catalyst in chemistry | Types, Examples


The term “catalyst” can have different meanings, depending on the context in which it is used. most common definitions of the catalyst are given below:

In chemistry

In chemistry, a catalyst is a substance that fasten the rate of a chemical reaction without being utilized in the process. Catalysts work by reducing the activation energy necessary for the reaction to happen.

In Psychology

In social psychology, a catalyst is a human  who start or increases a process of alteration in a group or society. Catalysts could  be individuals or groups that produce a spark of stimulas or motivation for others to follow.

In business

In business, a catalyst is a human or event that origins a significant modification or improvement. For example

  • a new CEO might be a catalyst for turning around a struggling company
  • or a breakthrough product might be a catalyst for a company’s growth.

Types Of Catalyst

There are following types of catalysts,

1. Homogeneous catalysts:

In this catalysis  phase show similarity with the reactants(i.e., gas, liquid, or solid) . For example,

a solution of sulfuric acid can act as a homogeneous catalyst for the hydration of ethylene to form ethanol.

2. Heterogeneous catalysts:

These are catalysts that are in a changed phase from the reactants. For example

  • a solid metal catalyst
  • such as platinum or palladium
  • can be used to catalyze the hydrogenation of a liquid or gaseous reactant.

3. Base catalysts:

These are catalysts that increase the rate of a reaction by accepting a proton (H+) from one of the reactants. Examples include

  • sodium hydroxide( which is used to catalyze the hydrolysis of esters)
  • and metal oxides( which are used to catalyze the aldol condensation reaction).

4. Enzymes:

Enzymes are very specific in the reactions they catalyze and can be consumed in a broad  range of industrial applications

  • from food processing
  • to pharmaceuticals.

5. Acid catalysts:

These are catalysts that increase the rate of a reaction by donating a proton (H+) to one of the reactants. Examples include

  • sulfuric acid( which is used to catalyze the esterification of carboxylic acids)
  • and zeolites( which are used to catalyze the cracking of hydrocarbons).

6. Photocatalysts:

These are catalysts that are triggered by light, classically in the ultraviolet range. They can be used

  • to drive reactions such as the photodegradation of pollutants in wastewater treatment
  • or the production of hydrogen from water using sunlight.

Factor affecting the catalyst

There are various factors that can affect the efficiency and stability of a catalyst, including:

Chemical composition:

The chemical composition of a catalyst can disturb its activity and selectivity. For example

  • different metals or metal oxides can have different catalytic properties.

How their activity can be improved

Addition of a promoter or modifier can improve the catalytic activity or selectivity of a catalyst.

Catalyst support:

Catalysts are often maintained on a high surface area material, such as

  • Alumina
  • or silica

to deliver a larger surface area for the reactants to react with the catalyst.

The properties of the support can affect the

  • Activity
  • Selectivity
  • and stability of the catalyst.

For example

  • the pore size and surface area of the support can affect the accessibility of the active sites,
  • while the acidity or basicity of the support can alter the adsorption and reaction of the reactants.

The method used to form the catalyst can disturb its structure and characteristics. For example,

  • the temperature
  • time
  • and atmosphere used during the synthesis
  • or activation of the catalyst can affect the size, dispersion, and composition of the active sites.

Surface area and morphology:

The surface area and morphology of the catalyst can change its activity and selectivity. For example,

  • a catalyst with a higher surface area may have more active sites for the reactants to bind to
  • while a catalyst with a certain morphology (such as nanoparticles) can have unique electronic and geometric properties that affect its activity.


Catalysts can be disabled over time due to factors such as

  • Sintering
  • Poisoning
  • or leaching of active components.

Sintering happen when the catalyst particles add up and lost  their high surface area.

Poisoning occurs when impurities or other species block or hurt the active sites of the catalyst.

while leaching happen when the active components are eliminated from the catalyst surface over time.

Operating conditions:

The operating conditions of the reaction, such as

  • Temperature
  • Pressure
  • and reactant concentration

can affect the

  • performance
  • and stability of the catalyst.

For example,

  • high temperatures or pressures can become a reason of sintering or deactivation of the catalyst
  • while too low concentrations of reactants can lead to low reaction rates.


Overall, understanding these factors and optimizing the catalyst design and operating conditions can improve the

  • Performance
  • Selectivity
  • and stability of a catalyst in a given reaction.