“槽内式”间接电氧化法制备2-甲基-1,4-萘醌

以Ti/PbO2为阳极、Pb为阴极、硫酸为支持电解质,采用Cr6+/Cr3+为氧化媒质,四丁基溴化铵为相转移剂,在阳离子交换膜为隔膜的“板框式”电解槽中,进行“槽内式”间接电氧化2-甲基萘(2-MN)合成2-甲基-1,4-萘醌(2-MNQ)的研究。考察了2-MN间接电氧化制备2-MNQ的工艺条件对2-MNQ选择性和电流效率的影响规律。实验结果表明:在2-MN和Cr2O72-浓度分别为0.02 mol/L和0.03 mol/L,硫酸质量分数20%,温度50℃,电流密度110 A/m2,通电量为理论通电量0.2倍的工艺条件下进行电解,2-MNQ的平均选择性为71.9%,平均表观电流效率为69.7%。

Preparation of 2-Methyl-1,4-naphthoquinone by "In-cell" Indirect Electrooxidation

2-Methyl-1,4-naphthoquinone(2-MNQ) was prepared from 2-methylnaphthalene(2-MN) by "in-cell" indirect electrolytic oxidation,using cation-exchange membrane as diaphragm,Ti/PbO2 as anode,Pb as cathode,sulfuric acid as supporting electrolyte,Cr6+/Cr3+ as oxidative medium and tetrabutylammonium bromide as phase transfer agent.The process conditions for synthesizing 2-MNQ were optimized in the plate and frame electrolytic cell.Under the optimum conditions that c(2-MN)=0.02 mol/L,c(Cr2O72-)=0.03 mol/L,w(H2SO4)=20%,reaction temperature=50 ℃,current density=110 A/m2 and the electric quantity was 0.20 times the theoretical value,the mean selectivity for 2-MNQ was 71.9%,and the mean apparent current efficiency was 69.7%.