• Title/Summary/Keyword: Ammonia$Al_2O_3$

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Ammonia Conversion in the Presence of Precious Metal Catalysts (귀금속촉매하에서 암모니아의 전환반응)

  • Jang, Hyun Tae;Park, YoonKook;Ko, Yong Sig
    • Korean Chemical Engineering Research
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    • v.46 no.4
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    • pp.806-812
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    • 2008
  • The ammonia decomposition reaction has been of increasing interest as a means of treating ammonia in flue gas in the presence of precious metal catalyst. Various catalysts, $Pt-Rh/Al_2O_3$, $Pt-Rh/TiO_2$, $Pt-Rh/ZrO_2$, $Pt-Pd/Al_2O_3$, $Pd-Rh/Al_2O_3$, $Pd-Rh/TiO_2$, $Pd-Rh/ZrO_2$, $Pt-Pd-Rh/Al_2O_3$, $Pd/Ga-Al_2O_3$, $Rh/Ga-Al_2O_3$, and Ru/Ga-$Al_2O_3$, were synthesized by using excess wet impregnation method. Using a homemade 1/4" reactor at $10,000{\sim}50,000hr^{-1}$ of space velocity in the presence of precious metal catalyst ammonia decomposition reactions were carried out to investigate the catalyst activity. The inlet ammonia concentration was maintained at 2,000 ppm, with an air balance. Both $T_{50}$ and $T_{90}$, defined as the temperatures where 50% and 90% of ammonia, respectively, are converted, decreased significantly when alumina-supported catalysts were applied. In terms of catalytic performance on the ammonia conversion in the presence of hydrogen sulfide, $Pt-Rh/Al_2O_3$ catalyst showed no effect on the poisoning caused by hydrogen sulfide. These results indicate that platinum-rhodium bimetallic catalyst is a useful catalyst for ammonia decomposition.

Experiment on Heat Transfer and Absorption Performance Enhancement for Binary Nanofluids (NH3/H2O + Nano-Particles) (이성분 나노유체 (NH3/H2O + 나노입자)의 열전달 및 흡수성능 촉진실험)

  • Lee, Jin-Ki;Jung, Chung-Woo;Kang, Yong-Tae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.9
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    • pp.669-675
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    • 2008
  • The objectives of this paper are to examine the effect of nano-particles on the pool type absorption heat transfer enhancement and to find the optimal conditions to design a highly effective compact absorber for ammonia/water absorption system. The effect of $Al_2O_3$ nano-particles and carbon nanotube(CNT) on the absorption performance is studied experimentally. The experimental ranges of the key parameters are 20% of ammonia concentration, $0{\sim}0.08\;vol%$ (volume fraction) of CNT particles, and $0{\sim}0.06 \;vol%$ of $Al_2O_3$ nano-particles. For the ammonia/water nanofluids, the heat transfer rate and absorption rate with 0.02 vol% $Al_2O_3$ nano-particles were found to be 29% and 18% higher than those without nano-particles, respectively. It is recommended that the concentration of 0.02 vol% of $Al_2O_3$ nano-particles be the best candidate for ammonia/water absorption performance enhancement.

The Powder Preparation of Blue Cobalt Aluminate at 210 °C Using the Malonate Method

  • Lee, Gong-Yeol;Lee, Dong-Hoon;Kim, Hong-Gun;Kim, Yoo-Young
    • Bulletin of the Korean Chemical Society
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    • v.31 no.1
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    • pp.47-51
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    • 2010
  • A powder, containing 80 percent of blue cobalt aluminate $(CoAl_2O_4)$ crystallites, was synthesized at $210 ^{\circ}C$ using a (metal nitrate-malonic acid-ammonium hydroxide-ammonium nitrate) system. The optimal amount of concentrated ammonia water and initial decomposition temperature were determined for the blue $CoAl_2O_4$ crystallites preparation. Three $CoAl_2O_4$ precursor pastes, corresponding to the various amounts of concentrated ammonia water, were prepared by evaporating the initial solutions in an electric furnace fixed at $80 ^{\circ}C$ under a vacuum of 25 torr. The initial solution was used to dissolve the starting materials. The powder with the maximum content (80%) of blue $CoAl_2O_4$ crystallites was prepared when the prepared precursor was decomposed at $210 ^{\circ}C$. The blue $CoAl_2O_4$ crystallite content in the prepared sample decreased with increasing initial decomposition temperature. For 0.2 mole of the $Al^{3+}$ ion, the chemical compositions of the precursor corresponded to molar ratios of 0.4, 1.40, 2.56 and 2.00 for the $Co^{2+}$ ion, malonic acid, ammonia and ammonium nitrate per mole of the $Al^{3+}$ ion, respectively. The blue $CoAl_2O_4$ crystallite content in the sample decreased with the amount of ammonia deviated from the optimal value. The characteristics of the powders were examined using X-ray diffraction, optical microscopy, Fourier transformation infrared spectroscopy and the Brunauer-Emmett-Teller technique.

Catalytic Ammonia Decomposition on Nitridation-Treated Catalyst of Mo-Al Mixed Oxide (Mo-Al 복합 산화물의 질화반응 처리된 촉매상에서 암모니아 촉매 분해반응)

  • Baek, Seo-Hyeon;Youn, Kyunghee;Shin, Chae-Ho
    • Korean Chemical Engineering Research
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    • v.60 no.1
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    • pp.159-168
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    • 2022
  • Catalytic activity in ammonia decomposition reaction was studied on Mo-Al nitride obtained through temperature programmed nitridation of calcined Mo-Al mixed oxide prepared by varying the MoO3 quantity in the range of 10-50 wt%. N2 sorption analysis, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR), and transmission electron microscopy (TEM) to investigate the physicochemical properties of the prepared catalyst were performed. After calcination at 600 ℃, the XRD of Mo-Al oxide showed γ-Al2O3 and Al2(MoO4)3 phases, and the nitride after nitridation showed an amorphous form. The specific surface area after nitridation by topotactic transformation of MoO3 to nitride was increased due to the formation of Mo nitride, and the Mo nitride was observed to be supported on γ-Al2O3. As for the catalytic activity in the ammonia decomposition reaction, 40 wt% MoO3 showed the best activity, and as the nitridation time increases, the activity increased, and thus the activation energy decreased.

An Efficient Method for the Production of Cyclohexylamine from Cyclohexanone and Ammonia over Cu-Cr-La/γ-Al2O3

  • Qin, Shuanglin;Wang, Pan;Huang, Shuangping;Liu, Shuai;Wang, Gaopeng;Wang, Liping;Sun, Meng;Wang, Xiaoji
    • Journal of the Korean Chemical Society
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    • v.59 no.6
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    • pp.493-498
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    • 2015
  • The reductive amination of cyclohexanone with ammonia over Cu-Cr-a/γ-Al2O3 was investigated. It was found that a proper solvent with high solubility of ammonia and 4Å molecular sieves for the elimination of generated water contributed to the formation of cyclohexylamine in the premixing process. In addition, the addition of ammonia in the fixedbed reactor could obviously improve the conversion of cyclohexanone to cyclohexylamine. Finally, reaction conditions including reaction temperature, hydrogen pressure and charging rate of the premix were optimized. Under the optimized conditions, cyclohexylamine was obtained in 83.06% yield.

Ammonia gas sensing characteristics of LaFeO3 thick-films With Al2O3 additives (Al2O3를 첨가한 LaFeO3 후막의 암모니아 가스 감지특성)

  • Kim, Jun-Gon;Ahn, Byeong-Yeol;Ma, Tae-Young;Park, Ki-Cheol;Kim, Jeong-Gyoo
    • Journal of Sensor Science and Technology
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    • v.11 no.1
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    • pp.18-27
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    • 2002
  • $LaFeO_3$-based thick films with 2wt.%, 5wt.% and 10wt.% $Al_2O_3$ additives were fabricated by screen printing method on $Al_2O_3$ substrates. Structural, electrical and ammonia gas sensing characteristics of the thick films with different heat treatment temperatures were examined. From XRD results, the compound of $LaFeO_3$ and $Al_2O_3$ was not found until the heat treatment at $1200^{\circ}C$. SEM microphotograph showed similar grain growth despite the amount of $Al_2O_3$ additives with the heat treatment. Thick films with high activation energy and low resistance in the electrical properties showed high sensitivity for gases. Thick films with 2wt % $Al_2O_3$ additives heat-treated at $1200^{\circ}C$ showed the sensitivities of 210% for 100 ppm $NH_3$ gas at the working temperature of $350^{\circ}C$. The thick films showed food selectivity to $NH_3$ gas.

Synthesis of Pyridine and β-Picoline from Acrolein and Ammonia on Pd/SiO2-Al2O3 Catalysts (Pd/SiO2-Al2O3 촉매상에서 아크로레인과 암모니아로 부터 피리딘과 β-피콜린의 합성)

  • Chun, Sung-Woo;Choi, Jung-Kun;Oh, Seok-Youn;Na, Suk-Eun;Park, Dae-Won
    • Applied Chemistry for Engineering
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    • v.2 no.2
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    • pp.138-146
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    • 1991
  • $Pd/SiO_2-Al_2O_3$ catalysts were prepared for the synthesis of pyridine and ${\beta}$-picoline from acrolein and ammonia. The activity of these catalysts decreased considerably by the formation of deposits on catalyst surface during the reaction. TPR study showed that the deposits were formed by the condensation polymerization of acrolein and ammonia. The conversion and production rate of pyridine and ${\beta}$-picoline decreased with the partial pressure of acrolein. The amount of deposits and the regeneration temperature of spent catalysts increased with the partial pressure of acrolein but they were independent of the concentration of ammonia.

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Removal of NO Using CuO/3Al2O3 · 2SiO2 Catalyst Impregnated Ceramic Candle Filters (산화구리 촉매담지 세라믹 캔들필터를 이용한 NO 제거)

  • 홍민선;문수호;이재춘;이동섭
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.3
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    • pp.291-302
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    • 2004
  • The CuO/$3AL_2O_3{\cdot}2SiO_2$ catalyst impregnated ceramic candle filters for nitrogen oxides removal were prepared by porous mullite($3AL_2O_3{\cdot}2SiO_2$) support and CuO catalyst deposited on this support to achieve uniformly dispersed CuO deposition, which are impregnated into the pores of available alumino-silicate ceramic candle filter. The CuO/3$AL_2O_3{\cdot}2SiO_2$ catalyst impregnated ceramic candle filters were characterized by XRD, BET, air permeability, pore size, SEM and catalytic tests in the reduction of NOx by NH$_3$. The observed effects of CuO/3$AL_2O_3{\cdot}2SiO_2$ impregnated ceramic candle filters in SCR reaction are as follows : (1) when the content of CuO catalyst increased further, activity of NO increased. (2) NO conversion at first increased with temperature and then decreased at high temperatures (above 40$0^{\circ}C$), possibly due to the occurrence of the ammonia oxidation reaction. (3) In pilot plant test for 3 months, NO conversion was greater than 90%.

A Study on the Electrical Characterisitics of $Al^{3+}$-doped ZnO Semiconductor Gas Sensor ($Al^{3+}$ 이온이 첨가된 ZnO 반도체 가스 센서의 전기적 특성에 관한 연구)

  • Joung, Yui-Nam;Lee, Keon-Hyeoug;Kim, Chang-Ook;Kim, Jong-Dae
    • Proceedings of the KIEE Conference
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    • 1987.11a
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    • pp.245-247
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    • 1987
  • In this thesis, ZnO semiconductor gas sensors doped by the $Al^{3+}$ were fabricated by the miexed oxide method. The specimens were sintered for 5(hr) at $1000-1200^{\circ}C$ and the I-V, sensitivity were investigated in acetone gas or ammonia gas. As a result, I-V curves of specimens as a function of temperature variation showed characteristics of linear resistor that the current was proportional to the, temperature at constant voltage. For the sensitivity of acetone, 1Wt $Al^{3+}$-ZnO has the hight 0.91, ammonia gas, 2Wt $Al^{3+}$-ZnO specimen has the hight 0.90. Hence, the operating temperature of specimens were both $300^{\circ}C$.

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Effects of Surface Nitrification on Thermal Conductivity of Modified Aluminum Oxide Nanofibers-Reinforced Epoxy Matrix Nanocomposites

  • Kim, Byung-Joo;Bae, Kyong-Min;An, Kay-Hyeok;Park, Soo-Jin
    • Bulletin of the Korean Chemical Society
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    • v.33 no.10
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    • pp.3258-3264
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    • 2012
  • Aluminum oxide ($Al_2O_3$) nanofibers were treated thermally under an ammonia ($NH_3$) gas stream balanced by nitrogen to form a thin aluminum nitride (AlN) layer on the nanofibers, resulting in the enhancement of thermal conductivity of $Al_2O_3$/epoxy nanocomposites. The micro-structural and morphological properties of the $NH_3$-assisted thermally-treated $Al_2O_3$ nanofibers were characterized by X-ray diffraction (XRD) and atomic force microscopy (AEM), respectively. The surface characteristics and pore structures were observed by X-ray photoelectron spectroscopy (XPS), Zeta-potential and $N_2$/77 K isothermal adsorptions. From the results, the formation of AlN on $Al_2O_3$ nanofibers was confirmed by XRD and XPS. The thermal conductivity (TC) of the modified $Al_2O_3$ nanofibers/epoxy composites increased with increasing treated temperatures. On the other hand, the severely treated $Al_2O_3$/epoxy composites showed a decrease in TC, resulting from a decrease in the probability of heat-transfer networks between the filler and matrix in this system due to the aggregation of nanofiber fillers.