Ethylene Polymerization using Combined Ni and Ti Catalysts Supported in situ on MAO‐Modified Silica

Abstract

Summary: Branched polyethylene/linear polyethylene blends (BPE/LPE) were prepared using the combined Ni(α‐diimine)Cl2 (1) (α‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) catalysts supported in situ on methylaluminoxane (MAO)‐modified silica (4.0 wt.‐% Al/SiO2). The polymerization reactions were performed in toluene at two different polymerization temperatures (0 and 30 °C) and several nickel molar fractions (xNi), using MAO as external cocatalyst. At all temperatures, the activities show an approximate linear correlation with xNi, indicating a non‐synergistic effect between the nickel and the titanium species. Higher activities were found at 0 °C. The melting temperatures for the polyethylene blends produced at 0 °C decrease as xNi increases in the medium, indicating good compatibility between the polyethylene phases made by both catalysts. The melting temperature (Tm) of the polyethylene blends was shown to depend on the order in which the catalysts were immobilized on the MAO‐modified silica support. The initial immobilization of 1 on the support (2/1/SMAO‐4) affords polymers with a lower Tm than those produced with 1/2/SMAO‐4. In addition, scanning electron microscopy (SEM) studies revealed that the spherical morphology of the supported catalyst is replicated in the polyethylene particles.Influence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying xNi.magnified imageInfluence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying xNi.

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

“…These catalysts are well known for production of respectively branched and linear polyethylene chains depending on the applied reaction conditions [34][35][36][37]. Both catalysts were supported on the TIBA-modified MgCl 2-nEtOH adduct, separately and concurrently, at different ratios.…”

“…Production of linear/ branched polyethylene blends in reactor eliminates the post-polymerization melt-mixing step and consequent degradation, thus can minimize the phase segregation problems, which is important from the economical point of view. Application of mixed as well as SiO 2 -supported hybrid LTM/metallocene catalysts for production of linear/branched polyethylene blends has been reported in the literature [34,35]. Others have reported synergistic effect of immobilization of LTM and metallocene catalysts on MgCl 2 adduct [36] supports and MCM nanoparticles [37].…”

“…Likewise, Ahmadjo et al [33] have provided polyethylene with multimodal melting peaks using hybrid bis(imino)pyridine Fe/Ziegler-Natta catalysts. Many groups have utilized a-diimine nickel complexes in homogeneous or heterogeneous states in combination with Ziegler-Natta or metallocene catalysts in order to synthesize linear/branched polyethylene blend in one reactor [34][35][36][37]. Such blends are mainly produced by post-polymerization melt-mixing process.…”

Polymethylaluminoxane organic frameworks (sMAOF) – highly active supports for slurry phase ethylene polymerisation

“…4 Polymer morphology is known to be influenced by the catalyst support, which acts as a template for the growing polymer chain in heterogeneous polymerisation. [114][115][116][117][118] Scanning electron microscopy (SEM) images of polyethylene samples for [M] 0 /[Al sMAO ] 0 = 0, 0.01 and 0.025 (Fig. 5a-c, respectively) show retention and replication of the 'popcorn' morphology of the original supports during catalyst immobilisation and polymerisation.…”

Catalysis of ethylene to linear low‐density polyethylene with iron‐based diimine complex immobilized on calcosilicate and silica‐supported rac‐Et(Ind)2ZrCl2

“…Benefits from this method are obvious due to the employment of a single feedstock—ethylene and two catalysts in one reactor. Following the aforementioned original work, several attempts adopting different combinations of ethylene oligomerization and copolymerization catalysts had been performed 3–9. However, such catalytic systems had problems like interferences between the oligomerization catalyst and copolymerization catalyst, the catalysts and activators, and moreover, inferior control over the distribution of α‐olefins and branching degree of the LLDPE obtained.…”