PX型配体/Cr(Ⅲ)/MAO体系催化乙烯齐聚/聚合

Ethylene oligomerization/polymerization catalyzed by PX ligands/Cr(Ⅲ)/MAO

合成了2-(二苯基膦基)乙基甲基硫醚(L1)、2-(二苯基膦基)乙基甲基醚(L2)、2-(二苯基膦基)-N,N-二甲基乙胺(L3)三种PX型配体,将配体与CrCl_3(THF)3络合,以甲基铝氧烷(MAO)为助催化剂组成PX/Cr(Ⅲ)/MAO催化体系,利用~1HNMR,^(13)C NMR,^(31)P NMR,GC,GPC等方法对配体结构和聚合产物进行了表征,研究了催化体系催化乙烯齐聚的性能。实验结果表明,PX/Cr(Ⅲ)/MAO体系的催化活性随反应温度的升高均呈先升高后降低的趋势,随反应压力的升高而逐渐升高。L1/Cr(Ⅲ)/MAO体系的催化活性低于L2/Cr(Ⅲ)/MAO和L3/Cr(Ⅲ)/MAO体系。3种体系所得聚乙烯的相对分子质量均较高且分布较宽。以甲苯为溶剂时催化活性较高,以环己烷为溶剂时产物中的聚乙烯含量较高。

Three PX ligands,namely [2-（diphenylphosphino）ethyl]methyl sulfide（L1）,[2-（diphenylphosphino）ethyl]methyl ether（L2） and 2-（diphenylphosphino）-N,N-dimethyl ethamine（L3）,were synthesized. PX/Cr（ Ⅲ）/MAO catalyst systems were prepared through the complexation reaction between CrCl_3（THF）3 and the ligands with methylaluminoxane（MAO） as the cocatalyst. The performances of the catalytic systems for ethylene oligomerization/polymerization were investigated. The ligands and the products of the oligomerization/polymerization were characterized by means of ~1H NMR,^（13）C NMR,^（31）P NMR,GC and GPC. It was revealed that,with reaction temperature rise,the catalytic activities of the PX/Cr（ Ⅲ）/MAO systems firstly increased and then decreased,and the catalytic activity increased with the increase of reaction pressure. The catalytic activity of the L1/Cr（ Ⅲ）/MAO system was lower than those of the L2/Cr（ Ⅲ）/MAO and L3/Cr（ Ⅲ）/MAO systems. The relative molecular masses of the polyethylene products obtained with the three systems were high and their distributions were wide. The catalytic activity with toluene as the solvent was higher than that with cyclohexane as the solvent,but the polyethylene content in the products was higher when the latter was used as the solvent.