An explanation for experimental behavior of hybrid metallocene silica-supported catalyst for ethylene polymerization

This work presents the results of homopolymerization of ethylene using an hybrid system (nBuCp)2ZrCl2-Cp2ZrCl 2, supported on silica. The catalytic systems were analyzed by RBS, DRIFTS and EXAFS and polyethylenes (PE) by GPC and DSC. The catalytic activities and the polymer properties showed dependence on the different ratio used (nBuCp)2ZrCl2/Cp2ZrCl2 at the preparation step. Theoretical studies permit us to conclude that the metallocenes interact with the surface in different ways. Depending on the addition order and the molar ratio between both metallocenes, distribution and nature of active species would be different. Possibility of binuclear active sites with different propagation and termination constants is analyzed and discussed. EHMO calculations allow us to conclude that Cp2ZrCl 2 has a strong affinity by AIS plane, whereas (nBuCp) 2ZrCl2 shows similar affinity for both silica planes.Fil: Aguiao Rodrigues, Silvia. Universidade Federal do Rio Grande do Sul; BrasilFil: Silveira, Fernando. Universidade Federal do Rio Grande do Sul; BrasilFil: dos Santos, J.H.Z.. Universidade Federal do Rio Grande do Sul; BrasilFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sal-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L-1 NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L-1) of embedded clay provide the highest corrosion protection. (C) 2014 Elsevier Inc. All rights reserved.Peer Reviewe

Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sal-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L-1 NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L-1) of embedded clay provide the highest corrosion protection. (C) 2014 Elsevier Inc. All rights reserved.Peer Reviewe

A methodology for improved operational optimization of water distribution systems

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