Authors:Lina Han, Soo-Jin Choi, Moon-Seok Park, Seon-Myong Lee, Yu-Jin Kim, Moon-Il Kim, Binyuan Liu, and Dae-Won Park
In this study, a series of imidazolium-based ionic liquids (ILs) having carboxylic acid moieties were synthesized and used as new homogeneous catalysts to synthesize cyclic carbonates from CO2 and epoxides. Even in the absence of any co-catalyst and organic solvent, carboxylic-acid-functionalized ILs showed better catalytic activity in the coupling reaction of CO2 and styrene oxide for the production of styrene carbonate than did hydroxyl-functionalized ILs and conventional ILs without any functional moieties. A detailed investigation was carried out on a variety of factors that affected the reactivity, such as the alkyl chain length and the molecular composition of IL molecules including the halide ions. The effect of various reaction parameters such as reaction time, temperature, CO2 pressure and catalyst amount was also investigated in detail. The mechanism underlying the enhanced rate of the cycloaddition reaction in the presence of carboxylic-acid-functionalized ILs was proposed.
Authors:Jung-Nam Park, Jeong Kuk Shon, Mingshi Jin, Soo Sung Kong, Kiyoung Moon, Gwi Ok Park, Jin-Hyo Boo, and Ji Man Kim
Highly ordered mesoporous ruthenium dioxide (meso-RuO2) has been successfully synthesized by controlling the surface hydrophobicity of a mesoporous silica template (KIT-6) via a nano-replication method. The meso-RuO2 material, thus obtained, exhibits a well-defined mesostructure and high surface area (131 m2 g−1). The physicochemical properties of the meso-RuO2 material are characterized by electron microscopy, X-ray diffraction, N2 adsorption–desorption, temperature programmed techniques, and X-ray photoelectron spectroscopy. Pretreatment of the meso-RuO2 catalyst under different gas environments (O2, H2 and CO) strongly affects the catalytic activity towards CO oxidation. The meso-RuO2, pretreated by O2 flowing at 200 °C, exhibited excellent catalytic activity for CO oxidation, 100% CO conversion with long-term stability at room temperature, whereas the meso-RuO2 catalysts with pretreatment under other conditions are not very active at room temperature. It is found that the surface oxygen species generated on the meso-RuO2 during O2 pretreatment at 200 °C provide CO oxidation activity at room temperature.
Authors:Mi-Young Kim, Se Min Park, Jung-Hyun Park, Chae-Ho Shin, Won-Jin Moon, Nark-Eon Sung, and Gon Seo
Platinum catalysts supported on silicas with various physicochemical properties were prepared in order to investigate the effect of silica characteristics on their platinum dispersion and catalytic activity in the oxidation of carbon monoxide. Although titania-incorporation into silica and further treatment of the impregnated platinum precursor with hydrogen peroxide were effective for improving the dispersion and stability of platinum catalysts supported on silicas, regardless of the characteristic of the silicas, the platinum catalysts supported on fumed silica with a medium level of surface hydroxyl group concentration exhibited the highest catalytic activity among those supported on mesoporous silica, silica gel, and precipitated silica. The required properties of the highly active platinum catalyst seemed to be a high dispersion of platinum, the formation of a stable titania layer, and the generation of strong acid sites. By contrast, the precipitated silica with a small surface area and high concentration of surface hydroxyl groups was not appropriate for a catalytic support for platinum catalysts.
Authors:Bo-Hyun Kim, Tae-Hee Lim, Jin-Woong Roh, Sang-Geun Lee, Chang Ju, Seong Park, Seong Hong, and Gun Lee
Undoped and Cr-doped Bi12TiO20 (BTO) were prepared and used as photocatalysts for the degradation of formic acid both under visible light and UV irradiation.
The effects of the Cr doping on the visible light response and the photocatalytic activity of BTO were investigated. The prepared
catalysts were characterized by using XRD, XPS, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy.
The doping of Bi12TiO20 with low concentration of Cr leads to noticeable increase in visible light absorption and decrease in the recombination rate
of photo-generated electrons and holes. As a result, the Cr-doped BTO showed a higher photocatalytic activity for the degradation
of formic acid both under visible light and UV irradiation, as compared with undoped BTO.