• Title/Summary/Keyword: TiO2 catalyst

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Kinetic Study of the Visible Light-Induced Sonophotocatalytic Degradation of MB Solution in the Presence of Fe/TiO2-MWCNT Catalyst

  • Zhang, Kan;Oh, Won-Chun
    • Bulletin of the Korean Chemical Society
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    • v.31 no.6
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    • pp.1589-1595
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    • 2010
  • In order to effective degradation of organic dye both under visible light or ultrasonic irradiation, the MWCNTs (multiwalled carbon nanotube) deposited with Fe and $TiO_2$ were prepared by a modified sol-gel method. The Fe/$TiO_2$-MWCNT catalyst was characterized by surface area of BET, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) and ultraviolet-visible (UV-vis) spectroscopy. The low intensity visible light and low power ultrasound was as an irradiation source and the methylene blue (MB) was choose as the model organic dye. Then degradation experiments were carried out in present of undoped $TiO_2$, Fe/$TiO_2$ and Fe/$TiO_2$-MWCNT catalysts. Through the degradation of MB solution, the results showed the feasible and potential use of Fe/$TiO_2$-MWCNT catalyst under visible light and ultrasonic irradiation due to the enhanced formation of reactive radicals as well as the possible visible light and the increase of ultrasound-induced active surface area of the catalyst. After addition of $H_2O_2$, the MB degradation rates have been accelerated, especially with Fe/$TiO_2$-MWCNT catalyst, in case of that the photo-Fenton reaction occurred. The sonophotocatalysis was always faster than the respective individual processes due to the more formation of reactive radicals as well as the increase of the active surface area of Fe/$TiO_2$-MWCNT catalyst.

The Studies on the Thermal Resistant Properties of $WO_3/TiO_2$ and $V_2O_5-WO_3/TiO_2$ Catalysts for NOx Reduction of Flue Gases from Industrial Boiler and on Catalyst Surface Acid Characteristics (産業用 보일러의 燃燒 排가스 中 NOx 處理를 위한 SCR 用 $WO_3/TiO_2$$V_2O_5/TiO_2$ 觸媒들의 耐熱特性과 表面 酸特性에 關한 硏究)

  • 이중범;임상윤;정석진;성준용
    • Journal of Korean Society for Atmospheric Environment
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    • v.6 no.1
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    • pp.31-42
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    • 1990
  • In order to suggest an efficient catalyst systems for NOx reduction of flue gases from industrial boilers, $TiO_2$ supported $WO_3-V_2O_5, V_2O_5$ and $WS_2$ catalysts were tested for the performances of NOx reduction at high reactin temperature range (250-500$^\circ$C) using a simulated flue gas system. It was found that while the proposed $WO_3/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts showed a significant high NOx reduction efficiency at about 350-400$^\circ$C, the conventional commercial catalyst of $V_2O_5/TiO_2$ showed a significant drop in NOx reduction efficiency due to the excessive $NH_3$ oxidation. From the measurement of surface acidities of those catalysts, it was found that the acidity are well correlated with the activities of NOx reduction. The reason of high activity of $WO_3$ series catalysts at high reaction temperature seems due to the low value of surface excess oxygen compared with that of $V_2O_5/TiO_2$ seems equivalent to the acid site of that catalyst.

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The Formation of ConTiOn+2 Compounds in CoOx/TiO2 Catalysts and Their Activity for Low-Temperature CO Oxidation (CoOx/TiO2 촉매상에 ConTiOn+2 화합물의 생성과 저온 CO 산화반응에 대한 촉매활성)

  • Kim, Moon-Hyeon;Ham, Sung-Won
    • Journal of Environmental Science International
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    • v.17 no.8
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    • pp.933-941
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    • 2008
  • The formation of $Co_nTiO_{n+2}$ compounds, i.e., $CoTiO_3$ and $CO_2TiO_4$, in a 5wt% $CoO_x/TiO_2$ catalyst after calcination at different temperatures has been characterized via scanning electron microscopy (SEM), Raman and X-ray photoelectron spectroscopy (XPS) measurements to verify our earlier model associated with $CO_3O_4$ nanoparticles present in the catalyst, and laboratory-synthesized $Co_nTiO_{n+2}$ chemicals have been employed to directly measure their activity profiles for CO oxidation at $100^{\circ}C$. SEM measurements with the synthetic $CoTiO_3$ and $CO_2TiO_4$ gave the respective tetragonal and rhombohedral morphology structures, in good agreement with the earlier XRD results. Weak Raman peaks at 239, 267 and 336 $cm^{-1}$ appeared on 5wt% $CoO_x/TiO_2$ after calcination at $570^{\circ}C$ but not on the catalyst calcined at $450^{\circ}C$, and these peaks were observed for the $Co_nTiO_{n+2}$ compounds, particularly $CoTiO_3$. All samples of the two cobalt titanate possessed O ls XPS spectra comprised of strong peaks at $530.0{\pm}0.1$ eV with a shoulder at a 532.2-eV binding energy. The O ls structure at binding energies near 530.0 eV was shown for a sample of 5 wt% $CoO_x/TiO_2$, irrespective to calcination temperature. The noticeable difference between the catalyst calcined at 450 and $570^{\circ}C$ is the 532.2 eV shoulder which was indicative of the formation of the $Co_nTiO_{n+2}$ compounds in the catalyst. No long-life activity maintenance of the synthetic $Co_nTiO_{n+2}$ compounds for CO oxidation at $100^{\circ}C$ was a good vehicle to strongly sup port the reason why the supported $CoO_x$ catalyst after calcination at $570^{\circ}C$ had been practically inactive for the oxidation reaction in our previous study; consequently, the earlier proposed model for the $CO_3O_4$ nanoparticles existing with the catalyst following calcination at different temperatures is very consistent with the characterization results and activity measurements with the cobalt titanates.

$TiO_2$-Ni inverse Catalyst for CRM Reactions with High Resistance to Coke Formation

  • Seo, Hyun-Ook;Sim, Jong-Ki;Kim, Kwang-Dae;Kim, Young-Dok;Lim, Dong-Chan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.267-267
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    • 2012
  • $TiO_2$-Ni inverse catalysts were prepared using atomic layer deposition (ALD) process and catalytic $CO_2$ reforming of methane (CRM) reaction over catalysts (either bare Ni or $TiO_2$ coated-Ni particles) were performed using a continuous flow reactor at $800^{\circ}C$. $TiO_2$-Ni inverse catalyst showed higher catalytic reactivity at initial stage of CRM reactions at $800^{\circ}C$ comparing to bare Ni catalysts. Moreover, catalytic activity of $TiO_2$/Ni catalyst was kept high during 13 hrs of the CRM reactions at $800^{\circ}C$, whereas deactivation of bare Ni surface was started within 1hr under same conditions. The results of surface analysis using SEM, XPS, and Raman showed that deposition of graphitic carbon was effectively suppressed in a presence of $TiO_2$ nanoparticles on Ni surface, thereby improving catalytic reactivity and stability of $TiO_2$/Ni catalytic systems. We suggest that utilizing decoration effect of metal catalyst with oxide nanoaprticles is of great potential to develop metal-based catalysts with high stability and reactivity.

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V2O5WO3/TiO2 Catalyst Prepared on Nanodispersed TiO2 for NH3-SCR: Relationship between D ispersed Particle Size of TiO2 and Maximum Decomposition Temperature of NOx (NH3-SCR용 나노분산 TiO2 담체상에 제조된 V2O5WO3/TiO2 촉매: TiO2 분산입도와 NOx 최대 분해온도와의 상관성)

  • Min Chae, Seo;Se-Min, Ban;Jae Gu, Heo;Yong Sik, Chu;Kyung-Seok, Moon;Dae-Sung, Kim
    • Korean Journal of Materials Research
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    • v.32 no.11
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    • pp.496-507
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    • 2022
  • For the selective catalytic reduction of NOx with ammonia (NH3-SCR), a V2O5WO3/TiO2 (VW/nTi) catalyst was prepared using V2O5 and WO3 on a nanodispersed TiO2 (nTi) support by simple impregnation process. The nTi support was dispersed for 0~3 hrs under controlled bead-milling in ethanol. The average particle size (D50) of nTi was reduced from 582 nm to 93 nm depending on the milling time. The NOx activity of these catalysts with maximum temperature shift was influenced by the dispersion of the TiO2. For the V0.5W2/nTi-0h catalyst, prepared with 582 nm nTi-0h before milling, the decomposition temperature with over 94 % NOx conversion had a narrow temperature window, within the range of 365-391 ℃. Similarly, the V0.5W2/nTi-2h catalyst, prepared with 107 nm nTi-2h bead-milled for 2hrs, showed a broad temperature window in the range of 358~450 ℃. However, the V0.5W2/Ti catalyst (D50 = 2.4 ㎛, aqueous, without milling) was observed at 325-385 ℃. Our results could pave the way for the production of effective NOx decomposition catalysts with a higher temperature range. This approach is also better at facilitating the dispersion on the support material. NH3-TPD, H2-TPR, FT-IR, and XPS were used to investigate the role of nTi in the DeNOx catalyst.

The Effect of Vanadium(V) Oxide Content of V2O5-WO3/TiO2 Catalyst on the Nitrogen Oxides Reduction and N2O Formation (질소산화물 환원과 N2O 생성에 있어서 V2O5-WO3/TiO2 촉매의 V2O5 함량 영향)

  • Kim, Jin-Hyung;Choi, Joo-Hong
    • Korean Chemical Engineering Research
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    • v.51 no.3
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    • pp.313-318
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    • 2013
  • In order to investigate the effect of $V_2O_5$ loading of $V_2O_5-WO_3/TiO_2$ catalyst on the NO reduction and the formation of $N_2O$, the experimental study was carried out in a differential reactor using the powder catalyst. The NO reduction and the ammonia oxidation were, respectively, investigated over the catalysts compose of $V_2O_5$ content (1~8 wt%) based on the fixed composition of $WO_3$ (9 wt%) on $TiO_2$ powder. $V_2O_5-WO_3/TiO_2$ catalysts had the NO reduction activity even under the temperature of $200^{\circ}C$. However, the lowest temperature for NO reduction activity more than 99.9% to treat NO concentration of 700 ppm appeared at 340 with very limited temperature window in the case of 1 wt% $V_2O_5$ catalyst. And the temperature shifted to lower one as well as the temperature window was widen as the $V_2O_5$ content of the catalyst increased, and finally reached at the activation temperature ranged $220{\sim}340^{\circ}C$ in the case of 6 wt% $V_2O_5$ catalyst. The catalyst of 8 wt% $V_2O_5$ content presented lower activity than that of 8 wt% $V_2O_5$ content over the full temperature range. NO reduction activity decreased as the $V_2O_5$ content of the catalyst increased above $340^{\circ}C$. The active site for NO reduction over $V_2O_5-WO_3/TiO_2$ catalysts was mainly related with $V_2O_5$ particles sustained as the bare surface with relevant size which should be not so large to stimulate $N_2O$ formation at high temperature over $320^{\circ}C$ according to the ammonia oxidation. Currently, $V_2O_5-WO_3/TiO_2$ catalysts were operated in the temperature ranged $350{\sim}450^{\circ}C$ to treat NOx in the effluent gas of industrial plants. However, in order to save the energy and to reduce the secondary pollutant $N_2O$ in the high temperature process, the using of $V_2O_5-WO_3/TiO_2$ catalyst of content $V_2O_5$ was recommended as the low temperature catalyst which was suitable for low temperature operation ranged $250{\sim}320^{\circ}C$.

Properties of Low-Temperature Sol-Gel TiO2 Thin Films with Catalyst Content (졸-겔법으로 제작된 저온 TiO2 박막의 촉매농도에 따른 광분해 특성 분석)

  • Hong, Hyun-Joo;Heo, Min-Chan;Hahn, Sung-Hong;Kim, Eui-Jung;Lee, Chung-Woo;Joo, Jong-Hyun
    • Korean Journal of Optics and Photonics
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    • v.17 no.3
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    • pp.296-302
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    • 2006
  • ILow-temperature $TiO_2$ sol was synthesized with various catalyst contents by using a sol-gel method. $TiO_2$ thin films were produced by a dip-coating method and their optical, structural and photocatalytic properties were examined. Transmittance of $TiO_2$ thin films with 0.10 mol, 0.25 mol, 0.50 mol and 0.75 mol catalyst content showed high transmittance in the visible range. XRD results showed the anatase-to-rutile phase transition was accelerated with increasing catalyst content and the crystallinity size of the $TiO_2$ thin films increased with increasing catalyst content. SEM results indicated that the particle size of the $TiO_2$ thin films was the smallest with catalyst content of 0.25 mol. Photocatalytic results showed that methylene blue was completely decomposed in the presence of anatase film prepared with 0.10 mol, 0.25 mol and 0.50 mol catalyst content.

A Study on the H2 Oxidation over Pt/TiO2, SO2 Poisoning and Regeneration (Pt/TiO2의 HS 산화반응 및 SO2 피독과 재생 방안 연구)

  • Lee, Dong Yoon;Kim, Sung Su
    • Applied Chemistry for Engineering
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    • v.30 no.6
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    • pp.731-736
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    • 2019
  • In this article, Pt/TiO2 was manufactured in the form of powder and honeycomb, and the influence of SO2, which is a poisonous substance to catalyst, and regeneration method were investigated. The catalytic activity of Pt/TiO2 before and after the exposure to SO2 was also compared. The initial activity of Pt/TiO2 was proportional to the injected H2 concentration (1~5%). And the optimum temperature of the catalyst and conversion rate of H2 were 183 ℃ and 95%, respectively. It was confirmed that when exposing 2,800 ppm of SO2 to the powder and honeycomb Pt/TiO2, the performance of catalyst was not measurable and also 0.69% sulfur (S) remained on the catalyst surface. As a result of the cleaning and heat treatment for the poisoning catalyst, the activity of the powder catalyst exhibited a conversion rate of H2 greater than 96%. Whereas, the honeycomb catalyst showed a conversion rate of H2 greater than 95% when it was regenerated through the heat treatment of H2 or air atmosphere.

A Study on Oxidative Decomposition of CFC-113 over TiO2-SiO2 Catalysts Prepared by the Sol-Gel Method (솔-젤법으로 제조된 TiO2-SiO2 촉매상에서 CFC-113의 산화분해반응에 관한 연구)

  • Chang, Won-Chul;Lee, Doo-Hyoung;Lee, Tae-Jin
    • Applied Chemistry for Engineering
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    • v.10 no.7
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    • pp.963-968
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    • 1999
  • The global environmental problems have been caused by the release of CFCs. Therefore, methods for safe destruction of recoverd CFCs will be eventually needed. The objective of this study was to develop and test a catalyst operating at a mild condition for the decomposition of CFC-113. In this work, catalytic oxidative decomposition of CFC-113 was carried out over aerosol $TiO_2/SiO_2(ATS)$ catalysts prepared by the sol-gel method. All ATS catalysts(Ti/Si mol ratio=1, 2, 2.33, 4) showed high initial activity. However, the deactivation of ATS catalysts was found that more remarkable due to an attack of fluorine and the destruction of ATS structure(Si-F reaction) from analyses of SEM-EDX, XRD than $TiO_2/SiO_2(ATS)$ catalyst prepared by the precipitation method. ATS catalysts prepared by more acidic prehydrolysis condition were found to have still more activity and longer life-time by increasing of acidity. The activity of ATS catalyst also depend on the content of $TiO_2$. There was reason that the acidity of the ATS catalyst was increased with the increased content of $TiO_2$ from 50 to 80 mol %. Solid superacid catalyst ($ATX/SO_4{^{2-}}$) modified with $H_2SO_4$ solution was prepared for high activity and lower deactivation. The reaction of $ATS/SO_4{^{2-}}$ catalyst also exhibited even higher activity and lower deactivation than the original ATS catalyst. It is suggested that the addition of the sulphate species clearly inhibit the deactivation.

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Performance of V2O5-TiO2 Catalyst Prepared by Various Methods for Removal of Hydrogen Sulfide Emitted from Steel Smelting Process (다양한 제조방법으로 제조된 V2O5-TiO2 촉매를 이용한 제련공정에서 발생한 황화수소 제거능 비교)

  • Kim, Moon il
    • Journal of Environmental Science International
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    • v.30 no.6
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    • pp.501-505
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    • 2021
  • V2O5-TiO2 catalysts were prepared by various methods. V2O5-TiO2 were prepared by sol-gel method with different drying conditions (aerogel and xerogel), and V2O5 supported on TiO2 obtained by sol-gel method with precipitation-deposition method and impregnation method. The performance of the V2O5-TiO2 catalysts was investigated for the selective oxidation of hydrogen sulfide in the stream containing both ammonia and excess water. All the catalysts showed good dispersion of vanadium and they had high H2S conversion with no or little production of sulfur dioxide. The V2O5-TiO2 aerogel catalyst prepared by sol-gel method with drying under super critical condition had the highest surface area which led to better catalytic activity compared to those by other synthesis methods.