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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.
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.
AROMATIZATION OF PENTANE CATALYZED OVER VARIOUS METALLOSILICATES
Woo, Seong Ihl,Park, Yong Ki,Kim, Do Heui 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.4
Various metallosilicates were synthesized using a hydrothermal method and characterized by SEM, XRD, ^(29)Si MAS NMR, chemical analysis and surface area measurements. These results showed that they had a MFI structure. The pentane aromatization reaction was carried out over these metallosilicates in a continuous flow reactor at 550℃, He/pentane=3, WHSV=1.5 h^(-1) and 1 atm. Among the various metallosilicates, [Ga]ZSM-5(20) (52.3 %) and [Zn]ZSM-5(40) (37.6 %) showed higher aromatic selectivities for pentane aromatization. When [Al] ZSM-5(40) was ion-exchanged with gallium nitrate and zinc chloride, the selectivities for aromatics increased from 23.0 % to 35.5 % and to 32.7 %, respectively. The Si/metal mole ratios of [Ga]ZSM-5 and [Al]ZSM-5 were changed from 20 to 250 and NH₃ temperature programmed desorption (TPD) was carried out. As the Si/metal ratio was changed from 250 to 20, the selectivities for aromatics were increased from 5.3 % to 52.3 % over [Ga]ZSM-5 and from 10.1 % to 25.7 % over [Al]ZSM-5. NH₃TPD of [Ga]ZSM-5 indicated that the sites of medium acidity play an important role in the formation of aromatics. When H₂ and CO were added to the reactant of pentane, the production of methane and ethane increased and that of aromatics decreased.
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, Taek Kyu,Ko, Young Soo 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.5
Silica supported MgCl₂/THF/TiCl₄catalyst (SiO₂/MgCl₂/THF/TiCl₄) was prepared, and then decomposed thermally. The amount of produced gas [tetrahydrofuran (THF) and 1,4-dichlorobutane (DCB)] was measured with gas chromatography (GC) and mass spectrometer. SiO₂/MgCl₂/THF/TiCl₄catalyst started to decompose around 85℃, and further decomposed at 113, 150 and 213℃. THF was mainly produced, but very small amount of DCB evolved during temperature programmed decomposition (TPD), while unsupported MgCl₂/THF/TiCl₄produced DCB significantly. Polymerization rate of ethylene with SiO₂/MgCl₂/THF/TiCl₄decreased when it was preheated at 85 and 110℃ for 5 and 60 min, respectively, while that of unsupported MgCl₂/THF/TiCl₄increased after same pretreatment condition. It can be suggested that Mg/Ti bimetallic complex anchored on the surface of silica through OH group of it has weak interaction between Mg and Ti species.
Characterization of Alumina Modified with Sulfate and Phosphate
Woo, Seong Ihl,Kim, Seo Il 한국화학공학회 1991 NICE Vol.9 No.6
The acidity and surface properties of alumina modified with sulfate (Al-S) and phosphate (Al-P) were characterized by IR, NH₃ TPD and 1-butene isomerization reaction. The Point of Zero Charge (PZC) of modified alumina and the amount of Mo anion adsorbed on modified alumina were measured. The PZC of modified alumina and the amount of Mo anion adsorbed on modified alumina decreased with increasing modifier content. Non-linear relationship between the PZC and Mo uptake in modified alumina was observed in Al-S and Al-P. The bonding mode of sulfate on alumina changed with increasing sulfate content. The Bronsted acid site appeared in alumina modified with sulfate of 10 wr%.
WET OXIDATION OF WASTERWATER CONTAINING HYDROCARBONS BY NOVEL SUPPORTED PD CATALYSTS
Woo, Seong Ihl,Cho, Se In,Kim, Doo Seong 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.6
Pd catalysts supported on TiO₂, ZrO₂, ZSM-5, MCM-41 and activated carbon were used in catalytic wet oxidation of hydrocarbons such as phenol, m-cresol and m-xylene. It was found that the Pd/TiO₂catalyst was highly effective in the wet oxidation of hydrocarbon. The activities, of catalysts with various hydrocarbon species, catalyst support, oxidation state of catalyst performed in a 3-phase slurry reactor show that reaction on Pd surface is more favorable than that in aqueous phase and that the active site is oxidized Pd in catalytic wet air oxidation of hydrocarbons. Based on the experimental results, a plausible reaction mechanism of wet oxidation of hydrocarbons catalyzed over Pd/TiO₂catalyst was proposed. This catalyst is superior to other oxide catalysts because it suppressed the formation of hardly-degradable organic intermediates and polymer.