Liquid-Phase Oxidation Reaction and Mechanism of p-Diethylbenzene to p-Ethylacetophenone with H2O2 in a Batch Reactor and a Fixed Bed Reactor

Liquid-phase oxidation of p-diethylbenzene (PDEB) to p-ethyl-acetophenone (EAP) with hydrogen peroxide (H2O2) catalyzed by 5Co/SBA-15 in a batch reactor and a fixed bed reactor was investigated. Based on the analysis of compositions, a reasonable reaction mechanism was discussed. Results show whether in a batch reactor or a fixed bed reactor, a mixture of EAP, 1-(4-ethylphenyl)-1-ethanol (EPEA), p-diacetylbenzene (PDAB), 4-acetylbenzoic acid (AA) and terephthalic acid (TA) could be detected. The reaction mechanism for oxidation of PDEB based on two reaction pathways for oxidizing ethyl group with H2O2 involving radical intermediates are proposed, PDEB firstly undergoes oxidation to give alkyl benzene carbocation and generates the key intermediate EPEA, which will be converted to EAP through pathway I. EAP can ultimately yield byproducts PDAB, AA and TA with pathway I and pathway II. Besides, diethyl group of PDEB can be tolerated pathway II to generate TA directly. The selectivity of EAP is steady around 68% in the fixed bed reactor, which is 16.52% higher than that in the batch reactor. It is essential to have a further study on the continuous flow process and obtain more data for industrial application.