HC.
Innovation Solution
A method for producing supported palladium-gold catalysts using sodium hydroxide or sodium carbonate to create a basic solution, maintaining pH levels above 7.0, and heating to form palladium and gold metal particles without the need for separate reducing agents, resulting in a catalyst with palladium and gold dispersed within alumina support pores, optimizing catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hazardous reducing agents like sodium borohydride and hydrazine are used for metal particle formation, then palladium and gold metal particles can be formed effectively, but handling and disposal become difficult and costly
Solution Approach 1:
The patent removes the hazardous reducing agent step entirely from the process. Instead of using sodium borohydride or hydrazine to reduce metal ions, the invention uses a basic solution (pH > 7) to directly form palladium and gold metal particles from their salt solutions, extracting the problematic reduction step while maintaining effective catalyst formation.
Solution Approach 2:
The invention replaces expensive and hazardous reducing agents with a simple, inexpensive basic solution (such as sodium hydroxide or ammonia). This basic solution serves as both the pH control medium and the particle formation agent, eliminating the need for special handling and disposal procedures required for traditional reducing agents.
2Quantity of substance
If traditional reducing agents are used, then metal particles can be formed, but special handling and disposal procedures are required which increase production costs
Solution Approach 1:
The basic solution performs multiple functions simultaneously: it maintains the required pH level, facilitates metal particle formation, and eliminates the need for separate reducing agents. This self-service approach reduces production costs by eliminating the need to purchase, handle, and dispose of hazardous reducing agents.
3Ease of manufacture
If pH is maintained above 7.0 during metal salt solution addition, then metal particles form without hazardous reducing agents, but pH control becomes critical during the process
Solution Approach 1:
The patent implements pH monitoring and control during the metal salt solution addition process. By maintaining pH above 7.0 through feedback control, the process ensures effective metal particle formation while preventing premature particle formation or aggregation that could occur at lower pH levels.
4Reliability
If the catalyst uses alumina support with dispersed metal particles, then catalytic activity for CO and HC treatment is achieved, but the complex internal pore system reduces manufacturing efficiency
Solution Approach 1:
The patent performs metal particle formation directly on the alumina support surface during the impregnation process, rather than requiring separate steps to create and populate the complex pore system. This preliminary action of forming particles in situ during support preparation improves manufacturing efficiency while maintaining the dispersed particle structure needed for catalytic 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
This method reduces the need for hazardous materials, lowers production costs, and enhances the catalyst's efficiency in treating engine exhaust emissions by maintaining pH levels during cooling and using acetic acid as a pH adjuster, achieving effective CO and HC conversion.
Implementation Method 1
preparing a mixture of support materials and a solution that is basic and having a pH that is greater than 9.0, adding a palladium salt solution and a gold salt solution, which have been separately prepared, to the mixture while maintaining the pH of the mixture to be greater than 7.0
Implementation Method 2
heating the mixture and maintaining the mixture at 343 K to 369 K above room temperature for a period of time
Implementation Method 3
cooling the mixture and, while cooling, maintaining the pH of the mixture to be between 7.7 and 8.1, by adding, for example, acetic acid
Implementation Method 4
reducing the palladium and gold ions to metal particles in situ and in the presence of the support material using suitable reducing agents
Data Source
AI summary
A supported palladium-gold catalyst is produced under mild conditions using a commonly available base, such as sodium hydroxide (NaOH) or sodium carbonate (Na2CO3). In this method, support materials and a base solution are mixed together and the temperature of the mixture is increased to a temperature above room temperature. Then, palladium salt and gold salt are added to the mixture while maintaining the pH of the mixture to be greater than 7.0 and keeping the mixture at a temperature above room temperature. This is followed by cooling the mixture while adding acetic acid to maintain the pH of the mixture to be within a desired pH range, filtering out the supported palladium-gold particles, washing with a pH buffer solution and calcining.