| 摘要 |
FIELD: polymerization catalysts. ^ SUBSTANCE: invention relates to chromium oxide catalysts on inorganic carriers as components of double catalytic systems also including supported chromocene catalyst and used for synthesis of high-strength, crack-resisting low-pressure polyethylene. According to invention, preparation procedure comprises preliminarily drying silica (carrier), applying chromium and aluminum compounds thereon from solutions in organic solvent, removing solvent, drying resulting product and subsequent thermal-oxidative activation in dry air flow within temperature range between 450 and 750°C. Long-term polymerization activity of double catalytic system is achieved owing to using, as aluminum compound solution, solution of alkoxyalumoxane of general formula [Al(OR)n (OR')1-nO]m, where R denotes ethyl or isopropyl, R' group C6H9O2, n = 0.6 or 0.7, and m = 2-5, in water-free lower aliphatic alcohol and. as chromium compound solution, solution of dicyclopentadienylchromium in toluene, and preliminary drying of silica is carried out in fluidized bed in presence of ammonium hexafluorosilicate at constant temperature within the range 330-400°C. Invention is also characterized by that thermal-oxidative activation of catalytic product is followed by thermal-reductive activation thereof in flow of purified nitrogen mixed with dry carbon dioxide at constant temperature within the range 350-390°C. ^ EFFECT: prolonged long-term catalytic activity. ^ 3 tbl, 22 ex |
