Assessment of a Stirred-Cell Reactor Operated Semicontinuously for the Kinetic Study of Fast Direct Ozonation Reactions by Reactive Absorption

Abstract

A jacketed stirred-cell reactor, operated semi-continuously, was used to assess the kinetics of fast ozonation reactions by reactive absorption. The method was applied to the direct ozone reaction with resorcinol. A high resorcinol concentration was used to reach a steady state and to neglect the byproducts accumulation. Thus, the mass-transfer rate, and consecutively the reaction rate, were deduced from the ozone mass balance in the gas phase. The gas-phase and liquid-phase mass-transfer coefficients were previously measured directly through the ozone absorption in appropriated conditions. The results emphasized the high sensitivity of the reaction rate constant to the ozone physicochemical properties, especially its solubility, which is controversial in the literature. Therefore, several correlations used to calculate the ozone solubility in water were considered to calculate the second-order reaction rate constant, which varied from 3.57-4.68 10 5 L mol -1 s -1 at 20°C to 9.50-12.2 10 5 L mol -1 s -1 at 35°C. The activation energy was in the range 35-59 kJ mol -1 depending on the considered ozone solubility correlation. A sensitivity analysis is provided to assess the influence of the experimental conditions and ozone physicochemical properties on the model. Finally, the applicability of this method is thoroughly discussed.2

Determination by reactive absorption of the rate constant of the ozone reaction with the hydroperoxide anion

“…This method is particularly adapted to reactions with molecular ozone since the dissolved ozone concentration is zero (Dang et al, 2016). Thus, the accuracy of the method is not affected by the poor ozone solubility and stability and its rather inaccurate quantification (Beltrán, 2004;Beltrán et al, 1998;Cardona et al, 2010;Dang et al, 2016;Sotelo et al, 1990;Sotelo et al, 1991).…”

“…Thus, the accuracy of the method is not affected by the poor ozone solubility and stability and its rather inaccurate quantification (Beltrán, 2004;Beltrán et al, 1998;Cardona et al, 2010;Dang et al, 2016;Sotelo et al, 1990;Sotelo et al, 1991). The calculation of the enhancement (or reaction) factor E, deduced from both the mass-transfer and chemical reaction rates, is the basis of the method (Beltrán, 2004).…”

“…The calculation of the enhancement (or reaction) factor E, deduced from both the mass-transfer and chemical reaction rates, is the basis of the method (Beltrán, 2004). Stirred-cell reactors, in which the interfacial area is well known from the reactor geometry, are particularly appealing for ozonation studies (Dang et al, 2016). Nonetheless, the gas-side resistance might be significant, even using a poorly soluble compound such as O3, especially when a fast chemical reaction is involved in the liquid phase (Dang et al, 2016).…”

“…Stirred-cell reactors, in which the interfacial area is well known from the reactor geometry, are particularly appealing for ozonation studies (Dang et al, 2016). Nonetheless, the gas-side resistance might be significant, even using a poorly soluble compound such as O3, especially when a fast chemical reaction is involved in the liquid phase (Dang et al, 2016). To reduce the number of inputs of the model and to gain in accuracy, the pseudo-first order regime is recommended (Dang et al, 2016).…”

“…Nonetheless, the gas-side resistance might be significant, even using a poorly soluble compound such as O3, especially when a fast chemical reaction is involved in the liquid phase (Dang et al, 2016). To reduce the number of inputs of the model and to gain in accuracy, the pseudo-first order regime is recommended (Dang et al, 2016). In that case, the reactant concentration near the gas-liquid interface is equal to the bulk concentration (Beltrán, 2004;Bin and Roustan, 2000;Luzi et al, 2014;Vaidya and Kenig, 2007).…”