title: Behaviors in ethylene polymerization of MgCl₂-SiO₂/TiCl₄/THF Ziegler-Natta catalysts with differently treated SiO₂.
abstract: The present research focuses on investigation of the catalytic behaviors of MgCl₂-SiO₂/TiCl₄/THF Ziegler-Natta (ZN) catalysts with fumed SiO₂ variously treated with silane compounds. The non-treated silica (NTS) and other silicas treated with dimethylsilicone fluid (TSDMSF), dimethyldichlorosilane (TSDMDCS), and hexamethyl-disilazane (TSHMDS) were employed. It was found that the Cat-TSDMDCS and Cat-TSHMDS exhibited remarkably high activity, even with a similar bulk Ti content as the others. Thus, the more powerful technique of XPS analysis was used to determine the Ti content at the catalyst surface. It was evident that the surface concentrations of Ti could play important role on the catalyst activity. As the result, the increased activity is proportional to the surface concentration of Ti. It was mentioned that the change in surface concentration of Ti with different treated silica can be attributed to the effect of silane spacer group and steric hindrance. The distribution of Ti on the external surface can be also proven by means of EDX mapping, which matched the results obtained by XPS analysis. The treated silica also resulted in narrower molecular weight distribution (MWD) due to the more uniform active sites produced. There was no significant change in polymer morphology upon treatment of the silica.
authors.affiliation: Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Nichapat
authors.initials: N
authors.lastname: Senso
authors.forename: Bunjerd
authors.initials: B
authors.lastname: Jongsomjit
authors.forename: Piyasan
authors.initials: P
authors.lastname: Praserthdam
mesh_terms: D002384:Catalysis; D002850:Chromatography, Gel / Q000379:methods; D005030:Ethylenes / Q000737:chemistry*; D015636:Magnesium Chloride / Q000737:chemistry*; D015394:Molecular Structure; D008970:Molecular Weight; D058105:Polymerization; D011108:Polymers / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D014025:Titanium / Q000737:chemistry*
chemical_list: D005030:Ethylenes; D011108:Polymers; D015636:Magnesium Chloride; D012822:Silicon Dioxide; C025096:titanium tetrachloride; C036216:ethylene; D014025:Titanium