Research of 1-Octene C═C Bond Isomerization in High-temperature Solution Copolymerization of Ethylene/1-Octene

Abstract

1-Octene has a very high industrial value as one of the linear α-olefins, but the industrial value is severely reduced when its double bond isomerizes to form endo-octene. Thus, in this paper, the effect of reaction temperature, reaction time, type, and concentration of aluminum compounds on the double-bond isomerization reaction of 1-octene and the inhibition of the isomerization by the inhibitor, have been investigated. The mechanism of 1-octene isomerization is studied by combining gas chromatography-mass spectrometry (GC-MS) and density functional theory (DFT) calculations. Modified methylaluminoxanes (MMAO-3A), triethylaluminum (TEA), or triisobutylaluminum (TIBA) could significantly promote 1-octene to undergo double-bond isomerization reactions and the degree of isomerization of 1-octene increased with increasing concentrations of aluminum compounds. In addition, inhibitors such as isooctanol or isooctylamine, can disrupt the structure of the reactive aluminum species and may retard the double bond isomerization reaction of 1-octene. Therefore, reducing the concentration of aluminum compounds in the ethylene/1-octene high-temperature solution copolymerization system and the timely and sufficient use of an inhibitor at the end of the reaction are both effective in eliminating the 1-octene double bond isomerization.