Preparation of concentrated *ao acid
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I would like to ask whether it is possible to concentrate a 25% dilute *ao acid to 68% using vacuum distillation. Is the concentration of the distillate at the beginning of the distillation process higher or lower than 25%, and how does the concentration of the distillate change during the distillation process? Will an azeotropic distillation be formed in the end?
Concentrated *ao acid cannot be obtained by directly distilling dilute *ao acid, as *ao acid and water form a binary azeotrope. A dehydrating agent such as sulfuric acid must be added in order to carry out distillation.
So if I directly distill a 20% *AO acid solution, will the concentration of *AO acid in the first fraction be greater than 20% if I collect the fractions separately? Does the concentration of *AO acid increase or decrease in the subsequent fractions?
The boiling points of the two components are similar, so direct distillation results in an azeotrope, which prevents concentration; you can give it a try in the laboratory to see for yourself
Thank you. With a concentration of 20% now, will azeotropy occur during the distillation of dilute *ao acid from the very beginning? Should we first evaporate some of the water, waiting until the concentration at the bottom of the tank reaches 68% before boiling point elevation occurs?
Low-concentration distillation involves evaporating a portion of the water first, but the resulting water is not pure; it is acidic, and the laboratory is unable to control the process of concentration change.