Distillation Of Alcoholic Beverages 505j14

Distillation of Alcoholic Beverages Maria Salvacion A. Esmalla, M.Sc. Department of Biochemistry Faculty of Pharmacy, UST

Objectives •

Separate the components of alcoholic beverage using distillation

•

Construct a distillation curve

•

Calculate the percent ethanol in the alcoholic beverage

•

Compare the efficiency of simple and fractional distillation in separating liquid mixture

Distillation • process of heating a liquid until its more volatile constituents into the vapor phase, and then cooling the vapor to recover such constituents in liquid form by condensation. • the main purpose of distillation is to separate a mixture of several components by taking advantage of their different volatilities, or the separation of volatile materials from nonvolatile materials.

Types of Distillation Simple Distillation – Used to separate mixtures of liquids with a large difference in volatility

Fractional Distillation – Used when liquids have close boiling points – Repeated distillation

Steam Distillation – ing steam through liquid mixture

Vacuum Distillation – Distilling at a low pressure for components to boil at lower boiling point – Useful for compounds that degrade at high temperatures

Simple Distillation Set-up 4

3

2

5 7

1 8 6

9

1. 2. 3. 4. 5. 6. 7. 8. 9.

Distilling flask Distilling head Thermometer packet Thermometer Condenser Cooling water in Cooling water out Adapter Receiving flask

Fractional Distillation Set-up 5

4 8 3

7 6

9

2

10

1

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Distilling flask Fractionating column Distilling head Thermometer packet Thermometer Condenser Cooling water in Cooling water out Adapter Receiving flask

Vapor Pressure • is the equilibrium pressure of a vapor above its liquid • As temperature increases vapor pressure also increases

Boiling Point • Temperature at which vapor pressure equals atmospheric pressure (1 atm) • Varies significantly with pressure • Characterized as vigorous bubbling of liquid as it vaporizes

Dalton’s Law • Total pressure is equal to the sum of the partial pressures of all gases PT = P1 + P2 + P3 + P4 + …

Raoult’s Law • For liquid mixtures, the partial pressure of liquid A (PA) is equal to the vapor pressure of the pure liquid A (P°A) multiplied by its mole fraction (XA) in the mixture PA = XAP°A • For mixture of liquid A and B, PT = PA + PB= XAP°A + XBP°B

Liquid-Vapor Phase Diagram • Shows the temperature at which a mixture with a certain composition starts to boil Boiling point of pure B Vapor composition line

Liquid composition line Boiling point of pure A

Liquid-Vapor Phase Diagram 100

T E M P E R A T U R E

90

80

100 A

80 A 20 B

60 A 40 B

40 A 60 B

COMPOSITION (%)

20 A 80 B

100 B

Liquid-Vapor Phase Diagram

Methodology 15 mL of test sample + boiling chips

distill Stop when: * the temperature reaches 100°C * the volume of the sample remaining in the flask is approximately 1-2 mL

DISTILLATE - Collect 0.5 mL using the calibrated test tubes - Record the temperature for each fraction collected - Perform flammability test ©Mr. A. R. M. Salcedo

RESIDUE - Measure volume remaining in the flask

Boiling Chips • Porous rock that releases bubbles of entrapped air to the solution being heated • Prevents bumping • Promotes smooth boiling • Porcelain, glass, unglazed clay, alumina • Do not add boiling chips when solution is hot

Data and Results Test tube

mL

1

0

1

0.5

test positive with the flammability test

2

1.0

» Compute the percent ethanol in your

3

1.5

sample

4

2.0

5

2.5

6

3.0

7

3.5

» Measure the volume of sample

8

4.0

9

4.5

remaining in the flask, and add it to the total volume of the distillate (Ved)

10

5.0

11

5.5

12

6.0

13 7.0 ©Mr. A. R. M. Salcedo

Temp

Confirmatory test

» Get the volume of the distillate that will

Volume of ethanol % ethanol =

Volume of sample

» Compute the percent loss % loss =

Vol of sample - Ved Volume of sample

Data and Results DISTILLATION CURVE

TEMPERATURE

VOLUME OF DISTILLATE

Simple Distillation Curve

Fractional Distillation Curve

Comparison of Results GROUP 1 2 3 4 5 6 7 8 9 10

SAMPLE

% EtOH (Actual)

TYPE

% EtOH (Experimental)

Fractional Distillation

Fractional Distillation

Fractional Distillation EFFICIENCY - refers to how well a fractionating column can separate components of a liquid mixture

- depends on: Length ► Packing material ► Reflux ratio ►

- reported in theoretical plates

Theoretical Plates - is the number of steps needed to bring about a specified degree of separation of two components in a mixture.

Theoretical Plates • NUMBER OF THEORETICAL PLATES NEEDED TO SEPARATE A BINARY MIXTURE Number of TP

Approx. bp difference (oC)

1

100

5

35

10

20

50

4

100

2

Theoretical Plates CHARACTERISTICS OF SOME FRACTIONATING COLUMNS Holdup (mL)

Theoretical Plates (TP)

Height of Each TP (cm)

Separable Bp diffrnce (oC)

1.5

3

8

50

Glass helices

5

6

4

30

Metal sponge

9

6

4

30

Spinning band

0.2

11-61

0.4-2

3-20

Type of column

Vigreux

Azeotropes • Greek for ‘no change in boiling’ • is a mixture of two or more solvents in such a ratio that its composition cannot be changed by simple distillation • when boiled, the resulting vapor has the same ratio of constituents as the original mixture of liquids • also known as constant boiling mixtures

Positive Azeotropes •also called minimum boiling azeotrope •boils at a lower temperature than any other ratio of its constituents • strong intermolecular attraction with similar molecules

azeotrope

Example: 95.6% ethanol / 4.4% water BptetOH = 78.4°C Bptwater = 100°C

©Mr. A. R. M. Salcedo

Bptazeotrope = 78.1°C Boiling point of liquid Vapor composition

Negative Azeotropes •also called maximum boiling azeotrope •boils at a higher temperature than any other ratio of its constituents

azeotrope

•strong intermolecular attraction with different molecules Example: 20.2% hydrogen chloride / 79.8% water BptHCl = -84°C Bptwater = 100°C Boiling point of liquid Vapor composition

The End “Nothing is as hard as it looks; everything is more rewarding than you expect; and if anything can go right it will and at the best possible moment.”