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以空气为氧源,一系列卤代异羟肟酸钴(Ⅱ)配合物(CoL21～CoL29)为催化剂,研究了其液相氧化对二甲苯生成对甲苯甲酸的性能和规律,比较了配合物中引入卤原子的种类与位置对催化剂催化活性的影响,考察了氯代异羟肟酸钴(Ⅱ)配合物CoL23催化氧化不同配比的混合二甲苯的选择性.结果表明:在反应温度为110℃、催化剂浓度为1.0 mmol/L、空气流速为2.4 L/L/min的条件下,1.5 h内二氯代异羟肟酸配体的钴(Ⅱ)配合物的催化活性顺序是CoL23>CoL24>CoL27>CoL25>CoL26,1.5～4 h的催化活性顺序是CoL23>CoL27>CoL24>CoL25>CoL26.单卤代异羟肟酸配体的钴(Ⅱ)配合物催化活性顺序是CoL29>CoL22、CoL28>CoL21.当混合二甲苯中各异构体比例为5∶3∶2(对∶邻∶间)时,反应有较高的选择性,并能析出纯度达96.7%的对甲苯甲酸固体.
Using air as oxygen source, a series of Co (Ⅱ) complexes (CoL21 ~ CoL29) were used as catalysts to study the performance and the regularity of liquid phase oxidation of p-xylene to p-toluate. The effect of the type and position of the halogen atom on the catalytic activity of the catalyst was investigated. The selectivity of mixed xylenes with different molar ratios of cobalt hydroxohydroxyl cobalt (Ⅱ) complex CoL23 was investigated. The results showed that when the reaction temperature was The catalytic activity of cobalt (Ⅱ) complexes with dichlorohydroxamic acid ligands within 1.5 h at 110 ℃, catalyst concentration of 1.0 mmol / L and air velocity of 2.4 L / L / min was CoL23> CoL24> CoL27> CoL25> CoL26, and the order of catalytic activity for 1.5-4 h was CoL23> CoL27> CoL24> CoL25> CoL26. The catalytic activity of the cobalt (II) complex of monohalohydroxamic acid ligand was CoL29> CoL22 , CoL28> CoL21. When the ratio of isomers in mixed xylene is 5: 3: 2 (between: o: m), the reaction has higher selectivity and can precipitate p-toluate with a purity of 96.7% .