Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 C, autogenous pressure, batch reactor). The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt (15.5 h1 ) >Co(13.0 h1 ) >Ni(5.2 h1 ) while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt (53%)>Co(21%)>Ni (15%) as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co (as a result of the formed acids), significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.     

Electron paramagnetic resonance study of the TiCl4/Al(i-C4H9)3 system

Toluene solutions of titanium tetrachloride-triisobutyl aluminium varying in molar ratio from 1: 3 to 1: 30 are studied by electron paramagnetic resonance spectroscopy at 77 K. It is shown that the stepwise reduction of Ti(IV) to Ti(III) occurs under these conditions, resulting in the formation of TI ₂ ⁷⁺ and TI ₂ ⁶⁺ heterovalent compounds. A feasible mechanism for the interaction between TiCl₄ and Al(i-Bu)₃ is proposed.     

A study of hydroxyapatite nanocrystals by the multifrequency EPR and ENDOR spectroscopy methods

Specimens of powders of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) with average crystallite sizes in the range of 20–50 nm synthesized by the wet precipitation method have been investigated by the multifrequency (9 and 94 GHz) electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) methods. In specimens subjected to X-ray irradiation at room temperature, EPR signals that are caused by nitrogen compounds have been observed. Numerical calculations performed in terms of the density functional theory show that the observed EPR signal is caused by the occurrence of paramagnetic centers, the structure of which is NO ₃ ^2? and which replace the positions of PO ₄ ^3? in the hydroxyapatite structure.     

Functionalization of Csp3–H Bond of Methyl Substituent in Quinaldine with 5-Arylfuran-2,3-diones

Russian Journal of Organic Chemistry - New effective method of direct functionalization of Сsp3–H bond in methyl substituent of quinaldine under the action of 5-arylfuran-2,3-diones was...     

Comparison of Birch with electrochemical reduction of 2,3-diphenyl-1,4-diazaspiro[4.5]deca-1,3-diene

Reduction of 2,3-diphenyl-1,4-diazaspiro[4.5]deca-1,3-diene is investigated both voltammetrically (glassy-carbon electrode, 20 °C, non-aqueous-solvents) and using dissolving-metals (sodium, ?78 °C, tetrahydrofuran (THF)/NH₃(l)). Remarkably, electro-reduction furnishes two two-electron processes, whilst only a four-electron product results from Birch synthesis.     

Observing the orbital ordering of Ti(III) ions in catalysts for the polymerization of diene compounds

The orbital ordering of Ti(III) ions is observed via EPR spectroscopy for the catalytic system TiCl₄ + TIBA in an isopentane solution with an excess of organoaluminum compound. A model of the alternating ground states of 3d ¹ ions (d _xy and \(d_{z^2 }\) is proposed for the ordered structures. Ti(III) ions with the d _xy ground states are mono- and dialkylated.