ANS:D - Multicomponent distillation.

Multicomponent distillation is a separation process used to separate a mixture of two or more volatile components based on their differences in boiling points. Unlike simple distillation, which involves the separation of a binary mixture (two components), multicomponent distillation deals with mixtures containing three or more components. Explanation:

1. Objective:
   • The primary objective of multicomponent distillation is to separate a multicomponent mixture into its individual components, each with a desired purity.
2. Boiling Point Differences:
   • Multicomponent distillation exploits the differences in boiling points of the components in the mixture.
   • Each component in the mixture has a unique boiling point, and the separation is achieved by vaporizing the mixture and then condensing the vapors back into liquid form, thereby selectively removing each component according to its boiling point.
3. Fractional Distillation:
   • Multicomponent distillation is typically carried out using fractional distillation columns, which consist of multiple trays or packing material.
   • The mixture is heated in a distillation column, and as the temperature rises, components with lower boiling points vaporize first, rise through the column, and condense on the trays or packing material.
   • The condensed liquid is then collected at different points along the column, resulting in the separation of the components based on their boiling points.
4. Multistage Process:
   • Multicomponent distillation is a multistage process, where each stage (tray or packing) facilitates further separation of the components.
   • As the vapor rises through the column, it comes into contact with the liquid on the trays or packing material. Mass transfer occurs between the vapor and liquid phases, leading to enrichment of certain components in the vapor phase and depletion in the liquid phase.
   • This continuous process of vaporization, condensation, and mass transfer at each stage enhances the separation efficiency of the distillation column.
5. Applications:
   • Multicomponent distillation is widely used in various industries, including petrochemical, chemical, and pharmaceutical industries.
   • It is used for the separation of complex mixtures such as crude oil into its individual fractions (e.g., gasoline, diesel, kerosene) and in the purification of chemicals and pharmaceutical products.
6. Challenges:
   • Multicomponent distillation can be challenging due to factors such as the presence of azeotropes (constant boiling mixtures) and the need to optimize operating conditions such as reflux ratio, temperature, and pressure to achieve desired separations.

In summary, multicomponent distillation is a vital separation process used to separate complex mixtures into their individual components based on differences in boiling points. It relies on fractional distillation columns and multistage separation mechanisms to achieve efficient separation of the components.