Kinetic Study of Chain Transfer Reactions upon 1-Hexene Polymerization on Highly Active Supported Titanium–Magnesium Catalysts

Hydrogen effect on the molecular weight distribution of polymers obtained by polymerization of ethylene and α‐olefins over supported titanium‐magnesium catalysts

“…At the same time, there are very few comparative data on the molecular weight and polydispersity of polymers obtained by polymerization in the absence and presence of hydrogen. Recently 33 we have found that addition of hydrogen at polymerization of 1‐hexene over TMC with tri‐ethyl‐aluminum (TEA) as cocatalyst leads to the narrowing of molecular weight distribution (decrease of Mw/Mn value) of polymer produced. We believe it is necessary to test and analyze this phenomenon for broader row of monomers and for copolymerization of ethylene with α‐olefins.…”

“…6,7,[18][19][20][21][22][23][24][25] According to, 24,25 this result is associated with reversible deactivation of some active sites upon the hydrogen introduction into the reaction medium. There are many publications [1][2][3][4][5][6][7]24,[26][27][28][29][30][31][32][33] devoted to the effect of the hydrogen content on the molecular weight of polymers obtained over titaniummagnesium catalysts of various compositions during the ethylene, propylene and 1-hexene polymerization. These data are usually used to determine the ratio of the constant of the chain transfer reaction with hydrogen (k tr H ) to the propagation rate constant (k P ).…”

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts

“…At the same time, in our works [19,[23][24][25][27][28][29][30]33] it was found that in some cases, when using a catalyst of the same composition, the introduction of polymer chain transfer agents into the reaction medium also leads to a change in the polydispersity of the obtained polyolefins. We believe these results are related to the additional heterogeneity of the active sites of supported Ziegler-Natta catalysts in polymer chain transfer reactions, as the composition of the reaction medium changes during polymerization.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13][14]. Varying the composition of supported Ziegler-Natta catalysts makes it possible to control the heterogeneity of the active centers of these catalysts in the reactions of polymer chain growth and transfer and to obtain polyolefins with different polydispersity [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

“…It is necessary to note the results presented in [19,[23][24][25][28][29][30]33] were obtained at different times (2009-2023) for various polyolefins (polyethylene, polypropylene, polyhexene, and ethylene-α-olefin copolymers) using supported catalysts Ziegler-Natta of various compositions. The generalization of these results, in the form of a short review, makes it possible to more reasonably formulate a new approach to control the polydispersity of polyolefins obtained over these catalysts by varying the composition of the reaction medium (polymerization conditions).…”