Active center determinations on MgCl₂‐supported fourth‐ and fifth‐generation Ziegler–Natta catalysts for propylene polymerization

Abstract

Active center determinations on different Ziegler–Natta polypropylene catalysts, comprising MgCl2, TiCl4, and either a diether or a phthalate ester as internal donor, have been carried out by quenching propylene polymerization with tritiated ethanol, followed by radiochemical analysis of the resulting polymers. The purpose of this study was to determine the factors contributing to the high activities of the catalyst system MgCl2/TiCl4/diether—AlEt3. Active center contents (C*) in the range 2–8% (of total Ti present) were measured and a strong correlation between catalyst activity and active center content was found, indicating that the high activity of the diether‐containing catalysts is due to an increased proportion of active centers rather than to a difference in propagation rate coefficients. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1635–1647, 2006

Chemical structure–stereospecificity relationship of internal donor in heterogeneous Ziegler–Natta catalyst for propylene polymerization by DFT and MM calculations

“…This implies that the insertion of propylene into the active site 1 should overcome higher energy barrier (10.0 kcal/mol) as compared with the insertion into the active site 2 (5.8 kcal/mol). This result leads us to assume that the polymerization kinetics of propylene at the isospecific active site 2 created on the (1 0 0) surface is much faster than that at the aspecific active site 1, which has been supported by recent experimental studies [13][14][15], where the propagation rate constant at an isospecific active site is several times lager than that at an aspecific active site. It is also noteworthy that the calculated activation energies of 10.0 and 5.8 kcal/mol are in a good agreement with an experimental value (6.8 $ 9.1 kcal/mol) [45].…”

“…However, the mechanism underlying the role of donor has not been completely understood, although many experimental [5][6][7][8][9][10][11][12][13][14][15][16][17] and theoretical [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] studies have been reported. A thorough understanding of the relationship between the chemical structure of donor and the isotacticity (and productivity) of polypropylene are essential for molecular design of better donor to yield highly isotactic polypropylene with high productivity.…”

Investigation of Planar Ziegler-Natta Model Catalysts Using Attenuated Total Reflection Infrared Spectroscopy

“…A 0.1 M ratio donor/MgCl 2 was applied, comparable to that present in a typical Ziegler-Natta catalyst [34]. It is well established that the coordination of donors such as esters onto MgCl 2 supports (ethyl benzoate/MgCl 2 complexes have been extensively studied) occurs via the carbonyl group [17-20, 24, 26, 28-31].…”

Role of Electron Donor in Polymer Catalyst Synthesis: An XPS Study

“…Evaluated Ti/Mg ratio with other parameters given in Table 1 has been used to estimate productivity of the catalyst [9]. Evaluated Ti/Mg ratio was 0.054, a value typical for Ziegler-Natta catalyst used for propylene polymerization [19].…”