Which type of reaction is involved in the given reaction?

$C_2{H}_4 + H_2 \stackrel{(\mathit{ }Ni catalyst)}{\to } C_2{H}_6$

The given reaction is an Addition type of reaction.

$C_2{H}_4 + H_2 \stackrel{(\mathit{ }Ni catalyst)}{\to } C_2{H}_6$

In the presence of catalysts like palladium or nickel, unsaturated hydrocarbons add hydrogen to produce saturated hydrocarbons.

Catalysts are substances that speed up or slow down reactions without changing the course of the reaction itself. This process is frequently used to hydrogenate vegetable oils using a nickel catalyst.

Animal fats have long saturated carbon chains, but vegetable oils often contain long unsaturated carbon chains.