The effect of SiO₂ porosity on activity profiles and comonomer incorporation in slurry ethylene/butene-1 polymerization by (SiO₂/MgCl₂/TEOS/TiCl₄) catalyst system

To investigate the influence of support porosity parameters e.g., average pore volume (APV), pore diameter (PD), and pore surface area distribution (PSAD) on activity-profile of catalyst and comonomer incorporation, a series of silica-supports with different porosity were prepared through sol–gel method and used to synthesize corresponding (SiO₂/MgCl₂/TEOS/TiCl₄) catalysts. Polymerization of ethylene/butene-1 showed that increasing of APV from 0.75 to 2.2 cm³ g increase initial activity from 120 to 400 (g_poly/g_cat.bar.hr) followed by appearance of secondary peaks in activity-profile which could be attributed to the variation of PSAD. It is found that the effect of support in polymerization is a complicated issue which depends not only on the porosity parameters also on the comonomer concentration. The catalyst with PD of 300 Å gives higher comonomer incorporation and polymers with 15–20% lower crystallinity in contrast to catalyst with PD of 100 Å. Porosity effect was quantitatively studied by modifying of conventional Z-N catalyst polymerization mechanism through introducing fragmentation term to achieve a new tool in designing and developing of polyolefin catalysts. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011