新型树枝状PNP铬催化剂的合成及催化性能

摘要

A novel dendritic PNP ligand was synthesized using 1.0G dendritic polyammidoamine(PAMAM) and chlorodiphenylphosphine as the raw materials through substitution reaction,and the dendritic PNP chromium(Ⅲ) catalyst was synthesized from the reaction with chromium(Ⅲ) chloride tetrahydrofuran complex as material.The structure of novel dendritic PNP ligand and PNP chromium(Ⅲ) catalyst were characterized by Fourier transform infrared(FTIR),ultraviolet-visible(UV-Vis),nuclear magnetic resonance(NMR),electrospray ionization-mass spectroscopy(ESI-MS) and elemental analysis.The results indicate that the structure of novel dendritic PNP ligand and PNP chromium(Ⅲ) catalyst are consistent with theoretical structure.The dendritic PNP chromium(Ⅲ) catalyst was used as a precatalyst in the oligomerization of ethylene with the co-catalyst methylaluminoxane(MAO).The effects of solvent,reaction temperature,reaction pressure and the molar ratio of Al/Cr on the catalytic activities and selectivity in the oligomerization were investigated.With MAO as co-catalyst and toluene as solvent,the selectivity of novel dendritic PNP chromium(Ⅲ) catalyst on ethylene trimer and tetramer reached up to 36.76% and the catalytic activity was 2.15×105 g/(mol Cr·h) at reaction temperature of 25 ℃,reaction pressure of 0.9 MPa and Al/Cr molar ratio of 500.%以1.0代聚酰胺-胺(PAMAM)为配体骨架,氯代二苯基膦为原料,通过取代反应合成了1种含有较大空间位阻的新型树枝状PNP配体,再以CrCl3(THF)3为络合试剂,通过络合反应合成树枝状PNP铬催化剂.采用傅里叶变换红外光谱(FTIR)、紫外-可见分光光度计(UV-Vis)、核磁共振波谱(NMR)、电喷雾电离质谱(ESI-MS)和元素分析等手段证实合成的新型树枝状PNP配体及其铬催化剂的结构与理论设计的结构一致.以甲基铝氧烷(MAO)为助催化剂,对乙烯齐聚反应进行了研究,考察了溶剂种类、反应温度、反应压力及Al/Cr摩尔比对该催化剂活性和选择性的影响.结果表明,以甲苯为溶剂,MAO为助催化剂,当反应温度为25 ℃,反应压力为0.9 MPa,Al/Cr摩尔比为500时,该催化剂的活性高达2.15×105 g/(mol Cr·h),催化剂对乙烯三聚、四聚反应的选择性共达到36.76%.