Modeling of sequence length distribution for olefin copolymerization with vanadium‐based catalyst

Abstract

Some thermodynamic and mechanical properties of a polyolefin, such as the melting temperature and the rigidity, are dependent on the nature of its sequence distribution. Accurate modeling of sequence length distribution (SLD) is important in precisely tuning and optimizing the properties of polymers produced. In this article, we proposed a model to predict the molecular weight distribution (MWD) and SLD for olefin copolymerization with vanadium-based catalyst. Due to the 2,1-insertion of α-olefin with vanadium-based catalyst, the SLD is expressed by uninterrupted methylene sequence distribution instead of conventional triad sequence distribution. To obtain a reliable model, parameter estimation with experimental data is first conducted. The SLD model along with the estimated kinetic parameters can be used to predict unmeasurable sequence length fraction. For the experimental conditions studied, the average methylene sequence length is predicted to change from 10 to 4 units as the propylene/ethylene mole feed ratio increases from 1.1 to 3.4.

Predicting Polyethylene Molecular Weight and Composition Distributions Obtained Using a Multi‐Site Catalyst in a Gas‐Phase Lab‐Scale Reactor

“…Cheng et al [42] (2019) 2 L Modeled dynamic ethylene/propylene copolymerization using a vanadium-based catalyst. Used Peng-Robinson EOS to calculate ethylene, propylene, and hydrogen concentrations in the liquid phase.…”

“…Eight of the 20 parameterestimation studies in Table 1 involved gas-phase polymerizations [8,9,26,[28][29][30]34,35] and the other 12 involved solution or slurry polymerization. [7,10,[31][32][33]36,[38][39][40][41][42][43] Eighteen out of 20 studies used real experimental data (the remaining two used data obtained from simulation). [26,40] Monomer partitioning into the polymer near the active sites has been modeled using a relatively simple Henry's Law approach and using equations of state that account for interactions between species.…”

“…Propagation and chain-transfer rate constants have been estimated using monomer consumption rates, comonomer composition, and average molecular-weight data. [7,10,34,[39][40][41][42][43] In multi-site systems, MWD deconvolution techniques have been used to aid the estimation of parameters for individual catalyst sites. [26,34,39,41] Only two studies used actual NMR sequence data to aid parameter estimation.…”

Kinetic Parameter Estimation for Linear Low-Density Polyethylene Gas-Phase Process from Molecular Weight Distribution and Short-Chain Branching Distribution Measurements

“…Orthogonalization algorithm and Wu’s mean squared error (MSE) based method are widely used in parameter estimability analysis for polymer chain structure prediction. − ,, Parameters are ranked one at a time in the orthogonalization algorithm (i.e., a forward selection from most estimable to least estimable). Though this method is convenient to apply, Chu and Hahn pointed out that some combinations of parameters giving better results could be excluded because of parameters selected at earlier steps in the orthogonalization algorithm.…”

Deterministic Approach to Estimate Functionality of Chains Produced by Radical Copolymerization in the Presence of Secondary Reactions

“…While commercial polymers range from high-volume commodities to high-value low-volume materials, in all cases designing the material for a targeted application needs an understanding of how operating condition influences molecular structure. − Multicomponent polymeric materials (i.e., those synthesized using a mixture of monomers) impart a tailored set of properties not achievable from a homopolymer blend. Functionalized copolymer chains are often synthesized as the first step for a given application, with final properties of the material developed through the subsequent reaction of the pendant functional groups that have been first incorporated through direct copolymerization.…”