Dependence of comonomer effect and hydrogen effect on internal donor in ethylene/1-hexene copolymerizations with MgCl2-supported catalysts

Abstract

Abstract:Ethylene homopolymerization and copolymerizations with 1-hexene by three types of MgCl 2 -supported catalysts were compared. Cat-1 contains no internal electron donor (ID), Cat-2 contains phthalic anhydride (PA) as ID, and Cat-3 contains anisole as ID. The influences of two kinds of ID on comonomer effect, the role of hydrogen, polymerization kinetics in ethylene/1-hexene copolymerization were investigated. The addition of ID improves the catalysts activities in ethylene polymerization. In comparison with ethylene homopolymerization, these ethylene/1-hexene copolymerization systems all showed strong comonomer effects. However, internal donor, especially anisole, weakens the extent of comonomer activity enhancement. When the concentration of 1-hexene is 0.6 mol/L, catalysts activities increase remarkably with adding a small amount of hydrogen. But, the addition of ID reduces the sensitivity of catalyst activity to hydrogen. The introduction of anisole increases the homo-polymerization rate rapidly at the initial stage, but makes it decay earlier. In ethylene/1-hexene copolymerization with hydrogen, the addition of phthalic anhydride as ID can stabilize the polymerization rate, but anisole accelerates the decaying trends. The results are discussed based on a kinetic mechanistic model of the ID effect on ethylene copolymerization.

Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

“…This was because the addition of internal donor decreased sensitivity of catalyst activity to external donor. This result is in good agreement with that of Zhang et al [5]. They reported that the addition of phthalic anhydride or anisole as internal donor can depress the sensitivity of catalyst activity to hydrogen in ethylene /1-hexene copolymerization.…”

“…However, Zhang et al studied effect of hydrogen in ethylene/1-hexene copolymerization in the presence of internal donor. They found that hydrogen can improve the catalyst activity in ethylene/1-hexene copolymerization when it presents in a small concentration [5]. At this point, the effect of hydrogen is still unclear, but it is interesting to investigate further.…”

“…Moreover, the molecular weight and molecular weight distribution of polyethylene were less affected by external donor addition. Furthermore, Zhang et al studied the effect of phthalic anhydride and anisole as internal donor in ethylene/1-hexene copolymerization with Ziegler-Natta catalyst [5]. The results showed that the addition of internal donor can improve the activity.…”

Effect of hydrogen on Ziegler - Natta catalysts prepared by different methods for ethylene polymerization

“…This was because the addition of internal donor decreased sensitivity of catalyst activity to hydrogen. This result is in good agreement with that of Zhang et al They reported that the addition of phthalic anhydride or anisole as internal donor can depress the sensitivity of catalyst activity to hydrogen in ethylene /1hexene copolymerization 127 . b Activity ratio without H2 = activity of the modified catalyst/activity of the unmodified catalyst c Activity ratio with H2 = activity of the catalyst at that level of H2/activity of that catalyst without H2…”

Effects of Internal Electron Donor on Distribution and Reactivity of Active Centers in Ethylene/1‐Hexene Copolymerization with MgCl2‐Supported Ziegler‐Natta Catalyst

“…[19][20][21] In the long-term research and development of supported Z-N catalysts for polyethylene production, the olefin polymerization kinetics, CCD of LLDPE, and morphology of the nascent polymer particles have been found to be effectively changed by introducing electron donors like esters, ethers, amides and alkoxysilanes in the catalysis system. [6][7][8]10,13,[22][23][24][25][26][27][28][29][30][31][32][33] Considering the importance of electron donors in supported Z-N catalysts, various research approaches have been adopted to disclose the mechanism of the electron donor effects, including spectroscopic analysis, [34][35][36][37][38][39][40] analysis on catalyst morphology, [41,42] and molecular simulation. [8,[43][44][45][46][47][48][49] Besides these approaches, mechanistic studies based on polymerization kinetics and counting of the active centers have also made important contributions to this topic.…”