• Title/Summary/Keyword: N $O_{}$ x/

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Nucleophilic Substitution Reactions of O-Methyl N,N-Diisopropylamino Phosphonochloridothioate with Anilines and Pyridines

  • Barai, Hasi Rani;Lee, Hai Whang
    • Bulletin of the Korean Chemical Society
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    • v.35 no.4
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    • pp.1016-1022
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    • 2014
  • The kinetic studies on the reactions of O-methyl N,N-diisopropylamino phosphonochloridothioate with X-anilines and X-pyridines have been carried out in acetonitrile. The free energy relationship with X in the anilines exhibits biphasic concave upwards with a break region between X = (H and 4-F), giving unusual negative ${\beta}_X$ and positive ${\rho}_X$ values with weakly basic anilines. The unusual phenomenon is rationalized by isokinetic relationship. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the selectivity parameter and variation trend of the deuterium kinetic isotope effects with X. The free energy relationship with X in the pyridines exhibits biphasic concave upwards with a break point at X = 3-MeO. A concerted mechanism is proposed based on relatively small ${\beta}_X$ value, and frontside and backside nucleophilic attack are proposed with strongly and weakly basic pyridines, respectively.

Selective Catalytic Reduction of NO by H2 over Pt-MnOx/ZrO2-SiO2 Catalyst (Pt-MnOx/ZrO2-SiO2 촉매에서 수소에 의한 일산화질소의 선택적 촉매 환원반응)

  • Kim, Juyoung;Ha, Kwang;Seo, Gon
    • Korean Chemical Engineering Research
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    • v.52 no.4
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    • pp.443-450
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    • 2014
  • Selective catalytic reduction of nitrogen monoxide by hydrogen ($H_2$-SCR of NO) over platinum catalysts impregnated on zirconia-incorporated silica ($ZrO_2-SiO_2$) and manganese oxide ($MnO_x$) was investigated. $Pt-MnO_x$ catalyst showed low conversions and low yields of $N_2O$ and $NO_2$ at $100{\sim}350^{\circ}C$. On the other hand, NO conversions over $Pt/ZrO_2-SiO_2$ were very high, but $N_2O$ was predominantly produced at $100-150^{\circ}C$ and the yield of $NO_2$ increased with temperature at $200-300^{\circ}C$, resulting in poor $N_2$ yields. $Pt-MnO_x/ZrO_2-SiO_2$ exhibited a small enhancement in $N_2$ yield at $100-150^{\circ}C$ due to the synergy of $MnO_x$ and $ZrO_2-SiO_2$. The surface composition and oxidation state of the catalyst components and the acidity of the catalysts were examined. IR spectra of the adsorption of NO and their subsequent reactions with hydrogen on these catalysts were also recorded. The variations of conversion and product yield according to the catalyst components in the $H_2$-SCR of NO were discussed in relation to their catalytic roles.

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.

The preparation of ${SiO_x}{N_y}$ thin films by reactive RF sputtering method (고주파 반응성 스퍼터링법에 의한 ${SiO_x}{N_y}$ 박막의 제작)

  • 조승현;최영복;김덕현;정성훈;문동찬;김선태
    • Korean Journal of Optics and Photonics
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    • v.11 no.1
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    • pp.13-18
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    • 2000
  • The SiOxNy thin films were prepared on Si(lOO) by reactive RF sputtering method. The reactive gas ratio and the power were used as parameters for depositing SiOxNy thin fims. The properties of ${SiO_x}{N_y}$ thin tilms were investigated by XRD, XPS, refractive index and extinction coefficient analyzer (n'||'&'||'k analyzer), and FfIR. It was found by the results of the x-ray diffraction measurement that SiOxNy thin films were grown to an amorphous structure. From the results of the XPS, and the n'||'&'||'k analyzer, it was found that refractive index was intended to increase with the increasement of the relative nitrogen contents of the ${SiO_x}{N_y}$ thin films.

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INVERSE SYSTEM AND ARTINIAN O-SEQUENCES OF CODIMENSION 4

  • Shin, Dong-Soo
    • Journal of applied mathematics & informatics
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    • v.25 no.1_2
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    • pp.513-518
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    • 2007
  • There is a one to one correspondence between Artinian algebras $k[x_1,...,x_n]/Ann(M)$ and finitely generated $k[x_1,...,x_n]-submodules$ M of $k[y_1,...,y_n]$ by Inverse System. In particular, any Artinian level algebra $k[x_1,...,x_n]/Ann(M)$ can be obtained when M is finitely generated by only maximal degree generators. We prove that H = (1, 4, 8, 13,..., 27, 8, 2) is not a level Artinian O-sequence using this inverse system.

Formation of N2O in NH3-SCR DeNOxing Reaction with V2O5/TiO2-Based Catalysts for Fossil Fuels-Fired Power Stations (화력발전소용 V2O5/TiO2계 촉매상에서 NH3-SCR 탈질반응으로부터의 N2O 생성)

  • Kim, Moon Hyeon
    • Korean Chemical Engineering Research
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    • v.51 no.2
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    • pp.163-170
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    • 2013
  • Selective catalytic reduction of $NO_x$ by $NH_3$ ($NH_3$-SCR) over $V_2O_5/TiO_2$-based catalysts is recently reported to be an anthropogenic emitter of $N_2O$ that is a global warming gas with a global warming potential of 310. Therefore, this review will get a touch on significance of some parameters regarding $N_2O$ formation in the $deNO_xing$ reaction for fossil fuels-fired power plants applications. The $N_2O$ production in $NH_3$-SCR reaction with such catalysts occurs via side reactions between $NO_x$ and $NH_3$ in addition to $NH_3$ oxidation, and the extent of these undesired reactions depends strongly on the loadings of $V_2O_5$ as a primary active component and the promoter as a secondary one ($WO_3$ and $MoO_3$) in the SCR catalysts, the feed and operating variables such as reaction temperature, $NO_2/NO_x$ ratio, oxygen concentration, gas hourly space velocity, water content and thermal excursion, and the physical and chemical histories of the catalysts on site. Although all these parameters are associated with the $N_2O$ formation in $deNO_xing$ reaction, details of some of them have been discussed and a better way of suppressing the $N_2O$ production in commercial SCR plants has been proposed.

An empirical study on the X-ray attenuation capability of n-WO3/n-Bi2O3/PVA with added starch

  • Oliver, Namuwonge;Ramli, Ramzun Maizan;Azman, Nurul Zahirah Noor
    • Nuclear Engineering and Technology
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    • v.54 no.9
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    • pp.3459-3469
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    • 2022
  • Matrix composites of n-WO3/n-Bi2O3/PVA with different loadings of n-WO3/n-Bi2O3 mixtures (0-15 wt%) and starch (0 and 3 wt%) were fabricated by using melt-mixing method. The X-ray attenuation capability were evaluated based on mass attenuation coefficient (μ/⍴) using a general diagnostic X-ray machine at 40-100 kVp. The effect of starch addition on the dispersion of the fillers in the PVA matrix were observed by using FESEM through morphological analysis. The fabricated samples have shrunken and caused their thickness to be decreased (0.35 mm-0.55 mm) after the drying process even though fixed thickness (2.0 mm) was set initially. The density and HVL values of the samples with 3 wt% starch was seen lower than samples without starch (0 wt%), however the former have provided improvement in filler dispersion and better X-ray attenuation capability compared to the latter. As conclusion, the matrix composite of n-WO3/n-Bi2O3/PVA with 15 wt% of n-Bi2O3, 8 wt% of n-WO3 and 3 wt% starch can be selected as the best promising candidate for X-ray shielding materials.

$NO_x$ Chemistry Over Rutile $TiO_2$(110) Surfaces

  • Kim, Yu-Gwon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.131-131
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    • 2012
  • We present our recent temperature-programmed desorption (TPD) study on catalytic reductions of $NO_x$ such as NO, $NO_2$, and $N_2O$ over rutile $TiO_2$(110) surfaces. Our results indicate that $NO_2$/NO readily reacts to give NO/$N_2O$ desorption at the substrate temperature as low as 100 K/70 K. Interestingly, $N_2O$, however, does not dissociate into $N_2$ and $O_{BBO}$ over the oxygen vacancy on the $TiO_2$(110) surface. Successive reduction of NO and $NO_2$ into $N_2O$ and NO, respectively, leaves oxygen atoms on the $TiO_2$(110) surface in a form of $O_{ad}$, which can induce additional reductive channels of NO and $NO_2$ at higher temperatures up to 400 K. During the repeated TPD cycles of $NO_x$, our x-ray photoelectron spectroscopy (XPS) analysis indicates that no N atom accumulates on the $TiO_2$ surface.

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On The Size of The Subgroup Generated by Linear Factors (선형 요소에 의해 생성된 부분그룹의 크기에 관한 연구)

  • Cheng, Qi;Hwang, Sun-Tae
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.45 no.6
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    • pp.27-33
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    • 2008
  • Given a polynomial ${\hbar}(x){\in}F_q[x]$ of degree h, it is an important problem to determine the size of multiplicative subgroup of $\(F_q[x]/({\hbar(x))\)*$ generated by $x-s_1,\;x-s_2,\;{\cdots},\;x-s_n$, where $\{s_1,\;s_2,\;{\cdots},\;s_n\}{\sebseteq}F_q$, and for all ${\hbar}(x){\neq}0$. So far the best known asymptotic lower bound is $(rh)^{O(1)}\(2er+O(\frac{1}{r})\)^h$, where $r=\frac{n}{h}$ and e(=2.718...) is the base of natural logarithm. In this paper, we exploit the coding theory connection of this problem and prove a better lower bound $(rh)^{O(1)}\(2er+{\frac{e}{2}}{\log}r-{\frac{e}{2}}{\log}{\frac{e}{2}}+O{(\frac{{\log}^2r}{r})}\)^h$, where log stands for natural logarithm We also discuss about the limitation of this approach.

Calculation of the Dipole Moments for Octahedral $[M(II)Cl_2O_2N_2]$ Square Planar and Tetrahedral $[Pd(Ⅱ)X_2Y_2]$ Type Complexes [M(Ⅱ) = Ni(Ⅱ) or Co(Ⅱ), X = N and Y = O or S] (팔면체 $[M(II)Cl_2O_2N_2]$, 사각형 및 사면체 $[Pd(Ⅱ) X_2Y_2]$형태 착물의 쌍극자모멘트의 계산 [M(Ⅱ) = Ni(Ⅱ) 또는 Co(Ⅱ), X = N 그리고 Y = O 또는 S])

  • Ahn Sangwoon
    • Journal of the Korean Chemical Society
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    • v.23 no.2
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    • pp.59-64
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    • 1979
  • The dipole moments for octahedral $[M(II)Cl_2N_2O_2]$, square planar and tetrahedral $[Pd(II)X_2Y_2]$ type complexes are calculated, using the approximate molecular orbital theory [M(II) = Ni(II) or Co(II), X = N and Y = O or S]. The calculated dipole moments for these complexes are in reasonable agreement with the experimental values. The possible structures for these complexes are investigated on the basis of the calculated dipole moments.

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