Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. It is a special type of distillation. Generally the component parts boil at less than 25°C from each other under a pressure of one atmosphere (ATM). If the difference in boiling points is greater than 25°C, a simple distillation is used. A chemical compound is a chemical substance consisting of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ... Laboratory distillation set-up using, without a fractionating column 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed... Laboratory distillation set-up using, without a fractionating column 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed...

Laboratory setup

Fractional distillation in a laboratory makes use of common laboratory glassware, as well as some single-purpose items like a fractionating column and "pigs" and "cows" used to cut fractions. A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ...

Apparatus

Fractional distillation apparatus using a Liebig condenser. A conical flask is used as a receiving flask. Here the distillation head and fractionating column are combined in one piece.

• heat source, such as a hot plate with a bath: open flames are not recommended
• distilling flask, typically a round-bottom flask
• receiving flask, often also a round-bottom flask
• fractionating column (Vigreux column)
• distillation head
• thermometer and adapter if needed
• condenser
  • Liebig condenser,
  • Graham condenser, or
  • Allihn condenser
• vacuum adapter (not used in upper right image)
• boiling chips, also known as anti-bumping granules
• rubber bungs, unless laboratory glassware with ground glass joints is used, such as quickfit apparatus.

Diagram , drawn by theresa knott. ... Diagram , drawn by theresa knott. ... Liebig condenser The Liebig condenser or straight condenser is a piece of laboratory equipment consisting of a straight glass tube surrounded by a water jacket. ... Erlenmeyer flask An apparatus feeding into an Erlenmeyer flask An Erlenmeyer flask (also called conical flask) is a type of laboratory glassware which consists of an inverted conical base with a cylindrical neck. ... A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ... A hot plate is a small electric stove often used in a laboratory setting to heat glassware. ... Round-bottom flasks are types of flasks having spherical bottoms used as laboratory glassware, mostly for chemical or biochemical work. ... A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ... A Vigreux column is a type of fractionating column. ... It has been suggested that List of temperature sensors be merged into this article or section. ... Look up condenser in Wiktionary, the free dictionary. ... Liebig condenser The Liebig condenser or straight condenser is a piece of laboratory equipment consisting of a straight glass tube surrounded by a water jacket. ... A Graham condenser in the first configuration is used to prevent the toluene from boiling away while it is being refluxed. ... The Allihn condenser or bulb condenser is a type of laboratory glassware. ... Boiling chips are small, irregularly shaped stones used to prevent bumping of liquids during heating, boiling, or distillation. ... A jug with a cork bung. ... Brown glass jars with some clear lab glassware in the background Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratories. ... A reflux set-up with conically-tapered ground glass joints connecting the Graham condenser with the vacuum adapter (top) and two-necked flask. ... Quickfit is a system (and manufacturer) of laboratory equipment, which as its name suggests fits together quickly (and easily). ...

Method

As an example, consider the distillation of a mixture of water and ethanol. Ethanol boils at 78.5 °C while water boils at 100 °C. So, by gently heating the mixture, the most volatile component will concentrate to a greater degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component. In this example, a mixture of 95% ethanol and 5% water boils at 78.2 °C, being more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanol-water mixtures. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Grain alcohol redirects here. ... This article needs more context around or a better explanation of technical details to make it more accessible to general readers and technical readers outside the specialty, without removing technical details. ...

The apparatus (the diagram represents a batch apparatus, as opposed to a continuous apparatus) is assembled as in the diagram. The mixture is put into the round bottomed flask along with a few anti-bumping granules, and the fractionating column is fitted into the top. As the mixture boils, vapor rises up the column. The vapor condenses on the glass platforms, known as trays, inside the column, and runs back down into the liquid below, refluxing distillate. The column is heated from the bottom. The hottest tray is at the bottom and the coolest is at the top. At steady state conditions, the vapor and liquid on each tray are at equilibrium. Only the most volatile of the vapors stays in gaseous form all the way to the top. The vapor at the top of the column, then passes into the condenser, which cools it down until it liquefies. The separation is more pure with the addition of more trays (to a practical limitation of heat, flow, etc.) The condensate that was initially very close to the azeotrope composition becomes gradually richer in water. The process continues until all the ethanol boils out of the mixture. This point can be recognized by the sharp rise in temperature shown on the thermometer. Boiling chips are small, irregularly shaped stones used to prevent bumping of liquids during heating, boiling, or distillation. ... A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ... A theoretical plate in many separation processes is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other. ... Diagram of typical reflux apparatus. ... Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquid and its vapor (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapor) equals the rate of condensation (vapor changing to liquid) on a molecular... This article or section does not cite its references or sources. ... Look up condenser in Wiktionary, the free dictionary. ... It has been suggested that List of temperature sensors be merged into this article or section. ...

In laboratory distillation, several types of condensers are commonly found. The Liebig condenser is simply a straight tube within a water jacket, and is the simplest (and relatively least expensive) form of condenser. The Graham condenser is a spiral tube within a water jacket, and the Allihn condenser has a series of large and small constrictions on the inside tube, each increasing the surface area upon which the vapor constituents may condense. Liebig condenser The Liebig condenser or straight condenser is a piece of laboratory equipment consisting of a straight glass tube surrounded by a water jacket. ... A water jacket is a water-filled void surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through the void. ... A Graham condenser in the first configuration is used to prevent the toluene from boiling away while it is being refluxed. ... The Allihn condenser or bulb condenser is a type of laboratory glassware. ...

Alternate set-ups may utilize a "cow" or "pig" which is connected to three or four receiving flasks. By turning the "cow" or "pig", the distillates can be channeled into the appropriate receiver. A vacuum may be applied through a hose barb at the "cow" or "pig" to allow distillations to occur at lower temperatures.

Industrial distillation

Image 2: Typical industrial fractional distillation columns

Distillation is the most common form of separation technology used in petroleum refineries, petrochemical and chemical plants and natural gas processing plants.^[1][2] In most cases, the distillation is operated at a continuous steady state. New feed is always being added to the distillation column and products are always being removed. Unless the process is disturbed due to changes in feed, heat, ambient temperature, or condensing, the amount of feed being added and the amount of product being removed are normally equal. This is known as continuous, steady-state fractional distillation. Image File history File linksMetadata Download high-resolution version (1609x2120, 552 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Distillation Fractional distillation Fractionating column User talk:Shanel Reflux Continuous distillation User talk:Randfan/Super Desk Metadata This... Image File history File linksMetadata Download high-resolution version (1609x2120, 552 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Distillation Fractional distillation Fractionating column User talk:Shanel Reflux Continuous distillation User talk:Randfan/Super Desk Metadata This... View of Shell Oil Refinery in Martinez, California. ... Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ... A Chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. ... A natural gas processing plant Natural gas processing plants are used to purify the raw natural gas extracted from underground gas fields and brought up to the surface by gas wells. ... Continuous distillation is a distillation process, which does not require interruption for adding raw material. ... HELLO EVERYONE!! Steady state is a more general situation than Dynamic equilibrium. ...

Industrial distillation is typically performed in large, vertical cylindrical columns known as "distillation or fractionation towers" or "distillation columns" with diameters ranging from about 65 centimeters to 6 meters and heights ranging from about 6 meters to 60 meters or more. The distillation towers have liquid outlets at intervals up the column which allow for the withdrawal of different fractions or products having different boiling points or boiling ranges. The "lightest" products (those with the lowest boiling point) exit from the top of the columns and the "heaviest" products (those with the highest boiling point) exit from the bottom of the column. Alternate use: Boiling Point, English title of Kitano Takeshis film 3-4X Jūgatsu; Boiling Point (TV series) The boiling point of a substance is the temperature at which it can change state from a liquid to a gas throughout the bulk of the liquid. ...

For example, fractional distillation is used in oil refineries to separate crude oil into useful substances (or fractions) having different hydrocarbons of different boiling points. The crude oil fractions with higher boiling points: View of Shell Oil Refinery in Martinez, California. ... Pumpjack pumping an oil well near Sarnia, Ontario Petroleum (from Greek petra – rock and elaion – oil or Latin oleum – oil ) or crude oil is a thick, dark brown or greenish liquid. ... In chemistry, a hydrocarbon is a cleaning solution consisting only of carbon (C) and hydrogen (H). ...

• have more carbon atoms
• have higher molecular weights
• are darker in color
• are more viscous
• are more difficult to ignite and to burn

Figure 1: Diagram of a typical industrial distillation tower

Large-scale industrial towers use reflux to achieve a more complete separation of products. Reflux refers to the portion of the condensed overhead liquid product from a distillation or fractionation tower that is returned to the upper part of the tower as shown in the schematic diagram of a typical, large-scale industrial distillation tower. Inside the tower, the reflux liquid flowing downwards provides the cooling needed to condense the vapors flowing upwards, thereby increasing the effectiveness of the distillation tower. The more reflux is provided for a given number of theoretical plates, the better the tower's separation of lower boiling materials from higher boiling materials. Alternatively, the more reflux provided for a given desired separation, the fewer theoretical plates are required. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... Viscosity is a measure of the resistance of a fluid to deform under shear stress. ... Ignition occurs when the heat produced by a reaction becomes sufficient to sustain the reaction, whether it be a fire, an explosion, or nuclear fusion. ... Image File history File links Distillation_Column. ... Diagram of typical reflux apparatus. ... A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ...

Fractional distillation is also used in air separation, producing liquid oxygen, liquid nitrogen, and high purity argon. Distillation of chlorosilanes also enable the production of high-purity silicon for use as a semiconductor. General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. ... It has been suggested that Silicons ranking be merged into this article or section. ... A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ...

In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This packing material can either be random dumped packing (1-3" wide) such as Raschig rings or structured sheet metal. Typical manufacturers are Koch, Sulzer and other companies. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Unlike conventional tray distillation in which every tray represents a separate point of vapor liquid equilibrium he vapor liquid equilibrium curve in a packed column is continuous. However, when modeling packed columns it is useful to compute a number of "theoretical plates" to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance. Raschig rings are referred to as random packing and are used in commercial fractional distillation columns to reduce pressure loss (versus using trays), while maintaining good efficiency and economy. ... The term Structured packing refers to a range of specially designed materials for use in distillation columns and chemical reactors. ... Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ... Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquid and its vapor (gas phase) are in equilibrium with each other, in a state where the rate of evaporation (liquid changing to vapor) equals the rate of condensation (vapor changing to liquid) on a molecular level... A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ...

Design of industrial distillation columns

Design and operation of a distillation column depends on the feed and desired products. Given a simple, binary component feed, analytical methods such as the McCabe-Thiele method^[2][3][4] or the Fenske equation^[2] can be used. For a multi-component feed, simulation models are used both for design and operation. The graphical approach presented by McCabe and Thiele in 1925, the McCabe-Thiele Method is considered the simplest and perhaps most instructive method for analysis of binary distillation. ... The Fenske equation in fractional distillation is an equation for calculating the minimum number of theoretical plates required for separation of a binary feed stream by a fractionation column operated at total reflux (i. ... Look up simulation in Wiktionary, the free dictionary. ...

Figure 2: Chemical engineering schematic of typical bubble-cap trays in a distillation tower

Moreover, the efficiencies of the vapor-liquid contact devices (referred to as plates or trays) used in distillation columns, as seen in Figure 2, are typically lower than that of a theoretical 100% efficient equilibrium stage. Hence, a distillation column needs more plates than the number of theoretical vapor-liquid equilibrium stages. Image File history File links Tray_Distillation_Tower. ... A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ...

An indication of numbers: the separation of two compounds with relative volatility of 1.1 requires a minimum of 130 theoretical plates with a minimum reflux ratio of 20.^[5]. With a relative volatility of 4, the required number of theoretical plates decreased to 9 with a reflux ratio of 0.66. In another source, a boiling point difference of 30°C requires 12 theoretical plates and, for a difference of 3°C, the number of plates increased to 1000.^[6] Volatility most frequently refers to the standard deviation of the change in value of a financial instrument with a specific time horizon. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ...

The reflux ratio is the ratio of the amount of moles returned as refluxed liquid to the fractionating column and the amount of moles of final product, both per unit time.

See also

• Azeotropic distillation
• Batch Distillation
• Distillation
• Extractive distillation
• Fractionating column
• Freeze distillation
• Raschig rings
• Steam distillation
• Vacuum distillation

In chemistry, azeotropic distillation is any of a range of techniques used to break an azeotrope in distillation. ... Bold textBold textBatch distillation[1] refers to the use of distillation, the separation of components in a system by volatilities, in batches. ... Laboratory distillation set-up using, without a fractionating column 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed... Extractive Distillation is defined as distillation in the presence of a miscible, high boiling, relatively non-volatile component, the solvent, that forms no azeotrope with the other components in the mixture. ... A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ... It has been suggested that this article or section be merged into Fractional freezing. ... Raschig rings are referred to as random packing and are used in commercial fractional distillation columns to reduce pressure loss (versus using trays), while maintaining good efficiency and economy. ... Laboratory set-up for steam distillation Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds. ... This article or section does not cite its references or sources. ...

External links

• Validating Your Binary VLE Data

References

1. ^ Kister, Henry Z. (1992). Distillation Design, 1st Edition, McGraw-Hill. ISBN 0-07-034909-6. 
2. ^ ^{a b c} Perry, Robert H. and Green, Don W. (1984). Perry's Chemical Engineers' Handbook, 6th Edition, McGraw-Hill. ISBN 0-07-049479-7. 
3. ^ Beychok, Milton (May 1951). "Algebraic Solution of McCabe-Thiele Diagram". Chemical Engineering Progress. 
4. ^ Seader, J. D., and Henley, Ernest J. (1998). Separation Process Principles. New York: Wiley. ISBN 0-471-58626-9. 
5. ^ Editors: Jacqueline I. Kroschwitz and Arza Seidel (2004). Kirk-Othmer Encyclopedia of Chemical Technology, 5th Edition, Hoboken, NJ: Wiley-Interscience. ISBN 0-471-48810-0. 
6. ^ Arthur I. Vogel and Brian S. Furnis (1988). Vogel's Textbook of Practical Organic Chemistry, 5th Edition, London: Longman Scientific & Technical. ISBN 0-582-46236-3.