Ziegler-Natta catalyst system having a thermally treated magnesium chloride component

A process for making a procatalyst, the process comprising:

• thermally treating a magnesium chloride slurry at a treatment temperature of at least 100° C. and for at least 30 minutes, the magnesium chloride slurry comprising at least magnesium chloride (MgCl2) dispersed in a solvent;
• and
• combining a chlorinating agent and a titanium species with the magnesium chloride slurry, the chlorinating agent having a structure A(Cl)x(R1)3-x, where:
• A is aluminum or boron;
• R1 is (C1-C30)hydrocarbyl;
• and
• x is 1, 2, or 3;
• wherein:
• a molar ratio of the chlorinating agent to the thermally treated MgCl2 component in the heterogeneous procatalyst is from 3:40 to 14:40;
• and
• a molar ratio of the titanium species to the thermally treated MgCl2 component in the heterogeneous procatalyst is from 0.5:40 to 5:40.

A process for making a procatalyst, the process comprising:

• thermally treating a magnesium chloride slurry at a treatment temperature of at least 100° C. and for at least 30 minutes, the magnesium chloride slurry comprising at least magnesium chloride (MgCl2) dispersed in a solvent;
• and
• combining a chlorinating agent and a titanium species with the magnesium chloride slurry, the chlorinating agent having a structure A(Cl)x(R1)3-x, where:
• A is aluminum or boron;
• R1 is (C1-C30)hydrocarbyl;
• and
• x is 1, 2, or 3;
• wherein thermally treating the magnesium chloride slurry occurs before combining the chlorinating agent and the titanium species with the magnesium chloride slurry.