Exposure to nitrogen dioxide (NO₂) can produce adverse health effects. Various indoor and outdoor combustion sources make NO₂ the most ubiquitous pollutant in the indoor environment. Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. In the present paper, we used a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements with 10 houses. Subsequently, mean contributions of indoor and outdoor sources were 28.86% and 81.09%, respectively, suggesting that both indoor and outdoor sources had contributions to indoor concentrations of NO₂.

Indoor air quality can be affected by indoor sources, ventilation, outdoor levels, and removal. Various indoor and outdoor combustion sources make nitrogen dioxide(NO2), which is a by-product of high temperature fossil fuel combustion. Especially, the presence of gas ranges and smoking have been identified as two of the major factors contributing to indoor NO2 exposures. In this study, the relative efficiencies for NO2 removal by a large number of materials are presented. This work has demonstrated that reactions with indoor surfaces represents a significant sink for NO2, and that these reactions currently are effecting a considerable degree of control over indoor NO2 levels. It seems that this control could be enhanced by judicious selection of furnishings and construction materials. Improved understanding of that rates and mechanisms of the removal process will permit optimization of the process for indoor air quality improvement.

Burning mosquito coils in indoor environments maygenerate smoke that can control mosquito effectively. This practice has been used in numerous households in Korea. However the smoke may contain air pollutants of health concern. We conducted the present study to characterize the emission from two common brands of mosquito coils from Vietnam and Malaysia, respectively. We measured mass emission of air pollutants of nitrogen oxides (NOx), fine particulate(PM2.5), formaldehyde (HCHO), total volatile organic compounds (TVOCs), carbon monoxide (CO) and carbon dioxide (CO2) in completely closed chamber. Air pollutants concentrations resulting from burning mosquito coils could substantially exceed health-based air quality standards orguidelines. Under the same condition, air pollutants were measured by cigarette smoking to compare mosquito coil. Burning one mosquito coil would release the same amount of PM2.5 mass as burning 20~58 cigarettes. The emission of HCHO from burning one coil can be as high as that released from burning 27 cigarettes.

본 연구에서는 광촉매 반응과 막분리 기술을 접목시킨 혼성 고도 정수처리 공정에서 소독 부산물의 전구체로 알려진 자연산 유기물을 효과적으로 제거하고자 하였고 다양한 운전 조건에서 시스템의 성능을 비교 평가하였다. 자연산 유기물은 흡입여과 방식의 분리막과 TiO2 광촉매를 이용하여 광분해하였을 때 광촉매 투입량의 증가에 따라 반응속도가 증가하였지만 과량의 촉매 주입시에는 반응 속도 향상에 오히려 부정적으로 작용하였다. 자연산 유기물을 보다 효과적으로 제거하기 위해 산화철 주입, TiO2 표면처리, 분리막 표면코팅을 시도하여 제거특성 및 운전에 따른 막여과 특성을 평가하였다. 산화철 주입은 초기에 흡착작용으로 인해 제거율 증가를 보였으나 반응이 진행됨에 따라 산화철 입자에 의한 광산란으로 광분해 효율이 오히려 감소되었다. 산화철 입자에 의한 광산란을 제어하고자 TiO2 표면을 광처리와 열처리 방법을 이용해 철을 직접 부착시킨 경우 긍정적인 효과를 얻지 못했다. 그러나 산화철로 막표면을 코팅하여 광산란 효과를 배제시킨 경우에는 향상된 결과를 보였다 막투과 플럭스 15 L/m2-h에서 정밀여과를 수행하였을 때 TiO2나 산화철에 의한 막오염은 거의 일어나지 않았고 안정된 막투과도를 나타내었다.

외연적 유한요소법은 벡터처리에 적합한 구조를 가지고 있어 벡터컴퓨터를 이용하면 기존의 스칼라 컴퓨터에서보다 휠씬 빠르게 해석을 수행할 수 있다. 본 논문에서는 memory-to-memory방식의 벡터컴퓨터에서의 외연적 유한요소법의 효율적인 벡터화 방법을 제시하였다. 먼저 벡터컴퓨터의 구조적 특성과 무관하게 적용될 수 있는 일반적인 벡터화 기법을 고찰한 후 memory-to-memory방식의 벡터컴퓨터에 적합한 벡터화 기법을 개발하였다. 개발된 벡터화 기법의 유용성을 확인하기 위해 외연적 유한요소 프로그램인 DYNA3D를 memory-to-memory방식의 벡터컴퓨터인 HDS AS/XL V50에 이식한 결과 스칼라에 비해 2.4배 이상의 성능 향상을 얻을 수 있었다.

Combustion of ethanol (EtOH) at low temperatures has been studied using titania- and silica-supported platinum nanocrystallites with different sizes in a wide range of 1~25 nm, to see if EtOH can be used as a clean, alternative fuel, i.e., one that does not emit sulfur oxides, fine particulates and nitrogen oxides, and if the combustion flue gas can be used for directly heating the interior of greenhouses. The results of H2-N2O titration on the supported Pt catalysts with no calcination indicate a metal dispersion of 0.97±0.1, corresponding to ca. 1.2 nm, while the calcination of 0.65% Pt/SiO2 at 600 and 900℃ gives the respective sizes of 13.7 and 24.6 nm when using X-ray diffraction technique, as expected. A comparison of EtOH combustion using Pt/TiO2 and Pt/SiO2 catalysts with the same metal content, dispersion and nanoparticle size discloses that the former is better at all temperatures up to 200℃, suggesting that some acid sites can play a role for the combustion. There is a noticeable difference in the combustion characteristics of EtOH at 80~200℃ between samples of 0.65% Pt/SiO2 consisting of different metal particle sizes; the catalyst with larger platinum nanoparticles shows higher intrinsic activity. Besides the formation of CO2, low-temperature combustion of EtOH can lead to many other pathways that generate undesired byproducts, such as formaldehyde, acetaldehyde, acetic acid, diethyl ether, and ethylene, depending strongly on the catalyst and reaction conditions. A 0.65% Pt/SiO2 catalyst with a Pt crystallite size of 24.6 nm shows stable performances in EtOH combustion at 120℃ even for 12 h, regardless of the space velocity allowed.

Adsorption using highly porous and highly functionalized sorbents is a straightforward removal technology currently being employed, however the range of contaminants is limited. A novel sorbent was synthesized from activated carbon and Zr-based UiO66 metal organic framework to remove both cationic and oxyanionic metals from aqueous solutions. The composite was characterized using FSEM-EDS, FT-IR, XRD, and TGA, and showed successful integration of UiO66 on the surface of activated carbon. Batch adsorption tests with ICP-OES reveal that the composite has removal efficiency >95% for Pb (II), Cu (II), Se (IV), and As (V). The hybrid material is a promising sorbent for the removal of both cationic and oxyanionic metals for wastewater purification.

Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of CO2 as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of CO2 adsorption at given conditions and those points have been extensively described with literature data. A great body of data of CO2 adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better CO2 adsorbent for PSA processes.

Titania-supported chromium oxides with different loadings have been embarked in catalytic oxidation of trichloroethylene (TCE) to inquire association of the formation of crystalline Cr2O3 with catalytic performances. A better activity in the oxidative TCE decomposition at chosen temperatures was represented when chromium oxides (CrOx) had been dispersed on pure anatase-type TiO2 (DT51D) rather than on phase-mixed and sulfur-contained ones such as P25 and DT51. The extent of TCE oxidation at temperatures below 350℃ was a strong function of CrOx content in CrOx/DT51D TiO2, and a noticeable point was that the catalyst has two optimal CrOx loadings in which the lowest T50 and T90 values were measured for the TCE oxidation. This behavior in the activity with respect to CrOx amounts could be associated with the formation of crystalline Cr2O3 on the support surface, that is less active for the oxidation reaction, and an easier mobility of the surface oxygen existing in noncrystalline CrOx species with higher oxidation states, such as Cr2O8 and CrO3.

폐기물을 이용한 재활용제품은 자원의 절약과 재활용촉진에 관한 법률에 폐목제 고형연료(WCF), 폐플라스틱 고형연료(RPF), 폐타이어 고형연료(TDF), 생활폐기물 고형연료(RDF)로 규정되어 있다. 이중에서 폐플라스틱 고형연료(RDF)의 저위발열량은 6,000 kcal/kg 이상으로 명시되어 있다. 폐플라스틱 고형연료(RDF)의 제조과정에서 발생되는 잔류물은 일부가 공정으로 재투입되기도 하지만 경제성과 공정의 효율적인 운영을 이유로 대부분 폐기처분되고 있다. 이렇게 폐기처분되는 폐플라스틱 고형연료(RDF) 잔류물이 보유하고 있는 물리 화학적 에너지는 생활폐기물과 비교해도 손색이 없을 정도이다. 본 연구에서는 두 종류의 폐플라스틱 고형연료(RDF) 잔류물을 이용하여 운전 조건별로 생산되는 합성가스의 특성을 비교하였다. 실험에 사용된 폐기물 시료의 습윤 저위발열량은 각각 5,228 kcal/kg, 4,454 kcal/kg으로 분석되었다. 운전 조건으로는 폐기물 투입속도, 등가비(Φ), 반응영역의 온도이며 조건별로 Test #1부터 #3까지 구분하였다. 실험 결과 합성가스 조성(CO+H2)은 56.3% ~ 63.1%, 합성가스 유량은 124.2 Nm³/h ~ 138.8 Nm³/h, 냉가스효율은 57.4% ~ 63.9%로 나타났다. 등가비가 증가할수록 합성가스의 조성이 증가하였으며 반응영역의 온도가 감소하는 것으로 분석되었다.

가스화는 산소가 불충분한 상태에서 폐기물, 바이오매스와 같은 원료물질에 열을 가하여 가연성 가스(합성가스)로 발생시키는 열화학적 전환 공정이다. 합성가스는 주로 CO, H₂ 성분이 혼합되어있다. 중･소규모의 폐기물, 바이오매스 가스화 시스템은 합성가스를 생산하여 열과 전기를 생산하는데 이용한다. 그러나 천연가스나 석탄을 이용한 합성가스 생산 공정에서는 이미 고부가가치의 액체 연료를 생산하는 공정이 상업운전 중에 있다. 국내에서도 납사 및 중유 가스화를 통해 합성가스를 생산하여 초산, 수소 등의 고부가가치 물질을 생산 중에 있다. 본 연구에서는 초산 제조공정에서 원료물질로 이용하는 CO를 폐기물 가스화를 통한 합성가스 내의 CO로 대체하고자 하는 시스템을 개발하고자 한다. 고정층 방식의 가스화 용융로에 U지역 사업장 폐기물을 원료물질로 하고 산화제는 산소를 이용하여 가스화 실험을 실시하였다. 수분 14.6%, 가연분 58.4%, 회분 27.0%, 저위발열량 3,158 kcal/kg의 특성을 가지는 U지역 사업장 폐기물을 이용한 결과 합성가스의 CO+H₂의 농도가 60% 이상 안정적으로 생산되는 것을 확인할 수 있어, 가연성 가스를 고부가가치 화학원료로 이용할 수 있을 것으로 판단되었다

The present work has been devoted to the catalytic reduction of N2O by H2 with Pt/SiO2 catalysts at very low temperatures, such as 110oC, and their nanoparticle sizes have been determined by using H2-N2O titration, X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) measurements. A sample of 1.72% Pt/SiO2, which had been prepared by an ion exchange method, consisted of almost atomic levels of Pt nanoparticles with 1.16 nm that are very consistent with the HRTEM measurements, while a Pt/SiO2 catalyst possessing the same Pt amount via an incipient wetness technique did 13.5 nm particles as determined by the XRD measurements. These two catalysts showed a noticeable difference in the on-stream deN2O activity maintenance profiles at 110℃. This discrepancy was associated with the nanoparticle sizes, i.e., the Pt/SiO2 catalyst with the smaller particle size was much more active for the N2O reduction. When repeated measurements of the N2O reduction with the 1.16 nm Pt catalyst at 110oC were allowed, the catalyst deactivation occurred, depending somewhat on regeneration excursions.

A unit emission reduction of nitrous oxide (N2O) from anthropogenic sources is equivalent to a 310-unit CO2 emission reduction because the N2O has the global warming potential (GWP) of 310. This greatly promoted very active development and commercialization of catalysts to control N2O emissions from large-scale stationary sources, representatively nitric acid production plants, and numerous catalytic systems have been proposed for the N2O reduction to date and here designated to Options A to C with respect to in-duct-application scenarios. Whether or not these Options are suitable for N2O emissions control in nitric acid industries is primarily determined by positions of them being operated in nitric acid plants, which is mainly due to the difference in gas temperatures, compositions and pressures. The Option A being installed in the NH3 oxidation reactor requires catalysts that have very strong thermal stability and high selectivity, while the Option B technologies are operated between the NO2 absorption column and the gas expander and catalysts with medium thermal stability, good water tolerance and strong hydrothermal stability are applicable for this option. Catalysts for the Option C, that is positioned after the gas expander thereby having the lowest gas temperatures and pressure, should possess high deN2O performance and excellent water tolerance under such conditions. Consequently, each deN2O technology has different opportunities in nitric acid production plants and the best solution needs to be chosen considering the process requirements.

Nitrous oxide (N2O) is one of six greenhouse gases listed up in the Kyoto Protocol, and it effects a strong global warming because of its much greater global warming potential (GWP), by 310 times over a 100-year time horizon, than CO2. Although such N2O emissions from both natural and anthropogenic sources occur, the latter can be controlled using suitable abatement technologies, depending on them, to reduce N2O below acceptable or feasible levels. This paper has extensively reviewed the anthropogenic N2O emission sources and their related compositions, and the state-of-the-art non-catalytic and catalytic technologies of the emissions controls available currently to representative, large N2O emission sources, such as adipic acid production plants. Challengeable approaches to this source are discussed to promote establishment of advanced N2O emission control technologies.

TiO2- and SiO2-supported Co3O4, Pt and Co3O4-Pt catalysts have been studied for CO and C3H8 oxidations at temperatures less than 250℃ which is a lower limit of light-off temperatures to oxidize them during emission test cycles of gasoline-fueled automotives with TWCs (three-way catalytic converters) consisting mainly of Pt, Pd and Rh. All the catalysts after appropriate activation such as calcination at 350℃ and reduction at 400℃ exhibited significant dependence on both their preparation techniques and supports upon CO oxidation at chosen temperatures. A Pt/TiO2 catalyst prepared by using an ion-exchange method (IE) has much better activity for such CO oxidation because of smaller Pt nanoparticles, compared to a supported Pt obtained via an incipient wetness (IW). Supported Co3O4-only catalysts are very active for CO oxidation even at 100℃, but the use of TiO2 as a support and the IW technique give the best performances. These effects on supports and preparation methods were indicated for Co3O4-Pt catalysts. Based on activity profiles of CO oxidation at 100℃ over a physical mixture of supported Pt and Co3O4 after activation under different conditions, and typical light-off temperatures of CO and unburned hydrocarbons in common TWCs as tested for C3H8 oxidation at 250℃ with a Pt-exchanged SiO2 catalyst, this study may offer an useful approach to substitute Co3O4 for a part of platinum group metals, particularly Pt, thereby lowering the usage of the precious metals.

The Kyoto Protocol, that had been in force from February 16, 2005, requires significant reduction in CO₂emissions for all anthropogenic sources containing transportation, industrial, commercial, and residential fields, etc, and automotive emission standards for air pollutants such as particulate matter (PM) and nitrogen oxides (NOx) become more and more tight for improving ambient air quality. This paper has briefly reviewed homogeneous charge compression ignition (HCCI) combustion technology offering dramatic reduction in CO₂, NOx and PM emissions, compared to conventional gasoline and diesel engine vehicles, in an effort of automotive industries and their related academic activities to comply with future fuel economy legislation, e.g., CO₂emission standards and corporate average fuel economy (CAFE) in the respective European Union (EU) and United States of America (USA), and to meet very stringent future automotive emission standards, e.g., Tier 2 program in USA and EURO V in EU. In addition, major challenges to the widespread use of HCCI engines in road applications are discussed in aspects of new catalytic emissions controls to remove high CO and unburned hydrocarbons from such engine-equipped vehicles.

The formation of ConTiOn+₂ compounds, i.e., CoTiO₃ and Co2TiO₄, in a 5 wt% CoOx/TiO2 catalyst after calcination at different temperatures has been characterized via scanning electron microscopy (SEM), Raman and X-ray photoelectron spectroscopy (XPS) measurements to verify our earlier model associated with Co3O4 nanoparticles present in the catalyst, and laboratory-synthesized ConTiOn+₂ chemicals have been employed to directly measure their activity profiles for CO oxidation at 100˚C. SEM measurements with the synthetic CoTiO₃ and Co2TiO₄ gave the respective tetragonal and rhombohedral morphology structures, in good agreement with the earlier XRD results. Weak Raman peaks at 239, 267 and 336 cm-1 appeared on 5 wt% CoOx/TiO₂ after calcination at 570oC but not on the catalyst calcined at 450˚C, and these peaks were observed for the ConTiOn+₂ compounds, particularly CoTiO3. All samples of the two cobalt titanate possessed O 1s XPS spectra comprised of strong peaks at 530.0±0.1 eV with a shoulder at a 532.2-eV binding energy. The O 1s structure at binding energies near 530.0 eV was shown for a sample of 5 wt% CoOx/TiO₂, irrespective to calcination temperature. The noticeable difference between the catalyst calcined at 450 and 570˚C is the 532.2 eV shoulder which was indicative of the formation of the ConTiOn+₂ compounds in the catalyst. No long-life activity maintenance of the synthetic ConTiOn+₂ compounds for CO oxidation at 100˚C was a good vehicle to strongly support the reason why the supported CoOx catalyst after calcination at 570˚C had been practically inactive for the oxidation reaction in our previous study; consequently, the earlier proposed model for the Co₃O₄ nanoparticles existing with the catalyst following calcination at different temperatures is very consistent with the characterization results and activity measurements with the cobalt titanates.