| 摘要 |
<p>An olefin polymerization catalyst comprises Al2O3, SiO2 and one or more oxygen-containing compounds of Mo, the latter being in a valency state below 6. Co is an optional ingredient and may be added e.g. as Co molybdate. The proportion of Al2O3 in the Al2O3-SiO2 is (in the Provisional Specification 1-80) 5-65, preferably 10-50, especially 15-40, e.g. 12 or 25 wt. per cent. Preferably the Mo compound is introduced as a hexavalent compound and reduced with a gas such as hydrogen, carbon monoxide or a hydrocarbon at above 300 DEG C., particularly below 650 DEG C., especially 400-550 DEG C., e.g. 500 DEG C.; prior to impregnation, the Al2O3-SiO2 may be activated at 500-750 DEG C. using air, other oxygen containing gas or inert gas, preferably together with water vapour. In the examples, ammonium molybdate solution is absorbed on the silica alumina and the product heated at 500 DEG C. prior to reduction with H2. The catalyst is preferably employed in a liquid hydrocarbon medium, but in the absence thereof may be fluidized or used in a fixed or moving bed. The catalyst is reactivated, after cleansing with solvents (e.g. hydrocarbons or chlorinated hydrocarbons) by "conditioning," i.e. reducing the catalyst (as above) but at lower temperatures (e.g. below 300 DEG C., even below 100 DEG C.), if necessary burning off combustible deposits prior to said "conditioning." The catalyst may be in the form of cylinders, spheres, coarse grains or lumps, but preferably comprises microspheroidal grains of 100-200, e.g. 20-120 microns. The starting material may be e.g. a treated clay or preferably a commercial cracking catalyst.ALSO:C2-C5 olefins, specifically ethylene and propylene, are polymerized in presence of a catalyst comprising at least one oxygen-containing Mo compound wherein the valency of Mo is below 6 (such as MoO3 reduced with H2), the oxides of Al (5-65 wt. per cent) and of Si (35-95 wt. per cent), and optionally minor quantities of other elements such as Co. The reaction is carried out either in absence, or, preferably, in presence, of aliphatic, cycloaliphatic or aromatic solvents (iso-octane is used in examples).</p> |
