• Title/Summary/Keyword: selective catalytic oxidation

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Characterization Studies for the Selective Catalytic Oxidation of Ammonia Utilizing Ce/TiO2 Catalyst (Ce/TiO2 촉매를 이용한 암모니아의 선택적 산화반응 특성 연구)

  • Lee, Hyun Hee;Kim, Ki Wang;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.24 no.5
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    • pp.494-498
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    • 2013
  • In this study, selective catalytic oxidation (SCO) of $NH_3$ using $Ce/TiO_2$ catalyst was examined to control the slipped NH3 from various pollutants. It was found that the catalytic activity increased with increasing the Ce loadings till reaching 10 wt% Ce loading. However, when Ce loaded over 10 wt%, the activity of catalysts rather decreased than that of catalysts, below 10 wt% Ce. Therefore, the composition of $Ce/TiO_2$ catalyst optimized in this study can be applied to industrial fields.

Influence of Active Metal Dispersion over Pt/TiO2 Catalyst on NH3-SCO Reaction Activity (Pt/TiO2 촉매의 활성금속 분산도가 NH3-SCO 반응활성에 미치는 영향)

  • Shin, Jung Hun;Kwon, Dong Wook;Kim, Geo Jong;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.29 no.1
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    • pp.22-27
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    • 2018
  • In this study, the effect of physical properties of $Pt/TiO_2$ on $NH_3$-selective catalytic oxidation (SCO) reaction at $200{\sim}350^{\circ}C$ was investigated. CO-chemisoption and BET analysis were carried out to verify physical properties of $Pt/TiO_2$. By characterizing physical properties of $Pt/TiO_2$ with respect to the Pt loading, the metal dispersion degree decreased as a function of the Pt loading amount. Also, the catalyst having a higher metal dispersion showed an excellent conversion efficiency of $NH_3$ to $N_2$. Since the specific surface area of the support affects the metal dispersion, $Pt/TiO_2$ catalysts were prepared using $TiO_2$ with different physical properties. As a result, it was confirmed that the catalyst having a wide specific surface area exhibited a excellent conversion of $NH_3$ to $N_2$.

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.

Effect of Water on the Kinetics of Nitric Oxides Reduction by Ammonia over V-based Catalyst (바나듐계 촉매상에서 암모니아를 이용한 질소산화물의 환원반응속도에 수분이 미치는 영향에 관한 연구)

  • Kim, Young-Deuk;Jeong, Soo-Jin;Kim, Woo-Seung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.6
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    • pp.73-82
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    • 2012
  • The main and side reactions of the three selective catalytic reduction (SCR) reactions with ammonia over a vanadium-based catalyst have been investigated using synthetic gas mixtures in the temperature range of $170{\sim}590^{\circ}C$. The three SCR reactions are standard SCR with pure NO, fast SCR with an equimolar mixture of NO and $NO_2$, and $NO_2$ SCR with pure $NO_2$. Vanadium based catalyst has no significant activity in NO oxidation to $NO_2$, while it has high activity for $NO_2$ decomposition at high temperatures. The selective catalytic oxidation of ammonia and the formation of nitrous oxide compete with the SCR reactions at the high temperatures. Water strongly inhibits the selective catalytic oxidation of ammonia and the formation of nitrous oxide, thus increasing the selectivity of the SCR reactions. However, the presence of water inhibits the SCR activity, most pronounced at low temperatures. In this study, the experimental results are analyzed by means of a dynamic one-dimensional isothermal heterogeneous plug-flow reactor (PFR) model according to the Eley-Rideal mechanism.

Selective Catalytic Oxidation of Ammonia over Noble Catalysts Supported on Acidic Fe-ZSM5 Supports (산성 Fe-ZSM5 담체에 담지된 귀금속 촉매를 활용한 암모니아의 선택적 산화반응)

  • Kim, Min-Sung;Lee, Dae-Won;Lee, Kwan-Young
    • Clean Technology
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    • v.18 no.1
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    • pp.89-94
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    • 2012
  • In this study, we investigated the activity of Pd and Pt supported on acidic Fe-ZSM5 supports for selective catalytic oxidation of ammonia ($NH_3$-SCO). Among the catalysts, Pt/Fe-ZSM5 catalyst exhibited superior $NH_3$-SCO activity to Pd/Fe-ZSM5 catalyst. We also tested Pt/Fe-ZSM5 catalysts with different Fe loading using ion-exchange method to prepare Fe-ZSM5 supports, which resulted in the increased catalytic performance with smaller Fe content: $NH_3$ was oxidized completely at low temperature ($250^{\circ}C$). The physicochemical properties of Fe-ZSM5 were investigated to figure out the relationship between the characteristics of the catalysts and the catalytic activity on $NH_3$-SCO by Inductively coupled plasma-atomic emissions spectrometer (ICP-AES), $N_2$ sorption, X-ray diffraction (XRD), temperature programmed desorption of $NH_3$ ($NH_3$-TPD) technique.

The Effect of Calcination Temperature of RuTi Catalysts on the Reaction Activity of NH3-SCO (RuTi 촉매의 소성온도가 NH3-SCO 반응활성에 미치는 영향)

  • Shin, Jung Hun;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.31 no.2
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    • pp.200-207
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    • 2020
  • In this study, the effect of calcination temperature on the production of RuTi catalyst in NH3-SCO (selective catalytic oxidation) was investigated. The RuTi catalyst was prepared using the wet impregnation method, and calcined at 400~600 ℃ for 4 h in air condition. The catalysts were named RuTi x00 where x00 means the calcination temperature. According to XRD (X-Ray diffraction), TEM (transmission electron microscope), H2-TPR (H2-temperature programmed reduction) analyses, RuTi x00 catalysts displayed that the dispersion of active metal decreased via increasing the calcination temperature. The catalysts with low dispersion showed a decrease in the surface adsorption oxygen species (Oβ) and NH3 adsorption amount via XPS, and NH3-TPD analyses. Therefore, the RuTi 400 catalyst was well dispersed in the active metal on TiO2 surface, and also, the NH3 removal efficiency was excellent.

Selective Catalytic Oxidation of Ammonia in the Presence of Manganese Catalysts (망간촉매하에서 암모니아의 선택적 산화반응)

  • Jang, Hyun Tae;Park, YoonKook;Ko, Yong Sig;Cha, Wang Seog
    • Korean Chemical Engineering Research
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    • v.46 no.3
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    • pp.498-505
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    • 2008
  • The selective catalytic oxidation of ammonia was carried out in the presence of natural manganese ore (NMO) and manganese as catalysts using a homemade 1/4" reactor at $10,000hr^{-1}$ of space velocity. The inlet ammonia concentration was maintained at 2,000 ppm, with an air balance. The manganese catalyst resulted in a substantial ammonia conversion, with adsorption activation energies of oxygen and ammonia of 10.5 and 22.7 kcal/mol, respectively. Both $T_{50}$ and $T_{90}$, defined as the temperatures where 50% and 90% of ammonia, respectively, are converted, decreased significantly when alumina-supported manganese catalyst was applied. Increasing the manganese weight percent by 15 wt% increased the lower temperature activity, but 20 wt% of manganese had an adverse effect on the reaction results. An important finding of the study was that the manganese catalyst benefits from a strong sulfur tolerance in the conversion of ammonia to nitrogen.

The Selective Catalytic Oxidation of Ammonia: Effect of Physicochemical Properties on Pt/TiO2 (Pt/TiO2 촉매의 물리화학적 특성이 NH3-SCO 반응활성에 미치는 영향)

  • Shin, Jung Hun;Kim, Dong Ho;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.28 no.3
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    • pp.279-285
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    • 2017
  • In this study, the study of the selective catalytic oxidation (SCO) for controlling the $NH_3$ at $200{\sim}350^{\circ}C$ range was investigated. Physicochemical properties of the catalysts were determined using XRD and XPS analysis. In the case of catalytic activity according to thermal treatment condition, the reduction catalyst showed better activity than that of using the calcination catalyst. It was confirmed that the valence state of reduction catalyst was mainly $Pt^{2+}$ and $Pt^0$ as analyzed by XPS. Also, when comparing the reaction activities of $Pt/TiO_2$ catalysts according to the reduction temperature, the $NH_3$ conversion of the catalyst reduced at $700^{\circ}C$ showed the most excellent activity. However, the best activity of $NH_3$ conversion to $N_2$ was obtained for the catalyst reduced at $600^{\circ}C$.

Inhibition Effects of Toxic Solvent Mixture in Catalytic Oxidation Process (유독성 유기용매의 촉매산화공정에서 혼합조성에 따른 간섭효과)

  • 이승범;김원일;홍인권;김형진
    • Journal of environmental and Sanitary engineering
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    • v.16 no.3
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    • pp.72-79
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    • 2001
  • The selective catalytic oxidation of toxic aromatic solvents (benzene, toluene, ethylbenzene, and styrene) and their mixtures were studied on a $Pt/{\;}{\gamma}-Al_2O_3$ catalyst at temperature ranging from $160~350^{\circ}C$. The deep conversion of aromatic solvents was increased as the inlet concentration was decreased and the reaction temperature was increased. The reactivity increases in order benzene > toluene > ethylbenzene > styrene. In mixture, remarkable effects on reaction rate and selectivity have been evidence ; the strongest inhibition effect is shown by styrene and increase in a reverse order with respect to that of reactivity. The inhibition effect was increased in order styrene > ethylbenzene > toluzene > benzene. This trend is due to the competition adsorption between the two or three reactants on the oxidized catalyst. Also, the deep conversion change of benzene was a small in tertiary mixtures(including of benzene and styrene) comparing with conversion characteristics of binary mixture with styrene. This result was due to small concentration of styrene. which had very strong inhibition effect.

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Removal of H2S by Selective Catalytic Oxidation II. Selective Oxidation of H2S on TiO2/SiO2 Catalysts (선택적 촉매 산화 반응에 의한 황화 수소의 제거 II. TiO2/SiO2 촉매 상에서 황화 수소의 선택적 산화 반응)

  • Chun, S.W.;Park, D.W.;Woo, H.C.;Hong, S.S.;Chung, J.S.
    • Applied Chemistry for Engineering
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    • v.7 no.4
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    • pp.645-652
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    • 1996
  • Selective catalytic oxidation of $H_2S$ to elemental sulfur using $TiO_2/SiO_2$ catalysts was investigated in this study. The reaction test with pure $TiS_2$ and $Ti(SO_4)_2$ and cyclic temperature operation revealed that $TiO_2$ had a good resistance to sulfation and sulfidation, which are known as the main cause of catalytic deactivation in sulfur recovery process. With the increase of $TiO_2$ loading amount in $TiO_2/SiO_2$ catalysts, the conversion of $H_2S$ increased and the selectivity of elemental sulfur was very slightly decreased. As the ratio of $O_2/H_2S$ increased, the selectivity to elemental sulfur was drastically decreased. In the presence of 10 vol.% water vapor to a stoichiometric mixture of $H_2S$ and $O_2$($H_2S$= 5 vol.% O=2.5 vol.% ), both activity and selectivity of 10 wt.% $TiO_2/SiO_2$ catalyst are decreased, but it still showed more than 80% of sulfur yield.

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