| 摘要 |
Ethylene may be polymerized, optionally with another olefin, at 100 DEG to 500 DEG F. to normally solid polymers in the presence of a catalyst prepared by a process which comprises depositing chromium oxide or a compound calcinable thereto on a support consisting of silica, alumina, thoria or zirconia, at least part of the chromium in the catalyst being in the hexavalent state and said support having been heated with hydrated aluminium fluoride to increase the polymerizing activity of the catalyst. The heating with aluminium fluoride may be effected before or after the deposition of the chromium compound. Specified other olefins are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl pentene-1, 1,3-butadiene and isoprene. The polymerization may be effected in the gaseous phase, liquid phase or mixed phase, preferably in the presence of an inert hydrocarbon liquid diluent. The catalyst may be activated by heating with an oxygen containing gas such as air. Examples describe the polymerization of ethylene (I, II and III) and the copolymerization of ethylene and 1-butene (III) in n-pentane in the presence of a chromium trioxide, silicaalumina, hydrated aluminium fluoride catalyst activated by heating with air; and the polymerization of ethylene (IV) in the presence of chromium trioxide, silica, hydrated aluminium fluoride and chromium trioxide, alumina, hydrated aluminium fluoride catalysts activated by heating in air. Similar results are said to be obtained using zirconia and thoria supports. |
