Pt Core Au Shell Bimetallic Catalyst for Acetylene Hydrochlorination
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Solution Overview
Problem
The existing catalysts for hydrochlorination of acetylene, such as carbon-supported Au catalysts, undergo rapid agglomeration and loss of surface sites in the presence of HCl, leading to a significant decrease in catalytic activity, making the process less attractive due to sintering issues.
Innovation Solution
A supported, bimetallic catalyst system is developed with a core metal having a higher surface free energy than the shell metal, where the shell metal remains resistant to agglomeration by staying on the core metal, maintaining high catalytic activity through metal-metal interactions and electroless deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon-supported Au catalysts are used for hydrochlorination of acetylene, then high activity and selectivity are achieved, but rapid agglomeration occurs in the presence of HCl leading to loss of surface sites and decrease in catalytic activity
Solution Approach 1:
The patent uses a core-shell bimetallic structure where a Pt core is coated with a Au shell. This composite structure combines the high catalytic activity of Au for acetylene hydrochlorination with the structural stability of Pt, preventing Au particle agglomeration while maintaining excellent catalytic performance and selectivity.
2Area of stationary object
If Au particles are maintained at small size (2 nm) for high surface area, then catalytic activity is maximized, but exposure to HCl causes sintering to larger particles (>20 nm) reducing surface area by 90%
Solution Approach 1:
The patent employs a thin Au shell (2-5 nm thick) deposited on the Pt core. This thin film structure maintains a large surface area for catalysis while the underlying Pt core provides structural support that prevents sintering and agglomeration during HCl exposure, ensuring long-term stability.
3Manufacturing precision
If HgCl2/C catalyst is used for direct hydrochlorination of acetylene, then very high selectivity (>99%) is achieved, but the catalyst undergoes reduction to Hg metal and volatilizes into the environment
Solution Approach 1:
The patent replaces the toxic HgCl2 catalyst with a Pt-core Au-shell catalyst that is environmentally friendly. While Hg catalysts provide high selectivity, they are short-lived and polluting; the bimetallic catalyst maintains high selectivity over extended periods without generating harmful emissions, effectively substituting a disposable toxic catalyst with a durable clean alternative.
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 bimetallic catalyst system maintains high catalytic activity and selectivity for hydrochlorination of acetylene, preventing sintering and extending the process's economic viability by ensuring the shell metal remains on the core metal, thereby maintaining the low surface free energy and activity over time.
Implementation Method 1
metal-metal interactions and electroless deposition techniques
Data Source
AI summary
Supported, bimetallic catalyst systems are provided. The supported, bimetallic catalyst system can include a support defining a surface; a core metal positioned on the surface of the support; and a shell metal positioned on the core metal to form a core-shell particle on the surface of the support. The core metal has a surface free energy that is higher than a surface free energy of the shell metal. Methods are also provided for the formation of such supported, bimetallic catalyst systems, as well as the use of such supported, bimetallic catalyst systems in chemical processes.