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Adriano G. Fisch - One of the best experts on this subject based on the ideXlab platform.
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Effects of the Ethoxide in the Coordination Sphere of Titanium on the Performance of MgCl2-Based Ziegler–Natta Catalyst
Industrial & Engineering Chemistry Research, 2018Co-Authors: Adriano G. FischAbstract:Traditional formulations of Ziegler–Natta catalysts that are based on magnesium Ethoxide tend to generate titanium moieties presenting Ethoxide ligand. It is suggested that the Ethoxide group in the coordination sphere of titanium affects the catalyst activity and molecular weight distribution of the produced polymer. In the present work, a systematic synthesis of catalyst and chemical characterizations were accomplished with the objective of identifying correlations between the active sites presenting Ethoxide as ligand and the performance of the catalyst in terms of activity and average molecular weight. Octahedral and trigonal-bipyramidal titanium moieties were identified as two groups of active sites in the catalyst. The Ethoxide group as a ligand of the titanium was found in octahedral moieties only. Trigonal-bipyramidal titanium moieties have preferentially chlorine as ligands.
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effects of the Ethoxide in the coordination sphere of titanium on the performance of mgcl2 based ziegler natta catalyst
Industrial & Engineering Chemistry Research, 2018Co-Authors: Adriano G. FischAbstract:Traditional formulations of Ziegler–Natta catalysts that are based on magnesium Ethoxide tend to generate titanium moieties presenting Ethoxide ligand. It is suggested that the Ethoxide group in the coordination sphere of titanium affects the catalyst activity and molecular weight distribution of the produced polymer. In the present work, a systematic synthesis of catalyst and chemical characterizations were accomplished with the objective of identifying correlations between the active sites presenting Ethoxide as ligand and the performance of the catalyst in terms of activity and average molecular weight. Octahedral and trigonal-bipyramidal titanium moieties were identified as two groups of active sites in the catalyst. The Ethoxide group as a ligand of the titanium was found in octahedral moieties only. Trigonal-bipyramidal titanium moieties have preferentially chlorine as ligands.
Lorraine Falter Francis - One of the best experts on this subject based on the ideXlab platform.
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Dip coating of titanium Ethoxide solutions
Materials Letters, 1993Co-Authors: Edward A. Hachfeld, Young-joo Kim, Lorraine Falter FrancisAbstract:Titania coatings are prepared by dip coating anhydrous titanium Ethoxide solutions on glass substrates. Titanium Ethoxide reacts with atmospheric water during deposition and drying to form coatings with a variety of microstructures. Transparent gel layers are prepared by coating in dry nitrogen and then exposing the coating to humid atmosphere or using slow withdrawal rates. Hydrated titania particles form in coatings deposited in atmospheres with relative humidity levels greater than ≈ 15%. These coatings are typically composed of agglomerates of small particles (≈0.3 μm); increases in substrate withdrawal rate and Ti Ethoxide concentration in the solution bath lead to increases in thickness, particle size and extent of agglomeration. Particle aggregation is prevented by adding hydroxypropyl cellulose (HPC) to the coating solution before deposition. © 1993.
Edward A. Hachfeld - One of the best experts on this subject based on the ideXlab platform.
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Dip coating of titanium Ethoxide solutions
Materials Letters, 1993Co-Authors: Edward A. Hachfeld, Young-joo Kim, Lorraine Falter FrancisAbstract:Titania coatings are prepared by dip coating anhydrous titanium Ethoxide solutions on glass substrates. Titanium Ethoxide reacts with atmospheric water during deposition and drying to form coatings with a variety of microstructures. Transparent gel layers are prepared by coating in dry nitrogen and then exposing the coating to humid atmosphere or using slow withdrawal rates. Hydrated titania particles form in coatings deposited in atmospheres with relative humidity levels greater than ≈ 15%. These coatings are typically composed of agglomerates of small particles (≈0.3 μm); increases in substrate withdrawal rate and Ti Ethoxide concentration in the solution bath lead to increases in thickness, particle size and extent of agglomeration. Particle aggregation is prevented by adding hydroxypropyl cellulose (HPC) to the coating solution before deposition. © 1993.
V. Ganesan - One of the best experts on this subject based on the ideXlab platform.
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Kinetics of thermal decomposition of sodium mEthoxide and Ethoxide
Journal of Nuclear Materials, 2006Co-Authors: K. Chandran, M. Kamruddin, P.k. Ajikumar, Anantha Iyengar Gopalan, V. GanesanAbstract:Abstract Sodium mEthoxide and sodium Ethoxide were synthesized. Their thermal decomposition and reaction kinetics were investigated under non-isothermal and isothermal conditions. Non-isothermal experiments were carried out at different linear heating rates. Kinetics of decomposition in each run was evaluated from the dynamic TGA and MS data obtained from thermogravimetric analyzer (TGA) coupled with mass spectrometer based evolved gas analyzer (EGA–MS). The activation energies derived from isothermal experiments by Arrhenius plot were 187.81 ± 11.22 and 150.84 ± 5.32 kJ mol −1 for sodium mEthoxide and sodium Ethoxide, respectively, which agree well with the values from non-isothermal method. The evolved gases were found to be a mixture of saturated and unsaturated hydrocarbons. XRD, IR, AES, CHNS analyzer and volumetric estimation were employed to characterize the decomposition residue and identified as a mixture of sodium carbonate, sodium hydroxide and amorphous carbon. The probable mechanism and kinetics of decomposition of sodium alkoxides described in this paper are reported for the first time.
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Heat capacity measurements on sodium alkoxides
Thermochimica Acta, 2005Co-Authors: K. Chandran, Anantha Iyengar Gopalan, R. Venkata Krishnan, K. Nagarajan, V. GanesanAbstract:Heat capacity measurements of sodium alkoxides, namely sodium mEthoxide, sodium Ethoxide, sodium n-propoxide and sodium iso-propoxide were carried out using differential scanning calorimetry (DSC) in the temperature range 240–550 K. From the heat capacity values, other thermodynamic functions, such as enthalpy increments, entropies and Gibbs energy functions of these compounds were derived and reported for the first time. The Cp,m 298 of sodium mEthoxide, sodium Ethoxide, sodium n-propoxide and sodium iso-propoxide were measured and found to be 65.05, 90.87, 113.52 and 121.20 J K −1 mol −1 respectively. © 2005 Elsevier B.V. All rights reserved.
Andrew J. Gellman - One of the best experts on this subject based on the ideXlab platform.
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Quantitative adsorbate orientation from vibrational spectra: Ethoxides on Cu(111)
The Journal of Chemical Physics, 1996Co-Authors: Shane C. Street, Andrew J. GellmanAbstract:Fourier‐transform infrared reflection absorption spectra have been obtained for a set of deuterium and isotopic carbon (13C) labeled Ethoxides adsorbed on the Cu(111) surface at saturation coverages. The frequency shifts upon 13C isotopic replacement indicate that the proper description of the skeletal stretches is in terms of CCO modes and not local modes of CO and CC bonds. Comparison of the spectra of the deuterated Ethoxides with gas phase and multilayer spectra of the corresponding ethanols allowed the determination of the orientation of the adsorbed Ethoxide. A solution for the average structure of Ethoxide shows that the plane of the species is tilted 17±2° from the plane of the surface normal and that the C–C bond, is tilted 70±2° from the surface normal. The tilt of the C–O bond from the surface normal is 17±2°. At elevated temperatures the Ethoxides undergo β‐hydride elimination and desorb as acetaldehydes. Temperature programmed reaction spectra for β‐hydride elimination of the selectively deut...
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FT-IRAS of Adsorbed Alkoxides: Fluorinated Ethoxides on Cu(111)
The Journal of Physical Chemistry, 1996Co-Authors: Shane C. Street, Andrew J. GellmanAbstract:Fourier transform infrared reflection absorption spectra (FT-IRAS) of a set of fluorinated Ethoxides (CFnH3-nCH2OH, n = 0−3) on the Cu(111) surface have been obtained. The decomposition reactions of adsorbed mono-, di-, and trifluoroEthoxide to gaseous fluoroaldehydes exhibit different reaction kinetics, as previously reported, and the reaction of trifluoroEthoxide-d2 (CF3CD2O−Cu(111)) exhibits a primary isotope effect. Quantitative measurements of the absorption intensities of CF3CH2O(ad) and CF3CH2OH allowed determination of the orientation of the adsorbed trifluoroEthoxide. FT-IRAS results indicate that the orientation of trifluoroEthoxide is different than that of Ethoxide. Ethoxide on the Cu(111) surface has the C−C bond tilted 70 ± 2° from the surface normal while in trifluoroEthoxide the C−C bond is oriented 50 ± 5° from the surface normal. In both species the plane of the molecule defined by the C−C−O atoms is tilted toward the surface. This tilt between the plane of the molecule and the plane of ...
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FT-IRAS of adsorbed alkoxides: Ethoxides on Cu(111)
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1995Co-Authors: Shane C. Street, Andrew J. GellmanAbstract:Abstract The Fourier-transform infrared reflection adsorption spectra (FT-IRAS) are presented for a set of deuterium-labelled Ethoxides on Cu(111). Stable Ethoxides are formed by deprotonation of the corresponding ethanols on the preoxidized Cu(111) surface. Comparison of the Ethoxide vibrational spectra with those of gas phase ethanols and multilayer ethanols on Cu(111) allowed a detailed assignment of the Ethoxide spectra. The surface selection rules for IRAS were used to determine the average orientation of the adsorbed Ethoxide. Comparing the spectra of Ethoxide and the deuterated Ethoxides in the CD and CH stretch regions shows the presence of a weak asymmetric methylene group stretch ( ν a (CH 2 )) and a loss in intensity of the symmetric methyl group stretch ( ν a (CH 3 )) with respect to the same mode in the multilayer. These FT-IRAS results indicate that Ethoxide has the C 3v axis of the methyl group, and hence the CC bond, oriented roughly parallel with the surface, and the plane of the molecule, defined by the CCO atoms, tilted away from the surface normal.