Identification of Site Types for Ethylene/1‐Olefin Copolymerization in Two‐Reactor System Using Simultaneous Deconvolution of Molecular Weight and Chemical Composition Distribution

Abstract

Ethylene/1-olefin copolymers have been commercially produced with multiple-site-type Ziegler-Natta catalysts in a two-reactor system, which allows the production of polymers with a broad range of microstructures and properties. In this work, the simultaneous deconvolution procedure for two-reactor system is developed to help identify an appropriate number of site types for catalysts in each reactor, estimate chain microstructures, and mass fraction of polymers produced on each site type, and also estimate mass fraction of polymers produced from each reactor. This simultaneous deconvolution procedure will allow us to understand the behavior of each site type in each reactor, which will lead to a better control of polymer chain microstructures for such a complex system.

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

“…They also applied their method to deconvolute the CFC of ethylene/1‐butene copolymers made with a Ziegler–Natta catalyst into multiple Stockmayer distributions. Chayrattanoroj and Anantawaraskul [ 129 ] extended this joint deconvolution approach for digital multiple‐site‐type copolymers made in dual reactors in series (bimodal polyethylenes). Finally, Khayanying and Anantawaraskul [ 130 ] used a genetic algorithm to improve the convergence properties of their joint MWD × CCD deconvolution method.…”

Modeling Propylene Polymerization in a Two‐Reactor System: Model Development and Parameter Estimation

“…The model can be calculated using the following procedure. First, the model estimates the yields of polymer made on each site type in the first (Yield r1,j ) and the second (Yield r2,j ) reactors using Equations ( 18) and (21), respectively. This calculation step uses the kinetic parameters listed in Table 7 and polymerization times in each reactor.…”

“…Unfortunately, the conventional MWD deconvolution procedure cannot be directly applied to products made in dual reactor systems. [ 21 ] Although the MWD of the polymer made in the two‐reactor system can be easily deconvoluted, it is hard, and perhaps even impossible, to identify what was the reactor in which a given polymer population was produced. Therefore, a new approach for MWD deconvolution for polyolefins made in two‐reactor (and multi‐reactor) systems is required.…”

“…Microstructural distribution deconvolution is a technique that can be used to identify the minimum number of site types and determine the mass fractions and microstructures of polymer populations produced on each site type from the overall microstructural distribution. [10][11][12][13][14][15][16][17][18][19][20][21][22] Deconvolution methods based on MWD measured with gel permeation chromatography (GPC) have been widely successful in many applications. [23][24][25][26][27][28][29][30][31][32][33] Typically, this method assumes that the MWD of polyolefin populations produced on each site type follows Flory's most probable distribution (MPD), as demanded from the mechanism of olefin polymerization with coordination catalysts.…”

“…Polymerization processes with two-reactor systems have been used in industry because they can make polypropylene with a broader range of microstructures and properties by adopting different feeding policies and/or operating conditions in both reactors. [1,21] For example, different hydrogen concentrations can be used to regulate the MWDs of polymer made in each reactor, while different reactor residence times can be used to control the mass fractions of polymers (product split) made in each reactor. Unfortunately, the conventional MWD deconvolution procedure cannot be directly applied to products made in dual reactor systems.…”