Papers by Author: Ji Hwan Park

Abstract: Mesoporous MCM-41 materials were prepared using the conventional thermal and microwave heating method. Both in conventional thermal and microwave heating synthesis of MCM-41, tetraethyl orthosilicate (TEOS) and cetyltrimethyl ammonium bromide (CTAB) were used as Si source and template, respectively. Microwave heating was carried out in a modified 400 W, 2.45 GHz microwave oven. In both methods, the crystallization temperatures was 70 °C and crystallization time was 3~12 h. The prepared MCM-41 samples were characterized by XRD, TEM and SEM. The XRD patterns of MCM-41 samples prepared from both the methods were typical of a relatively well ordered material. TEM results also revealed that the MCM-41 samples prepared from both the methods possess the regular hexagonal array of mesoporous channels. On the contrary, SEM has shown the difference in morphologies of the MCM-41 samples prepared from both the methods. The samples prepared by conventional thermal heating method mainly consist of irregular and small particles, whereas the samples prepared by microwave heating method have elongated rope-like structure and their length extends longer than 10 μm.

Abstract: Transient reaction of adsorbed monolayer of acetic acid was used to compare the photocatalytic properties of TiO2 (Degussa P-25), titanium silicalite (TS-1) and Ti-MCM-41. TS-1 and Ti-MCM-41 catalysts with Si/Ti ratio of 50 were prepared by in-situ crystallization. The catalysts were characterized using XRD and UV-DRS. During photocatalytic oxidation (PCO), CO2 and HCHO were formed on P-25 TiO2, whereas CO2 and CH4 formed on TS-1 and Ti-MCM-41. Acetic acid decomposed photocatalytically on P-25 TiO2 to form CO2, CH4 and C2H6. On the contrary, CO2 and CH4 were formed on TS-1 and Ti-MCM-41 during photocatalytic decomposition (PCD). The rates of product formation during PCD were lower than PCO. The TS-1 and Ti- MCM-41 catalysts were less active per gram of catalyst. However, the TS-1 and Ti-MCM-41 catalysts had much higher adsorption capacities for organics. Therefore, it seems that the TS-1 and Ti-MCM-41 catalysts have some advantages in applications to PCO of organic comtaminants under conditions where the organic concentrations vary widely.

Abstract: We investigated the feasibility of preparing nanocrystalline oxotitanium phthalocyanine (TiOPc) from crude TiOPc using liquid-phase direct recrystallization under the microwave irradiation. Different crystal structures and morphologies of TiOPc were obtained through acidtreatment and recrystallization method. The nanocrystalline TiOPcs prepared in various conditions were characterized by the means of an X-ray diffractometry (XRD), a transmission electron microscopy (TEM) and a photoconductivity measuring device.