SYNTHESIS OF p-NITROACETANILIDE

BACHELOR OF ENGINEERING (HONS) CHEMICALCHE 465 CHEMICAL ENGINEERING LABORATORY I

VAPOR-LIQUID EQUILIBRIUM UNIT

PREPARED BYEH2202BHAFIZAH BINTI OSMAN (2013686936)ILI NADIA ISMAIL (2013212084)JAILANI BIN ZULKIFLI (2013450328)JEALONOVIER SAYAS ANAK JEMON (2013886766)MARLISSA BINTI AZEMI (2013815618)

PREPARED FORMISS SITINOOR ADEIB BINTI IDRISVAPOR-LIQUID EQUILIBRIUM UNITABSTRACTExperiment of liquid vapour equilibrium (VLE) unit is used to study about the binary system. The mixture used is methanol-water mixture. The first objective of this experiment is to construct the equilibrium curve for the methanol-water system at atmospheric pressure. Secondly, the objective is to investigate the relationship between vapour and liquid at equilibrium and thirdly, to determine the composition of methanol at liquid and vapour phase. The quantity of methanol is added for a few times until the quantity of methanol is 5liters and water is 1litres. The mixture is heated until it boiled. The constant temperature is taken and at constant temperature, the liquid vapour sample is drain and the refractive index is read by using the refractometer.

INTRODUCTIONIn industry, the most of the separation process used the vapour liquid equilibrium concept that applicable for the binary system. It used the concept based on the differences of the boiling point. In the experiment of liquid vapour equilibrium (VLE) unit the pressure used may be constant (at atmospheric pressure) or at differences pressure. In this experiment, the pressure used is atmospheric pressure and it means that the pressure is constant. The mixture used is methanol-water mixture.For the separation process between methanol and water, the substance with low boiling point will vaporised first. In this mixture, water has high boiling point compare to methanol. This is because water has the molecule that attract with the strongest hydrogen bond. Thus, methanol will vaporise first. There are a few laws that can be used to relate with this experiment. Raoults Law state that the vapour pressure of a solution depends on the mole fraction of a solute added to the solution. This law only used for the ideal mixture and for the ideal solution. Then, Daltons Law state that the total pressure exerted by the mixture of non-reactive gas is equal to the sum of the partial pressure of the partial pressure of gases itself. For this experiment, Antoine equation is used to describe the relation between vapour pressure and temperature for pure components.The vapour liquid equilibrium unit is used for any binary system and used the concept of boiling point. In this experiment, the mixture of methanol-water of unknown composition is fed into the evaporator. When the heater is switch on, the mixture started to boil until it vaporised. The condenser is placed at the top of the evaporator. It is used to cooled down the vaporised mixture and prevent the mixture from further vaporised. As the vapour start to condensed, the liquid will fall back into the evaporator. At constant temperature reaches, the system will stabilized and reached equilibrium. At this point, the sample is taken to determine the refractive index by using the refractometer. The composition is obtained by using the refractive index.

OBJECTIVESThe objectives of this experiment are; to investigate the relationship between vapor and liquid at equilibrium; to construct an equilibrium curve for the methanol and water system at atmospheric pressure; and to study the effect of initial mixture composition upon boiling temperature and vapor-liquid phase compositions.

THEORYIn vapor liquid equilibrium, there are two laws related to the experiment which is Raoults law and Daltons law. Besides, Antoine equation is also used in finding the vapor pressure. After getting the vapor pressure from Antoine equation, used the equation from Raoults law to find the mole fraction. Raoults law is usually used for predicting the vapor liquid equilibrium for an ideal solution in equilibrium with an ideal gas mixture from the pure component vapor pressure. It states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperaturescaledby the mole fraction of the solvent.Psolution=XsolventPosolventWherePsolution = equilibrium partial pressurePosolvent = vapor pressure of solvent in pure stateXsolvent = mole fractionMeanwhile, Daltons law states that the total pressure of a gas or vapor mixture in a container is the sum of the partial pressures of the individual gases or vapor mixture in the container. It can be stated asPtotal= P1+ P2+ P3+ ... PnAntoine equation is a vapor pressure equation and describes the relation between the vapor pressure and temperature for pure components. The basic form of the equation is:

Where P = the absolute vapor pressure of a substance T = the temperature of the substanceA, B, C = substance specific coefficient (i.e. constants or parameters)Temperature versus x and y diagram (Txy) and x versus y diagram are the VLE diagrams used to represent the data for binary systems. X represents the liquid composition and Y represents the vapor composition where both are in mole fraction.

Figure 1: Boiling Point Diagram for Methanol/Water

Figure 2 : Equilibrium DiagramThe curved line is called the equilibrium line and describes the compositions of the liquid and vapor in equilibrium at some fixed pressure.

MATERIALSDistilled water and methanol

APPARATUSRefractometer; SOLTEC Vapor Liquid Equilibrium Unit ( Model : BP16); Sample collector; Dropper; 1000 mL and 2000 mL beaker; 500 mL and 50 mL measuring cylinder

EXPERIMENTAL PROCEDURE1. The general start-up procedures were performed.1. About 12 L of pure methanol and 5 L deionized water were prepared.1. Valve V8 was opened.1. 0.1 L methanol and 3 L water were poured into the evaporator through valve V1 and Valve V1 was closed.1. Valve V13 and V14 were opened at the level sight tube. The liquid level was ensured above the safety line on the level sight tube. Valve V13 and V14 were then closed back.1. Valve V10 was opened and adjusted to allow 5 L/min of cooling water to flow through the condenser.1. The temperature controller TIC-01 was set to about 100C and the heater was switched on.1. Temperature rise in TIC-01 was observed. The liquid in the evaporator begins to boil when the temperature at TI-02 starts to increase sharply. The pressure at PI-01 was observed. All temperature and pressure were left to stabilize to a steady state value.1. The evaporator pressure and the liquid and vapour temperatures were recorded.1. A liquid and vapour samples from the unit were collected using the standard collection procedure. The samples were analysed to determine their composition.1. The heater was switched off and valve V11 was opened to allow cooling water to flow through the cooling coil in the evaporator.1. The temperature at TI-02 was observed until it drops significantly to signify that boiling has stopped. Valve V11 was closed.1. An additional 0.2 L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 0.3 L methanol and 3 L water in the evaporator. Steps 5 to 12 above were repeated.1. An additional 0.2 L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 0.5 L methanol and 3 L water in the evaporator. Steps 5 to 12 above were repeated.1. An additional 0.5 L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 1 L methanol and 3 L water in the evaporator. Steps 5 to 12 above were repeated.1. An additional 1-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 2-L methanol and 3-L water in the evaporator. Steps 5 to 12 above were repeated.1. An additional 1-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 3-L methanol and 3-L water in the evaporator. Steps 5 to 12 above were repeated.1. Valve V2 and V3 were opened to drain all liquid from the evaporator.1. 2-L methanol and 1-L water were poured into the evaporator through valve V1. Valve V1 was closed. Steps 5 to 12 above were repeated.1. An additional 1-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 3-L methanol and 1-L water in the evaporator. Steps 5 to 12 above were repeated.1. An additional 2-L methanol was poured into the evaporator through valve V1. Valve V1 was closed. There was now about 5-L methanol and 1-L water in the evaporator. Steps 5 to 12 were repeated.1. The general shut-down procedures were performed.

RESULTSTable 1 : Calibration Table for Methanol-WaterWater (ml)Methanol (ml)Mol WaterMol MethanolMol TotalMethanol Mol FractionRefractive Index

1000.55600.55601.3308

910.5000.0250.5250.0481.3349

820.4440.0490.4930.1001.3385

730.3890.0740.4630.1601.3410

640.3330.0990.4320.2291.3417

550.2780.1230.4010.3071.3420

460.2220.1480.3700.4001.3412

370.1670.1730.3400.5091.3401

280.1110.1980.3090.6411.3361

190.0560.2220.2780.7991.3350

01000.2470.2471.0001.3341

Table 2 : Vapor-Liquid Equilibrium TableComponentTemperature (C)Refractive Index (nD)

WaterMethanolVaporLiquidVaporLiquid

3.00.195.399.01.33491.3345

3.00.390.195.41.33901.3350

3.00.587.692.81.34051.3354

3.01.083.986.31.34101.3375

3.02.080.183.51.33791.3390

3.03.078.378.91.33621.3410

1.02.073.073.51.33491.3416

1.03.071.872.01.33331.3407

1.05.070.170.01.33201.3382

Figure 3 : Graph of Refractive Index Versus Mole Fraction

Figure 4: Graph of Vapor-Liquid Equilibrium

Figure 5: T-XY Diagram of Methanol-Water System

CALCULATIONS*Note that the vapor pressure of methanol is 97.658 mmHg.From Antoines Law: PA

From Raoults Law: PA . P A where x (vapor mol fraction) can be written as y (liquid mol fraction)Therefore,

Antoines Constant:

Calculation of Methanol Mol Fraction in Vapor State.When T = 95.3.0C (368.3 K)

0.032

When T = 90.1C (363.1 K)

0.026

When T = 87.6 C (360.6 K)

0.024

When T = 83.9C (356.9 K)

0.021

When T = 80.1C (353.1 K)

0.018

When T = 78.3C (351.3 K)

0.017

When T = 73.0C (346.0 K)

0.014

When T = 71.8C (344.8 K)

0.014

When T = 70.1C (343.1 K)

0.013

Calculation of Methanol Mol Fraction in Liquid State. When T = 99.0C (372.0 K)

0.035

When T = 95.4C (368.4 K)

0.031When T = 92.8C (365.8 K)

0.029

When T = 86.3C (359.3 K)

0.023

When T = 83.5C (356.5 K)

0.021

When T = 78.9C (351.9 K)

0.018When T = 73.5C (346.5 K)

0.015

When T = 72.0C (345.0 K)

0.014

When T = 70.0C (343.0 K)

0.013

Sample Calculation of Methanol Mol Fraction from Calibration Table.Water : 9mLMethanol : 1mL

Mole of water:

Mole of methanol:

Therefore,

= 0.799DISCUSSIONSVapour-liquid equilibrium is commonly used in distillation process. This is involved of binary mixture which is methanol and water for simplicity. X represented the mole fraction of liquid and y represented the mole fraction of gas. This information is tabulated in a graft which is equilibrium x-y diagram.Two-component (binary) system can be represented by T-xy Diagram. Binary system is easier to analysis by T-xy diagram. There are two main factors that make the vapour and liquid compositions different at equilibrium which are the pure component vapour pressures and the no ideal ties in the liquid phase. The refractive index for vapour and liquid is recorded. The composition of methanol in the liquid and vaporise determined based on Antoine equation.For the first experiment, the volume of water is constant, which is 3L but the volume of methanol is increased from 0.1L to 3L. Based on the experiments data, the temperature of liquid mixture decrease from 95.3C to 78.3C and the temperature of vapour mixture decreased from 99C to 83.5C. By comparing the equilibrium line of experiment with the ideal equilibrium line, we only got the slightly line compare to the literature line. This occur maybe due to the error like putting the methanol in the beaker without closing and cause the methanol vaporise because methanol is very volatile.The graph of refractive index versus mol fraction is the calibration curve of this experiment. The calibration curve is very important to determine the unknown mole fraction from the sample. T-xy diagram can be plot with help of the calibration curve. But, we use the Antoine formula instead of this method.

CONCLUSION AND RECOMMENDATIONSFor the conclusion, the experiment was conducted successfully with some mistake or error. The relationship of liquid and vapour at equilibrium is determined via the graft of equilibrium. The composition of methanol is higher in the vapour compare to liquid and vice versa for the water. This is because the methanol is volatile than the water, so methanol is easy to vaporised compare to water. The experiment is conducted in a constant pressure which is atmosphere pressure (1 atm). Water has higher boiling point than the methanol due to lower vapour pressure. The objectives of the experiment are achieved, it can be concluded that the experiment was successfully done.On the other hand, to achieve more accurate and better results, some recommendations have to be taken into account such as before starting the experiment makes sure that there is no liquid inside the VLE unit and draw out all the liquid inside it if the liquid is still there. Besides, ensure that the liquid is enough at all time to fully submerge the heater. Furthermore, before started the draining always switch off the heater cool down the liquid. Also, make sure to perform the general start up and shut down before and after the experiment is carried out. Other than that, safety precaution should be taken seriously before entering the pilot plant. For instance, lab coat with long sleeve as well as the safety cap should be worn before entering the pilot plant and conduct the experiment. These are to avoid any unwanted accidents inside the pilot plant.

REFERENCESi) Skoog, West, Holler & Crouch, Fundamentals of Analytical Chemistry, 8th Ed, Thomson Brooks/Cole, 2004.

ii) Raoults Law, http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Solutions_and_Mixtures/Ideal_Solutions/Changes_In_Vapor_Pressure2C_Raoult's_Law, accessed on 12th April 2014.

iii) Daltons Law of Partial Pressures, http://chemistry.about.com/od/workedchemistryproblems/a/daltons-law-of-partial-pressures.htm, accessed on 13th April 2014.

iv) Vapor-Liquid Equilibria, http://lorien.ncl.ac.uk/ming/distil/distilvle.htm, accessed on 12th April 2014.

v) Antoine Equation, http://www.tau.ac.il/~tsirel/dump/Static/knowino.org/wiki/Antoine_equation.html, accessed on 13th April 2014.

vi) Raoults Law, http://en.wikipedia.org/wiki/Raoult's_law, accessed on 12th April 2014.CHE 465-MISS SITINOOR ADEIB IDRISPage 18