Profile
Settings
Refer your friends
Sign out
Catalysis
Catalysis is a phenomenon that occurs when a catalyst is employed to speed up a chemical reaction.
What are the Different Types of Catalysis?
Catalysis is classified into three forms based on the nature and physical condition of the substance used in the chemical reaction.
1.Homogeneous Catalysis
2.Heterogeneous Catalysis
3.Autocatalysis
Heterogeneous Catalysis
The reacting chemicals in a reaction and the catalyst used in that reaction are not in the same state of matter in this sort of catalysis.
Example 1: Haber’s procedure for producing ammonia.
A compressor passes pure and dry Nitrogen and Hydrogen gasses in a 1: 3 ratio through it, maintaining a high pressure of 200 – 30 atmospheres. Iron oxide is employed as a catalyst in this procedure. It is a solid oxide that is used in a process where the reactants are gaseous. In the pressure of Iron oxide solid, nitrogen (g) interacts with hydrogen (g) to generate ammonia (g), resulting in heterogeneous catalysis.
Example 2: Sulphuric acid production via the contact technique.
The oxidation of sulfur dioxide is a crucial stage in this process. Sulfur dioxide is a gas, and oxygen is a gas, while vanadium pentoxide is a solid catalyst in this oxidation. Reactants and catalysts are in different states of matter in this process.
Mechanism of Heterogeneous Catalysis
Adsorption and intermediate chemical production are both involved in heterogeneous catalysis. The reactant molecule is adsorbed on the catalyst’s surface’s activation center. These come together to generate an active complex, which is a compound in between. This chemical breaks down into products.
The products are absorbed from the surface as soon as they are created, with no time delay. Adsorption of reactants on the surface of the catalyst, synthesis of intermediate compounds, and dissociation into a product are all part of heterogeneous catalysis.
1.On the surface of the nickel, ethene is hydrogenated to ethane.
2.On the surface of the catalyst, ether and hydrogen molecules are adsorbed.
3.Occlusion occurs when hydrogen takes up the majority of the activation center.
4.To generate an active compound, ethane molecules attack their double bond area.
5.Ethane is formed when ether combines with active hydrogen.
6.This ethane is absorbed on the catalyst’s surface.
Electrocatalysis
Several forms of metal-containing catalysts are employed in electrochemistry, particularly when dealing with fuel cell engineering. The primary function of these catalysts is to increase the rates of the half-reactions that occur in a fuel cell. The most common electrocatalyst utilized in a fuel cell is made up of platinum nanoparticles. These are now supported by carbon particles that are slightly larger. Platinum accelerates the rate of oxygen reduction to water or hydroxide when it comes into contact with one of the electrodes in a fuel cell (also hydrogen peroxide).
Homogeneous Catalysis
Homogeneous catalysis is defined as catalysis in which the catalyst and the reactants are in the same state of matter. Homogeneous catalysts work in the same step as the reactants. Homogeneous catalysts and substrates are often dissolved in a solvent. One example of homogeneous catalysis is the effect of H+ on the esterification of carboxylic acids, such as the creation of methyl acetate from acetic acid and methanol. High-volume processes requiring a homogeneous catalyst include hydroformylation, hydrosilylation, and hydrocyanation. Inorganic chemists usually associate homogeneous catalysis with organometallic catalysts. Many homogeneous catalysts, however, are not organometallic, as the use of cobalt salts to catalyze the oxidation of p-xylene to terephthalic acid demonstrates.
While transition metals receive a lot of attention in catalysis research, small organic molecules without metals can also have catalytic capabilities, as evidenced by the lack of transition metals in many enzymes. Organic catalysts often require a higher load (catalyst quantity per unit quantity of reactant, expressed in mol percentage of material) than transition metal(-ion)-based catalysts, however these catalysts are typically available in bulk, lowering prices. In the early 2000s, such organocatalysts were called a “new breed,” and they compete with metal-based catalysts (-ion).
Example 1: Ethyl acetate hydrolysis in the presence of dilute acid.
Ethyl acetate is an ester functional group-containing liquid. It produces ethyl alcohol and acetic acid when it combines with water in the presence of dilute sulphuric acid, which is a liquid.
The reactants and catalysts in the aforementioned reaction are in the same state of matter. As a result, it’s homogenous catalysis.
Example 2: Sulfur dioxide oxidation in the lead chamber process.
Sulphuric acid is produced via the lead chamber technique. Nitric oxide gas is employed as a catalyst in this procedure.
As SO2 and O2, as well as the catalyst NO, are all gases in the aforementioned reaction, it is homogenous.
Conclusion
We conclude that Catalysts reduce the amount of energy required to start a chemical process, therefore speeding it up. Many industrial processes rely on chemical reactions to transform raw materials into useful products, and catalysis is at the heart of them. Catalysts are used to make plastics and a variety of other industrial goods.
