Catalyst for propylene polymerization

Abstract

A polypropylene catalyst (no more than 2 wt % titanium) contains at least one titanium-halogen bond-containing compound, internal donor, and activated, amorphous magnesium dihalide support, essentially free of alkoxy functionality. It is made by combining and heating titanium tetrachloride, magnesium halide precursor compound, and internal electron donor, in alkylbenzene solvent, to form an intermediate product; washing that product with an aromatic hydrocarbon solvent at elevated temperature producing a washed product; decantation of supernatant; treating the washed product with titanium tetrachloride in an alkylbenzene solvent to form a treated product and a supernatant; heating of that product and supernatant; decantation of the supernatant; washing of the treated product with an aromatic hydrocarbon solvent at elevated temperature; decantation of the supernatant; washing of the treated product with an aromatic hydrocarbon solvent; and addition of an aliphatic hydrocarbon solvent to the treated product with decantation of the solvent therefrom to form the catalyst.

We claim:  
     
         1 . A process for forming a propylene polymerization catalyst which comprises: forming a combination of titanium tetrachloride, a magnesium-containing compound that can be converted to magnesium dihalide and an internal electron donor in an alkylbenzene solvent, with the proviso that, the magnesium-containing compound cannot be a magnesium dialkoxide when the internal donor is a halo phthaloyl derivative, and bringing that combination to elevated temperature to form an intermediate product; washing the intermediate product with an aromatic hydrocarbon solvent at elevated temperature to produce a washed product and a supernatant followed by decantation of the supernatant therefrom; treating the washed product with titanium tetrachloride in an alkylbenzene solvent to form a treated product and a supernatant followed by heating of the treated product and supernatant, decantation of the supernatant therefrom, and washing of the treated product with an aromatic hydrocarbon solvent at elevated temperature; to produce a washed product and a supernatant followed by decantation of the supernatant therefrom; treating the washed product with titanium tetrachloride in an alkylbenzene solvent, at least one more time, to form a treated product and a supernatant followed by heating of the treated product and supernatant, decantation of the supernatant therefrom; and addition of an aliphatic hydrocarbon solvent to the treated product with decantation of the solvent therefrom to form a washed product which can be used as a propylene polymerization catalyst.  
     
     
         2 . A process as claimed in  claim 1  wherein, after the formation of the washed product resulting from addition of the aliphatic hydrocarbon solvent, and addition of mineral oil is added to the washed product forming a slurry containing the propylene polymerization catalyst.  
     
     
         3 . A process as claimed in  claim 1  wherein the alkylbenzene solvent is toluene.  
     
     
         4 . A process as claimed in  claim 1  wherein the magnesium-containing compound that can be converted to magnesium dihalide is a magnesium chloroalkoxide that contains up to about twelve carbon atoms in its alkyl moiety.  
     
     
         5 . A process as claimed in  claim 1  wherein the internal electron donor is a phthalate ester that contains up to about twelve carbon atoms in its alkyl groups.  
     
     
         6 . A process as claimed in  claim 1  wherein the alkylbenzene solvent is toluene, the magnesium chloroalkoxide is magnesium chloroethoxide, and the phthalate ester contains up to about twelve carbon atoms in its alkyl groups.  
     
     
         7 . A process as claimed in  claim 2  wherein the alkylbenzene solvent is toluene.  
     
     
         8 . A process as claimed in  claim 4  wherein the magnesium chloroalkoxide contains up to about twelve carbon atoms in its alkyl moiety.  
     
     
         9 . A process as claimed in  claim 5  wherein the phthalate ester contains up to about twelve carbon atoms in its alkyl groups.  
     
     
         10 . A process as claimed in  claim 1  wherein the alkylbenzene solvent is toluene, the magnesium-containing compound that can be converted to magnesium dihalide is a magnesium chloroalkoxide, and the internal electron donor is a phthalate ester that contains up to about twelve carbon atoms in its alkyl groups.  
     
     
         11 . A catalyst for the polymerization of propylene which comprises a titanium compound having at least one titanium-halogen bond which is supported on an activated, amorphous magnesium dihalide support that is essentially free of alkoxy functionality, said catalyst having the following physical parameters: weight percent titanium—less than 2%; weight percent phthalate ester—from about 10% to about 25%; phthalate ester to titanium molar ratio—from about 0.9 to about 2; weight percent magnesium—from about 14% to about 23%; magnesium to titanium molar ratio—from about 7 to about 30; surface area—from about 250 m 2 /gm to about 500 m 2 /gm; pore volume—from about 0.2 cc/gm to about 0.5 cc/gm; and average pore diameter—no more than about 50 Angstroms.  
     
     
         12 . A catalyst for the polymerization of propylene which comprises a titanium compound having at least one titanium-halogen bond which is supported on an activated, amorphous magnesium dihalide support that is essentially free of alkoxy functionality, said catalyst having the following physical parameters: weight percent titanium—from about 1% to less than 2.0%; weight percent phthalate ester—from about 10% to about 20%; phthalate ester to titanium molar ratio—from about 1 to about 1.9; weight percent magnesium—from about 18% to about 21%; magnesium to titanium molar ratio—from about 14 to about 29; surface area—from about 300 m 2 /gm to about 500 m 2 /gm; pore volume—from about 0.2 cc/gm to about 0.4 cc/gm; and average pore diameter—no more than about 35 Angstroms.  
     
     
         13 . A catalyst for the polymerization of propylene which comprises a titanium compound having at least one titanium-halogen bond which is supported on an activated, amorphous magnesium dihalide support that is essentially free of alkoxy functionality, the titanium metal content in the catalyst being less than 2 wt %, based on the weight of the support, and a phthalate ester donor, the surface area of the catalyst ranging from about 250 m 2 /gm to about 500 m 2 /gm.  
     
     
         14 . A catalyst as claimed in  claim 13  wherein the magnesium dihalide support is derived from a magnesium chloroalkoxide that contains up to about twelve carbon atoms in its alkyl moiety.  
     
     
         15 . A catalyst as claimed in  claim 13  wherein the phthalate ester donor contains up to about twelve carbon atoms in its alkyl groups.