A process for reducing the loss of catalyst activity of a Ziegler-Natta catalyst, the process comprising: a) preparing a Ziegler-Natta catalyst by providing a precursor composition of the ZN catalyst comprising at least one titanium compound; contacting the at least one titanium compound in the precursor composition with at least one aluminum alkyl compound in a hydrocarbon solvent, wherein the aluminum alkyl compound converts the at least one titanium compound in the precursor composition into a modified state of the ZN catalyst; and, removing at least a portion of the aluminium alkyl compound in the hydrocarbon solvent not consumed in converting the at least one titanium compound into the modified state to produce a reduced ZN catalyst; b) optionally, drying the reduced ZN catalyst; and c) storing and/or transporting the reduced ZN catalyst for at least 20 days at a temperature of 15°C or less; wherein the reduced ZN catalyst has a fresh catalyst activity and an aged catalyst activity, wherein the fresh catalyst activity is the catalyst activity of the catalyst when the catalyst is fed to a polymerization system soon after the catalyst is manufactured and before the catalyst substantially changes, and the aged catalyst activity is the catalyst activity of the catalyst when it is fed to the polymerization system after the catalyst has been stored and/or transported; and, the aged catalyst activity is at least 75% of the fresh catalyst activity; and, wherein the contacting of the at least one titanium compound in the precursor composition with the aluminum alkyl compound includes providing a molar ratio of the aluminum alkyl compound to the titanium compound in a range from 4:1 to 10:1. a) preparing a Ziegler-Natta catalyst by providing a precursor composition of the ZN catalyst comprising at least one titanium compound; contacting the at least one titanium compound in the precursor composition with at least one aluminum alkyl compound in a hydrocarbon solvent, wherein the aluminum alkyl compound converts the at least one titanium compound in the precursor composition into a modified state of the ZN catalyst; and, removing at least a portion of the aluminium alkyl compound in the hydrocarbon solvent not consumed in converting the at least one titanium compound into the modified state to produce a reduced ZN catalyst; contacting the at least one titanium compound in the precursor composition with at least one aluminum alkyl compound in a hydrocarbon solvent, wherein the aluminum alkyl compound converts the at least one titanium compound in the precursor composition into a modified state of the ZN catalyst; and, removing at least a portion of the aluminium alkyl compound in the hydrocarbon solvent not consumed in converting the at least one titanium compound into the modified state to produce a reduced ZN catalyst; b) optionally, drying the reduced ZN catalyst; and c) storing and/or transporting the reduced ZN catalyst for at least 20 days at a temperature of 15°C or less; wherein the reduced ZN catalyst has a fresh catalyst activity and an aged catalyst activity, wherein the fresh catalyst activity is the catalyst activity of the catalyst when the catalyst is fed to a polymerization system soon after the catalyst is manufactured and before the catalyst substantially changes, and the aged catalyst activity is the catalyst activity of the catalyst when it is fed to the polymerization system after the catalyst has been stored and/or transported; and, the aged catalyst activity is at least 75% of the fresh catalyst activity; and, wherein the contacting of the at least one titanium compound in the precursor composition with the aluminum alkyl compound includes providing a molar ratio of the aluminum alkyl compound to the titanium compound in a range from 4:1 to 10:1. wherein the reduced ZN catalyst has a fresh catalyst activity and an aged catalyst activity, wherein the fresh catalyst activity is the catalyst activity of the catalyst when the catalyst is fed to a polymerization system soon after the catalyst is manufactured and before the catalyst substantially changes, and the aged catalyst activity is the catalyst activity of the catalyst when it is fed to the polymerization system after the catalyst has been stored and/or transported; and, the aged catalyst activity is at least 75% of the fresh catalyst activity; and, wherein the contacting of the at least one titanium compound in the precursor composition with the aluminum alkyl compound includes providing a molar ratio of the aluminum alkyl compound to the titanium compound in a range from 4:1 to 10:1.