单茂钛催化剂的苯乙烯间规聚合和乙烯聚合的比较

STUDIES ON SYNDIOSPECIFIC POLYMERIZATION OF STYRENE AND POLYMERIZATION OF ETHYLENE WITH NOVEL TITANOCENE CATALYST

考察三甲基铝（ＴＭＡ） 部分水解法制备固体改性甲基铝氧烷（ｍ ＭＡＯ） 时，反应物Ｈ２Ｏ 和ＴＭＡ 的摩尔比对ｍ ＭＡＯ 的产量及ｍ ＭＡＯ 中ＴＭＡ 含量的影响；以五甲基茂基三苄氧基钛［Ｃｐ ＊ Ｔｉ（ＯＢｚ）３］／ｍ ＭＡＯ 组成的均相催化体系，分别考察ｍ ＭＡＯ 的用量［ 即Ａｌ／Ｔｉ 摩尔比］ 及ｍ ＭＡＯ 中ＴＭＡ 含量对苯乙烯间规聚合和乙烯聚合的影响．通过分析Ｃｐ ＊ Ｔｉ（ＯＢｚ）３／ｍ ＭＡＯ 催化体系钛氧化态的分布，发现Ｔｉ（ Ⅲ） 活性中心有利于合成间规聚苯乙烯；而Ｔｉ（ Ⅳ） 活性中心有利于合成聚乙烯．苯乙烯间规聚合时，外加三异丁基铝（ＴＩＢＡ） ，将提高催化活性，同时可节省ＭＡＯ 用量．

Syndiotactic polystyrene (sPS) and polyethylene were comparatively synthesized with homogeneous catalytic systems composing η\+5 \|pentamethycyclopentadienyltribenzyloxy titanium \[Cp\+*Ti(OBz)\-3\] and various modified methylaluminoxanes (mMAO).The content of TMA in mMAO can be controlled by regulating H\-2O/TMA molar ratio during the preparation of mMAO by partial hydrolysis of TMA with Al\-2(SO\-4)\-3·18H\-2O.The effect of Al/Ti molar ratio on polymerization of styrene as well as ethylene have been studied in detail. The oxidation states of titanium in Cp\+*Ti(OBz)\-3/MAO catalytic systems were determined by redox titration method. It seems that active centre of Ti(Ⅲ) is favorable for styrene syndiospecific polymerization with higher catalytic activity, while Ti(Ⅳ) center is favorable for ethylene polymerization. The styrene syndiospecific polymerization may also be influenced by the external addition of tri\|isobutyl\|aluminum(TIBA) into the same catalytic sistem giving higher yield but slightly lower molecular weight of sPS.