Generation of chemical reaction mechanism. CO hydrogenation catalyzed by meaal atoms in the gas phase

An approach to determine the catalytic properties of metal atoms for the hydrogenation of CO in the gas phase is suggested. This approach has been developed using an algorithm based on a mathematical model for structural chemistry. Structural and energetic characteristics for intermediates and possible products of the catalytic hydrogenation of CO to C₁ and C₂ organic compounds and metals established as catalysts for the formation of various products are presented.

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. C₁ C₂- . , .

     

Generation of mechanisms of chemical reactions. Gas phase CO+H2 reaction in the absence of catalysts

An algorithm for the generation of chemical reaction mechanisms in the absence of catalysts tested for the reaction of CO hydrogenation is suggested.

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State of components in contact solutions based on Pd(II) salts and Fe(NO3)3 for ethylene oxidation to EGMA

Physico-chemical studies of contact solutions based on Pd(II) salts and Fe(NO₃)₃ for ethylene oxidation to EGMA have been carried out.

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- (II) .

     

Membrane separation of ions for the preparation of pure solutions of heteropolycompounds

Reverse osmosis was used for the separation of various types of heteropolyanions (HPA): [PW₁₁O₃₉M(H₂O)] ^k– (M = Co^II, Fe^III, Cr^III), [(PW₁₁O₃₉Fe)₂O]^10– , and [PW₁₁O₃₉ · Fe _n O _x H _y ] ^p– from contaminant ions NO₃ ^– and Na⁺ that are usually introduced into the solution in the synthesis of HPA.Translated fromIzvestiya Akodemii Nauk. Seriya Khimicheskaya, No. 4, pp. 1009–1011, April, 1996.     

Synthesis and spectral properties of titanium(iv) polynuclear hydroxo complexes stabilized in solution by the [PW11O39]7− heteropolyanion

Unsaturated heteropolyanions (HPA) [PW₁₁O₃₉]⁷⁻ stabilize Ti^IV hydroxo complexes in aqueous solutions (Ti: PW₁₁ [PW₁₁O₃₉]⁷⁻⪯12, pH 1–3). Spectral studies (optical,¹⁷O and³¹P NMR, and IR spectra) and studies by the differential dissolution method demonstrated that Ti^IV hydroxo complexes are stabilized through interactions of polynuclear Ti^IV hydroxo cations with heteropolyanions [PW₁₁TiO₄₀ ⁵⁻ formed. Depending on the reaction conditions, hydroxo cations Ti _n−1O _x H _y ^m+ either add to oxygen atoms of the W−O−Ti bridges of the heteropolyanions to form the complex [PW₁₁TiO₄₀·Ti _n−1O _x H _y ] ^k− (at [HPA]=0.01 mol L⁻¹) or interact with Ti^IV of the heteropolyanions through the terminal o atom to give the polynuclear complexes [PW₁₁O₃₉Ti−O−Ti _n−1O _x H _y ]^q− (at [HPA]=0.2 mol L⁻¹). When the complexes of the first type were treated with H₂O₂, Ti^IV ions added peroxo groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–920, May, 1997.     

Study of the equilibrium of formation of arsenic(iii) lacunar heteropolytungstates by Raman spectroscopy

The formation of lacunar heteropolyanions (HPA): [AsW₉O₃₃]^9–, [As₂W₁₉O₆₇(H₂O)]^14–, and [As₂W₂₀O₆₈(H₂O)]^10– in aqueous solutions was investigated by Raman spectroscopy at [Na₂HAsO₃]₀ = 0.1, [Na₂WO₄]₀ = 0.9 mol L^–1 and pH 9.4–1.6. The [AsW₉O₃₃]^9– HPA is characterized by the most intense band ns (W=O) at 948 cm^–1 retaining its position in the pH range from 8.9 to 7.5. Under these conditions, the equilibrium constant of [AsW₉O₃₃]^9– formation from H₂AsO₃ ^– and WO₄ ^2– ions was estimated (logK = 87.0±1.0). The asymmetrical band at 952 cm^–1 corresponding to H_x[As₂W₁₉O₆₇(H₂O)]^(14–x)– shifts to 960 cm^–1 as the pH decreases from 6.5 to 5.5, which is due to the change in HPA protonation. The [As₂W₂₀O₆₈(H₂O)]^10– HPA is formed at pH 3.1—1.6; it is characterized by a band at 972 cm^–1.     

Acidity of Solutions of Heteropoly Acids with Various Structures and Compositions

Hammett acidity functions H ₀ of solutions of heteropoly acids H₅PW₁₁XO₄₀ (X(IV) = Ti, Zr), H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₆P₂W₂₁O₇₁, and H₂₁B₃W₃₉O₁₃₂, as well as HClO₄ and CF₃SO₃H, in water and 90% aqueous acetone and acetonitrile, are measured at 20°C by the indicator method. In aqueous solutions all acids under study have the same strength, and in organic solvents their acidities differ. A correlation between the catalytic activity and acidity of the solution is found for the condensation of acetone to mesityl oxide.     

Solvent effect on the rate and direction of furfural transformations during hydrogenation over the Pd/C catalyst

Russian Chemical Bulletin - The rate and directions of transformations during the liquid-phase hydrogenation of furfural with molecular hydrogen in the presence of the 5%Pd/C catalyst (at 423 K, 3...     

Effect of High-Temperature Gas-Chemical Modification on the Structural and Functional Properties of Carbon Black Particles

The structure and electrochemical properties (specific capacitance and electrical resistance) of various grades of carbon black before and after high-temperature gas-chemical treatment were studied. The textural and structural parameters were determined by the methods of low-temperature nitrogen adsorption, dibutyl phthalate absorption, X-ray diffraction analysis, and Raman spectroscopy. The results are compared to the characteristics of Printex XE2-B extra-conductive carbon black.     

Catalytic properties of platinum-promoted acid cesium salts of molybdophosphoric and molybdovanadophosphoric heteropoly acids in the gas-phase oxidation of benzene to phenol with an O<Subscript>2</Subscript> + H<Subscript>2</Subscript> mixture

Acid salts Cs _x H_{3 + n ? x} PMo_{12 ? n} V _n O₄₀ (n = 0, 1, 2, or 3; x = 2.5 or 3.5) with coprecipitated or supported platinum were studied using thermogravimetry, IR spectroscopy, and temperature-programmed reduction. The thermal region of the full stability of these salts is limited by the decomposition temperature of the corresponding acid H₃PMo₁₂O₄₀ (～400°C) or H_{3 + n} PMo_{12 ? n} V _n O₄₀ (～300–350°C). The degree of reduction of heteropoly anions with hydrogen is regulated by temperature. Deeply reduced heteropoly anions (at 300°C) are slowly oxidized with oxygen with structure and composition regeneration. The states of molybdenum and vanadium on the surface of samples with coprecipitated platinum Pt_0.1-Cs_2.5H_0.5PMo₁₂O₄₀ (1) and Pt_0.1-Cs_2.5H_2.5PMo₁₀V₂O₄₀ (2), which were studied using XPS, correspond to reduced or reoxidized heteropoly anions in the bulk. Platinum metal particles of ～5 nm in size were observed in high-resolution TEM images obtained after the reduction and storage of sample 1 in air. A heteropoly compound forms two texture levels: spherical nanoparticles of 10–20 nm in size are collected in closely packed globules of 100–300 nm in size. Detailed texture studies, which were performed using nitrogen adsorption isotherms, demonstrated texture mobility under the ambient conditions. The cesium salts of the heteropoly acids were tested in the gas-phase oxidation of benzene to phenol with an O₂ + H₂ mixture at 180°. The effect of platinum concentration on the specific catalytic activity in the presence of deeply reduced heteropoly anions was monitored. The samples containing the salt Cs_2.5H_0.5PMo₁₂O₄₀ exhibited the highest activity in the formation of phenol. The introduction of vanadium into the heteropoly anion impaired the catalytic performance of both deeply and slightly reduced samples.