수소는 반도체, 수소화 반응, 연료전지 등 다양한 산업 공정에 사용될 뿐만 아니라 높은 에너지 밀도를 가져 미래의 에너지 원으로 각광 받는다. Water Gas Shift(WGS)와 같은 일반적인 수소제조 공정에서 수소 뿐만 아니라 일산화탄소, 이산화탄소 메탄과 같은 불순물들이 포함되며, 농축 및 정제의 필요성이 있다. Pd 수소분리막을 이용한 수소 분리공정은 수소만을 선택적으로 분리하여 99% 이상의 순도를 쉽게 얻을 수 있다. 본 연구에서는 상전이법을 통하여 중공사형 알루미나 지지체를 제조하고, 무전해 도금법을 이용하여 Pd를 코팅하였다. 무전해 도금법을 이용하여 제조한 분리막을 SEM, EDS, XRD 등의 분석을 통하여 특성을 파악하였으며, 온도 및 압력에 따른 수소 분리실험을 진행 하였다. 본 연구는 “교육부 기본연구(NRF-2017R1D1A1B03036250)”의 지원으로 수행되었습니다.

Perfluorinated sulfonic acid (PFSA) ionomers have been used as polymer electrolyte membrane (PEM) materials owing to their excellent chemical durability and proton conductivity. However, the PFSA ionomers are suffering from fast hydrogen crossover and, thereby, chemical degradation in the membrane state. To solve these issues is to make reinforced membranes by filling proton-conductive PFSA ionomers in the pores of chemically robust poly(tetrafluoroethylene) (PTFE) support films. However, it is very difficult to obtain PFSA-PTFE reinforced membranes with improved hydrogen barrier property. In this study, PFSA-PTFE reinforced membranes were fabricated by immersing commercial reinforced membrane in PFSA ionomer dispersions with different chemical architectures and particle sizes and their effects were systematically investigated.

본 총설은 분리막기술이 적용된 수소생산에 대한 개론으로, 특히, 암모니아를 수소운반체로 이용하는 수소생산에 대한 연구결과를 중점적으로 서술하였다. 암모니아를 수소운반체로 적용한 수소생산은 추가적인 탄소생성이 없다는 점 외에 여러 측면에 있어 이점이 있다. 많은 연구들이 고순도 수소 분리 및 생산을 위한 분리막 개발을 위해 진행되고 있으며, 이들 중 팔라듐을 기본으로 한 분리막(예를 들어, 다공성 세라믹 또는 다공성 금속 지지체와 팔라듐 합금의 얇은 선택층으로 이루어진 분리막)에 대한 연구가 활발하다. 반면에, 효율적인 암모니아 분해를 위해서는 주로 루테늄 촉매가 적용되고 있으며, 루테늄과 지지체 및 촉진제로 이루어진 루테늄에 기반을 둔 촉매에 대한 연구발표가 다수 존재한다. 수소생산을 위한 분리막 반응기 형태로는 충전층, 유동층, 그리고 마이크로반응기 등이 있으며, 이들의 최적화 및 원활한 물질전달 연구는 현재진행형 이다. 또한, 높은 암모니아 분해율, 고순도 수소생산 및 높은 수소생산율을 얻기 위해 분리막과 촉매의 다양한 조합에 대한 연구 및 분리막과 촉매의 역할을 동시에 구현할 수 있는 분리막에 대한 연구가 발표되고 있다.

고온에서 진행되는 프로판 탈수소 반응에서 촉매의 불활성화의 주된 원인은 코크 침적, 소결현상이 있다. 이러한 불활성화를 줄이는 촉매를 연구하기 위해, 본 연구에서는 열적 안정성이 높은 MgAl2O4를 담체로 적용하여 프로판 탈수소 반응용 촉매로의 활용성을 확인하고자 하였다. Alcohthermal method로 MgAl2O4를 소성온도 800, 900, 1000℃로 달리하여 제조하였고, Pt와 Sn을 공동함침법으로 담지하여 Pt-Sn/MgAl2O4촉매를 제조하였다. 열적안정성의 확인을 위해 반응온도를 고온의 650, 600℃에서 진행하였다. 반응실험 결과 반응온도에 상관없이 담체의 소성온도가 800℃인 담체적용 촉매일 때 프로판 탈수소 반응 실험의 전환율과 수율이 담체소성온도가 900,1000℃인 담체적용 촉매보다 높은 것을 확인하였고, 반응온도가 고온인 650℃일 때는 Pt-Sn/θ-Al2O3보다도 더 높은 수율을 가지는 것을 볼 수 있었다. 특성분석으로는 TGA, BET, XRD, CO-화학흡착, SEM-EDS 분석을 실시하였다. MgAl2O4-800oC가 좋은 수율과 Pt분산도 및 적은 불활성화 정도의 관계를 서로 연관 지어 확인하였다.

바이오항공유 제조 공정 내 수첨업그레이딩 공정의 운전조건 선정은 반응물로부터 얻고자 하는 주생성물인 탄화수소 화합물에 대하여 바이오항공유로서 원하는 탄소수 분포의 물성을 갖도록 하기 위한 중요한 인자이다. 본 연구에서는 식물성 오일 유래 노말 파라핀계 탄화수소 화합물에 대한 수첨 업그레이딩 반응이 0.5 wt.% Pt/Zeolite 촉매 하에서 수행되었으며, 이를 통해 크래킹 반응과 이성질화 반응이 동반됨으로써 바이오항공유로서 물성을 갖는 탄소수 분포인 C8-C16에 해당하는 노말 파라핀계와 이소 파라핀계가 혼합된 탄화수소류 화합물이 제조되었다. 반응온도, 반응압력, 반응물 몰비와 공간속도를 변화하여 얻어진 생성물의 수율 및 조성을 분석하였다. 상기 공정 조건에 대한 정보는 수첨 업그레이딩 반응특성의 이해뿐 아니라 향후 증류를 통한 바이오항공유 제조에 도움을 줄 수 있다.

A lab-scale biofilter with fungal growth has been studied to investigate the removal of gas-phase hydrogen sulfide. The biofilter inoculated initially with the aerobic activated sludge was operated for 100 days under acidic condition, and 0.36 L/d of the buffered nutrient with 0.05 g/L Chloramphenicol and Gentamicin was injected into the biofilter. The critical removal capacity of hydrogen sulfide was up to 22 g/m³/h. The pH of the effluent liquid was stable at pH 1.5-2, corresponding to the volatile suspended solids of 20-50 mg/L. In microbial analysis through the plate count method, it was found that fungi were dominant over bacteria. The fungi isolated from biomass in the bilfilter were identified as Acidomyces acidophilus and Aspergillus fumigatus. Sulfate and thiosulfate were also detected in liquid samples, as a result of the biological sulfur oxidation in the biofilter bed. For the analysis of sulfur mass balance, the accumulated mass of sulfate and thiosulfate reached up to 67.5% of inlet sulfur. Sulfur was also detected on the biomass collected from the biofilter through Scanning electron microscopy/Energy dispersive X-ray spectroscopy.

Nickel oxide(NiO) thin films, nanorods, and carbon nanotube(CNT)/NiO core-shell nanorod structures are fabricated by sputtering Nickel at different deposition time on alumina substrates or single wall carbon nanotube templates followed by oxidation treatments at different temperatures, 400 and 700 oC. Structural analyses are carried out by scanning electron microscopy and x-ray diffraction. NiO thinfilm, nanorod and CNT/NiO core-shell nanorod structurals of the gas sensor structures are tested for detection of H2S gas. The NiO structures exhibit the highest response at 200 oC and high selectivity to H2S among other gases of NO, NH3, H2, CO, etc. The nanorod structures have a higher sensing performance than the thin films and carbon nanotube/NiO core-shell structures. The gold catalyst deposited on NiO nanorods further improve the sensing performance, particularly the recovery kinetics.

The hydrogen reduction behavior of MoO3-CuO powder mixture for the synthesis of homogeneous Mo-20 wt% Cu composite powder is investigated. The reduction behavior of ball-milled powder mixture is analyzed by XRD and temperature programmed reduction method at various heating rates in Ar-10% H2 atmosphere. The XRD analysis of the heat-treated powder at 300oC shows Cu, MoO3, and Cu2MoO5 phases. In contrast, the powder mixture heated at 400oC is composed of Cu and MoO2 phases. The hydrogen reduction kinetic is evaluated by the amount of peak shift with heating rates. The activation energies for the reduction, estimated by the slope of the Kissinger plot, are measured as 112.2 kJ/mol and 65.2 kJ/mol, depending on the reduction steps from CuO to Cu and from MoO3 to MoO2, respectively. The measured activation energy for the reduction of MoO3 is explained by the effect of pre-reduced Cu particles. The powder mixture, hydrogen-reduced at 700oC, shows the dispersion of nano-sized Cu agglomerates on the surface of Mo powders.

Since the so-called diesel gates of German automobiles, interest in environmentally-friendly vehicles has been rising, among other alternatives, hydrogen-fueled electric vehicles with 0% vehicle emissions are expected to replace a significant portion of passenger cars. Here, we analyze trends of US, Europe, PCT (WO) 3-patent offices application of hydrogen-fueled electric vehicles and analyze the patent application trends of national and individual companies, the patent application trend of detailed technology through clustering analysis, technology competitiveness. The global market for hydrogen-fueled electric vehicles, which is currently only 0.01% of other alternatives, is expected to grow to several percent in 2020. Major automobile makers such as Japan, United States of America, Germany, and Korea continue to fiercely compete for eco-friendly vehicles.

Hydrogen evolution on a steel surface and subsequent hydrogen diffusion into the steel matrix are evaluated using an electrochemical permeation test with no applied cathodic current on the hydrogen charging side. In particular, cyclic operation in the permeation test is also conducted to clarify the corrosion-induced hydrogen evolution behavior. In contrast to the conventional perception that the cathodic reduction reaction on the steel in neutral aqueous environments is an oxygen reduction reaction, this study demonstrates that atomic hydrogen may be generated on the steel surface by the corrosion reaction, even in a neutral environment. Although a much lower permeation current density and significant slower diffusion kinetics of hydrogen are observed compared to the results measured in acidic environments, they contribute to the increase in the embrittlement index. This study suggests that the research on hydrogen embrittlement in ultra-strong steels should be approached from the viewpoint of corrosion reactions on the steel surface and subsequent hydrogen evolution/diffusion behavior.

We report a method for preparing rare earth oxides (RexOy) from the recycling process for spent Ni-metal hydride (Ni-MH) batteries. This process first involves a leaching of spent Ni-MH powders with sulfuric acid at 90℃, resulting in rare earth precipitates (i.e., NaRE(SO4)2·H2O, RE = La, Ce, Nd), which are converted into rare earth oxides via two different approaches: i) simple heat treatment in air, and ii) metathesis reaction with NaOH at 70℃. Not only the morphological features but also the crystallographic structures of all products are systematically investigated using field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD); their thermal behaviors are also analyzed. In particular, XRD results show that some of the rare earth precipitates are converted into oxide form (such as La2O3, Ce2O3, and Nd2O3) with heat treatment at 1200℃; however, secondary peaks are also observed. On the other hand, rare earth oxides, RExOy can be successfully obtained after metathesis of rare earth precipitates, followed by heat treatment at 1000℃ in air, along with a change of crystallographic structures, i.e., NaRE(SO4)2·H2O → RE(OH)3 → RExOy.

Acidic and basic mixtures of odorous compounds are commonly emitted from various sources, and, in an absorption process, pH conditions in the liquid phase significantly affect the performance. In this study, the effect of pH on mass transfer in a bubble column reactor was evaluated using hydrogen sulfide and ammonia as a model mixture. Their mass transfer coefficients were then calculated. Furthermore, the total mass transfer coefficients as a function of pH were evaluated, and the experimental data were fitted into an empirical equation using dimensionless numbers. The mass transfer rates of hydrogen sulfide, the non-ionic form, increased dramatically with increasing pHs, while those of ammonia were almost unchanged because of its high solubility. As a result, a favorable pH condition for less soluble compounds must be selected to achieve high absorption capacity. The total mass transfer rates, which took into account pH effects as well as all the non-ionic and ionic constituents together, were found to be from 2.2 to 2.4 × 10−3 min−1 for hydrogen sulfide and ammonia, respectively, and they were almost constant at different pHs. The empirical equations, which were derived to obtain the best fit for the total mass transfer rates, implied that a method to increase diffusivity of each compound should be applied to improve overall mass transfer. In addition, when using the empirical equation, a mass transfer coefficient at a given set of pH and operating conditions can be calculated and used to design a water scrubbing process.

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

수소원자는 금속 표면에 흡착하여 해리되고 금속 격자 사이를 이동해 다시 수소분자로 재결합되어 탈착할 수 있으며 이러한 과정으로 수소는 금속을 통해 투과할 수 있다. 특히 수소원자는 팔라듐에서 높은 용해도와 이동도를 보이기 때문에 우수한 수소 투과 특성을 나타낸다. 본 연구에서는 무전해 도금을 이용하여 Pd 금속을 α-Al2O3 중공사 지지체에 증착시켜 SEM&EDS 분석을 통해 Pd 코팅 특성을 확인하였다. 치밀 Pd 층을 확인하기 위한 분리막의 leak 테스트 후 고온 수소투과 실험을 통해 분리막의 수소투과특성을 확인하였다. 본 연구는 “교육부 기본연구(NRF-2017R1D1A1B03036250)”의 지원으로 수행되었습니다.

수소를 연료로 사용하는 PEMFC는 고효율⋅출력밀도를 나타내며, 짧은 시동시간, 우수한 응답특성에 따라 현지설치형 발전기술로 사용되며, 이를 위한 고효율 연료처리장치가 필수적이다. SMR반응은 연료당 고회수율을 때문에 경제성이 우수하며, 전환율 확보를 위해 700°C, 20 bar 이상의 운전조건에서 수행되며, WGS, PSA의 후단공정을 통해 수소를 생산한다. 분리막 개질기를 이용한 SMR반응은 분리막이 수소를 제거함에 따라 반응효율 증진, 공정온도 저감, 후단공정 배제를 할 수 있어 공정구성 및 경제성이 우수하다. 본 연구에서는 팔라듐분리막 개질기를 사용하여 550°C, 5 bar에서 SMR반응을 통해 수소를 생산하였으며, 개질된 가스의 CO 농도를 최소화하여 고온 PEMFC용 연료처리장치를 개발하였다.