The Research Of Synthesis And Catalytic Performance Over Mesoporous Cobalt-based Catalysts Via Rapid Ultrasonic Technique In The Styrene Oxidation

The catalytic oxidation of styrene has an important research value in the field of organicsynthesis and industrial production as it can produce benzaldehyde and styrene oxide. Thecommonly used catalysts was prepared by hydrothermal method. However, hydrothermalmethod wastes long time and tremendous heat. In this paper, the rapid preparation of SBA-15with cobalt (Co) introduction was performed via the ultrasonic irradiation. The catalyticproperties of the synthesized Co-SBA-15were investigated by examining the oxidation ofstyrene with hydrogen peroxide. The effect of pH values on the textural properties wereextensively investigated using small-angle X-ray Diffraction (XRD), N2adsorption–desorption isotherms and Transmission Electron Microscipy (TEM). Thecharacterization results showed that the incorporation of Co by ultrasonic method exhibited awell-ordered hexagonal mesoporous structure with higher surface area and pore volume. Thephysicochemical properties and catalytic activity of the Co-SBA-15catalysts via ultrasonictechnique possessed the comparable characteristics as those prepared via conventionalhydrothermal method.Meanwhile， cobalt-containing MCM-41was prepared via the similar ultrasonicirradiation. The textural properties of cobalt-containing SBA-15and MCM-41wereextensively investigated using XRD, N2adsorption-desorption isotherms and TEM. Thecobalt species in SBA-15and MCM-41were characterized by X-ray photoelectronspectroscopy (XPS), temperature programmed reduction (TPR) and diffuse reflectancespectroscopy (DRS). The characterization results showed the cobalt species in Co-SBA-157.5was mainly in the single-site Co(II) state but in Co-MCM-417.5was mainly in Co3O4Cocontaining SBA-15and MCM-41were active in the oxidation of styrene using hydrogenperoxide as oxidant and Co(II) in Co-SBA-157.5exhibited the better catalytic performancethan Co3O4in Co-MCM-41.In addition, cobalt supported on carbon nanotubes (Co/CNTs) was developed as a novelcost-effective catalyst by ultrasonic impregnation techniques. The structures of the Co/CNTscatalysts were characterized, and the presence of cobalt species was confirmed and theactivity of Co/CNTs catalysts were examined for the epoxidation of styrene. The results showed that the cobalt species in Co/CNTs was in the single-site Co(II) state and Co/CNTscatalyst exhibited good catalytic performance and strong stability. The catalytic behavior ofCo/CNTs catalysts was closely correlated with the oxidants, supports, and solvents，reactiontime. The reaction condition was optimized: with TBHP as an oxidant, acetonitrile as asolvent,10wt%cobalt as loading content,10h as reaction time,51.15%of styreneconversion and71.82%of the styrene oxide selectivity can be achieved.