Effect of adduct synthesis parameters on the ethylene polymerization kinetics of Ziegler Natta catalysts

Abstract

Here, it is aimed to clarify the structure-performance relationship in MgCl 2 based Ziegler Natta catalysts toward ethylene polymerizations. In this regard, 11 different adduct precursors were prepared through industrially appreciated melt quenching method employing various: (i) reaction times for dissolving magnesium chloride inside ethanol; (ii) ethanol/MgCl 2 molar ratios in the feed; (iii) heating rates during thermal dealcoholation; (iv) N 2 flows during thermal dealcoholation and (v) alcohol content after thermal dealcoholation. Among the studied parameters, heating rate and N 2 flow during thermal dealcoholation have the most pronounced effect on the porosity and particle size of the resulted adducts. Related Ziegler Natta catalysts were subsequently employed in ethylene polymerizations. According to the kinetic curves, catalyst productivity and form of kinetic curve (as decay or build-up type) can be precisely tailored by proper choosing of the mentioned variables during adduct synthesis. Microstructure analysis of the prepared polyethylenes reveals that alcohol content in the final adduct has the most significant effect on the H 2 response, in terms of molar mass and its distribution, of the related Ziegler Natta catalysts. The overall results help polyethylene producers in choosing proper reaction conditions during adduct synthesis for the production of different polymer grades, when productivity or H 2 response is targeted.

Chemical dealcoholation of MgCl2·EtOH adduct by Al compounds and its effect on the performance of Ziegler–Natta catalysts

“…On the other hand, at extremely lower ethanol contents in the feed, the dissolution of MgCl 2 becomes problematic. As a consequence, an optimal value for the ethanol content in the feed should be considered in the feed 44 …”

“…The MgCl 2 ·(1.5)EtOH adduct was prepared according to our recent publication 44 ; 150 mmol MgCl 2 were dissolved in 500 mmol ethanol containing 15 g silicon oil (viscosity: 100 cps), at a temperature of 66°C using mechanical stirrer with the speed of 300 rpm. After dissolution, 40 mL silicon oil was added to the mixture and the temperature was increased to 110°C.…”

“…The synthesis of Ziegler–Natta catalysts was performed according to a procedure mentioned in our recent research with some modifications as follows 44 . In a 250 mL round bottom flask, 1.0 g of MgCl 2 ·1.5 EtOH (0.0061 mol) adduct together with 15 mL dry toluene were mixed at −20°C under inert atmosphere.…”

“…Besides exploring the microstructure of the resulting catalysts, the effect of the aforementioned Al compounds on the kinetic data of the ethylene polymerization reaction 43 and the characteristics of the final polymers are also assessed. The MgCl 2 Á(1.5)EtOH adduct was prepared according to our recent publication 44 ; 150 mmol MgCl 2 were dissolved in 500 mmol ethanol containing 15 g silicon oil (viscosity: 100 cps), at a temperature of 66 C using mechanical stirrer with the speed of 300 rpm. After dissolution, 40 mL silicon oil was added to the mixture and the temperature was increased to 110 C. After 2 h of stirring, the reaction mixture was transferred to another reactor containing 700 mL of dry hexane at À17 C with continuous stirring at 400 rpm.…”

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

“…[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] Similar deconvolution studies were used to understand the effect of polymerization conditions and catalyst formulations for the polymerization of ethylene and α-olefins with Ziegler-Natta [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] and Phillips/chromium catalysts. [82][83][84] Other studies used MWD deconvolution to identify active site populations for the polymerization of 1-octene, [85] 1-hexene, [86][87][88][89] and 1-butene [90,91] with Ziegler-Natta catalysts. An alternative MWD deconvolution algorithm, using the cumulative version of Flory distribution, has also been proposed but has not been widely adopted.…”