• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.388-400
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• 2021

Power to gas (P2G) is one of the energy storage technologies that can increase the storage period and storage capacity compared to the existing battery type. One of P2G technology produces hydrogen by decomposing water from renewable energy (electricity) and the other produces CH4 by reacting hydrogen with CO2. This study is an experimental study to produce CH4 by reacting CO2 of biogas with hydrogen using a 40 wt% Ni-Mg-Al catalyst and a commercial catalyst. Catalyst characteristics were analyzed through H2-TPR, XRD, and XPS instruments of 40% Ni catalyst and commercial catalyst. The effect on the CO2 conversion rate and CH4 selectivity was analyzed, and the activities of a 40% Ni catalyst and a commercial catalyst were compared. As a result of experiment, In the case of a 40 wt% catalyst, the maximum CO2 conversion rate showed 77% at the reaction temperature of 400℃. Meanwhile, the commercial catalyst showed a maximum CO2 conversion rate of 60% at 450℃. When 50% of CO was added to the CO2 methanation reaction, the CO2 conversion rate was increased by about 5%. This is considered to be due to the atmosphere in which the CO reaction can occur without the process of converting to CH4 after forming carbon and CO as intermediates in terms of the CO2 mechanism on the catalyst surface.

• 한국환경과학회지
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• 제5권5호
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• pp.569-577
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• 1996

과잉수소 반응조건하에서 사염화탄소의 열적 안정성과 수첨탈염소화 과정을 고찰하기 위한 모델로써 Cl/H의 비가 다른 순수 염화메탄화합물인 메틸염소, 메틸렌염소, 클로로포름과 사염화탄소를 이용하였다. 반응시간 1초에서 99% 분해되는 온도를 기준으로한 열적 안정성은 메틸염소는 $875^{\circ}C,$ 메틸렌염소는 $780^{\circ}C,$ 클로로포름은 $675^{\circ}C,$ 사염화탄소는 $635^{\circ}C$ 이었으며, 낮은 반응온도영역에서는 클로로포름의 열적 안정성이 사염화탄소보다 낮았으나 온도가 증가함에 따라 사염화탄소의 분해가 증가하여 $570^{\circ}C$ 이상에서는 클로로포름보다 쉽게 분해되었다. 사염화탄소의 분해 반응계에서의 생성물 고찰결과, 반응온도가 증가함에 따라 염화탄화수소 화합물 계열 생성물의 농도와 염화정도가 감소하였다. 과잉수소 반응조건에서 사염화탄소 열분해 실험결과, $850^{\circ}C$ 이상에서는 탈염소화 탄화수소화합물인 메탄, 에틸렌, 에탄의 생성물의 농도가 증가하였으며 염소화 합물로는 메틸염소만이 소량 검출되었다. 이는 염화정도가 낮은 화합물일수록 열적 안정성이 크다는 것을 의미하며 CCl4/H2 반응계에서 염화탄소화합물중 메틸염소가 열적 안정성이 가장 큰 화합물이었다.

• 한국응용과학기술학회지
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• 제30권1호
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• pp.166-172
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• 2013

본 연구는 압연공정에서 발생하는 폐수 중에 함유되어있는 난분해성 COD 물질을 $80{\mu}m$ 두께의 극세사 형태로 제조된 Cu-Zn 금속합금의 산화 작용으로 인하여 발생하는 OH 라디칼을 이용하여 처리하는 방법에 관한 기초 연구이다. OH 라디칼은 유기화합물(RH) 속에 포함된 수소를 수소추출반응(H Abstraction) 또는 탄소와 탄소(C-C)의 불포화 결합에 첨가됨으로써 빠르고 비 선택적인 반응을 수행하는 것으로 알려진 것처럼 난 분해성 유기화합물의 처리에 효과적인 것으로 나타났다. 금속합금 반응 물질은 극세사 형태로 표면적이 넓어서 1회 처리만으로도 수용액의 pH를 평형에 도달하게 하여서 반응 효율성이 높은 것으로 나타났다. COD처리 효율은 중성 pH에 가까운 pH 7, pH 6에서 최고치를 보였으며 산성분위기인 pH 5이하 및 알칼리성 분위기인 pH 8이상에서는 낮은 효율을 보였다. 실제 압연 폐수의 응집 침전을 이용한 COD 처리에서도 redox 반응장치의 유무에 따라 2배 이상의 처리효율의 차이를 보였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1995년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.25-25
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• 1995

Liquid phase sintering of 90W-6Ni-4Mn alloy has been investigated as functions of sintering atmosphere, heating rate, and reduction temperature. The present work accounts for the thermodynamic oxidatiodreduction reactions of constituent powders of W, Ni and Mn. By discounting these reactions, the previous investigations would obtain only the alloy with large pores and the lowered relative sintered density, by the liquid phase sintering under a dry hydrogen atmosphere. the sintering cycle consisted of a rapid heating to reduction temperatures under high purity nitrogen atmosphere, and holding for 4 hours and sintering at $1260^{\circ}C$ for 1 hour under a dry hydrogen gas. The relative density of the sintered alloy increased with increasing heating rate. As the reduction temperature increased, the relative density increased to the lm theotical density at the duction temture above $1150^{\circ}C$. The mimsturcatre of sintered alloys has been analysed by a scanning election microscope. The sintered density was compared with those obtained from the other investigators. It was found that the reduction $1150^{\circ}C$ results in the lowered densification of 90W-6Ni-4Mn alloy. This is caused by the fact that reducing reactions of W and Ni oxides contained in W an Ni powders concomitantly leads to oxidizing reaction of Mn powder the oxidized Mn is hardly reduced at sintering temperature and thereby remains large pores in the alloy. It is concluded that the W-Ni-Mn alloy with full density can be obtained by the precise control of atmosphere, heating rate, and sintering temperature.

• 한국분말재료학회지
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• 제25권3호
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• pp.240-245
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• 2018

This study focuses on the fabrication of a WC/Co composite powder from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere for the recycling of WC/Co hardmetal. Mixed powders are manufactured by mechanically milling the oxide powder of WC-13 wt% Co hardmetal scrap and carbon black with varying powder/ball weight ratios. The oxide powder of WC-13 wt% Co hardmetal scrap consists of $WO_3$ and $CoWO_4$. The mixed powder mechanically milled at a lower powder/ball weight ratio (high mechanical milling energy) has a more rapid carbothermal reduction reaction in the formation of WC and Co phases compared with that mechanically milled at a higher powder/ball weight ratio (lower mechanical milling energy). The WC/Co composite powder is fabricated at $900^{\circ}C$ for 6 h from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere. The fabricated WC/Co composite powder has a particle size of approximately $0.25-0.5{\mu}m$.

• Asian Journal of Atmospheric Environment
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• 제9권2호
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• pp.158-164
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• 2015

The estimation of the concentration of hydroxyl radical (OH) in the atmosphere is essential to build atmospheric models and to understand the mechanisms of the reactions involved in OH. Although water vapor is one of the most abundant species in the troposphere, only a few studies have been performed for the reaction of OH and water vapor. Here I demonstrate an ab initio study on the complex forming reation of OH with $H_2O$ in the gas phase performed based on density functional theory to calculate the reaction rate and the energy states of the reactant and the OH-$H_2O$ complex. The structure of the complex, which belongs to the Cs point group, was optimized at global minima. The transition state was not found at the B3LYP and MP2 levels of theory. Rate constants of the forward and the reverse reactions were calculated as $1.1{\times}10^{-16}cm^3\;molecule^{-1}\;s^{-1}$ and $5.3{\times}10^9\;s^{-1}$, respectively. The extremely slow rates of complex forming reaction and the resulting hydrogen atom exchange reaction of OH and $H_2O$, which are consistent with experimentally determined values, imply a negligible possibility of a change in OH reactivity through the title reaction.

• Korean Chemical Engineering Research
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• 제58권4호
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• pp.658-664
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• 2020

Zeolite HY is wet impregnated with Ni (0.1, 0.3, 0.4, 0.5 wt%), Pt (0.1 wt%) and reduced in presence of hydrogen to form nanosized particles of Ni and Pt. All the catalysts were characterized by XRD, TEM, ESCA, NH₃-TPD, Pyridine adsorbed FT-IR and BET. Characterization results confirm that the Ni and Pt fractions effectively rehabilitated the physio-chemical properties of the zeolite HY catalysts. Further, all the reduced catalyst were screened with hydroisomerization of m-xylene at LHSV = 2.0 h^-1 in the temperature range 250-400 ℃ in steps of 50 ℃ in hydrogen atmosphere (20 ml/g). The addition of Ni to Pt catalyst increases hydroisomerization conversion, as well as maximizes p-xylene selectivity by restricting the pore size. The increasing trend in activity continues up to 0.3 wt% of Ni and 0.1 wt% Pt addition over zeolite HY. The increasing addition of Ni increases the total number of active metallic sites to exposed, which increases the metallic sites/acid sites ratio towards the optimum value for these reactions by better balance of synergic effect for stable activity. The rate of deactivation is pronounced on monometallic catalysts. The results confirm the threshold Ni addition is highly suitable for hydroisomerization reaction for product selectivity over Ni-Pt bimetallic/support catalysts.

• 한국수소및신에너지학회논문집
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• 제10권2호
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• pp.131-139
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• 1999

The objective of this works was to synthesize the$Mg_2Ni$ hydrogen storage materials economically and to eliminate the intial activation process. $Mg_2NiH_x$ was mechanically alloyed under purified hydrogen gas atmosphere using pure Mg and Ni chips. M.A(Mechanical Alloying) was carried out using planetary ball mill for times varying from 12h to 96h under 20bars of hydrogen gas pressure. $Mg_2NiH_x$ started to form after 48h and the homogeneous $Mg_2NiH_x$ composites was synthesized after 96h. From TG analysis, the dehydriding reaction of $Mg_2NiH_x$ started at around $200^{\circ}C$. The result of P-C-T at $300^{\circ}C$ revealed the hydrogen storage capacity of $Mg_2NiH_c$ reached 3.68 wt% and the effective hydrogen storage was 2.38 wt%. The enthalpy difference of absorption-desorption cycling for the hydride formation and the hysteresis were reduced and the plateau flatness and the sloping were improved according to M.A time.

• 한국미생물·생명공학회지
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• 제11권3호
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• pp.211-216
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• 1983

R. sphaeroides K- 7에 의한 수소생성과 질소고정효소(nitrogenase)와의 연관성을 조사한 결과 수소생성은 질소고정효소에 의해 이루어지는 것으로 나타났다. 또한 수소생성은 수소효소(hydrogenase)와 무관하며 박테리오클로로필의 농도와도 무관한 것으로 나타났다. 글루타민산이 in vivo에서 질소고정효소의 활성도를 조절하는데 중요한 역할을 할 수 있는 것으로 나타났으며 질소개스를 이용해 키운 세균을 글루타민산 존재하로 옮겼을때 보다 큰 정도의 수소생성능 및 질소고정효소 활성도가 나타났다.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.167-171
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• 2004

The electroless deposition of copper on the hydrogen-terminated Si(111) surface was investigated by means of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning tunneling microscopy (STM), and energy-dispersive spectroscopy (EDS). The hydrogen-terminated Si(111) surface prepared was stable under air atmosphere for a day or more. It was found from ATR-FTIR that two bands centered at 2000 and 2260 $cm^{-1}$ appeared after the H-Si(111) surface was immersed in 40% $NH_4F$ solution containing 10 mM $Cu^{2+}$. On the other hand, STM image included the copper islands with a height of 5 nm and a diameter of 10-20 nm. The EDS data displayed the presence of copper, silicon and oxygen species. The results were rationalized in terms of the redox reaction of surface Si atoms and $Cu^{2+}$ ions in solutions, which are changed into $Si(OH)_x(F)_y$ containing $SiF_6^{2-}$ ions and neutral copper islands.