1: Stirrer bar/anti-bumping granules
2: Still pot
3: Fractionating column
4: Thermometer/Boiling point temperature
5: Condenser
6: Cooling water in
7: Cooling water out
8: Burrette
9: Tap
10: Collection vessel
The Dean-Stark apparatus or Dean-Stark receiver or distilling trap is a piece of laboratory glassware used in synthetic chemistry to collect water (or occasionally other liquid) from a reactor. Laboratory glassware refers to a variety of equipment traditionally made of Glass, used for Scientific experiments and other work in Science, especially In Chemistry, chemical synthesis is purposeful execution of Chemical reactions in order to get a product, or several products Water is a common Chemical substance that is essential for the survival of all known forms of Life. It is used in combination with a reflux condenser and a batch reactor for continuous removal of the water that is produced during a chemical reaction performed at reflux temperature. In a Laboratory, a condenser is a piece of Laboratory glassware used to cool hot vapors or liquids The Batch reactor is the generic term for a type of Vessel widely used in the process industries A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called This article is about using reflux in chemical engineering and chemistry Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature It was invented by E. W. Dean and D. D. Stark in 1920 for determination of the water content in petroleum[1].
Two types of Dean-Stark traps exist – one for use with solvents with a density less than water (shown in figure) and one for use with solvents with a density greater than water.
The Dean-Stark apparatus in the laboratory typically consists of vertical cylindrical piece of glass (the trap, above (9) in figure), often with a volumetric graduation on its full length and a precision tap on the bottom very much like a burette. A burette (also buret) is a vertical cylindrical piece of Laboratory glassware with a volumetric graduation on its full length and a precision tap or Stopcock The top of the cylinder is a fit with the bottom of the reflux condenser (5). Protruding from the top the cylinder has a side-arm sloping toward the reaction flask (2). At the end the side-arm makes a sharp turn so that the end of the side arm (3) is vertical as well. This end connects with the reactor.
During the reaction in (2), vapors containing the reaction solvent and the component to be removed travel out of reaction flask up into the condenser (5), and then drip into the distilling trap (above 9). Here, immiscible liquids separate into layers. Miscibility is a term commonly used in Chemistry that refers to the property of Liquids to mix in all proportions forming a Homogeneous Solution When the top (less dense) layer reaches the level of the side-arm it can flow back to the reactor, while the bottom layer remains in the trap. The trap is at full capacity when the lower level reaches the level of the side-arm--beyond this point, the lower layer would start to flow back into the reactor as well. It is therefore important to syphon or drain the lower layer from the Dean-Stark apparatus as much as needed.
More rarely encountered is the model for solvents with a density greater than water. This type has a tube at the bottom of the side-arm to allow the organic solvent at the bottom to flow back into the reaction vessel. The water generated during the reaction floats on top of the organic phase.
This piece of equipment is usually used in azeotropic distillations. In Chemistry, azeotropic distillation is any of a range of techniques used to break an Azeotrope in Distillation. A common example is the removal of water generated during a reaction in boiling toluene. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of An azeotropic mixture of toluene and water distills out of the reaction, but only the toluene (density=0. 865 g/ml) returns, since it floats on top of the water (density=0. 998 g/cm3), which collects in the trap. The Dean-Stark method is commonly used to measure moisture content of items such as bread in the food industry.
This equipment can be used in cases other than simple removal of water. One example is the esterification of butanol with acetic acid catalyzed by sulfuric acid. Butanol or butyl alcohol (sometimes also called biobutanol when produced biologically is a Primary alcohol with a 4 Carbon structure and the Molecular Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. The vapor contains 63% ester, 24% water and 8% alcohol at reflux temperature and the organic layer in the trap contains 86% ester, 11% alcohol and 3% water which is reintroduced. The water layer is 97% pure.
Another example is the esterfication of benzoic acid and n-butanol where the ester product is trapped and the butanol, immiscible with the ester flows back into the reactor. Esterification is the general name for a Chemical reaction in which two reactants (typically an alcohol and an acid form an Ester as the reaction product Benzoic acid, C7H6O2 (or C6H5COOH is a colorless crystalline solid and the simplest Aromatic Carboxylic acid Butanol or butyl alcohol (sometimes also called biobutanol when produced biologically is a Primary alcohol with a 4 Carbon structure and the Molecular Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least Removing water in the course of these esterfications shifts the chemical equilibrium in favour of ester formation. In a Chemical process, chemical equilibrium is the state in which the chemical activities or Concentrations of the reactants and products have no net change
External links
- Esterification of benzoic acid and n-butanol
- Supplier Schematics
- Esterfication of acetic acid with butanol
References
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