Principles and Methodology of Different Types of Distillation.pptx

Presented By:- Akanksha Kumari (CUPB)
BASIC PRINCIPLES AND METHODOLOGY OF :-
1.Fractional distillation
2.Distillation under reduced
pressure
3.Steam distillation
4.Molecular distillation
Presented by:- Akanksha Kumari
Central University of Punjab
(B. Pharmacy, 2024-28)

1.Fractional Distillation:-
Principle:-
• Fractional distillation is the separation of a
mixture of liquids with different boiling points
by heating the mixture and allowing the
components to vaporize at different
temperatures.
Fig.:- Fraction distillation
assembly

Construction:-
• Heat source: Boils the liquid mixture (e.g., a burner or
heating mantle).
• Distillation flask: Holds the liquid mixture to be heated.
• Fractionating column: The core of the setup. It's a
vertical tube packed with materials like glass beads,
rings, or stones that provide a large surface area. This
allows for repeated cycles of vaporization and
condensation, which separates components with close
boiling points.
• Thermometer: Placed at the top of the fractionating
column to monitor the temperature of the vapor that is
about to enter the condenser.
• Condenser: A separate tube with a cool surface that
cools the vapor, causing it to condense back into a liquid.
Cold water is often circulated around it for this purpose.
• Receiver flask: The flask where the purified liquid
(distillate) is collected. Presented By:- Akanksha Kumari (CUPB)

Different types of fractionating columns:-
Packed Columns:-
• Filled with packing materials (e.g., glass
beads, Raschig rings, steel wool) to increase
the surface area for vapor-liquid contact.
• Separating mixtures with components that
have close boiling points due to the high
surface area.
Tray Columns:-
• Consist of a series of trays or plates installed at
intervals inside the column. Vapor rises and
passes through the liquid on each tray, leading to
repeated cycles of condensation and vaporization
• Large-scale industrial applications and separating
mixtures with varying properties.
Fig.- Packed column
Fig.- tray Column

Working:-
• Heating the mixture: The liquid mixture is placed in a
distillation flask and heated.
• Vaporization: As the mixture heats, the components begin to
vaporize. The liquid with the lower boiling point vaporizes first.
• Rising through the column: The vapor rises, travels up a
fractionating column which is filled with material like glass
beads that provide a large surface area, and then condenses
into a separate liquid at the top of the column.
• Repeated condensation and vaporization: The temperature
decreases as the vapor rises. At different levels, the vapor
cools, condenses, and then re-vaporizes . This process of
vaporization and condensation repeats multiple times in the
column, leading to a more complete separation of the
components.
• Condensation: Eventually, the vapor reaches the top of the
column and enters a condenser.
• Collection: The condenser cools the vapor into a liquid, which
is then collected in a receiving flask as the distillate. The
components with higher boiling points remain in the
distillation flask or condense lower in the column.
Fig.- Fractional Distillation Assembly

Advantages
Efficient separation: It can effectively separate liquids with close boiling points, which
simple distillation cannot do as well.
High purity: It can produce very pure fractions of the original mixture.
Wide applications: It is used to separate complex mixtures like crude oil into useful
products such as gasoline, kerosene, and diesel.
Disadvantages
Energy-intensive: The process requires a significant amount of heat and energy.
Slower process: It takes more time to complete the separation compared to simple
distillation.
Complex and expensive setup: The apparatus is more complicated, requiring a
fractionating column, which makes it more expensive to set up.
Potential for error: If the system is not properly monitored, the separation may be
poor, resulting in impure fractions.

2.Distillation under Reduced Pressure:-
Principle:-
• Boiling of a liquid occurs when a liquid's vapor
pressure equals to the atmospheric pressure
I.e. pressure on it’ s surface. By reducing the
external pressure on the liquid by applying
vacuum, the boiling point of liquid is decreased.
Therefore, allowing it to be distilled at a lower
temperature than its normal boiling point.

Construction:-
• Distillation flask: Holds the liquid to be distilled and is placed on a
heating source.
• Thermometer: Measures the temperature of the vapor. It is placed
at the junction where the vapor enters the condenser.
• Capillary tube: (Optional) Used to regulate the boiling process and
prevent bumping.
• Condenser: A glass tube with an outer jacket through which cold
water flows to cool the vapor into a liquid.
• Receiver: A flask or beaker that collects the purified distillate.
• Vacuum pump: Connected to the receiver, this removes air from the
system to lower the pressure.
• Manometer: Measures the pressure inside the system to ensure it is
being lowered correctly.
Working:-
• Boiling of a liquid occurs when a liquid's vapor pressure equals to the
atmospheric pressure I.e. pressure on it’ s surface.
• By reducing the external pressure on the liquid by applying vacuum,
the boiling point of liquid is decreased.
• Therefore, allowing it to be distilled at a lower temperature than its
normal boiling point.

Advantages:-
• This is especially useful for purifying high-boiling-point liquids.
• Those compounds that would decompose at their normal boiling
temperature can be distilled by this method.
Disadvantages:-
• High energy consumption for pumps: Vacuum pumps require a
significant amount of energy to operate and maintain the necessary low
pressure.
• Potential for leaks: Any leaks or cracks in the system can cause pressure
loss, leading to reduced efficiency and potentially hazardous conditions.
• Complex setup: The equipment required is more complex than for
standard distillation, as it must include a vacuum pump, a manometer,
and specialized flasks to handle the reduced pressure.
• Pressure control is critical: The entire process is dependent on
maintaining a precise pressure, so any fluctuations can negatively impact
the separation process.

3.Steam Distillation:-
Principle:-
• Steam distillation is a separation technique
used to extract temperature-sensitive
compounds, like essential oils, by passing
steam through the material to vaporize
volatile compounds at a temperature below
their boiling points. The resulting vapor is then
condensed and collected, separating the
immiscible organic compound from water.
• This method is valuable because it avoids
thermal decomposition, making it ideal for
natural products and complex organic
synthesis. Fig.: Steam Distillation
Assembly

Construction:-
• Boiler: A separate vessel used to heat water and
produce steam. This can be a simple kettle or a
larger industrial steam generator.
• Extractor (or Still):This is the main vessel where the
plant material or mixture is placed. It is often a large,
jacketed kettle that allows for heating or cooling of
the contents . It has an inlet for steam and an outlet
for the vapor mixture to exit.
• Condenser : A cooling coil or jacketed tube that
cools the steam and volatile vapors, causing them to
condense into a liquid. Water is circulated through
the condenser jacket to facilitate cooling.
• Receiver (or Separator):A vessel for collecting the
condensed liquid mixture. A Florentine receiver is
commonly used for immiscible liquids like oil and
water, as it separates the two layers based on
density. There are different types of Florentine
receivers for separating oils that are denser or less
dense than water.
Fig.: Steam Distillation
Assembly
Fig.: Florentine Receiver

Working:-
• Steam generation: Water is heated in the steam
generator to produce steam.
• Vaporization: The steam is directed into the
extraction flask, passing through the plant material or
liquid mixture.
• Co-distillation: The hot steam carries the volatile
compounds from the material with it, forming a vapor
mixture. This occurs at a lower temperature than if the
liquid were boiled directly, which prevents heat-
sensitive compounds from decomposing.
• Condensation: The steam and compound vapor
mixture travels into the condenser, where it is cooled
by circulating cold water.
• Collection and separation: The cooled mixture, now
a liquid, is collected in a separator. Since the organic
compound is often immiscible with water, two
separate layers form. The oil, which is often less dense
than water, floats on top and can be easily separated.
Fig.: Steam Distillation Assembly

Advantages:-
• Extracts heat-sensitive compounds: It allows for the vaporization of
compounds with high boiling points at lower temperatures (below 100°C)
by using the vapor pressure of steam, which prevents thermal
decomposition.
• Separates immiscible liquids: The process is highly effective for
separating substances that do not mix with water, such as essential oils
from plant material.
Disadvantages:-
• Time-consuming: The process can take a long time, especially on an
industrial scale, because the steam needs time to pass through the
material and carry the volatile components out.
• Energy-intensive: Generating and maintaining the steam requires a
significant amount of energy.
• Limited applicability: It is not suitable for compounds that are soluble in
water or for substances that decompose or react with water or steam.

4.Molecular Distillation:-
Principle:-
• The substances to be distilled have very low vapour
pressures (examples are:- viscous liquids, oils,
greases, waxy materials and high molecular weight
substances). Therefore they boil at very high
temperatures. In order to decrease the boiling point
of the liquids high vacuum must be applied.
• Molecular distillation is defined as a distillation
process in which each molecule in the vapour phase
travels mean free path and gets condensed
individually without intermolecular collisions on
application of vacuum. It separates substances
based on their mean free paths rather than their
boiling point as in conventional distillation.

Construction:-
•Heated evaporation surface: A heated surface, sometimes with a
jacket for temperature control, is where the liquid is fed and evaporates.
In falling film stills, wipers create a thin film to maximize surface area
and prevent non-volatile buildup.
•Condenser: A very closely positioned condenser cools the vapor,
which then condenses on its surface. The short distance between the
evaporator and condenser is crucial and is typically only a few
centimeters.
•High vacuum system: The apparatus is operated under a very high
vacuum (e.g.:-10 mmHg or lower). This reduces pressure so the mean
⁻⁴
free path of the molecules is greater than the distance between the
evaporator and condenser, allowing them to travel directly to the
condenser without colliding with other molecules or gas.
•Collection system: Separate outlets are needed to collect the
condensed distillate and the undistilled liquid residue, which is often a
non-volatile or less-volatile material.

Working:-
• The liquid mixture is fed onto a heated surface, which
can be a falling film or a rotating surface in a
centrifugal system.
• The heat causes molecules to evaporate and enter the
vapor phase.
• Because of the high vacuum and short path, the
molecules can travel to the condenser without colliding
with each other.
• Lighter molecules, which have a longer mean free path,
reach the cold condenser surface and condense, while
heavier molecules do not travel as far and are collected
separately.
• This difference in molecular travel distance allows for
the separation and purification of the mixture.

Advantages:-
• Low-temperature processing: Enables separation of high-boiling point, heat-
sensitive, or easily oxidized compounds by operating at low temperatures.
• High purity: The high vacuum and short-path design leads to highly pure
products with minimal degradation.
• Short residence time: Material spends very little time on the heated surface,
significantly minimizing thermal damage or decomposition.
• Reduced degradation and oxidation: The high vacuum environment prevents
oxidative damage, preserving the product's quality.
• Environmentally friendly: Avoids the use of toxic solvents and does not create
residues.
• Efficient separation: It is highly effective at separating compounds with high
boiling points and high viscosity.
Disadvantages:-
• High equipment cost: The specialized equipment for molecular distillation is
expensive compared to traditional distillation systems.
• Complexity: It requires high vacuum conditions and skilled operators, making the
process more complex to manage.
• Limited scalability: It is not typically suitable for large-scale, low-value products
and is better for high-value applications like pharmaceuticals and fine chemicals.

THANK YOU!!

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