Yi Zhou,Rui Zhang,He Ren,Xuelian He,Bao Liu,Ning Zhao,Boping Liu
A series of novel V/Ti bimetallic polyethylene catalysts were developed successfully through the introduction of vanadium species into the (SiO 2 /MgR 2 /MgCl 2 )·TiCl x Ziegler-Natta Catalyst. The organometallic heterogeneous catalysts combined advantages of reducibility of magnesium alkyl on the activation of secondary metal active sites (vanadium active sites), which successfully enhanced average molecular weight in homopolymer products and produced dominantly bimodal molecular weight distribution in copolymer products. Catalyst preparation conditions including calcination temperature and magnesium dosage were investigated to explicit the effect on the relative performance of different metal active centers. Moreover, the factors including hydrogen and ethylene/1-hexene copolymerization were systematically studied. The bimetallic catalysts exhibit 63.9% enhancement on activity, 37.3% better hydrogen response than the original (SiO 2 /MgR 2 /MgCl 2 )·TiCl x organic magnesium Ziegler-Natta catalyst. Moreover, a simplified schematic model was proposed to elaborate on the reason why the bimetallic catalysts showed much higher activity than the original one, and each active species performance well. Vanadium active sites react quickly in the initial reaction time on the external surface of the support, which helps titanium active sites crack the catalyst particles together in the fragmentation and activation stage; then the released internal surface active sites, which were accessible to the monomer in the slurry phase, speed up the polymerization reaction during the latter reaction process.
Wenqian Kang,Xiong Wang,Yue Ren,Pingsheng Zhang,Anping Huang,Guangquan Li
Porous organic polymers (POPs) are attracting attention for their easy functionalization and potential as catalyst supports in olefin polymerization. In this study, sulfonated POP (s-POP) supported Ziegler–Natta catalysts were used for ethylene polymerization, producing ultra-high molecular weight polyethylene, with Mν reaching up to 6.83 × 106 g mol−1. The maximum Mν of polyethylene was achieved by Cat-3 with DIBP as the internal donor, albeit with a partial loss of catalytic activity. Polymerization conditions also play a pivotal role in determining the molecular weight of polyethylene. Hydrogen, being the most efficient chain transfer agent, can decrease the molecular weight to 9.68 × 104 g mol−1 at higher hydrogen concentrations ([H2] : [C2H4] = 0.83), and the s-POP-supported ethylene polymerization catalysts were observed to exhibit high sensitivity to hydrogen response. The effects of polymerization temperature, [Al] : [Ti] molar ratio, and ethylene pressure on ethylene polymerization were thoroughly investigated.
危险品化学品经营许可证（带存储）