Al2O3固载Schiff碱锰配合物催化氧化环己烷反应

Catalytic Oxidation of Cyclohexane with Alumina-Supported Schiff Base Manganese Complexes

以Al2O3为载体制备了Al2O3固载Schiff碱锰配合物,并利用傅里叶变换红外光谱、紫外-可见分光光度计和X射线光电子能谱进行了表征。以该配合物为催化剂,考察了配体结构、催化剂用量、氧气压力和反应温度对环己烷氧化反应的影响。结果表明,Al2O3固载不仅提高了Schiff碱锰配合物催化剂的稳定性且易与产物分离;随配体环内空腔的增大,催化剂的活性降低,其中Al2O3固载的乙二胺-水杨醛Schiff碱锰配合物([Mn(Salen)(1)]-Al2O3)的活性最高。环己烷氧化反应的最佳条件为:[Mn(Salen)(1)]-Al2O3摩尔分数0.30%,氧气压力1.4MPa,反应温度140℃,反应时间4h。在此条件下,环己烷的转化率为10.8%,KA油(环己醇与环己酮的混合物)的选择性为84.2%,催化剂每个活性中心上平均转化环己烷的分子数达到3600。

Alumina-supported Schiff base manganese complexes were synthesized by reaction of Schiff base manganese complexes with alumina, and were characterized by means of IR, UV-Vis and XPS. The supported complexes were used as catalysts in oxidation of cyclohexane. Effects of Schiff base manganese complex structure, catalyst dosage, oxygen pressure and reaction temperature on oxidation of cyclohexane were studied. The supported catalysts are better in stability than the unsupported because they can be easily separated from products and can be reused after purifying and drying. The catalytic activity decreases with the increase of cavity within complex molecules. N,N＇-bis （salicylic aldehyde ） ethylenediamine Schiff base manganese complexes supported on Al2O3 （[Mn（Salen）（1）]-Al2O3 ） is the best in catalytic activity. Under the optimal conditions for cyclohexane oxidation： [ Mn （ Salen ） （ 1 ） ]-A12O3 mole fraction 0.30% , oxygen pressure 1.4 MPa, reaction temperature 140 ℃ and reaction time 4 h, conversion of cyclohexane and selectivity to KA oil （mixture of cyclohexanol and cycohexanone）are 10.8% and 84.2% respectively, and number of average molecules of cyclohexane converted per each active center on catalyst is 3 600.