Experimental Measurement of the Rate of Methyl tert-Butyl Ether Hydrolysis in Sub- and Supercritical Water

Experiments were conducted to measure the isothermal rate of methyl tert -butyl ether (MTBE) decomposition in water at hydrothermal conditions ( T = 150−600 °C and P = 250 bar). The primary identified products of the reaction of MTBE were methanol, isobutene, and tert -butyl alcohol. An assumed first-order rate constant for the hydrolysis of MTBE was determined at each temperature and showed a local maximum below the critical temperature of water (374 °C) followed by a local minimum above it. This behavior was modeled using an acid-catalyzed mechanism, which resulted in a rate expression with a first-order dependence on the concentration of H + . Because of the dramatic decrease in the ion dissociation constant of water ( K w ) in the critical region, the drop in the rate of reaction could be modeled quantitatively over the entire temperature range.