新型水杨醛亚胺钛催化剂的制备及乙烯聚合研究

Preparation of a novel salicylaldehyde imine titanium catalyst and study on its application in ethylene polymerization

以3-溴水杨醛和取代苯胺为原料合成了水杨醛亚胺配体(1a~1c)及其钛配合物(2a~2c),并在助催化剂甲基铝氧烷(MAO)的作用下将配合物2a~2c在常压下催化乙烯聚合,利用红外、凝胶色谱(GPC)和差示扫描量热法(DSC)对聚合物进行分析。考察了配体结构、聚合温度、n(Al)∶n(Ti)及催化剂用量对聚合行为的影响。结果表明,在35℃、n(Al)∶n(Ti)=2000∶1条件下,配合物2a的催化活性最高,可达1.40×10^(6)g_(PE)/(mol_(Ti)·h),随着亚胺基苯环上取代基空间位阻的增大,所得聚乙烯的分子质量进一步增加,配合物2c所得聚乙烯重均分子质量(M_(w))达到8.3×10^(5)g/mol、分子质量分布(PDI)为2.6。

Salicylaldehyde imine ligands(1a-1c)and its titanium complexes(2a-2c)are synthesized from 3-bromosalicylic aldehyde and substituted aniline,and their structures are characterized by means of 1HNMR,13CNMR and elemental analysis.Under the action of methylaluminoxane(MAO)co-catalyst,the complexes 2a-2c are used to catalyze ethylene polymerization at atmospheric pressure.The polymers obtained are analyzed through using IR,gel permeation chromatography(GPC)and differential scanning calorimetry(DSC).The influences of ligand structure,polymerization temperature,n(Al)∶n(Ti)and catalyst dosage on polymerization behavior are investigated.Results show that under the conditions of 35℃,0.1 MPa and n(Al)∶n(Ti)=2000∶1,the catalytic activity of complex 2a reaches the highest,being 1.40×10^(6)gPE/(molTi·h).As the steric hindrance of the substituents on the imine benzene ring increases,the molecular weight of resulted polyethylene further increases.The weight average molecular weight(M_(w))of polyethylene obtained over complex 2c reaches 8.3×10^(5)g·mol^(-1),and the molecular weight distribution(PDI)is 2.6,indicating good controllability of the polymerization process.