Investigation of ethylene interaction with some oxidants in the presence of Pd2+ in acetic acid

The composition of products from the interaction of ethylene with some o oxidants, catalyzed by palladium acetate in acetic acid has been studied, An assumption is made on the possible reason for the influence of such oxidants on the selectivity of formation of ethylene glycol ethers.

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A Study of the Acid Properties of Structurally and Compositionally Different Heteropoly Acids in Acetic Acid

The acid properties of heteropoly acids of the following three structure types were studied by conductometry in acetic acid: Keggin (H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₁ThO₃₉; and H₅PW₁₁XO₄₀, where X(IV) = Ti or Zr), Dawson (-H₆P₂W₁₈O₆₂and -H₆P₂Mo₁₈O₆₂), and H₆P₂W₂₁O₇₁(H₂O)₃. These compounds are electrolytes that dissociate in only the first step of this solvent. The thermodynamic dissociation constants of the heteropoly acids were calculated by the Fuoss–Kraus method. The Hammett acidity functions H ₀of the solutions of H₅PW₁₁XO₄₀, H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, and H₆P₂W₂₁O₇₁(H₂O)₃in 85% acetic acid at 25°C were determined by the indicator method. All of the test heteropoly acids were found to be strong acids.     

Esterification of n-Butanol with Acetic Acid in the Presence of Heteropoly Acids with Different Structures and Compositions

The esterification reaction of n-butanol with acetic acid ([BuOH] : [HOAc] = 1 : 15 mol/mol; 55°C, 5% H₂O) was studied in the presence of tungsten heteropoly acids of the Keggin (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₅PW₁₁TiO₄₀, H₅PW₁₁ZrO₄₀, and H₃PW₁₁ThO₃₉) and Dawson structure (-H₆P₂W₁₈O₆₂, H₆P₂W₂₁O₇₁(H₂O)₃, H₆As₂W₂₁O₆₉(H₂O), and H₂₁B₃W₃₉O₁₃₂). The reaction orders with respect to H₆P₂W₂₁O₇₁(H₂O)₃, H₃PW₁₂O₄₀, and H₆P₂W₁₈O₆₉are equal to 0.78, 1.00, and 0.97, respectively. It was found that the reaction rate depends on the acidity, as well as on the structure and composition of heteropoly acids. The H₂₁B₃W₃₉O₁₃₂heteropoly acid is most active, whereas the Keggin-structure heteropoly acids exhibit the lowest activities. Of the Keggin structure heteropoly acids, H₅PW₁₁ZrO₄₀exhibits the highest activity because of the presence of a Lewis acid site in its structure.     

The use of temperature to simplify formose sugar composition

Form ose reaction, the Ca(OH)₂ catalyzed condensation of HCHO to a complex mixture of sugars, does not lose its autocatalytic nature at 98°C. The induction period is 15 sec, and then, at 18% total HCHO conversion, there was a period of approximately 3 sec duration in which the reaction had produced C₆ sugars at 84.3 wt.% selectivity. Glucose amounted to 90% of those sugars, and no branched sugars were detected. Conversion was complete within 3 min. The simple nature of the product was lost at lower temperatures or higher conversions.

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— HCHO, Ca(OH)₂, 98°C. 15 , 38%- HCHO 3 , C₆ 84,3 . %. 90%, . 3- . .

     

Liquid-phase oxidation of propylene to propylene glycol acetates over Pd/C and Pt?Pd/C: Effect of platinum on catalyst activity and metal dispersity

Kinetics of oxidation of propylene to propylene glycol and its acetates in acetic acid solutions of lithium nitrate over Pd/C and Pd–Pt/C catalysts has been studied. Catalysts were investigated using X-ray phase analysis and electron microscopy. Platinum introduction into catalyst increases the metal dispersity and the catalyst stability but produces no effect on the nature of surface sites active in propylene oxidation.

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Pd/C Pd–Pt/C. . , , , .

     

Ruthenium complexes with heteropoly anion PW11O39 7− and their redox properties

A new heteropoly complex PW₁₁Ru^IV and complexes of Ru^II, Ru^III and Ru^V based thereon have been obtained. Using specrophotometry the states of Ru^III and Ru^IV complexes in solution, the pH range of their stability, and the interaction of PW₁₁Ru^IV with ClO₄ ^–,SO₄ ^2–, Cl^– ions have been studied. A conclusion has been thus made that the ruthenium ion in such a complex is not incorporated in the heteropolyanion lattice, but is attached only to its external oxygen atoms. Kinetics of oxidation of PW₁₁Ru^IV and PW₁₁Ru^III with potassium chlorate have been studied. The activation energy and pre-exponential factor have been found for the reaction. The possibility that ClO₄ ^– and ClO₃ ^– in aqueous solutions can be activated by PW₁₁Ru^II with the former and by PW₁₁Ru^III and PW₁₁Ru^IV with the latter has been demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1363–1369, August, 1993.The authors wish to thank I. L. Krayevskaya and V. M. Novopashina for X-ray fluorescence and ionic chromatographic analyses, respectively.     

Effect of dentate number of anchored phosphine ligands on the composition and catalytic properties of their palladium complexes

Mono-, di- and triphosphine ligands anchored by a Si–C bond to the surface of silica have been synthesized. Complexes of Pd(II) and Pd(O) with these ligands have been obtained. On the basis of elemental analysis and UV spectroscopy, structures of the complexes formed are suggested. The catalytic properties of the above complexes in the selective hydrogenation of cyclopentadiene are compared.

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-, - , Si–C . Pd(II) Pd(O) . - . .

     

New Y(La)-M-O Binary Systems (M = Ca,Sr, or Ba): Synthesis,Physicochemical Characterization,and Application As the Supports of Ruthenium Catalysts for Ammonia Synthesis

The effect of the nature of the alkaline-earth metal on the phase composition and specific surface area of new Y(La)-M-O binary oxide compositions (M = Ca, Sr, or Ba) prepared by coprecipitation was studied. These systems were found to contain mixed compounds (M₂Y₂O₅, MY₂O₄, and MLa₂O₄), which are different in thermal stability, in addition to individual La₂O₃ or Y₂O₃ phases. The Y(La)-M-O compositions calcined at 450°C were characterized by a more developed specific surface area, as compared with that of individual La₂O₃ or Y₂O₃. An increase in the calcination temperature to 650°C was accompanied by a decrease in the specific surface area of binary compositions. Catalysts prepared by supporting K₂[Ru₄(CO)₁₃] onto the Y(La)-M-O systems were active in ammonia synthesis at 250-400°C and atmospheric pressure. The most active of these catalysts, K₂[Ru₄(CO)₁₃]/Y-Ba-O, provided a higher yield of NH₃ at 250-300°C than analogous catalysts prepared with the use of well-known supports (Sibunit, CFC-1, and C/MgO).     

Acidity of heteropoly acids with various structures and compositions studied by IR spectroscopy of the pyridinium salts

The acidity on the proton affinity scale was determined by IR spectroscopy of the pyridinium salts for nineteen heteropoly acids of nine structural types (including two with the previously unknown structure) and one isopoly acid. All heteropoly acids exhibited a high acidity at the level of CF₃SO₃H and HClO₄. H₃PW₁₂O₄₀ was the strongest acid.     

Structure sensitivity of Fe(II) oxidation on palladium and platinum catalysts

The oxidation of ferrous sulfate with dioxygen, an example of an inorganic redox process in aqueous phase, has been studied on a number of carbon-supported Pd and Pt catalysts, both freshly reduced and kept for a long time after contacting with air. In the whole range of metal dispersities studied (0.10–0.75, as determined by CO chemisorption) a several-fold gradual loss of intrinsic activity has been found when increasing the dispersity. Such a decrease appeared sufficient to present volcanotype plots for the corresponding activities on a per-gram basis. It has been concluded that the metal particle size and oxidation state of the metallic surface are two independently acting factors which affect the intrinsic rate.