Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

Hydrogenation of benzene to cyclohexane catalyzed by rhodium(I) complex supported on montmorillonite clay

[Rh(I)PPh₃]⁺ intercelated in the interlamellars of montmorillonite clay catalyzes the hydrogenation of benzene to cyclohexane at 70°C and 20 atm hydrogen pressure.

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[Rh(I)PPh₃)]⁺, -, - 70°C –20 .

     

Asymmetric hydrogenation of carbonyl group in the presence of modified ruthenium catalyst

Conclusions The hydrogenation of acetoacetic ester in the presence of ruthenium, deposited on silica gel, modified with D-tartaric acid at pH 4.2–5.9, yields the (–)--hydroxybutyrate, which possesses optical activity. The highest asymmetric yield is observed when the modifying solution has a pH of 5.5.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1803–1804, August, 1971.     

Hydrogenation of unsaturated compounds in the presence of palladium-containing modified carbon nanofibers

Palladium-containing carboxylated carbon nanofibers were studied as catalysts for hydrogenation of double bond >C=C< in olefins, unsaturated alcohols, and acids, as well as for hydrogenation of nitroarenes. The developed catalyst is 7 times more efficient than the industrial analog (Pd/C).     

Hydrogenation of olefins on Ru/pillared montmorillonite

Hydrogenation reactions of olefinic hydrocarbons using ruthenium-incorporated pillared montmorillonite as catalysts are reported. Depending on the steric hindrance, Ru/pillared montmorillonite selectively reduces carbon-carbon double bonds using hydrogen under pressure.     

Hydrogenation of carbon monoxide in the presence of homogeneous ruthenium catalysts: effects of onium halides as promoters

The direct formation of ethylene glycol and ethanol from synthesis gas in the presence of a homogeneous ruthenium carbonyl catalyst is promoted by onium halides, such as ammonium, phosphonium and iminium halides. The catalytic activities for ethylene glycol and ethanol formation are dependent on the nature of the halides, and increase in the order I⁻ < Br⁻ < Cl⁻ and Cl⁻ < I⁻ ≤ Br⁻, respectively. The ruthenium catalyst in conjunction with (Ph₃P)₂NCl shows the highest activity for ethylene glycol formation. The catalytic activities are dependent on the electron-accepting abilities of the solvents. A moderate electron-accepting ability of the solvent is important for oxygenate formation.     

Heats of adsorption of benzene and toluene vapors on polyhydroxyaluminum montmorillonite

Changes that occur in the surface properties and porous structure of montmorillonite when sodium ions are replaced with polyhydroxyaluminum ions are studied. It is established that thermal evacuation significantly affects the adsorption and energy properties of polyhydroxyaluminum montmorillonite (PHAM). The dependences of the differential isosteric heats of adsorption and desorption on the amount of adsorbed substance are determined from data on a series of isosteres for the sorption of benzene and toluene on dehydrated PHAMs, where the curves of the heats of sorption of C₆H₆ and C₇H₈ are of an extreme character. It is concluded that the occurrence of maxima is determined by the interaction between molecules of adsorbates and active centers (and with one another) due to packing upon the filling of the volumes of slittype micropores.     

Kinetics of styrene emulsion polymerization in the presence of montmorillonite

The effect of the pristine sodium montmorillonite (Na⁺-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na⁺-MMT compared to the counterpart without Na⁺-MMT. Micelle nucleation predominates in the polymerizations with [SDS] ≧ 13 mM. On the other hand, the contribution of the polymerization associated with the Na⁺-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the Na⁺-MMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na⁺-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na⁺-MMT.     

Hydrogen adsorption on silicalite in the presence of water and benzene

¹H NMR techniques in the temperature range 200–280 K under isobaric conditions are used to investigate concurrent adsorption of hydrogen and water in the pores of silicalite, a microporous silica. The possibility for a small (up to a few weight percent) quantity of water to exist in the pores is demonstrated. Water is found to exist in the form of two types of cluster structures differing in the degree of water association. A conclusion about the stabilization of the weakly associated form by weakly polar organic molecules is made. Water is shown to promote the hydrogen adsorption process; when its concentration is c _H2O = 2 wt %, adsorption increases more than twofold. A suggestion that this effect is caused by the formation of water-hydrogen cluster structures in the pores is made.     

Adsorption of ethanol on the modified ruthenium catalysts in alkaline media

Regularities of ethanol adsorption in alkaline medium on the surface of the monoruthenium Ru/C catalyst and systems promoted by nickel and vanadium oxides, Ru-VO _x /C and Ru-NiO _x /C, were studied by non-stationary voltammetry techniques. An analysis of the kinetic and concentration dependences of adsorption showed that an increase in the content of the promoting component in the bimetallic systems enhances the energy heterogeneity of the catalyst surface. The data on adsorption measurements were compared with the results of previous studies of the kinetics and depth of ethanol electrooxidation on the examined catalysts. The larger quantity of electricity consumed for the oxidation of adsorbed particles formed on the surface of the metallooxide systems corresponds to higher extents of electrooxidation and rate than those for the monoruthenium catalyst.     

TG characterization of organically modified montmorillonite

Montmorillonite was modified with octadecyltrimethylammonium chloride, under different reaction conditions, as evidenced by TG and XRD. TG curves presented two degradation peaks (295 and 395°C). At low salt concentrations, only the 395°C-degradation appeared, which increased with reaction time to the limit of 9 g of salt/100 g of clay. The second peak presented a limit at 17/100 m/m of salt/clay ratio. XRD analysis confirmed clay organic modification as the basal distance increased, showing greater reaction time effect than the salt mass effect, and with only one d-spacing. This suggested that an intercalation complex was formed but also that octadecyltrimethylammonium was adsorbed on the external surfaces of clay particles. This revised version was published online in August 2006 with corrections to the Cover Date.     

A study of ruthenium catalysts on fluoride support

The surface and catalytic properties of magnesium fluoride supported ruthenium catalysts have been studied. IR and EPR results for adsorption of probe molecules (CO, O₂) indicate the existence of both Ru⁰ and Ru⁺ clusters. The Ru/MgF₂ system was found to be very active in redox reactions.     

Electron affinity of modified benzene

The electron affinities of organic molecules obeying Hückel's rule of aromaticity are vanishingly small, if not negative. For example, benzene, a classic example of an aromatic molecule, has an electron affinity of −1.15 eV. Using density functional theory, we have systematically calculated the electron affinities and vertical detachment energies of C₆H₆ by substituting H with halogen (F) and superhalogen (BO₂) moieties, as well as replacing one of the C atoms with B. The ground state geometries were obtained by examining about 330 isomers. The electron affinities are found to steadily increase with these substitutions/replacements, even surpassing that of Cl, the element with the highest electron affinity in the periodic table, in the case of C₅BH(BO₂)₅. In some special cases such as C₆H₅(BO₂) the electron affinity and vertical detachment energy differ by as much as 5 eV, indicating substantial changes in the geometry as the electron is removed from the anion. We hope that the ability to change the negative electron affinity of C₆H₆ to large positive values by substituting H and/or replacing C atom will motivate experimental studies.