INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
artículos
Título:
Metallocene supported on a polyhedral oligomeric silsesquioxane (POSS) modified silica: structural characterizayion and catalytic activity for ethylene polymerization
Autor/es:
IVAN GARCÍA-OROZCO; TERESA VELILLA; GRISELDA B. GALLAND; JOAO HENRIQUE Z. DOS SANTOS; ROBERTO J. J. WILLIAMS; RAÚL QUIJADA
Revista:
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
Editorial:
JOHN WILEY & SONS INC
Referencias:
Lugar: New York; Año: 2010 vol. 48 p. 5938 - 5944
ISSN:
0887-624X
Resumen:
Preliminary results on the activity
of metallocene supported over a polyhedral oligomeric silsesquioxane
(POSS)-modified silica for ethylene polymerization (D. Bianchini et al., J
Polym Sci, A: Polym Chem 2005, 43, 5465 ), were extended showing the effect of
large variations of the amount of both POSS
and metallocene on the catalyst activity. DRIFT results showed that at low
concentrations (< 1 wt %), POSS was
physically adsorbed on SiOH groups present in the silica surface through
H-bonds. At larger concentrations POSS was adsorbed by covalent bonds with the
silica surface. The metallocene catalyst was adsorbed either on the silica
surface by interactions with residual SiOH groups or inthe organic branches of the metallocene. It was found that the highest
contribution to the catalyst activity arose from the metallocene directly
adsorbed on the silica support. The effect of POSS to increase the catalyst
activity was mainly due to its effect as a horizontal spacer of metallocene
molecules adsorbed on the silica surface. An optimum range of POSS and
metallocene adsorbed on the silica support was found that gave catalyst
activities close to the one of the homogeneous system while doubling the molar
mass of the PE produced.