Simple and Fractional Distillation

Simple and Fractional Distillation 9/24/2019 Abstract: Distillation is the method in which mixtures of liquids are separated into its pure components via vaporization or condensation. A lot of chemical processes are involved in purification and identification of organic liquids, so distillation plays an important role in chemical industry. This process separates mixture into two or more products that consist of different boiling points through the vaporization of a liquid mixture components and the recycling of countercurrent gas liquid flow in the column. There are many kinds of distillations, but the experiment’s main focus was simple and fractional ones. Mixtures of 10 % and 30 % by volume of aqueous ethanol were distilling by simple and fractional distillation to compare the efficiency of two methods. Data was collected and it showed that fractional distillation was more efficient in purifying ethanol than simple fractional distillation. Introduction: Distillation is a method that uses the differences boiling points of solutions. The boiling point is the temperature at which the vapor pressure of the liquid is equal to the external pressure applied to the surface of the liquid. In simple distillation, a mixture is boiled to change the most volatile component from a liquid into vapor. The vapor rises and passes into a condenser. The condenser is cooled with water so the vapor can condense into liquid. Fractional distillation is used for a precise distillation process. As the mixture is heated, the vapor rises and enters the fractionating column. As the vapor cools, it condenses on the packing material of the column. The heat of rising vapor causes this liquid to vaporize again, moving it along the column and eventually yielding a higher purity sample of the more volatile component of the mixture. Simple distillation 1 is used to make alcohol beverages, perfumes while fractional distillation is widely used in refining oil industry. Distillation has some concepts that are very import including boiling points of liquids, Raoult’s Law, Dalton’s Law and azeotropes. Boiling point occurs when the vapor pressure exceeds the atmospheric pressure which cause the solvent to vapor. According to Raoult’s Law, the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature regarding mole fraction. While, Dalton’s Law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. Lastly, an azeotrope is a mixture of liquids that has a specific boiling point and the vapor composition is exactly the same as the liquid. The purpose of this experiment was to separate 10% and 30 % by volume of aqueous ethanol by using simple and fractional distillation to compare the two distillation techniques to see which one was more efficient in purifying distillates. Chemical structures of the substances that were used in the experiment: ETHANOL WATER H 2O CH2CH3OH O OH H H 2 Results and discussion: The results of the experiment were summarized in the following tables and graphs: Table 1: Fractional distillation for 10 % and 30 % by volume of aqueous ethanol 10 % by volume Volume(mL) 1.0 2.1 3.0 4.0 5.1 6.0 7.2 8.0 9.1 10.0 11.1 12.0 13.0 14.1 15.3 16.2 17.0 18.0 19.0 20.0 22.1 23.1 24.0 24.5 30 % by volume Volume(mL) 2.9 4.5 7.1 8.2 9.0 10.0 11.2 12.0 12.9 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 13.8 13.8 14.0 14.3 14.5 14.7 15.0 15.2 15.4 15.5 16.0 20.0 22.0 23.0 24.0 25.0 B.P.(°C) 73.1 73.2 98.0 98.0 98.0 98.1 98.3 98.2 98.5 98.8 98.8 98.9 98.9 98.9 98.8 98.9 99.0 99.0 99.0 99.0 99.0 99.1 99.1 99.1 3 B.P.(°C) 74.5 76.0 76.5 77.0 78.0 78.2 78.9 82.0 85.1 88.5 89.0 90.0 90.1 91.0 92.1 92.1 93.0 94.0 95.0 98.0 98.1 98.2 98.5 99.0 99.0 99.0 99.0 99.0 99.1 99.1 99.1 99.1 99.2 Table 2: Simple and Fractional distillation for 10 % by volume of aqueous ethanol Simple Distillation Volume(mL) 1.0 2.0 3.5 4.0 5.1 6.0 7.1 8.0 9.0 10.1 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.1 19.0 20.2 21.0 23.0 25.0 26.0 28.0 Fractional Distillation Volume(mL) 1.0 2.1 3.0 4.0 5.1 6.0 7.2 8.0 9.1 10.0 11.1 12.0 13.0 14.1 15.3 16.2 17.0 18.0 19.0 20.0 22.1 23.1 24.0 24.5 T(°C) 88.0 89.0 95.0 96.8 97.9 98.0 98.3 98.5 98.8 98.8 98.9 98.9 98.9 98.9 98.9 98.9 98.9 98.9 98.9 98.9 98.9 99.0 98.9 98.9 98.9 B.P.(°C) 73.1 73.2 98.0 98.0 98.0 98.1 98.3 98.2 98.5 98.8 98.8 98.9 98.9 98.9 98.8 98.9 99.0 99.0 99.0 99.0 99.0 99.1 99.1 99.1 Table 3: Simple and fractional distillation for 30 % by volume of aqueous ethanol Simple Distillation Volume(mL) 1.2 3.0 3.8 5.2 6.0 Fractional Distillation Volume(mL) 2.9 4.5 7.1 8.2 9.0 T(°C) 79.4 81.4 82.1 83.5 83.9 4 B.P.(°C) 74.5 76.0 76.5 77.0 78.0 7.0 8.0 9.1 10.0 11.0 12.0 13.1 14.1 15.0 16.0 17.2 18.0 19.1 20.0 22.2 22.9 24.0 25.0 28.0 85.0 86.0 88.0 90.0 92.0 94.3 95.2 96.9 97.5 98.0 98.1 98.5 98.5 98.5 98.5 98.8 98.8 98.8 98.8 10.0 11.2 12.0 12.9 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 13.8 13.8 14.0 14.3 14.5 14.7 15.0 15.2 15.4 15.5 16.0 20.0 22.0 23.0 24.0 25.0 Graph 1: Fractional distillation for 10 % and 30 % to volume ethanol aqueous 5 78.2 78.9 82.0 85.1 88.5 89.0 90.0 90.1 91.0 92.1 92.1 93.0 94.0 95.0 98.0 98.1 98.2 98.5 99.0 99.0 99.0 99.0 99.0 99.1 99.1 99.1 99.1 99.2 Fractional Distillation of 10 % and 30 % by volume of aqueous ethanol 120 Temperature (°C) 100 80 60 40 20 0 0 5 10 15 20 30 30% 25 ethanol Solution Volume (mL) 10% ethanol Solution Graph 2: Comparison of simple vs. fractional distillation for 10 % by volume of aqueous ethanol Temperature (°C) 105 Simple vs. Fractional Distillation of 10% by volume of aqueous ethanol 100 95 90 85 80 75 70 0 5 10 15 Volume (mL) 20 25 30 Fractional Distillation Simple Distillation 6 Graph 3: Comparison of simple vs. fractional distillation for 10 % by volume of aqueous ethanol Simple vs. Fractional Distillation of 30% by volume of aqueous ethanol 105.0 Temperature (°C) 100.0 95.0 90.0 85.0 Simple Distillation 80.0 Fractional Distillation 75.0 70.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Volume (mL) Looking at graph 1 fractional distillation between the two solutions, the 10 % solution was quickly boiled and vaporized around 73°C and then had a drastic change in temperature from 73°C to 98°C of the volume of 2.0-mL to 3.0 mL, then the temperature plateaued at 4-mL which was 98°C. On the other hand, the 30% solution had a larger volume of the distillate collected around 78°C which is the boiling point of ethanol. The graph showed that the higher concentration of ethanol solution yielded a higher purity volume of distillate. This is expected because the boiling point of ethanol is 78 °C, the 30% solution had more ethanol concentration which gave a larger volume of distillate around that temperature. At 98°C, all the ethanol had already vaporized, the mixture now had mostly water, so water began to vaporize around its boiling point. At around 79°C, the volume of distillate collected for the 10% solution was deceasing, but the temperature kept increasing up to 99°C but never reached 100°C. 7 Graph 2 and 3 showed that fractional distillation was more efficient in collecting distillation regardless of the percent of concentration of the volatile. Both graphs showed a drastic changed in temperature of the 30 % solution after 78°C. The distinct jump of temperature showed the point where ethanol was all vaporized and the system switched to collect water. The clean break in the graph showed the period where water was heating up almost 100°C and plateaued. While in simple distillation the temperature increased gradually over a larger volume which made it harder to separate the two substances. The experiment also showed that the solutions’ temperature in all experiments never reached 100 °C because of the barometric pressure was 76.5 mmHg which was different than standard one. During the experiment, it was very important to control the mantle’s temperature to make sure that the heat supplying to the RBF was consistent. However, during the beginning of collecting the distillate of fractional distillation process, it could be possible that the temperature was too high that the data weren’t accurate. However, the temperature was monitor very closely for the rest of the experiment and the final data showed reasonable results. Also, it was impossible to get pure ethanol with fractional distillation because the mixture of ethanol and water contained less than 95.6% of ethanol1. The particular mixture of ethanol and water boiled as if it were a pure liquid and had a constant boiling point which created a constant boiling mixture an azeotrope. Therefore, the liquid collected by fractionating column cannot be pure ethanol. The experiment showed the temperatures where ethanol started to vapor, or boil were always different than 78.5 °C. Although both techniques distilled ethanol from the mixture very well, the results of the experiment showed that fractional was more effective in distill ethanol from the aqueous ethanol than simple distillation. Experiment: 8 Simple distillation: ethanol 10%. The simple distillation apparatus was set up according to the diagram provided in the lab manual1. To a 100-mL round bottom flask (RBF) equipped with a boiling chip was added a mixture of 3.5-mL of 10% ethanol and 31.5-mL of water. Attach the RBF to a distilling head, west condenser, bend vacuum adapter, thermometer, and thermometer adapter in a vertical position. Then, the apparatus was clipped with Keck clips to prevent any leakage of vapor. A thermometer was placed into the distilling head with the support of thermometer adapter. The thermometer was placed below the entrance of the condenser to ensure the accuracy of t temperature of the vapors. Another stand was used to keep the whole apparatus from flipping over. After everything was set up, heat mantle was placed underneath the RBF. The solution was heated to boil, and the vapor went through the condenser and was collected in a graduated cylinder. The first 1 mL of distillate was collected on a watch glass to perform a flame test and gave a positive result. The distillate volume collected in the receiving cylinder versus the temperature on the thermometer was monitored. For every 1° C the temperature rose, the volume in the receiving cylinder was recorded. The voltage box was set at 40% power to start, then it was slowly increased to 65 % power. Over the course of 1 h while maintain that voltage, 28 mL of distillate was collected. The regulator was turned off and the apparatus was removed from heating mantel. The apparatus, heating mantel and thermometer were allowed to cool. All data was recorded. The remaining distillate was placed in the organic waste and all parts of the apparatus were cleaned and put away. The same procedure was carried out for the second solution with 11.1-mL of 30% ethanol and 25.9-mL water. Fractional distillation: 9 The same apparatus as above was set up for factional distillation but using a fractional column with burl saddles inside was added between the distilling head and the RBF. The experiment was carried out with 2 solutions: solution 1: 3.7-mL of 10 % ethanol and 33.0-mL water, solution 2: 3.7-mL of 30 % ethanol and 33.0-mL water. The temperatures and volume of distillate were recoded closely. Conclusion: The experiment was successful in separate ethanol from the mixture with water by simple and fractional distillation. The data collected in the experiment showed that fractional distillation was more effective because the vapor was able to condense so many times in the fractional column. In addition, the experiment also showed that pure ethanol could not be distillated from a mixture that had less than 95.6% of ethanol. 10