新型Cr(Ⅲ)络合物/甲基铝氧烷催化乙烯齐聚

Ethylene Oligomerization Catalyzed by Novel Cr(Ⅲ) Complex/Methylaluminoxane

合成并表征了1,4-双（二苯基膦）哌嗪（配体Ⅰ）及其与Cr Cl3（THF）3（THF为四氢呋喃）形成的络合物（络合物Ⅰ）。以甲基铝氧烷（MAO）为助催化剂,考察了反应温度、反应压力、n（Al）∶n（Cr）等因素对络合物Ⅰ催化乙烯齐聚性能的影响。实验结果表明,当以甲苯为溶剂时,在反应压力4.0 MPa、反应温度80℃、n（Al）∶n（Cr）=600、c（Cr）=0.18 mmol/L的条件下,催化活性可达3.72×106 g/（mol·h）,其中,C4~14线型α-烯烃的选择性可达97.99%。考察了复合助催化剂对络合物Ⅰ催化乙烯齐聚性能的影响。当以甲基环己烷为溶剂、助催化剂为不含Al Me3的MAO与Al Et3的复合物时,产物为高相对分子质量的线型聚乙烯。

A novel ligand,1,4-bis（diphenylphosphino） piperazine（ligandⅠ）,and a complex,ligandⅠ/Cr Cl3（THF）3（THF：tetrahydrofuran）（complexⅠ）,were synthesized and characterized. ComplexⅠ exhibited high catalytic activity and selectivity for the oligomerization of ethylene to linear α-olefi n with methylaluminoxane（MAO） as cocatalyst. The effects of reaction temperature,reaction pressure,the mole ratio of Al to Cr on the performance of the catalytic system were investigated. The results showed that,the catalytic activity reached 3.72×106 g/（mol·h） and the selectivity to C4-14 linear α-olefi ns was 97.99% under the reaction conditions of toluene as solvent,reaction pressure 4.0 MPa,reaction temperature 80 ℃,the mole ratio of Al to Cr 600 and Cr concentration 0.18 mmol/L. The effect of the composite cocatalyst on the complex Ⅰ catalyst in the ethylene oligomerization was studied. The major product was linear polyethylene under the conditions of methylcyclohexane as solvent and DMAO/Al Et3（DMAO：Al Me3-depleted MAO） as cocatalyst.