Types of Catalysts with Examples

Catalysts are substances that change the rate of reaction by changing the path of the reaction. A catalyst is a substance that allows a chemical reaction to occur faster or under different conditions, such as at a lower temperature. 

Catalysts can be of any matter – solid, liquid, or gas. Metals and their oxides, such as sulphides and halides, are examples of solid catalysts. Catalysts can also be liquid or gaseous elements that are in their purest form. These components are sometimes combined with appropriate solvents or carriers. 

Characteristics of a catalyst

• Catalysts help in increasing the rate of reaction by reading the activation energy of the reaction. 
• Catalysts cannot start the reaction. They only activate the reaction.
• The activity of the catalyst depends upon its optimum pH and temperature.
• A small amount of catalyst is sufficient to carry out the reactions.
• The catalysts are generally specific to the reactions. Specific catalysts work on specific reactions, and will fail to catalyse other reactions.

Types of catalysts

Catalysts are of two types:

Positive catalyst

The catalyst that increases the rate of reaction is a positive catalyst. The rate of reaction increases by lowering the activation energy. It increases the percentage of products.

An example is the preparation of ammonia by Haber’s process. Iron oxide act as a catalyst in this reaction, increasing the production of ammonia.

More examples of positive catalysts are manganese dioxide, vanadium pentoxide, and platinum. Manganese dioxide is used in the decomposition of hydrogen peroxide. Vanadium pentoxide is used in many processes such as oxidation of sulphur dioxide, in the oxidation of ethanol, to produce phthalic acid, oxalic acids, etc. 

Negative catalyst

Catalysts that decrease the rate of reaction are called negative catalysts. They decrease the rate of reaction by increasing the activation energy. They lower the production of the reaction. 

An example of a negative catalyst is acetanilide, which is used in the decomposition of hydrogen peroxide into oxygen and water. Phosphoric acid acts as a negative catalyst in the decomposition of dihydrogen dioxide. Alcohol is a negative catalyst in the oxidation process of sodium sulphate.

Importance of catalyst 

All products that are produced in the industries, sometimes go through catalysis.

Energy processing

The refining of petroleum uses catalysis; the burning of fossil fuels uses catalysis. 

Production of chemicals

The production of chemicals in industries, in large amounts, is done by the process of catalysis. Nitric acid, sulphuric acid, xylene, etc. Many polymers are made from ethylene and propylene by the process of Ziegler-Natta. The process of carbonylation uses metal catalysts. Some more reactions are the Heck reaction, Friedel-craft reactions, etc. Many pharmaceutical products are prepared by enantioselective catalysis.

Food processing

In the food industry, catalysts are a common and important substance. Many food products are prepared by using catalysts.

Environment

Catalysts affect the environment in good ways. It helps to produce green fuels. It is also utilised in the reduction of greenhouse gases. Catalysts help in converting waste materials into raw materials that can produce energy.

Uses of catalyst

The reactions are employed in a variety of sectors to create useful goods.

• In order to manufacture margarine, a catalyst is used in the reaction of hydrogen with fat.
• A catalyst accelerates the reaction by slowing down the rate of activation energy.
• Even at lower temperatures, a catalyst can carry out the reaction.

Conclusion

Catalysts are of great importance in daily life and many industries. Catalysts help to

increase the production of any reaction and lower the activation energy. They do not get consumed in the reaction and so can be used again for other reactions. Catalysts do not impact the reactions and products, and they depend upon specific pH and temperature.