Preparation Of 1-Octene By Ethylene Tetramerization With High Selectivity

1-Octene is widely used as a co-monomer for polyethylene, an intermediate for plasticizerand fatty acid. The ethylene copolymer with 1-octene as a co-monomer has better mechanicalproperties, optical properties, tear and impact resistance than those with 1-butene or 1-hexene asa co-monomer. There is no commercially successful process for tetramerizing ethylene to1-octene specially. Usually, 1-octene is prepared as a by-product by ethylene oligomerization orextraction process in industry, which has some disadvantages such as low selectivity and lowoutput, and all of this restrict it from been widely used. So the development of the catalyst andtechniques of synthesis 1-octene by ethylene tetramerization with patented right seems especiallyimportant and urgent.Starting with analyzing of the mechanism of oligomerization reaction, this thesis hasdesigned and synthesized two series that contain ten ligands. We confirmed the object catalyst bystudying the catalyst system that composed by ligand, chromium compound, cocatalyst andaccelerant. We have also selected the best conditions by researching the effects of ligandstructure, cocatalyst type, reaction temperature, reaction pressure, molar ratio of Al and Cr,concentration of main catalyst and reaction time on oligomerization reaction.The results show that: adding electron donor accelerant to the catalyst system of ethyleneoligomerization, can improve the selectivity toward 1-octene efficiently. The catalytic activitycan reached 1.85×107 g/(mol Cr?h);the selectivity of 1-octene reached 74.74%;the selectivity of1-hexene is 11.31%, while 1-butene is 0.41%;oligomerization products with 10 or more than 10carbon is 5.18% with chromium acetylacetonate as main catalyst,N-cyclopenty-diphoshinoamine as ligand, MAO as cocatalyst, tetrachloroethane as accelerantand the proportion is 1︰2︰300︰1, pre-mix time is 3 min, concentration of Cr is 3 ppm,reaction temperature is 50℃ , reaction pressure is 5.0MPa, reaction time is 30 min, speed ofmechanical stir is 550 rpm.