The second life of Ziegler catalyst. Ethylene polymerization reactions with TiCl₄–Al[C₂H₅]₂Cl/Mg(C₄H₉)₂ catalyst

Abstract

The Ziegler catalyst, a combination of TiCl4 and Al(C2H5)2Cl, was widely used since 1950s for the commercial manufacture of linear polyethylene. We found that addition of Mg(C4H9)2 to this catalyst at [Al]:[Mg]molar > 2 leads to the formation of a very active catalyst system for homopolymerization of ethylene and for copolymerization of ethylene and 1‐alkenes. The principal advantages of the ternary TiCl4–Al(C2H5)2Cl/Mg(C4H9)2 catalyst are very high activity (six to seven times higher than the activity of the original Ziegler catalyst), low cost, and the ease of use: the catalyst is prepared in situ from three commercially available cheap compounds soluble in aliphatic and aromatic hydrocarbons. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47340.

Synthesis of atactic polypropylene: Propylene polymerization reactions with TiCl4–Al(C2H5)2Cl/Mg(C4H9)2 catalyst

“…TiCl 4 , which is added to the Al(C 2 H 5 ) 2 Cl/Mg(C 4 H 9 ) 2 cocatalyst at the last step of catalyst preparation, reacts both with unreacted excess of Al(C 2 H 5 ) 2 Cl and with Al(C 2 H 5 ) 2 (C 4 H 9 ) formed in . As discussed in detail earlier, reactions between TiCl 4 and organoaluminum compounds, both AlR 3 and AlR 2 Cl, generate complex mixtures of hydrocarbon‐soluble and insoluble products containing complexes of Ti IV , Ti III , and Al compounds, such as Cl 3 TiR∙AlR 2 Cl, Cl 3 TiR∙AlRCl 2 , Cl 2 TiR 2 ∙AlR 2 Cl, and Cl 2 TiR 2 ∙AlRCl 2…”

“…It is currently generally accepted that the most probable structures of active centers in all Ti‐based Ziegler‐Natta catalysts include cationic species containing the catalytically active Ti + –C bond . Two reasons for high activity of the ternary TiCl 4 –Al(C 2 H 5 ) 2 Cl/Mg(C 4 H 9 ) 2 system in propylene polymerization reactions can be proposed by analogy with alkene polymerization reactions with various premetallocene and postmetallocene catalysts . First, the products of reactions between TiCl 4 and either AlR 3 and AlR 2 Cl (i.e., various Ti IV and Ti III complexes 423,24 ) are adsorbed on the Lewis‐acidic MgCl 2 surface [] and form cationic species containing the Ti + –C bond: …”

“…Earlier we discovered that combinations of Al(C 2 H 5 ) 2 Cl and organomagnesium compounds MgR 2 , when they are used at an [Al]/[Mg] molar ratio above 2, are universal cocatalysts for all types of transition‐metal polymerization catalysts, including common heterogeneous Ziegler‐Natta catalysts, Ti(OR) 4 compounds, metallocene complexes, and various post‐metallocene complexes . In particular, the Ziegler catalyst modified with Mg(C 4 H 9 ) 2 is a highly efficient catalyst for polymerization of ethylene and for ethylene/1‐alkene copolymerization reactions …”

Alkene polymerization reactions with catalysts based on acetylacetonate complexes of vanadium and titanium: effect of cocatalyst

“…Earlier, we showed that binary combinations of two organometallic compounds, AlR 2 Cl (R = C 2 H 5 or i‐C 4 H 9 ) and MgR′ 2 (R′ = n ‐C 4 H 9 and i‐C 4 H 9 ), when used at an [Al]:[Mg] molar ratio of >2, are universal activators for various types of transition metal polymerization catalysts, including TiCl 4 , 18,19 common Ti 3+ ‐ and Ti 4+ ‐based heterogeneous and supported catalysts, 20 Ti(OR) 4 , 21,22 metallocene complexes 23 and numerous post‐metallocene catalysts 20,23–28 …”

Ethylene polymerization and copolymerization reactions with Ti(OR)4 – Al2(C2H5)3Cl3/Mg(C4H9)2 catalyst

“…We found earlier that combinations of chloro‐organoaluminium compounds AlR 2 Cl and organomagnesium compounds MgR′ 2 , when used at an [Al]:[Mg] molar ratio above 2, are universal cocatalysts for converting various types of transition metal compounds into alkene polymerization catalysts, including TiCl 4 , 9,10 common heterogeneous and supported Ti‐based catalysts, 11 metallocene complexes 12 and many post‐metallocene complexes 11–17 …”