GB886893A - Purification of olefines for low-pressure polymerisation - Google Patents

Abstract

Olefins containing 2-4 carbon atoms are purified, prior to low pressure polymerization, with a purification mass containing chromium trioxide at -20 to 60 DEG C. The olefin is preferably prepurified to less than 1% impurities. The chromium trioxide may be a conventional polymerization catalyst, e.g. supported on alumina, aluminium silicate, magnesium silicate or silica gel and forming 1-10% by weight of the carrier. The mass may be diluted with polyethylene, polypropylene, alumina, aluminium or magnesium silicate or silica gel, and may be used in fixed or fluidized beds in continuous processes. Internal or external cooling may be applied, 'e.g. by decompression in the purifying tower from 50-60 down to 20-30 atmospheres. The purified olefin, e.g. ethylene or propylene, may be conventionally polymerized with a chromium trioxide or other low pressure catalyst, e.g. TiCl4 and Al(C2H5)3.ALSO:Olefins containing 2 to 4 carbon atoms are purified by contact with a purification mass containing chromium trioxide at -20 DEG C. to 60 DEG C. The olefin may be first purified conventionally, e.g. with caustic potash, alumina, silica gel or diethyl zinc and preferably contains less than 1% of impurities. The chromium trioxide may be present in an amount of 1%-10% by weight of a carrier, e.g. alumina, aluminium sili ate, magnesium silicate or silica gel and the mass may be diluted with an inert solid, e.g. polyethylene, polypropylene, alumina, aluminium silicates, magnesium silicate, iron oxide or silica gel. In batch processes the amount of the mass may be 0.01%-150% by weight of the olefin and in continuous processes may be in a fixed or fluidised bed; it may be regenerated by oxidation. Internal or external cooling may be applied, e.g. by reducing the pressure from 50-60 atmospheres down to 20-30 atmospheres.