Two (SiO₂/MgR₂/MgCl₂)·TiCl_x model catalysts are made by refluxing TiCl₄ with 0.35 wt% Cr modified silica gel/alkyl Mg adducts or silica gel/alkyl Mg adducts, which are named as Cr/Ti‐based bimetallic Cat‐1 and Ti‐based monometallic Cat‐2, respectively. The kinetics, active center counting, morphology, and polymer characterizations are studied to disclose the effect of low loading Cr active sites on the Cr/Ti‐based bimetallic Cat‐1 polymerization under mild conditions. The activity of Cat‐1 is 120.4% higher than that of Cat‐2, with a 114.1% higher [C*]/[M] value. Morphology results show the Cat‐1 fragmentation in the first 3 min is highly accelerated, which helps to release buried clustered Ti sites. Differential scanning calorimetry results show that low‐temperature heat absorbing shoulder of polyethylene (PE) from Cat‐2 demonstrates the signal of low crystallinity polymer made by Cat‐2 during the first 60 s, verifying the fluffy polymer in morphology results. GPC results show PE from Cat‐1 has a higher M_w in the first 3 min while a lower M_w in the end. The Cat‐1, which release active sites faster, has a high M_w in the early time. Lower M_w in the 900 s attributes to the effect of relative lower M_w polymer made by Cr sites, compared with Cat‐2.

中文翻译：

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Cr / Ti基双金属催化剂和Ti基单金属催化剂进行乙烯聚合的动力学和机理比较

两种（SiO ₂ / MgR ₂ / MgCl ₂）·TiCl _x模型催化剂是通过将TiCl ₄与0.35 wt％Cr改性的硅胶/烷基Mg加合物或硅胶/烷基Mg加合物（称为Cr / Ti-）回流制备的基双金属Cat-1和钛基单金属Cat-2。研究了动力学，活性中心计数，形态和聚合物表征，以揭示低负荷Cr活性位点在温和条件下对Cr / Ti基双金属Cat-1聚合的影响。Cat-1的活性比Cat-2高120.4％，[ C *] / [ M高114.1％] 价值。形态学结果表明，在前3分钟内Cat-1碎裂被大大加速，这有助于释放掩埋的簇状Ti部位。差示扫描量热法的结果表明，来自Cat-2的聚乙烯（PE）的低温吸热肩部展示了Cat-2在最初的60 s内产生的低结晶度聚合物的信号，证实了蓬松的聚合物的形态结果。GPC结果表明PE距离Cat-1具有更高的中号_瓦特在而较低的前3分钟中号_瓦特到底。Cat-1释放活动站点的速度更快，早期具有较高的M _w。900 s中的较低M _w归因于相对较低M _w的影响 与Cat-2相比，由Cr部位制成的聚合物。