• Bulletin of the Korean Chemical Society
• /
• v.23 no.8
• /
• pp.1149-1153
• /
• 2002

CH4/CO2 dry reforming was carried out to make syn gas on the Ni/Al2O3 catalysts calcined at different temperatures. The Ni/Al2O3 (850 $^{\circ}C)$ catalyst gave good activity and stability w hereas the Ni/Al2O3 $(450^{\circ}C)$ catalyst showed lower activity and stability. The NiO/Al2O3 catalyst calcined at $850^{\circ}C$ for 16 h (Ni/Al2O3 $(850^{\circ}C))$ formed the spinel structure of nickel aluminate, which was confirmed by TPR. The carbon formation rate on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was very low till 20 h, and then steeply increased with reaction time without decreasing the activity for CH4 reforming. The Ni/Al2O3 $(450^{\circ}C)$ catalyst showed high carbon formation rate at the initial reaction time and then, the rate nearly stopped with continuous decreasing the activity for CH4 reforming. Even though the amount of carbon deposition on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was higher than that on the Ni/Al2O3 $(450^{\circ}C)$ catalyst, the activity for CH4ing was also high, which could be attributed to the different type of the carbon formed on the catalyst surface.

• Journal of Hydrogen and New Energy
• /
• v.21 no.5
• /
• pp.412-418
• /
• 2010

Steam reforming of n-hexadecane, a major component of diesel over Ni-based hydrotalcite-like catalyst was carried out at $900^{\circ}C$ at atmospheric pressure with space velocity of $10,000h^{-1}$ and feed molar ratio of steam/carbon=3.0. Ni-based hydrotalcite catalyst was prepared by a solid phase crystallization (spc) method and characterized by $N_2$-physisorption, CO chemisorption, TPR., XRD, and TEM techniques. It was found that spc Ni/MgAl catalyst showed higher catalytic stability and inhibition of carbon formation than Ni/$\gamma-Al_2O_3$ catalyst under the tested conditions. The results suggest that the modified spc-Ni/MgAl catalyst after optimization may be applied for the SR reaction of diesel.

• Journal of Hydrogen and New Energy
• /
• v.17 no.2
• /
• pp.166-173
• /
• 2006

Catalytic reforming of $CO_2$ by $CH_4$ over Ni-YSZ based catalysts was investigated to produce syngas as raw material of high valued chemicals and develop high performance catalyst electrode for an internal reforming of $CO_2$ in SOFC system. Ni-YSZ based catalysts were prepared using physical mixing and maleic acid methods to improve catalytic activity and inhibition of carbon deposition. The catalysts before and after the reaction were characterized by $N_2$ physisorption, TPR(temperature programed reduction), XRD and impedance analyzer. The conversions for $CO_2$ and $CH_4$ over Ni-MgO catalyst showed 90% but much amount of carbon deposition was detected on catalyst surface. On the other hand, the conversions for $CO_2$ and $CH_4$ over NiO-YSZ-$CeO_2$ catalyst showed 100% and 85% respectively, and carbon deposition on catalyst surface was inhibited under the tested condition. It was concluded that NiO-YSZ-$CeO_2$ catalyst is a promising candidate for the catalytic reforming of $CO_2$ and the internal reforming in SOFC system.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.155-155
• /
• 2011

용융탄산염 연료전지(MCFC)는 $650^{\circ}C$에서 작동하는 고온형 연료전지 시스템이다. 이 시스템은 천연가스 등을 개질하여 생산된 수소를 바로 전기로 생산할 수 있는 시스템으로 열효율이 높으며, 현재 대체 발전시스템으로 각광을 받고 있다. MCFC는 개질방식에 따라 내부개질 방식과 외부개질 방식이 있다. 내부개질 방식은 수소를 생산하는 개질기가 스택내부에 장착된 형식으로 천연가스를 스택내부에서 개질하여 바로 전기를 생산하는 방식이다. 이 내부개질반응에 사용되는 촉매로는 알루미나에 고함량 (약 50 wt.%)으로 담지된 니켈(Ni) 계열촉매이 주로 쓰이고 있다. 이 고함량으로 담지된 촉매는 대부분 높은 활성을 보인다. 비교적 낮은 온도 운전조건 (약 $580{\sim}620^{\circ}C$)을 가지는 MCFC 내부개질에 적용하기 위해서는 활성점인 니켈을 최대한 담지체에 고르게 분산 시켜야한다. 이를 위해서 MgO를 이용하여 촉매의 활성점을 높게 분산시키는 연구를 진행 하였다. 촉매를 제조하는 방법으로 요소(urea)를 이용한 균일용액침전법을 이용하였다. 니켈함량은 50 wt.%로 고정을 한 다음, MgO 양과 $Al_2O_3$ 양을 각각 0 ~ 45 wt.%와 5 ~ 50 wt.%로 조절하면서 촉매를 제조하여 그 특성들을 분석하였다. 물성을 비교하기 위해서, X-선 회절분석 (XRD) 및 TPR, 물리화학흡착 실험을 하였다. 촉매의 활성을 살펴보기 위해서, fresh 상태 및 피독 상태에서 메탄수증기 개질활성 실험을 실시하였다. MgO 함량이 없거나 적은 촉매에서는 높은 BET surface area와 작은 NiO, metallic Ni 결정 크기가 나타났다. 반면 MgO 함량이 높은 촉매에서 낮은 BET surface area와 비교적 큰 NiO, metallic Ni 결정 크기가 나타났다. 또한 XRD 분석에서 MgO 함량이 증가할 수 록 MgO 결정 피크가 명확히 나타났으며, $MgAl_2O_4$ 피크는 나타나지 않았다. TPR 분석에서 촉매들의 환원 피크를 측정한 결과, 저함량의 MgO를 포함한 촉매는 $700^{\circ}C$ 부근에 환원 피크가 관찰되었고 MgO가 고함량인 촉매는 환원 피크가 $400^{\circ}C$ 부근에서 관찰되었다. 촉매의 초기 fresh 상태에서의 활성은 고함량 MgO를 포함한 Ni-90M10A 샘플을 제외하고 모든 촉매가 거의 비슷하게 나타났다. 그러나 $K_2CO_3$ 피독 상태에서는 MgO 함량이 증가할 수 록 활성이 좋지 않았음을 알 수 있었다. 따라서 MgO가 소량 포함된 촉매의 경우 fresh 상태에서는 우수한 물성과 활성을 보이지만, 피독상태에서는 MgO가 포함되지 않은 Ni-$Al_2O_3$ 촉매가 우수한 활성을 보였다.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.5
• /
• pp.1241-1246
• /
• 2010

Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.

• Journal of Hydrogen and New Energy
• /
• v.21 no.1
• /
• pp.50-57
• /
• 2010

Stepwise production of syn-gas and hydrogen from methane on ferrite based media added with yttria-stabilized zirconia (YSZ) was carried out using a fixed bed infrared reactor. In this study, all M-ferrite (M=Co, Cu, Mn and Ni) media were prepared by co-precipitation method, and there the YSZ was added as a binder to improve thermal stability, reactivity, and resistance against carbon deposition. Most of the ferrite media containing YSZ showed the good redox property for temperature programmed reduction/oxidation (TPR/O) tests. Notably, the Cu-substituted ferrite medium with YSZ showed the great resistance against carbon deposition as well as the good reactivity for the stepwise production of syngas and hydrogen. Furthermore, it also showed the good durability without significant deactivation during five repeated cyclic tests.

• Journal of Hydrogen and New Energy
• /
• v.19 no.5
• /
• pp.394-402
• /
• 2008

The Effects of Cu or Ni additives co-added with Ce/Zr mixed oxides to Fe-based oxide mediums were investigated for the purpose of the replacement of Rh, a precious metal additive, in terms of hydrogen storage(reduction by hydrogen) and release(water splitting). From the results of temperature programmed reduction(TPR), initial reduction rate of iron oxide in the mediums was greatly increased with the addition of Cu, similar to that of Rh. For isothermal redox reaction of 10 cycles, the total amounts of hydrogen evolved in water splitting steps for the mediums added with Cu or Ni were highly maintained at ca. 7 mmol/g-material, even though the oxidation rates were slightly lower than that for the medium added with Rh. This result suggests that the replacement of Rh to Cu or Ni is possible as a co-additive for Fe-based oxide mediums.

• Journal of Hydrogen and New Energy
• /
• v.30 no.2
• /
• pp.95-102
• /
• 2019

In order to investigate the effect of water treatment on activity of WGS catalyst, $Cu/ZnO/MgO/Al_2O_3$ (CZMA) catalysts were synthesized by co-precipitation method. The prepared catalysts were water-treated at two different temperature (250, $350^{\circ}C$). Synthesized catalysts were characterized by using BET, SEM, $N_2O$ chemisorption, XRD, $H_2-TPR$ and XPS analysis. The catalytic activity tests were carried out at a GHSV of $28,000h^{-1}$ and a temperature range of $180-320^{\circ}C$. The reduction temperature decreased with water treatment and CZMA_250 catalyst showed the lowest reduction temperature and retained a large amount of $Cu^+$. Water-treated catalysts showed increased reactivity compared to untreated catalyst and the CZMA_250 catalyst showed higher catalytic activity on WGS reaction.

• Korean Journal of Chemical Engineering
• /
• v.35 no.11
• /
• pp.2185-2190
• /
• 2018

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of $450-550^{\circ}C$. Although $CeO_2$ is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as $CO_2$, CO and carbon deposits are produced during the reaction over $CeO_2$. We investigated the effect of iron in $FeO_x/CeO_2$ catalysts on methane oxychlorination. $FeO_x/CeO_2$ with 3 wt% iron shows the maximum yield at $510^{\circ}C$ with 23% conversion of methane and 65% selectivity of chloromethane. XRD and $H_2$ TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over $FeO_x/CeO_2$ than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.226.1-226.1
• /
• 2010

본연구에서는 GTL(gas to liquids)공정의 합성가스 생산을 위해 수증기-이산화탄소 복합개질반응(Combined Steam and Carbon dioxide Reforming of Methane, CSCRM)을 수행하였다. CSCRM은 수증기와 이산화탄소의 공급비 조절을 통해 $H_2$/CO비를 2로 맞추기 용이한 장점을 지니고 있어 다른 단일 개질 반응과 달리 합성가스 생산 시 $H_2$/CO 비율을 조절하기 위한 부가적인 공정이 필요하지 않아 경제적인 공정이다. 일반적으로 사용되는 Ni개질촉매는 가격대비 우수한 성능을 보이지만 S/C비가 낮은 CSCRM의 경우 촉매표면의 탄소침적에 의한 비활성화가 야기되는 문제점이 있다. 따라서 본 연구에서는 산소저장능력과 산소전달능력이 우수한 $CeO_2$를 조촉매로 첨가하여 표면에 형성된 코크 제거가 용이하도록 하였다. Ni-Ce/$MgAl_2O_4$촉매는 동시함침법(co-impregnation)으로 제조하였으며, Ni의 함량을 10wt%로 고정한 상태에서 Ce의 함량을 조절하여 Ce/Ni 최적비를 찾고자 하였다. XRD, TPR, BET, $H_2$-Chemisorption과 같은 촉매의 특성분석을 통해 촉매의 비표면적, 환원특성과 Ni입자의 분산도 등을 확인하였다. Ce를 첨가함에 따라 Ce2.5wt%까지는 비표면적이 증가하다가 이후 점차 줄어드는 경향성을 보였다. 또한, $H_2$-Chemisorption 결과 역시 비표면적과 유사한 경향성을 보였는데, Ce5.0wt%까지 Ni 분산도가 증가 하다가 다시 감소하는 것을 확인할 수 있었다. 반응실험은 $H_2O:CO_2:CH_4:N_2$ = 0.8:0.4:1:1의 공급조건에서 수행하였으며, 질소와 수소 환원분위기로 $700^{\circ}C$에서 1시간 환원 후 $650^{\circ}C$에서 $550^{\circ}C$범위로 온도를 떨어뜨려가면서 반응을 수행하였다. Ce를 첨가함에 따라 $CH_4$ 전환율이 증가를 하다가 Ce2.5wt% 이후 감소하는 것을 확인할 수 있었다. 이러한 높은 촉매 활성은 Ce 첨가로 인해 환원특성이 좋아지고 Ni분산도가 증가하여 담체와 강한 상호작용(SMSI)을 형성함으로 탄소침적 저항성 강화에 기인한 것이다.