Department of Chemical EngineeringUniversity of San Carlos Technological CenterNasipit, Talamban, Cebu City

ChE 411NPhase and Chemical Equilibria of Mixtures

Vapour-Liquid Equilibrium Diagrams(Methyl tert-butyl ether and Methanol binary system)

A project submitted toEngr. Luis K. CabatinganInstructor, ChE 411N

ByUgoy, Marc Dennis Angelo B.

October 19, 2013

AbstractIn separation process of binary mixture the vapour liquid equilibrium diagram is integral to design the separation apparatus. This project objective is to construct the x-y diagram for MTBE-Methanol binary mixture system at constant temperature and to construct vapour liquid equilibrium diagram for the same binary mixture system at various temperatures which is at constant pressure and at various pressures which is at constant temperature. The other objective is to determine the Azeotropic point in which the MTBE-Methanol binary mixture formed at certain point that posed problems in separation processes. The separation process encountered problems during the Azeotropic point which vapour and liquid fraction are equal. A predictive activity coefficient model which is the UNIFAC model was used to determine the activity coefficients of both components in a binary mixture. The vapour pressure equation used was the Wagner 3,6 equation. The total pressure and the vapour composition of MTBE which was used to plot x-y and P-xy diagram was determined using the Raoults law equation for non-ideal solutions. The various temperatures which were used to construct the T-xy diagram were determined by iteration using Wagner 3,6 equation and the Raoults law equation for non-ideal solutions. This was done using the solver add-ins in Microsoft Excel. The x-y, P-xy and T-xy diagram were constructed using the data that was processed. The result, MTBE fraction of x vapor fraction and y liquid fraction formed Azeotropic point at 0.7000~0.7250 in which x=y and T=313.15K. i

TABLE OF CONTENTSChapterTitlePageAbstract --------------------------------------------------------------------------------------------------- iNomenclature --------------------------------------------------------------------------------------------- iiList of Tables --------------------------------------------------------------------------------------------- ivList of Figures -------------------------------------------------------------------------------------------- vI. Introduction ---------------------------------------------------------------------------------- 1Rationale of the Project ---------------------------------------------------------------- 1Related Literature ----------------------------------------------------------------------- 4Binary mixture of MTBE and Methanol ------------------------------------- 4Conventional production of MTBE ------------------------------------------- 4Importance of Vapour-Liquid Equilibrium Diagram ----------------------- 5Theory of Vapour-Liquid Equilibrium Diagram ---------------------------- 6Raoults Law --------------------------------------------------------------------- 9

Activity coefficient model UNIFAC equation -----------------------------10Wagner vapour pressure equation ---------------------------------------------12Azeotrope -------------------------------------------------------------------------13II. The Problem ----------------------------------------------------------------------------------- 15Statement of the Problem --------------------------------------------------------------- 15Objective ---------------------------------------------------------------------------------- 16Scope of Project -------------------------------------------------------------------------- 16Significance of Project ------------------------------------------------------------------ 16III. Methodology --------------------------------------------------------------------------------- 17Tools used -------------------------------------------------------------------------------- 17Procedure ---------------------------------------------------------------------------------- 17Determining of activity coefficients of MTBE and Methanol ------------ 17Constructing xy and P-xy diagram -------------------------------------------- 17Constructing T-xy diagram ---------------------------------------------------- 18IV. Results and Analysis ------------------------------------------------------------------------- 19Conclusion -------------------------------------------------------------------------------- 21V. References ------------------------------------------------------------------------------------- 22VI. Appendix -------------------------------------------------------------------------------------- 23Appendix A:UNIFAC model constant and parameters for MTBE-Methanol binary mixture ------------------------------------------------------------------------------------- 23Appendix B: Data for constructing xy, P-xy and T-xy diagram for MTBE-Methanol binary mixture -----------------------------------------------------------------24Appendix C: Data for determination of vapour pressure as a function of temperature -------------------------------------------------------------------------------- 28

NOMENCLATUREy = Vapour mole fractionx = Liquid mole fractionPvap = Vapour pressure1 = MTBE (Methyl tert-butyl ether)2 = MeOH (Methanol)P = Equilibrium pressure [bar]T = Equilibrium temperature [K]Pc = Critical pressure [bar]Tc = Critical temperature [K]A , B , C , D = Wagner equation parameters of a specific component = Activity coefficient = Molecular weighted segment = Area fractional componentsL = Compound parameter r and zr = Volume parameterq = Surface area parameterUmn = Energy of interaction between groups m and nz = Average coordination number which is taken by 10k = Activity of an isolated group in a solutionR = Group volume parametersQ = Group surface area parametersm = Summation of the area fraction of group mmn = Group interaction parameterXn = Group mole fraction of number of group nR* = Ideal gas constant, 83.14 cc-bar/mol-Kamn = Net energy interaction between groups m and nvk = Summation of occurrence of the functional group

LIST OF TABLESFigure numberTitlePage1. UNIFAC definition of components MTBE and EtOH ---------------------------------- 232. UNIFAC Rk and Qk values for each subgroup -------------------------------------------- 233. UNIFAC Main group interaction parameters, amn in Kelvin ---------------------------- 234. Activity Coefficients at varying composition of liquid MTBE, x1 at constant temperature of 313.15K determined using Modified UNIFAC model ----- 245. P and y1 data at constant temperature of 313.15K ---------------------------------------- 256. T and y1 data at constant pressure of 0.6677 bar ------------------------------------------ 267. Data for determination of Vapour Pressure as a function of temperature ------------- 28

LIST OF FIGURESFigure numberTitlePage1. Schematic diagram of the production of MTBE ----------------------------------------- 52. VLE Diagram of Binary Mixture ----------------------------------------------------------- 73. x-y diagram for the MTBE-Methanol system at a fixed temperature of 313.15K --- 194. The x-y diagram for MTBE-Methanol system at a fixed pressure of 0.6677 bar. --- 195. The Pressure-composition diagram for the MTBE-Methanol system at fixed temperature of 313.15K -------------------------------------------------------------- 206. The Temperature-composition diagram for the MTBE-Methanol system at fixed pressure of 0.6677 bar. ---------------------------------------------------------------------- 20

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THE PROBLEM AND ITS SCOPEINTRODUCTION

Rationale of the ProjectThe separation process depends heavily on both chemical and physical properties of the material needed to be separated. These properties determined the type of separation process. Separation process in the bigger picture was used to transform a mixture of substances into two or more distinct product and because the fundamental part of separation process is manipulating both chemical and physical properties of the elements aimed to be separated and the separated product could differ in chemical properties or physical properties such as size, boiling point and other properties. Bear in mind that almost every element or compound is found to be naturally in an impure state such as mixture of two or more components. Separation applications in the fields of chemical engineering are very important.Separation processes can be essentially be defined as mass transfer that occurs in distillation, absorption, drying, liquid-liquid extraction, adsorption, ion-exchange, crystallization, and membrane processes (Geankoplis, 2003). Mass transfer is important in many areas of science and engineering that occurs when a component in mixture migrates in the same phase or from phase to phase because of difference in certain properties such as boiling point, concentration or component size this justify why separation process manipulate either chemical or physical properties as mentioned above (Geankoplis, 2003)The classification can be based on the mean of separation, mechanical or chemical. The choice of separation depends on the pros and cons of each. Mechanical separations are usually 1

favoured if possible due to the lower cost of the operations as compared to chemical separations. Systems that cannot be separated by purely mechanical means (e.g. crude oil), chemical separation is the remaining solution. The mixture at hand could exist as a combination of any two or more states: solid-solid, solid-liquid, solid-gas, liquid-liquid, liquid-gas, gas-gas, solid-liquid-gas mixture, etc.Distillation is a unit operation or a physical separation process and not a chemical reaction. Commercially distillation has a number of applications. It used to separate crude oil into more fractions, other example is the distillation process used to distillate water to remove its impurities. Distillation process can be divided into two main types of distillation which is batch distillation and continuous distillation. Batch distillation refers to the use of distillation in batches, meaning that a mixture is distilled to separate it into its component fractions before the distillation still is again charged with more mixture and the process is repeated. This is in contrast with continuous distillation where the feedstock is added and the distillate drawn off without interruption. Batch distillation has always been an important part of the production of seasonal or low capacity and high-purity chemicals. It is a very frequent separation process in the pharmaceutical industry and in wastewater treatment units. And continuous distillation is an ongoing separation in which a mixture is continuously (without interruption) fed into the process and separated fractions are removed continuously as output streams as time passes during the operation.The distillation process operated by manipulating the physical properties based on the volatility of the component in the mixture, the boiling point differences of the components in the mixture, using the boiling point is a way to separate the components from mixture is through heating process, by heating the mixture it will evaporate the components that have lower boiling point in comparison with the other components. This will leave behind the component that have higher boiling point that is still in liquid form. And to recover the evaporated components the condenser will be used condense the vapour back into liquid form. This is roughly the basic ideas behind distillation process. In much more complex system of distillation column the vapour liquid equilibrium principles were used as guidelines in the distillation process. In industrial level each of the binary or ternary mixture contains a set vapour liquid equilibrium data that helps engineer to perform separation process. Vapour Liquid Equilibrium data are the reason this study is conducted. The applications of distillations can be roughly divided in few groups, laboratory scale, and industrial distillation. The main difference between laboratory scale distillation and industrial is that laboratory scale is often performed batch-wise, whereas industrial distillation often occurs continuously. However azeotropic phenomena limit the separation achievable by ordinary distillation. Complete separation of azeotropic mixtures requires either the coupling the distillation columns with other separation methods such as adsorption, membranes, and extraction or the use of more complex distillation schemes based on a modification of the equilibrium to effect the complete separation. Although many new separation techniques are being developed, distillation will remain the method of choice for large-scale separation of non-ideal mixtures including azeotropic mixtures. Separation of such mixtures is achieved by use of one of the enhanced distillation methods. These include extractive distillation, salt distillation, pressure-swing distillation, reactive distillation, and azeotropic distillation. The latter method involves the use of entrainers to alter the relative volatility of the components and break the azeotrope. The choice of separation method depends on the specific system and economics (Silva, 2006).Related LiteratureBinary Mixture of MTBE and MethanolMTBE also known as methyl tertiary butyl ether and MTBE is a chemical compound with molecular formula (CH3)3CH3CO. MTBE is a volatile, flammable and colourless liquid that is immiscible with water. MTBE has a minty odour vaguely reminiscent of diethyl ether, leading to unpleasant taste and odour in water. MTBE is a gasoline additive, used as oxygenate and to rise the octane number, although its use has declined in the United States in response to environmental and health concerns. The production of MTBE is from the chemical reaction of Isobutylene and Methanol but in this reaction not all the reactants turn to MTBE, Methanol still exist in the final product of this reaction which the Methanol is the undesired product so it is important to separate the undesired and the desired product.Conventional production of MTBE Methyl tertiary butyl ether is a high octane fuel additive and non-toxic as well as none polluting in contrast to lead alkyl additives. The high number of process licensors and plant under operation underline the economical importance of MTBE. The demand is predicted to increase from 8 to 32 million tons in the year 2000 making it worthwhile to improve existing production facilities. (Hommerich, 1998)Figure 1 shows a schematic subdivision into three parts. In the reactor cascade, i-butene, which is available in C4 - Raffinate from a steam cracking or catalytic cracking processes. Therefore, the effluent from the cascade consists mainly of MTBE, linear butenes (n-butenes) and excess methanol. Particularly the azeotrope formation of methanol with both MTBE and C4 poses difficulties on the subsequent product purification. In column 1 operated at 6 bar, the reactor effluent is separated into and n-C4/methanol distillate with azeotropic composition and a bottom product containing approximation of 97 wt% MTBE and 3 wt% methanol. The distillate is fed to third process part where high selectivity of the etherification is used for producing pure n-C4 hydrocarbons. The MTBE /methanol stream of column 1 is fed to third process part where high selectivity of the etherification is used for producing pure n-C4 hydrocarbons. The MTBE/methanol stream of column 1 is fed to a second distillation at 12 bars in order to achieve the final product quality of over 99 wt% for MTBE. The MTBE/methanol azeotrope at the top of column 2 has to be recycled into the reaction zone, since an economical separation is not feasible because of the small amount (approx. 4% of the reactor effluent) (Hommerich, 1998).

MeOHMTBEColumn 2Column 1Figure 1. Schematic diagram of the production of MTBE (Hommerich, 1998)

Importance of Vapour-Liquid Equilibrium DiagramVLE is a set of data necessary especially for engineer in separation process. This data is importance in chemical industries. Most industries handle two type of distillation which is continuous and batch distillation, and VLE is at the heart of the process as it provides guidance at how to design of the distillation equipments itself.VLE is especially important to continuous distillation or fractional distillation. In distillation it is importance to have a boiling diagram of the binary mixture. The diagram provide the information of the mixture in terms of which components is more volatile (boiling point) and which is less volatile (higher boiling point).In the boiling point diagram it also show the fraction of the mixture at different temperature and pressure. This information is paramount to conduct any distillation process. Once the data acquired this will provide the engineer at what temperature and at what pressure should the distillation process be proceeds and provide how much distillate will be resulted from distillation and how much condensate will be obtained and this much more importance particularly for the continuous distillation process.Theory of Vapour-Liquid EquilibriumAs in gas-liquid systems the equilibrium in vapour liquid system is restricted by the phase rule. For two components system and two phases there are four variables which are temperature, pressure and compositions y of which is the fraction mixture in vapour condition and x which is in liquid conditions. In the mixture of two components let say MTBE and Methanol the mixture is in two phase, vapour and liquid. VLE is a set of data obtained experimentally to provide ways for engineer to separate the mixture effectively. VLE is a condition where a liquid and its vapour (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapour) equals the rate of condensation (vapour changing to liquid) on a molecular level such that there is no net (overall) vapour-liquid interconversion. Although in theory equilibrium takes forever to reach, such an equilibrium is practically reached in a relatively closed location if a liquid and its vapour are allowed to stand in contact with each other long enough with no interference or only gradual interference from the outside. There are many types of VLE. vapour and liquid. .VLE is a set of data obtained experimentally to provide ways for engineer to separate the mixture effectively. VLE is a condition where a liquid and its vapour (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapour) equals the rate of condensation (vapour changing to liquid) on a molecular level such that there is no net (overall) vapour-liquid interconversion. Although in theory equilibrium takes forever to reach, such an equilibrium is practically reached in a relatively closed location if a liquid and its vapour are allowed to stand in contact with each other long enough with no interference or only gradual interference from the outside. There are many types of VLE. VLE can be of one component and or more than one. VLE that comprise more than one component were called binary mixture (two components) of ternary for three components. It said that the more components we have in VLE the more complicated it will be (Geankoplis, 2003).

Figure 2. VLE Diagram of Binary MixtureFigure 2 the binary mixture of two components. Often the VLE relations for a binary mixture let say A(MTBE) and B(Methanol) are given as a boiling point diagram as shown above. The upper line is the saturated vapour line (or the dew point line) and the lower line is the saturated liquid line (the bubble point line).The region between those lines is the area which vapour and liquid are in mixture. In other word the mixture is between those line is a two phase region. The concentration of a vapour in contact with its liquid, especially at equilibrium, is often given in terms of vapour pressure, which could be a partial pressure (part of the total gas pressure) if any other gas are present with the vapour. The equilibrium vapour pressure of a liquid is usually very dependent on temperature. At vapour-liquid equilibrium, a liquid with individual components (compounds) in certain concentrations will have an equilibrium vapour in which the concentrations or partial pressures of the vapour components will have certain set values depending on all of the liquid component concentrations and the temperature. It also means that if a vapour with components at certain concentrations or partial pressures is in vapour-liquid equilibrium with its liquid, then the component concentrations in the liquid will be set dependent on the vapour concentrations, again also depending on the temperature.The equilibrium concentration of each component in the liquid phase is often different from its concentration (or vapour pressure) in the vapour phase, but there is a correlation. Such VLE concentration data is often known or can be determined experimentally for vapour-liquid mixtures with various components. In certain cases such VLE data can be determined or approximated with the help of certain theories such as Raoult's Law, Dalton's Law, and/or Henry's Law (Geankoplis, 2003).Raoults LawThe law was established by by Franois-Marie Raoult`s. Raoult's law which states that for binary mixture the total pressure of an non-ideal solution is dependent on the vapour pressure of each chemical component Pivap, the mole fraction of the component xi and yi present in the solution and its activity coefficient i which in mathematical is expressed as:

[1 &2]Equation 1 is also known as Vapour-Liquid Equilibrium equation which is only applicable for a system with low pressure. P is the total pressure vapour pressure of all the components exist in the mixture consequently, as the number of components in solution increases, the individual vapour pressures decrease, since the mole fraction of each component decreases with each additional component. The non-ideality in the equation is the introduction of the activity coefficient which is a factor used inthermodynamicsto account for deviations from ideal behaviour in amixtureofchemical substances. In anideal mixture, the interactions between each pair ofchemical speciesare the same (or more formally, theenthalpy change of solutionis zero) and, as a result, properties of the mixtures can be expressed directly in terms of simple concentrationsorpartial pressuresof the substances present e.g.Raoult's law for ideal solution. Deviations from ideality are accommodated by modifying the concentration by anactivity coefficient. Analogously, expressions involving gases can be adjusted for non-ideality by scalingpartial pressuresby afugacitycoefficient. So for the mixture to be ideal the activity coefficient must be equal to 1. Activity Coefficient Model UNIFAC equationThe UNIFAC model(UNIQUACFunctional-groupActivityCoefficients) was first published in 1975 by Fredenslund, Jones and Prausnitz, a group of chemical engineering researchers from the University of California. It is asemi-empiricalsystem for the prediction of non-electrolyteactivityin non-ideal mixtures. UNIFAC uses thefunctional groupspresent on the molecules that make up the liquid mixture to calculate activity coefficients.It attempts to break down the problem of predicting interactions between molecules by describing molecular interactions based upon the functional groups attached to the molecule. This is done in order to reduce the sheer number of binary interactions that would be needed to be measured to predict the state of the system. Equipped with the activity coefficients and a knowledge of the constituents and their relative amounts, phenomena such asphase separationandvapour-liquid equilibriacan be calculated. UNIFAC attempts to be a general model for the successful prediction of activity coefficients. It is mathematically expressed as for binary mixture: [3]

[4]

Where:

[5][12]

[6][13][7][14][8][15]

[9][16][10][17][11][18]The UNIFAC model splits up the activity coefficient for each species in the system into two components; a combinatorialand a residual component. For themolecule, the activity coefficients are broken down as per the following equation:

[19]For Equation 3 and 4, [20]

[21]

In the UNIFAC model, there are three main parameters required to determine the activity for each molecule in the system. Firstly there are the group surface areaand volume contributionsobtained from theVan der Waalssurface area and volumes. These parameters depend purely upon the individual functional groups on the host molecules. Finally there is the binary interaction parameter, which is related to the interaction energyof molecular pairs (equation in "residual" section). These parameters must be obtained either through experiments, via data fitting or molecular simulation.Wagner Vapor Pressure EquationThe Wagner vapor pressure equation is the best equation for correlation. It is expressed as:

[22]Where [22][23]

The A, B, C and D are characteristics constants for the fluid under study, and Pvap is the vapour (saturation) pressure. If parameters A, B, C, and D are available for a pure hydrocarbon, the equation predicts vapour pressures within the acceptable accuracy down to a reduced temperature of 0.5 which is more accurate than other vapour pressure estimation equation (DDBSP, 2009).AzeotropeDepartures of the Raoult`s Law frequently manifest themselves in the formation of azeotropes particularly mixtures of close boiling species of different chemical types whose liquid solutions are non ideal. azeotropes are formed by liquid mixtures exhibiting maximum and minimum boiling point. These represent, respectively negative or positive deviations from Raoult`s Law. Vapour and liquid compositions are identical at the azeotropic compositions thus all the K values are 1 and no separation can take place. There are types of azeotropes that are commonly encountered with the binary mixture. The most common type by far is the minimum boiling homogenous azeotrope. Heterogeneous azeotrope is always minimum boiling point mixture because activity coefficient must be significantly greater than 1 to cause the splitting into two liquid phases. This is true for the MTBE Methanol mixture which showed minimum azeotrope position. azeotropes limit the separation achievable by ordinary distillation. It is possible to shift the equilibrium by changing the pressure sufficiently to break azeotrope or move it away from the region where required separation must take place (Seaders, 1998)

THE PROBLEM

Statement of the ProblemBinary mixture of MTBE-Methanol have been subject of numerous investigations in recent years because of their anti knock properties. However azeotropic phenomena limit the separation of this mixture achievable by ordinary distillation. Complete separation of azeotropic mixtures requires either the coupling the distillation columns with other separation methods such as adsorption, membranes, and extraction or the use of more complex distillation schemes based on a modification of the equilibrium to effect the complete separation. Although many new separation techniques are being developed, distillation will remain the method of choice for large-scale separation of non-ideal mixtures including azeotropic mixtures. Separation of such mixtures is achieved by use of one of the enhanced distillation methods. These include extractive distillation, salt distillation, pressure-swing distillation, reactive distillation, and azeotropic distillation. The latter method involves the use of entrainers to alter the relative volatility of the components and break the azeotrope. The choice of separation method depends on the specific system and economics (Silva, 2006).The final steps in the synthesis process of MTBE are the separations of the compound from the methanol via azeotropic distillations. The study of Vapour Liquid of the mixture is of great interest to supplement the design of the distillation processes, because the mixture showed deviations from Raoult`s Law that is positive azeotropic, positive or negative azeotrope will influence separations in terms of its efficiencies. Initial step in studying azeotropes is study on Vapour Liquid Equilibrium Diagram.ObjectiveThe objective of the project is to obtain a Vapour-Liquid diagram for MTBE- Methanol Binary mixture as a function of pressure, temperature and composition.Scope of ProjectI. To construct x-y, P-xy, and T-xy diagram for MTBE-Methanol mixture.II. Determine azeotropic point of MTBE-Methanol mixture. Significance of the ProjectAzeotrope has limits the separation achievable by ordinary distillation. It is possible to shift or break the azeotropic point by applying entrainer in separation process. To research on what type of entrainer that would work in enhancing separation process, the research on the Vapour Liquid Equilibrium of the mixture must be completed first. The significant of study into the Vapour Liquid Equilibrium is that it can provide data such as temperature, pressure and vapour/liquid fraction compositions that can be simplified in a diagram that could help the study of finding the entrainer.

METHODOLOGY

Tools used: 1. Microsoft Excel 20072. Modified UNIFAC Program from SandlerProcedure:Determining activity coefficients of MTBE and MethanolModified UNIFAC program developed by Sandler was used in determining activity coefficients of MTBE and Methanol. This was done by supplying first the number of components (2), name of the components (MTBE and Methanol), and the number of groups in each molecule from the menu of UNIFAC groups. MTBE has 3 groups which are CH3, C, and CH3O and on the other hand, Methanol has only 1 group which is CH3OH. A temperature was also supplied in the program which is 40C or 313.15K. From this temperature, vapour pressure was then calculated and used by the program to determined the activity coefficients and the equation model used in determining the vapour pressure is the Wagner 3,6 model. Gex-xy diagram was chosen and activity coefficients at varying compositions from 0-1 with an increment of 0.025 was displayed in the display area in the program (located lower left).Constructing x-y and P-xy diagramActivity coefficients with its accompanying liquid MTBE composition obtained from the Modified UNIFAC program was tabulated in the Excel Spreadsheet also with activity coefficients of MTBE and Methanol. Equation 1 and 2 was used in determining P and y, respectively, at varying composition of liquid MTBE and at constant temperature of 313.15 where Equation 22 was used in determining the vapour pressure of MTBE and Methanol at the same temperature. This was tabulated in the Excel Spreadsheet. An x-y diagram was constructed using the data in the spreadsheet. This was done by plotting the column containing x1 vs columns containing y1 then columns containing x1 vs with the same column that contains x1 in one Scatter graph with smooth lines. Also, P-xy diagram was constructed using the same data in the spreadsheet. This was done by plotting the column that contains P vs column containing x1 and vs column containing y1 in one Scatter graph with smooth lines.Constructing T-xy diagramThis required iterative method in determining T at varying composition of liquid MTBE and constant pressure which chosen to be close to azeotrope located in the P-xy and x-y diagram. 10 columns was created which are named alphabetically from A-J. Column A contains x1, column B and C contains 1 and 2, column D contains chosen temperature which are all 300K, column E and F contains t1 and t2, column G and H contains vapour pressure of MTBE and Methanol, column I contains total pressure P, and column J containing y1. Equation 1, 2, 22, and 23 were used in column I, J, G and H, and E and F, respectively. Solver add-ins was used for iteration in which the set target cells are column I that must be equal to chosen constant pressure and the changing column is column D. A T-xy diagram was constructed using the resulting data in the spreadsheet. This was done by plotting column D vs column A and vs column J.RESULTS AND ANALYSIS

Figure 3. The x-y diagram for the MTBE-Methanol system at a fixed temperature of 313.15K

Figure 4. The x-y diagram for MTBE-Methanol system at a fixed pressure of 0.6677 bar.

Figure 5. The Pressure-composition diagram for the MTBE-Methanol system at fixed temperature of 313.15K

Figure 6. The Temperature-composition diagram for the MTBE-Methanol system at fixed pressure of 0.6677 bar.

It can be be verified in figure 3 6 in which it shows nonlinear function of mole fraction that non-ideal solutions such as MTBE-Methanol exhibits deviation from Raoults law.Also From Figure 3-6 it showed that MTBE-Methanol mixture formed azeotropic point at 313.15K in figure 6 and at 0.6677 bar in figure 3-5 which are all at composition approximately 0.7175. At this point the Azeotropic formed the minimum boiling point or positive azeotrope highlighting that this is the positive deviation of Raoult`s Law. This is also because that the activity coefficient of at least one of the species Methanol or MTBE in the mixture is greater than unity which is > 0.As presented Figure 3 and 4, below the azeotropic point it has a greater difference between the x-y curve (blue curve) of the mixture and the x = y line (red line). This tells us that there is larger difference in composition between the liquid and the vapour phase and thus it is easier to separate the MTBE and Methanol by distillation (Sandler, 1999). In figure 6, it was assumed that the small variations of temperature do not greatly affect the activity coefficients because the temperature dependence of activity coefficient is small compared to the variation of the vapour pressure (Sandler, 1999).Conclusion: Vapour-Liquid Equilibrium diagram of MTBE-Methanol binary mixture were obtained by constructing its x-y and P-xy at constant temperature of 313.15K and T-xy diagram at constant pressure of 0.6677 bars in which exhibits deviation from Raoults law. Azeotropic point was determined at composition approximately 0.7175 and a pressure of 0.6677 bar for P-xy diagram and a temperature of 313.15K for T-xy diagram.

References:DDBPS. (2009). Pure components Equations. OldenBurgGeankopolis, G.J. (2003). Principles of Transport Processes and Separation Processes. New Jersey. Pearson Education, Inc.Hommerich U., Rauterbach R.D. (1998) Design and Optimization of Combined Pervaporation/Distillation process for the production of MTBE. Journal of Membrane Science.Ishak, M.A. (2010). Effects of Temperature on Vapour-Liquid Equilibrium of MTBE-Methanol Mixtures. Malaysia. University of Malaysia Pahang.Sandler, S.I. (1999). Chemical and Engineering Thermodynamics. 3rd edition. New York. John Wiley and Sons and Technology.Seaders, J.D. (1998). Separation process principles. John Wiley and Sons Publishing Inc.Silva, E.A.B., Rodrigues, A.E. (2008) Design Methodology and Performance Analysis of a Pseudo-Simulated Moving Bed for Ternary Separation. Separation Science and Technology.

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APPENDIXAppendix A. UNIFAC model constants and parameters for MTBE-Methanol binary mixtureTable 1. UNIFAC definition of components MTBE and EtOH

componentsSubgroupno.riqili vk

MTBE (1)CH334.37574.032-1.65724

C1

CH3O1

MeOH (2)CH3OH11.43111.432-0.43563

Table 2. UNIFAC Rk and Qk values for each subgroup

SubgroupRQ

C0.21950.0000

CH30.90110.8480

CH3O1.14501.0880

CH3OH1.43111.4320

Table 3. UNIFAC Main group interaction parameters, amn in Kelvin

main groupCH2CH3OCH3OH

CH20251.5697.2

CH3O83.360238.4

CH3OH16.51-128.60

Appendix B. Data for constructing x-y, P-xy and T-xy diagram for MTBE-Methanol binary mixture systemTable 4. Activity Coefficients at varying composition of liquid MTBE, x1 at constant temperature of 313.15K determined using Modified UNIFAC model

x112x112x112x112

0.00003.76511.00000.27501.86741.10120.52501.34701.36970.77501.08542.0640

0.02503.38631.00130.30001.79571.11880.55001.31221.41210.80001.06872.1859

0.05003.09221.00480.32501.72981.13790.57501.27951.45870.82501.05372.3241

0.07502.85651.01010.35001.66911.15890.60001.24891.50990.85001.04042.4820

0.10002.66231.01700.37501.61281.18170.62501.22021.56630.87501.02872.6635

0.12502.49881.02520.40001.56051.20660.65001.19341.62870.90001.01892.8734

0.15002.35861.03460.42501.51191.23370.67501.16841.69780.92501.01103.1181

0.17502.23651.04540.45001.46641.26330.70001.14521.77460.95001.00503.4060

0.20002.12871.05730.47501.42401.29570.72501.12361.86030.97501.00133.7480

0.22502.03261.07060.50001.38421.33100.75001.10371.95621.00001.00004.1585

0.25001.94601.0852

Table 5. P and y1 data at constant temperature of 313.15K

x1y1P[bar]x1y1P[bar]x1y1P[bar]x1y1P[bar]

0.00000.00000.35480.27500.51980.58990.52500.64650.65310.77500.75300.6670

0.02500.12740.39690.30000.53650.59950.55000.65650.65640.80000.76700.6656

0.05000.21420.43100.32500.55190.60820.57500.66640.65930.82500.78250.6634

0.07500.27840.45940.35000.56620.61610.60000.67620.66170.85000.79990.6601

0.10000.32860.48370.37500.57950.62320.62500.68600.66380.87500.81980.6556

0.12500.36950.50480.40000.59200.62960.65000.69610.66540.90000.84300.6495

0.15000.40370.52330.42500.60390.63540.67500.70630.66670.92500.87060.6414

0.17500.43300.53970.45000.61510.64050.70000.71700.66750.95000.90420.6305

0.20000.45860.55430.47500.62590.64520.72500.72820.66790.97500.94600.6162

0.22500.48120.56750.50000.63640.64940.75000.74020.66781.00001.00000.5971

0.25000.50150.5793

Table 6. T and y1 data at constant pressure of 0.6677 bar

x1y1T [K]t1t2P1vapP2vapP

0.00000.0000327.41390.34040.36130.98230.66770.6677

0.02500.1153325.09820.34510.36580.90920.60510.6677

0.05000.1983323.33430.34860.36920.85640.56080.6677

0.07500.2619321.93050.35150.37200.81610.52750.6677

0.10000.3127320.77700.35380.37420.78420.50140.6677

0.12500.3546319.80890.35570.37610.75810.48040.6677

0.15000.3902318.98270.35740.37770.73640.46300.6677

0.17500.4209318.26550.35890.37910.71800.44830.6677

0.20000.4478317.64090.36010.38030.70230.43590.6677

0.22500.4717317.08920.36120.38140.68860.42520.6677

0.25000.4931316.60180.36220.38240.67670.41590.6677

0.27500.5125316.16890.36310.38320.66630.40770.6677

0.30000.5301315.78130.36390.38400.65710.40060.6677

0.32500.5464315.43650.36460.38460.64890.39430.6677

0.35000.5614315.12580.36520.38520.64170.38870.6677

0.37500.5754314.84900.36570.38580.63530.38380.6677

0.40000.5886314.60070.36620.38630.62960.37950.6677

0.42500.6010314.37770.36670.38670.62450.37560.6677

0.45000.6127314.17930.36710.38710.62000.37210.6677

0.47500.6240314.00030.36740.38740.61600.36910.6677

0.50000.6348313.84280.36780.38770.61240.36640.6677

0.52500.6453313.70200.36800.38800.60930.36400.6677

0.55000.6556313.57730.36830.38830.60650.36190.6677

0.57500.6657313.46930.36850.38850.60410.36010.6677

0.60000.6757313.37650.36870.38870.60210.35850.6677

0.62500.6857313.29950.36890.38880.60040.35730.6677

0.65000.6959313.23660.36900.38890.59900.35620.6677

0.67500.7063313.18900.36910.38900.59790.35540.6677

0.70000.7170313.15650.36910.38910.59720.35490.6677

0.72500.7283313.14270.36920.38910.59690.35470.6677

0.75000.7402313.14770.36920.38910.59700.35480.6677

0.77500.7529313.17600.36910.38900.59770.35520.6677

0.80000.7668313.23120.36900.38890.59890.35610.6677

0.82500.7822313.31850.36880.38880.60080.35760.6677

0.85000.7994313.44560.36860.38850.60360.35970.6677

0.87500.8191313.62710.36820.38820.60760.36270.6677

0.90000.8421313.87480.36770.38770.61310.36690.6677

0.92500.8695314.21350.36700.38700.62080.37270.6677

0.95000.9029314.68050.36610.38610.63140.38090.6677

0.97500.9450315.32280.36480.38490.64630.39230.6677

1.00001.0000316.22740.36300.38310.66770.40880.6677

Appendix C. Data for determination of Vapour Pressure as a function of temperatureTable 7. Wagner 3,6 parameters, Tc and Pc data

Pvap constantscomponent

12

A-7.8252-8.5480

B2.95490.7698

C-6.9408-3.1085

D12.17421.5448

Tc496.4000512.6000

Pc33.700080.9000