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1.
The results of the influence of alkaline earth metal and magnesium cations on the activity and sulfur stability of catalysts based on synthetic mordenites and high-silicon zeolites with pentasil structures on the selective reduction of nitrogen oxides with C3−C4 hydrocarbons are presented. Doping the H-form of mordenite and pentasils with Ca, Sr, Ba, and Mg cations increased their activity and stability with respect to sulfur dioxide in the selective reduction of NOx with a propane-butane mixture. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 5, 317–321, September–October, 1999.  相似文献   

2.
The results of a search for optimum conditions for the modification of natural mordenites and the results of an investigation of their acidic characteristics by temperature programmed desorption of ammonia for the purpose of producing active and sulfur-resistant catalysts for the selective reduction of NOx by lower hydrocarbons (C1−C4) are presented. It was shown that during the chemical modification of samples of mordenite-bearing rock, including acid treatment with 0.25–0.5 N sulfuric acid solutions, recationization, and subsequent decationization, the concentration of strong acid centers increases. Here the activity of the catalysts and the resistance to the effect of SO2 in the selective reduction of NOx to nitrogen by a propane-butane mixture are increased. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 125–129, March–April, 1999.  相似文献   

3.
Toward achieving selective catalytic reduction of NO x by hydrocarbons at low temperatures (especially lower than 200 °C), C2H2 selective reduction of NO x was explored on H-mordenite (H-MOR) catalysts in dielectric barrier discharge (DBD) plasma. This work reported significant synergistic effects of DBD plasmas and H-MOR catalysts for C2H2 selective reduction of NO x at low temperatures (100–200 °C ) and across a wide range of O2 content (0–15%). At 100 °C, NO x conversions were 3.3, 11.6 and 66.7% for the plasma alone, catalyst alone and in-plasma catalysis (IPC) cases (with a reactant gas mixture of 500 ppm NO, 500 ppm C2H2, 10% O2 in N2, GHSV = 12,000 h−1 and input energy density of 125 J L 1), respectively. At 200 °C, NO x conversions were 3.8, 54.0 and 91.4% for the above three cases, respectively. Also, strong signals of hydrogen cyanide (HCN) byproduct were observed in the catalyst alone system by an on-line mass spectrometer. By contrast, almost no HCN was detected in the IPC system.  相似文献   

4.
The results from investigation of the processes involved in the catalytic reduction of nitrogen oxides are reviewed: 1) with carbon monoxide and other combustible gases (H2, C n H m ) at a developed block honeycomb palladium-containing catalysts; 2) with ammonia (the SCR process) at vanadium-containing and complex oxide (Cu-Cr, Fe-Cr/-Al2O3) catalysts; 3) with light C1-C4 hydrocarbons at cation-exchange zeolites (pentasils, natural and synthetic mordenites). Mechanisms and kinetic models are proposed, and the regions of a positive and negative effect from oxygen and sulfur dioxide on the processes involved in the reduction of nitrogen oxides are established.  相似文献   

5.
A deNOx catalyst was prepared by wash-coating a cobalt ion exchanged ZSM-5 zeolite together with an alumina binder on a cordierite honeycomb structure. A few types of the Co-ZSM-5 based catalysts were tested for NOx reduction with C2H4 under oxidizing conditions in the temperature range between 250–600°C. Preliminary tests of the catalytic activity of the systems showed NOx reduction up to 95% at temperatures between 400–550°C using a mixture of a synthetic gas and air as reactant.  相似文献   

6.
The combined conversion conditions were examined for the reactions of decomposition and reduction of N2O and NO with C1,C3–C4 hydrocarbons, in particular, in gas mixtures containing oxygen and sulfur dioxide, over Fe- and Co-containing catalysts supported on zeolites and zirconia, as well as on structured honeycomb monoliths.  相似文献   

7.
The interaction of methane with the oxidized surface of the KNaSrCoO3−x is first order in methane with respect to formation of higher hydrocarbons and zero order with respect to formation of CO2. At the initial stage the rate of formation of the reaction products is independent of the amount of oxygen from the catalyst consumed (up to 5–7 monolayers of oxygen), after which the rate of the reaction falls linearly. The overall amount of oxygen consumed in the reaction reaches 30 monolayers. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 3, pp. 182–187, May–June, 2000.  相似文献   

8.
A study was carried out on the effect of the chemical nature of MxLy on the activity and selectivity of bifunctional MxLy/zeolite catalysts, where MxLy are metal-like transition metal compounds, M is a metal atom (Co, Mo, or W), and L is a nonmetal atom (B or Si), in the dehydrocondensation of methane to give higher hydrocarbons in the absence of gas-phase oxidizing agents. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from éksperimental’naya i Teoreticheskaya Khimiya, Vol. 33, pp. 243–247, July–August, 1997.  相似文献   

9.
The kinetics of the heat release during the reactions of aqueous HNO3 withn-heptane andn-octadecane was studied. The kinetic regularities of the reactions of hydrocarbons C7H16−C18H38 with HNO3 and the heats of the reactions were described. At all stages, except initial, the hydrocarbon reacts with NO2 and nitric acid reproduces NO2 in the reaction with NO. The accumulation of NO2 results in the acceleration of the process. When the pressure of the hydrocarbon vapor is equilibrium, its reaction with NO2 can also proceed in the gas phase. The contribution of this reaction to the total heat release was estimated. The additives of aromatic and unsaturated hydrocarbons to aliphatic hydrocarbons increase strongly the initial rate of the heat release and changes slightly the subsequent stages of the process. Naphthenic hydrocarbons have almost no effect on the kinetic parameters of the process. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–40, January, 1998.  相似文献   

10.
The hydrogenation of Co on zirconium dioxide catalysts containing from 0 to 10 mass % iron was studied. Small additions of iron up to about 0.5 mass % promote the ZrO2 catalysts relative to the formation of C2–C4 olefins. In the presence of large iron additives, the catalyst operates as a complex metal-oxide system featuring interaction of its components. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 153–158, May–June, 1997.  相似文献   

11.
The experiments are carried out in the system of continuous flow reactors with dielectric-barrier discharge (DBD) for studies on the conversion of natural gas to C2 hydrocarbons through plasma catalysis under the atmosphere pressure and room temperature. The influence of discharge frequency, structure of electrode, discharge voltage, number of electrode, ratio of H2/CH4, flow rate and catalyst on conversion of methane and selectivity of C2 hydrocarbons are investigated. At the same time, the reaction process is investigated. Higher conversion of methane and selectivity of C2 hydrocarbons are achieved and deposited carbons are eliminated by proper choice of parameters. The appropriate operation parameters in dielectric-barrier discharge plasma field are that the supply voltage is 20–40 kV (8.4–40 W), the frequency of power supply is 20 kHz, the structure of (b) electrode is suitable, and the flow of methane is 20–60 mL · min−1. The conversion of methane can reach 45%, the selectivity of C2 hydrocarbons is 76%, and the total selectivity of C2 hydrocarbons and C3 hydrocarbons is nearly 100%. The conversion of methane increases with the increase of voltage and decreases with the flow of methane increase; the selectivity of C2 hydrocarbons decreases with the increase of voltage and increases with the flow of methane increase. The selectivity of C2 hydrocarbons is improved with catalyst for conversion of natural gas to C2 hydrocarbons in plasma field. Methane molecule collision with radicals is mainly responsible for product formation.  相似文献   

12.
The adsorption of NO, NO/O2 mixtures and NO2 on pure ZrO2 and on two series of catalysts supported on ZrO2, one containing vanadia and the other molybdena (ZV and ZMo, respectively), has been investigated. The V and Mo surface contents of the latter were ≤3 atoms nm−2 and ≤5 atoms nm−2, respectively. All samples had been previously submitted to a standard oxidation treatment. On all samples, only extremely minor amounts of NOx surface species are formed by NO interaction at room temperature (RT). NOx surface species are formed in greater amounts on pure ZrO2 when NO and O2 are coadsorbed at RT; they are mainly nitrites, small amounts of nitrates, and small amounts of (O2NO−H)δ− species; when ZrO2 is warmed to 623 K in the NO/O2 mixture, nitrites decrease, nitrates and (O2NO−H)δ− species increase. The same NOx species as on the ZrO2 surface free from V (or Mo) are formed on ZV (or ZMo) samples with surface V (or Mo) density <1.5 atoms nm−2; however, they occur in decreased amount with increasing V (or Mo) coverage. On ZV samples with a surface V density of 1.5–3 atoms nm−2 (or ZMo samples with a surface Mo density of 1.5–5 atoms nm−2) when NO and O2 are coadsorbed at RT, there is formation of small amounts of nitrites, nitrates (both on ZrO2 surface free from V (or Mo) and at the edges of V- or Mo-polyoxoanions) and NO2 δ+ species, associated with V5+ (or Mo6+) of very strong Lewis acidity; when samples are warmed up 623 K in the NO/O2 mixture, nitrites disappear, nitrates increase, NO2 δ+ species remain constant or slightly decrease. When NO2 is allowed into contact at RT with oxidized samples, surface situations almost identical to those obtained for each sample warmed to 623 K in NO/O2 mixture is reached. The NOx surface species stable at 623 K, the temperature at which catalysts show the best performance in the selective catalytic reduction (SCR) of NO by NH3, are nitrates, both on ZrO2 and on polyvanadates or polymolybdates at high nuclearity. On the contrary, nitrites and NO2 δ+ species are unstable at 623 K.  相似文献   

13.
The catalytic properties of zirconia prepared by different methods with impregnated variable-valence metals (chromium, cobalt, and cerium) as well as rhodium-promoted samples were studied in the reduction of nitrogen oxides by C1 and C3–C4 hydrocarbons and also in the presence of sulfur dioxide. TPDA and IR spectroscopy showed that the different catalytic behavior of the Me x O y /ZrO2 samples is related to their acid properties. The more active samples had strong Brönsted acid sites.  相似文献   

14.
A personalized, miniaturized air sampling system was evaluated to estimate the daily exposure of pediatric asthmatics to nitrogen dioxide (NO2). The lightweight device (170 g) uses a sampling pump connected to a solid sorbent tube containing triethanolamine (TEA)-impregnated molecular sieve. The pump is powered by a 9 V battery and samples air over a 24 h period at a collection rate of 0.100 L/min. After exposure, the solid sorbent is removed from the tubes for spectrophotometric analysis (Griess Assay). The lower detection limit of the overall method for NO2 is 11 μg/m3. The linearity, precision and accuracy of the sampler was evaluated. Different NO2 concentrations generated in the laboratory (range: 50 to 340 μg/m3) were simultaneously measured by the TEA tube samplers and colocated continuous chemiluminescent NOx analyzers (reference method). The coefficient of determination for the laboratory test derived from ordinary linear regression (OLR) was r 2=0.99 (y OLR=0.94x−4.58) and the precision 3.6%. Further, ambient NO2 concentrations in the field (range: 10–120 μg/m3) were verified with continuous chemiluminescent monitors next to the active samplers. Reweighted least squares analysis (RLS) based on the least median squares procedure (LMS) resulted in a correlation of r 2=0.68 for a field comparison in Riverside, CA (y RLS=1.01x−0.94) and r 2=0.92 in Los Angeles, CA (y RLS=1.31x−7.12). The precision of the TEA tube devices was 7.4% (at 20–60 μg/m3 NO2) under outdoor conditions. Data show that the performance of this small active sampling system was satisfactory for measuring environmental concentrations of NO2 under laboratory and field conditions. It is useful for personal monitoring of NO2 in environmental epidemiology studies where daily measurements are desired.  相似文献   

15.
It is shown that palladium–cobalt oxide–cerium catalyst deposited on cordierite catalyzes the reduction of nitrogen(II) oxide with carbon monoxide, and cobalt–iron catalysts in simultaneous reduction of NO + N2O with C3-C4 alkanes retained high activity in the presence of water vapor and sulfur dioxide. The Pd-Co3O4/cordierite catalyst exceeds the Pt-Co3O4/codierite catalyst in the conversion of NO and CO in the reaction mixture CO + NO + O2 + H2O + SO2. Modification of the Pd-Co3O4/cordierite with cerium oxide considerably increases its sulfur resistance.  相似文献   

16.
Mixed oxides CoxAlyO4 with different Al/Co ratios applied as supports for the catalysts of the Fischer-Tropsch synthesis were prepared using the solid-state chemical reaction. The CoxAlyO4 supports were prepared by modifying gibbsite with various cobalt salts (acetate, nitrate, and basic carbonate). The use of basic cobalt carbonate gives the Co(20%)/CoxAlyO4 catalyst, which provides an increased yield of hydrocarbons C5+ and a decreased methane content compared to the impregnation catalyst Co(30%)/Al2O3. The introduction of small amounts of rhenium additives makes it possible to enhance the yield of hydrocarbons C5+ (179 g m−3) and also to increase the selectivity with respect to the C5–C18 fraction. The introduction of basic cobalt carbonate into the support, most likely, creates favorable conditions for the epitaxial growth of the precursor of the active phase. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1856–1860, September, 2007.  相似文献   

17.
A simple, rapid, and economical spectrophotometric method is developed for the determination of sulfur dioxide in sugar and air samples. The developed method is based on a red-brown peroxovanadate complex (λmax = 470 nm) produced in 2 M sulfuric acid when ammonium metavanadate is treated with hydrogen peroxide. Under fixed concentrations of hydrogen peroxide and ammonium metavanadate, when sodium metabisulfite (Na2S2O5 = 2SO2) is added, it preferentially reacts with hydrogen peroxide producing sulfuric acid, and the unreacted hydrogen peroxide then reacts with ammonium metavanadate; therefore, the concentration of sulfur dioxide is directly proportional to a decrease in the concentration of the peroxovanadate complex. The stoichiometric ratio between hydrogen peroxide and ammonium metavanadate as well as the stability constant of the complex are determined by the modified Job’s method and the respective values are found to be 1: 1 and 2.5 × 104 mol−1 L, respectively. The system obeys Lambert-Beer’s law in the concentration range 3.57–64.26 ppm of sulfur dioxide. The molar absorptivity, correlation coefficient, and Sandell’s sensitivity values are found to be 0.649 × 103 L mol−1 cm−1, 0.9908, and 0.1972 μg cm−2, respectively. The method is applied to the determination of sulfur dioxide present in commercial sugars and air samples. The results obtained are reproducible with a standard deviation of 0.02–0.05. For method validation, sulfur dioxide is also determined separately following the AOAC method for an air sample and the ICUMSA method for commercial sugars. The results obtained by the developed and official methods are in good agreement. The text was submitted by the authors in English.  相似文献   

18.
The activity of samples containing indium in the selective catalytic reduction (SCR) of NO with C1-C4 hydrocarbons depends on nature of the carrier, Al2O3, ZrO2, the quantity of indium oxide, and the method of its introduction. The most active catalysts (2.5–5.0% In2O3/Al2O3) are stable to water and are characterized by a large overall concentration of oxide centers. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 107–111, March–April, 2007.  相似文献   

19.
R. Snel 《Chromatographia》1986,21(5):265-268
Summary A simple gas chromatographic system has been developed for the rapid on-line analysis of light Fischer-Tropsch products. This involves a single chromatography fitted with two columns, a porous-layer open-tubular column coated with KCl deactivated alumina and a packed Porapak-Q column. The capillary column separates the 16 most common C1−C4 hydrocarbons and permits a reasonable analysis of the hydrocarbons in the C5−C7 range. The packed column is used for the separation of methane, carbon monoxide, carbon dioxide, water and methanol. Retention characteristics for the analysis on the capillary column are presented. The total analysis cycle is 30 minutes.  相似文献   

20.
This paper presents a study for the preparation of CoxFe3−xO4 (x = 0.02, 0.2, 0.5, 0.8, 1.0, 1.1, 1.5) nanoparticles, starting from metal nitrates: Co(NO3)2·6H2O, Fe(NO3)3·9H2O and ethylene glycol (C2H6O2). By heating the solutions metal nitrates-ethylene glycol, the redox reaction took place between the anion NO3 and OH–(CH2)2–OH with formation of carboxylate anions. The resulted carboxylate anions reacted with Co(II) and Fe(III) cations to form coordinative compounds which are precursors for cobalt ferrite. XRD and magnetic measurements have evidenced the formation of cobalt ferrite for all studied molar ratios. The average diameter of the cobalt ferrite crystallites was estimated from XRD data and showed values in the range 10–20 nm. The crystallites size depends on the annealing temperature. The magnetization of the synthesized samples depends on the molar ratio Co/Fe and on the annealing temperature.  相似文献   

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