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Heterogeneous Gold Catalysis

Heterogeneous gold catalysis is a gold reaction with other metal oxide substrates. It is the procedure of using gold as a catalyst in chemical reactions. The following article illustrates it in detail.

Heterogeneous Gold Catalysis is the scientific method of using gold as catalysts in chemical reactions. Catalysts are chemicals that facilitate the chemical reaction’s whole procedure.

 It plays an intermediate part in any reaction. However, it does not undergo the reaction, nor does it affect the product of the reaction. It provides a suitable environment for the reaction so that the reaction can occur smoothly. 

Heterogeneous Gold Catalysis is mainly used to complete the reactions of metal oxide substrates. Various procedures and reactions like activation of hydrogen, hydrogenation, and water shift use gold as catalysis to facilitate their occurrence and support them in obtaining the final product.

A brief history of gold catalysis

The primary advances in gold catalysis happened in 1965 when the German firm Knapsack derived it by oxidative acetylation of ethylene. Bond and Sermon hydrogenated 1-pentene in 1973, utilising gold impetuses. Hutchins and partners showed how upheld gold could be utilised to combine hydrogen peroxide (H₂O₂) straight by responding hydrogen with oxygen under unfavourable circumstances. So the modification in Gold impetus results in the discovery of heterogeneous gold catalysis.

Definition of heterogeneous gold catalyst

The process of gold catalysis that is aided by metal oxide substrates is referred to as heterogeneous gold catalysis. 

Synthesis of heterogeneous gold catalysis

The size of AuNPs is thought to be a crucial component in developing efficient catalysts for various catalytic applications. Before selecting the optimal gold catalyst composition, it is ordinarily necessary to determine if the size of gold particles affects the reaction’s progress. Along with this, selecting the appropriate metal oxide substrates for support is very necessary. As a result, technique selection is unquestionably critical for creating high-performance gold catalysts. Metal nanoparticles may be synthesised in several ways, including physical, chemical, biological, and hybrid processes. 

The role of adsorption in heterogeneous catalysis 

According to the traditional role of adsorption in heterogeneous gold catalysis, reactants in their gaseous or dissolved form in any solution get adsorbed on the solid surface of a suitable catalyst. As the concentration of reactants on the catalyst surface grows, the availability and likelihood of a reaction between two reactants increases and, therefore, the rate of the reaction increases. Some energy is released when the reactants cling to the catalyst’s surface after an exothermic reaction. This heat of combination is used to accelerate the reaction between the two species. According to the intermediate compound hypothesis of heterogeneous gold catalysis, the intended reaction is accomplished by creating an intermediate compound and breaking it into the desired products. After the reaction is complete, the catalyst is regenerated. Thus, adsorption in heterogeneous catalysis is crucial in the chemical history of catalysis.

Methods of heterogeneous gold catalysis

In chemical research, there are four methods for creating heterogeneous gold catalysts. Each has distinct advantages and disadvantages. Deposition-precipitation, co-precipitation, impregnation, and reduction-deposition are the most frequently used procedures for preparing metal oxide-support AuNPs. The following procedures are used to create heterogeneous gold catalysts: 

  • Deposition and participation
  • Co-precipitation
  • Impregnation
  • Reduction deposition

Applications of heterogeneous gold catalysis 

Gold catalysis is widely used in industries and factories. Here are some applications:

  • Carbon monoxide oxidation: Gold works as a catalyst in the oxidation of carbon monoxide. In the catalysis of carbon monoxide, carbon monoxide reacts with oxygen to create carbon dioxide. In this reaction, the gold cations help in increasing the activation energy of atoms present in both the reactants, helping the reaction complete faster. 
  • Water-gas shift: One of the most popular methods used to produce H₂ dihydrogen. In this procedure, water reacts with carbon monoxide to form dihydrogen. Like carbon monoxide oxidation, gold helps increase the activation energy of reactants, and the reaction occurs at faster rates. 
  • Gold catalyst is also used in the formation of hydrogen peroxide. 
  • It also facilitates the oxidation of glucose, creating gluconic acid as a result.
  • It also facilitates the decomposition of dioxins, in which it acts as a reducing agent. 
  • It is also used in the hydrogenation of alkynes and dines to form mono-olefins. 
  • Gold catalyst is also used in the production of vinyl acetate.

Conclusion

The rational design of heterogeneous gold catalysis based on a precise atomic-level understanding of surface processes generates considerable scientific interest in heterogeneous catalysis. Further research may focus on creating bi- or multi-functional suitable catalysts, which might significantly impact current applications or open the door to new ones. 

Additionally, analytical techniques to sequence various capabilities will need to be developed to build innovative, attractive, eco-friendly nanostructured gold catalysts for various applications. The introduction of Heterogeneous Gold Catalysis has positively impacted the overall studies of chemistry. However, it is used for supporting various reactions like hydrogenation and water shift.

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