Oligomerization of Ethylene to Produce Linear α-Olefins Using Heterogeneous Catalyst Prepared by Immobilization of α-Diiminenickel(II) Complex into Fluorotetrasilicic

CATEGORY: OLIGOMERIZATION
Catalysts 2013, 3, 125-136; doi:10.3390/catal3010125
Oligomerization of Ethylene to Produce Linear α-Olefins Using Heterogeneous Catalyst Prepared by Immobilization of α-Diiminenickel(II) Complex into Fluorotetrasilicic
Mica Interlayer
Hideki Kurokawa 1,*, Kazuki Miura 1, Kazuhiro Yamamoto 2, Tsutomu Sakuragi 2, Takao Sugiyama 1, Masa-aki Ohshima 1 and Hiroshi Miura 1
1 Graduate School of Science & Engineering, Saitama University, 255, Shimo-okubo, Sakura-ku, Saitama-shi, Saitama, 338-8570, Japan
s07ta056@mail.saitama-u.ac.jp
sugiyama@apc.saitama-u.ac.jp
oshi@apc.saitama-u.ac.jp
hmiura@mail.saitama-u.ac.jp
2 Japan Polychem Corporation, 1 Toho-cho, Yokkaichi-shi, Mie, 510-0848, Japan;
yamamoto.kazuhiro@mp.japanpe.co.jp
sakuragi.tsutomu@mb.pochem.co.jp
Abstract:
Heterogeneous catalysts for production of linear α-olefins from ethylene were prepared by the direct reaction of the α-diimine ligand [L: R-N=C(R')-C(R')=N-R; R' = Me and R = 2,6-Me2Ph (L5), 2,5-Me2Ph (L1), 2-MePh (L2), or Ph (L3); R' = 1,8-naphth-diyl and R = Ph (L4)] and Ni2+ ion-exchanged fluorotetrasilicic mica. Only high molecular weight polyethylene was obtained in the reaction using the L5/Ni2+-Mica procatalyst activated by AlEt3 (TEA) as an activator, whereas the TEA-activated L1- and L2/Ni2+-Mica procatalysts afforded a mixture of a large amount of low-molecular weight polyethylene and a small amount of oligomers having 4-22 carbons. The procatalyst consisting of Ni2+-Mica and the L3 ligand that possesses non-substituted phenyl groups on the iminonitrogen atoms effectively promoted the oligomerization of ethylene after its activation with TEA, resulting in the fact that the ethylene oligomers were produced with a moderate catalytic activity (101 g-ethylene g-cat−1 h−1 at 0.7 MPa-ethylene) in the presence of TEA. When the backbone was varied from the butane moiety (L3) to acenaphthene (L4), the solid product dramatically increased. The weight percentage of the oligomers in the total products increased with the increasing reaction temperature; however, an insignificant increase in the oligomers was observed when the ethylene pressure was decreased.
Introduction
α-Olefins (terminal alkenes) of carbon number 4–20 are important basic products in the chemical industry, and these are used as the comonomer in the ethylene/α-olefin copolymerization, the raw material of long-chain alcohols, and the base material of synthetic lubricant oil. Straight chain olefins produced by the oligomerization of ethylene are more useful than branched olefins, because of the high biodegradability of the products. The one-step process using a triethylaluminum catalyst was developed by the Gulf Oil Chemical Co. (Chevron Corp.) to produce ethylene oligomers having the Shultz-Flory distribution [1]. The two-step process using the same catalyst is known as the Ethyl process (Albemarle Corp.) and the products have a Poison distribution with a relatively narrow distribution [1]. These processes required both a high reaction temperature and ethylene pressure due to the low catalytic activity of triethylaluminum [1].
Recently, researchers developed new heterogeneous catalysts, which were prepared through the intercalation of the ligand into the late transition-metal ion exchanged clay mineral, and the coordination of the bis(imono)pyridine or α-diimine ligand to the interlayer metal ion; these catalysts showed a high activity for the polymerization of ethylene in the presence of not only MAO, but also alkyl aluminum compounds. Moreover, the steric and/or electronic properties of these heterogeneous catalysts can be changed by modification of the ligand structures, which are used in the homogeneous catalysts. As an example of the ligand modification, an iron complex bearing the acetyliminopyridine ligand instead of the bis(imino)pyridine ligand, which was immobilized into the mica interlayer, effectively produced linear α-olefins with a high activity. Researchers attempted to develop heterogeneous ethylene oligomerization catalysts to produce α-olefins by decreasing the steric bulk around the nickel center in α-diiminenickel(II) complex immobilized in a fluorotetrasilicic mica interlayer. Helldörfer et al. reported that the α-diiminenickel(II) complex, having a less hindered ligand, acts as a catalyst for ethylene oligomerization when the complex was combined with MAO.
Free Full Text Source: http://www.mdpi.com/2073-4344/3/1/125/pdf