Impact of Process Poisons on the Performance of Post‐Phthalate Supported Ziegler–Natta Catalysts in Gas Phase Propylene Polymerization

Abstract The impact of common process catalyst poisons on the performance of a 6th generation Ziegler–Natta catalysts during the gas phase polymerization of propylene are examined using two approaches: introducing propylene without purification, or with one or two sets of purification columns, and by introducing carbon dioxide (CO 2 ), oxygen (O 2 ), water (H 2 O), methanol (CH 3 OH), ethyl acetate (C 4 H 8 O 2 ) and dimethyl sulfoxide (C 2 H 6 SO) during the polymerization. As expected, purification columns increases the catalyst activity significantly, slightly reduce catalyst decay. Injecting TiBA during the reaction leads to an activity increase. The addition of two full sets of columns substantially increased the repeatability of polymerization reactions. The power of deactivation of poisons injected during the polymerization reaction is: O 2 > CO 2 > CH 3 OH > C 2 H 6 SO > C 4 H 8 O 2 > H 2 O. Adding CO 2 , O 2 , and CH 3 OH resulted in a progressive decrease in molecular weight while almost no effect is observed with H 2 O. However, C 4 H 8 O 2 , and C 2 H 6 SO resulted in a mild increase in molecular weight. Additionally, the effects on crystallinity and stereoregularity are similar where CO 2 , O 2 , H 2 O and CH 3 OH caused a progressive decrease while C 4 H 8 O 2 and C 2 H 6 SO resulted in a mild increase, indicating some isotacticity control by these two poisons.