Synthesis of Branched Polyethylene from Ethylene by Tandem Action of Iron and Zirconium Single Site Catalysts

Abstract

The synthesis of low-density polyethylene from ethylene as the only monomer feed has been investigated as an alternative route to branched polyethylene and to obtain new materials with different properties, avoiding the need to feed 1-alkenes into the polymerization process. The details of the evaluation of two combination catalyst systems based on single site catalysts are discussed. The {[(2-ArNdC(Me)) 2C5H3N]FeCl2} (Ar ) 2-C6H4(Et)) compound, designated as catalyst 1, oligomerizes ethylene to produce linear R-olefins with high selectivity, and Me2SiInd2ZrCl2 (2) or EtInd2ZrCl2 (3) are used as catalysts that incorporate the R-olefins in the polymer. For catalyst 1 in the presence of methylaluminoxane (MAO) and ethylene, a wide range of R-olefin products were found, both soluble and insoluble. Also, tandem catalyst combinations 1 and 2 or 1 and 3 in the presence of ethylene alone can readily produce branched polyethylene with levels of 1-4 branches per 100 units of ethylene. A change in activity was found for variations in the Fe/Zr ratio for both systems, with lower activity but higher frequency of branching in the polymer backbone for catalyst 2. The final product obtained by the 1/3/MAO systems, however, shows a more homogeneous structure as determined by DSC and GPC.

FI Catalyst for Polymerization of Olefin

“…Accordingly and following the great success of the metallocene catalysts, significant efforts have been directed toward the discovery and application of new, highly active, single-site catalysts (post-metallocene catalysts) [10,11]. These research efforts have led to the introduction of quite a few high-activity single-site catalysts based on both early and late transition metal complexes with various ligand environments [12][13][14][15][16][17][18]. In association with appropriate cocatalysts, many of these catalysts show ethylene polymerization activities that are superior or comparable to those seen with early group 4 transition metals metallocene catalysts.…”

“…In association with appropriate cocatalysts, many of these catalysts show ethylene polymerization activities that are superior or comparable to those seen with early group 4 transition metals metallocene catalysts. These post-metallocene catalysts can produce a wide array of distinctive polymers (e.g., hyper-branched PEs, ethylene-methyl acrylate copolymers, monodisperse poly(1-hexene)s, and block copolymers based onolefins), many of which were inaccessible using metallocene catalysts [3,[16][17][18][19][20][21][22][23][24].…”

Tandem catalytic system: Rac‐Et(ind)2ZrCl2/AlEt2Cl/MAO toward the synthesis of branched polyethylene

“…After that, a wide variety of promising tandem catalytic systems have been developed to prepare LLDPE in situ involving two different Ziegler-Natta catalysts, Ziegler-Natta catalyst/ homogeneous catalyst, two or three different homogeneous catalysts. [3][4][5][6][7][8][9][10] Surveying these works, [11][12][13][14][15][16] it is found that tandem catalysis is consisted of two kinds of catalysts and one activator, in which one catalyst oligomerizes the ethylene to a-olefins, and the other is responsible for polymerizing the ethylene and incorporating the a-olefins into the growing polymer chain under the same activator. In other words, the essential of tandem catalysis exists a dual functional catalyst active species: oligomerization/copolymerization active species in the same reaction system.…”

Turning a Cr-based heterogeneous ethylene polymerisation catalyst into a selective ethylene trimerisation catalyst

“…Currently, they are industrially obtained using a two-step process: production of 1-hexene by ethylene oligomerisation and subsequent use of 1-hexene in the production of LLDPE. A single-step process involves either the use of a bi-functional catalyst active in both processes or the use of a tandem catalytic system [5][6][7][8]. So far, no homogeneous catalysts are reported to be simultaneously active in both processes and, therefore, more attention is paid to heterogeneous systems, which present the advantage that different active sites can be created on a support surface.…”