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

Abstract

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 (≈600–800 g TMQ \({\text{L}}_{{{\text{cat}}}}^{{ - 1}}\) h⁻¹) is proved.