Ethylene Polymerization and Ethylene/1-Octene Copolymerization with rac-Dimethylsilylbis(indenyl)hafnium Dimethyl Using Trioctyl Aluminum and Borate: A Polymerization Kinetics Investigation

Abstract

The polymerization of ethylene and ethylene/1-octene in a semibatch solution reactor using rac-dimethylsilylbis(indenyl)hafnium dimethyl and tetrakis(pentafluorophenyl) borate dimethylanilinium salt ([B(C6F5)4]−[Me2NHPh]+) as the catalytic system and trioctylaluminum (TOA) as the scavenger was investigated. Ethylene and 1-octene concentrations, polymerization temperature, borate/catalyst ratio, and TOA concentration were changed to study the ethylene polymerization kinetics with this system. The mode of addition for catalyst, borate, and TOA was also studied. When TOA and borate were added sequentially to the reactor followed by the catalyst, the polymerization activity was low and the molecular weight distribution (MWD) bimodal. Contrarily, when TOA was added first to the reactor and a mixture of catalyst and borate were added to the reactor, the polymerization rate was much higher and the MWD unimodal. An augmented 2 × 2 central composite design was used to investigate this phenomenon. Borate helped stabilize the active sites and reduce potential deactivation reactions with excess TOA.

Ethylene Polymerization with a Hafnocene Dichloride Catalyst Using Trioctyl Aluminum and Borate: Polymerization Kinetics and Polymer Characterization

“…The present results extend previously published work [42] with a detailed study on the kinetics of ethylene polymerization using bis(n-propylcyclopentadienyl)hafnium dichloride/borate/TOA catalytic system. A 2 3 central composite design, augmented with some additional runs was used to explore the effect of TOA, borate and catalyst concentrations on the catalyst performance.…”

Quantification of active sites in single-site group 4 metal olefin polymerization catalysis

“…Some studies hypothesize that all (pre)catalyst is active; see e.g. [32][33][34]. However, even though metallocene, hemi-metallocene and post-metallocene complexes provide in principle the same global catalytic environment to all propagating centers (hence the "single-site" nomenclature), it is not guaranteed that they all undergo evenly and entirely the transformation into the active species and that the latter species remain active throughout the polymerization process.…”

The Use of Instantaneous Distributions in Polymerization Reaction Engineering

“…A polymerization kinetic model is needed to calculate ξ i ( t ). Most olefin polymerization kinetic curves can be modeled with relatively simple algebraic expressions . Table lists a model containing three steps (site activation, propagation, and catalyst deactivation) that can be used to describe the polymerization kinetics with the majority of single‐site catalysts.…”