• 청정기술
• /
• 제16권1호
• /
• pp.12-18
• /
• 2010

본 연구의 목적은 산화탈황 공정의 부산물인 dibenzothiophene sulfone의 분해반응용 KF/MgO 촉매를 개발하는 것이다. MgO 지지체에 KF를 담지시켜 KF/MgO 촉매를 제조하였다. KF 담지량 및 소성 효과 등이 촉매 특성에 미치는 영향을 BET표면적, XRF, XRD, 이산화탄소 승온탈착 실험 등을 통해서 분석하였다. Dibenzothiophene sulfone을 biphenyl 과 이산화황으로 분해하는 반응에서의 촉매 특성을 조사하였다. MgO 촉매에 KF를 담지하면 DBTS 분해반응 활성이 증가하였다. KF/MgO 촉매를 제조하여 373 K에서 건조과정만 거친 촉매의 활성이 고온에서 소성을 거친 촉매의 활성보다 높았으며, 이는 fluoride 이온 ($F^-$)이 염기도를 증가시키는 역할을 하기 때문으로 판단된다. KF를 10 wt% 담지한 촉매가 dibenzothiophene sulfone 분해 반응에서 가장 뛰어난 활성을 보였다.

• 공업화학
• /
• 제23권3호
• /
• pp.344-347
• /
• 2012

본 연구에서는 기존 MgO의 염기세기를 증가시켜 전이에스테르화 반응에 있어 보다 좋은 활성을 가지는 촉매를 만들고자 하였다. MgO를 실험실에서 제조한 후 지지체로 사용하였으며 염기세기를 증가시키기 위하여 KF를 함침법으로 담지하였다. BET, XRD, XRF, $CO_2$ TPO로 촉매의 특성분석을 하였고, 대두유과 메탄올을 사용하여 바이오디젤을 합성한 후 지방산메틸에스테르 함유량을 측정함으로써 촉매의 활성을 알아보았다. 결과적으로, KF를 30% 담지한 촉매가 활성이 가장 좋은 것으로 나타났다. 이는 전이에스테르화 반응에서 중간세기 염기도가 더 많이 관여하기 때문으로 보인다.

• 한국재료학회지
• /
• 제27권9호
• /
• pp.495-500
• /
• 2017

Oxide layers were formed by an environmentally friendly plasma electrolytic oxidation (PEO) process on AZ91 Mg alloy. PEO treatment also resulted in strong adhesion between the oxide layer and the substrate. The influence of the KF electrolytic solution and the structure, composition, microstructure, and micro-hardness properties of the oxide layer were investigated. It was found that the addition of KF instead of KOH to the $Na_2SiO_3$ electrolytic solution increased the electrical conductivity. The oxide layers were mainly composed of MgO and $Mg_2SiO_4$ phases. The oxide layers exhibited solidification particles and pancake-shaped oxide melting. The pore size and surface roughness of the oxide layer decreased considerably with an increase in the concentration of KF, while densification of the oxide layers increased. It is shown that the addition of KF to the basis electrolyte resulted in fabricating of an oxide layer with higher surface hardness and smoother surface roughness on Mg alloys by the PEO process. The uniform thickness of the oxide layer formed on the Mg alloy substrates was largely determined by the electrolytic solution with KF, which suggests that the composition of the electrolytic solution is one of the key factors controlling the uniform thickness of the oxide layer.

• 한국재료학회지
• /
• 제29권10호
• /
• pp.609-616
• /
• 2019

Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of $NaAlO_2$, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and $MgAl_2O_4$ phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.

• 한국수소및신에너지학회논문집
• /
• 제25권6호
• /
• pp.570-576
• /
• 2014

LFG (Land-Fill Gas) includes components of $CH_4$, $CO_2$, $O_2$, $N_2$, and water. The preparation of synthesis gas from LFG as a DME (Dimethyl Ether) feedstock was studied by methane reforming of $CO_2$, $O_2$ and steam over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Our experiments were performed to investigate the effects of methane conversion and syngas ratio on the amount of LFG components over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Results were obtained through the activity reaction experiments at the temperature of $900^{\circ}C$ and GHSV of 4,000. The results were as following; it has generally shown that methane conversion rate increased with the increase of oxygen and carbon dioxide amounts. Highly methane conversion of 92~93% and syngas ratio of approximately 1.0 were obtained in the feed of gas composition flow-rate of 243ml/min of $CH_4$, 241ml/min of $CO_2$, 195ml/min of $O_2$, 48ml/min of $N_2$, and 360ml/min of water, respectively, under reactor pressure of 15 bar for 50 hrs of reaction time. Also, it was shown that catalyst deactivation by coke formation was reduced by excessively adding oxygen and steam as an oxidizer of the methane reforming.

• 한국세라믹학회지
• /
• 제17권2호
• /
• pp.61-68
• /
• 1980

The effect of the addition of various fluoreides on the mullitization of Korean crude kaolin was studied by X-ray powder diffraction and scanning electron microscopic methods. Kaolin without any addition of fluoreides began to be transformed into the mullite at 1, 10$0^{\circ}C$. Mullite peaks were discernible in the X-ray diffraction patterns of the specimens which contained fluorides equivalent to about 2 wt % fluorine, and which were sintered at 1, 05$0^{\circ}C$. The higher the concentration of fluorine in kaolin, the lower was the initiatinig temperature of mullitization. Experiments , for example, showed that mullite could be formed at 95$0^{\circ}C$ from kaolin mixed with 3.4% fluorine. Of the fluoride, addtives, sodiumsiliconfluoride $(Na_2SiF_6)$ was must effective in mullite formation of kaolin. In order of accelerating mullitization, the fluorides except $Na_2SiF_6$ could be placed in following sequence ; (1) sodium (NaF) (2) aluminium$(AlF_3)$ (3)potassium(KF) (4) ammonium$(NH_4F)$ (5) magnesium$(MgF_2)$ (6) calcium$(CaF_2)$. It was considered that the intrinsic characteristics of fluorides, such as size of ionic radiu, charge , bond strength between cation and anion, and electronegativity of cation affected millitization of halloysite, a main constituent mineral of kaolin.