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Catalytic hydrogenation of methyl methacrylate-g-natural rubber (MMA-g-NR) in the presence of OsHCl(CO)(O2)(PCy3)2

Paper ID Volume ID Publish Year Pages File Format Full-Text
43104 45955 2008 10 PDF Available
Title
Catalytic hydrogenation of methyl methacrylate-g-natural rubber (MMA-g-NR) in the presence of OsHCl(CO)(O2)(PCy3)2
Abstract

The graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out by using cumene hydroperoxide as redox initiator. The monomer conversion, grafting efficiency, and graft copolymer composition were examined. The purified graft copolymer was then hydrogenated by using a homogeneous osmium catalyst, OsHCl(CO)(O2)(PCy3)2. The purified graft copolymer and hydrogenated graft copolymer samples were characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. A detailed kinetic investigation of the hydrogenation was carried out by monitoring the amount of hydrogen consumption using a gas-uptake apparatus. The kinetic results for the hydrogenation of graft natural rubber indicated that the rate of hydrogenation exhibited a first-order dependence on the catalyst concentration. The hydrogenation exhibited a first-order dependence on hydrogen pressure which then decreased toward a zero-order dependence at higher hydrogen pressure. The addition of a small amount of acid provided a beneficial effect on the hydrogenation of grafted natural rubber. The hydrogenation rate was dependent on the reaction temperature and the apparent activation energy over the range of 120–160 °C was found to be 70.3 kJ/mol. The mechanistic aspects of these catalytic processes are discussed based on the observed kinetic results. Thermal properties of the grafted copolymer and hydrogenated grafted copolymer were also determined.

Graphical abstractNatural rubber grafted methyl methacrylate was hydrogenated using OsHCl(CO)(O2)(PCy3)2 as catalyst. A detailed kinetic investigation was carried out by monitoring the amount of hydrogen consumption. The kinetic results obtained were used to formulate a reaction mechanism for the hydrogenation process. The addition of acid provided a beneficial effect on the hydrogenation of grafted natural rubber.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Natural rubber; Hydrogenation; Osmium complex; Kinetics; Catalyst
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Catalytic hydrogenation of methyl methacrylate-g-natural rubber (MMA-g-NR) in the presence of OsHCl(CO)(O2)(PCy3)2
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 344, Issues 1–2, 15 July 2008, Pages 88–97
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
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