Question:

Which catalyst is used in hydrogenation of oils and fats?

Updated On: Aug 16, 2023
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Solution and Explanation

The most commonly used catalyst for the hydrogenation of oils and fats is a nickel catalyst. Nickel catalysts are typically used in the form of finely divided nickel metal or nickel compounds, such as nickel oxide (NiO) or nickel on a support material like silica or alumina. These catalysts facilitate the addition of hydrogen gas (H₂) to the carbon-carbon double bonds present in unsaturated fatty acids, leading to the conversion of liquid vegetable oils into more solid fats or semi-solid products like margarine or shortening. Hydrogenation improves the stability and shelf life of oils and fats by reducing their susceptibility to oxidation and rancidity.

These catalysts facilitate the addition of hydrogen gas to the carbon-carbon double bonds present in unsaturated fatty acids, converting them into saturated fats. This process is utilized in the food industry to produce solid fats from liquid vegetable oils, thereby improving the texture, shelf life, and cooking properties of various food products.

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Concepts Used:

Chemical Kinetics

Chemical kinetics is the description of the rate of a chemical reaction. This is the rate at which the reactants are transformed into products. This may take place by abiotic or by biological systems, such as microbial metabolism.

Rate of a Chemical Reaction:

The speed of a reaction or the rate of a reaction can be defined as the change in concentration of a reactant or product in unit time. To be more specific, it can be expressed in terms of: (i) the rate of decrease in the concentration of any one of the reactants, or (ii) the rate of increase in concentration of any one of the products. Consider a hypothetical reaction, assuming that the volume of the system remains constant. R → P

Read More: Chemical Kinetics MCQ

Factors Affecting The Reaction Rate:

  • The concentration of Reactants - According to collision theory, which is discussed later, reactant molecules collide with each other to form products.
  • Nature of the Reactants - The reaction rate also depends on the types of substances that are reacting.
  • Physical State of Reactants - The physical state of a reactant whether it is solid, liquid, or gas can greatly affect the rate of change.
  • Surface Area of Reactants - When two or more reactants are in the same phase of fluid, their particles collide more often than when either or both are in the solid phase or when they are in a heterogeneous mixture. In a heterogeneous medium, the collision between the particles occurs at an interface between phases. Compared to the homogeneous case, the number of collisions between reactants per unit time is significantly reduced, and so is the reaction rate.
  • Temperature - If the temperature is increased, the number of collisions between reactant molecules per second. Increases, thereby increasing the rate of the reaction.
  • Effect Of Solvent - The nature of the solvent also depends on the reaction rate of the solute particles.
  • Catalyst - Catalysts alter the rate of the reaction by changing the reaction mechanism.