Method for preparing a Ziegler-Natta catalyst
View Patent ↗A method for preparing a titanium-containing Ziegler-Natta catalyst is disclosed. A dialkyl magnesium compound, a trialkyl aluminum compound, and a polymethylhydrosiloxane are first combined in a hydrocarbon solvent. That product is then combined with dry, alcohol-free magnesium chloride. A solid product from the reaction with the magnesium chloride component is isolated and washed with a hydrocarbon solvent. The washed solid product is then combined with an alkyl aluminum dichloride or a dialkyl aluminum chloride to give the catalyst. The catalyst is suitable for both slurry and gas-phase olefin polymerizations. Polyolefins produced with the catalyst have broad molecular weight distributions and narrow distributions of relatively large particles.
1. A method for preparing a titanium-containing Ziegler-Natta catalyst, said method comprising:
a) combining a dialkyl magnesium compound, a trialkyl aluminum compound, and a polymethylhydrosiloxane in a first hydrocarbon solvent;
b) combining the product from step (a) with dry, alcohol-free magnesium chloride;
c) washing a solid product isolated from step (b) with a second hydrocarbon solvent; and
d) combining the washed solid product with an aluminum compound selected from the group consisting of alkyl aluminum dichlorides and dialkyl aluminum chlorides to give the catalyst;
wherein titanium is introduced as a titanium alkoxide in step (a), during preparation of the magnesium chloride used in step (b), or both.
2. The method of claim 1 wherein the magnesium chloride has an average particle size within the range of 5 and 100 microns.
3. The method of claim 1 wherein step (a) includes a titanium alkoxide.
4. The method of claim 1 wherein the magnesium chloride is a titanium-modified material made by reacting a magnesium chloride alcoholate with titanium tetrachloride.
5. The method of claim 1 further comprising washing the catalyst from step (d) with a third hydrocarbon solvent.
6. The method of claim 1 wherein the first and second hydrocarbon solvents are the same.
7. A process which comprises polymerizing an olefin in the presence of a catalyst prepared by the method of claim 1 .
8. A gas-phase process of claim 7 .
9. A slurry process of claim 7 .
10. A catalyst prepared by the method of claim 1 .