Supported Ziegler–Natta catalysts for propylene polymerization. Study of surface species formed at interaction of electron donors and TiCl4 with activated MgCl2

The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

“…[8] This is because their model is based on a careful understanding of the conclusions of experimental and computational investigations. The conclusions are as follows: (1) the MgCl 2 support consists of a few layers of MgCl 2 sandwiches, [29] and the surface primarily consists of (104) and (110) lateral cuts, (2) the (104) lateral cuts are significantly greater in number than the (110) cuts, [30] and (3) the TiCl 4 molecules prefer the more-acidic, four-coordinated magnesium atoms on the (110) lateral cuts over the less-acidic five-coordinated magnesium atoms on the (104) lateral cuts. [31] These experimental and computational findings have recently led Cavallo and co-workers [8] to propose an interesting new model for the MgCl 2 support that convincingly accounts for the seemingly contradictory findings listed from (1) to (3) above.…”

Propylene Polymerization over MgCl2‐Supported Ziegler–Natta Catalysts Containing Tri‐Ether as the Internal Donor

“…4,16,[18][19][20] Additionally, the internal donor could prevent the formation of aspecific sites or transforms aspecific sites into highly stereoselective sites. 17,21 It is believed that the internal donor blocks particular sites on the MgCl 2 surface which otherwise, upon coordination with TiCl 4 , would generate precursors of nonstereospecific active sites. 6,21,22 The role of the internal donor in the Ziegler-Natta catalyst system is very crucial in terms of activity, isotacticity, 23 hydrogen response, and molecular weight distribution (MWD).…”

“…17,21 It is believed that the internal donor blocks particular sites on the MgCl 2 surface which otherwise, upon coordination with TiCl 4 , would generate precursors of nonstereospecific active sites. 6,21,22 The role of the internal donor in the Ziegler-Natta catalyst system is very crucial in terms of activity, isotacticity, 23 hydrogen response, and molecular weight distribution (MWD). 19 External donors play a major role in controlling polypropylene catalyst activity, stereospecificity, MWD, and hydrogen response.…”

Effect of internal electron donor on the active center distribution in MgCl2-supported Ziegler–Natta catalyst

“…Meanwhile, ID plays a vital role in controlling the catalyst stereoselectivity, leading to evident improvement in isotacticity of polyolefins [5]. Several molecular models have been proposed to explain the stereoregulating capability of the ID [6][7][8][9]. Considerable efforts have been devoted to finding better IDs that can improve both activity and stereoselectivity of the catalysts [10,11].…”