ABSTRACT A kinetic model of ethylbenzene oxidation by air oxygen in the presence of 2‐ethylhexanoates of metals of the second and 12th groups (Mg, Ca, Sr, Ba, Zn, and Cd) as catalysts was constructed and parameterized using experimental data. Using the model, it is shown that: (1) in the range of 1–100 mmol/L, there exist initial concentrations of catalysts below which an increase in the initial catalyst concentration leads to an increase in the rate of ethylbenzene hydroperoxide formation in the oxidation of ethylbenzene (428 K, 1 atm, volume flow rate of air supply to the reactor of 0.018 m 3 /h, initial ethylbenzene concentration of 8.17 mol/L, initial concentrations of other species are 0), and above which it leads to a decrease (2‐ethylhexanoates of Mg, Ca, and Zn) or a plateau (2‐ethylhexanoates of Sr, Ba, and Cd); this is because the catalysts simultaneously accelerate the reactions of both formation and decomposition of ethylbenzene hydroperoxide, and starting from a certain initial catalyst concentration, the decomposition of ethylbenzene hydroperoxide begins to prevail over its formation; (2) the key reaction for the formation of ethylbenzene hydroperoxide and for ethylbenzene conversion in catalytic ethylbenzene oxidation, as in the non‐catalytic process, is the reaction between ethylbenzene and the peroxyl radical of ethylbenzene; the key reactions governing selectivity are the formation of methylphenylcarbinol and acetophenone from oxyl and peroxyl radicals of ethylbenzene; the role of the catalyst is to increase the concentrations of these radicals through the decomposition reactions of the intermediate adduct “ethylbenzene hydroperoxide + catalyst”; (3) Mg, Ca, Sr, Cd 2‐ethylhexanoates deactivate within 1 h of the ethylbenzene oxidation process, while Ba and Zn 2‐ethylhexanoates deactivate within 4 h (428 K, 1 atm, volume flow rate of air supply to the reactor of 0.018 m 3 /h, initial ethylbenzene, ethylbenzene hydroperoxide, and catalyst concentrations of 8.163, 0.022, and 5 mmol/L, respectively, initial concentrations of other species are 0); therefore, these catalysts should not affect the subsequent transformations of ethylbenzene hydroperoxide during propylene epoxidation in the Halcon process.
Ulitin et al. (Tue,) studied this question.