The Study On Novel One-step Reaction For Catalytic Epoxidation Of Gaseous Cyclohexane

In this paper, a series nanocomposite catalysts of Ag₂O/SiO₂, TiO₂/SiO₂ and Ag₂O–TiO₂/SiO₂ were synthesized by solution combustion method with anhydrous ethanol as fuel. Epoxycyclohexane was obtained by one-step reaction of catalytic epoxidation of gaseous cyclohexane with above catalyst.SEM, XRD, Raman, FT-IR and N2 adsorption–desorption were used to study surface structure, crystalline, surface morphology, dispersion and interaction of the catalysts and supports. The results showed that Ag₂O–TiO₂/SiO₂ nanocomposite catalysts displayed disordered mesopore structure, and most of the pore size distributed about 16 nm, whose catalysts particles are spherical with diameter between 20 and 30 nm. Ag₂O–TiO₂/SiO₂ nanocomposite catalysts exhibit a broad diffraction peak of amorphous silica, which indicates that silver oxides and titania are highly dispersed on the silica surface, chemical binding interaction may occurred between Ag₂O and TiO₂, and formed Ti–O–Ag bond.The reaction of catalytic epoxidation of gaseous cyclohexane was investigation by using oxygen and nanocomposite catalyst containing different activity components. The results from the experimental evaluate the activity of nano-composite catalysts. It is found that Ag₂O–TiO₂/SiO₂ (7.1 wt.% Ag₂O,nSi/nTi=25)samples exhibited higher catalytic performance than Ag₂O/SiO₂, TiO₂/SiO₂ and the other Ag₂O–TiO₂/SiO₂ samples on epoxidation of cyclohexane. 54.3% cyclohexane conversion and 86.8% selectivity to olefins and oxygenates with cyclohexene, epoxy cyclohexane and 5-hexenal as the dominant products, 32.7% epoxycyclohexane selectivity and 17.7% epoxycyclohexane yield can be achieved under 380℃with the flowing rate of oxygen, gaseous cyclohexane and nitrogen is 7.5 mL·min?1, 5 mL·h?1 and 7.5 mL·min?1, respectively.On the adjusting process of catalytic property of catalyst, we found that nanometer calcium carbonate can used to be an excellent support. Nanometer calcium carbonate were studied out to be an support for further optimize the catalytic epoxidation of gaseous cyclohexane. As the catalyst properties can be affected by the morphologies of support, we synthesized different morphologies of nanometer calcium carbonate by reverse microemulsion method, and the influences of surfactants and the composition of the reverse microemulsion upon the surface morphologies of calcium carbonate were investigated.