Department of Chemical EngineeringUniversity of San Carlos – Technological Center

Nasipit, Talamban, Cebu City

ChE 512LChemical Engineering Laboratory 2

Reaction Rate Kinetics, Temperature Effects, and Performance of a Plug Flow Reactor( Tubular Flow Reactor )

An Initial Laboratory Report Submitted ToEngr. May V. TampusInstructor, ChE 512L

ByGroup 4

Aaron, James Glerry J.Chia, Bernadette A.

Saladaga, Jesha Helery R.

July 30, 2014

2. Objectives

2.1 Determine the reaction order and the rate constant for the ethyl actetate-NaOH reaction

system using plug flow reactor data.

2.2 Determine the variation of conversion with respect to the residence time.

2.3 Verify the temperature dependence of the reaction rate constant.

4. Results and Discussion

4.1 Determination of Reaction Order and the Rate Constant

0.501.001.502.002.503.003.504.000.00

0.01

0.02

0.03

0.04

f(x) = − 0.0030368461538 x + 0.0329705128205R² = 0.977539759818241

τ, min

CNaO

H,f

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

-4.0000

-3.9000

-3.8000

-3.7000

-3.6000

-3.5000

-3.4000

-3.3000

f(x) = − 0.122412116451238 x − 3.38258196162775R² = 0.979038936165714

τ, min

ln C

NaO

H,f

(a)………………… ………………………………(b)

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.500.0000

10.0000

20.0000

30.0000

40.0000

50.0000

60.0000

f(x) = 4.98771688359217 x + 28.1150188280933R² = 0.980020508182786

averageLinear (average)

τ, min

1/ C

NaO

H,f

(L/

mol

)

(c)

Figures 4.1.1 Plots of the average of the two trials in (a) zero order, (b) first order, and (c) second order reaction kinetics.

Table 4.1.1. Summary of Reaction Order and Rate Constant Determination

Reaction Order,

n

Rate

KineticsPlot R2

Rate Constant, k Unit

0 -rA=k CA vs τ 0.9775 333.7041 mol/L.min

1 -rA=kCA ln(CA) vs τ 0.9790 8.1728 1/min

2 -rA=kCA2 1/CA vs τ 0.9800 0.2005 L/mol.min

The integral method was used to determine the order and rate constant of the ethyl acetate-NaOH reaction. Figure 4.1.1 shows the best fit lines for every plot of an order. It can be seen that the best fit line with the highest regression coefficient, R2, is the n=2. This means that the reaction between ethyl acetate and NaOH is second order. This is in accordance with the hypothesis that the reaction is second order based on its stoichiometry. The reaction depends on both the concentration of ethyl acetate and NaOH, and may possibly follow an elementary rection.

4.2 Conversion as a Function of Residence Time

0.0000 0.5000 1.0000 1.5000 2.0000 2.5000 3.0000 3.5000 4.0000 4.50000.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Residence time, min

xNaO

H

Figure 4.2 Variation of conversion with residence time. Data plotted are the average of the two trials.

Figure 4.2 shows that for a certain residence time (τ = 0 to τ = 1 min), the conversion of NaOH increases. But after τ = 1 min, the slope of the curve changes. The conversion of NaOH still increases with the residence time, but in a lesser rise as compared to the first part. This is because at the beginning of the reaction, there are still higher concentrations of the reactants giving way to more reaction. However, as time increases, there is a decrease in the reactant

concentrations and little conversion is going on. As time increases, more products are formed, more reactants are consumed, and conversion increases.

4.3 Determination of Temperature Dependence of Reaction Rate

3.05E-03 3.10E-03 3.15E-03 3.20E-03 3.25E-03 3.30E-030.0000

0.5000

1.0000

1.5000

2.0000

2.5000

3.0000

3.5000

4.0000

f(x) = − 3917.01232361525 x + 15.8255217845551R² = 0.993258231371198

1/Tave ,K-1

ln k

ave

Figure 4.3 Variation of Rate Constant with Temperature Based on Average Values

Figure 4.3 shows the Arrhenius’ plot of the reaction between ethyl acetate and NaOH; table 4.3 shows the calculated frequency factor (k0) and activation energy (E) from the experiment. Because the plot (figure 4.3) gives off an R2 = 0.9933, the reaction follows Arrhenius law which states that the energy activation energy is constant for a reaction at the same concentration but different temperatures. The temperature dependency of a reaction is found in the rate constant which is affected by the activation energy and the temperature of the system. The higher the temperature, the higher the rate constant is because high temperatures signify higher kinetic energy of the molecules. This will lead to more collisions between the reactants and the reaction occurring between them.

The average activation energy calculated is 131777.4 J/mol and the k0 is 7466971. The high value of the activation energy means that the ethyl acetate-NaOH reaction is greatly affected by the temperature, or that it is a temperature-sensitive reaction.

Table 4.3 Temperature Dependence of Trials 1 and 2, and Average

ko E (J/mol)

Average 7.47E+06 131577.4Trial 1 1.31E+06 28653.37Trial 2 4.22E+07 36478.51

References:

Geankoplis, C. J. (2003). Transport Processes and Unit Operations / C.J. Geankoplis.

Englewood Cliffs, EUA : Prentice-Hall.

Levenspiel, O. (1967). Chemical reaction engineering. New York: Wiley.

7. Appendices

Table 7.1. Determination of Initial Concentration of NaOH Solution

Volume of

NaOH (mL)

Initial Buret

Reading (mL)

Final Buret

Reading (mL)

Volume of 0.1N

HCl used in

titration (mL)

CNaOH

(mol/L)

Trial 1 10.00 0.00 9.50 9.50 0.095

Trial 2 10.00 9.50 19.60 10.10 0.101

Average CNaOH

(mol/L)0.098

Table 7.2. Determination of initial concentration of EtOAc solution

Volume

of EtOAc

(mL)

Volume of

0.1N NaOH

added (mL)

Volume of

0.1 N HCl

added (mL)

Initial

Buret

Reading

(mL)

Final

Buret

Reading

(mL)

Volume of

NaOH used

in titration

(mL)

CEtOAc

(mol/L)

Trial 1 5.00 10.00 10.00 20.00 25.20 5.20 0.098

Trial 2 5.00 10.00 10.00 33.00 38.10 5.10 0.096

Average

EtOAc

(mol/L)

0.097

Table 7.3. Relevant Parameters

Reactor Volume (L)

0.4 CHCl used (N) 0.1

CNaOH in feed vessel (mol/L)

0.098CNaOH used in titration (N)

0.097

Table 7.4. Data for Constructing n=0, n=1, n=2 Graphs

T (0C) FNaOH

(cm3/mi

n)

FEtOAc

(cm3/mi

n)

v0

(cm3/mi

n)

Ƭ(min)

TITRANT (0.097 N NaOH) CNaOH, effluent

(mol/L)xNaOH

Initial Reading (mL)

Final Reading (mL)

VNaOH (mL)

Initial Final 1 2 1 2 1 2 1 2 1 2 Ave.

31.5 31.2 50 50 100 4.00 0.00 8.15 8.15 16.35 8.15 8.20 0.0209 0.0205 0.7863 0.7912 0.7888

31.0 31.0 100 100 200 2.00 16.35 23.50 23.50 31.40 7.15 7.90 0.0306 0.0234 0.6873 0.7615 0.7244

31.0 31.0 150 150 300 1.33 30.60 37.90 37.90 45.10 7.30 7.20 0.0292 0.0302 0.7021 0.6922 0.6972

31.0 31.0 200 200 400 1.00 0.00 7.20 7.20 14.60 7.20 7.40 0.0302 0.0282 0.6922 0.7120 0.7021

40.0 41.0 100 100 200 2.00 0.00 7.80 7.80 15.80 7.80 8.00 0.0243 0.0224 0.7516 0.7714 0.7615

51.5 50.8 100 100 200 2.00 17.80 26.50 26.50 34.80 8.70 8.30 0.0156 0.0195 0.8407 0.8011 0.8209

Table 7.4. Data for Constructing n=0, n=1, n=2 Graphs (Continued)

τ, minCNaOH,f

Ave.ln CNaOH,f Averag

eCNaOH,f (mol/L) Averag

eTrial 1 Trial 2 Trial 1 Trial 2 Trial 1 Trial 2 Trial 1 Trial 2

4 0.0209 0.0205 47.7441 48.8759 -0.0428 -3.8659 -3.8893 -3.8776 0.0209 0.0205 0.0207

2 0.0306 0.0234 32.6318 42.7899 -0.0307 -3.4853 -3.7563 -3.6208 0.0306 0.0234 0.027

1.3333 0.0292 0.0302 34.2583 33.1565 -0.0262 -3.5339 -3.5012 -3.5176 0.0292 0.0302 0.0297

1 0.0302 0.0282 33.1565 35.4359 -0.0268 -3.5012 -3.5677 -3.5345 0.0302 0.0282 0.0292

Table 7.5. Conversions with Respect to Residence Times

Residence time, Ƭ(min)

Average Trial 1 Trial 2

4.0000 0.7888 0.7863 0.79122.0000 0.7244 0.6873 0.76151.3333 0.6972 0.7021 0.69221.0000 0.7021 0.6922 0.71200.0000 0.0000 0.0000 0.0000

1CNaOH ,f

0.501.001.502.002.503.003.504.004.500.0000

10.0000

20.0000

30.0000

40.0000

50.0000

60.0000

f(x) = 5.01727855647107 x + 26.4949985095411R² = 0.869630692952673

τ, min

1/ C

NaO

H,f

(L/m

ol)

0.501.00

1.502.00

2.503.00

3.504.00

4.50-3.9000-3.8000-3.7000-3.6000-3.5000-3.4000-3.3000-3.2000

f(x) = − 0.124737250621105 x − 3.33670795701921R² = 0.860784202051625

τ, min

ln C

NaO

H,f

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.500.0000

0.0050

0.0100

0.0150

0.0200

0.0250

0.0300

0.0350

f(x) = − 0.00313384615384615 x + 0.0342638461538461R² = 0.850202429149797

CNaO

H,f

(a) (b) (c)

0.00 1.00 2.00 3.00 4.00 5.000.0000

10.0000

20.0000

30.0000

40.0000

50.0000

60.0000

f(x) = 4.95815521071331 x + 29.7350391466454R² = 0.863480534763729

τ, min

1/ C

NaO

H,f

(L/m

ol)

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50-4.0000-3.9000-3.8000-3.7000-3.6000-3.5000-3.4000-3.3000

f(x) = − 0.120086982281373 x − 3.42845596623628R² = 0.829441218955464

τ, min

ln C

NaO

H,f

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.500.00000.00500.01000.01500.02000.02500.03000.0350

f(x) = − 0.00293984615384615 x + 0.0316771794871795R² = 0.792910409643478

τ, min

CNaO

H,f

(d) (e) (f)

Figures 7.1 Plots of the trials 1 (a to c) and 2 (d to f) in second order, first order, and zero order reaction kinetics respectively.

0 1 2 3 40.000.100.200.300.400.500.600.700.800.90

Residence time, min

xNaO

H

0 1 2 3 40.000.100.200.300.400.500.600.700.800.90

Residence time, min

xNaO

H

Figures 7.2 Plots of Conversions versus Residence Time of Trials 1 and 2 respectively.

Table 7.6. Data for Determining Temperature Effects

Average Temperature, Tave (1/Tave)

Initial CNaOH

(mol/L)

Final cNaOH

(mol/L)xNaOH Ƭ

(min)(oC) (K) Trial 1 Trial 2 Trial 1 Trial 2

31 304.15 0.003288 0.098 0.0306 0.0234 0.6873 0.7615 2.00

40 313 0.003195 0.098 0.0243 0.0127 0.7516 0.8704 2.00

50.5 323.5 0.003091 0.098 0.0156 0.0098 0.8407 0.9001 2.00

Table 7.6. Data for Determining Temperature Effects (Continued)

k=1 /(τ*Ca) ln k

Trial 1 Trial 2 Average Trial 1 Trial 2 Average

16.31588 21.39495 18.8554 2.792139 3.063155 2.9276

20.54232 39.37008 29.9562 3.022487 3.673006 3.3477

32.03075 51.07252 41.5516 3.466696 3.933247 3.7000

3.0E-03 3.2E-03 3.4E-030

0.51

1.52

2.53

3.5

f(x) = − 4472.01524075961 x + 17.0873600222512R² = 0.984937618299799

1/Tave ,K-1

ln k

3.0E-03 3.2E-03 3.4E-030.000.501.001.502.002.503.003.504.004.50

f(x) = − 5227.59779238796 x + 20.0671987538359R² = 0.925334910622164

1/Tave ,K-1

ln k

Figures 7.1 Plots of Temperature Dependence of Trials 1 and 2, respectively

SAMPLE CALCULATIONS