Significant improvement of styrene oxidation over mononuclear/binuclear carboxyl metal phthalocyanine-attapulgite composites

Novel tetrasubstituted carboxyl metal phthalocyanine-ATP composites (CoTCPc-ATP) and hexa-substituted binuclear carboxyl metal phthalocyanine-ATP (biCoTCPc-ATP) catalysts were prepared by an ultrasonic impregnation method. The as-prepared samples are characterized by UV-Vis spectroscopy (UV-Vis), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The oxidation of styrene was examined by using tert-Butyl hydroperoxide (TBHP) as oxidant when CoTCPc-ATP/biCoTCPc-ATP composites are employed as catalysts. It was found that the biCoTCPc-ATP/composites exhibited more efficient catalysts comparing with CoTCPc-ATP in the styrene oxidation reaction. For the reason that the binuclear phthalocyanine had an enlarged pi electron conjugated system, could provide more active sites and possessed the enhanced electronic reserve capacity compared with the mononuclear metal phthalocyanine contributing to the more prominent catalytic performance. Both composites can catalyze the oxidation of styrene to form styrene oxide as the main product along with benzaldehyde as the secondary product. Furthermore, the potential mechanism of the catalytic oxidation of styrene is also proposed.