A study of various characteristics of supported NiO/bentonite catalyst used in the polymerization of methyl methacrylate

• Published in: Journal of materials science 1989-03, Vol.24 (3), p.1095-1102
• Main Authors: HASSAN, S. A, SELIM, S. A, MEKEWI, M. A, HANAFI, S
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF01148804

Several samples of a supported NiO/bentonite catalyst were studied after pretreatment at either 300 or 500 deg C. The TGA results revealed that at 300 deg C, a fraction of nickel nitrite remains stabilized by the bentonite matrix. This fraction reaches its maximum level in samples IVa and Va (or 15 and 20 wt.% NiO, respectively). From a study of the surface characteristics, it could be concluded that the nitrite fraction is located in the narrower pores of the catalyst system. The activity tested in the polymerization of MMA indicated that samples IVa and Va are the most active ones. The importance of the surface factor and the degree of fractional surface coverage by Ni exp 2+ ions, or equivalently by the corresponding anions, could be tested. The results showed that the polymerization process proceeds via an anionic mechanism as enhanced by the presence of NO exp -- sub 2 ions; the effect becoming much more pronounced in samples IVa and Va. The high stereospecific nature of the produced polymer in all cases can be attributed to the bentonite support effect, being activated by dispersing nickel oxide or other Ni species in its layer structure at both temperatures studied. 24 ref.--AA