The reactivity of a phenoxy-imine-ether system (FI)TiCl₃/MAO was studied toward selective ethylene trimerization. This system was shown to either trimerize or polymerize ethylene depending on the reaction temperature. Its selectivity switches from a significant production of the trimerization product, 1-hexene (85 wt%, 520–450 kg_1-hexene g_Ti⁻¹ h⁻¹) between 30 and 40 °C, to a moderate polyethylene formation (70–80 wt%, 60–70 kg_polyethylene g_Ti⁻¹ h⁻¹) at a higher reaction temperature (T > 60 °C). Polymerization was investigated based on an original “polymer-to-catalyst” strategy aiming at identifying the active species responsible for this side reaction. Using DSC, SEC and high temperature ¹³C NMR analyses, polyethylenes were found to exhibit high molar masses (>10⁵ g mol⁻¹) and a low 1-hexene content (<1 mol%) at any temperature. Kinetic studies support that trimerization and polymerization species are generated from the catalyst precursor at 40 °C but a parallel process may occur at a higher temperature. The increase of dispersity to 4.6 at 80 °C suggests a change from single to multi-site catalysis. The poor comonomer incorporation ability of the active species is reminiscent of a molecular Ziegler–Natta or a bulky post-metallocene catalyst.

中文翻译：

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用于选择性乙烯三聚的钛基苯氧基亚胺催化剂：温度对聚合物副产物活性，选择性和性能的影响

研究了苯氧基-亚胺-醚体系（FI）TiCl ₃ / MAO对选择性乙烯三聚反应的反应性。根据反应温度，该体系显示出三聚或聚合乙烯。其选择性从在30至40°C之间大量生产三聚产物1-己烯（85 wt％，520–450 kg _1-己烯g _Ti ^-1 h ^-1）转变为中等程度的聚乙烯形成（70- 80重量％，60–70千克_聚乙烯g _Ti ^-1 h ^-1，在更高的反应温度下（T> 60°C）。基于原始的“聚合物-催化剂”策略研究了聚合反应，旨在确定引起该副反应的活性物质。使用DSC，SEC和高温¹³ C NMR分析，发现聚乙烯显​​示出高摩尔质量（> 10 ⁵ g mol ^-1）和低的1-己烯含量（<1 mol％）在任何温度下。动力学研究支持三聚和聚合反应是在40°C下由催化剂前体产生的，但在更高的温度下可能会发生平行过程。在80°C时，分散度增加到4.6，表明从单点催化转变为多点催化。活性物质共聚单体的结合能力差，让人联想到分子齐格勒-纳塔分子或笨重的后茂金属催化剂。