• 한국자동차공학회논문집
• /
• 제11권3호
• /
• pp.71-76
• /
• 2003

A numerical simulation of selective catalytic reduction (SCR) for NO with $NH_3$ is conducted over the $V_2O_5/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The governing $NH_3$ and NO transport equations are considered by using the time-dependent FCT (Flux-Corrected Transport) algorithm. After a validating simulation for $NH_3$ step feed and shut-off experiments is analyzed, transient behavior of $NH_3$ and NO concentration in a SCR catalyst is investigated by changing such parameters as inflow $NH_3$ concentration, temperature of the catalyst, and $NH_3$/NOx ratios.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.29.1-29.1
• /
• 2011

The selective catalytic reduction (SCR) of $MnO_x$ with $NH_3$ is an effective method for the removal of $MnO_x$ from stationary system. The typical catalyst for this method is $V_2O_5-WO_3(MoO_3)/TiO_2$, caused by the high activity and stability. However, This catalyst is active within $300{\sim}400^{\circ}C$ and occurs the pore plugging from the deposition of ammonium sulfate salts on the catalysts surface. It needs to locate the SCR unit after the desulfurizer and electrostatic precipitator without reheating of the flue gas as well as deposition of dust on the catalyst. The manganese oxides supported on titania catalysts have attracted interest because of its high SCR activity at low temperature. The catalytic activity of $MnO_x/TiO_2$ SCR catalyst with different manganese precursors have investigated for low-temperature SCR in terms of structural, morphological, and physico-chemical analyses. The $MnO_x/TiO_2$ were prepared from three different precursors such as manganese nitrate, manganese acetate (II), and manganese acetate (III) by the sol-gel method and then it calcinated at $500^{\circ}C$ for 2 hr. The structural analysis was carried out to identify the phase transition and the change intensity of catalytic activity by various manganese precursors was analyzed by FT-IR and Raman spectroscopy. These different precursors also led to various surface Mn concentrations indicated by SEM. The Mn acetate (III) tends to be more suppressive the crystalline phase (rutile), and it has not only smaller particle size, but also better distributed than the others. It was confirmed that the catalytic activity of MA (III)-$MnO_x/TiO_2$ was the highest among them.

• Korean Chemical Engineering Research
• /
• 제52권5호
• /
• pp.688-693
• /
• 2014

촉매필터의 NO 환원활성을 조사하기 위하여 $SO_2$와 $H_2O$가 동시 또는 따로 존재하는 조건에서 NO, $NH_3$, air로 구성된 합성가스 분위기에서 그 성능이 측정되었다. 집진성능이 높이 평가된 SiC 세라믹 필터의 기공에 $V_2O_5-WO_3/TiO_2$ 촉매를 코팅하여 SCR용 촉매필터를 제작하였다. $260^{\circ}C$ 이하의 저온영역에서 반응가스 중에 $SO_2$와 $H_2O$가 각각 또는 동시에 존재할 경우에 이들이 존재하지 않을 때와 비교하여 촉매필터의 활성이 두드러지게 감소하였다. 반면에 $320^{\circ}C$ 이상의 고온에서는 반응가스 중에 $SO_2$가 포함될 경우 촉매필터의 활성이 증가하여 여과속도 2 cm/s에서 500 ppm의 NO를 99.8% 이상 질소로 환원시켰다. 특히 반응가스 중에 물이 존재할 때는 $380^{\circ}C$의 고온까지 99% 이상의 NO 전환율이 유지되었다. 이와 같은 물의 영향은 물이 고온에서 $NH_3$ 산화반응을 둔화시켜서 $N_2O$ 생성으로 가는 반응을 억제시키기 때문으로 해석되었다. $SO_2$와 $H_2O$가 공존하는 반응가스에서 100시간 운전 후에도 촉매필터의 초기 NO 환원활성이 유지되었다. 따라서 촉매필터가 분진과 NOx 가스를 동시에 처리할 수 있는 우수한 산업촉매로써 활용될 수 있을 것으로 사료되었다.

• 센서학회지
• /
• 제6권6호
• /
• pp.476-482
• /
• 1997

주성분 분석 및 역전달 인공 신경망의 패턴 인식 기법과 산화물 반도체 가스센서 어레이를 사용한 소형 전자코 시스템을 제작하여 그 특성을 평가하였다. 센서 어레이로서 Pd가 첨가된 $WO_{3}$, Pt가 첨가된 $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$가 첨가된 $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$가 첨가된 후 Pd 코팅층이 형성된 $SnO_{2}$, $Al_{2}O_{3}$가 첨가된 ZnO 및 $PdCl_{2}$가 첨가된 $SnO_{2}$ 등의 6가지 조성의 감지재료가 사용되었다. 전자코 시스템 하드웨어는 CPU로서 16bit의 Intel 80c196kc, 시스템 동작 프로그램의 저장을 위한 EPROM, 인공 신경망의 최적화된 가중치의 다운로딩을 위한 EEPROM, 가스농도의 결과 표시를 위한 LCD 등으로 구성하였다. 시스템의 성능 평가를 위해 자동차에서 배출되는 환경오염 물질인 CO/HC 가스(CO 0%/HC 0 ppm 에서 CO 7.6%/HC 400 ppm 까지 범위의 26가지 CO/HC 혼합가스 패턴)에 대한 인식 실험 결과 우수한 특성을 얻을 수 있었다.

• 센서학회지
• /
• 제23권1호
• /
• pp.15-18
• /
• 2014

We present gas sensing performance based on $2{\times}2$ sensor array with four different elements ($TiO_2$, $SnO_2$, $WO_3$ and $In_2O_3$ thin films) fabricated by rf sputter. Each thin film was deposited onto the selected $SiO_2$/Si substrate with Pt interdigitated electrodes (IDEs) of $5{\mu}m$ spacing which were fabricated on a $SiO_2$/Si substrate using photolithography and dry etching. For 5 ppm $NO_2$ and 50 ppm CO, each thin film sensor has a different response to offers the distinguishable response pattern for different gas molecules. Compared with the conventional micro-fabrication technology, $2{\times}2$ sensor array with such remarkable response pattern will be open a new foundation for monolithic integration of high-performance chemoresistive sensors with simplicity in fabrication, low cost, high reliablity, and multifunctional smart sensors for environmental monitoring.

• Bulletin of the Korean Chemical Society
• /
• 제30권3호
• /
• pp.630-635
• /
• 2009

For use as a photocatalyst, bismuth tungsten oxide, $Bi_2WO_6$, was successfully synthesized by hydrothermal treatment at pH = 11 and heating at 200 ${^{\circ}C}$ for 24h, and samples were subsequently thermal treated at 400, 600, and 800 ${^{\circ}C}$ to increase crystallinity. TEM results revealed that the initial untreated particles were sheet‐shaped, grain size was below 80 nm, and it increased with treated temperatures. These $Bi_2WO_6$ samples absorbed at around 400 nm in the visible light range and the intensity of absorption was particularly strongest in samples thermal treated at 600 ${^{\circ}C}$. Their photoluminescence abilities, related to the recombination between the excited electrons and holes, were overall small for other general photocatalysts such as TiO2, and the smallest in the case of thermal treatment at 600 ${^{\circ}C}$, as reversible result of UV‐visible absorbance. Methyl orange of 5.0 ppm aqueous solution was almost completely removed after 2 h when treated over the $Bi_2WO_6$ thermal treated at 600 ${^{\circ}C}$.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.352-353
• /
• 2006

The effect of TiC content on oxidation behavior of the sintered WC-TiC-TaC alloys with 2 mass% TaC and different TiC amounts of 3-45 mass% was investigated through oxidation tests in air at 973K. As a result of the tests, it was revealed that with increasing TiC content in the alloys, mass changes caused by oxidation and thickness of the scale decreased. Thus, it is considered that the main component of the scales changed gradually from $WO_3$ to $TiO_2$ with increasing TiC content in the alloys, and oxygen diffusion through the scale to the alloys was inhibited gradually.

• Korean Journal of Chemical Engineering
• /
• 제35권12호
• /
• pp.2365-2378
• /
• 2018

We investigated the correlation between vanadium surface density and VOx structure species in the selective catalytic reduction of NOx by $NH_3$. The properties of the $VOx/TiO_2$ catalysts were investigated using physicochemical measurements, including BET, XRD, Raman spectroscopy, FE-TEM, UV-visible DRS, $NH_3-TPD$, $H_2-TPR$, $O_2-On/Off$. Catalysts were prepared using the wet impregnation method by supporting 1.0-3.0 wt% vanadium on $TiO_2$ thermally treated at various calcination temperatures. Through the above analysis, we found that VOx surface density was $3.4VOx/nm^2$, and the optimal V loading amounts were 2.0-2.5 wt% and the specific surface area was $65-80m^2/g$. In addition, it was confirmed that the optimal VOx surface density and formation of vanadium structure species correlated with the reaction activity depending on the V loading amounts and the specific surface area size.

• 한국전기전자재료학회논문지
• /
• 제28권5호
• /
• pp.300-305
• /
• 2015

$WO_3$, $SiO_2$, and $TiO_2$ films with hydrophilic property are deposited by rf-magnetron sputtering. Their wettability is strongly depends on the presence or absence of the oxygen plasma etching on the glass substrates. The $TiO_2$ film of 50 nm-thick on the plasma etched glass shows a water contact angle (WCA) below $5^{\circ}$ which means a super-hydrophilic surface. However, WCA values are gradually degraded when the films are exposed under atmosphere, especially $WO_3$. In order to improve hydrophilic property, the degraded films can be again recovered by UV illumination for 10 sec using UV-light and the $TiO_2$ film shows a super-hydrophilic surface about $3^{\circ}$.

• 한국산업보건학회지
• /
• 제26권2호
• /
• pp.119-138
• /
• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.