Phillips catalysts synthesized over various silica supports: Characterization and their catalytic evaluation in ethylene polymerization

Abstract

Ethylene polymerization was carried out using Phillips chromium catalyst based on silica supports such as silica aerogel, SiO2 (Grace 643), and titanium modified SiO2 (G 643), and the results were compared with other catalysts based on SiO2 (Aldrich), SBA-15(Hex), SBA-15(Sp) and MCM-41. A combination of TGA, DSC, XRD, nitrogen adsorption, SEM, ICP, FTIR and other analyses were used to characterize the materials. The results showed that the chromium was successfully introduced into silica supports. Shish-kebab polyethylene was prepared via in situ ethylene polymerization with the Cr/SiO2 (G 643) and Cr/Ti/SiO2 (G 643) catalytic systems. A comparison between different types of catalysts revealed that the polymerization activity of Cr/SiO2 (G 643) was significantly increased to 191 kg PE (g Cr)-1 h-1 due to the higher pore volume and pore diameter of Grace silica compared to the other supports. Also, the polymerization activity of the Cr/SiO2 (G 643) catalyst was significantly improved by Ti-modification.

Keywords

• Silica aerogel
• Grace silica
• chromium catalyst
• Ethylene polymerization
• shish-kebab