Ethylene and Propylene Polymerization Using In Situ Supported Me₂Si(Ind)₂ZrCl₂ Catalyst: Experimental and Theoretical Study

Abstract

Summary: Me2Si(Ind)2ZrCl2 was in situ immobilized onto SMAO and used for ethylene and propylene polymerization in the presence of TEA or TIBA as cocatalyst. The catalytic system Me2Si(Ind)2ZrCl2/SMAO exhibited different behavior depending on the amount and nature of the alkylaluminum employed and on the monomer type. The catalyst activity was nearly 0.4 kg polymer · g cat−1 · h−1 with both cocatalysts for propylene polymerization. Similar activities were observed for ethylene polymerization in the presence of TIBA. When ethylene was polymerized using TEA at an Al/Zr molar ratio of 250, the activity was 10 times higher. Polyethylenes made by in situ supported or homogeneous catalyst systems had practically the same melting point (Tm). On the other hand, poly(propylenes) made using in situ supported catalyst systems had a slightly lower Tm than poly(propylenes) made using homogeneous catalyst systems. The nature and amount of the alkylaluminum also influenced the molar mass. The poly(propylene) molar mass was higher when TIBA was the cocatalyst. The opposite behavior was observed for the polyethylenes. Concerning the alkylaluminum concentration, the molar mass of the polymers decreased as the amount of TEA increased. In the presence of TIBA, the polyethylene's molar mass was almost the same, independent of the alkylaluminum concentration, and the poly(propylene) molar mass increased with increasing amounts of cocatalyst. The deconvolution of the GPC curves showed 2 peaks for the homogeneous system and 3 peaks for the heterogeneous in situ supported system. The only exception was observed when TEA was used at an Al/Zr molar ratio of 500, where the best fit was obtained with 2 peaks. Based on the GPC deconvolution results and on the theoretical modeling, a proposal for the active site structure was made.Molar mass distribution deconvolution of polyethylene prepared with the system Me2Si(Ind)2ZrCl2/SMAO/TIBA with 500 mol/mol of alkylaluminum as cocatalyst.magnified imageMolar mass distribution deconvolution of polyethylene prepared with the system Me2Si(Ind)2ZrCl2/SMAO/TIBA with 500 mol/mol of alkylaluminum as cocatalyst.

Innovative route for the preparation of high-performance polyolefin materials based on unique dendrimeric silica particles

“…Franceschini et al [54] observed in a previously mentioned study that the polyethylene produced through in-situ supported systems (SA-DS equivalent) presented similar melting temperatures to the polymer produced with the catalyst in homogeneous conditions, while other studies published by Lee and Park [38,51] reported polymers produced through in-situ supported systems that presented both higher and lower melting temperatures than their homogeneous analogues. In fact, there are various factors that contribute towards the final melting temperature and crystallinity of a polymer, namely the polymerization temperature, the type of system applied (catalyst, co-catalyst, scavenger, etc.).…”

Transition Metal–(μ-Cl)–Aluminum Bonding in α-Olefin and Diene Chemistry

“…The negative role of Cl − in the zirconocene-catalyzed polymerization of α-olefins when using MAO as an activator was demonstrated by Cramail et al in the framework of the simplified MAO model [ 157 ]; however, further studies have shown that not everything is so unambiguous, primarily because of the incompleteness of the early conceptions of the MAO structure. In recent years, this issue was clarified; essentially, the presence of Cl-containing MAO species as counter-ions was confirmed experimentally [ 28 , 125 , 158 , 159 ], In particular, the molecular ion with an m / z ratio of 1395 ( Figure 16 ) was detected when analyzing the activation of Cp 2 ZrCl 2 by MAO. Evidently, it is the Al–Cl fragment in this molecule that can coordinate at the Zr catalytic center.…”

Modification of Clays by Sol‐Gel Reaction and Their Use in the Ethylene In Situ Polymerization for Obtaining Nanocomposites

“…For HsT3 and HsT12, the decrease in catalyst activity is low compared to the HsT8 system: its value is roughly one half of that obtained in the case of homopolymerization reaction. This decrease effect of catalytic activity with the clay support has been widely studied [34]. It is probably due to the clay surface which should work like an extremely huge ligand, proving more difficult to render access to the monomer.…”