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New Chromium on Silica Gel Catalysts with very high activity for the polymerization of ethylene
Author(s) -
Rebenstorf B.
Publication year - 1984
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19845130611
Subject(s) - chromium , catalysis , polymerization , silica gel , ethylene , chemistry , absorbance , inorganic chemistry , polymer , polymer chemistry , nuclear chemistry , organic chemistry , chromatography
Together with the known chromium (II)/silica gel catalyst (Phillips catalyst) for the polymerization of ethylene, two new ones have been investigated. It was found that a chromium(II)‐“repoly” catalyst (prepared by short reaction of the chromium(II)/silica gel with ethylene at temperatures between 100 and 225°C) and a chromium(III)/silica gel catalyst have up to hundred times higher activity than the chromium(II) one. Activation energies were calculated as 54.6, 49.6 and 43.8 kJ per mol, respectively. The number of active sites was determined by measuring the integrated absorbance of the CH and CO stretching vibrations of the polymer. At low chromium concentration (0.056%) roughly 50% of all chromium was catalytically active in the case of chromium(II) and chromium(III) on silica gel. For the chromium(II)‐“repoly” catalyst all chromium atoms can be active. The turnover numbers for the polymerization at 20°C were calculated as 0.1 (chromium(II)), 7.5 (chromium(II)‐“repoly”) and 20 (sec −1 atm −1 ) (chromium(III)).