Abstract

Introduction

To separate miscible and immiscible mixture, thermodynamic parameters play a very important

role. For a given system, vapor-liquid equilibrium data has to be obtained to know the

components behavior in the system. To separate and purify the components, interaction

parameters have to be calculated with respect to all the components present in the system. For

obtaining the data, experiments were performed but these were limited to simple systems and

were not helpful in industrial applications. As the components increase, it becomes difficult to

obtain the accurate interaction parameters and vapor-liquid phase equilibrium data. Hence

thermodynamic models were developed on tools such as NRTL, UNIFAC, etc. to verify the

experimental data for a given system. This resulted in understanding the system, getting more

knowledge for boiling point, azeotropic mixtures, etc. and also comparing the experimental data

with the model equations.

In this study, we have worked upon the separation of Methyl Acrylate (MA) which is one of the

important components for industrial purpose. We have validated the interaction parameter results

for multiphase behavior of a system consisting of methyl acrylate (MA), Methanol (Me), Methyl

Acetate (MeOAc) and water (H2O) by using thermodynamic models of NRTL and UNIFAC.

Interaction parameters for binary system such as H2O-MA, H2O-Me, H2O-MeOAc, MeOAc-

Me, MeOAc-MA, Me-MA haven been studied by many researchers in the previous years.

Experiments were also done on ternary and quaternary systems but the data obtained couldn’t be

extrapolated to complicated systems. So to fulfill these insufficient results thermodynamic tools

of Aspen is very helpful.

Modeling Approach

Thermodynamic equilibrium data of all three systems H2O-Me-MA, H2O-Me-MeOAc, H2O-

MA-MeOAc were obtained by simulating the ternary system using Aspen Plus V8.4. Using the

NIST database of Aspen, the system was regressed with those available data and binary

interaction parameters were obtained using NRTL (Non Random Two Liquid) model for the

components. Using these parameters, bubble point and dew point temperature was calculated and

plotted to obtain the binary VLE and LLE phase diagrams. Mole fraction and mass fraction was

also calculated and ternary VLE and LLE phase diagrams were obtained. All these data and plots

available were compared to the previous literature data available which validates it perfectly.

NRTL model:

The Non Random Two Liquid model (NRTL) is an activity coefficient model that correlates .the

activity coefficients of a compound with its mole fractions in the concerned liquid phase. The

model provides precise representation of highly non-ideal VLE and LLE systems. The NRTL

activity coefficient expression for multi-component system is given as:

Where

Gij is the energy interaction parameter for components and τij is the temperature dependent

parameter between i and j.

Results & Discussion

The three ternary system were simulated in Aspen and results were obtained.

The following interaction parameters were obtained after regression of the thermodynamic

equilibrium data in Aspen Plus NRTL model:

i-j αij aij aij bij bij

1-2 0.3 -1.69451844 2.62864832 1245.39328 -102.324971

1-3 0.3 5.29100053 -2.42119461 -854.561638 1071.28247

1-4 0.3 4.84170631 -2.52084741 -1232.26827 743.029065

2-3 0.3 -0.08768 -0.818468524 -20.78 329.4381

2-4 0.3 -1.64458815 0.879381222 670.46144 2

3-4 0.3 -1.18988098 0.186680235 618.996818 56.0419807

Table : Binary Intraction Parameters of the NRTL model for H2O (1), MA (2), MeOAc (3) and

Me(4)

Form the above interaction parameters we

System 1: Vapor-Liquid-Liquid Equilibrium of Water-Methyl Acrylate-Methanol (H2O-MA-Me)

water-methanol-methyl acrylate

For the binary system of H2O-Me, fig shows the VLE of two different liquid and vapor phase

which is similar to the data that has been obtained earlier. There is no azoetrope formation in this

system.

Fig : VLE phase diagram for Water-Methyl Acetate using NRTL model

Fig : VLE phase diagram for Methyl Acrylate-Methyl Acetate using NRTL model

In

Fig : Binary VLLE phase diagram for Water-Methyl Acrylate using NRTL model

In the binary system of MA-H2O, the VLLE data was calculated and plotted using the NRTL

model. From the VLLE graph in Fig we can conclude that MA forms a minimum boiling

azeotrope with H2O at temperature=344.2K, mole fraction of MA as 0.728 which verifies the

data given in the literature.

Fig : Ternary LLE phase diagram for Water-Methyl Acrylate using NRTL model

System 2:

water-methanol-methyl acetate

System 3:

water-methyl acrylate-methyl acetate

Conclusions

Acknowledgment

References