Studies On Chromium Based Ethylene Selective Oligomerization Catalyst System

1-Hexene and 1-octene are a-olefins and import intermediate products.Both are in great demand industrially as co-monomer for ethylene copolymerization.Studies on ethylene selective tri-/tetramerization are focused on by researchers academically and industrially.Chromium catalysts attract more attention for their high selectivity and activity.Modifying current catalyst systems and finding new catalyst systems and are effective ways.In this work,studies on mixed ligands catalyst systems for ethylene selective oligo-merization,formed by adding a second ligand containing an N,O,P,or S atom into PNP-Cr catalyst,has been carried out.Results show that addition of a second ligand may change the selectivity of 1-hexene and 1-octene in the liquid products,while affecting the activity of catalyst.Using the mixed ligand catalyst system consisting of tBu-PNP/Cr(acac)3/MAO and 1 equiv of PPh3 for ethylene oligomerization at 65 ℃,30 bar ethylene,the total selectivity of 1-hexene and 1-octene may increase from 88.5%to 91.6%,comparing to the results without a second ligand.A series of P^N^N ligands were synthesized according to the reference,and applied to ethylene selective oligomerization.Catalysts formed of PAN^N ligand and CrCl3(THF)3 were tested under optimized condition.Results shows that these catalyst were capable for ethylene selective trimerization.The highest selectivity for 1-hexene are 83.5%,with the activity of 3014 g/gcr·h when using Ph2P(C2H4)NH(C2H4)NEt2 as the ligand.IRMOF-3 was synthesized according to the reference and applied to ethylene selective oligomerization in many ways.The IRMOF-3-SI-Cr prepared from IRMOF-3 was applied to ethylene oligomerization,and 1-hexene and 1-octene were detected in liquid products.