Study On The Clean Process Of 2-Methyl-1,4-Naphthalene Quinone By 2-Methylnaphthalene Oxidation Synthesis

2-menadione（2-MNQ）is an important intermediate of K vitamins,which is widely used in medicine,pesticides,feed additives and other fields.Vitamins K₃ and K₄ can only be obtained artificially.In industry,2-methylnaphthalene（2-MN）and chromic anhydride are often used as raw material and oxidant,respectively.This process produces a large amount of waste containing chromium,which poses a certain threat to the environment and human health.Therefore,scholars all over the world are competing to develop a new green synthesis process with high yield,low cost,safety and effectiveness.In this thesis,H₂O₂ was used as oxidant to prepare 2-MNQ green oxidation process,and the synthesis process was optimized.The main research results are as follows:Using 2-methylnaphthalene（2-MN）as raw material,（NH₄）₂S₂O₈ as initiator,ferrous sulfate as catalyst,2-methyl-1,4-naphthoquinone（2-MNQ）was synthesized by 30%H₂O₂ batch oxidation method in glacial acetic acid system.The effects of catalyst,reaction temperature,reaction time,dosage of oxidizer and initiator on 2-MNQ were investigated.HPLC（external standard method）was used to determine the conversion and yield of 2-MNQ,and the appropriate technological conditions were obtained:n（H₂O₂）:n（2-MN）=10:1,the mass fraction of（NH₄）₂S₂O₈ is 4%,the reaction temperature is 85℃,the reaction time is 5h,under this condition,the conversion of 2-methylnaphthalene is 75%,the product yield is 28%.Using 2-methylnaphthalene（2-MN）as raw material,（NH₄）₂S₂O₈ as initiator,peracetic acid was prepared with 30%H₂O₂and glacial acetic acid under the catalysis of sulfuric acid,and then dropped into the reaction solution,2-methyl-1,4-naphthoquinone（2-MNQ）was oxidized and synthesized.Its structure was characterized by ICIR,GC-MS and LCMS.The oxidation reaction mechanism and intermediate products were verified.The effects of reaction temperature,reaction time,dosage of oxidant and dripping time on the yield and conversion of 2-MNQ were investigated,and the appropriate process conditions were obtained:The reaction temperature was 65℃,the reaction time was 5h,n（H₂O₂）:n（2-MN）=26:1,and the dripping time was 1.5h.Under this condition,the conversion rate of 2-methylnaphthalene was 98%and the product yield was 35%.The process has the characteristics of environmental protection,simple process,mild operating conditions and easy access to raw materials.At present,the synthesis process of 2-MNQ from 2-MN is mainly intermittent reaction with low reaction efficiency,while the microchannel reactor can accurately control the ratio of reaction materials and reaction time,and effectively control the reaction temperature.Therefore,this paper explored the synthesis process of 2-MNQ from 2-methylnaphthalene（2-MN）in a microchannel reactor,and investigated the effects of different material ratios,reaction temperature and reaction time on the yield and conversion of 2-methyl-1,4-naphthalene quinone.The optimum process conditions were obtained as follows:reaction temperature was 75℃,reaction time was 3h,n（H₂O₂）:n（2-MN）=26:1.At this time,the conversion rate of 2-methylnaphthalene was 99%,and the product yield was 42%.