Which of the following catalytic systems is used for the reduction of unsaturated hydrocarbon to saturated hydrocarbon? 

The correct answer is Nickel and H2.

Key PointsReduction of Unsaturated Hydrocarbons to Saturated Hydrocarbons

• The reduction of unsaturated hydrocarbons to saturated hydrocarbons involves the addition of hydrogen (H2) across the double or triple bonds of alkenes or alkynes, respectively, turning them into alkanes.
• This process is known as hydrogenation and requires the presence of a catalyst to proceed under mild conditions.
• Nickel (Ni) is a widely used catalyst for this purpose due to its effectiveness in breaking the H-H bond and facilitating its addition to the unsaturated hydrocarbon.
• Other metals like Palladium (Pd) and Platinum (Pt) are also used as catalysts in hydrogenation reactions, but Nickel is preferred for its cost-effectiveness and availability.
• The reaction typically occurs under increased pressure and at moderate temperatures, which the Nickel catalyst helps to lower, making the process energetically favorable.

Hence, the correct option is Nickel and H2.

Additional Information

• Hydrogenation reactions are not only limited to the production of saturated hydrocarbons but also play a significant role in the food industry, where they are used to convert vegetable oils into semi-solid fats for margarine and shortening.
• The choice of catalyst and reaction conditions can influence the selectivity of the hydrogenation process, allowing for the partial hydrogenation of polyunsaturated fats to monounsaturated fats, which are considered healthier.
• Catalyst poisoning is a phenomenon where the catalyst's activity is significantly reduced due to the presence of certain substances that strongly adsorb to the catalyst surface, thereby blocking the active sites. Sulphur compounds are common poisons for Nickel catalysts in hydrogenation reactions.
• The development of more efficient and selective catalysts is a key area of research in green chemistry, aiming to reduce energy consumption and improve the sustainability of chemical processes.