• 에너지공학
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• 제8권2호
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• pp.256-264
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• 1999

본 연구에서는 메탄의 부분산화반응에 미치는 base metal 의 영향을 살펴보기 위하여 6~l2wt%의 Mn, Cu, V, Co, Cr 그리고 Ba 등이 2 wt% Pt, 70 wt% Alumina, 28 wt% Ceria and Zirconia 와 함께 cordierite (2MgO.2Al$_2$O$_3$.5SiO$_2$)에 담지된 Pt-B/cordierite 촉매(B: base metal)를 사용하여 메탄의 부분산화반응 실험을 수행하였다. 메탄의 부분산화반응에 대한 활성은 Ba, Co그리고 Cr 담지 촉매는 Ni담지 촉매와 유사하게 Mn, Cu, V을 담지 했을 때 보다 우수한 것으로 나타났으나, 코크 생성에 대한 활성도 큰 것으로 나타났다. 또한 5wt% Ni/Al$_2$O$_3$촉매를 이용한 메탄의 부분산화반응 실험 후의 촉매에 대한 XRD 분석결과 Ni은 3가지 형태의 상으로 존재하는 것을 확인할 수 있었으며, 촉매층 전단에서는 주로 NiAl$_2$O$_4$와 NiO 형태로 존재하여 메탄의 산화반응이 일어나며, 그리고 촉매층 후단에서는 환원상태의 Ni로 존재는 것으로 보아 개질반응이 일어나는 것을 알 수 있었다.

• 품질경영학회지
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• 제21권2호
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• pp.242-253
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• 1993

The interpretation of the reaction mechanism is significant to produce the high quality welds and understand the welding processes. This investigation is important for the design of welding consumables and the selection of welding process parameters to develop the high quality welds. The objective of this study is to investigate the effect of electrochemical reactions on the transfer of alloy elements between slag and weld metal during submerged arc welding During submerged arc welding weld metal composition is shown to be controlled by two reaction mechanisms in four reaction zones. The responsible reaction mechanisms are thermochemical and electrochemical reactions. The possible reaction sites are the melted electrode tip, the detached droplet, the hot weld pool immediately below the moving electrode, and the cooling and solidifying weld pool behind the moving electrode. The possible reactions in submerged arc welding at different zones of the process is schematically shown in Figure 1.

• 대한금속재료학회지
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• 제47권3호
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• pp.182-187
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• 2009

The molten salt electrolysis is applied to reduce titanium dioxide to titanium metal using calcium chloride as an electrolyte and the reaction mechanism of the reduction process is examined by analyzing the reaction products. The process conditions to obtain titanium metal for $900^{\circ}C$ correspond to 2.9~3.2 V and 24 hours. The reaction products for 2.9 V at $900^{\circ}C$ include irregular-shaped titanium oxides such as $Ti_4O_7$, $Ti_3O_5$ and $Ti_2O_3$ and polyhedral $CaTiO_3$. Using these microstructure analysis, the sequential reaction mechanism for the electrochemical reduction of titanium dioxide to titanium is proposed.

• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• Korean Chemical Engineering Research
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• 제53권2호
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• pp.262-268
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• 2015

본 연구에서는 일반적인 귀금속 담지법과 담체 위에 형성한 고분자 전해질 다층 박막 내에 귀금속을 내포시키는 방법으로 촉매를 제조하고, 과산화수소 직접제조 반응에 적용하여 촉매의 제조 방법이 과산화수소 생산성 및 촉매 수명에 미치는 영향을 조사하였다. 촉매의 활성은 제조 방법에 상관없이 담체의 산세기에 크게 의존하였으며, 사용한 담체들 중 산세기가 가장 강한 HBEA(SAR=25)를 사용한 경우가 활성이 가장 우수하였다. 단순 귀금속 담지 촉매는 고분자 전해질 다층 박막을 도입한 촉매보다 과산화수소 생산성은 우수하였으나, 반응 중 활성 금속인 Pd의 용출로 인해 재사용 횟수가 증가할 때마다 활성이 급격히 감소하였다. 한편, 고분자 전해질 다층 박막의 도입은 산성 담체의 역할을 약화시켜 촉매 활성은 감소하고 과산화수소 분해능은 증가하여 전체적으로 과산화수소의 생산성이 감소되는 결과를 가져왔다. 하지만, 5회에 걸친 재사용 동안에도 촉매 활성이 유지되었으며, 이러한 비약적인 촉매 수명의 향상은 담체 위에 고분자 전해질 다층 박막을 도입하는 것이 반응 중 활성 금속의 용출 억제 측면에서 매우 효과적이라는 것을 시사한다.

• 한국환경보건학회지
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• 제30권5호
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• pp.358-365
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• 2004

The photocatalytic oxidation of Rhodamine B(RhB) was studied using photocatalytic reactor filled with module of quartz tube. Module of quartz tube consisted of small quartz tube (inner diameter, 1.5 mm; outer diameter, 3 mm) bundle coated with powder $TiO_2$ and uncoated large quartz tube (inner diameter, 20 mm; outer diameter, 22 mm). Two 30 W germicidal lamp was used as the light source and the reactor volume was 0.5 l. The effects of parameters such as the coating materials and numbers, initial concentration, $H_{2}O_2$ dose and metal deposition (Ag, Pt and Fe) and simultaneous application of $H_{2}O_2$ and metal deposition. The results showed that the initial reaction constant of quartz module coated with powder $TiO_2$ was higher 1.4 time than that of the $TiO_2$ sol and optimum coating number is twice. In order to increase reaction rate, simultaneous application of photocatalytic and photo-fenton reaction using Fe coating and dose $H_{2}O_2$ dose increased reaction rate largely.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2483-2487
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• 2010

Pseudo-first-order rate constants ($k_{obsd}$) were measured spectrophotometrically for nucleophilic substitution reactions of 4-nitrophenyl picolinate (6) with alkali metal ethoxides (EtOM, $M^+\;=\;K^+$, $Na^+$ and $Li^+$) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOM] exhibits upward curvature regardless of the nature of $M^+$ ions. However, the plot for the reaction of 6 with EtOK is linear with significantly decreased $k_{obsd}$ values when 18-crown-6-ether (18C6, a complexing agent for $K^+$ ion) is added in the reaction medium. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that ion-paired EtOM is 3~17 times more reactive than dissociated $EtO^-$. The reaction has been proposed to proceed through a 5-membered cyclic transition state, in which $M^+$ ion increases the electrophilicity of the reaction site. Interestingly, $Na^+$ ion exhibits the largest catalytic effect. The presence of a nitrogen atom in the pyridine moiety of 6 has been suggested to be responsible for the high $Na^+$ ion selectivity.

• 한국환경과학회지
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• 제6권5호
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• pp.505-512
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• 1997

The Interfacial characteristics between various heavy metals and hydrous FeS were investigated. Heavy metals which have lower sulfide solubilities than FeS undergoes the lecttice exchange reaction when these metal tons contact FeS In the aqueous phase. For heavy metals which have higher suede solubilities than FeS, these metal ions adsorb on the surface of FeS. Such characteristic reactions were interpreted by the soled solution formation theory. The presence of ligand such as EDTA reduced largely metal removal efficiency due to formation of metal-ligand complex In the solution. In an attempt to elucidate the Interfacial characteristics, zeta potential of the hydrous FeS In the absence and In the presence of various metal loons were measured and analyzed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.129-132
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• 2007

Advanced structure of metal-supported solid oxide fuel cells was devised to overcome sealing problem and mechanical instability in ceramic-supported solid oxide fuel cells. STS430 whose dimensions were 26mm diameter, 1mm thickness and 0.4mm channel width was used as metal support. Thin ceramic layer composed of anode(Ni/YSZ) and electrolyte(YSZ) was joined with STS430 metal support by using a cermet adhesive. $La_{0.8}Sr_{0.2}Co_{0.4}Mn_{0.6}O_{3}$ perovskite oxide was used as cathode material. It was noted that oxygen reduction reaction of cathode governed the overall cell performance from oxygen partial pressure dependance.

• 한국대기환경학회지
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• 제16권4호
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• pp.409-414
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• 2000

Catalytic combustion of acetaldehyde has been investigated as a representative of unpleasant odor by its reaction with metal-phthalocyanines(PC). The experiment was conducted at the reaction temperature of 200~41$0^{\circ}C$ and the concentratio of acetaldehyde in air at the range of 0.07~0.94 mole% The pretreated metal-PC has been characterized by UV-VIS and XRD analysis. According to this study catalytic activity of metal -PC was improved by air pretreatment at 45$0^{\circ}C$ for 1hr. Under this pretreatment condition Co-PC and Cu($\alpha$)-PC were destroyed and new metal oxides were formed such as Co3O4 and CuO respectively. However Zn-PC retained its basic structure even afte air pretreatment. The order of catalytic activity on acetaldehyde combustion was summarized as follows : Zn-PC$\alpha$)-PC. It was found that the complete combustin of acetaldehyde with Cu($\alpha$)-PC was accomplished at its concentrations below 0.2mole% (32$0^{\circ}C$) and 0.6 mole%(35$0^{\circ}C$) in air.