SUMMARY The aim is to observe distillation process of ethanol-water solution and to measure the alcohol content after process in this experiment. 500 ml of solution with an alcohol content of 32% (v/v) is used for this experiment. Temperature values are recorded for every 10 ml alcohol obtained in the flask. The process is repeated in our experiment and for the first process, the data collection process continues until the distillate reaches to 200 ml. The concentration of alcohol is measured for first process by hydrometer.
For the second process, approximately 200 ml of distillate containing 70% alcohol is used and data collection continues until the distillate reaches 150 ml. Finally, the concentration of alcohol is also measured after 2nd process as 82%. INTRODUCTION The objective of this experiment is to distillate the alcohol-water solution into ethanol and water. Distillation is a process of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction.
The basic requirement of distillation is that the components of the liquid solution must have different boiling points. There are some types of distillation methods which are flash distillation, simple batch distillation, simple steam distillation, continuous distillation, vacuum distillation, etc. : Flash distillation It is a single stage process which liquid mixture is vaporized. The vapor and the liquid are come to equilibrium, and these phases are separated. Simple steam distillation This is a separation process at lower temperatures.
This process is often used to separate a high boiling component from small amounts of nonvolatile impurities. Continuous distillation This is a process in which a liquid mixture is continuously fed into the process and separated fractions are removed continuously. Vacuum distillation It is used for some compounds having very high boiling points. Instead of the increasing the temperature too much, lowering the pressure is preferred in this distillation type. In this experiment we used simple batch distillation in order to distillate alcohol-water mixture.
Simple batch distillation This is a separation process which the liquid charge is boiled slowly and the vapors are withdrawn as quickly as vapors form to condenser, where the distillate, condensed vapor, is collected. The first portion of vapor condensed will be the richest in the more volatile component. Vapor-liquid equilibria take an important role in distillation process. Vapor-Liquid-Equilibria (VLE) Constant pressure VLE data is obtained from boiling point diagrams. VLE data of binary mixtures is often presented as a plot, as shown in the figure below.
The curved line is called the equilibrium line and describes the compositions of the liquid and vapour in equilibrium at some fixed pressure. Distillation experiment is applied to two miscible liquids which are ethanol-water, soluble in each other in all ratios. Mixtures of ethanol and water form an azeotrope. Azeotropic mixture: Azeotropic mixture is a solution that forms a vapor with the same concentration as the solution, distilling without a change in concentration. The composition of the liquid phase at the boiling point is identical to hat of the vapor in equilibrium with it, and azeotropes form constant-boiling solutions. The exact composition of the azeotrope changes if the boiling point is altered by a change in the external pressure. Ethyl alcohol and water form an azeotrope of 95. 6% at 78. 1 °C. Azeotropic systems give rise to VLE plots where the equilibrium curves crosses the diagonals. METHODS AND MATERIALS -Distillation apparatus -Alcoholmeter -Graduated cylinder -500 ml of 30% (v/v) water-ethanol mixture Source: Retrieved from http://www. baruch. cuny. edu/wsas/academics/natural_science/chm_1000/6_wine. df The distillation apparatus is for the separation of two miscible liquids by taking advantage of their boiling point differences. The mixture is put in the distillation flask, and a thermometer is located in there. The heater has a knob that is used to adjust the heating. Cold tap water is circulated in the condenser to condense the vapor. First, the ethanol – water mixture was poured into the distillation flask, and boiling chips were used to prevent over bubbling. Then the heater was turned on at a moderate level to prevent fast heating and better separation of the liquids.
After the first drop of the distillate was obtained, the temperature was recorded. Every 10 milliliters, the temperature in the flask was recorded. At the end of the distillation, an alcoholmeter was used to measure the alcohol content of the distillate. 200 milliliters of distillate was distillated again in the same manner to obtain a higher alcohol percentage in the final product. DATA & CALCULATION Notations used: A: Ethanol B: Water XA ? Mole fraction of ethanol in liquid YA ? Mole fraction of ethanol in vapor XB? Mole fraction of water in liquid YB ?
Mole fraction of water in vapor Assumptions: – Pressure is 101,32kPa – Constant physical properties – Condensed fluid drops on the wall of still are neglected Initial data: – 500 mL of ethanol-water mixture is used for the first distillation. – 200 mL of ethanol-water mixture is used for the second distillation. Calculation: XA & YA values can be calculated from the Raoult’s law equation; ? A + ? B = P PA* XA + PB* XB = P ? Since XA + XB = 1 PA* XA + PB* (1- XA)= P XA = (P – PB)/( PA – PB) The PA & PB values were obtained according to the temperature data. (Acland,T. 2011) 1st DISTILLATION: T(? C)PBPAXAYAXBYB 7843,5100,11,0015551,0032540,000,00 78,544,4102,10,9864820,9940760,0135180,005924 7945,3104,10,9527210,9788620,0472790,021138 79,245,7104,90,9395270,9727240,0604730,027276 79,345,9105,30,9329970,9696460,0670030,030354 79,546,3106,20,9185310,9627710,0814690,037229 8047,2108,30,8857610,9467820,1142390,053218 80,548,2110,40,8540190,9305540,1459810,069446 8149,2112,60,8220820,9136050,1779180,086395 81,550,2114,80,7913310,8966130,2086690,103387 8251,21170,7617020,8795810,2382980,120419 82,552,2119,30,7320420,8619480,2679580,138052 353,3121,60,7030750,8438010,2969250,156199 8455,4126,30,6476730,8073540,3523270,192646 8557,7131,20,5934690,7684880,4065310,231512 85,558,8133,70,567690,7491140,432310,250886 8762,4141,50,4920350,687160,5079650,31284 8864,8146,90,4448230,6449320,5551770,355068 88,566,1149,60,4217960,6227870,5782040,377213 9070158,10,3555050,5547310,6444950,445269 The average composition of total material distilled, Yav was measured by using hydrometer as 70%. So the final composition of remaining liquid,X2, can be obtained by material balance using Rayleigh equation: L1X1 = L2X2+ (L1 – L2)Yav 00(0,32) = 300 X2 + 200(0,7) ? X2 = 0,067 That means, 6,7 % of ethanol remained in the distillation still. 2nd DISTILLATION: T(? C)PBPAXAYAXBYB 78,544,4102,10,9864820,9940760,0135180,005924 79,546,3106,20,9185310,9627710,0814690,037229 8047,2108,30,8857610,9467820,1142390,053218 8149,2112,60,8220820,9136050,1779180,086395 8251,21170,7617020,8795810,2382980,120419 8455,4126,30,6476730,8073540,3523270,192646 8864,8146,90,4448230,6449320,5551770,355068 9070158,10,3555050,5547310,6444950,445269 The average composition of total material distilled, Yav was measured by using hydrometer as 82%.
So the final composition of remaining liquid,X2, can be obtained by material balance using Rayleigh equation: L1X1 = L2X2+ (L1 – L2)Yav 200(0,7) = 50 X2 + 150(0,82) ? X2 = 0,34 That means, 34 % of ethanol remained in the distillation still. DISCUSSION In first distillation, according to data obtained boiling point diagram is drawn. This graph can be seen as incomplete because some data is missing in order to complete graph since high temperature is not reached. Moreover, azeotropic point cannot be seen because we are not able to change pressure, so we cannot see that point and forward.
In boiling point diagram graph for second distillation, we omit some of data because fraction is found negative, which is not possible. There may be error due to experimental condition or reflux. CONCLUSION In this experiment, our aim is to learn basic distillation concept and how to take and evaluate our data. We also learnt how to put data into boiling point diagram. In first distillation it is obtained 70% alcohol water solution and in the second distillation it is obtained 78% alcohol water solution.
However, because of negative fraction values, we are not able to put all the data into boiling point diagram. REFERENCES Ackland, T. (2011). Home distillation of alcohol. Retrieved from http://homedistiller. org/ Geankoplis, C. J. (2003). Transport processes and separation process principles. Prentice Hall. Seperation Process. Distillation. Retrieved from http://www. separationprocesses. com/ Distillation/DT_Chp05. htm Wikipedia. Distillation. Retrieved from http://en. wikipedia. org/wiki/Distillation Wikipedia. Azeotropic Distillation. Retrieved from http://en. wikipedia. org/wiki/