Simple Distillation
- Simple and Fractional Distillation
Distillation is a purification technique in which compounds with different boiling points can be separated by controlled
heating. Vapors from a sufficiently heated sample can be recondensed and collected, purer than the initial mixture.
A methanol/water mixture will be distilled twice to compare the efficiencies of two slightly different physical setups - the second involving the insertion of a fractionating column.
Simple Distillation
Distillation
I. Basic Distillation Process (temperature and pressure dependent) A. Physical set-up
B. Temperature control liquid vapor vapor liquid
heat sample to boiling, vapors migrate through system, condenser cools vapors C. Industrial-scale distillations: petroleum refineries (hydrocarbons)
alcoholic beverage distilleries (ethanol)
refine.htm
What is Distillation?
• A separation technique
• Distillation:
• Two types:
1. Simple – separate liquids with b.p.
differences
2. Fractional separate liquids with b.p.
differences
Simple Distillation Setup
Simple Distillation Setup
ringstand lab jack
Corning hotplate/stirrer Thermowell heating unit
25-mL RB flask with stirring bar metal clamp
three way adapter (distillation head)
"cooking" thermometer probe plastic Keck clips (2)
water-cooled condenser vacuum take-off adapter sample vial (collector) 1
4 2 3
5 6 7 8 9 10 11 12
7
11 10
Plug Thermowell
into Variac
Cold water
Simple Distillation Setup
-
1 4
2 3 6 5
7
8
9
10
11
12 9
H2O
ringstand lab jack
Corning hotplate/stirrer Thermowell heating unit
25-mL RB flask with stirring bar metal clamp
three way adapter (distillation head)
"cooking" thermometer probe plastic Keck clips (2)
water-cooled condenser vacuum take-off adapter sample vial (collector) 1
4 2 3
5 6 7 8 9 10 11 12
- -
Heating Apparatus
silicone oil bath
heating mantle Thermowell
Corning stirrer/hot plate
A stirred silicone oil bath, heated on a hot plate, will distribute heat more evenly
and the temperature can be directly monitored by a
thermometer.
Simple Distillation Set-Up
Keck Clip H2O In
H2O Out Thermometer Distillation
Head
Vacuum Distillation Head
Graduated Cylinder (collects distillate)
1. Assemble the
empty apparatus
Keck Clip H2O In
H2O Out
Vacuum Distillation Head
Simple Distillation Set-Up
2. Remove the
boiling flask
Simple Distillation Set-Up
3. Add mixture and reattach boiling flask
Keck Clip H2O In
H2O Out
Vacuum Distillation Head
Simple Distillation Set-Up
Keck Clip H2O In
H2O Out Thermometer Distillation
Head
Vacuum Distillation Head
Graduated Cylinder (collects distillate)
4. Raise the
heating mantle
Fractional Distillation Set-Up
* Note Keck clip
and placement of clamp
Keck Clip
H2O In H2O Out
What is Boiling?
Evaporation:
Boiling:
Simple vs. Fractional Distillation
• Ideally a distillation will efficiently separate liquids in the order of increasing bp’s.
• Actually incomplete separations (with sample overlap) often occur, especially with liquids of similar bp’s and/or physical apparatus of lesser fractionating capability.
• Typically expect to observe a fairly steady boiling range of 2-5°C for the collection of the majority of distillate (broader boiling ranges indicate less pure samples).
method bp difference typical use
simple distillation 50°C or more initial sample clean up fractional distillation 10°C or more finer separations
Fractional Distillation
Factors influencing the effectiveness of a distillation:
(how well a sample can be purified by distillation)
1. type of mixture - the greater the difference in the boiling points of two compounds the easier it is to separate them by distillation
*2. physical setup - not only does the setup enclose and direct the migration of vapors, it provides an internal surface to promote vapor/liquid equilibria, helping establish a temperature gradient
3. temperature control - more defined vapor/liquid equilibria and
temperature gradients can be established if heat is not applied
too quickly and insulation is used to minimize temp. fluctuations
Distillation of a Methanol/Water Mixture
X % CH3OH (methanol) 65C {10 mL mixture}
(100-X) % H2O (water) 100C Data collection - Temperature vs. Volume
Volume (mL)
Temp. (C) {Theory}
Temp. (C) {Simple}
Temp. (C) {Fraction.}
Plotted Distillation Data
0.5 100
1.0
1.5 Temp. (C)
2.0
. . . 65
Volume (mL)
Excel Plot of Distillation Data
Volume Temp. Temp. Temp.
(mL) Theory Simple Fract.
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
Type of % MeOH
Column: _________________________ determined _____ %
Distillation of Methanol/Water Mixture
60 65 70 75 80 85 90 95 100 105
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Volum e (m L)
Temp. (C)
Theory Simple Fract.
Insert your distillation data;
the Excel program will automatically
plot the results.
