钴-溴催化氧化邻二甲苯制邻甲基苯甲酸

Catalytic Oxidation of oXylene to oToluic Acid with Cobalt Naphthenate and Ammonium Bromide as Catalyst

研究了邻二甲苯空气液相氧化制邻甲基苯甲酸，采用环烷酸钴单独催化和环烷酸钴与溴化铵共同催化对邻甲基苯甲酸收率的影响．用环烷酸钴单独催化时，在低Ｃｏ２＋浓度范围内（小于３．４×１０－３ｍｏｌ／Ｌ），随环烷酸钴浓度升高，邻甲基苯甲酸收率增加，但Ｃｏ２＋浓度达到２．２４×１０－３ｍｏｌ／Ｌ后，邻甲基苯甲酸收率基本不变．向环烷酸钴催化的反应溶液中添加溴化铵后，邻甲基苯甲酸收率增加，但只有在Ｂｒ－与Ｃｏ２＋的物质的量比为１．０∶１．０时，邻甲基苯甲酸的收率才最大．环烷酸钴和溴化铵之间存在协同催化作用，这种协同催化作用是通过环烷酸钴和溴化铵形成的络合物来完成的。

The liquidphase oxidation of oxylene with air to produce otoluic acid was investigated in two catalyst systems of cobalt naphthenate and the combination of cobalt naphthenate with ammonium bromide. With cobalt naphthenate alone as catalyst, the yield of otoluic acid increases as the content of cobalt naphthenate in the reaction mixture is increased in low Co2+ concentrations of less than 3.4103 mol/L. However, the otoluic acid yield remains virtually unchanged with Co2+ concentration after the concentration reaches 2.24103 mol/L. The otoluic acid yield increases as ammonium bromide is added to the reaction mixture containing cobalt naphthenate. However, the otoluic acid yield reaches the maximum only at a molar ratio of cobalt to bromine of 1.01.0. This suggests that a synergistic catalysis of cobalt naphthenate and ammonium bromide exists in the reaction. This synergistic catalysis takes place through a complex of cobalt naphthenate and ammomium bromide. The complex, which has a 1.01.0 molar ratio of cobalt to bromine, accelerates the initiation of radicals in the oxidation.