(762f) Optimizing the Liquid Phase Oxidation of Ethylbenzene to Hydroperoxide by Varying Temperature Operation

The liquid phase oxidation of ethylbenzene (EB) to hydroperoxide (EBHP) by air is the fundamental step of the co-production technology of propylene oxide and styrene monomer (PO/SM). Two major problems in industrial manufacture of EBHP are the slow reaction rate at lower temperatures and the unacceptable selectivity at higher temperatures. In this work, the liquid phase oxidation kinetics of EB to EBHP was firstly measured under temperatures range from 135 to 155 ℃ in a semi-continuous pilot plant, in which the air was bubbled continuously but the EB was introduced before each experiment. Based on the free radical chain reaction mechanism, elementary reaction steps of liquid phase oxidation of EB were put forward. The kinetic model was then established, including EBHP and two major byproducts in EB oxidation, i.e. acetophenone (ACP) and α-methylbenzyl alcohol (MBA). The model calculation was in good agreement with experimental data. Next, the decreasing temperature operation step by step (DTOSS) for EB oxidation was simulated and the results showed that DTOSS can lead to a higher yield of EBHP meanwhile the reaction rate is faster than that at constant lower temperatures. This simulation results were also verified by experiments carried out under varying temperature operation. The optimized temperature sequence is as follows: 150 ℃ for 1.5 hours, followed by 145 ℃ for 0.5 hours, followed by 140 ℃ for 1 hour, and finally followed by 135 ℃ for 1 hour. According to this temperature sequence, after 4 hours the conversion of EB reached 10%, and the selectivity of EBHP was 87.2%.