钴基吡唑配合物催化氧化甲苯制苯甲酸

Oxidation of Toluene over Cobalt-Pyrazole Complexes

采用氯化钴、澳化钴与吡唑类化合物反应制备不同钴基吡唑配合物([Co(dmBPM)X_2](dmBPM =N,N′-二(3,5-二甲基吡唑)甲烷,X=Cl,Br)、[Co(H_2Cbpz)_2X_2]·2H_2O(H_2Cbpz=N,N′-二吡唑甲烷, X=Cl,Br)、[CoX_2(pz)_4](pz=吡唑,X=Cl,Br)、[CoX_2(dmpz)_2](dmpz=3,5-二甲基吡唑,X=Cl,Br)),并利用核磁共振(NMR)、红外光谱(FT-IR)和元素分析(EA)对合成的配合物进行了表征。以乙酸为溶剂,考察乙酸钴和钴基吡唑配合物在甲苯氧气液相氧化反应中的催化性能及反应条件对催化性能的影响。结果表明,N,N′-二(3,5-二甲基吡唑)澳化钴(Ⅱ)的催化性能最好,其合适的反应条件为催化剂与甲苯物质的量之比1:300,乙酸与甲苯质量比1.2、反应压力1.5 MPa和反应温度150℃,在该条件下反应140 min后,甲苯转化率和苯甲酸选择性分别为89.05%和92.35%。

Eight cobalt-pyrazole complexes were prepared from pyrazole and cobaltous chloride or cobaltous bromide （[CoX2 （dmBPM）] （ dmBPM = N, N＇-bis （ 3, 5-dimethylpyrazolyl） methane, X=Cl, Br）, [Co（H2Cbpz）2X2] · 2H2O（H2Cbpz= N, N＇-bis（1-pyrazolyl） methane, X=Cl, Br）, [CoX2（pz）4]（pz=-pyrazole, X=Cl, Br） and [CoX2（dmpz）2]（dmpz=3,5-dimethylpyrazole, X=Cl, Br））. The complexes were characterized by nuclear magnetic resonance （NMR）, Fourier transformation infrared spectroscopy （FT-IR） and element analyzer （EA）. The activities of cobalt acetate and the complexes were evaluated by liquid-phase oxidation of toluene with oxygen as oxidant. The results showed that the acitivity of N, N＇-bis（3,5-dimethylpyrazole） cobalt （Ⅱ） bromide was the highest. The effects of reaction temperature, reaction pressure, catalyst dosage and reaction time on liquid-phase oxidation of toluene were investigated. The conversion of toluene was 89.05% and the selectivity of benzoic acid was 92. 35% under the optimal conditions of molar ratio of catalyst to toluene 1 ： 300, mass ratio of acetic acid to toluene 1.2, reaction temperature 150℃, oxygen pressure 1.5 MPa and reaction time 140 min.