SO2存在条件下M/REY催化剂NH3选择性还原NO性能研究

采用浸渍法制备了以REY为载体负载金属氧化物催化剂。采用XRD、NH₃-TPD、NO-TPD、H₂-TPR和XPS对催化剂进行表征,并在固定床微型反应器上评价SO₂存在条件下催化剂在NH₃选择还原NO反应中的活性。实验结果表明,活性组分种类及负载量均影响催化剂性能,Cu(3)/REY催化剂在NH₃选择还原NO反应中表现出较好的低温活性,在SO₂存在条件下,254~390℃时NO的转化率大于95%。催化剂表征结果显示,Cu(3)/REY催化剂的催化活性与其良好的氧化还原性和对NO的吸脱附性能相关。     

SO2对NO催化氧化过程的影响V.NiO/γ-Al2O3上SO2的作用机理

采用程序升温脱附(TPD)及漫反射原位红外光谱(DRIFT)技术分析比较了SO2存 在前后，NO—02反应气体在NiO／γ—Al2O3催化剂上所形成吸附物种的变化情况， 发现SO2能促使硝酸盐物种在低温分解并释放出NO2，而且耐热稳定的硝酸盐物种也 比单纯NO-02吸附时多．室温时催化剂表面上的SO2以弱吸附物种为主，特征红外吸 收峰位于1324cm^-1附近，温度升高后表面硫酸盐物种数量增多．关联SO2气氛中 NO2的生成规律后得出，类似于铅室反应中间体的多分子吸附物种[NO2(SO3)x]是产 生N02的活性物种，由SO2在载体或催化剂表面弱碱位吸附后吸引气相NO所产生，解 离O^-起到稳定活性物种和补充弱碱位的作用．同时该物种也是毒性物质SO4^2-的 前驱体，当KO氧化反应发生后催化剂的失活也开始了．     

Propane dehydrogenation by SO2 in the presence of carbon

The oxidative condensation products of the title reaction are catalytically active, presumably because sulfur enters into their composition.

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The mechanism of SO2 oxidation by CH3O2 radicals. Rate coefficients for the reactions of CH3O2 with SO2 and NO

The reactions of CH₃O₂ with SO₂ and NO have been studied by steady state photolysis of azomethane in the presence of O₂SO₂→NO mixtures at 296 K and 1 atm total pressure. The quantum yield of NO oxidation by CH₃O₂ radicals is increased substantially when SO₂ is added to the system indicating an SO₂ induced chain oxidation of NO. The rate law gives k₁/k₂ = (2.5 ± 0.5) × 10^?3 for CH₃O₂ + SO₂ → CH₃O₂SO₂ (1), CH₃O₂ + NO → CH₃O + NO₂ (2). Combining this ratio with the absolute value of k₁ = 8.2 × 10^?15 cm³ s^?1 gives k₂ = 10^{?11.5 ± 02} cm³ s^?1.     

Kinetic investigation of CO oxidation in the presence of SO2

The kinetics of CO oxidation on a mixed, Pd-containing catalyst have been studied by the gradientless method. The reaction rates were measured as a function of the temperature and the CO and SO₂ concentrations. A break has been found on the kinetic curves, showing the influence of CO concentration on the reaction rate.

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CO . — , CO .

     

CO oxidation over CuCr/Al2O3 catalysts in presence of SO2

Poisoning of variously prepared CuCr/Al₂O₃ catalysts having different compositions by sulfur dioxide has been studied. Comparative values for a decrease in the catalyst activities have been obtained.

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CO .

     

Bond function parameter transferability in SO2, SF2 and SO2F2

Ab initio MO studies of the use of gaussian bond functions in the molecules SO₂,SF₂ are presented. It is shown that optimization of bond function exponent and position parameters in the small molecules is a good approximation to the optimum parameter set for SO₂F₂,     

Fast chemisorption of NO and SO2 on FeOOH crystals

The electrical conductivity changes of α-, β- and γ-FeOOH by adsorption of NO and SO₂ during 1 ms-1 min were determined. The conductivity change consists of fast and slow processes which are presumably caused by fast chemisorption on the oxygen vacancies and by slow one on the surface anions. The rate constants of fast and slow chemisorption were determined from the conductivity changes. The correlations of the rate constants with the compression pressure of specimen, adsorption temperature and original electrical conductivity are given. The order of magnitude of the fast chemisorption rate constants of the three polymorphs is related to the difference in the surface structure.     

A shock tube study of vibrational relaxation in SO2, SO2Ar and SO2He

Vibrational relaxation times in SO₂, SO₃Ar (11%, 20% and 54% SO₂) and SO₂He (9.5% SO₂) were measured behind incident shock waves using the laser schlieren technique in the temperature ranges 550–1200 K, 700–2100 K and 700–1600 K respectively for the three systems. An analysis of the density gradient signals revealed a double exponential behaviour consistent with earlier studies. The fast relaxation rates were not quantitatively studied and the slow relaxation rates were found to fit the following equations:

where Pτ is the relaxation time in atm μs and T is in °K. The collision numbers corresponding to the slower rates were found to agree well with a recent theoretical calculation using SSH-Tanczos theory.     

Calculation of the rate of SO2 oxidation to SO3

Approximate equation to calculate the effectiveness factor of catalyst for SO₂ oxidation to SO₃ has been derived. Calculated data agree well with those predicted by a quasi-homogeneous model.

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CoOx-CeOx/ZrO2催化氧化NO性能及抗SO2毒化研究

采用浸渍法制备了一系列CoO_x-CeO_x/ZrO₂催化剂,探讨了催化剂载体、Co含量、Co/Ce配比等对Co基催化剂催化氧化NO活性的影响及其机理。ZrO₂负载的Co氧化物具有优良的低温NO催化氧化活性,铈的添加进一步提高了催化剂的低温活性。其促进机制主要是提高了催化剂吸附氧的能力及改善了Co在催化剂表面的分散。同时,掺杂铈使得催化剂抗SO₂能力有一定增强,呈现出选择性毒化机制。     

Investigation of phase equilibria in the systems K2SO4Sc2(SO4)3, Rb2SO4Sc2(SO4)3 and Cs2SO4Sc2(SO4)3

Phase diagrams of the systems K₂SO₄Sc₂(SO₄)₃, Rb₂SO ₄Sc₂(SO₄)₃ and Cs₂SO₄ Sc₂(SO₄)₃ have been investigated by X-ray diffraction phase analysis and differential thermal analysis techniques. A salient feature of all the systems is the formation of M₃Sc(SO₄)₃, which melt incongruently, and MSc(SO₄)₂, which on heating decompose in the solid state.     

High-temperature reduction of SO2 by methane at various CH4/SO2 ratios

The character of the effect of initial reaction mixture and temperature on the selectivity of catalytic reduction of sulfur dioxide by methane in the presence of oxygen has been studied.

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Mass-spectrometric analysis of SO3 in SO2 oxidation over vanadium catalysts

The detailed composition of the reaction mixture and, in particular, SO₃ concentration, in SO₂ oxidation over vanadium catalysts, have been determined experimentally. Both oxidized and reduced catalysts were shown to absorb a considerable amount of SO₃, the desorption rate of SO₃ being lower than that of its adsorption.

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, , . , , SO₃, .

     

Simultaneous determination of NH3, SO2, NO and NO2 by direct UV-absorption in ambient air

Summary Direct spectroscopic methods are not hampered by wall losses, are highly specific, have a potential for real time detection and offer the possibility to measure several species simultaneously in one experiment. This is demonstrated for the determination of NH₃, NO and SO₂ in ambient air by a differential optical a2bs orption spectroscopy (DOAS) technique in the spectral region 207–221 nm. Detection limits were 1 ng/g or better.     

Electron beam process for SO2 removal from flue gases with high SO2 content

Flue gases with high SO₂ concentration are emitted from different industrial processes, e.g. combustion of coal with high sulfur content, copper smelting and sintering plant. The application of the electron beam process for SO₂ removal from such flue gases was investigated. A parametric study was carried out to determine the removal efficiency as a function of temperature and humidity of irradiated gases, dose and ammonia stoichiometry. At the dose 11.5 kGy 95% SO₂ removal efficiency was obtained when the temperature and humidity of irradiated flue gases and ammonia stoichiometry were properly adjusted. The synergistic effect of high SO₂ concentration on NO_x removal was observed. The collected by-product was the mixture of (NH₄)₂ SO₄ and NH₄NO₃. The content of heavy metals in the by-product was many times lower than the values acceptable for commercial fertilizer.     

Vibrational relaxation in SO2

SSH—Tanczos calculations are carried out to estimate the energy transfer probabilities and the slow vibrational relaxation time in SO₂ in the temperature range 300–2000 K. The theoretical results suggest a series process below 1000 K, and a complex series/parallel process above that temperature for the vibrational relaxation in SO₂. The theoretical results are compared with the known experimental data.     

Zur Bestimmung von SO2 und SO3, in ihren Gemischen

Ohne Zusammenfassung     

The phase diagram of the system La2(SO4)3Ag2SO4

The phase diagram of the system La₂(SO₄)₃Ag₂SO₄ was studied by DTA, XRD, SEM, and optical methods. One double salt is formed at 67 mole% La₂(SO₄)₃ and this melts incongruently at 876±6°C. A eutectic is formed at 8 mole% La₂(SO₄)₃ and at a temperature of 618±3°C. Suppression of decomposition was effected by the sealed tube method, but some reference is made to experiments conducted with a flowing atmosphere of SO₃, SO₂ and O₂.     

Theoretical investigations on the SO2 + HO2 reaction and the SO2–HO2 radical complex

The mechanism of the SO₂ + HO₂ reaction was studied theoretically for the first time. Three product channels were revealed, namely, O₂ + HOSO, O₂ + HSO₂, and OH + SO₃. The O₂ + HOSO channel dominates the reaction under combustion conditions. A five-member-ring complex [SO₂–HO₂] exists at the entrance of the reaction. The structure and binding energy (D_e and D₀) of the SO₂–HO₂ complex have been calculated. In view of D₀ = 21.2 ± 2.0 kJ mol⁻¹, the SO₂–HO₂ complex should be stable at low temperature. The infrared spectra and frequency shifts were calculated for both SO₂–HO₂ and SO₂–DO₂, and compared with the available experimental data.