Liquid-phase oxidation of 2-methoxy-p-cresol to vanillin with oxygen catalyzed by a combination of CoCl2 and N-hydroxyphthalimide
Liquid-phase oxidation of 2-methoxy-p-cresol to vanillin (4-hydroxy-3-methoxybenzaldehyde), in methanol, with molecular oxygen at atmospheric pressure as oxidant and a combination of cobaltous chloride and N-hydroxyphthalimide (NHPI) as catalyst, has been investigated. The effect of reaction conditions on conversion and selectivity for vanillin was studied systematically. Selectivity for vanillin could be enhanced by optimizing the molar ratio of 2-methoxy-p-cresol to NHPI, the amount of sodium hydroxide, reaction time, reaction temperature, and the volume of methanol, which determined the concentration of the reactants. Under the optimized conditions the yield of vanillin was 90.1 %.
Keywords2-Methoxy-p-cresol Vanillin Oxidation Molecular oxygen Cobaltous chloride N-hydroxyphthalimide
The authors are grateful for financial support from the National Natural Science Foundation of China (no. 21276061).
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