Premium
Kinetics and mechanism of isobutene formation from T ‐butanol in hot liquid water
Author(s) -
Xu Xiaodong,
Antal Michael J.
Publication year - 1994
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690400911
Subject(s) - chemistry , butanol , carbocation , dehydration , protonation , arrhenius equation , catalysis , kinetics , acid catalysis , organic chemistry , ether , reaction mechanism , dehydration reaction , supercritical fluid , activation energy , ethanol , ion , biochemistry , physics , quantum mechanics
Isobutene is the only product of the uncatalyzed and acid‐catalyzed dehydration of tert‐butanol in compressed liquid water at 250°C. The uncatalyzed dehydration reaction is fast: equilibrium is established after about 30 s. Only one of many chemically‐motivated kinetic models is able to fit all the experimental data. This model presumes a heterolytic dehydration mechanism that involves protonated alcohol, carbocation, di‐tert‐butyl ether, and protonated ether as intermediates. The model permits tert‐butanol to dissociate as both an Arrhenius acid and a Bronsted acid while catalyzing its dehydration to isobutene. The pK a of tert‐butanol at 250°C is predicted to be about 9, whereas its value at normal temperature and pressure is 18. This 10 9 increase in the K a value of tert‐butanol hints of the promising new world of reaction chemistry in near‐ and supercritical water.