C3/C4 olefins refer to a group of hydrocarbons that contain three or four carbon atoms and at least one double bond. These olefins are important building blocks for the production of various chemicals, including plastics, detergents, and synthetic rubbers. However, they are also highly reactive and can easily undergo unwanted reactions, such as polymerization or oxidation, during storage or transportation. Therefore, selective or complete hydrogenation is often used to stabilize these olefins and improve their handling and processing properties. The hydrogenation reaction is carried out under hydrogen atmosphere using a suitable catalyst. Depending on the catalyst, they can be used for either complete hydrogenation of double or triple bonds or selective hydrogenation, keeping one unsaturated bond intact. The related processes are the complete saturation process (CSP) and the selective hydrogenation process (SHP).