Introduction of chromium species into the (SiO2/MgO/MgCl2)·TiClx Ziegler–Natta catalyst for better catalytic performance

作者：Jingwen Wang; Ruihua Cheng; Xuelian He; Zhen Liu; Ning Zhao; Boping Liu

来源：Journal of Organometallic Chemistry, 2015, 798: 299-310.

• Cr-modification
• Ziegler–Natta polymerization
• Copolymerization
• Kinetics (polym.)
• Short chain branch distribution

A novel chromium-modified (SiO2/MgO/MgCl2)·TiClx Ziegler–Natta ethylene polymerization catalyst with improved catalytic properties is successfully developed. The catalyst is prepared through co-impregnation of water-soluble magnesium and chromium compounds with SiO2 followed by calcination in dry air and refluxing reaction with TiCl4 to synthesize magnesium dichloride in situ, and the supporting of titanium species is also accomplished simultaneously. By characterization of the catalysts and the polymers, several key factors such as cocatalyst concentration, the addition amount of chromium species, the effect of hydrogen and 1-hexene in ethylene polymerization are systematically investigated. Compared with the original (SiO2/MgO/MgCl2)·TiClx Ziegler–Natta catalyst, the novel Cr-modified catalyst with proper initial addition amount of chromium shows better catalytic performance with 13% higher activity, 40% higher hydrogen response, and 20% higher 1-hexene incorporation ability with better short chain branch distribution.