• 분석과학
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• 제16권4호
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• pp.269-276
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• 2003

새로운 종류의 벗김전압전류법, 즉 전도된 촉매 벗김전압전류법 ($IC_tSV$)을 소개한다. 염산 용액에서 로듐-포름알데히드 착물은 역주사 동안에 환원전류 봉우리 즉 전도된 촉매수소 봉우리가 생긴다. 이 전도된 봉우리의 특징을 조사하고 이 봉우리를 분석 봉우리로 이용하여 결정한 검출한계는 $1.2{\times}10^{-10}M$ (축적시간 50초)이었다. 최적 실험 조건은 0.015% (W/V) HCHO-0.42 M HCl, 농축전위 -1.1 V, 주사속도 100 mV/s이다.

• Carbon letters
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• 제25권
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• pp.33-42
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• 2018

Activated carbon (AC) was modified by ammonium persulphate or nitric acid, respectively. AC and the modified materials were used as catalyst supports. The oxygen groups were introduced in the supports during the modifications. All the supports were characterized by $N_2$-physisorption, Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis. Methanol synthesis catalysts were prepared through wet impregnation of copper nitrate and zinc nitrate on the supports followed by thermal decomposition. These catalysts were measured by the means of $N_2$-physisorption, X-ray diffraction, XPS, temperature programmed reduction and TEM tests. The catalytic performances of the prepared catalysts were compared with a commercial catalyst (CZA) in this work. The results showed that the methanol production rate of AC-CZ ($23mmol-CH_3OH/(g-Cu{\cdot}h)$) was higher, on Cu loading basis, than that of CZA ($9mmol-CH_3OH/(g-Cu{\cdot}h)$). We also found that the modification methods produced strong metal-support interactions leading to poor catalytic performance. AC without any modification can prompt the catalytic performance of the resulted catalyst.

• 한국대기환경학회지
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• 제22권4호
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• pp.431-439
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• 2006

Catalytic oxidation of benzene, toluene and xylene (BTX) using regenerated metal oxide catalysts (ZnO-CuO, NiO, $Fe_2O_3$, ZnO, CrO) were investigated in a fixed bed flow reactor to evaluate their feasibility for the purpose of removing volatile organic compounds (VOCs). Four kinds of pre-treatment methods such as gas (air and hydrogen), acid aqueous solution, alkali aqueous solution and cleaning agent were used to find out the optimal regeneration conditions. The physico-chemical properties of the used and regenerated catalysts were characterized by BET and TPR (Temperature Programmed Reduction). The used catalysts showed high conversion ratio and the catalytic ability of toluene oxidation was in the order of ZnO-CuO>$Fe_2O_3$>NiO>ZnO>CrO. We found that the acid aqueous pre-treatment (0.1 N HNO$_3$) was the best way to enhance the catalytic activity of $Fe_2O_3$. In addition, air and hydrogen gas treatment were optimal for NiO and ZnO-CuO catalysts, respectively. Furthermore, the decomposition of BTX depends on the type of a catalyst and a gas molecule.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.237-240
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• 2002

Micro catalytic reactors are alternative propulsion device that can be used on a nano satellite. When used with a monopropellant, $H_2O_2$, a micro catalytic reactor needs only one supply system as the monopropellant reacts spontaneously on contact with catalyst and releases heat without external ignition, while separate supply lines for fuel and oxidizer are needed for a bipropellant rocket engine. Additionally, $H_2O_2$ is in liquid phase at room temperature, eliminating the burden of storage for gaseous fuel and carburetion of liquid fuel. In order to design a micro catalytic reactor, an appropriate catalyst material must be selected. Considering the safety concern in handling the monopropellants and reaction performance of catalyst, we selected hydrogen peroxide at volume concentration of 70% and perovskite redox catalyst of lantanium cobaltate doped with strondium. Perovskite catalysts are known to have superior reactivity in reduction-oxidation chemical processes. In particular, lantanium cobaltate has better performance in chemical reactions involving oxygen atom exchange than other perovskite materials. In the present study, a process to prepare perovskite type catalyst, $La_{0.8}Sr_{0.2}CoO_3$, and measurement of its propellant decomposition performance in a test reactor are described.

• Applied Microscopy
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• 제46권2호
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• pp.105-109
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• 2016

Palladium has been used as a catalyst not only in Suzuki and Heck cross coupling reaction in organic chemistry, but also in automobile industry for the reduction of vehicle exhausts. The catalytic activity of Pd nanoparticles depends strongly on their size and exposed crystalline facets. In this study, the single crystalline palladium nanocubes/nanorods were prepared in the presence of polyvinyl pyrrolidone (PVP) and potassium bromide (KBr) using the polyol method. Selected area diffraction pattern and high-resolution transmission electron microscopy (TEM) were performed by TEM. The result shows that the ratio of KBr/PVP is the key factor to determine whether the product is cubes or rods. The as-prepared Pd nanocubes were highly uniform in both size and shape. The ordered packing structures including monolayer and multilayer can be fabricated via the rate-controlled evaporation of solution solvent. The catalytic activity of these Pd nanocubes towards heck reaction of iodobenzene with acrylate or acrylic acid was found to be higher than that of Pd nanorods. We suspect it is caused by the difference of energy state while Pd nanocubes is {100} plane and nanorods is {111} plane.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.363-368
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• 2008

Nitrogen oxides (NO, $NO_2$ and $N_2O$) have been controlled effectively by the SCR catalysts coated on monolith or honeycomb in commercial sites with ammonia as reductant at high temperature range $300{\sim}400^{\circ}C$. However, the catalytic filter has much merit on the point of controlling the particles and nitrogen oxides simultaneously. It will be more advanced-system if the catalytic working temperature is reduced to the normal filtration temperature of under $200^{\circ}C$. This study has focus on the development of the catalytic filter working at the low temperature. So the additive effect of the components such as Pt and Mn (which are known the catalytic component of $V_2O_5/TiO_2$ was investigated. The $V_2O_5-WO_3$ catalytic filter exhibited high activity and selectivity at $250{\sim}320^{\circ}C$ showing more than 95% NO conversion for the treatment of 600 ppm NO at face velocity 2 cm/s. The Pt-$V_2O_5-WO_3$ catalytic filter shifted the optimum working temperature towards the lower temperature ($170{\sim}200^{\circ}C$). And NO conversion was 100% and higher than that of $V_2O_5-WO_3$ catalyst at $250{\sim}320^{\circ}C$. The $MnO_X-V_2O_5-WO_3$ catalytic filter showed the wide temperature range of $220{\sim}330^{\circ}C$ for more than 95% NO conversion. This is a remarkable advantage when considered the $MnO_X$ catalytic filter presents the maximum activity at $150{\sim}250^{\circ}C$ and $V_2O_5-WO_3$ catalytic filter shows the maximum activity at $250{\sim}320^{\circ}C$.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.248-254
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• 2006

The promotion effects of noble metals upon the activity and reducibility in steam methane reforming over $Ni/MgAl_2O_4$ catalysts were investigated. While $Ni/MgAl_2O_4$ catalysts require the pre-reduction by $H_2$, the noble metal-added catalysts show high catalytic activities without pre-treatment. According to $CH_4$-TPR, the addition of noble metal makes the $Ni/MgAl_2O_4$ catalyst easily reducible. The reduction degree of NiO in the noble metal-added catalysts after using at $650^{\circ}C$ without pre-reduction was $15{\sim}20%$, and was lower than that in the $H_2$-reduced $Ni/MgAl_2O_4$ catalyst(reduction degree=27%). The enhancement of the catalytic activity over noble metal-added catalysts results from easier reducibility by addition of noble metal and the synergy effect between noble metal and Ni.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2874-2879
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• 2008

The Selective catalytic reduction(SCR) system is a highly-effective device of $NO_x$ reduction for diesel engines. Generally, the ammonia($NH_3$) generated from a liquid urea-water solution is used for the reductant. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency becomes lower, due to temperature window. And space velocity also affects to $NO_x$ conversion efficiency. This paper reviews a laboratory study to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the SCR system. The maximum conversion efficiency of $NO_x$ was indicated when the $NH_3$ to $NO_x$ ratio was 1.2 and the space velocity was $60,000\;h^{-1}$. The results of this paper contribute to improve overall $NO_x$ reduction efficiency and $NH_3$ slip.

• 한국컴퓨터정보학회논문지
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• 제22권1호
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• pp.63-69
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• 2017

In this paper, we propose a method to optimize the geometry and installation position of the mixer in the selective catalytic reduction (SCR) system by computational fluid dynamic(CFD). Using the commercial CFD software of CFD-ACE+, the flow dynamics of the flue gas was numerically analyzed for improving the injection uniformity of the reduction agent. Numerical analysis of the mixed gas heat flow into the upstream side of the primary SCR catalyst layer was performed when the denitrification facility was operated. The characteristics such as the flow rate, temperature, pressure loss and ammonia concentration of the mixed gas consisting of the flue gas and the ammonia reducing gas were examined at the upstream of the catalyst layer of SCR. The temperature difference on the surface of the catalyst layer is very small compared to the flow rate of the exhaust gas, and the temperature difference caused by the reducing gas hardly occurs because the flow rate of the reducing gas is very small. When the mixed gas is introduced into the SCR reactor, there is a slight tendency toward one wall. When the gas passes through the catalyst layer having a large pressure loss, the flow angle of the exhaust gas changes because the direction of the exhaust gas changes toward a smaller flow. Based on the uniformity of the flow rate of the mixed gas calculated at the SCR, it is judged that the position of the test port reflected in the design is proper.

• 한국융합학회논문지
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• 제10권4호
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• pp.131-138
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• 2019

디젤엔진은 열효율이 높고 연비가 좋으며 CO, HC 및 $CO_2$의 배출량이 낮은 등 가솔린 엔진보다 상당한 장점이 있다. 그러나 디젤엔진은 배기가스 중에 $O_2$ 농도가 높기 때문에 NOx 저감이 어렵고, 삼원촉매를 적용하기 어렵다. Urea-SCR과 LNT는 디젤엔진에서 NOx를 연속적으로 저감하는데 활용 가능한 두 기술이다. 디자인 엔진에 Urea-SCR 시스템을 구현함으로써 2.5l 이상 엔진에서 Euro-6의 강화된 NOx 기준을 충족시킬 수 있게 되었다. 본 연구에서는 엔진 회전속도, 부하, 촉매 방식 및 $NH_3$/NOx 비율에 따른 NOx 저감 특성을 연구하여 NOx 저감을 극대화하는 조건을 제시하고자 한다. 또한 Euro-6 이상의 규제에 대응할 수 있도록 Urea-SCR에 대한 정밀한 실험 데이터를 제공하고자 한다.