Which element is commonly used as a catalyst in hydrogenation reactions?

Nickel is commonly used as a catalyst in hydrogenation reactions due to its effectiveness, availability, and cost efficiency. Hydrogenation reactions typically involve the addition of hydrogen to unsaturated hydrocarbons, and nickel serves as an excellent catalyst under moderate conditions.

Nickel's metallic properties allow it to provide a surface for the reactants to interact, facilitating the breaking of double bonds and the addition of hydrogen. It is particularly advantageous in industrial applications due to its relatively low cost compared to precious metals while still providing suitable catalytic activity.

While other metals like platinum and palladium are also effective catalysts for hydrogenation, they are significantly more expensive, making nickel a popular choice in various chemical processes. Iron, while it can function as a catalyst in other reactions, is not typically favored for hydrogenation.