DISTILLATION

Application, basic terminology, difference between distillation and evaporation, classification of distillation method, principles, construction, working, uses, merits and demerits of simple distillation, Flash distillation, Fractional distillation.

1. DISTILLATION PROF. TAUFIK MULLA ASST. PROFESSOR DEPT. OF PHARMACEUTICS SPBC COLLEGE OF PHARMACY

2. DISTILLATION Distillation is the process of converting liquid into its vapors by heating and reconverting it again into liquid by condensing the vapors. Distillation process involve 2 phase Converting liquid into vapor phase Transfer vapor to other place and recover liquid by condensation If the mixture contain volatile and non volatile liquid together, so its easy to separate volatile liquid from mixture by distillation. In other word we can say, distillation is considered as separation or purification method.

3. application Separation of volatile oil from clove, anise seed, eucalyptus leaves by steam distillation method. Simple distillation method used for purification of organic solvent. Simple distillation method used for determination of boiling range of liquid as per I.P. 96. Aromatic spirit of ammonia prepared by simple distillation method. Distilled water, water for injection can be prepared by simple and compression distillation method as per I.P.

4. In petroleum industry, crude oil refined by distillation method. Solvent used for extraction of drug from plant parts. Recovered that solution by using distillation method to avoid environmental contamination. Distillation method used in quality control test like to determine alcohol content in liquid mixture. The drug obtained from chemical reaction, can be purified by using distillation method.

5. terminology Distillation – used when condensed vapor require as a product Evaporation – concentrated residue require as a product. Temperature maintain at below boiling point. In this method, vapor is not condensed. Drying – dry solid material require as a product. Binary Mixture - When two liquids mixed together, they may be miscible with each other in all proportion, such miscible liquid are known as binary mixtures of liquid. Example - Ethanol + Water Acetone + Water Benzene + Carbon tetrachloride

6. Ideal Solution (Perfect solution) - Ideal solution is defined as the one in which there is no change in the properties of components other than dilution, when they mixed to form a solution. Properties of ideal solution Total volume of solution is equal to sum of volumes of each component No heat absorbed and No heat evolved No Chemical reaction in-between Final volume of solution represents additive property of individual components Follow Raoul's low

7. Ideal Solution (Perfect solution) - Ideal solution is defined as the one in which there is no change in the properties of components other than dilution, when they mixed to form a solution. Properties of ideal solution Total volume of solution is equal to sum of volumes of each component No heat absorbed and No heat evolved No Chemical reaction in-between Final volume of solution represents additive property of individual components Follow Raoul's low

8. Real Solution - Most system shows varying degree of deviation from raoult’s law, depending on nature of liquids and temperature. These solution are known as real solution. Properties of Real solution Heat may absorbed or evolved Chemical reaction occurs in-between Final volume of solution represents additive property of individual components Don’t Follow Raoul's low

9. Difference

10. Classification of distillation method Simple distillation Flash distillation Fractional distillation Azeotropic distillation Distillation under reduced pressure Steam distillation Molecular distillation Destructive distillation Compression distillation

11. Simple distillation It is a process of converting a single constituent form liquid mixture into its vapor, and transferring the vapor to another place and condensing it again into liquid. The process also called as differential distillation. Principle : Liquid boil when vapor pressure equal to atmospheric pressure. Simple distillation conduct at boiling point. If liquid have high volatility then its easy to separate by simple distillation. Boil the liquid and vapor transferred to another place and condensed it.

12. Construction : It consist distillation flask with side arm slopping downward. Condenser fitted to side arm by cork. Condenser usually water condenser which continuously circulate water. Condenser is connected to receiver flask using adapter.

13. Working : Liquid filled in distillation flask around half to two third of its volume. Add some pieces of porcelain to avoid bumping. Thermometer inserted into cork and fixed to flask. Liquid get heated gradually. It began to boil after some time. Vapor rise up and pass down the side arm into condenser. Vapor condensed and collected into receiver. distillation must occur slowly as all vapor get condensed to liquid in condenser. 20 drop in minute Distillation should be continued until a small volume of liquid remain in flask.

14. Application : Used for preparation of distilled water and water for injection. Volatile oil and aromatic water prepared by this method. Used in purification of organic solvent. Used in separation of volatile and non volatile material from mixture.

15. Flash distillation It’s a process in which entire liquid get vaporized (flash) by passing feed from high pressure zone to low pressure zone. Also called as equilibrium distillation as separation will done at liquid and vapour phase are in equilibrium.

16. Principle : When hot liquid mixture is allowed to enter from high pressure zone to low pressure zone, entire liquid mixture get vaporized. The process called as flash vaporization. During this process chamber get cooled because of sudden drop in boiling point. Because of cooling, less volatile component condenses and converted into liquid where more volatile substance remain as vapor form. Liquid and vapor kept in contact with each other for some time to achieve equilibrium. The liquid fraction collect separately. The vapor are further condense and collect separately.

17. Construction : It consist of pump which connect to feed tank. Pump help in pumping feed into heating chamber which having some heating mechanism. Other end of pipe directly introduced into vapor – liquid separator through pressure reducing valve. Vapor outlet provided at the top of separator. liquid outlet provided at bottom .

18. Working : The feed is pumped through heater at certain pressure. Liquid get heated and enter in liquid – vapor separator through pressure reducing valve. Due to drop in pressure, liquid get flash, and enhance vaporization process which induced cooling. Vapor molecule have high boiling point get condensed. Low boiling point molecule remain as vapor. Liquid feed allowed to remain for sufficient time to get equilibrium. Liquid collected from bottom. Vapor from top side get condensed further to achieve second liquid.

19. Uses : Used in petroleum industry to refined crude oil. Used for separation of liquid component which boil at different temperature. Advantages : Used in continues mode Used to obtain multi component having narrow range boiling point. Disadvantages : If pure component require as product this process not suitable. Not suitable for those component having same volatility.

20. Fractional distillation It’s a process in which vaporization of liquid mixture give rise to mixture of constituent from which desired one is separated. Also called as rectification process Used to separate miscible volatile liquid whose boiling points are close. This method is quite different from simple distillation as in simple distillation vapor directly passed through condenser but here it first goes to fractionating column where partial condensation of vapor occurred.

21. Principle : When liquid mixture is distilled, partial condensation happen in fractionating column. In column, ascending vapor from flask is allowed to come in contact with condensing vapor returning to flask. By condensing vapor and reheating liquid repeatedly, equilibrium between vapor and liquid get achieved. Which help in separation of more volatile component.

22. Construction : Liquid mixture put into round bottom flask. Add porcelain pieces to avoid bumping. Fractionating column fitted at the top. At bottom of flask, heat source provided. Top of column, condenser provided.

23. Working : Let’s assume we have a liquid mixture of X and Y. X is more volatile than Y. Mixture transfer in flask and heated. As temperature rise slowly and mixture get boil. Because of boiling formation of vapor happen. Vapor having more amount of X as Y. Vapor travel into fractionating column. And liquid less volatile Y get condense first. Vapor of X rises more in column and liquid of Y flowing down. Same process repeated for several time. Vapor of X reach to top, from there taken out to condenser and transfer in container after condensation.

24. Uses : For the separation of crude oil this method used like gasoline, diesel oil, paraffine wax. Used for purification of water. Used for separation of acetone and water. Used for separation of specific gas from gas mixture. Used in chemical industry. Disadvantages : Do not used to separate miscible liquid which form azeotropic mixture. (mixture contain 2 or more liquid and all have same boiling point)