The Advantages and Disadvantages of Homogeneous Catalysis

Different chemical reactions occur when two or more reactants interact in controlled environments. The use of catalysts is one of the essential parts of multiple chemical reactions to increase the yield and rate of reaction. Homogeneous catalysis is one such exclusive type of chemical reaction. The catalyst and different reactants remain in the same phase in such reactions.

Let us discuss homogeneous catalysis and its examples. First, it is crucial to learn about homogeneous catalysis reactions to understand their mechanism. 

What is homogeneous catalysis?

Catalysts are compounds that, when added to any chemical reaction, increase the reaction rate by helping the reactants quickly cross the activation energy levels. The amount of catalyst does not change in the process; hence, it is not consumed. Out of all the catalysts available for chemical reactions, homogeneous catalysts have unique applications. 

It is essential to understand the mechanism of the chemical reaction catalysis, which is given by:

1. The reactant molecules are introduced and diffused on the catalytic surface.
2. The next step involves absorbing the reactant molecules on the catalytic surface.
3. The intermediates are formed on the catalytic surface due to the chemical reaction in the second step.
4. The desorption of the products from the catalytic surface takes place.
5. The final products are formed by the diffusion of product molecules away from the catalytic surface.

The homogeneous catalysts exist in the same phase as the phase of the reactants. These can be gaseous or liquid state catalysts according to the reaction needs. Some widely used homogeneous catalysts include acid, enzymatic, and organometallic catalysts. The process involving these catalysts is termed homogeneous catalysis. 

Homogeneous catalysis example

Thus, the chemical reaction in which the reactants and the catalysts are in the same phase (essentially gaseous or liquid) is called homogeneous catalysis.

Consider the oxidation of SO2 to SO3 with O2. Here, NO is the homogeneous catalyst.

2SO2(g)   +   O2(g)  → 2SO3(g)

Some other quick examples of homogeneous catalysis include:

1. Acid catalysis: In this reaction, acid is dissolved in water to release protons. These protons fasten the process of reaction like the hydrolysis of esters. It is not possible to hydrolyze the ester without acids.
2. Organocatalysis: The reactions like transfer hydrogenation and hydroformylation are possible with the inclusion of organometallic compounds.
3. Enzyme catalysis: In these reactions, an enzyme is used as the homogeneous catalyst to increase the rate of reaction.

Advantages of homogeneous catalysis

Some of the key advantages of the homogeneous catalysis are:

1.     It offers high levels of rational manipulation. These chemical reactions are easy to characterise.
2.     It becomes easy to manage the exothermic homogeneous catalysis reactions. The heat thus produced is released by the catalysts into the solvent directly.
3.     These reactions are highly selective compared to heterogeneous catalysis.
4.     These reactions have high catalytic activities as reactants can quickly access the homogeneous catalysts.

Disadvantages of homogeneous catalysis

Like any other chemical reaction, homogeneous catalysis also has certain limitations. The possible disadvantages of this reaction include:

1. The catalysts used in the homogeneous catalysis reaction have low thermal stability.
2. The operating temperature for these catalysts may increase up to 200 degrees Celsius for pincer-based catalysts.
3. The separation of the homogeneous catalysts from the products is a challenging process.
4. In the homogeneous catalysis reaction, catalysts may not get completely separated from the final product.
5. Distillation is required to separate the organic products from the homogeneous catalysts.

Conclusion

The reagents used in catalysis are catalysts, and the process becomes homogeneous catalysis when the catalysts and reactants remain in the same phase. Formation of acetic acid is one of the popular homogeneous catalysis examples. This article discusses the advantages and disadvantages of homogeneous catalysis reactions. The homogeneous catalysts can be in gaseous or liquid states.