• Korean Chemical Engineering Research
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• 제52권5호
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• pp.678-687
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• 2014

The catalytic performance of silicon carbide supported nickel catalysts modified with or without second metal (Co, Cu and Zn) for the methanation of CO has been investigated in a fixed-bed reactor using a feed consisting of 25% CO and 75% $H_2$ without any diluent gas. It has been found that the introduction of Co species can clearly improve the catalytic activity of Ni/SiC catalyst, whereas the addition of Cu or Zn can result in a significant decrease in the catalytic activity. The characterizations by means of XRD, TEM, XPS, CO-TPD and $H_2$-TPR indicate that the addition of Co could decrease the particle size of active metal, increase active sites on the surface of methanation catalyst, improve the chemisorption of CO and enhance the reducibility of methanation catalysts. Additionally, the special interaction between Co species and Ni species is likely favorable for the dissociation of adsorbed CO on the surface of catalyst, and this may also contribute to the high activity of 5Co-Ni/SiC catalyst for CO methanation reaction. For 5Cu-Ni/SiC catalyst and 5Zn-Ni/SiC catalyst, Cu and Zn species could cover partial nickel particles and decrease the chemisorption amount of CO. These could be responsible for the low methanation activity. In addition, a 150h stability test under 2 MPa and $300^{\circ}C$ showed that 5Co-Ni/SiC catalyst was very stable for CO methanation reaction.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.415-418
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• 2010

Highly ordered mesoporous silver material was successfully synthesized from a mesoporous silica template (KIT-6) with 3-D channel structure using the nano-replication method. The effects of $H_2$ or $O_2$ pretreatments on the catalytic performance of the mesoporous silver were investigated using a temperature programmed CO oxidation technique in a fixed bed reactor. The mesoporous silver material that was pretreated with $H_2$ exhibited an excellent catalytic activity compared to the as-prepared and $O_2$-pretreated catalysts. Moreover, this present mesoporous silver material showed good catalytic stability. For the CO oxidation, the apparent activation energy of the $H_2$-pretreated mesoporous silver catalyst was $61{\pm}0.5\;kJ\;mol^{-1}$, which was also much lower than the as-prepared ($132{\pm}1.5\;kJ\;mol^{-1}$) and $O_2$-pretreated ($124{\pm}1.4\;kJ\;mol^{-1}$) catalysts.

• 공업화학
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• 제10권1호
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• pp.85-92
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• 1999

고정층 촉매 반응기를 이용하여 ${\gamma}$-알루미나에 담지한 크롬산화물 촉매상에서 vinyl chloride의 완전산화잔응을 $240{\sim}300^{\circ}C$의 온도와 600~3,500 ppm의 농도범위에서 조사하였다. 반응은 vinyl chloride의 농도에 대하여 비선형적으로 변하였으며, 산소의 농도에 대하여는 0차 거동을 보였다. 또한 반응 생성물인 $H_2O$와 HCl를 반응물에 첨가하였을 때 vinyl chloride의 전환율에 영향이 거의 없었다. Vinyl chloride의 산화반응에 대한 몇 가지 반응모델을 가정하고 실험결과와 상관시켜 가장 잘 일치하는 모델을 도출하였다. 속도식의 해석결과 vinyl chloride의 산화반응은 산소로 피복된 촉매표면에 vinyl chloride가 흡착한 후 산화분해되며, vinyl chloride가 촉매표면에 흡착하여 반응을 방해한다는 가정하에서 도출된 반응속도 모델이 실험결과를 가장 잘 표현하였다. 실험치와 예측치간의 표준편차 백분율은 약 5.2% 정도였으며 활성화에너지는 18.9 kcal/mol으로 계산되었다.

• 청정기술
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• 제20권3호
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• pp.256-262
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• 2014

본 연구에서는 ${\gamma}-Al_2O_3$에 구리를 함침시킨 촉매를 고정층 반응기에 충전시킨 후 휘발성유기물질(VOCs)인 벤젠의 촉매산화 반응특성을 살펴보았다. 실험조건은 반응온도 $200{\sim}500^{\circ}C$, 벤젠의 농도 400~650 ppm, 가스유입량 50~100 cc/min, 공간속도 $7,500{\sim}22,500hr^{-1}$의 범위로 적용하였다. BET분석, 주사전자현미경(SEM), 열천칭(TGA) 분석을 통해 제조된 촉매의 물성을 조사하였으며, 벤젠의 촉매산화반응의 전환율에 대하여 고찰하였다. 실험결과, 벤젠의 농도와 공간속도가 낮아질수록 벤젠 산화반응의 전환율은 증가함을 알 수 있었다. 벤젠의 촉매산화반응은 1차 균일반응으로 해석될 수 있었으며, 반응의 활성화 에너지(Ea)는 17.2 kcal/mol, 빈도인자(A)는 $1.33{\times}10^6sec^{-1}$이었다.

• 대한환경공학회지
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• 제29권4호
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• pp.444-451
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• 2007

본 연구에서는 $\gamma-Al_2O_3$에 전이금속들을 함침시킨 촉매를 고정층 반응기에 충전시킨후 휘발성유기물질(VOCs)인 밴젠을 일정농도로 공급하면서 촉매산화 특성을 살펴보았다. 전이금속으로는 구리, 니켈, 망간, 철등을 포함해 8가지 금속을 선정하였고, 실험조건은 반응온도 $200\sim500^{\circ}C$, 벤젠의 농도 $1,000\sim3,000$ ppm, 공간속도 $5,000\sim60,000\;hr^{-1}$의 범위로 적용하였다. BET분석, 전자주사현미경(SEM), XRD분석을 통해 제조된 촉매의 물성을 조사하였으며, VOC 촉매산화반응의 전환율에 대하여 고찰하였다. 실험결과, VOC농도와 공간속도가 낮을수록 VOC산화반응의 전환율은 증가함을 알 수 있었다. 여러 전이금속촉매들 중에 Cu촉매가 벤젠에 대해 가장 높은 활성을 나타내었고, 소성온도 $500^{\circ}C$조건에서 전이금속의 함침율이 15 wt%일 경우 가장 높은 전환율을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제31권4호
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• pp.808-814
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• 2010

Activities of nanostructure HZSM-5 and Co-ZSM-5 catalysts (with different Co-loading) for catalytic conversion of ethyl acetate and toluene were studied. The catalysts were prepared by wet impregnation method and were characterized by XRD, BET, SEM, TEM and ICP-AES techniques. Catalytic studies were carried out inside a U-shaped fixed bed reactor under atmospheric pressure and different temperatures. Toluene showed lower reactivity than ethyl acetate for conversion on Co-ZSM-5 catalysts. The effect of Co loading on conversion was prominent at temperatures below $400^{\circ}C$ and $450^{\circ}C$ for ethyl acetate and toluene respectively. In a binary mixture of organic compounds, toluene and ethyl acetate showed an inhibition and promotional behaviors respectively, in which the conversion of toluene was decreased at temperatures above $350^{\circ}C$. Inhibition effect of water vapor was negligible at temperatures above $400^{\circ}C$. An artificial neural networks model was developed to predict the conversion efficiency of ethyl acetate on Co-ZSM-5 catalysts based on experimental data. Predicted results showed a good agreement with experimental results. ANN modeling predicted the order of studied variable effects on ethyl acetate conversion, which was as follows: reaction temperature (50%) > ethyl acetate inlet concentration (25.085%) > content of Co loading (24.915%).

• 청정기술
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• 제20권3호
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• pp.218-225
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• 2014

석탄의 가스화는 촉매 도입 시 온순 조건에서 가능하나, 석탄 내 회분에 의한 비활성화에 의해 반복적인 촉매 활용이 힘들다. 이에 본 연구에서는 삼화 원탄에서 회분을 제거하여 삼화 무회분탄(ash-free coal, AFC)을 제조한 후 가스화 반응성을 원탄과 비교하여 알아보았다. 우선 원탄을 대상으로 고정층 반응기에서 수증기 공급량, 공간 속도(space velocity), 온도 및 촉매를 변수로서 가스화 조건을 결정하였다. 고체상 혼합법으로 다양한 촉매 도입 시, 유동성을 갖는 $K_2CO_3$가 가장 높은 활성을 보였다. 무회분탄은 원탄보다 낮은 반응성을 보였으며, 이는 용매(1-methylnaphthalene, 1-MN)를 이용한 고온 추출 및 건조 공정 중에 소모된 산소 기능기 함량과 증가된 탄화도(carbonization)에 기인한다. $K_2CO_3$ 가 혼합된 무회분탄의 반응성은 급격히 증가하여 낮은 온도 ($700^{\circ}C$)에서도 높은 전환율을 보였다. 이때 $H_2/CO$와 $CO_2/CO$ 비율도 증가하는데, 이는 촉매에 의해 수성가스전환(water-gas shift) 반응이 활성화됨에 기인한다. 본 연구에서는 무회분탄의 저온 촉매 가스화 반응을 통해 석탄 가스화 공정의 경제성이 개선될 수 있음을 확인하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.33-36
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• 2014

Gasification of biomass produces syngas containing CO, $H_2$ and/or $CH_4$, which can then be converted into energy or value-added fuels. One of key issues for efficient gasification is to minimize tar concentration in the syngas for use in a final conversion device such as gas engine. This study investigated the decomposition of primary tar by catalytic cracking using char as catalyst, of which the feature can be integrated into a fixed bed gasifier design. The pyrolysis vapor containing tar from pyrolysis of wood at $500^{\circ}C$ was passed through a reactor filled with or without char at $800^{\circ}C$ for a residence time of 1, 3 or 5 sec. Then, the condensable vapor (water and tar) and gases were analyzed for the yields and elemental composition. Four types of char particles with different microscopic surface area and pore size distribution: wood, paddy straw, palm kernel shell and activated carbon. The results were analyzed for the mass and carbon yields of tar and the composition of product gases to conclude the effects of char types and residence time.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.135-141
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• 2014

$NH_3$-SCR has high NOx removal efficiency approximately 80~90%. Recently, the copper or iron ion-exchanged zeolite catalysts are widely used as automobile SCR catalysts. In this paper, the effect of the space velocity, temperature of reaction and $NO_2$ addition on the $NH_3$-SCR reaction were studied using various zeolite SCR catalysts. The test was conducted with small sized fresh catalysts in a laboratory fixed-bed flow reactor system using simulated gases. It is found that the activity of the BEA is better than MFI. It seems that three-dimensional framework and a wide pore entrance of BEA enhances the SCR activity. It is also found that low temperature activity of Cu-zeolites was better than Fe-zeolites. Once $NO_2$ was added, the NOx conversion activity of the Cu-zeolite was slightly enhanced, whereas remarkable improvement was achieved by Fe-zeolite.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.525-530
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• 2014

Titanium dioxide nanotube supported ZSM-5 zeolite composite catalyst was fabricated by decorating ZSM-5 zeolite on the hydrothermally synthesized titanium dioxide via hydrothermal process and subsequent annealing. The catalyst was characterized by X-ray powder diffraction (XRD), Transmission electron microscopy (TEM) and Nitrogen adsorption-desorption (BET). The surface acidity of the catalyst was measured by means of Fourier transform infrared (FT-IR) spectrum of pyridine adsorption. And the catalytic activity for ethanol dehydration to ethylene was evaluated in a continuous flow fixed-bed reactor. Attributed to the increase of the effective surface acid sites caused by titanium dioxide nanotube as electron acceptor, titanium dioxide nanotube supported ZSM-5 zeolite composite catalyst exhibits strongly enhanced activity for ethanol dehydration to ethylene.