Eggshell Pd-Ag Bimetallic Catalyst for Selective Hydrogenation
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Solution Overview
Problem
Existing catalysts used for selective hydrogenation of unsaturated hydrocarbons, such as acetylene and ethylene, suffer from unsatisfactory durability and selectivity, particularly when employed in gaseous phase hydrogenation processes, leading to reduced catalyst activity and polymer quality issues.
Innovation Solution
A method for producing supported metal catalysts involves applying a reducing agent like hydrazine or formaldehyde to a catalyst support, followed by impregnation with transition metals like Pd, Pt, Cu, or Ag, and subsequent calcination, resulting in a catalyst with a strong interaction between metals, enhancing durability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Pd-Al2O3 catalysts are used for selective hydrogenation, then selectivity is improved, but durability is not satisfactory
Solution Approach 1:
The patent applies local quality by creating an eggshell distribution of Pd and Ag metals where at least 90% of the metals are concentrated in an outer shell region with a maximum depth of 200 μm from the catalyst surface. This localized metal distribution optimizes both selectivity for acetylene hydrogenation and durability by preventing metal migration and sintering in the bulk catalyst, resolving the contradiction between selectivity and durability.
Solution Approach 2:
The patent uses composite materials by combining Pd with Ag to form a bimetallic catalyst system. The specific composition requires at least 90% of Pd and Ag to be located in the outer shell region, with the metals forming an alloy structure. This composite approach enhances both selectivity for selective acetylene hydrogenation and durability through synergistic effects and reduced metal sintering.
2Ease of manufacture
If nickel sulfide catalysts are used, then cost is reduced, but activity at high temperatures is low leading to increased polymer formation
Solution Approach 1:
The patent changes the chemical composition parameters by transitioning from nickel sulfide to a Pd-Ag bimetallic system with specific compositional ratios and spatial distribution. The eggshell distribution with at least 90% of metals in the outer 200 μm shell, combined with the synergistic Pd-Ag alloy structure, dramatically enhances high-temperature activity for acetylene hydrogenation while maintaining cost-effectiveness through optimized metal loading.
3Duration of action of stationary object
If Pd penetration depth is increased, then durability is improved, but selectivity for acetylene hydrogenation decreases
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through eggshell distribution, where at least 90% of Pd and Ag metals are concentrated in an outer shell region with a maximum depth of 200 μm from the catalyst surface. This localized metal placement ensures high selectivity for acetylene hydrogenation at the surface while the overall catalyst structure provides durability, avoiding the need for deep metal penetration into the catalyst bulk.
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 resulting catalyst exhibits high durability and selectivity, allowing for repeated hydrogenation cycles with increased cycle times and reduced formation of by-products like green oil, thereby improving the efficiency of selective hydrogenation processes.
Implementation Method 1
the reducing agent is a compound that is capable of reducing the transition metal from the second liquid medium
Implementation Method 2
selective hydrogenation wherein these compounds are hydrogenated
Implementation Method 3
Pd-catalysts based on aluminium oxides and silicium oxides for selective hydrogenation processes
Data Source
AI summary
The present invention relates to a method for producing supported metal catalysts, catalysts obtainable thereby and their use in a hydrogenation process.