UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA THERMOFLUIDS LABORATORY (CGE 536)

GROUP MEMBERS : AMIRA BINTI KORMAIN (2014851022) FARHAN HAIRI BIN KASSIM (2014204678)MOHD ZAIDI BIN MOHD RADZALI (2014678172)NURULTHAQIFAH BINTI BAHARUM (2014870248)EXPERIMENT :VAPOUR LIQUID EQUILIBRIUM DATE PERFORMED :13th march 2015SEMESTER : 3PROGRAMME : EH 243GROUP : GROUP 8

No.TitleAllocated Marks (%)Marks

1Abstract/Summary5

2Introduction5

3Aims/Objectives5

4Theory5

5Apparatus5

6Procedures10

7Result10

8Calculations10

9Discussion 20

10Conclusion10

11Recommendations5

12References5

13Appendices 5

TOTAL MARKS100

Remarks:

Checked by:

Date:

LIST OF TABLES

TABLESTITLE PAGE1Vapor Liquid Equilibrium Data 102 Temperature and mole fraction of methanol 113Mole fraction of methanol 164Composition of methanol in mole fraction 17

LIST OF FIGURES

FIGURETITLE PAGE1 Pxy diagram 52 Txy diagram 63Txy diagram at different total pressure 64Refractometer 75Vapour Liquid Equilibrium Unit 7

TABLE OF CONTENT

No.TitlePages

1Abstract3

2Introduction4

3Aims/Objectives4

4Theory4

5Apparatus7

6Procedures8

7Results10

8Calculations13

9Discussion 18

10Conclusion19

11Recommendations19

12References20

13Appendices 21

ABSTRACT

The experiment was conducted to construct an equilibrium curve for the methanol-water system at atmospheric pressure. The experiment was carried out by using SOLTEQ Vapour Liquid Equilibrium (VLE) unit. A mixture of methanol-water with known composition is at first bolstered into the evaporator. At the point when the heater is exchanged on, the mixture will begin to boil. The mixture vapor will ascend and will be chilled off by the condenser at the top of the evaporator. As the vapor begins to consolidate, the liquid falls once more into the evaporator. The system would achieve a balance state when the temperature stays consistent. Vapor and liquid samples are taken to determine their composition. Toward the end of the investigation, a graph of mole fraction of vapor against mole fraction of liquid and a chart of temperature against mole fraction of liquid and vapor were plotted. This equilibrium curves at atmospheric pressure for binary system specifically methanol and water obviously demonstrates the relationship between vapor and liquid at equilibrium and at atmospheric pressure. It can be said that from the graphs, the relationship between vapor and liquid at equilibrium and at atmospheric pressure is linear. The experiment was viewed as a success as all the objectives were accomplished.

1.0INTRODUCTIONThe understanding of phase equilibrium, and vapor-liquid equilibrium in particular is important for many process engineering applications. These processes usually involve a combination of two immiscible liquids of combination of liquid and gas. The ability to be able to recognize when these phases are in equilibrium with each other and also calculating the variables is especially useful for real life applications.

2.0OBJECTIVESThe objective of this experiment is to construct an equilibrium curve for the methanol-water system at atmospheric pressure.

3.0 THEORY3.1 Introduction of Vapor-Liquid EquilibriumA vapor/liquid mixture of two components could be considered and placed in a closed container and the system is hold at constant temperature. For instance, a mixture of methanol and water were introduced into the system for the analysis. The composition of the two phases will slowly change as they distribute themselves between liquid and vapor phases through vaporization and diffusion, and eventually the system will approach equilibrium state (Sandler, 1999). This state can be determined or verified when successive readings of temperature, liquid, liquid and vapor mol fractions are identical. The composition of the liquid and vapor phases and the pressure of the system are fixed at this point and producible according to the phase rule. If the 2-phase system is considered to be ideal, the composition of both phases at thermodynamic can be given by Raoults law (Oremusov, 2007): (1)Where pi is the partial pressure of the component i above the solution surface, pi0 are the pressures of the pure component, and xi is the molar fraction of component i. The total pressure of the gaseous phase is given by Daltons Law (Oremusov, 2007):(2) (3)The intensive properties of and relationships between them is heavily concerned when applying thermodynamics to phase equilibrium, and therefore the condition necessary to determine the equilibrium state is specified by the phase rule.

3.2 Pxy and Txy DiagramThere are four intensive variables which is our concern in studying vapor-liquid equilibrium in a binary system; temperature, pressure, a single liquid mol fraction, and a single vapor mol fraction. The composition of a phase in a binary system can be determined with only a single mol fraction due to the condition that the total mol fraction must equal to one. The maximum numbers of intensive variable that can be specified are only two and occurs only when a single phase is present .when phase rule is applied to binary system.By holding one variable constant, the representation of phase behavior on a two-dimensional plot can be accomplished as three variables are required to describe the state of a single phase. As such, three different type plots are possible for the binary system. The Pxy diagram places x and y as functions of pressure at constant temperature while in Txy diagram, x and y are functions of temperature at constant pressure. The xy diagram puts x versus y at constant pressure with temperature as parameter along the curve. The span of entire range of fractions are found to be enveloped on Txy and Txy diagrams, thus rendering the PT plot to be of little use unless we are concerned with the equilibrium near the critical region (Saad Al-Shahrani).

Figure 1: Pxy diagram

Figure 2: Txy diagramBased on Figure 1, at equilibrium, the pressure P1 is equal for each phase and the liquid and vapor curves are tied together by the tie line. Thus, the equilibrium and composition of x1 and y1 are obtained from the intersection of the phase by the line. By specifying two variables for the two- component, two-phase system as per the phase rule, the other variable can be determined by choosing either one. If the pressure is increased at constant temperature to PDP, called the dew point, the composition z will begin to form liquid phase (Saad Al-Shahrani). In Figure 2, the Txy diagram is characterized by temperature instead of pressure.

Figure 3: Txy diagram at different total pressureIn Figure 3, the Txy diagram shows that for the same system, the p2 will be greater than p1. The vapor liquid equilibrium temperatures are higher at p2 than at p1 and the phase equilibrium lines at higher pressure are usually closer together (Saad Al-Shahrani).

4.0 APPARATUS SOLTEQ Vapour Liquid Equilibrium Unit, refractometer, beaker, measuring cylinder, methanol, deionized water.

Figure 4 Refractometer

10897654321Figure 5 Vapour Liquid Equilibrium Unit

1. Condenser6. Pressure Relief Valve

2. Evaporator7. Control Panel

3. Bottom Sample Collector8. Top Sample Collector

4. Cooling Water Supply9. Rotameter

5. Cooling Water Drain10. Hetaer

5.0 PROCEDURE1) The general start-up procedure was performed.2) 12-L of pure methanol and 5-L of deionized water was prepared.3) Valve V8 was opened.4) 0.1-L of methanol and 3-L of water was poured into evaporator through valve V1. Valve V1 was closed.5) Valve V13 and V14 were opened at the level sight tube. The liquid level was make sure to be above the safety line on the level sight tube. Valve V13 and V14 were closed back.6) Valve V10 was opened and adjusted to allow about 5 L/min of cooling water to flow through the condenser.7) The temperature controller TIC-01 was set to about 100. The heater was switched on.8) The temperature rise in TIC-01 was observed. The liquid in the evaporator has begun to boil when the temperature at TI-02 started to increase sharply. The pressure at PI-01 was observed. All temperature and pressure were waited to stabilize at a steady state value.9) The evaporator pressure and the liquid and vapour temperatures was recorded.10) A liquid and vapour sample from the unit were collected. The samples were analysed to determine their compositions.11) The heater was switch off and valve V11 was opened to allow cooling water to flow through the cooling coil in the evaporator.12) The temperature at TI-02 was waited to drop significantly to signify that boiling has sopped. Valve V11 was closed.13) An additional 0.2L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There is now about 0.3L methanol and 3-L water in the evaporator. Steps 5 to 12 above was repeated.14) An additional 0.2-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There is now about 0.5-L methanol and 3-L water in the evaporator. Steps 5 to 12 above was repeated.15) An additional 0.5-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There is now about 1-L methanol and 3-L water in the evaporator. Steps 5 to 12 above was repeated.16) An additional 1-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There is now about 2-L methanol and 3-L water in the evaporator. Steps 5 to 12 above was repeated.17) An additional 1-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There is now about 3-L methanol and 3-L water in the evaporator. Steps 5 to 12 above was repeated.18) Valves V2 and V3 were opened to drain all liquid from the evaporator.19) 2-L methanol and 1-L water was poured into the evaporator through valve V1. Valve V1 and V8 were closed. Steps 5 to 12 above was repeated.20) An additional 1-L of methanol was poured into the evaporator through valve V1. Valves V1 and V8 were closed. There is now about 3-L methanol and 1-L water in the evaporator. Steps 5 to 12 above was repeated.21) An additional 2-L of methanol was poured into the evaporator through valve V1. Valves V1 and V8 were closed. There is now about 5-L methanol and 1-L water in the evaporator. Steps 5 to 12 above was repeated.22) The general shut-down procedures was performed.

Sampling Procedures1) Vapour sampling from the condenser.i. Vent valve V6 was ensure to be opened and drain valve V7 was closed.ii. Valve V5 was slowly open to allow some condensed vapour from condenser to flow into the top sample collector. Valve V5 was closed.iii. Valve V7 was opened to collect the sample in a sampling vial.iv. The cap on the vial was immediately closed and the vial was immersed in cold water.2) Liquid sampling from the evaporator.i. Vent valve V4 was ensure to be opened and drain valve V3 was closed.ii. Valve V12 was opened to allow cooling water to flow through the bottom sample collector.iii. Valve V2 was slowly open to allow liquid from evaporator to flow into the sample collector. Valve V2 was closed.iv. Valve V3 was opened to collect the sample in a sampling vial.v. The cap on the vial was immediately closed and the vial was immersed in cold water.

6.0 RESULTS

Volume of Water (L)Volume of Methanol (L)Temperature (C)RI (nD)Mole Fraction

LiquidVaporLiquidVaporLiquid(X)Vapor(Y)

3.00.193.098.31.33371.33490.01950.0195

3.00.389.394.31.33451.34070.05670.0570

3.00.587.592.21.33521.34180.09200.0925

3.01.083.386.21.33791.34100.17250.1729

3.02.079.982.81.33941.33870.30580.3056

3.03.077.878.11.34101.33640.41220.4108

1.02.072.773.71.34151.33480.63080.6276

1.03.071.072.01.34071.33330.76570.7614

1.05.069.370.11.33711.33260.92180.9187

Table 1: Vapor Liquid Equilibrium Data

Temperature (C)Mole Fraction

Liquid (X)Vapor (Y)Liquid (X)Vapor (Y)

93.098.30.01950.0195

89.394.30.05670.0570

87.592.20.09200.0925

83.386.20.17250.1729

79.982.80.30580.3056

77.878.10.41220.4108

72.773.70.63080.6276

71.072.00.76570.7614

69.370.10.92180.9187

Table 2: Temperature and mole fraction of methanol

Graph 1: T-xy diagram for methanol-water system

Graph 2: X-Y equilibrium

7.0 CALCULATIONS

Density of water (H2O) = 1 g/mlMolecular weight of water (H2O) = 18 g/molDensity of methanol (CH3OH) = 0.79 g/mlMolecular weight of methanol (CH3OH) = 32.04 g/ mol

Number of mole = [Volume]

Moles of Water (H2O)

Volume of 3 L (3000 mL)Number of moles = (3000 ml)= 166.667 mol

Volume of 1 L (1000 mL)Number of moles= (1000 ml)= 55.556 mol

Moles of Methanol (CH3OH)

Volume of 0.1 L (100 mL)Number of moles= (100 ml)= 2.466 mol

Volume of 0.3 L (300 mL)Number of moles= (300 ml)= 7.397 mol

Volume of 0.5 L (500 mL)Number of moles= (500 ml)= 12.328 mol

Volume of 1 L (1000 mL)Number of moles= (1000 ml)= 24.657 mol

Volume of 2 L (2000 mL)Number of moles= (2000 ml)= 49.313 mol

Volume of 3 L (3000 mL)Number of moles= (3000 ml)= 73.970 mol

Volume of 5 L (5000 mL)Number of moles= (5000 ml)= 123.283 mol

Mole Fraction of Methanol (CH3OH)

Volume of Water (L)Volume of Methanol (L)Mole of Water (mol)Mole of Methanol (mol)Moltotal (mol)Mole fraction of WaterMole fraction of Methanol

3.00.1166.6672.466169.1330.9850.0146

3.00.3166.6677.397174.0640.9580.0425

3.00.5166.66712.328178.9950.9310.0689

3.01.0166.66724.657191.3240.8710.1289

3.02.0166.66749.313215.9800.7720.2283

3.03.0166.66773.970240.6370.6930.3074

1.02.055.55649.313104.8690.5300.4702

1.03.055.55673.970129.5260.4290.5711

1.05.055.556123.283178.8390.3110.6894

Table 3: Mole fraction of methanol

Composition of Methanol (CH3OH) in mole fraction

Temperature (C)Mole FractionRefractive Index, RI (nD)Mole Fraction

LiquidVaporWater (H2O)Methanol (CH3OH)LiquidVaporMethanol (Liquid)XMethanol (Vapor)Y

93.098.30.9850.01461.33371.33490.01950.0195

89.394.30.9580.04251.33451.34070.05670.0570

87.592.20.9310.06891.33521.34180.09200.0925

83.386.20.8710.12891.33791.34100.17250.1729

79.982.80.7720.22831.33941.33870.30580.3056

77.878.10.6930.30741.34101.33640.41220.4108

72.773.70.5300.47021.34151.33480.63080.6276

71.072.00.4290.57111.34071.33330.76570.7614

69.370.10.3110.68941.33711.33260.92180.9187

Table 4: Composition of methanol in mole fraction

8.0 DISCUSSION

Vapor-liquid equilibrium (VLE) undergirds the bulk of industrial separation processes, particularly in the distillation processes. It will be consider only binary (two components) mixture for simplicity. The composition of the liquid phase will be designated by the mole fraction of the more volatile component (lower boiling point), represented by X meanwhile the mole fraction of the vapor represented by Y. When the liquid is heated to its boiling point, the vapor will produce, in general, have a different composition than the liquid. Thus, boiling the mixture produces a partial separation of the component. If the vapor is collected, it can be condensed and boil again to further change the composition.The T-xy diagram represents the data for two-component (binary) system. T-xy diagram is convenient for analysis the binary distillation system. There are two main factors that make the vapor and liquid compositions different at equilibrium which are the pure component vapor pressures and the no idealities in the liquid phase. The refractive index for vapor and liquid is recorded. The composition of methanol in the liquid and vapor is determined based on the refractive index.The mole fraction for methanol and water are determined by calculation by using the density of each compound. The density of methanol is 0.79 g/ml whilst the density of water is 1 g/ml. From the volume of methanol and water that had been used, the mass of the methanol and water can be calculated by using the density of the methanol and water.In the experiment, the volume of the water is kept constant at 3.0L and then being mixed with different volume of methanol of 0.1L, 0.3L, 0.5L, 1.0L, 2.0L and 3.0L. The temperature of the liquid methanol is decreased from 93.0C to 77.8C whereas the temperature of the vapor methanol also decreased from 98.3C to 78.1C. The refractive index for liquid methanol is decreased from 1.3337 to 1.3410 while the refractive index for vapor methanol also decreased from 1.3349 to 1.3364. In addition to that, the mole fraction of the liquid methanol is increased from 0.0195 to 0.4122 meanwhile the mole fraction for vapor methanol also increased from 0.0195 to 0.4108.On the other hand, in the second experiment, the volume of the water is kept constant at 1.0L before being mixed with different volume of methanol of 2.0L, 3.0L and 5.0L. The temperature of liquid methanol dropped from 72.7C to 69.3C and the temperature of vapor methanol also dropped from 73.7C to 70.1C. The refractive index for liquid methanol is decreased from 1.3415 to 1.3371 while the refractive index for vapor methanol also decreased from 1.3348 to 1.3326. Moreover, the mole fraction of liquid methanol is elevated from 0.6308 to 0.9218 and the mole fraction of vapor methanol also elevated from 0.6276 to 0.9187.Through the X-Y equilibrium graph, the mole fraction of liquid methanol is directly proportional to the mole fraction of vapor methanol as it is both increased. The mole fraction that had been used in the graph is calculated using the mole fraction formula Methanol is a volatile liquid. During the experiment, putting the methanol in the beaker without closing the beaker can cause the methanol to vaporize slowly. The methanol is added before the temperature of the heater is lower than 50C. This will cause error to the experiment and lead to inaccurate readings.

9.0 CONCLUSIONThe conclusion for this experiment is the experiment is successfully carried out. The relationship between vapour and liquid methanol at the normal pressure can be determined successfully. The maximum mole fraction that can be achieved in this experiment is 0.6894. The objective of this experiment is construct the equilibrium curve for the methanol-water system at atmospheric pressure. From the result of this experiment, the composition of methanol in liquid is higher than in vapour. The composition of methanol in liquid and vapour is increase as the volume of methanol in mixture is increase. When the objective of this experiment is achieved, it can be concluded that this experiment is successfully done.

10.0 RECOMMENDATION Make sure that the heater is operating correctly before running the experiment. Before starting the experiment, make sure that the water level is enough or at least fill half of the evaporator. Make sure that the cooling water is open when running the experiment. Always cool down the sample before test it by using refractometer.

11.0 REFERENCES

S. I. Sandler. (1999). Chemical and Engineering Thermodynamics, John Wiley &Sons, Third Edition.Saad Al-Shahrani. (n.a.). Separation Process. Retrieved 18th March 2015 from http://www.kau.edu.sa/Files/0008595/Files/59993_Lecture%206.ppt J. Oremusov. (2007). Manual for laboratory practice in physics for students of pharmacy, Department of Physical Chemistry, Faculty of Pharmacy, Comenius University, Bratislava.

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