A catalyst is a component that changes the rate of a reaction by guiding it down a different path that requires less energy to activate. Catalysts are essential for chemical processes to shift reaction steps and progress reasonably.

In the periodic table, we frequently mistaken transition metals with d-block metals. But transition metals are part of the d-block of the periodic table of elements, not all d-block metals may be considered transition metals. Scandium and zinc, for example, do not transition metals, despite being d-block elements. A transition metal must have an incompletely filled d-orbital to be a d-block element.

The most fundamental reason transition metals are useful catalysts is that, depending on the nature of the reaction, they can lend or take electrons from the reagent. Transition metals are useful catalysts because of their capacity to be in various oxidation states, interchange oxidation levels, form complexes with reagents, and be suitable suppliers of electrons.

Catalytic Properties

A catalyst is a component that changes the rate of a reaction by guiding it down a different path that requires less energy to activate. Catalysts are essential for chemical processes to shift reaction steps and progress reasonably.

Metals such as platinum and nickel make excellent catalysts because they adsorb strongly enough to hold and activate the reactants while allowing the products to escape. The reaction of ethene and hydrogen in a nickel catalyst is the most basic example.

Types of Catalysts

There are four types of catalysts:  

(1) homogeneous,  

(2) heterogeneous (solid), 

(3) heterogenised homogeneous, and 

(4) biocatalysts.

Catalytic Property of Transition Metals

The catalytic property of transition metals results from the following factors:

  1. Variable oxidation state: Transition metals generate unstable intermediate compounds with the help of an inconsistent oxidation state. These medium molecules open up a new path for the reaction with lower activation energy.
  1. Large surface area: When transition metals or their compounds are finely split, it gives a large surface area for the adsorption of reactants, resulting in a faster reaction due to the tighter contact.

Transition metals and their compounds are essential industrial and biological catalysts. Transition metals are excellent catalysts due to their availability of 3d and 4s electrons and their ability to change oxidation state. A solid transition metal catalyst with reactants in liquid or gas phases means that the catalyst is different from the reactants. Transition metals can establish weak bonds with reactants using electrons from the complexion (ligand) surface’s 3d and 4s orbitals. Once the reaction has occurred on a metallic exterior, these connections can break, releasing products.

One important example is the hydrogenation of alkenes using a Ni or Pt catalyst. Transition metals ionise in an aqueous solution as a homogeneous catalyst. The ion produces an intermediate compound with one or more reactants, and the intermediate then degrades to form products.

Catalytic Property of d-block Elements

Transition elements or d-block elements exhibit catalytic behaviour primarily for the following reasons:

  • They have unoccupied d-orbitals.
  • They are capable of displaying a range of valencies. 
  • They have a proclivity for forming complicated chemicals.

Conclusion

As discussed earlier, A catalyst is a component that changes the rate of a reaction by guiding it down a different path that requires less energy to activate. Catalysts are essential for chemical processes to shift reaction steps and progress reasonably. Transition metals and their compounds or complexes and d-block elements change the rate of a chemical process and act as catalysts. A catalyst develops an unstable intermediate compound in homogeneous catalysis, decomposing into products and regenerating the catalyst. However, transition metals necessitate heterogeneous catalysis. Transition metals have partially filled d-subshells that adsorb reactants on the surface and give a wide surface area for the reactants to react on. Transition metals are excellent catalysts due to their various oxidation states. As a result, compounds of Fe, Co, Ni, Pt, Pd, Cr, and other metals are utilised as catalysts in various processes.