Homogeneous Catalysts of Redox Processes Based on Heteropolyacid Solutions III: Developing Effective Ways for the Preparation of 2,3,5-Trimethyl-1,4-Benzoquinone

Different ways of preparing 2,3,5-trimethyl-1,4-benzoquinone (TMQ), a key intermediate in the synthesis of vitamin E, via the catalytic oxidation of 2,3,6-trimethylphenol (TMP) are considered. It is shown that aqueous solutions of Mo-V phosphoric heteropolyacids (HPAs) are promising catalysts for the oxidation of TMP with oxygen. Different technological options are analyzed for using HPAs in this reaction: the one-stage homogeneous acetic acid oxidation of TMP and a biphasic two-step procedure. The efficiency of a biphasic version that ensures high (up to 99.5%) selectivity for TMQ and high catalyst productivity in the target reaction (approximate to 600-800 g TMQ L-cat(-1) h(-1)) is proved.