• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1763-1770
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• 2007

Strong solid acid catalysts, NiO/Al2O3-TiO2/WO3 for ethylene dimerization were prepared by the addition of Al2O3 and the modification with WO3. The acid sites and acid strength were increased by the inductive effect of WO3 species bonded to the surface of catalysts. The larger the dispersed WO3 amount, the higher both the acidity and catalytic activity for ethylene dimerization. The addition of Al2O3 to TiO2 up to 5 mol% enhanced acidity and catalytic activity gradually due to the interaction between Al2O3 and TiO2 and consequent formation of Al-O-Ti bond.

• Journal of Environmental Science International
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• v.17 no.5
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• pp.565-571
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• 2008

The surface properties of activated carbon modified by acids and base were studied. The influence of the surface chemistry on the adsorption of benzene and acetone vapor on modified activated carbons has been investigated The modified activated carbons were obtained by treatment with acetic acid ($CH_3COOH$), nitric acid ($HNO_3$) and sodium hydroxide (NaOH). The modified activated carbons had similar porosity but different surface chemistry and adsorption characteristics. The total surface acidity (sum of functional groups) of activated carbon (AC-AN) treated by nitric acid was 2.6 times larger than that of activated carbon (AC) before the acid treatment. Especially, carboxyl group was much developed by nitric acid treatment. The benzene equilibrium adsorption capacity of AC-AN decreased 20% more than that of AC. However, the acetone equilibrium adsorption capacity of AC-AN increased 20% more than that of AC because of the large increase of carboxyl group and acidity.

• Carbon letters
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• v.3 no.4
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• pp.219-225
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• 2002

The two-step surface modifications of activated carbon was carried out to improve the adsorption capacity of toxic heavy metal ions in liquid phase. Physical and chemical properties of the as-received activated carbon (AC) and two kinds of surface-modified activated carbons ($1^{st}AC$ and $2^{nd}AC$) were evaluated through the BET analysis, surface acidity, and oxides measurements. Specific surface area and pore volume did not significantly change, but surface oxide-group remarkably increased by the surface modification. Equilibrium and batch adsorptions of the various metals, such as Pb, Cd, and Cr, using AC, $1^{st}AC$, and $2^{nd}AC$ were performed at initial pH 5. The adsorption capacity and rate of $2^{nd}AC$ were higher than those of AC and $1^{st}AC$. The carboxylic/sodium carboxylate complex groups were developed from the two-step surface modification of activated carbon, which strongly affected the adsorption of metal ions.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.902-907
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• 2006

Freeze dried crude bacteriocin was encapsulated within an acid-soluble coating material, Eudragit EPO, using a surface modification technique through a hybridization system. The pH and titratable acidity of control yoghurt were 3.92 and 1.56%, respectively, after 24 hr of fermentation at $42^{\circ}C$, whereas yoghurt containing 500 AU/mL encapsulated bacteriocin exhibited a higher pH (4.37) and lower titratable acidity (1.2%). Yoghurt containing encapsulated bacteriocin had significantly lower titratable acidity when the duration of fermentation (to pH 4.5) and subsequent refrigerated storage ($4^{\circ}C$) was longer than 20 days. There were no significant differences in the viability of lactic acid bacteria after 15 hr of fermentation. This suggests that microencapsulated bacteriocin has the potential to control the excessive growth of yoghurt starters caused by temperature abuse or post-acidification.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.127-128
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• 2006

Nafion/basic polymer composite membranes were prepared to reduce the methanol crossover for the application of direct methanol fuel cell. The thermal and mechanical properties increased with increasing basic polymer contents due to the formation of complex via acid/basic interaction. The water uptake, proton conductivity, methanol permeability decreased with increasing basic polymer concentration by reduction of acidity associated with the formation of acid/base complex. The molecular effect on those properties was not considerable.

• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.821-829
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• 2006

A series of catalysts, $NiO/La_2O_3-ZrO_2/WO_3$, for acid catalysis was prepared by the precipitation and impregnation methods. For the $NiO/La_2O_3-ZrO_2/WO_3$ samples, no diffraction lines of nickel oxide were observed, indicating good dispersion of nickel oxide on the catalyst surface. The catalyst was amorphous to X-ray diffraction up to 300 ${^{\circ}C}$ of calcination temperature, but the tetragonal phase of $ZrO_2$ and monoclinic phase of $WO_3$ by the calcination temperatures from 400 ${^{\circ}C}$ to 700 ${^{\circ}C}$ were observed. The role of $La_2O_3$ in the catalyst was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The high acid strength and high acidity were responsible for the W=O bond nature of complex formed by the modification of $ZrO_2$ with $WO_3$. For 2-propanol dehydration the catalyst calcined at 400 ${^{\circ}C}$ exhibited the highest catalytic activity, while for cumene dealkylation the catalyst calcined at 600 ${^{\circ}C}$ showed the highest catalytic activity. 25-$NiO/5-La_2O_3-ZrO_2/15-WO_3$ exhibited maximum catalytic activities for two reactions due to the effects of $WO_3$ modifying and $La_2O_3$ doping.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.895-901
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• 1999

The acid characteristics of ${\beta}$-zeolites was modified by the different calcination conditions in order to remove template and the post-treatments such as ammonium ion exchange and HCl treatment. Alkylation of benzene with propene and isopropanol was carried out over the catalysts to investigate the effect of acid characteristics on the selectivity to cumene in this reaction. The $Br{\ddot{o}}nsted$ acidity(IR $3610cm^{-1}$ band) of ${\beta}$-zeolite was significantly reduced by a deep bed calcination compared to that of ${\beta}$-zeolite calcined in a shallow bed. Moreover, extraframework aluminum species which did not show acidity were produced by the framework dealumination on the deep bed calcined ${\beta}$-zeolite. $Br{\ddot{o}}nsted$ acidity of deep bed calcined ${\beta}$-zeolite was significantly recovered by ammonium ion exchange, however, it was partially recovered by a weak HCl treatment. It was found that the framework aluminum as well as the extraframework aluminum were extracted by a strong HCl treatment. The selectivity to cumene was shown to be about 95% on the shallow bed calcined ${\beta}$-zeolite, however, it decreased to 90% on the deep bed calcined one. The post-treatment such as ammonium exchange and weak HCl treatment enhanced the selectivity to cumene up to 93% by the partial recovery of $Br{\ddot{o}}nsted$ acidity. Propene was proved to be a good alkylating agent for the selectivity to cumene compared to isopropanol.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2459-2465
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• 2007

V2O5/TiO2-ZrO2 catalyst modified with V2O5 was prepared by adding Ti(OH)4-Zr(OH)4 powder into an aqueous solution of ammonium metavanadate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using XRD, DSC, solid-state 51V NMR, and FTIR. In the case of calcination temperature of 500 oC, for the catalysts containing low loading V2O5 below 25 wt % vanadium oxide was in a highly dispersed state, while for catalysts containing high loading V2O5 equal to or above 25 wt % vanadium oxide was well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of TiO2-ZrO2. The strong acid sites were formed through the bonding between dispersed V2O5 and TiO2-ZrO2. The larger the dispersed V2O5 amount, the higher both the acidity and catalytic activities for acid catalysis.

• Journal of the Korean Society of Tobacco Science
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• v.16 no.2
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• pp.191-197
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• 1994

Relationships between surface structure and adsorption properties of smoke components were investigated in surface-modified and un-modified activated carbon filter cigarettes. Commercially available activated carbon was treated with nitric acid and hydrogen peroxide as oxidant, and their pore volume, surface structure, BET surface area, pore type and size were studied. BET surface area and pore volume were decreased by nitric acid treatment, but median pore diameter was 8.1 $\AA$, which showed better development of pore compared with that of un-modified activated carbon, 6.9 $\AA$. In case of hydrogen peroxide treatment, BET surface area and pore volume were increased. Their pore was found to be a slit type based on V-t plot analysis. Neutralization capacities for bases of different strength (NaHCO3, Na2CO3, NaOEt and NaOH) showed that the majority of the acidic surface groups are of weak acidity. Modification of the activated carbon surface led to a slight change in adsorption properties when analyzing the smoke of triple-filter cigarette with surface-modified activated carbon.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.307-312
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• 2001

Adsorption capacities of toxic heavy metal ions using as-received carbon(AC), single and double surface-modified activated carbon(OAC and DSMC) in wide pH ranges are extensively evaluated. Physical and chemical properties of surface-modified activated carbons are evaluated through BET analysis, surface acidity and oxides measurements. Based oil tile adsorption isotherms of Pb, Cd and Cr ions by AC, OAC and DSMC, the adsorption amount on DSMC was obviously higher than that on the other carbons. Breakthrough behaviors of ternary metal ions in a column packed with three kinds of carbon were also characterized with respect to the variations of the influent pH and concentration. The adsorption capacity of DSMC in a fixed bed stood a favorable comparison with that of as-received carbon.