What Is Distillation?

Distillation is the process of separating a mixture into its components. This is done by heating the mixture to boiling point and channeling the vapor into a condenser where it cools and collects as liquid.


Medieval Muslim chemists like Jabir ibn Hayyan and Abu Bakr al-Razi experimented with distillation. As Europe emerged from the Dark Ages, their advancements found a wide audience among apothecaries and physicians.


Distillation is a separation technique that takes advantage of the fact that different substances have distinct boiling points. As a mixture is heated, the substance with the lowest boiling point will vaporize first. This vapor is then condensed back into a liquid, leaving the other component behind. The process can be used to separate a wide variety of substances, including liquids, gases, and solids. It is commonly used to purify water, alcohol, and petroleum products. It is also a common laboratory procedure for the separation of compounds.

The most common form of distillation involves a distillation column and a fractionating flask. The distillation column improves the separation by providing a greater surface area for the vapor to contact the condensed liquid. The column can even consist of multiple subsystems, each with its own vapor-liquid equilibrium.

During the distillation process, the composition of the vapor changes over time. This is because the more volatile component boils off earlier. The fresh vapors then have a higher concentration of the less volatile component. The process can be repeated to further enrich the vapor concentration until it reaches a theoretical plate.

For compounds that are air sensitive, a simple vacuum distillation system can be used. This system involves a glass tube with an inner and outer section. The vapor travels into the inner section and is then condensed into a liquid by cold water flowing through the outer section. This method can be a useful alternative to more expensive equipment, such as a Perkin triangle apparatus.


Distillation is widely used in chemical processes, including alcohol production, petroleum refining, and the production of essential oils. It is also often employed in scientific research to separate and purify chemicals. The process is based on heating a mixture of liquids or solids to produce vapor that can be separated from the liquid. In most cases, the vapor is rich in molecules from the more volatile component of the mixture, and the liquid contains the less-volatile components. In some cases, the mixture forms an azeotrope, a composition in which the boiling points of both pure components are equal. In these cases, the azeotropic distillation must be broken using techniques such as adding an extra component or varying the pressure.

A common method of distillation is to heat a mixture in a flask until it boils, and then let the vapor and liquid cool down separately. This is called batch distillation, and it can be performed with simple glassware. It is also possible to use a fractionating column on top of the distillation flask for improved separation. This system is often more efficient than a standard distillation apparatus, and it can be used to collect compounds that are air sensitive or have high boiling points.

One of the major costs of a refinery is energy, and 35% of that energy is consumed in the crude distillation process. Therefore, the optimisation of distillation systems is an important issue. This study aims to develop a model that can be used for the design and optimization of a CO cryogenic distillation process.

Gas-liquid equilibria

The separation of a mixture by distillation depends on the differences in concentrations of the components in the liquid and vapor phases. These differences are determined by the vapor pressures of the different chemicals in the mixture and their relative volatility. These differences are reflected in the mole fractions of the different components in each phase. For example, a mixture of benzene and toluene will contain more benzene in the vapor phase than toluene in the liquid phase, because benzene is more volatile than toluene.

The concentration distribution function is a key to the design of a distillation column. It can be derived from gas-liquid equilibrium theory and mass balance, as well as component equilibrium. The moving velocity of the concentration distribution curve is also a key factor in the nonlinear dynamic model of a distillation column.

To obtain accurate concentration distribution data, it is important to have the correct temperature measurement device in place. The instrument must be able to measure the boiling point of the solution and the temperature of the vapor bubble in contact with the liquid. The thermocouple will also need to be positioned correctly in order to accurately determine the temperature of the head. A PTFE valve plug, shown schematically in Figure 1, is used to fit into the neck of the condenser and complete the reflux junction. The plug incorporates a cylindrical channel that aligns with two adjoining branches of the reflux junction.

Idealized models

Distillation is one of the most common mass transfer operating units in petroleum refining and petrochemical plants. However, distillation is also one of the most energy-intensive processes. In order to improve the energy efficiency of the process, it is necessary to strengthen its operation control. This requires a highly effective model and control scheme. The model must be accurate and simplified enough to be useful.

The most efficient distillation processes use a retort, a pot with a lid, that can be heated and cooled in a water bath. Alternatively, a packed column is used for industrial applications. This type of column contains a packing material that allows for more efficient heat transfer. The packing material may be a random dumped packing (1-3″ wide) or structured sheet metal, such as Raschig rings. Liquids tend to wet the surface of the packing and vapors pass across this wetted surface, where mass transfer occurs. The resulting liquids are separated by boiling points, which are then enriched by the process.

Large-scale industrial distillation towers use a process called reflux to achieve more effective separations. Reflux is a flow from the condenser back down through the column, which generates a recycle that helps to separate higher-boiling materials from lower-boiling ones. Generally, the more reflux is provided for a given number of theoretical plates, the better the separation.