• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.560-567
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• 2020

In this study, we investigated that the effect of alkali metals [Na(Sodium) and K(Potassium)], known as representative deactivating substances among exhaust gases of various industrial processes, on the NH₃-SCR (selective catalytic reduction) reaction of V/W/TiO₂ catalysts. NO, NH₃-TPD (temperature programmed desorption), DRIFT (diffuse reflectance infrared fourier transform spectroscopy analysis), and H₂-TPR analysis were performed to determine the cause of the decrease in activity. As a result, each alkali metal acts as a catalyst poisoning, reducing the amount of NH₃ adsorption, and Na and K reduce the SCR reaction by reducing the L and B acid points that contribute to the reaction activity of the catalyst. Through the H₂-TPR analysis, the alkali metal is considered to be the cause of the decrease in activity because the reduction temperature rises to a high temperature by affecting the reduction temperature of V-O-V (bridge oxygen bond) and V=O (terminal bond).

• Clean Technology
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• v.17 no.3
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• pp.225-230
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• 2011

Characteristics of hydrocarbon selective catalytic reduction of NOx using various noble metal catalysts were investigated. The best active metal is Pt, supports are $CeO_2$ and $TiO_2$ by strong interactions between active metals, and 55% of conversion rate of NOx is shown. Pd, Rh and Ag catalysts presented a conversion of less than 20% as active metals, and supports also showed the poor activity compared to $SiO_2$ and $ZrO_2$. Experiments were performed with different types of reducing agents, amount, concentration of oxygen and space velocity in order to investigate the performance of catalysts according to operating conditions. The results confirm that the methane is better than propane as a reducing agent, and as the ratio of methane/nitrogen oxide increases, the catalytic activity increased, as the concentration of oxygen increases and space velocity decreases, the performance of catalysts increased.

• Clean Technology
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• v.22 no.2
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• pp.106-113
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• 2016

This study was performed to study the photocatalyst for controlling the pollutant such as CO, C₂H₅OH and H₂S by the UV light. This was shown in a catalyst having the same volume and the same surface area, that the structure in which the UV light to reach the interior structure exhibits more excellent activity. However, the activity of this activity of this photocatalyst removal of CO was very low. This problem can be solved by performing a reduction process by the addition of the precious metal series of Pt. Particularly, the amount of chemical species Pt⁰ incerased in the surface of Pt/TiO₂ photocatalyst through the reduction process, which make the reaction activity of photocatalyst excellent to the removal of the CO.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.300-306
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• 2014

In this study, we investigated the noble metal catalysts for HCHO removal at room temperature. These catalysts were characterized by XRD, FT-IR, CO-chemisorption. As a result, Pt and Pd based catalysts prepared by the reduction treatment showed the superior HCHO oxidation ability at room temperature. When the catalysts were prepared using $TiO_2$ support, which is well known as the reducing support, showed the superior activity. Also, the activity decreased by the agglomeration of active metal with increasing the reduction time. In case of reduction catalysts, it has been confirmed that the desorption and adsorption ability properties of HCHO is excellent at room temperature.

• Clean Technology
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• v.15 no.2
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• pp.130-136
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• 2009

Commercial catalyst (Cu-Zn/$Al_2O_3$, Johnson Matthey Co., 83-3 Catalyst) was applied to the hydrogen production by steam reforming of methanol in the micro-channel reactor (MCR). The steam reforming of methanol was tested over Cu-Zn catalyst at temperatures in the range of 200 and 300$^{\circ}C$, the catalyst size of 0.05${\sim}$2.2 mm, the space velocity of 3,000${\sim}$10,000 $hr^{-1}$ in a fixed bed continuous flow reactor. The conversion of methanol and the yield $H_2$ preferred high temperatures and low space velocities, and had optimal results with the particle size of 0.35 mm. Based on the results from experiments with fixed bed reactor, two types of MCR, boat bed and stacked bed MCRs, were studied. The stacked bed type MCR showed better methanol conversion compared with the boat type one.

• Prospectives of Industrial Chemistry
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• v.22 no.5
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• pp.25-40
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• 2019

전 세계적으로 환경문제를 해결하기 위한 방안으로 환경규제를 강화시키며 특히 다양한 대기오염 물질 중 최근 큰 이슈인 초미세먼지 저감을 위해 전구물질로 알려진 질소산화물을 제어하기 위한 다양한 기술개발이 가속화되고 있다. 특히, 다양한 처리기술 중에 기술적·경제적인 이점을 갖춘 선택적 촉매환원법(selective catalytic reduction, SCR) 기술을 통하여 질소산화물 제거를 위해 암모니아를 환원제로 반응에 참여시켜 인체에 무해한 H₂O, N₂로 전환하는 기술이 대표적이다. 최근 전 세계적으로 다양한 산업군에서 질소산화물이 배출되고 있으며, 점오염원뿐만이 아니라 비점오염원(mobile sources)에 대한 규제가 강화되고 있다. 디젤엔진이 장착된 선박 배가스 처리장치 내 SCR 기술이 주목을 받고 있으며, NH₃-SCR에 사용되는 촉매는 주로 VO_x/TiO₂, VO_x/W/TiO₂ 촉매가 대표적이다. 한편 선박 디젤엔진에 사용되는 연료에 따라 연소배가스 특성이 다르다. 이러한 연료가 연소됨에 따라 SO₂, SO₃가 발생되고 환원제인 NH₃와 결합하여 황산암모늄염((NH₄)₂SO₄), ABS (ammonium bisulfate, NH₄HSO₄)과 같은 염을 형성시켜 탈질촉매의 비활성화 문제가 발생된다. 이러한 비활성화 물질이 침적된 탈질촉매를 재활성화 시키기 위하여 열 산화를 통해 재생시키고 있다. 이처럼 선박용 SCR 촉매는 강화되는 배출규제 및 엔진기술의 발달로 저감되는 운전 온도에 대비하여 저온 활성 재생이 가능한 고활성, 고내구성 촉매기술 개발이 필요하다.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.193-198
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• 2015

Ceria supported on various commercial $TiO_2$ catalysts were prepared by wet-impregnation method. We confirmed that the correlation between physicochemical properties of $TiO_2$ supports and SCR activities. Physicochemical properties of the various $TiO_2$ were evaluated using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and pH analysis. Ce/Ti catalyst exhibited different SCR activities with respect to physicochemical properties of $TiO_2$. An excellent activity was obtained as the surface area of $TiO_2$ increased. In the case of CeOx surface density, the excellent activity in a range of $2.5{\sim}14.5CeOx/nm^2$ was achieved and the activity tended to decrease above $14.5CeOx/nm^2$. The O/Ti mole ratio of $TiO_2$ in the range of 1.32 to 1.79 showed an excellent SCR activity. It was also confirmed that the pH of the $TiO_2$ has no effects on the SCR activity. In order to achieve excellent SCR activities, ceria oxide should be supported on $TiO_2$ possessing a high specific surface area and certain O/Ti mole ratio. In addition, the catalyst with the low CeOx surface density resulted from the high dispersed ceria oxide should be prepared.

• Microbiology and Biotechnology Letters
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• v.37 no.4
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• pp.371-376
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• 2009

The fruits of sweet cherry are highly appreciated by the consumer due to their precocity and quality, such as their sweetness, color and sourness. In this study, the hot-water extract and its sequential organic solvent fractions were prepared from domestic Napoleon sweet cherry (Prunus avium L.) to investigate antimicrobial and antioxidant activity. The hot-water extract contained about 40% sugars, and the solvent fraction yields for hexane, ethylacetate (EA), butanol, and water residue were 0.01%, 3.45%, 16.30%, and 80.24%, respectively. Contents of total polyphenol and total flavonoid of the fractions were 1.24~5.24%, and 0~3.76%, respectively. Among the fractions, EA fraction showed the highest total polyphenol and total flavonoid concentrations. Evaluation of antimicrobial activity of the extract and fractions revealed that EA fraction and butanol fraction contained strong antibacterial activity against Listeria monocytogenes, Staphylococcus aureus, and Salmonella typhimurium with minimal inhibitory concentration (MIC) of 0.5~1.0 mg/mL. But the extract and fractions tested were not active to Pseudomonas aeruginosa. In a while, only hexane fraction showed anti-Candida activity with 0.5~1.0 mg/mL of MIC. The fraction showed strong activity against different multi-antibiotics resistant strains such as C. albicans CCARM 14020. Antioxidative activity assay showed that EA fraction has a strong DPPH scavenging activity and a reducing power. The $IC_{50}s$ of vitamin E and EA fraction were 15.5 and $195.5\;{\mu}g/mL$, respectively. Our results suggest that the fruit of P. avium L. has high potentials with anti-Candida and antioxidative activity.

• Journal of Life Science
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• v.25 no.4
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• pp.425-432
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• 2015

This study was performed to develop high-value-added biomaterials for health and beauty products. Extracts of ethanol and hot water and their subsequent organic solvent fractions were prepared from Lees of Wookukseng (LW), a commercialized Korean traditional rice wine. We investigated their activities on blood coagulation, platelet aggregation, hemolysis against human red blood cells (hRBCs), and anti-oxidation. The water content, pH and brix of the LW were 80.3%, 3.94 and 13.0°, respectively. The yield of ethanol extraction (6.62%) was 3.15 times higher than that of hot-water extraction (2.1%), and the ethyacetate fraction (EAF) of ethanol extract showed the highest content of total polyphenol (128 mg/g) among the various fractions. In anticoagulation activity assay, the EAF of ethanol extract showed a 15-fold extension in TT, PT, and aPTT, indicating that the EAFs contain various inhibitory substances against thrombin, prothrombin and coagulation factors. In anti-platelet aggregation activity assay, the butanol fraction and water residue of ethanol extract showed significant inhibition activity. The activities were comparable to aspirin, a commercial anti-thrombosis agent. The above extracts and fractions did not show hemolysis activity against hRBC up to 5 mg/ml, and had radical scavenging activity against DPPH anion, ABTS cation and nitrite. Our results suggest that the active fractions prepared from LW, which has no specific usage until now, have a high potential as novel resources for anti-thrombosis agents.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.42-51
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• 2012

In this paper, injection-locking characteristics versus active layer structures in Fabry-Perot laser diodes (FP-LD) are compared. TE and TM gain spectra and peak gains versus carrier density in polarized and unpolarized multiple quantum well structures and in an unpolarized bulk structure are calculated. The calculated gain parameters are applied to a time-domain large-signal model to simulate the injection-locking characteristics. The results show that RIN in unpolarized FD-LDs is about 3 dB lower than that in a polarized FP-LD and that the eye characteristics of the unpolarized FP-LD are much better than those of the polarized FP-LD.