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Why is a catalyst regenerated rather than used up during a reaction?

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dissociation of E–N — reaction mechanism Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E⁺ and N⁻ (see text).

A catalyst is regenerated during a chemical reaction because its fundamental role is to provide an alternative reaction mechanism that lowers the activation energy required for the process to occur.12

In this mechanism, the catalyst enters into a temporary chemical combination with the reactants to form reactive intermediates. These intermediates are designed to react more readily than the original reactants to form the desired end product. As these intermediates transform into the final product, the catalyst is released in its original form.12

Because the catalyst is not consumed, it remains available to participate in subsequent cycles, allowing a single catalyst molecule to facilitate the transformation of many reactant molecules. This cycle of combination and regeneration is precisely what allows a catalyst to accelerate a reaction without being depleted.21