Effect of EtOH/MgCl2 Molar Ratios on the Catalytic Properties of MgCl2-SiO2/TiCl4 Ziegler-Natta Catalyst for Ethylene Polymerization

Molecules

Supanan Patthamasang¹  Bunjerd Jongsomjit¹ 

[1] Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand

关键词: Ziegler-Natta catalyst;    silica;    MgCl₂;    ethanol;    spherical support;    morphology;    polyethylene;   

DOI  :  10.3390/molecules16108332

来源: mdpi

【 摘 要 】

MgCl₂-SiO₂/TiCl₄ Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl₂ on SiO₂ in heptane and further treatment with TiCl₄. MgCl₂^·nEtOH adduct solutions were prepared with various EtOH/MgCl₂ molar ratios for preparation of the MgCl₂-supported and MgCl₂-SiO₂-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl₂] for the MgCl₂-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl₂-SiO₂-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl₂] ratio. The lower [EtOH]/[MgCl₂] in MgCl₂-supported catalyst exhibited better catalytic activity. However, for the MgCl₂-SiO₂-supported catalyst, MgCl₂ can agglomerate on the SiO₂ surface at low [EtOH]/[MgCl₂] thus not being not suitable for TiCl₄ loading. It was found that the optimized [EtOH]/[MgCl₂] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl₂ was 7. Morphological studies indicated that MgCl₂-SiO₂-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO₂. The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region.

【 授权许可】

CC BY   
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.