1‐Hexene Polymerization over Supported Titanium–Magnesium Catalyst: The Effect of Composition of the Catalytic System and Polymerization Conditions on Temperature Dependence of the Polymerization Rate

Abstract

The effect of temperature on the rate of 1‐hexene polymerization over supported titanium–magnesium catalyst of composition TiCl4/D1/MgCl2 + AlR3/D2 (D1 is dibutyl phthalate, D2 is propyltrimethoxysilane, and AlR3 is an organoaluminum cocatalyst) is studied. The unusual data that the polymer rate decreases when temperature is increased from 30 to 70 °C are obtained. The 1‐hexene polymerization rate and the pattern of changes in polymerization rate with temperature depend on a combination of factors such as cocatalyst (AlEt3 or Al(i‐Bu)3) and presence/absence of hydrogen and an external donor in the reaction mixture. These factors differ in their effects on catalytic activity at different polymerization temperatures, so the temperature coefficient (Eeff) values calculated using the Arrhenius dependence of the polymerization rate on polymerization temperature vary greatly. The “normal” Arrhenius plot where polymerization rate increases with temperature is observed only for polymerization with the Al(i‐Bu)3 cocatalyst in the presence of hydrogen and without an external donor. Formation of high‐molecular‐weight polyhexene at low polymerization temperatures results in catalyst particle fragmentation, which may additionally contribute to the increase in polymerization rate as polymerization temperature is reduced.

Polymerization of Hexene-1 and Propylene over Supported Titanium–Magnesium Catalyst: Comparative Data on the Polymerization Kinetics and Molecular Weight Characteristics of Polymers

“…Our earlier study [ 15 ] revealed that in the case of hexene-1 polymerization over titanium–magnesium catalyst, the composition of cocatalyst (AlEt 3 or Al(i-Bu) 3 ) substantially affects the MWD of the produced polyhexene. In particular, the use of AlEt 3 as a cocatalyst leads to the formation of a polyhexene with a broader molecular weight distribution in comparison with MWD of polyhexene obtained in the presence of the Al(i-Bu) 3 cocatalyst.…”

“…Catalysts of different compositions can be employed to produce polyhexene; among them are traditional Ziegler-Natta type catalysts, supported titanium-magnesium catalysts (TMC) [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], and homogeneous metallocomplex catalysts [ 17 , 18 , 19 , 20 ]. Kinetics of hexene-1 polymerization over Ziegler-Natta catalysts with different composition and data on the effect of catalysts’ composition, and polymerization conditions on the molecular weight and molecular weight distribution of polyhexene are presented and discussed in refs.…”

“…Kinetics of hexene-1 polymerization over Ziegler-Natta catalysts with different composition and data on the effect of catalysts’ composition, and polymerization conditions on the molecular weight and molecular weight distribution of polyhexene are presented and discussed in refs. [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Modern TMC, which are commonly used for stereospecific propylene polymerization, are highly active in hexene-1 polymerization also.…”

Regulation of Molecular Weight Characteristics and Microtacticity of Polyhexene Produced over Highly Active Supported Titanium–Magnesium Catalysts

“…Other details on polymerization conditions and the activity measurements were described in the previous paper. [8]…”

“…We have recently studied the effect of polymerization temperature within the range of 30-70 °C on the polymerization rate at 1-hexene polymerization over supported TMC. [8] It was found that the effect of polymerization temperature strongly depends on composition of the catalytic system and the polymerization procedure, and in particular, on cocatalyst composition (AlEt 3 or Al(i-Bu) 3 ) and presence/absence of the external donor (ED) and hydrogen at polymerization. In most cases, we observed an unusual effect: the polymerization rate decreased with rising polymerization temperature.…”