疏水性Cosalen/SBA-15的制备及在甲苯选择性氧化中的应用

Preparation of Hydrophobic Cosalen /SBA-15 and Its Application in the Selective Oxidation of Toluene

以介孔分子筛SBA-15为载体,先采用γ-氨丙基三乙氧基硅烷(APTES)进行氨基硅烷化修饰,然后经甲基三乙氧基硅烷(MTES)疏水修饰后固载双水杨醛缩乙二胺合钴配合物(Cosalen).采用傅里叶变换红外光谱、紫外-可见漫反射光谱、X射线光电子能谱、元素分析、等离子体发射光谱、X射线衍射和氮气物理吸附等手段对制备的固载型催化剂Cosalen/SBA-15进行了物相结构和修饰程度的表征,并考察了样品对甲苯、苯甲醛和苯甲醇的吸附性能及在甲苯液相氧化反应中的催化性能.结果表明,固载型催化剂Cosalen/SBA-15的介孔结构和孔道有序性保持良好,Cosalen通过与氨基配位固载在修饰后的载体SBA-15上,且高度分散,氨基硅烷化和甲基修饰明显增强了其表面疏水性能,对苯甲醛和苯甲醇的吸附量降低.疏水性Cosalen/SBA-15协同N-羟基邻苯二甲酰亚胺(NHPI)催化甲苯液相分子氧氧化反应,无溶剂体系在130℃下反应2 h,甲苯转化率达到16.0%,产物中苯甲醛和苯甲醇的总选择性为32.0%,在一定程度上抑制了极性产物深度氧化为苯甲酸.高温不利于苯甲醛和苯甲醇选择性的提高,降低温度至110℃,甲苯转化率达到12.9%时,苯甲醛和苯甲醇的总选择性提高到43.9%.

The mesoporous SBA-15 was functionalized by(3-aminopropyl)-triethoxysilane(APTES),and then hydrophobic modified with methyltriethoxysilane(MTES). The obtained material was used as carrier to immobilize N,N-bis( salicylidene) ethylenediiminocobalt( Cosalen) complex. The supported catalyst Cosalen / SBA-15 was characterized by means of Fourier transform infrared spectroscopy,diffuse reflectance ultroviolet visible spectroscopy,X-ray photoelectron spectrograph,elementary analysis,inductive coupled high frequency plasma,X-ray diffraction,N2adsorption-desorption techniques. The adsorption properties of samples for toluene,benzaldehyde and benzyl alcohol and catalytic performance for liquid-phase oxidation of toluene were investigated. The results showed that the ordered mesoporous structure of SBA-15 carrier after modification were retained; Cosalen was highly dispersed on the surface of SBA-15 by the coordination effect of NH2ligand. The hydrophobicity of samples with amino functionalization and methyl modification was obviously enhanced,and their adsorptive capacity for benzaldehyde and benzyl alcohol decreased. The liquid-phase solvent-free oxidation of toluene with molecular oxygen catalyzed by hydrophobic Cosalen / SBA-15 and NHPI effectively improves the products selectivity of benzaldehyde and benzyl alcohol to 32. 0% with the conversion of toluene 16. 0% at 130 ℃ for 2 h,which resulted from the prevention of deep oxidation of benzaldehyde and benzyl alcohol to benzonic acid to some extend. The investigation of temperature effect showed that high temperature was not good for the improvement of selectivity of benzaldehyde and benzyl alcohol. Lower temperature to 110 ℃,the selectivity of benzaldehyde and benzyl alcohol was up to 43. 9% with the conversion of toluene 12. 9%.