The effect of the nature of a modifying additive (Pt,Zn, Ga) on the activity of oxide and zeolite catalysts in ethane dehydrogenation and aromatization

The catalytic properties of Pt, Zn, and Ga deposited on supports of various natures (Al₂O₃, SiO₂, NaZSM, and HZSM) in the dehydrogenation and aromatization of ethane were investigated. Pt-containing catalysts are the most active in the conversion of ethane: the selectivity with respect to ethylene is 25–87 % depending on the nature of the support. In the presence of Zn- and Ga-containing catalysts the yield of ethylene is 2–3 times lower than with Pt-catalysts. With HZSM modified by Pt, Zn, or Ga aromatic hydrocarbons (ArH) and methane are the main products of ethane transformation. Ga/HZSM is the most efficient catalyst of the aromatization of ethane under the conditions studied (550 °C, 120 h^–1).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 606–609, April, 1994.     

Laser activation of ethylene and formaldehyde quenching

A novel method is described for oxidizing ethylene with molecular oxygen to give formaldehyde under normal conditions in the presence of the beam from a continuous wave low-power CO₂ laser (943 cm^–1), which is in resonance with the ethylene vibrational mode p(CH₂) = 949 cm^–1; the method involves activating the CH₂-CH₂ bonds to failure with the formation of biradicals and then quenching the formaldehyde, which is out of equilibrium as regards temperature.Institute for General and Inorganic Chemistry, Academy of Sciences of The Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Eksperimental'naya Khimiya, No. 2, pp. 220–223, March–April, 1991. Original article submitted April 19, 1990.     

Kinetic peculiarities of the heterogeneous-homogeneous conversion of ethylene to butadiene

The influence of the surface of the quartz packing and degree of crystallinity of aluminosilicate crystals on the total conversion of C₂H₄ and selectivity in the conversion of ethylene to butadiene have been established. It was shown that the data agree with the hypotheses of a heterogeneous-homogeneous mechanism of the process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 1, pp. 44–47, January–February, 1995.     

Preparation of 2-chloroethyl alkyl sulfones by the addition of alkanesulfonyl chlorides to ethylene

Conclusions A study was made of the addition of alkanesulfonyl chlorides to ethylene under pressure in the presence of CuCl₂, Cu₂Cl₂, and their mixtures, and it was shown that here the corresponding 2-chloroethyl alkyl sulfones are formed in 90–95% yield when based on reacted alkane-sulfonyl chloride, with a 35–40% conversion of the latter.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–941, April, 1977.     

Pulse radiolysis studies on [Fe(CN)6]4−−BrO 3 − −CN− system in ethylene glycol — Water solutions

Formation of oxidizing and reducing radicals has been studied by pulse radiolysis of [Fe(CN)₆]^4––BrO ₃ ^– –CN^– system in ethylene glycol — water solvent mixture. Oxidizing ·BrO₂ and BrO radicals formed by electron scavenging with ·BrO ₃ ^– were identified and their reactions were investigated. The reaction of hydroxyl radicals with ethylene glycol leads to formation of reactive radicals with reducing properties and of compounds which reduce slowly in dark the ferricyanide formed in the reaction of ·BrO₂ radical with ferrocyanide.     

Single-stage catalytic conversion of ethylene to butadiene

It has been found that butadiene is formed in the process of ethylene conversion over an aluminosilicate catalyst. Data have been obtained on the total conversion of C₂H₄ and product selectivities in the temperature interval from 873 to 973 K. Probable chemical reactions are suggested for this process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 4, pp. 369–371, July–August, 1993.     

(π-Cyclopentenyl)(π-cyclopentadienyl)nickel: A novel catalyst for the conversion of ethylene to 1-butene and n-hexenes

(π-Cyclopentenyl)(π-cyclopentadienyl)nickel, (h⁵-C₅H₅)Ni(h³-C₅H₇), is a novel, highly active, unicomponent catalyst for the conversion of ethylene to n-butenes and n-hexenes at 145–150° C. At high conversions of ethylene (70–90%), the dimeric product (80–86% yield) contains a high percentage (90–82%) of 1-butene. Experimental evidence is presented which strongly indicates that the cyclopentadienyl group remains bonded to the nickel during catalysis while the cyclopentenyl group is labile. A possible mode of activation is the reversible elimination of cyclopentadiene from (h⁵-C₅H₅)N₁(h³-C₅H₇) to generate π-cyclo pentadienylnickel hydride as a catalytically active intermediate. An improved synthesis of the title compound (70% yield) by direct hydrogenation of nickelocene is also reported.     

Migration of Ethylene Terephthalate Oligomers from Roasting Bags into Olive Oil

Summary A high-performance liquid-chromatographic method with UV detection (HPLC–UV) has been developed for quantification of ethylene terephthalate oligomers in olive oil, from which they were extracted with acetonitrile. Oligomers, from monomers (M₁) to pentamers (M₅), were jointly and/or individually identified by liquid chromatography with mass spectrometry (electron-impact mass spectrometry (EIMS) low- and high-resolution) and were quantified by HPLC–UV using an acetonitrile solution of the major oligomer (the trimer M₃) as standard. For M₃ recovery was 98.9%, the detection limit was 60 g L^–2, and method precision was 2.03% (RSD). Migration of oligomers M₁–M₅ into 50 mL olive oil sealed in each of two brands of 10 cm × 10 cm poly(ethylene terephthalate) roasting bag was evaluated under two sets of conditions that approached but remained below the limit at which the bag material became physically deformed – heating for 7 min at 850 W in a microwave oven, or for 60 min at 200 °C in a conventional oven. Total migration was approximately 2.7 mg dm^–2 under the former conditions and 3.5–4.1 mg dm^–2 under the latter.Presented at the International Symposium on Separation and Characteristics of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003     

Electrokinetic control of fluid in plastified laser-printed poly(ethylene terephthalate)-toner microchips

The application of plastified laser-printed poly(ethylene terephthalate)(PET)-toner microchips to capillary electrophoresis was investigated. Electroosmotic flow was observed in the direction of the cathode for the buffer system studied (phosphate, pH 3–10). Average electroosmotic mobilities of 1.71×10^–4 to 4.35×10^–4 cm² V^–1 s^–1 were observed from pH 3 to 10. This variation suggests that silica fillers in the toner and on the surface of the polymer dominate the zeta potential of the material, which is also confirmed by XPS measurements. Dopamine and catechol were used as model analytes for microchip electrophoresis in combination with electrochemical detection. Results show that these two analytes can be efficiently separated and detected electrochemically with the plastified laser-printed PET-toner microchips.     

Determination of copper(I)-ethylene complexes, [Cu(C2H4)]+ and [Cu(C2H4)2]+, with aid of EDTA titration of copper(I) and copper(II) ions

Summary Volumetric measurements of ethylene and simple EDTA titration of copper(I) and copper(II) ions confirm that [CuL]⁺ and [CuL₂]⁺ are formed when an aqueous solution of copper(II) is reduced by copper metal in the presence of ethylene, (L). The formation constants,K ₁=[CuL⁺]²[Cu²⁺]^–1[L]^–2 andK ₂=[CuL ₂ ⁺ ]^–1[L]^–1, have been estimated. The formation of [CuL]⁺ is accompanied by an enthalpy change, H, of –25 kJ mol^–1, and a positive entropy change, S, of 13 J mol^–1 K^–1.     

Determination of inorganic sulphur in aqueous solutions. An application for cyanide extracts of gold ore and plating solutions

Summary The method described for the determination of total sulphur in aqueous solutions known to contain no organic sulphur is based on quantitative conversion of sulphur species to sulphate by hydrogen peroxide at room temperature. The oxidation is first carried out under basic conditions for 1 h and then under acidic conditions for a further hour. The conversion of S^2–, S₂O ₅ ^2– , S²O ₃ ^2– , S₂O ₈ ^2– , SCN^– and SO ₃ ^2– to sulphate is quantitative. The sulphate is then determined turbidimetrically. The method is suitable for a wide range of inorganic solutions containing greater than 2 ppm sulphur. It was applied to determine the total sulphur content in several cyanide extracts of gold ore and plating solutions of zinc and nickel.

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Bestimmung von anorganischem Schwefel in wäßrigen Lösungen. Anwendung auf Cyanideextrakte von Golderzen und galvanische Bäder

     

Effect of Sodium Hydroarsenate on the Kinetics of Reduction of Hydrogen Ions at Iron and on the Hydrogen Diffusion through a Steel Membrane from Aqueous and Ethylene Glycol Solutions of Hydrochloric Acid

Effect of arsenic compounds H₃AsO₄, H₂AsO₄ ^–, and HAsO₄ ^2– on the hydrogen overvoltage, the slow stage of discharge of hydronium ions on the Armco iron, and the hydrogen diffusion through a steel membrane from aqueous and ethylene glycol solutions of hydrochloric acid with a constant ionic strength of unity is considered.     

Metallocomplex catalyst of the addition reaction of CCl4 to ethylene

The catalyst Fe^IIFe₂ ^IIICl₈ (DMA)₆-iron(2+)diiron(3+)octachlorohexakis(dimethylacetamide), was isolated from the media of the catalytic synthesis of 1,1,1,3-tetrachloropropane (C₃), and characterized by physicochemical methods. A counter synthesis of the catalyst was carried out. The telomerization of ethylene with CCl₄ proceeds with a 98% selectivity with respect to C₃ in its presence, while the conversion of CCl₄, reaches 55–60% after 4 h. A coordination-ionic mechanism of the reaction of CCl₄ with C₂H₄ was proposed, which followed the concept of the donor-accpetor electron-transporting systems (the DAET systems), thus accounting for its high selectivity.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2794–2798. December, 1990.     

Mathematical Modeling of Kinetics of Adenosine 5"-Triphosphate Hydrolysis Catalyzed by the Zn2+ Ion in the pH Range 7.4–8.3

Kinetic data on adenosine triphosphate (ATP) hydrolysis catalyzed by the Zn²⁺ ion in the pH range 7.4–8.3 are analyzed by the method of numerical simulation. The rates of forward and reverse reactions of isomeric conversion of the open conformation of ZnATP^2– (Op), which is inactive in hydrolysis to ADP, to the active cyclic conformation ZnATP^2– (Cy) in the specified range of pH are proportional to the concentration of H₃O⁺ and characterized by the same rate constants as in the range of pH above 8.5. The mechanism of the isomeric conversion Op Cy involves the formation of a pentacovalent state at -P, pseudorotation, and the abstraction of OH^– from -P of the pentacovalent intermediate with the participation of H₃O⁺ in a slow step. The sequence of steps for the formation and transformation of intermediates, which was established earlier for the ZnATP^2– associates in the pH range 7.1–7.4, is applicable to this range of pH as well. In the analyzed range of pH, the contributions from the pH-independent channel of hydrolysis of the ZnATP^2– associates and the pH-dependent channel of CyOH^– and Op(OH^–)₂ species, which determine the formation of ADP and AMP at pH > 8.5, are comparable. Changes in the concentrations of intermediate products (monomeric and associates) in the course of hydrolysis are described. General base catalysis by a nitrogen base in the steps of formation of active centers for hydrolysis, the general acid catalysis of a coordinated water molecule, the exchange of medium OH^– with OH of -phosphate, the catalysis of conversion of the inactive conformation ZnATP^2– to the active one by a proton, and a change of the rate-limiting stage of hydrolysis with a change in pH indicate the enzyme-like mechanism of the reaction.     

Pulse radiolysis of pentacyanonitrosylferrate/II/ ions in aqueous solutions

Pulse radiolysis of aqueous solutions of sodium pentacyanonitrosylferrate/II/ Na₂[Fe/CN/₅NO] /sodium nitroprusside/ was studied in the presence of ethylene glycol as an OH radical scavenger. The rate constants of the one-electron reduction of nitroprusside ion were measured with e _q ^– and with radicals derived from some alcohols /ethylene glycol, ethanol, 2-propanol/ as reducing species. The results show that the transition state for the reduction by alcohol radicals is polar. The only observed product of reduction is the Fe/CN/₅NO^3– ion, which then undergoes a slow dissociation to form Fe/CN/₄NO^2–. Only a small isotope effect k_H/k_D=1.08 was observed in D₂O solutions for the dissociation reaction. This suggests an intramolecular electron transfer as rate-determining step for the dissociation reaction.Dedicated to Professor Schulte-Frohlinde on the occasion of his 60th birthday.     

Catalytic synthesis of propionic acid by carboxylation of ethylene with carbon dioxide

Conclusions The carboxylation of ethylene with CO₂ in the presence of tris (triphenylphosphine) rhodium chloride at 700 atm and 180° gave propionic acid, ethanol, and ethyl propionate in respective yields of 38.4, 24.3, and 11.2%, with an ethylene conversion of 91.4%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2814–2816, December, 1978.     

Catalytic Oxidative Deformylation of Polyethylene Glycols with the Participation of Molecular Oxygen

The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs) with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of –(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxidation were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to PEG 2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A^–···O₂], which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably, an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of PEG with a lower molecular weight.     

Structures and thermodynamic stabilities of the C2H4O isomers: Acetaldehyde,vinyl alcohol and ethylene oxide

Ab initio molecular orbital theory with a sequence of basis sets ranging from minimal to triple zeta plus polarization and with electron correlation incorporated using Möller-Plesset perturbation theory terminated at third order (MP3) is used to examine the structures and relative energies of the C₂H₄O isomers, acetaldehyde, vinyl alcohol and ethylene oxide. Acetaldehyde is indicated to be the most stable isomer with vinyl alcohol lying 45 kJ mol^–1 and ethylene oxide 114 kJ mol^–1 higher in energy. The theoretical structures and energies are in reasonable agreement with the best available experimental data.