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51.
A. Goifman J. Gun V. Gitis A. Kamyshny Jr. O. Lev J. Donner H. Brnick E. Worch 《Applied catalysis. B, Environmental》2004,54(4):225-235
Pyrolysed carbon supported cobalt porphyrin, an electrocatalyst that is frequently used for oxygen reduction in fuel cells, is evaluated for catalytic oxidation of hydrogen sulfide by dissolved dioxygen. The catalyst performs best after heat treatment at 880 °C, at pH 8. Analysis of the reaction products reveals that sulfur is the dominant product throughout the investigated pH range 5–10. The catalyst performs much better than powdered activated carbon, granular activated carbon and different other forms of unmodified carbon catalysts. This is as far as we know the first time that heat treated cobalt porphyrins are evaluated for non-electrocatalytic applications. 相似文献
52.
Na-oyoshi Iwasaki Takanori Miyake Eriko Yagasaki Toshimitsu Suzuki 《Catalysis Today》2006,111(3-4):391-397
Attention has been increasingly paid to the partial oxidation of lower alkanes to synthesis gas, due to its intrinsic energy saving process. We studied the partial oxidation of ethane (POE) on Co loaded on various supports. The POE performance varied as follows: Y2O3, CeO2, ZrO2, La2O3 SiO2, Al2O3, TiO2 > MgO. Comparing Y2O3 and CeO2, the carbon deposition during the POE was negligible on CeO2 and therefore CeO2 was the most preferable support. By changing space velocity and O2 partial pressure, reaction mechanism of POE was studied and it was revealed that two-step mechanism was prevailing; combustion of ethane to H2O and CO2 and subsequent reforming of ethane with H2O and CO2 to synthesis gas. Co/CeO2 catalyst exhibited high and stable catalytic activity for 10 h; high ethane conversion of 18% (maximum ethane conversion 20% at O2/C2H6 = 0.2) with H2 and CO selectivities of 93 and 84%, respectively. 相似文献
53.
54.
提出应用甲醛肟分光光度法测定原水中微量金属锰含量的方法,并对可能的干扰进行了讨论,对方法的精密度和准确度进行实验。此方法准确,简便,适用于公司竹浆生产选择含氧漂白工艺生产控制分析。 相似文献
55.
在稀硫酸(或稀盐酸)溶液中,用闪锌矿(或方铅矿)精矿作还原剂,用可溶性铁盐作催化剂,分解软锰矿(或大洋锰结核矿),同时制取锰盐和锌盐。该工艺具有反应快速、彻底,工艺流程简单等特点,同时省去了软锰矿的还原焙烧和锌(铅)精矿的氧化焙烧,能够大幅度提高锰、锌(铅)矿的浸出率,对原料矿的品级没有严格要求。 相似文献
56.
57.
掺锰BaTiO3 PTCR陶瓷的电子顺磁共振研究 总被引:2,自引:1,他引:2
利用电子顺磁共振(EPR)方法对Mn掺杂的BaTiO3 PTCR陶瓷在120-450K的温度范围内进行了研究,研究结果表明:高自旋Mn^2 离子的6重谱线非常明显,表征谱线位置的g因子为2.009 9,Mn^2 离子信号弱弱与BaTiO3晶体结构密切相关,Mn^2 离子信号的温度分布呈U型,即在三方相和立方相时,信号强度较强,而在四方相和斜方相时信号很弱,这是因为在四方相和斜方相中,由于BaTiO3晶体结构的扭曲和畸变,导致Mn^2 和Vo空位缔合生成Mn^2 -Vo复合缺陷,未成对电子的消失以及复合缺陷n^2 -Vo的生成最Mn^2 在四方相和斜方相(200-380K)消失的主因,实验中没有发现Mn^3 和Mn^4 的信号,而与实验的环境条件一致,掺Mn后样品Curie点的漂移可能是Mn进入晶格的一个判据,此外,由于试样的n(Ba)/n(Ti)=1,因而没有发现钡空位VBa及其它的复合缺陷(如:VBa-Mn^2 ,Mn^3 -Vo,La^3 -Mn^3 等),Mn^2 离子等电子陷阱的生长是Curie温度处电阻骤然增加的主要原因。 相似文献
58.
Z. Benzo T. Zoltan M. Murillo M. Quintal J. Salas E. Marcano C. Gómez 《Journal of the American Oil Chemists' Society》2006,83(5):401-405
An emulsion-based method was developed as an alternative for the introduction of oil-based samples into a graphite furnace
to produce a more rapid, precise, and accurate method of analysis. The combination of emulsion sampling and electrothermal
atomization for atomic absorption spectroscopy was developed and then applied to the determination of Ni and manganese in
neem oil from Venezuela. The optimal concentration of neem oil in the emulsion was 30 and 4% for Ni and Mn, respectively,
based on the metal concentration of the neem oil. The stability of the emulsion as a function of time was evaluated. The use
of aqueous calibration solutions and the accuracy attained using this method make it attractive for the analysis of oil samples.
The metal recovery was between 97 and 101%. Based on the emulsion method, the neem oil samples had 1.39 and 0.21 mg of Mn
and Ni per kg of oil, respectively. The wet digestion method indicated a Mn and Ni concentration in the neem oil sample of
1.42 and 0.24 mg/kg, respectively. 相似文献
59.
Cobalt sulphide catalyst prepared via a new method involving the precipitation reaction between cobaltous acetate and ammonium sulphide solutions has been shown to be favourably active for the catalytic decomposition of H2S when compared with data for other transition metal sulphides.
The BET surface area of this unsupported catalyst is about an order of magnitude higher than cobalt sulphide formed by direct sulphidation of cobalt oxide with H2S gas. XRD, SEM and TEM analyses were used to obtain bulk composition and morphological characteristics. Catalyst specimen calcined at 823 K showed the best activity.
The kinetics of the decomposition reaction has been studied over this new preparation. Experiments conducted at atmospheric pressure between 933-983 K using about 11 feed compositions showed that below 40% H2S/Ar the reaction was essentially 1st order with respect to H2S partial pressure. Beyond this point, rate remained invariant with feed composition. A mechanism involving catalysis via co-ordinative unsaturation sites on the CoS was proposed and kinetic model based on the cleavage of the surface H-S bond as the rate-determining step appeared to be the most adequate representation of the rate data. Hydrogen production rates at all temperatures also paralleled the behaviour seen for H2S decomposition. Activation energy for H2S decomposition and H2 production rates were estimated as 111 kJ mol-1 and 88 kJ mol-1 respectively 相似文献
The BET surface area of this unsupported catalyst is about an order of magnitude higher than cobalt sulphide formed by direct sulphidation of cobalt oxide with H2S gas. XRD, SEM and TEM analyses were used to obtain bulk composition and morphological characteristics. Catalyst specimen calcined at 823 K showed the best activity.
The kinetics of the decomposition reaction has been studied over this new preparation. Experiments conducted at atmospheric pressure between 933-983 K using about 11 feed compositions showed that below 40% H2S/Ar the reaction was essentially 1st order with respect to H2S partial pressure. Beyond this point, rate remained invariant with feed composition. A mechanism involving catalysis via co-ordinative unsaturation sites on the CoS was proposed and kinetic model based on the cleavage of the surface H-S bond as the rate-determining step appeared to be the most adequate representation of the rate data. Hydrogen production rates at all temperatures also paralleled the behaviour seen for H2S decomposition. Activation energy for H2S decomposition and H2 production rates were estimated as 111 kJ mol-1 and 88 kJ mol-1 respectively 相似文献
60.
A self-assembled monolayer (SAM) of a novel cobalt(II)porphyrin disulphide derivative was prepared on flat gold(1 1 1) electrode. Evidence for surface modification was provided by electrochemical reductive desorption of the monolayer and ellipsometry, consistent with a coverage of 2.5 × 10−10 mol cm−2 and a thickness of 13 Å, respectively. Both results support the presence of SAMs where the molecules share an intermediate position between perpendicular and flat orientation. Scanning tunnelling microscopy have also proven the formation of CoPSS SAMs, however high-resolution images could only be obtained when the CoPSS molecules were diluted in an hexanethiol SAM. The electrocatalytic activity of the surface confined Co-porphyrin was evaluated for the oxygen reduction. Voltammetric data indicate that reaction involves two electrons consistent with the formation of hydrogen peroxide. Under similar experimental conditions the data obtained for an iron-porphyrin analogue points for a full reduction of dioxygen to water. 相似文献