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 oxidation of CH4 and SO2 over vanadium and palladium containing catalysts

The kinetics of deep oxidation of CH₄ and SO₂ over complex vanadium catalysts with and without palladium additives and over silica-supported palladium has been studied. Sulfur dioxide increases the rate of CH₄ oxidation, not affecting the reaction mechanism, whereas CH₄ does not effect SO₂ oxidation on the catalysts studied.

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, , . , , .

     

Kinetics of dissolution of inactive crystalline phase in vanadium catalysts for SO2 oxidation

Kinetics of inactive crystalline phase dissolution of V(IV) compounds formed under SO₂ oxidation in the region of low temperatures and conversions has been studied. Dissolution rate is shown to increase with increasing temperature and pressure of SO₃.

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V(IV), . , .

     

Studies of fast relaxations in SO2 oxidation on active components of vanadium catalysts

Studies of the fast relaxations of the reaction mixture composition in the SO₂ oxidation on V₂O₅–K₂S₂C₇ have revealed O₂ and SO₂ evolution from the catalyst during the initial period of the reaction. An associative mechanism for the interaction of molecular oxygen with the molten active vanadium complex is suggested.

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є SO₂. . .

     

Studies of adsorption-desorption processes in SO2 oxidation on the active component of vanadium catalysts

Diffusion and solubility coefficients of O₂, SO₂ and SO₃ in the active component of vanadium catalysts have been determined by a high-speed relaxation method. Processes of their dissolution are shown to be quasi-equilibrium with respect to catalytic reactions.

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O₂, SO₂ SO₃ ,

     

Analysis of a nonsteady-state kinetic model for SO2 oxidation

The dynamics of the steps of catalytic SO₂ oxidation affect the reaction rates in periodic operation.

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.

     

Active component of vanadium catalysts in oxidation of gases with low concentrations of SO2

EPR and NMR studies show that in oxidation of gases with low concentrations of SO₂ the molten active component of K/V and Cs/V catalysts becomes inhomogeneous and contains V⁵⁺ compounds having different activities.

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, SO₂ K/V Cs/V , V⁵⁺.

     

Individual and combined oxidation of CO and SO2 on vanadium catalysts with and without Pd additives

The function of SO₂ in CO oxidation on Pd-V catalysts is to transform a rapid heterogeneous-homogeneous process to a slower heterogeneous one. High concentrations of CO also exert the same effect. In the heterogeneous process an increase in the SO₂ concentration increasing the degree of catalyst reduction with and without Pd additives, promotes CO oxidation.

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CO - SO₂ - . CO. SO₂, , , CO.

     

Influence of porous support structure and active component composition on deactivation of vanadium catalysts in SO2 oxidation

The effect of porous support structure and active component composition of vanadium catalysts on the crystallization character of this component has been studied in SO₂ oxidation at low temperatures and conversion degrees. The tendency to crystallization is shown to drop with decreasing support pore radius and with increasing K/V molar ratio.

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. , K/V.

     

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 .

     

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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. .

     

Effect of NH3 and SO2 on n-butane oxidation

It has been established that NH₃ and SO₂ adsorption on the surface of V–P–O catalysts at reaction temperatures modifies its acid-base properties, which changes its activity and selectivity.

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, NH₃ SO₂ V–P–O -C₄H₁₀, - .

     

CH4 oxidation over palladium and vanadium containing catalysts

The kinetics of total oxidation of CH₄ over a complex vanadium catalyst with and without Pd additives and over silica-supported palladium has been studied. The addition of palladium increases the initial reaction rate but as catalysis progresses, the activity decreases to the level of an unpromoted catalyst. Palladium additives do not affect the mechanism of CH₄ oxidation.

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, , . , . .

     

Kinetic models of CO oxidation on Pd-containing catalysts (with and without SO2)

The effect of reactants and experimental conditions on the Pd/C catalyzed oxidation of DS at 110–150°C and 0.3–1.0 MPa in alkaline aqueous solution is described with emphasis on the maximal reaction rate, yield of DGA and catalyst deactivation. Oxygen causes practically irreversible deactivation of catalyst.

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DS Pd/C 110–150°C 0.3–1.0 . , DGA . .

     

51V-,29Si- and27Al-NMR studies of the interaction of active component of vanadium catalysts for SO2 oxidation with supports

NMR studies have revealed that silicas and aluminosilicates interact with the active components of vanadium catalysts, in the former case merely yielding surface compounds.

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, , .

     

Regioselective bromination of aromatic compounds with Br2/SO2Cl2 over microporous catalysts

A new selective brominating system Br₂/SO₂Cl₂/zeolite, has been discovered. Partially cation-exchanged Ca²⁺-Y zeolite efficiently catalyzes the selective para-bromination of neat chlorobenzene (CB) by Br₂/SO₂Cl₂ affording a CB conversion of ∼89% and a para-selectivity of ∼97%. During the bromination reaction, SO₂Cl₂ oxidizes HBr, prevents its accumulation within the zeolite pores and yields a more active brominating species. The Ca²⁺-Y catalyst was found to be stable under the bromination conditions, and can easily be regenerated by calcination. The Br₂/SO₂Cl₂/Ca²⁺-Y brominating system could be applicable to other activated aromatic compounds such as o-xylene, toluene and fluorobenzene.     

SO_2对Mn-Ce/TiO_2低温SCR催化剂的毒化作用研究

考察了SO_2对Mn-Ce/TiO_2低温脱硝催化剂活性的影响,利用XRD、BET、SEM和XPS对其毒化作用的原因进行分析。结果表明,SO_2对催化剂活性有明显的抑制作用,使NO_x去除率由84%降至42%左右。主要是SO_2的加入造成催化剂比表面积减小,孔径为5-10 nm的孔数量减少,且催化剂晶相由锐钛矿型转化成金红石型结构,活性组分MnO_x发生晶化现象,破坏了Mn-Ti间的强相互作用。催化剂理化性质的变化造成吸附态氧转化为晶格氧的路径受阻、MnO_2含量减少和CeO_x储氧功能减弱,并且产生氧阻效应而使NO吸附和解吸受阻,造成催化剂活性降低。同时生成的硫酸铵盐在催化剂表面沉积,覆盖了催化剂表面的Lewis酸性位,使其对NH_3吸附能力减弱。     

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,