Exp. G notes Fractional Distillation, 30Aug2004 page 1

Prelab: provide only for 1-propanol, 1-butanol, and methanol

Properties

M.W. M.P. B.P. Den. Sol. (> 10%) Hazard1-propanol 60.10 -127o 970 0.804 H2O, EtOH

1-butanol 74.12 -900 117.70 0.810 EtOH

methanol 32.04 -98 64.6 0.791 Water, ethanol

1. do not plug mantle directly electric outlet, use controller

2. Use 40/60 mol percent 1-propanol/1-butanol (no cyclohexane or toluene) – less

toxic

3. Set up fractional distillation (OP27)

4. Set heat at highest level to start, insulate distillation column with glass wool

after boiling begins to save time

5. not too fast or slow, distillation should take about 30 min

6. turn back down to 60-80% when vapor starts up column, collect first sample

then adjust heat as needed

7. 40/60 solution is standard

8. write procedure during distillation not when finished you may split page,

left side procedure, right side table (no scratch paper)

Additional material for Postlab Report1. Retention times

2. C and XP,v (mole fraction of propanol vapor), and XB,v (mole fraction of butanol vapor).

Exp. G notes Fractional Distillation, 30Aug2004 page 2

3. table with area of propanol (AP), area of butanol (AB), AP/AB, R, XP (mole fraction of propanol), and XB (mole fraction of butanol).

sample standard 1

AP

AB

AP/AB

R

XP

XB

4. example of each calculation.

5. plot of boiling point versus volume

6. calculate HETP

7. copy of chromatograms

Exp. G notes Fractional Distillation, 30Aug2004 page 3

Calculation of Theoretical plates from mole fractions

1. theoretical plate – result of simple distillation

2. each distillation (plate) creates vapor more rich in more volatile component

3. column can have several theoretical plates

4. n is total theoretical plates in apparatus

5. n-1 is total theoretical plates of column

6. determine n from mole fraction (X) of components

Use complete equation on OP 27.

is the volatility ratio = 1.49

nP = moles of propanol, nB = moles of butanol

XP,v and XB,v = mole fractions in the vapor at the top of the column, XP,l and XB,l = mole fractions in the pot

For this experiment XP,v and XB,v are obtained from first fraction, XP,l and XB,l are obtained from original mixture

Calculation of mole fractions from GC data

(AP/nP)std = (AP/nP)sample and (AB/nB)std = (AB/nB)sample

(AP/nP)std/(AB/nB)std = (AP/nP)sample /(AB/nB)sample

(nP/nB)sample = R = (AP/AB)sample*(AB/nB)std/(AP/nP)std = (AP/AB)sample*(AB/AP)std*(nP/nB)std

AP = area of propanol under peak, AB = area of butanol under peak

Exp. G notes Fractional Distillation, 30Aug2004 page 4

XP + XB = 1, XB = 1 - XP

Let C = (AB/AP)std*(nP/nB)std = a calibration factor from standard

Then R = (AP/AB)sample*C

(mole ratio) = (area ratio of sample)*(calibration factor)

R can be used to calculate mole fractions XP and XB