7 Types Of Catalysts and Their Functions

14 min read
Types of catalysts

There are 7 different Types of Catalysts in Chemistry. They are substances that alter the rate of a chemical reaction without itself undergoing a permanent change in chemical composition.

Firstly, Let’s see what those list of catalysts is.

  1. Compounds that can Oxidise and Reduce – Cobalt compounds.
  2. Water.
  3. Hydrogen and Hydroxyl ions.
  4. Finely divided metals.
  5. Metal oxides.
  6. Biochemical catalysts or Enzymes.
  7. Negative catalysts.

So, let’s discuss each of the above catalyst ad their functions with examples.

1. Compounds that can Oxidise and Reduce – Cobalt compounds

In this type of catalyst, cobalt compounds catalyze the decomposition of hypochlorites. For example, A small quantity of cobalt nitrate solution added to bleaching powder causes the rapid evolution of oxygen.

2CaOCl -> 2CaCl2+ O2

Calcium chloride and oxygen are the final products. The following reactions presume to occur.

  1. The lime in the bleaching powder forms cobaltous hydroxide which,
  2. Forms cobaltic hydroxide with the oxygen in the bleaching powder.
  3. Being unstable, the cobaltic hydroxide loses oxygen to form cobaltous hydroxide.

Cobaltous hydroxide then reacts with more bleaching powder. Reactions for the above statements presented below.

  1. Co(NO3)2 + Ca(OH)2 → Co(OH)2 + Ca(NO3)2
  2. 2Co(OH)2 + CaOCl2 + H2O → 2Co(OH)3 + CaCl2
  3. 4Co(OH)3 → 4Co(OH)2 + 2H2O + O2

Also, By repetition of the process, a small amount of a cobalt salt can decompose a considerable quantity of bleaching powder.

Another example is the catalytic effect of cupric chloride on the oxidation of hydrogen chloride.

4HCl + O2 -> 2H2O + 2Cl2

The cupric chloride probably reduces to chlorine and cuprous chloride. Then reacts with hydrogen chloride and oxygen to reform cupric chloride and water. The cupric chloride thus undergoes alternate reduction and oxidation.

  1. 2CuCl2 → Cu2Cl2 + Cl2
  2. 2Cu2Cl2 + 4HCl + O2→ 4CuCl2 + 2H2O

Hydrogen peroxide oxidizes a large number of organic compounds. The action catalyzes y the presence of small amounts of ferrous compounds. E.g., ferrous sulfate. Also, The ferrous sulfate probably converts into ferric compounds in the process.

Know more – Characteristics of Catalytic Reactions.

2. Water

A large number of reactions do not appear to take place in the absence of water or If they do only at infinity slow rate. Therefore water is a significant catalyst that belongs to the Types Of Catalysts.

Water as a catalyst under types of catalysts

For example, perfectly dry carbon monoxide and oxygen do not combine to form carbon dioxide. But in the presence of the slightest trace of water vapor. They combine when sparked with explosive violence. Among other reactions catalyzed by traces of water is the combination of hydrogen and chlorine, hydrogen chloride and ammonia, carbon dioxide, and lime, and sulfur, and oxygen.

3. Hydrogen and Hydroxyl ions

When acids dissolve in water, they dissociate to form hydrogen ions. Similarly, alkalis furnish hydroxyl ions. The hydrolysis of a number of organic compounds takes place more rapidly in the presence of these ions. When cane sugar dissolved in water, it is very slowly hydrolyzed (or “inverted”) to a mixture of glucose and fructose.

C12H22O11 + H2O -> C6H12O6 + C6H12O6

This change takes months to complete, but the presence of hydrogen ions accelerates the rate of reaction so considerably that it is complete in a few hours.

Also, another reaction catalyzed by hydrogen ions is the hydrolysis of esters. Water hydrolyzes the ester ethyl acetate to acetic acid and ethyl alcohol.

CH3.CO.OC2H5 + H.OH ⇌ CH3.CO.OH + C2H5OH

The change, as the arrows indicate, is reversible. So, It takes place slowly in the presence of water only. The rate of reaction is considerably increased when hydrogen ions are present.

4. Finely Divided Metals

In these Types Of Catalysts, there are certain metals, especially platinum, nickel, iron, and copper. They very effective in promoting specific gaseous reactions. Also, it is essential in most cases that the metal should be in a finely divided condition. So, Among the more important reactions catalyzed by these metals are as follows.

Gaseous ReactionCatalyst
2SO2 + O2 ⇌ 2SO3Platinum
N2 + 3H2 ⇌ 2NH3Iron or Platinum
2H2 + O2 -> 2H2OPlatinum
C2H4 + H2 -> C2H6Nickel
4NH3 + 5O2 -> 4NO + 6H2OPlatinum or Iron
Metal Catalysts

Also, Most finely divided metals and colloidal solutions of metals accelerate the decomposition of hydrogen peroxide.

2H2O2 -> 2H2O + O2

Finely divided nickel use technically in the manufacture of edible fats (e.g., margarine) by the reduction of unsaturated vegetable oils. These are mixed with finely divided nickel and hydrogen passed through under pressure at 1800– 2000C. Also, Hydrogen is taken up with the formation of solid fat, which is a mixture of saturated compounds.

5. Metal Oxides

Metal oxides often use to catalyze reactions of industrial importance.  For example, ferric oxides as a catalyst in the Bosch process for preparing hydrogen from carbon monoxide and steam. Also, Zinc oxide with chromium oxide as a promoter used as a catalyst in the manufacture of methanol from carbon monoxide and hydrogen.

CO + 2H2 -> CH3OH

Ferric and bismuth oxides sometimes employ instead of platinum in the manufacture of nitric acid from ammonia. For example, Heated alumina, Al2O3, use in a  number of reactions in organic chemistry. E.g., the dehydrogenation of ethanol to form ethylene. Also, Iron and cobalt oxides are catalysts in the hydrogenation of coal to form a hydrocarbon mixture with the properties of petrol.

6. Biochemical catalysts or Enzymes

These Types of Catalysts are complex colloidal substances. But there are some enzymes obtained in crystalline form as well. Also, They elaborate by the cells of living plants and animals that are capable of altering the rate of chemical reactions occurring in living organisms. Most importantly, They differ from inorganic catalysts in the following respects,

Enzymatic reaction process

How Enzymes differ from Inorganic catalysts

  1. Enzymes are permanently inactivated at temperatures above about 500C.
  2. Also, They often combine with substances formed in a reaction they catalyze.
  3. Their action is more specific than those of inorganic catalysts.
  4. They require the presence of a second substance known as a co-enzyme for optimum activity.

So, In this connexion, it may note that inorganic catalysts are often more effective in the presence of a promoter. Thus a little molybdenum or silica increases the catalytic effect of iron in the manufacture of ammonia from nitrogen and hydrogen.

Examples of Enzyme action

  1. The conversion of glucose into carbon dioxide and alcohol by the enzyme zymase present in yeast cells.
  2. The hydrolysis of cane sugar into glucose and fructose by acid invertase, present in intestinal juice.
  3. The hydrolysis of fats into organic acids and glycerol by lipase in the small intestine.

7. Negative Catalysts

Under Types of Catalysts,  a negative catalyst retards the rate of the chemical reaction. Thus the decomposition of hydrogen peroxide retard by the presence of alcohol or glycerol. Also, The decomposition of chloroform is also retard by the presence of 1% alcohol.

Negative catalysts reaction process under types of catalysts
Negative catalysts path

Also, The action of a positive catalyst is frequently diminished or even entirely inhibited by the presence of very small quantities of impurities. Therefore, They are said to “poison” the catalyst. Arsenic, for example, reduces the efficiency of platinum used as a catalyst in effecting the combination of sulfur dioxide and oxygen. Also, Hydrogen cyanide, hydrogen sulfide, and mercuric chloride are general catalytic poisons.

Conclusion – Types Of Catalysts

Finally, Catalysts are beneficial substances that can use to increase the rate of reactions. So, from this article, we have discussed 7 Types of Catalysts. They are inorganic or organic, natural, or human-made. Also, Some catalysts are unique to a specific chemical reaction.  However, they are playing a vital role in the Chemical world.

How can we divide Catalytic Actions?

Homogeneous and Heterogeneous catalysts

Examples for Plant Enzymes

Proteases.
Amylases.
Lipases.

Examples for Animal Enzymes

Lipases
Amylase
Maltase
Trypsin 

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