Hyo-Sub Kim

Improvement of lifetime using transition metal-incorporated SAPO-34 catalysts in conversion of dimethyl ether to light olefins

Transition metal (Mn, Fe, or Ni) incorporated SAPO-34 (MeAPSO-34) nanocatalysts were synthesized using a hydrothermal method to improve the catalytic lifetime in the conversion of dimethyl ether to light olefins (DTO). The structures of the synthesized catalysts were characterized using several methods including XRD, SEM, BET, 29Si-MAS NMR, and NH3-TPD techniques. Although the structure of the MeAPSO-34 catalysts was similar to that of the SAPO-34 catalyst, the amount of weak acid sites in all MeAPSO-34 catalysts was markedly increased and accompanied by differences in crystallinity and structural arrangement. The amount of weak acid sites decreased in the following order: NiAPSO-34 > FeAPSO-34 >MnAPSO-34 > SAPO-34 catalyst. The MeAPSO-34 catalysts, when used in the DTO reaction, maintained DME conversion above 90% for a longer time than the SAPO- 34 catalyst, while also maintaining the total selectivity above 95% for light olefins. In addition, the NiAPSO-34 catalyst showed the longest catalytic lifetime; the lifetime was extended approximately 2-fold relative to the SAPO-34 catalyst. Therefore, the increase in the catalytic lifetime is related to the amount of weak acidic sites, and these sites are increased in number by incorporating transition metals into the SAPO-34 catalyst.

Preparation of the Anti-Reflective(AR) Coating Film by Sol-Gel Method to Improve the Efficiency of Solar Cell

2 Spawn Korea, 1337 Gwanpyeong-dong Yuseong-gu Daejeon, 305-509, Korea Abstract >> This study investigates the preparation of anti-reflective (AR) coating film to improve the efficiency of solar cell. The AR coating film was successfully obtained by dip-coating with AR coatings prepared by sol-gel method. Fluoroalkylsilane was additionally introduced into the coatings to give the self-cleaning effect of AR coating film. We performed the abrasion test, pencil scratch hardness test and cross-cut test to identify the mechanical strength of AR coating film. As the results, the transmittance of AR coating films with 9.07, 18.13 and 27.20 of IPA/MTMS molar ratios were 93.1, 93.6 and 95.3%, respectively. The water contact angle and transmittance of AR coating film increased by the introduction of hydrophobicity. The prepared AR coating film shows the high level of abrasion, hardness and adhesion. The IPA/MTMS molar ratio of 27.20 and the withdrawing speed range of 0.20 ~ 0.28cm/sec are the optimal coating condition in terms of the transmittance and mechanical strength of AR coating film.

Hydrogen storage and release properties of a Cu-added Fe/YSZ redox system

Hydrogen storage and release by the redox reaction of an iron oxide with yttria-stabilized zirconia (YSZ) were investigated. YSZ was introduced to the samples to improve the thermal stability of the iron oxide. The average size of the samples synthesized using urea was 40-50 nm, whereas those synthesized using Na2CO3 as a precipitant were 150-200 nm. The sample prepared via coprecipitation using urea exhibited better stability than the other samples. We prepared the Cu-added Fe/YSZ sample to enhance the lowtemperature reactivity. The water-splitting reaction was initiated at approximately 200°C, and the maximum rate of hydrogen evolution was observed at approximately 350°C. In the isothermal redox test over 35 cycles, the degree of hydrogen storage and release was almost maintained over 1.8wt% based on the total amount of the sample.

The Effect of SO 2 -O 2 Mixture Gas on Phase Separation Composition of Bunsen Reaction with HI x solution

The Sulfur-Iodine (SI) thermochemical hydrogen production process is one of the most promising thermochemical water splitting technologies. In the integrated operation of the SI process, the produced from a decomposition section could be supplied directly to the Bunsen reaction section without preliminary separation. A () solution could be also provided as the reactants in a Bunsen reaction section, since the sole separation of in a solution recycled from a HI decomposition section was very difficult. Therefore, the Bunsen reaction using mixture gases in the presence of the solution was carried out to identify the effect of . The amount of unreacted under the feed of mixture gases was little higher than that under the feed of gas only, and the amount of HI produced was relatively decreased. The in mixture gases also played a role to decrease the amount of a impurity in phase by only striping effect, while that in phase was hardly affected.

Effects of Process Variables on the Growth of Dendrite in the Electrochemical Alane(AlH 3 ) Production Process

Abstract >> Electrochemical alane (AlH 3 ) production process can be provided as a synthesis route which closea reversible cycle. In this study, growth inhibition of dendrite as key issues in this process was investigated. Maincause of dendrite growth was because Al fine powder separated in consumption process of Al electrode was movedto Pd electrode. In an effort to avoid this, use of glass block with uniform holes was the most effective to inhibitthe amount of dendrite to that of AlH 3 . Furthermore, effects of Al electrode (anode) type and electrolyte concentrationwere investigated and the optimal condition for inhibiting dendrite formation was proposed.Key words : Hydrogen storage(수소 저장), Alane(알레인), Electrochemical(전기화학), Dendrite(덴드라이트) † Corresponding author : yh_kim@cnu.ac.kr Received: 2015.11.3 in revised form: 2015.11.29 Accepted: 2015.12.30Copyright ⓒ 2015 KHNES 1. 서 론 수소 저장 물질로서 알레인 (Alane, Aluminum hydride, AlH 3 )을 이용하는 알레인-연료전지 시스템의 에너지 밀도는 50%의 효율을 가정할 때 1200 Wh/L와 850 Wh/kg 의 용량을 갖는다. 이 값은 전형적인 리튬 전지의 에너지 밀도인 300 Wh/L (150 Wh/kg)보다 약 4배 이상의 높은 용량이다. 따라서 알레인-연료전지 시스템은 수소-연료전지 자동차를 포함하여 다양한 분야에 적용할 수 있는 미래 에너지 저장 시스템으로 전망되고 있다