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Application of Sonotriboluminescence to Determine Arene Molecules in Hydrocarbons

The sonotriboluminescence of suspensions of terbium(III) and europium(III) sulfates in decane without and in the presence of benzene, toluene and p-xylene was studied. The choice of crystals of these lanthanides is due to the fact that they have intense luminescence during mechanical action, and also do not dissolve in hydrocarbon solvents. During ultrasonic exposure to suspensions in pure alkanes, bands of Ln3+ ions and N2 in the UV region are recorded in the luminescence spectrum. When aromatic hydrocarbon molecules are added, bands of benzene, toluene and p-xylene molecules, coinciding with their photoluminescence spectra, are recorded in the sonotriboluminescence spectra in the UV region. The high sensitivity of the luminescence of suspensions to arene additives made it possible to obtain the dependence of the characteristic fluorescence of arene molecules in the sonotriboluminescence spectra on their concentration in suspensions. The limits of detection of benzene, toluene and p-xylene in the composition of this suspension were established. The lower limits of detection from the sonotriboluminescence spectra for xylene, toluene and benzene are 0.1, 3 and 50 ppmv, respectively. Fluorescence bands of these molecules were also recorded in the sonotriboluminescence spectra of suspensions in commercial dodecane and heptane with additives of commercial gasoline (up to 1%). The results obtained can be used for luminescent detection of aromatic compounds in saturated hydrocarbons.

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Activation of metallocene hydride intermediates by methylaluminoxane in alkene dimerization and oligomerization

Abstract Homogeneous catalytic systems based on metallocenes, organoaluminum compounds, and activators proved to be efficient in alkene dimerization, oligomerization, and polymerization reactions. Metal hydrides can act as highly reactive species of these catalytic systems. Despite the large number of experimental and theoretical studies in this field, the effect of the activator on the structure and dynamics of hydride intermediates is an open question. In order to elucidate the dependence of the structure and reactivity of the bimetallic hydride intermediates formed in the systems metal complex – OAC – activator on the nature of the transition metal atom and ligand environment, we used NMR spectroscopy to study reactions of a series of L2MCl2 complexes (M = Hf, Zr; L2 = Cp2, CpMe2, ansa-(Me2C)2Cp2, ansa-Me2CInd2) with HAlBui2 and ММАО-12 activator. As a result, M,Al-bimetallic intermediates containing [L2ZrH3] and [(L2Zr)2H3] type moieties were detected for both hafnium and zirconium complexes with cyclopentadienyl ligands. The [L2ZrH3] type structure predominates in the system based on the ansa-linked bis-indenyl zirconium complex. The detected complexes provide associates with ММАО-12 and, hence, they can act as precursors of active sites determining the alkene dimerization and oligomerization routes.

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