Ethylene Tetramerization:  A New Route to Produce 1-Octene in Exceptionally High Selectivities

Abstract

Linear alpha-olefins, such as 1-hexene and 1-octene, are important comonomers in the production of linear low-density polyethylene (LLDPE). The conventional method of producing 1-hexene and 1-octene is by oligomerization of ethylene, which yields a wide spectrum of linear alpha-olefins (LAOs). While there exists several processes for producing 1-hexene via ethylene trimerization, a similar route for the selective production of 1-octene has so far been elusive. We now, for the first time, report an unprecedented ethylene tetramerization reaction that produces 1-octene in selectivities exceeding 70%, using an aluminoxane-activated chromium/((R2)2P)2NR1 catalyst system.

Selective Ethylene Oligomerization with Chromium Complexes Bearing Pyridine–Phosphine Ligands: Influence of Ligand Structure on Catalytic Behavior

“…9,19 Encouraged by this finding, introduction of a carbon linkage between the pyridine and the aminophosphine fragments was endeavored for 1−3, affording the analogous ligands 4−6 (Scheme 4). These ligands were then reacted with CrCl 3 (THF) 3 to afford corresponding chromium complexes.…”

“…90% 1-hexene) into tetramerization (up to 70% 1-octene). 8,9 Although it is not clear whether the switch in the C 6 /C 8 product ratio is mediated by ligand sterics, coordination of the pendant methoxy group to chromium, or both, 8,24,34,35 this finding demonstrates that even subtle ligand modifications can significantly influence the catalytic behavior.…”

Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr(III)/MAO catalyst

“…Toluene was refluxed and distilled from sodium/benzophenone under dry nitrogen. The ligand 1 was prepared according to a published procedure [9]. Cis,cis-1,3,5-cyclohexanetricarboxylic acid, diphenylphosphoryl azide(DPPA) and Cr(acac) 3 were purchased from Sigma-Aldrich(Pennsylvania, USA) and used as received.…”

“…Chromium catalysts play an important role in both of these processes [1][2][3][4][5][6][7][8]. Since the first report of ethylene tetramerization to form 1-octene using Cr-bis(diphenylphosphino)amine (PNP) catalysts [9], numerous studies have investigated the relationship between ligand structure and catalytic properties. We were attracted by the potential for using chromium as an ethylene tetramerization active center because of its high catalytic activity and high selectivity to 1-octene.…”

“…Chromium catalysts play an important role in both of these processes [1][2][3][4][5][6][7][8]. Since the first report of ethylene tetramerization to form 1-octene using Cr-bis(diphenylphosphino)amine (PNP) catalysts [9], numerous studies have investigated the relationship between ligand structure and catalytic properties. These include investigations into various single-site PNP ligands, wherein alkyl [10][11][12], cycloalkyl [13], ether [14], thioether, pyridyl tethers [15] and aryl [16,17] substituents attached to the N or P atom of the ligand backbone were synthesized and evaluated.…”