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Woo, Seong Ihl,Han, Jong Dae 한국화학공학회 1992 NICE Vol.10 No.1
The coordination changes of Co^(2+) in Y-zeolite prepared by ion-exchange and dehydrated at various temperatures, have been investigated by UV/VIS diffuse reflectance spectroscopy. Fully hydrated zeolites show an octahedral coordination of [Co(H₂)_6]^(2+) in the supercage with some interaction with the framework. During dehydration at high temperatures, Co^(2+) in Yzeolite changes its coordination, first from a symmetric to distorted tetrahedral and, successively, to an octahedral coordination. Fully hydrated sample of impregnated cobalt nitrate in Y-zeolite shows an octahedral coordination of Co(H₂O)_6(NO₃)₂. During dehydration at high temperature, the cobaltous nitrate decomposes to the cobalt oxide. However, the small amount of cobalt ions in cobaltnitrate are ion-exchanged simultaneously.
Woo, Seong Ihl,Han, Jong Dae 한국화학공학회 1993 NICE Vol.11 No.6
The coordination changes of Co^(2+) in CoNaY/NaOHs, prepared by cobalt ion-exchange and treatment with NaOH, during dehydration at various temperatures have been investigated by UV/VIS diffuse reflectance spectroscopy. After dehydration of CoNaY/NaOHs at 473 K, the DRS bands show the formation of mixed cobalt oxide species interacted with lattice oxygen. This mixed cobalt oxide species interacted with lattice oxygen decompose during further dehydration at 673 K. The strong intensities of the bands at 650, 575 and 530 nor after dehydration of CoNaY/NaOHs at 873 K indicate that a considerable amount of the cobalt ions remains in the sodalite cage with tetrahedral coordination even after dehydration at 873 K.
Woo, Seong Ihl,Kim, Il 한국화학공학회 1990 NICE Vol.8 No.3
The kinetics for decawite of etW enu pulymerizution catalyzed with fiCl, IcCI. Sio. has been investiated in the rancc of temperatures tetaeen 40 and 90C and in the range of ethylene pressures bwen 4 and 13=I atm. hhe decay of IxIwerizalion rate eras fitted well ht the ype of first order dec. The deay rate constant caused by nunennrr could Ire expressed by k.i-C. M. Some plnusibl specnlaticms htwc been propnsed on the deactivtic? merlt mism caused by numomer. THE activation enery for the deactivation reaction is 9.3 kcal mole.
Woo, Seong Ihl,Park, Yong Ki,Hong, Suk Bong,Uh, Young Sun,Kim, Chang Gyoun 한국화학공학회 1992 NICE Vol.10 No.3
Vanado-, fern, and gallosilicate catalysts were prepared from the mixtures containing colloidal silica, corresponding metal source, tetrapropylammonium bromide and VHF by hydrothermal crystallization at 175 for 7 days. The pH value of the reaction mixture was low(pH$lt;8) compared to the conventional methods. The metal compounds have higher solubilites in these conditions than conventional conditions(pH$gt;10). The size distribution and the size of final products were found to be more homogeneous and larger than those of metallosilicates prepared in strong alkaline media. The characterization of metallosilicates with IR, X-ray diffraction, SEM, EPR, and ^(29)Si MAS NMR, indicated that corresponding metal atoms were successfully incorporated into the tetrahedral lattice sites of the ZSM-5 structure.
Thermal Stability of [ B ] ZSM -5 Molecular Sieve
Woo, Seong Ihl,Hong, Suk Bong,Uh, Young Sun,Lee, Jae Kyu 한국화학공학회 1991 NICE Vol.9 No.2
The thermal stability of [B]ZSM-5 (boronsilicalite) has been examined by IR, XRD, ^(11)B MAS NMR and XPS techniques. [B]ZSM-5 and amorphous borosilicate were converted to a-cristobalite at ftigh temperatures (=750℃). However, Na-free amorphous borosilicate was not converted to a-cristobalite at 150℃. Therefcre, the presence of Naionsiat [B]ZSM-5 would determine whether this transition occurred or not. When the phase transition to a-crstoba(ite occurred, most of B atoms tetrahedrally coordinated were released from the ZSM-5 structure and migrated to the exterior surface as a boron compound having trigonal BO₃, units and oxidation states of 3.
Woo, Seong Ihl,Kim, Seo Il,Kim, Choong Hyon 한국화학공학회 1995 Korean Journal of Chemical Engineering Vol.12 No.5
CoMo/Al₂O₃ catalysts were prepared by impregnating Cobalt nitrate solution into oxidic or sulfided Mo/Al₂O₃. The properties of CoMo/Al₂O₃ catalysts were characterized by XRD, TPS, oxygen chemisorption and ESR. Catalytic activity of CoMo/Al₂O₃catalyst was evaluated by thiophene HDS as a probe reaction. When CoMo/Al₂O₃ catalyst was prepared by impregnating Cobalt nitrate solution into sulfided Mo/Al₂O₃, the interaction between Mo and alumina became weaker and the formation of synergic phase was facilitated. These structural changes may explain higher HDS activity of CoMo/Al₂O₃ catalyst prepared by impregnating Cobalt nitrate solution into sulfided Mo/Al₂O₃.
Seong Ihl Woo,Seo Il Kim,Choong Hyon Kim 한국화학공학회 1996 화학공업과 기술 Vol.14 No.1
N/A CoMo/Alo catalysts were prepared by impregnating Cobalt nitrate solution into oxidicur sulfided Mo/Al3. the properties of CoMo/AI3, catalssts were cbaracteried by XKD. TPS, oxygen chemisrptim and ESR. Catalytic activity of CoMo/AIU, catalyst was evaluated be thiophene (II)S as a prohe reaction. When CuMo/Al, catalyst was prepared by impregnating Cobalt nitrate solution into sulfided Mo/AIO. the nteraction between Mo and alumina became weaker and the formation of synergic phase was facilitated. These structural changes may explain higher HDS activity of CoMo/AIO catalyst prepared by impreKnating Cobalt nitrate solution into sulfided 110/41.
Crystallization of Ferrisilicate Molecular Sieve in the Presence of Fluoride Ions
Woo, Seong Ihl,Hong, Suk Bong,Uh, Young Sun 한국화학공학회 1990 NICE Vol.8 No.1
the ferrisilicate molecular sieve analogue of the 7SMS was prepared from the weak alkaline medium (pH 8) in the presence of F- ions, which was confirmed by IR, X-ray powder diffraction, EPR, and ^(29)Si MAS NMR studies. The addition of F-ion in the preparation of metallosilicate molecular sieves could reduced the pH value of the reaction mixture, and prevent from the precipitatiorr of metal ions which are sparingly soluble in strong alkaline media.