给电子体在丙烯聚合MgCl_2载体催化剂体系中的作用

研究了不同给电子体分别作为内给电子体(D_(in))和外给电子体(D_(ex))对MgCl_2载体催化剂体系活性和定向性能的影响。还讨论了D_(in)和D_(ex)的搭配作用。烷氧基硅烷、苯甲酸乙酯(EB)、邻苯二甲酸二异丁酯(DIBP)和2,2,6,6-四甲基哌啶(TMP)用作Dex,可以明显改善聚丙烯的等规度,而同时使催化活性大大降低。EB、DIBP和TMP用作D_(in)的效果则各不相同。烷氧基硅烷等D_(ex)提高等规度的作用是由于它们选择性地使无规活性中心失活大大高于等规活性中心。适当的D_(in)和D_(ex)搭配,可以获得兼具高活性和高定向性能的催化剂体系。

EFFECTS OF ELECTRON DONORS ON MgCl2 SUPPORTED CATALYSTS SYSTEM FOR POLYMERIZATION OF PROPYLENE

The effects of different electron donors such as ethyl benzoate(EB) diisobutyl phthalate (DIBP), 2,2,6,6-tetramethyl piperidine(TMP) and various silanes as internal donor (Dm) and external donor(Dex) respectively were investigated.The possible synergistic effect of Din and Dex was discussed.It was found that EB, DIBP, TMP and alkoxysilanes used as Dex could evidently improve the stereospecificity accompanied with a decrease of the activity, while the effects of EB, DIBP and TEM used as Din are quite different from each other. The effects of increasing the stereospecilicity is due to deactivation of different selectivity for both atactic and isotatic active centers and the deactivation of atactic active centers is much greater than that of isotactic active centers.Cooperation of appropriate Din and Dex would give good catalytic performance with high activity and high stereospecifity.