Catalysis  

Catalysis meaning involves a process in which a catalyst, a substance that remains unchanged, speeds up a chemical reaction by offering an alternative pathway with lower activation energy without undergoing any lasting alteration itself.

1.0What is Catalysis?

Catalysis speeds up reactions by lowering energy barriers. Catalysts are substances that enable this without being used up in the process.

2.0Difference Between Catalyst and Catalysis

A catalyst speeds up a chemical reaction or lowers the temperature or pressure needed to start one without itself being consumed during the reaction, while Catalysis is the process of adding a catalyst to facilitate a reaction.

3.0Types of Catalysis with Catalysis Examples

Hydrogenation catalysis meaning involves using metals like iridium, nickel, palladium, platinum, rhodium, or ruthenium to facilitate reactions with hydrogen. These catalysts are either heterogeneous or homogeneous.

1. Homogeneous Catalysis:

In this type, the catalyst and the reactants exist in the same phase, for example of homogeneous catalysis, Oxidation of sulphur dioxide in the lead chamber process.

$2{\mathrm{SO}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\stackrel{\mathrm{NO}(\mathrm{g})}{\to }2{\mathrm{SO}}_3(\mathrm{g})$

In the above reaction, SO₂ and O₂, along with catalyst NO, are gases; hence, it is considered as an example of homogeneous catalysis.

2. Heterogeneous Catalysis: 

Here, the catalyst exists in a different phase from the reactants. A classic example of heterogeneous catalysis is the catalytic converter in automobiles where platinum or palladium nanoparticles (solid catalyst) facilitate the conversion of harmful gases into less harmful substances.

Another important example of heterogeneous catalysis is Manufacture of sulphuric acid by contact process. In this oxidation, sulphur dioxide and oxygen are gases, while vanadium pentoxide is a solid catalyst. Besides, reactants and catalysts are in different states of matter. See the reaction below.

$2{\mathrm{SO}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\stackrel{{\mathrm{v}}_2{\mathrm{O}}_5}{\to }2{\mathrm{SO}}_3(\mathrm{g})$

3. Catalysis by Enzymes: 

Enzymes act as biological catalysts, usually proteins or RNA molecules, accelerating specific reactions in living organisms. 

Examples include enzymes involved in digestion, photosynthesis, and cellular respiration. 

Another example is the hydrolysis of cane sugar, which is given below.

${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\text{ (aq.) })+{\mathrm{H}}_2\mathrm{O}\stackrel{\text{ Invertase }}{\to }{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\text{ (aq. })+{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6(\mathrm{aq})$

4. Acid and Base Catalysis:

 Certain substances act as catalysts by donating or accepting protons. Strong acids or bases often serve as catalysts in reactions like esterification or hydrolysis.

5. Photochemical Catalysis: 

Catalysis that involves the absorption of photons to provide the energy needed to drive a reaction. 

For Example, photocatalysts like titanium dioxide are used in water purification and air purification systems.

Another example is, The photolysis of ozone involves the breaking down of ozone (O₃) molecules into oxygen (O₂) molecules in the presence of ultraviolet (UV) radiation. Reaction is given below:

$2{\mathrm{O}}_3(\mathrm{g})+{\mathrm{H}}_2\mathrm{O}(\mathrm{g})\stackrel{\mathrm{h}v}{\to }{\mathrm{O}}_2(\mathrm{g})+2\mathrm{OH}$

6. Autocatalysis:

Some reactions are catalyzed by one of their own products. As the reaction progresses, the product catalyzes its further formation. An example is the iodination of acetone in the presence of iodine and Hydrolysis of an Ester.

Another example is, the autocatalysis of AsH₃, which is arsine, involves a reaction where arsine acts as both a reactant and a catalyst, speeding up its own production.

Another example is, decomposition of arsine (AsH₃) is not typically considered an autocatalytic reaction. Autocatalysis involves a reaction where one of the products acts as a catalyst for the same reaction to proceed more rapidly.

$2\mathrm{A}{\mathrm{s}}_3{H}_3\to 2\mathrm{As}+3{\mathrm{H}}_2$

7. Industrial Catalysis: 

This encompasses various catalysts used in large-scale industrial processes, such as petrochemical refining, ammonia synthesis, and polymer manufacturing.

8. Electrocatalysis: 

Involves the acceleration of electrochemical reactions at the electrode surfaces, crucial in fuel cells, electrolysis, and batteries.

4.0Applications of Catalysis

Catalysis plays a very important role in various industries, including petrochemicals, pharmaceuticals, food production, and environmental processes. It is mainly used in the synthesis of a wide range of products and in the removal of pollutants from air and water. Here is a list of applications of Catalysis-

Chemical Manufacturing: 

Catalysts are essential in the production of chemicals, allowing for more efficient, less energy-intensive processes. For example, the Haber-Bosch process uses catalysts to synthesize ammonia from nitrogen and hydrogen, which is vital for producing fertilizers.

Petroleum Refining: 

Catalysts are used extensively in refining petroleum to produce fuels and other chemicals. Processes like catalytic cracking break long-chain hydrocarbons into shorter ones, increasing the yield of valuable products like gasoline.

Environmental Protection: 

Catalytic converters in vehicles convert harmful gases from exhaust (like CO and unburned hydrocarbons) into less harmful substances such as nitrogen, carbon dioxide, and water vapor, significantly reducing pollution.

Pharmaceuticals: 

Many pharmaceuticals are manufactured using catalytic processes, which can help in creating more effective drugs with fewer by-products and lower costs.

Food Processing: 

Enzymatic catalysis is used in the food industry to modify fats, enhance flavors, and process dairy products. For example, lactase is used to break down lactose in milk for lactose-free products.

Energy Production: 

Catalysts are involved in the production of biofuels from biomass. They also play a role in fuel cells, where they speed up the reactions at the electrodes of hydrogen or methanol fuel cells.

Material Science: 

Catalysis is used in the production of polymers and other materials. For instance, catalysts are used to polymerize ethylene to polyethylene, a common plastic.

Water Treatment: 

Catalytic processes are employed in water treatment to remove contaminants and purify water, often involving oxidation reactions that break down pollutants.