PN(CH2)nP配体/Cr(III)/DMAO/AlEt3催化乙烯齐聚

合成并表征了N-(2-(二苯基膦酰)乙基)-N-甲基-1,1-二苯基膦胺(L1)、N-(2-(二苯基膦酰)乙基)-N-异丙基-1,1-二苯基膦胺(L2)和N-(3-(二苯基膦酰)丙基)-N-异丙基-1,1-二苯基膦胺(L3)3种新型PN(CH₂)_nP型配体。3种配体分别与CrCl₃(THF)₃、脱除挥发性组分的甲基铝氧烷(Dried methylaluminoxane，DMAO)和三乙基铝(Aluminumtriethyl，AlEt₃)组成催化体系，考察其催化乙烯齐聚的性能。结果表明：该类配体组成的催化体系，具有催化活性高和C₆～C₈线性α烯烃选择性高的特点;L2组成的催化体系，在4.0 MPa和100 ℃时，催化活性可达1.71×10.7 g/(mol Cr·h)；在1.0 MPa和100 ℃时，1-己烯和1-辛烯总选择性达到93%。与配体L1相比，配体L2骨架N上的异丙基增加了催化剂空间体积，显著提高了催化活性及催化体系的热稳定性。

Ethylene Oligomerization Catalyzed by PN(CH2)nP/Cr(III)/DMAO/AlEt3

Three PN(CH₂)_nP ligands, N-(2-(diphenylphosphanyl)ethyl)-N-methyl-1,1 diphenylp-hosphineamine(L1),N-(2-(diphenylphosphanyl)ethyl)-N-isopropyl-1,1- diphenylphosphineamine(L2),N-(3-(diphenylphosphanyl)propyl)-N-isopropyl-1,1- diphenylphosphineamine(L3) were synthesized, and were employed as catalysts for ethylene oligomerization. The catalytic system was composed of ligand, CrCl₃(THF)₃, methylaluminoxane removing volatile components (dried methylaluminoxane, DMAO), and aluminumtriethyl (AlEt₃) and their catalytic performance was investigated for ethylene oligomerization. In the catalyst screening, the catalyst systems based on L1－L3 exhibit high catalytic activity and selectivity toward C₆－C₈ linearα-olefins, in particular, the catalyst based on L2 ligand displays the excellent catalytic activity of 1.71×10.7 g/(mol Cr·h) at 4.0 MPa and 100 ℃. For the same catalyst system, the total selectivity toward 1-hexene and 1-octene reaches to 93% at 1.0 MPa and at 100 ℃. Besides the activity, the thermal stability of the catalyst system has been also enhanced by increasing the steric bulk of the substituent groups upon N moiety from methyl (in L1) to isopropyl (in L2).