Effects of diethylaluminum ethoxide pre-reduction and chromium loading over bistriphenylsilyl chromate/silica for ethylene polymerization,The Canadian Journal of Chemical Engineering

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Effects of diethylaluminum ethoxide pre-reduction and chromium loading over bistriphenylsilyl chromate/silica for ethylene polymerization
The Canadian Journal of Chemical Engineering ( IF 1.6 ) Pub Date : 2023-04-25 , DOI: 10.1002/cjce.24930
Xiaofeng Xue ₁ , Yang Yang ₁ , Yuli Gao ₂ , Jianjun Yi ₂ , Boping Liu ₁ , Yulong Jin ₁

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Bistriphenylsilyl chromate (BC)/silica (S-2 catalyst) is a commercially used high-density polyethylene (HDPE) catalyst with great importance. In this work, the catalytic performance of this catalyst was tried to be improved by increasing the loading amount of Cr and pre-reducing with diethylaluminum ethoxide (DEALE). It is found that, when the Cr loading amount was doubled, the productivity in gPE · g⁻¹Cat became almost doubled as well, indicating the maintenance of overall efficiency for Cr centres. Meanwhile, pre-reduction of BC/silica with a small amount of DEALE (the molar ratio of DEALE/Cr < 2.4) was adequate to promote its productivity greatly, while large dose of DEALE led to the activity decay fast, which might originate from the over-reduction of the Cr centre, as well as pore blockages caused by the added DEALE. Moreover, it is found that both the increased Cr loading and DEALE pre-reduction offered an alternative way to reduce the weight-average molecular weight (MW) and molecular weight distribution (MWD) of the polyethylene products mainly by shaving the high MW shoulder.

中文翻译：

乙醇二乙基铝预还原和铬负载对双三苯基硅基铬酸酯/二氧化硅对乙烯聚合的影响

双三苯基甲硅烷基铬酸酯（BC）/二氧化硅（S-2催化剂）是一种非常重要的商业化高密度聚乙烯（HDPE）催化剂。本工作尝试通过增加Cr负载量和乙醇二乙基铝(DEALE)预还原来提高该催化剂的催化性能。结果发现，当Cr负载量加倍时，gPE·g ^{-1的生产率}Cat 也几乎翻了一番，表明 Cr 中心的整体效率得以维持。同时，少量DEALE（DEALE/Cr摩尔比<2.4）预还原BC/二氧化硅足以大幅提高其产率，而大剂量DEALE则导致活性快速衰减，这可能是由于Cr 中心的过度还原，以及添加 DEALE 造成的孔隙堵塞。此外，研究发现，增加Cr负载量和DEALE预还原提供了一种主要通过削除高MW肩部来降低聚乙烯产品的重均分子量（MW）和分子量分布（MWD）的替代方法。

更新日期：2023-04-25

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