Abstract:

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, N₂ adsorption-desorption techniques. The adsorption properties of samples for toluene, benzaldehyde and benzyl alcohol and catalytic performance for liquid-phase oxidation of to-luene were investigated. The results showed that the ordered mesoporous structure of SBA-15 carrier after mo-dification were retained; Cosalen was highly dispersed on the surface of SBA-15 by the coordination effect of NH₂ ligand. 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 tempe-rature to 110 ℃, the selectivity of benzaldehyde and benzyl alcohol was up to 43.9% with the conversion of toluene 12.9%.

Key words: N,N-Bis(salicylidene)ethylenediiminocobalt(Cosalen), SBA-15 molecular sieve, Hydrophobic modification, Liquid-phase oxidation of toluene