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

Abstract

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 (SiO 2 /MgCl 2 /TEOS/TiCl 4 ) catalysts. Polymerization of ethylene/butene-1 showed that increasing of APV from 0.75 to 2.2 cm 3 g À1 SiO2 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.

Condensed Mode Cooling for Ethylene Polymerization: Part II. The Effect of Different Condensable Comonomers and Hydrogen on Polymerization Rate

“…However, they also proposed that as the 1‐hexene concentration increased, a bulk convection effect led to its accumulation in the particles, and since it has a lower reactivity than ethylene, this in turn led to an overall lower reaction rate. Vakili et al also observed that silica particles with larger pores (and thus an increased friability) also gave a stronger comonomer effect in slurry copolymerization of 1‐butene and ethylene.…”