High-Entropy Oxide Copper Catalysts for Stable Selective Hydrogenation
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Solution Overview
Problem
Copper-based catalysts for hydrogenation of carbon-carbon triple bonds suffer from low thermal stability and aggregation due to low Tamman temperature and weak metal-support interaction, posing challenges in exothermic reactions, especially in ethylene production processes where acetylene poisoning affects catalyst performance.
Innovation Solution
A Cu-Mx/HEOs catalyst is developed, where Cu is the active component and M is a reducible auxiliary metal, supported by high-entropy oxides (HEOs) with controlled reduction conditions, synthesized via a nucleation/crystallization method to enhance structural stability and dispersibility, utilizing layered double hydroxides (LDHs) as precursors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper nanoparticles are used as catalyst, then hydrogenation activity and olefin selectivity are improved, but thermal stability deteriorates due to low Tamman temperature causing aggregation and growth
Solution Approach 1:
The patent creates a composite material system where copper nanoparticles are supported on high-entropy oxides (HEOs). The HEOs consist of multiple metal elements (at least three different metals) that form a stable oxide matrix. This composite structure allows the copper to maintain its catalytic activity while the high-entropy oxide support prevents copper aggregation through strong metal-support interaction and entropy-stabilized lattice structure, thereby resolving the contradiction between catalytic performance and thermal stability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the support material by using high-entropy oxides with specific compositional ratios (at least 30 at% oxide content). The high configurational entropy of the multi-element oxide system raises the Tamman temperature and enhances structural stability. By adjusting the metal composition ratios and oxide content parameters, the catalyst achieves both high copper dispersion for activity and stable support structure for thermal resistance.
2Productivity
If copper-based catalyst is used for exothermic hydrogenation reaction, then hydrogenation efficiency is improved, but catalyst stability deteriorates under high reaction temperatures
Solution Approach 1:
The high-entropy oxide acts as an intermediary between the copper active sites and the reaction environment. It mediates the thermal stress and chemical environment, protecting the copper nanoparticles from sintering and deactivation. The HEO support provides a thermally stable platform that facilitates heat dissipation during exothermic reactions while maintaining copper dispersion, thus enabling high hydrogenation efficiency without sacrificing catalyst stability under harsh reaction conditions.
3Reliability
If copper nanoparticles are dispersed to enhance activity, then catalytic performance is improved, but resistance to aggregation deteriorates due to weak metal-support interaction
Solution Approach 1:
The high-entropy oxide support possesses a porous structure with high surface area and controlled pore distribution. This porous architecture provides numerous anchoring sites for copper nanoparticles, enhancing dispersion and preventing aggregation. The porous structure also facilitates mass transfer and heat dissipation, maintaining high catalytic performance while the confined pore spaces physically constrain copper particle growth, thereby simultaneously achieving high activity and aggregation resistance.
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 catalyst exhibits excellent thermal stability and long-term performance in selective hydrogenation of carbon-carbon triple bonds, maintaining high acetylene conversion and selectivity under harsh conditions.
Implementation Method 1
Entropy-driven structural stability can improve catalyst long-term performance, and the unique hysteresis effect of high-entropy materials can slow down or prevent the aggregation of catalytic active metals
Implementation Method 2
where metals are uniformly dispersed within the layers and can easily convert to oxides at low temperatures
Implementation Method 3
Copper with only one electron in its 4 s orbital exhibits certain hydrogenation activity and excellent selectivity for olefin
Implementation Method 4
The phenomenon of strong metal-support interaction (SMSI) occurs when the surface of supported metal catalysts undergoes a classic metal-carrier interaction, the carrier species migrate to the surface of the metal nanoparticles to wrap them and inhibit their aggregation and growth
Data Source
AI summary
Cu-based catalysts with excellent thermal stability for selective hydrogenation and a preparation method thereof are provided. The method includes: first, six mixed metal salts are instantaneously nucleated in an alkaline solution by the nucleation/crystallization isolation method, to prepare high-entropy composite metal hydroxides (H-LDHs) with uniform element distribution and similar metal proportions. Furthermore, well-crystallized high-entropy oxides (HEOs) are obtained based on the structural topology characteristics of H-LDHs, and a series of Cu-Mx/HEOs catalysts with flexible adjustable catalytic microzone geometries and electronic structures are obtained using the HEOs as precursors.