The chemistry of magnesium chloride supported catalysts for polypropylene

Abstract

The reactions between the components of high activity catalysts for polypropylene, aluminum alkyls, magnesium chloride, titanium halides and Lewis bases, are discussed with particular reference made on their influence on the activity and stereospecificity of the catalytic system.

Propene/Ethene-[1-13C] Copolymerization as a Tool for Investigating Catalyst Regioselectivity. MgCl2/Internal Donor/TiCl4−External Donor/AlR3Systems

“…Results of chain end group analysis for polypropylene samples prepared in the presence of catalyst systems (similar to) 1 and 2 at variable H 2 pressure indicate that, in the limit of p (H 2 ) → 0, the fraction of n -butyl ends generated by hydrogenolysis of dormant chains is substantially higher in the latter case, which points to a correspondingly higher value of x d * (or, equivalently, to a lower value of k sp / k ps ) 13c. With these systems, catalyst productivity in the presence of hydrogen is typically a factor 3−5 higher than is observed in the absence of hydrogen. , This hydrogen activation effect appears to be greatest for the diether-containing catalyst 2 , in line with the higher proportion of n -butyl-terminated chains, but it should also be taken into account that in the case of ester-containing systems the overall activating effect of hydrogen may be limited by partial catalyst deactivation resulting from reaction of the ester with Ti−H bonds formed in chain transfer with hydrogen …”

“…15,22 This hydrogen activation effect appears to be greatest for the diether-containing catalyst 2, in line with the higher proportion of n-butylterminated chains, but it should also be taken into account that in the case of ester-containing systems the overall activating effect of hydrogen may be limited by partial catalyst deactivation resulting from reaction of the ester with Ti-H bonds formed in chain transfer with hydrogen. 23…”

Effects of Internal and External Donors on the Regio- and Stereoselectivity of Active Species in MgCl2-Supported Catalysts for Propene Polymerization

“…Nevertheless, and in contrast to the diether-and phthalate-based systems, an activating effect of hydrogen is generally not observed. Giannini [29] has proposed that this is due to the use of an ester as external as well as internal donor, the reaction of the ester with the titaniumhydrogen bond formed in chain transfer with hydrogen leading to the formation of a Ti1O bond inactive for chain propagation.…”

Catalyst Type Effects on Structure/Property Relations of Polypropylene Random Copolymers

“…The rapid decay of the activity can at least partially be ascribed to the aromatic monoester reaction with Ti-H bonds formed in chain transfer with hydrogen, generating Ti-O bonds, inactive for chain propagation. [28] 2.1.3. Fourth-Generation ZN Catalysts-Gas-Phase, Bulk, and Hybrid Processes…”