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Relative volatility is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes. [ 1 ] [ 2 ] [ 3 ] In effect, it indicates the ease or difficulty of using distillation to separate the more volatile components from the less ...
In chemistry, volatility is a material quality which describes how readily a substance vaporizes. At a given temperature and pressure , a substance with high volatility is more likely to exist as a vapour , while a substance with low volatility is more likely to be a liquid or solid .
Distillation can operate over a wide range of pressures from 0.14 bar (e.g., ethylbenzene/styrene) to nearly 21 bar (e.g.,propylene/propane) and is capable of separating feeds with high volumetric flowrates and various components that cover a range of relative volatilities from only 1.17 (o-xylene/m-xylene) to 81.2 (water/ethylene glycol). [2]
Large-scale industrial distillation is rarely undertaken if the relative volatility is less than 1.05 with the volatile component being i and the less volatile component being j. [2] K values are widely used in the design calculations of continuous distillation columns for distilling multicomponent mixtures.
Unstable node: This is the pure component or the azeotropic point with the lowest boiling temperature and highest vapor pressure in a distillation region. Residue curve never reach an unstable node. Saddle: These are pure components or azeotropic points with an intermediate boiling temperature and vapor pressure in a distillation region.
Greater deviations from Raoult's law make it easier to achieve significant changes in relative volatility with the addition of another component. In azeotropic distillation the volatility of the added component is the same as the mixture, and a new azeotrope is formed with one or more of the components based on differences in polarity. [2]
Salt-effect distillation is a method of extractive distillation in which a salt is dissolved in the mixture of liquids to be distilled. The salt acts as a separating agent by raising the relative volatility of the mixture and by breaking any azeotropes that may otherwise form.
Batch heteroazeotropic distillation is an efficient method for the separation of azeotropic and low relative volatility (low α) mixtures. A third component (entrainer, E) is added to the binary A-B mixture, which makes the separation of A and B possible.