Thesis (D.Eng.)--Chulalongkorn University, 2011

Heterogeneous Ziegler-Natta catalysts for ethylene polymerization were prepared with various support systems, MgCl₂, MgCl₂/SiO₂ and Mg(OEt)₂. The objectives are to improve the morphology of catalyst and to decrease the fragmentation of catalyst’s particle during catalyst preparation. For MgCl₂/TiCl4 and MgCl₂/SiO₂/TiCl4, the MgCl₂ support was prepared via recrystallization of anhydrous MgCl₂ in ethanol-hydrocarbon solution. The bi-support (MgCl₂/SiO₂) was prepared by impregnation of MgCl₂•nEtOH adduct on SiO₂ surface in heptane media. After that, reaction with TiCl₄ was performed to obtain the catalyst. In the case of Mg(OEt)₂/TiCl₄, the MgCl₂ support was prepared by chemical reaction between Mg(OEt)₂ and TiCl4. The result shows that using of SiO₂ in bi-support system could improve morphology of MgCl₂-based catalyst with spherical shape. Moreover, SiO₂ could reduce the effect of ethanol, which is the key parameter to control the morphology and activity of MgCl₂/TiCl₄ catalyst. Hydrogen response in ethylene polymerization and stability of catalyst were also studied. For Mg(OEt)₂/TiCl₄ system, the results show that the morphology of catalyst replicated the morphology of Mg(OEt)₂ precursor and highly catalytic activity was achieved. Additional, the effect of internal electron donor and catalyst’s preparation conditions and catalyst’s performance in ethylene and propylene polymerization were also studied.