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  • Title/Summary/Keyword: temperature programmed reaction

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Steam Reforming of Ethylene Glycol over Ni/Al2O3 Catalysts: Effect of the Preparation Method and Reduction Temperature (Ni/Al2O3 촉매를 사용한 에틸렌글리콜의 수증기 개질 반응: 촉매 제조 방법과 환원온도의 영향)

  • Choi, Dong Hyuck;Park, Jung Eun;Park, Eun Duck
    • Korean Chemical Engineering Research
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    • v.53 no.3
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    • pp.372-381
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    • 2015
  • The effect of preparation method on the catalytic activities of the Ni/Al2O3 catalysts on steam reforming of ethylene glycol was investigated. The catalysts were prepared with various preparation methods such as an incipient wetness impregnation, wet impregnation, and coprecipitation method. In the case of coprecipitation method, various precipitants such as KOH, K2CO3, and NH4OH were compared. The prepared catalysts were characterized by using N2 physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperatureprogrammed reduction, pulsed H2 chemisorption, temperature-programmed oxidation, scanning electron microscopy, and thermogravimetric analysis. Among the catalysts reduced at 773 K, the Ni/Al2O3 catalyst prepared by a coprecipitation with KOH or K2CO3 as precipitants showed the best catalytic performance. The preparation method affected the particle size of Ni, reducibility of nickel oxides, catalytic performance (activity and stability), and types of coke formed during the reaction. The Ni/Al2O3 catalyst prepared by a coprecipitation with KOH showed the increasing catalytic activity with an increase in the reduction temperature from 773 to 1173 K because of an increase in the reduction degree of Ni oxide species even though the particle size of Ni increased with increasing reduction temperature.

Acidic Properties of ZSM-5 Zeolite Catalyst (ZSM-5 제올라이트 촉매의 산성도)

  • Byoung Joon Ahn;Joon Ryeo Park;Hakze Chon
    • Journal of the Korean Chemical Society
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    • v.33 no.2
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    • pp.177-184
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    • 1989
  • Acidic properties of ZSM-5 zeolite catalysts were investigated by temperature-programmed desorption technique and ir spectroscopy. Ammonia t.p.d. pattern of HZSM-5 showed three different states, designated as α,β and γ. The amount of γ-state decreased with increasing SiO2/Al2O3 ratio, and upon cation-exchanging with alkali cations. From the ir adsorption spectra of absorbed pyridine and the reaction study of toluene alkylation, the γ-state could be explained to be due to the strong Bronsted acid sites of H-ZSM-5. Also they showed that the interaction between alkali cation-exchanged ZSM-5 and bases, i.e. NH3 and pyridine, was increasing with decreasing the size of cations.

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The Effect of Calcination/reduction Condition Over Ru/TiO2 on the NH3-SCO Reaction Activity (소성/환원 조건이 Ru/TiO2의 NH3-SCO 반응활성에 미치는 영향)

  • Shin, Jung Hun;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.31 no.1
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    • pp.108-114
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    • 2020
  • In this study, NH3-selective catalytic oxidation (SCO) efficiencies according to calcination/reduction conditions were compared when preparing various Ru[1]/TiO2 catalysts. The Ru[1]/TiO2 red catalyst had better NH3 conversion and NH3 to N2 conversion than those of Ru[1]/TiO2 cal. Physico-chemical properties of Ru[1]/TiO2 catalysts were confirmed by Brunauer Emmett Teller (BET), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (H2-TPR) analyses, and the properties were shown to affect the dispersion and surface adsorption oxygen species (Oβ) ratio of the active metal.

Reactivity and Preparation of Perovskite-Type Mixed Oxides LaBO3(B = Mn, Fe, Co) by Citrate Sol-Gel Method (Citrate Sol-Gel법에 의한 Perovskite형 복합 산화물 LaBO3(B = Mn, Fe, Co)의 생성 및 환원 반응성)

  • Hwang, Ho Sun;Park, Il Hyeon
    • Journal of the Korean Chemical Society
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    • v.38 no.4
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    • pp.276-282
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    • 1994
  • Perovskite-type mixed oxides LaBO3(B = Mn, Fe, Co) were prepared by citrate sol-gel method in air(850C, 24h). The oxygen stoichiometries and structures of these oxides were determined by XRD and TPR results as followings; LaMnO3.16(a = 5.507, c = 13.329 \AA, hexagonal), LaFeO3.17(a = 5.554, b = 5.555, c = 7.863 \AA, orthorhomibic), LaCoO3.0(a = 5.436, c = 13.095 \AA, hexagonal). The temperature programmed reduction(TPR) experiments in static 300 torr H2 atmosphere shows that the reduction reaction of LaBO3(B = Mn, Fe, Co) proceeds into two stages, and thermal stabilities of these oxides decreased in the order of LaMnO3 > LaFeO3 > LaCoO3. According to the kinetic analysis the lowest activation energy was obtained for LaCoO3.

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Preparation and Characterization of Al-Zr Mixed Oxide Catalysts (Al-Zr 혼합산화물 촉매의 제조 및 특성분석)

  • Park, Jung-Hyun;Youn, Hyun Ki;Shin, Chae-Ho
    • Clean Technology
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    • v.22 no.1
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    • pp.9-15
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    • 2016
  • xAl-yZr mixed oxide catalysts with different molar ratios of Al/(Al+Zr) were prepared by a co-precipitation method and its catalytic performance was compared in the iso-propanol dehydration as a model reaction. The catalysts were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), N2 adsorprion-desorption, NH3 temperature programmed desorption (NH3-TPD), and iso-propanol TPD analyses. The addition of Al into ZrO2 promoted the formation of relatively small particles with large surface areas and retarded the transformation of teragonal phase to monoclnic phase. NH3-TPD results revealed that the relative acidity of the catalysts increased along with the increase of Al molar ratio. The catalytic activity for the dehydration of iso-propanol to propylene was also increased with the same tendency. The catalytic activity could be correlated with high surface area, acidity and easy desorption of iso-propanol.

Structure and Reactivity of Bimetallic Catalyst (이원금속 촉매의 구조와 반응성)

  • Yie, Jae-Eue
    • Applied Chemistry for Engineering
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    • v.3 no.1
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    • pp.24-34
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    • 1992
  • Recent studies dealing with the fundamental understanding and applications of bimetallic catalysts are discussed. Bimetallic catalysts have had a major industrial impact, specifically for the reforming of petroleum naphtha, for the hydrogen reduction of carbon monoxide, and for the three way catalytic converter system. The action of the bimetallic catalysts in these reactions may be interpreted in terms of ensembles, electronic influences and surface structure. Various combinations of metal pairs have been considered in order to evaluate the role played by the added metals. For catalyst selectivity control, the possibility of surface enrichment of one element has been recognised. More generally, the influence of preparative variables on the formation of supported catalysts has been clarified, In particular by temperature programmed reduction (TPR). Information on the structure of bimetallic catalysts has been obtained with chemical probes, such as chemisorption and reaction rate measurement and physical probes, such as extended X-ray absorption fine structure (EXAFS), scanning transmission electron microscopy (STEM) and Xe-NMR.

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Fabrication of Tungsten Powder Mixtures with Nano and Micro Size by Reduction of Tungsten Oxides (텅스텐 산화물의 환원을 이용한 나노/마이크로 크기 텅스텐 혼합분말 제조)

  • Kwon, Na-Yeon;Jeong, Young-Keun;Oh, Sung-Tag
    • Korean Journal of Materials Research
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    • v.27 no.10
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    • pp.513-517
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    • 2017
  • An optimum route to fabricate a hybrid-structured W powder composed of nano and micro size powders was investigated. The mixture of nano and micro W powders was prepared by a ball milling and hydrogen reduction process for WO3 and W powders. Microstructural observation for the ball-milled powder mixtures revealed that the nano-sized WO3 particles were homogeneously distributed on the surface of large W powders. The reduction behavior of WO3 powder was analyzed by a temperature programmed reduction method with different heating rates in Ar-10% H2 atmosphere. The activation energies for the reduction of WO3, estimated by the slope of the Kissinger plot from the amount of reaction peak shift with heating rates, were measured as 117.4 kJ/mol and 94.6 kJ/mol depending on reduction steps from WO3 to WO2 and from WO2 to W, respectively. SEM and XRD analysis for the hydrogen-reduced powder mixture showed that the nano-sized W particles were well distributed on the surface of the micro-sized W powders.

Adsorption of Nitrogen Dioxide on Transition-Metal-Oxide-Incorporated Hydrotalcites (전이금속 산화물이 고정된 하이드로탈사이트에 이산화질소 흡착)

  • Park, Ji Won;Seo, Gon
    • Korean Chemical Engineering Research
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    • v.46 no.6
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    • pp.1029-1038
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    • 2008
  • Transition-metal-oxide-incorporated hydrotalcites were prepared by hydrothermal reaction of their synthetic mixtures containing precursors of transition metal oxides and their properties of nitrogen dioxide adsorption was investigated. The dispersion of transition metal oxides on the hydrotalcites and the amount and the state of nitrogen dioxide adsorbed on them were examined by using XRD, SEM, XPS, nitrogen adsorption, a gravimetric adsorption system, FT-IR spectroscopy and temperature programmed desorption techniques. Transition metal oxides were mainly incorporated on their surface and the incorporation of iron and nickel oxides to the hydrotalcites increased their adsorption amounts of nitrogen dioxide. The dispersion of iron oxide on the hydrotalcites was effective in increasing the amount of nitrogen dioxide adsorption, while too much amount of iron oxide incorporation reduced the amount of nitrogen dioxide adsorption due to masking of surface basic sites by agglomerated iron oxide. Although the incorporation of iron oxide to the hydrotalcites lowered the adsorption strength of nitrogen dioxide, the incorporation of it with a proper amount enhanced the amount of nitrogen dioxide adsorption and the stability against the hydrothermal treatment.

Porous W-Ni Alloys Synthesized from Camphene/WO3-NiO Slurry by Freeze Drying and Heat Treatment in Hydrogen Atmosphere (Camphene/WO3-NiO 슬러리의 동결건조 및 수소분위기 열처리에 의한 W-Ni 다공체 제조)

  • Park, Sung Hyun;Park, Seong-Min;Park, So-Jeong;Park, Bo-Yeong;Oh, Sung-Tag
    • Korean Journal of Materials Research
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    • v.28 no.2
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    • pp.108-112
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    • 2018
  • The present study demonstrates the effect of raw powder on the pore structure of porous W-Ni prepared by freeze drying of camphene-based slurries and sintering process. The reduction behavior of WO3 and WO3NiO powders is analyzed by a temperature programmed reduction method in Ar-10% H2 atmosphere. After heat treatment in hydrogen atmosphere, WO3NiO powder mixture is completely converted to metallic W without any reaction phases. Camphene slurries with oxide powders are frozen at 30C, and pores in the frozen specimens are generated by sublimation of the camphene during drying in air. The green bodies are hydrogen-reduced at 800C and sintered at 1000C for 1 h. The sintered samples show large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The strut between large pores, prepared from pure WO3 powder, consists of very fine particles with partially necking between the particles. In contrast, the strut densification is clearly observed in the Ni-added W sample due to the enhanced mass transport in activation sintering.

Glycerol Steam Reforming for Hydrogen Production on Metal-ceramic Core-shell CoAl2O4@Al Composite Structures (금속-세라믹 Core-Shell CoAl2O4@Al 구조체를 적용한 불균일계 촉매의 글리세롤 수소전환 반응특성)

  • Kim, Jieun;Lee, Doohwan
    • Clean Technology
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    • v.21 no.1
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    • pp.68-75
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    • 2015
  • In this study, we investigated the structure and properties of a highly heat conductive metal-ceramic core-shell CoAl2O4@Al micro-composite for heterogeneous catalysts support. The CoAl2O4@Al was prepared by hydrothermal surface oxidation of Al metal powder, which resulted in the structure with a high heat conductive Al metal core encapsulated by a high surface area CoAl2O4 shell. For comparison, CoAl2O4 was also prepared by co-precipitation method and also utilized for a catalyst support. Rh catalysts supported on CoAl2O4@Al and CoAl2O4 were prepared by incipient wetness impregnation and characterized by N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO chemisorption, and temperature-programmed reduction (TPR). The properties of catalysts were investigated for glycerol steam reforming reaction for hydrogen production at 550 ℃. Rh/CoAl2O4@Al exhibited about 2.8 times higher glycerol conversion turnover frequency (TOF) than Rh/CoAl2O4 due to facilitated heat transport through the core-shell structure. The CoAl2O4@Al and CoAl2O4 also showed some catalytic activities due to a partial reduction of Co on the support, and a higher catalytic activity was also found on the CoAl2O4@Al core-shell than CoAl2O4. These catalysts, however, displayed deactivation on the reaction stream due to carbon deposition on the catalysts surface.