Selective oxidation of styrene to benzaldehyde by cobalt phthalocyanine-multi-walled carbon nanotube composites

Abstract

Novel tetrasubstituted cobalt phthalocyanine-multi-walled carbon nanotube composites ([4a(OPh-p-Cl)CoPc]-MWCNTs) were prepared to efficient catalytic oxidation of styrene to benzaldehyde. The [4a(OPh-p-Cl)CoPc]-MWCNTs composites were characterized by UV–vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. In order to achieve efficient and selective catalysis, the effects of solvent types, oxidant types, catalyst amount, temperature and reaction time on catalytic performance have been studied. It was found that the [4a(OPh-p-Cl)CoPc]-MWCNTs composites performed very high catalytic activity in the styrene oxidation reaction. The highest styrene conversion (99.17%) and benzaldehyde selectivity (88.93%) were obtained under the optimum conditions of 20 mg of [4a(OPh-p-Cl)CoPc]-MWCNTs, oxidant being TBHP for 2 mL, and in THF at 80 °C for 4h. Furthermore, the possible reaction mechanism for [4a(OPh-p-Cl)CoPc]-MWCNTs composites selectively oxidized styrene to benzaldehyde was also proposed.