Modeling the Dehydration of tert-Butyl Alcohol and Avoidance of the Formation of Oligomers

Abstract

To model the industrial relevant dehydration process of tert-butyl alcohol in sulfuric acid, a new mechanistic reaction scheme is applied that accounts for a parallel reaction path via di-tert-butyl ether (DTBE). Based on the quasi-steady-state approximation concerning intermediates, a mathematical model is developed that incorporates the acidity of the solvent. Model validation is performed by means of experimental data obtained from stationary continuously stirred tank reactor (CSTR) measurements at different temperatures under reaction conditions that exclude the formation of oligomers. It is shown how numerical simulations, combining this mathematical model with experimental correlations, allow for maximization of isobutene yield in a batch reactor in the regime where the formation of oligomers is avoided.

Mechanistic Insights into the Rhenium‐Catalyzed Alcohol‐To‐Olefin Dehydration Reaction

“…The main difference, however, lies in the p K a of the hydroxyrhenium species, which is expected to be lower than that of the strong Brønsted acids usually applied in dehydration reactions, thereby making the deprotonation step of the carbenium ion more plausible. We, however, did not calculate the ether formation step here, which is proposed to be a relevant pathway in the Brønsted acid‐catalyzed reaction,19, 20 and therefore we do not rule out the involvement of such a pathway in the rhenium‐catalyzed reaction.…”

“…One of the issues involved with a pure E1 mechanism is the deprotonation of the carbenium ion, which in acidic media is very slow. Several kinetic investigations have indicated that the formation of ethers through an Ad E 2 mechanism and subsequent ether‐splitting could provide an alternative pathway 19. 20 For the hydrochloric acid‐catalyzed gas phase dehydration, a concerted six‐membered transition‐state has been proposed on the basis of DFT calculations, with the HCl proton linked to the OH group and the chloride linked to the hydrogen atom at the β‐position 21.…”