Steam Distillation-to calculate efficiency of steam distillation

Steam Distillation-to calculate efficiency of steam distillation
Distillation is the process to obtain pure liquid components from a mixture by boiling and then cooling the same.
The process of distillation is based on the difference in volatility of the components.
If in the given mixture, one liquid is volatile and the other component is non-volatile, then the volatile component vaporises out and distillation in this case results in complete separation.
If one component is more volatile than the other then after distillation we get a mixture containing high amount of more volatile component.
Thus there occurs partial separation of the mixture.
This results in increased concentration of selected products.
This partial mixture then can be separated using separating funnel. Distillation is used in pharmaceutical industry, food industry, chemical industry, beverage industry petroleum industry, etc.
There are various types of distillation like fractional distillation, steam distillation, simple distillation, flash distillation, distillation under reduced pressure, azeotropic distillation, vacuum distillation,etc depending on the technique used to carry out separation.
Out of all the methods available, steam distillation is used for heat sensitive materials and volatile oils separation.
Principle: -
In steam distillation, on boiling the mixture of immiscible liquids (water and the material to be separated), the material begins to boil at a temperature lower than the boiling point of the material and water. This happens due to the fact that both the liquids exert vapour pressure independent of each other i.e. each liquid exerts a vapour pressure as if the other liquid is not present. When the sum of the vapour pressures of both the liquids becomes equal to atmospheric pressure, the mixture begins to boil. (Boiling point of a liquid is the temperature at which the vapour pressure of the liquid becomes equal to atmospheric pressure). This happens at a point well below the boiling point of both the liquids.
Applications: -
Used for manufacturing of essential oils e.g. Perfumes.
Eucalyptus oil and orange oil are produced by this method.
Used for synthetic production of complex organic compounds.
Used for separation of immiscible liquids.
Camphor production is done using steam distillation.
Aromatic waters can be prepared by this technique.
Also used in petroleum and food industry.
Advantages: -
Maintains the integrity of the plant oils.
As the amount and time of steam supply can be controlled, the quality of the product is maintained by avoiding degradation and loss of aroma of the product.
It can be used for high boiling, water immiscible liquid separations.
Disadvantages: -
Equipment is costly.
Lot of care is required as the person works with pressurised system.
The material to be separated should be water immiscible and have molecular weight higher than water.
Efficiency of steam distillation:
Efficiency of steam distillation is calculated using the formula as
Percentage efficiency =(𝐏𝐫𝐚𝐜𝐭𝐢𝐜𝐚𝐥 𝐲𝐢𝐞𝐥𝐝)/( 𝐓𝐡𝐞𝐨𝐫𝐞𝐭𝐢𝐜𝐚𝐥 𝐲𝐢𝐞𝐥𝐝) x 100
Here, practical yield is the amount of pure component obtained after distillation as compared to pure water obtained after distillation.
Practical yield=(𝐀𝐦𝐨𝐮𝐧𝐭 𝐨𝐟 𝐜𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭 𝐨𝐛𝐭𝐚𝐢𝐧𝐞𝐝 𝐚𝐟𝐭𝐞𝐫 𝐝𝐢𝐬𝐭𝐢𝐥𝐥𝐚𝐭𝐢𝐨𝐧 )/(𝐀𝐦𝐨𝐮𝐧𝐭 𝐨𝐟 𝐰𝐚𝐭𝐞𝐫 𝐨𝐛𝐭𝐚𝐢𝐧𝐞𝐝 𝐚𝐟𝐭𝐞𝐫 𝐝𝐢𝐬𝐭𝐢𝐥𝐥𝐚𝐭𝐢𝐨𝐧 )
Thus, it gives the amount of pure organic liquid that will distilled out.
Theoretical yield is calculated based on the Raoult’s law. Vapour pressure and molecular weight of the component and water determine theoretical yield as
Theoretical yield
= (𝐌𝐚𝐬𝐬 𝐨𝐟 𝐜𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭)/( 𝐌𝐚𝐬𝐬 𝐨𝐟 𝐖𝐚𝐭𝐞𝐫 ) = ( 𝐕.𝐏 𝐨𝐟 𝐜𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭 𝐗 𝐌𝐨𝐥 𝐰𝐭 𝐨𝐟 𝐜𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭)/(𝐕. 𝐏 𝐨𝐟 𝐰𝐚𝐭𝐞𝐫 𝐗 𝐌𝐨𝐥 𝐰𝐭 𝐨𝐟 𝐰𝐚𝐭𝐞𝐫)
Thus, by calculating the percent efficiency we can conclude whether steam distillation is useful to carry out separation of the components without wasting material, energy, time etc.
If the percent efficiency is very low then alternative method for separation should be used.