Refers toWater moleculeThe reaction process of precipitation.But it usually does not includehydrationThe process of removing water molecules from crystals or other hydrates.Dehydration can be performed by heating orcatalyzerIt can also be carried out under the action ofDehydrating agentReaction;It can occur within a compound molecule, that is, intramolecular dehydration, or between two molecules of the same compound, that isIntermolecular dehydration。
Dehydration reaction isHydration reactionThe reverse process of, usuallyEndothermic reaction, Generalhigh temperatureLow pressure is conducive to reaction.Therefore, in industry, this process is carried out at a higher temperature than the corresponding reverse process, namely hydration.In addition, most dehydration processes mustcatalyzerExists.Catalyst used in hydration processacid catalyst It is also suitable for dehydration. The commonly used ones are sulfuric acidphosphoric acid、Aluminium trioxideEtc.The main dehydration processes for industrial production include:
② Dehydration of acid The dehydration of monocarboxylic acid can produce anhydrides, but it is not usually used as a method of producing anhydrides.acetic acidGenerated by dehydration after heating to 700~750 ° CKeteneIt is the main method of making ketene.Dicarboxylic acidCan be formed at lower temperature after heatingAcid anhydride, e.g. byMaleic acidDehydration systemMaleic anhydride。nitric acidIt can be used on dehydrated basis (usually PtwoOfive）Generated in the presence ofNitrogen pentoxide（N2O5）。
In 1809, P. Bligh proposed thatethanolDehydration can be madeEtherThis reaction is still the basis of ether production method.the First World Warperiod,GermanyBitfieldThe first electrochemical plant to use ethanol dehydration to produce ethylene;1929, GermanyIG Farben Developed byFormamideDehydration systemHydrocyanic acidMethod.
