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Pacheco M.E.,Petrobras | Martins Salim V.M.,Programa de Engineering Quimica | Pinto J.C.,Programa de Engineering Quimica
Industrial and Engineering Chemistry Research | Year: 2011

Pilot plant experiments are designed to allow for evaluation of the impact caused by increasing the severity of key operation variables on deactivation of hydrotreating (HDT) catalysts, through accelerated runs performed in short periods of time. One of the main aspects of this work is the use of a kinetic approach in order to observe the impact of accelerated deactivation conditions upon catalyst performances during hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and aromatic hydrogenation (HDA) reactions. This approach allows for evaluation of catalyst deactivation for each of the analyzed reactions. Results obtained with a reference catalyst indicate that the proposed methodology is able to deactivate the catalyst effectively, leading to proper representation of actual industrial deactivation at the end of a catalyst life cycle. © 2011 American Chemical Society. Source

Peixoto L.S.,Programa de Engineering Quimica | Cordeiro F.B.,Federal University of Rio de Janeiro | Melo P.A.,Programa de Engineering Quimica | Nele M.,Federal University of Rio de Janeiro | Pinto J.C.,Programa de Engineering Quimica
Macromolecular Symposia | Year: 2011

Previous published works described suspension polymerization processes for the production of spherical core-shell poly(vinyl acetate)/poly(vinyl alcohol) (PVAc/PVA) particles with regular morphology for use as embolic agents in vascular embolization procedures. Although the clinical performance of the produced particles was regarded as excellent, the produced PVAc/PVA particles were prone to agglomeration during storage. For this reason, methyl methacrylate is now used as comonomer in order to increase the glass transition temperature of the final product and prevent agglomeration of polymer particles. The final expansion of particles, intended to control the density of the polymer beads, also exerts a beneficial effect on the rate of particle agglomeration. Therefore, a methodology to obtain spherical poly(vinyl acetate)-co-poly(methyl methacrylate)/poly(vinyl alcohol) (PVAc-co-PMMA/PVA) particles with core-shell structure is presented in this work. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Pereira H.L.,Programa de Engineering Quimica | MacHado F.,Programa de Engineering Quimica | MacHado F.,University of Brasilia | Lima E.L.,Programa de Engineering Quimica | Pinto J.C.,Programa de Engineering Quimica
Macromolecular Symposia | Year: 2011

Near infrared spectroscopy (NIRS) is widely used for determination of polymer properties through in line and real time monitoring of polymerization reactions. Experimental runs were performed to evaluate whether NIRS can be used to monitor vinyl acetate/acrylic acid (VAc/AA) copolymerizations carried out in suspension reactors. It is shown that NIRS can be used successfully to monitor the evolution of VAc/AA suspension copolymerizations and that very good calibration models can be developed for monitoring of composition trajectories along the batch. Therefore, NIRS can be employed for real time monitoring and control of copolymer composition in VAc/AA copolymerizations performed in suspension reactors. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Oliveira M.A.M.,Programa de Engineering Quimica | Melo Jr. P.A.,Programa de Engineering Quimica | Nele M.,Programa de Engineering Quimica | Pinto J.C.,Programa de Engineering Quimica
Macromolecular Symposia | Year: 2011

Embolization is a radiological technique that consists in occluding a blood vessel intentionally with an embolic agent (particle). A suspension polymerization process was developed to allow for production of embolic particles with core-shell morphology. This technology was modified to allow for the in-situ incorporation of antibiotics (amoxicillin) in PVA/PVAc-co-PMMA core-shell particles. The incorporation of amoxicillin led to modification of some of the final polymer properties, including the particle morphology, the molecular weight distribution and the characteristic transition temperatures of the polymer material. The final polymer properties depended on the antibiotic concentration and on how the drug was added into the polymerization medium. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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