Question

which catalyst used for reduction of hydrogenated oil

Answer 1

mainly nickel is used

Answer 2

Answer: Nickel

Catalysts are substances which change the reaction rate but do not participate in the reactions. Alkenes generally have activation energy which is very high and so their hydrogenation does not occur spontaneously. Finely divided metals such as nickel, platinum and palladium, act as catalysts and lower their activation energies. Thus, it speeds up the hydrogenation process.  

Firstly, the reactant gets adsorbed onto the catalyst surface and then the reaction occurs.