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Challenging problem: acetone chloroform€¦ · César Eduardo Flores Ríos A01168336 ... b. The...

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Members: 2 Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336 Date: November 24 th Group: 1 Challenging problem: acetone chloroform a. Graph representation Figure 1. Ideal T-xy graph of a mixture of acetone with chloroform. In this graph we observed that the behavior of the mixture is ideal because this form does not contemplate the molecular interactions and does not have an azeotrope. Figure 2. Wilson T-xy graph of a mixture of acetone with chloroform.
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Members: 2 Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

Date: November 24th Group: 1

Challenging problem: acetone – chloroform

a. Graph representation

Figure 1. Ideal T-xy graph of a mixture of acetone with chloroform.

In this graph we observed that the behavior of the mixture is ideal because this form

does not contemplate the molecular interactions and does not have an azeotrope.

Figure 2. Wilson T-xy graph of a mixture of acetone with chloroform.

Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

Figure 3. Comparison between Wilson and Ideal T-xy graph of a mixture of acetone with

chloroform.

The Wilson model contemplates the excess calculations with the Gibbs free energy molar excess of the mixture and that is why the behavior of the graph goes to another direction. The graph contains an azeotrope.

Figure 4. NRTL T-xy graph of a mixture of acetone with chloroform.

Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

Figure 5. Comparison between NRTL and Ideal T-xy graph of a mixture of acetone with

chloroform.

The behavior of this model is determinate by another kind of parameter different than

ideal model parameter is related to the non-randomness of the mixture, or is that the

components of the mixture are not randomly distributed, but follow a pattern defined by

the local composition. The graph contains an azeotrope.

Figure 6. UNIQUAC T-xy graph of a mixture of acetone with chloroform.

Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

Figure 7. Comparison between UNIQUAC and Ideal T-xy graph of a mixture of acetone with

chloroform.

Was necessary to developed a new equation that determinate the data in a reliable way

and then was developed the UNIQUAC and we notice in the graph behavior that in this

case the randomness in the molecules was contemplated and the different sizes of the

molecules. The graph contains an azeotrope.

The azeotropes are mixtures of two or more components that the proportions are such

that the vapor produced by partial evaporation has the same composition as the liquid.

Exist many forms to avoid the azeotrope, for example add another compound to the

mixture but the disadvantage is that later we are going to need another separation.

Another form is to change the pressure, it will be able to move the azeotrope with the

objective to obtain a more pure separation. Another form is to find the way of not pass

through the azeotrope.

b. The maximum x achievable

For the calculation of the theoretical plates we used UNIQUAC model because is the

more reliable of the three models because contemplate more variables.

According to Aspen Plus Software with the initial concentrations are 0.05 for acetone

and 0.95 in the case of chloroform and a temperature of 25°C and pressure of 1 atm the

maximum x achievable is: 0. 3435.

To obtain a better result was used the other two models, Wilson and NRTL to get the

maximum x achievable and the result was the same of the data in UNIQUAC.

Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

Figure 8. Results of the azeotrope obtained on Aspen plus software of a mixture of acetone with

chloroform using xi= 0.05 of the volatile compound.

c. Theoretical plates

The selected method is UNIQUAC, then the theoretical plates was calculated using the

T-xy graph of this method.

The result is approximately 7 theoretical plates.

The graphical representation of theoretical plates of UNIQUAC graphic representation:

Figure 9. Graphical representation of theoretical plates of UNIQUAC of a mixture of acetone

with chloroform.

Paola Chanel Villegas Tapia A01373219 César Eduardo Flores Ríos A01168336

d. Related component structure - Intermolecular forces and discuss

In the case of a mixture acetone – chloroform are negative deviations from Raoult’s law

because the molecules have polar groups. There are strong unlike interactions, specific

between the carbonyl oxygen and the hydrogen on chloroform; this interactions produce

a negative excess Gibbs energy; in other words there are strong hydrogen bonding

interactions too.

Those interactions may cause the formation of specific inseparable compositions where

the vapor and liquid compositions are in equilibrium (azeotrope); we use the UNIQUAC

model to check that affirmation and the conclusion is that the maximum x is located in

the azeotrope, in this case the x= 0.3435.

References

Apuntes científicos (s.f.). Desviaciones de la ley de Raoult. Retrieved from http://apuntescientificos.org/azeotropos-ibq2.html.

IRA A. Fulton College. (s.f.). Vapor-liquid equilibria (VLE). Retrieved from http://www.et.byu.edu/~rowley/VLEfinal/background4.htm

UVIGO (2004). Modelos termodinámicos para el equilibrio fase liquido-vapor. Retrieved from http://eueti.uvigo.es/files/material_docente/1621/modelostermodinamicos.pdf


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