Acid-catalysed dehydration of alcohols in supercritical water

✍ Scribed by Sundaresh Ramayya; Andrew Brittain; Carlos DeAlmeida; William Mok; Michael Jerry Antal Jr

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 958 KB
• Volume: 66
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(87)90183-9

✦ Synopsis

At pressures exceeding its critical pressure water retains its ionic properties to temperatures of 400°C or more. In water under these conditions trace amounts of Arrhenius acids dissociate and selectively catalyse the dehydration of alcohols, diols, and polyols. High yields of the desired dehydration product (ethene from ethanol, propene from propanol, acetaldehyde from ethylene glycol, and acrolein from glycerol) can be obtained with a residence time of less than one minute. However, for ethanol the equilibrium conversion appears to be less than predicted by ideal solution thermochemical calculations. This may be due to catalyst deactivation, or it may be an effect of hydrogen bonding between the water and the reactant alcohol. The dehydration of n-propanol proceeds by a first order reversible reaction whose equilibrium is close to that predicted by thermodynamics. Because these dehydration reactions proceed rapidly with a high degree of specificity, they appear to be good candidates for industrial exploitation.