Suspended chrome catalyst containing titanium and the use thereof for producing ethylene homopolymers and copolymers
Novel supported, titanized chromium catalysts can be used for the homopolymerization of ethylene and the copolymerization of ethylene with α-olefins.
1. A process for preparing supported, titanized chromium catalysts, which comprises the following steps:
A) bringing a spherical, spray-dried, oxidic support material into contact wit a titanium compound in a suspension,
B) bringing the support material which has been treated in this way into contact with a chromium salt solution in a suspension and subsequently removing the solvent,
C) optionally, calcining the precatalyst obtained in step B) at above 280° in an inert gas atmosphere and subsequently
D) activating the precatalyst obtained in step B) or C) at from 500° C. to 800° C. in an oxygen-containing atmosphere.
2. The process of claim 1 , wherein the oxidic support material used is a silica gel.
3. The process of claim 1 , wherein the pore volume of the support material is from 0.5 to 3 ml/g.
4. The process of claim 1 , wherein the specific surface area of the support material is from 50 to 600 m 2 /g.
5. The process of claim 1 , wherein the mean particle size of the support material is from 1 to 1000 μm.
6. The process of claim 1 , wherein the support material is slurried with an acid before being brought into contact with the titanium compound.
7. A process for preparing homopolymers of ethylene and copolymers of ethylene wit α-olefins, by polymerization of ethylene or of mixtures of ethylene and α-olefins, which comprises preparing a supported, titanized chromium catalyst by the process of claim 1 and carrying out the polymerization in the presence of the supported, titanized chromium catalyst.
8. The process of claim 7 , wherein the polymerization is carried out in the presence of the supported, titanized chromium catalyst and a supported, nontitanized chromium catalyst which is prepared by a process in which a spherical, spray-dried support material is treated as described in steps B) to D).
9. The process of claim 7 , wherein the polymerization is carried out in the gas phase.