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A catalyst is a substance that is not consumed by a chemical process but reduces the activating power of the reaction. A catalyst, in other words, is a reaction as well as a product of a chemical reaction. To catalyse the reaction, only a little amount of catalyst is required.
Homogeneous catalysis:
A homogeneous catalyst is a catalytic system in which the surfaces and catalyst components for a reaction are maintained together in a single phase, usually liquid.
Heterogeneous catalysis:
A heterogeneous catalyst is one that does not take part in the process in which it is growing. The catalyst and the processes in heterogeneous catalysis can be in different phases, such as gas-phase reactions catalysed by solids.
Examples of Homogeneous catalysis:
Carbonylation:
Alcohols are converted to carboxylic acids by adding CO to a molecule (substrate). Carbonization is used to produce this conversion. In the presence of a homogeneous catalyst, methanol (CH3OH) interacts with carbon monoxide (CO) to form acetic acid.
Lead chamber process:
The oxidation state of sulphur dioxide is used in the main chamber process for the manufacture of sulfuric acid. This oxidation of SO2 gas occurs in the presence of oxygen, with NO gas acting as a catalyst.
Hydrolysis of ester:
In the presence of water and acid, acetyl-hydrolysis of ethyl acetate ester yields ethanol and ethanoic acid. The aqueous phase of ethyl acetate is the same phase in which acid is added. As a result, it is categorised as a homogeneous catalyst.
Examples of Heterogeneous catalysis:
Oxidation of sulphur dioxide:
Haber process:
Ammonia into nitric acid:
Catalyst activity:
The catalyst has the ability to speed up the reaction. The activity of the catalyst refers to the catalyst’s ability. It is determined by the reaction’s absorption on the catalyst’s surface. Chemisorption is a crucial element in the regulation of the stimulant effect. The link formed between the catalyst surface and the reaction during absorption should not be excessively strong or too weak.
It must be strong enough to activate the catalyst, but the reactant molecules are too weak to be stable on the catalyst’s surface, leaving space for new reactants to be absorbed. The catalytic activity of group 5 to group 11 metals increases for the hydrogenation process in general. The periodic table’s group 7-9 elements had the highest catalytic activity.
Specificity and selectivity of catalyst:
The catalyst’s effect is very specific, in that the provided substance functions as one.
The catalyst is only present in one type of reaction, not all of them. It’s a remarkable activity.
Enzyme specificity refers to the ability of an enzyme to catalyse only one type of reaction.
The specification refers to the fact that it is a one-of-a-kind chemical that acts exclusively on its own surface.
Making it into a specific item. That is, the enzyme binds to only certain molecules, and only one reaction occurs as a result. Some enzymes are highly selective and catalytically transform a specific surface to create a one-of-a-kind product.
The capacity to specify a catalyst’s reaction while excluding other products is referred to as selectivity. The ability to direct the reaction is determined by the catalyst used.
When a product is in the same reaction state as another, products are also possible.
Examples:
In presence of Ni as a catalyst
in presence of Cu as catalyst
Enzyme substrate specificity:
The ability of an enzyme to select an exact surface from a group of chemical compounds is known as specificity. In fact, specificity is a molecular identification mechanism that relies on complementarity between the enzyme and the substrate in terms of confirmation and structure.
Four different kinds of specificity:
Absolute specificity refers to the enzyme’s ability to catalyse only one reaction.
Group specificity refers to the enzyme’s ability to only operate on particular compounds in a given group.
Amino, phosphate, and methyl groups are examples of functional groups.
Linkage Specificity – An enzyme that only operates on one type of chemical bond, regardless of the rest of the molecular structure.
Stereochemical specificity refers to the enzyme’s ability to function on a single steric or optical isomer.
Conclusion:
A catalyst is a substance that, when introduced, increases the rate of a chemical process. A homogeneous catalyst is a catalytic system in which the reaction’s surfaces and catalyst components are kept in a single phase, usually liquid. A heterogeneous catalyst is one that does not participate in the growth process. In heterogeneous catalysis, the catalyst and the processes might be in distinct phases, such as gas-phase reactions catalysed by solids.
The catalyst has a very specific effect in that it makes the delivered chemical function as one.
Only one sort of reaction uses the catalyst, not all of them.
