• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1785-1792
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• 2003

Zirconia modified with $MoO_3$ was prepared by impregnation of powdered $Zr(OH)_4$ with ammonium heptamolybdate aqueous solution followed by calcining in air at high temperature. Spectroscopic studies on prepared catalysts were performed by using FTIR, Raman, XRD, and DSC and by measuring surface area. Upon the addition of molybdenum oxide to zirconia up to 15 wt%, the specific surface area increased in proportion to the molybdate oxide content, while acidity measured by irreversible chemisorption of ammonia exhibited a maximum value at 3 wt% of $MoO_3$. Since the $ZrO_2$ stabilizes the molybdenum oxide species, for the samples equal to or less than 30 wt%, molybdenum oxide was well dispersed on the surface of zirconia and no phase of crystalline $MoO_3$ was observed at any calcination temperature above $400^{\circ}C$. The catalytic activities for cumene dealkylation were roughly correlated with the acidity of catalysts measured by ammonia chemisorption method, while the catalytic activities for 2-propanol dehydration were not correlated with the acidity because weak acid sites are necessary for the reaction.

• 한국지반환경공학회 논문집
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• 제20권1호
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• pp.27-33
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• 2019

산성배수가 발생하는 비탈면에서 생태적 녹화를 위한 산성배수 중화기법을 알아보기 위한 연구를 진행하였다. 산성배수중화기법을 위한 4가지 유형의(무처리, 석회고토 처리, 인산염 처리, 석회고토 + 인산염 처리) 시험구를 조성하였다. 실험결과 산도(pH), 피복율(%), 고사율(%), 식물뿌리상태 등에서 중화기법에 따른 유의차가 발생하는 것을 알 수 있었다. 중화기법에 따른 연구결과 (첫 번째 : 석회고토 + 인산염 처리, 두 번째 : 인산염 처리, 세 번째 : 석회고토 처리, 네 번째 : 무처리) 순서로 산도 중화 및 식물생장에 효과적이었다. 산성배수 비탈면에서 석회고토 처리와 인산염 처리는 토양산도 중화와 식물생장에 효과적이었으나, 석회고토 처리에 비해 인산염 처리가 더 효과적이었으며, 인산염 처리가 황화광물의 코팅 효과 때문에 토양산도 중화와 식물 생장에 더 효과적이라는 것을 알 수 있었다.

• 한국식품저장유통학회지
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• 제4권3호
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• pp.265-270
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• 1997

Effect of modified atmosphere packaging conditions on quality changes of dry jujube was investigated. Dry jujubes with moisture content of 26.7% were packaged in PET/Al/PE film pouches with modified atmospheres. The tested packages include those with normal air, vacuum, CO2 flushing, N2 flushing and O2 scavenger. Packages were stored at 25$^{\circ}C$ for 6 months, during which ascorbic acid concentration, browning level, titratable acidity and surface color were measured. Generally modified atmosphere packages could improve quality retention of dry jujubes except that vacuum package resulted in large surface color change. CO2-flushed package showed the best quality retention of high ascorbic acid content and low browning during 112 days, but caused high amounts of ascorbic acid destruction and browning in longer storage. In all the modified atmosphere packages titratable acidity reached a maximum followed by decline and subsequent rise, while it increased linearly with time in normal air package. Considering ascorbic acid retention browning level and surface color changes during 112 days, the packages of CO2 flushing and N2 flushing were better than others.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1231-1234
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• 2003

A sample procedure has been described to room temperature synthesis, mesoporous aluminosilicate materials with strong surface acidity by using a cationic surfactnat cetyltrimethylammonium bromide(CTABr) as the template agent. All samples were charecterized by X-ray diffraction(XRD) and nitrogen adsorption. The crystallinity and surface area of MCM-41 type aluminosilicats decrease with decreasing of Si/Al ratio. The influence of the aluminum contents of MCM-41 on the coordination of Al and on the acidity is studied by $^{27}Al$ MAS NMR and temperature programmed desorption of ammonia(TPD). It was shown that the incorporation of Al atoms into the framework causes increasing of acid site surface. And then Al atoms in the framework were incorporated tetrahedrally in structure, which gave a rise to cationic sites in the framework.

• Bulletin of the Korean Chemical Society
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• 제22권12호
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• pp.1309-1315
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• 2001

Zirconium sulfate supported on zirconia catalysts were prepared by impregnation of powdered $Zr(OH)_4$ with zirconium sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of zirconium sulfate to zirconia increased the phase transition temperature of $ZrO_2$ from amorphous to tetragonal due to the interaction between zirconium sulfate and zirconia, and the specific surface area and acidity of catalysts increased in proportion to the zirconium sulfate content up to 10 wt% of $Zr(SO_4)_2$. Infrared spectra of ammonia adsorbed on $Zr(SO_4)2}ZrO_2$ showed the presence of Bronsted and Lewis acid sites on the surface. $10-Zr(SO_4)_2}ZrO_2$ calcined at $600^{\circ}C$ exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by ammonia chemisorption method.

• 한국환경과학회지
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• 제17권5호
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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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• 제9권1호
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• pp.8-16
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• 2008

Oxidized activated carbons were prepared by reacting steam-activated carbon developed from pecan shells with nitric acid of varying strength (15, 30, 45 and 60%). The textural properties and the chemistry of the surface of the non-oxidized and of the oxidized carbons were determined from nitrogen adsorption and base neutralization capacities. The uptake of Pb(II) and Cd(II) from aqueous solution by these carbons was determined by kinetic and equilibrium experiments as well as by the column method. Treatment with nitric acid brought about drastic decrease in surface area and remarkable increase in the pore size of the carbon with these changes depending on the strength of nitric acid. Nitric acid increased the surface acidity by developing new surface oxygen functional groups of acidic nature. $HNO_3$-oxidized carbons exhibited high adsorption capacities for Pb(II) and Cd(II). The adsorption of these ions increased with the decrease of the surface pH of the carbon and with the increase of the solution pH from 2.5 to 6 and 7. The amount adsorbed from lead and cadmium was also related to the amount of surface acidity, the pH of the point of zero charge and on some metal ion parameters. Cadmium and lead uptake by the investigated carbons followed pseudo-second order model and the equilibrium sorption data fitted Langmuir adsorption model.

• 대한화학회지
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• 제23권3호
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• pp.161-164
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• 1979

$Ca^{2+},\;La^{3+},\;NH_4^+$ 등으로 양이온을 교혼하거나, 알루미늄을 추출한 합성 zeolite Y에 팔라듐을 담지시켜, 촉매산성도 및 담지된 금속의 유효표면적을, n-butane의 분해반응에서 촉매활성과 관련지어 조사하였다. 암모니아의 TPD(Temperature Programmed Desorption) 실험에 의하면 NaY < CaY < LaY 순으로 강한 산점의 양이 많아졌으며, 알루미늄 추출로 $SiO_2/Al_2O_3$의 비가 커질 수록 전체산점의 양은 감소되었으나, 강한 산점의 양은 증가되었다. CO의 화학흡착으로 측정한 담지금속의 유효표면적은 산성도가 큰 촉매에서 비교적 컸다. n-Butane의 zeolite 촉매에서의 반응은, 촉매의 산성도와 금속성분의 유효표면적에 관계되나, 전화율이 측정한 범위내에서의 유효표면적에 비례하므로 금속성분에 의한 탈수소반응이 중요한 단계로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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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.

• 한국식품저장유통학회지
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• 제4권2호
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• pp.123-130
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• 1997

To develop the prediction program for quality change of Citrus unshiu during marketing, we examined the quality characteristics of Citrus unshiu stored at experimental refrigerator set to 4, 8, 12 and 16$^{\circ}C$ for 2 months. According to the storage temperature the changes of quality characteristics were different respectively, but it was most severe during 16$^{\circ}C$ storage. Activation energy and Q10 value were 6683.16 cal/mol K and 1.53 respectively. The determination coefficient of regression equation of pH, acidity and vitamin C by surface response analysis were over 0.85. Using these regression equation, we developed the prediction program for the change of pH, acidity and vitamin C contents. The calculated values and experimental values of pH, acidity and vitamin C contents for short-term storage of Citrus unshiu were coincided well.