LDPE Production in Tubular Reactors: Comprehensive Model for the Prediction of the Joint Molecular Weight-Short (Long) Chain Branching Distributions

The production of low‐density polyethylene (LDPE) in high‐pressure tubular reactors is widely studied due to its extensive use worldwide. Reaction conditions have a crucial impact on the polymer molecular architecture, which, in turn, influences the rheological behavior of the polymer in the molten state, a very important variable during subsequent processing. Up to now, the relationships between reactor polymerization conditions, polymer microstructure, and final rheological properties are not completely established, although they could be a very useful tool for rapid process control and optimization. This work presents an integrated model of the high‐pressure polymerization of ethylene in tubular reactors, consisting of the combination of a deterministic model of the tubular reactor that calculates molecular properties of the polymer and an empirical rheological model for branched molecules. The integrated model predicts conversion, temperature, and average molecular properties, as well as the bivariate molecular weight‐long chain branching distribution, the branching index, and the shear viscosity flow curve for LDPE under different operating conditions. Results compare well with experimental data of an actual industrial reactor. Additionally, the effect of polymerization conditions on molecular and rheological properties is analyzed.

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“…[ 46 ] Further details on the reactor model and its experimental validation can be found in previous works by the authors. [ 29,39,45–47 ]…”

Section: Model Descriptionmentioning

confidence: 99%

“…More recently, Dietrich et al. [ 29 ] used bivariate probability generating functions (pgf) to transform the initially infinite PBEs, giving as results the bivariate MWD–LCBD and MWD–SCBD, g , and the LCB density curve.…”

Section: Introductionmentioning

confidence: 99%

Modeling Low‐Density Polyethylene (LDPE) Production in Tubular Reactors: Connecting Polymerization Conditions with Polymer Microstructure and Rheological Behavior

Dietrich

Sarmoria

Brandolin

et al. 2022

Macro Reaction Engineering

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“…The value of e g represents the branching index obtained from Dietrich, Sarmoria, Brandolin, and Asteasuain. 37 The branching index information is essential since the LDPE polymer has complex branches, and no general relationship can be obtained unless the rheology of the polymer is characterized. 38 MWW is the weight average molecular weight, which is calculated in the Aspen simulation model using the method of moments.…”

Section: Mfi Modelmentioning

confidence: 99%

Low‐density polyethylene tubular reactor control using neural Wiener model predictive control

Muhammad

Rohman

Ahmad

et al. 2021

Asia-Pacific J Chem Eng

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Low-density polyethylene (LDPE) is a valued commodity plastic with versatile applications. However, controlling the LDPE polymerization reactor is a challenging task due to its nonlinear behavior and multivariable process and operates in a board operating region. This work aims to develop and explore the neural Wiener MPC (NWMPC) application in controlling the LDPE tubular reactor process. The motivation for NWMPC development originates from its advantage in terms of lower development effort, time, resource, and computational costs compared to nonlinear MPC (NMPC) using the first principle model (FPM). In order to develop the LDPE tubular reactor model, the Aspen Plus and Aspen Dynamic software are used to simulate the process in steady-state and dynamic form. The neural Wiener (NW) model identification is performed using state space and neural network model identification using Matlab software. The identification result shows the ability of the NW model to identify the nonlinear LDPE tubular reactor process successfully. Furthermore, the NWMPC has outperformed the state space MPC (SSMPC) in controlling grade transition, feed pressure loss, feed impurity disturbance, and heat of polymerization change during the online closed-loop performance tests. These results signify the ability of NWMPC to handle practical LDPE tubular reactor control scenarios.

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“…The macroradicals can be deactivated in several ways, such as by random scission (reaction 7), termination by combination or by disproportion (reactions 10 and 11). The chain transfers to monomer (reaction 4) and to chain transfer agent (CTA) (reaction 5) produce lower molecular weight molecules …”

Section: Reaction Mechanismsmentioning

confidence: 99%

Prediction of branch on branch and topological characteristics of low‐density polyethylene polymerization by a novel stochastic approach

Taheri

Najafi

Motahari

2020

Polymers for Advanced Techs

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A novel approach using Monte Carlo method applied to simulation of low-density polyethylene (LDPE) polymerization in tubular reactor showing topological characteristics, and the comprehensive kinetic mechanism has been taken into consideration.The results show the precise details of the structure of a chain in the three levels of the backbone, the main branches, and branches on branch. The chain types include dead polymer, dead polymer with unsaturated end, and live polymer with primary radical, secondary radical, and tertiary radical. In this work, the branches on branch were identified in terms of number, length, and position of the branch. Sixty percent of branches on branch are 1 to 5 carbons long, and the longest branch on branch is about 50 carbons. Thus, this study provides a tool for more accurately mapping the polymer chains architecture, superior to determine the number, and position of longand short-chain branches in past researches. Finally, this approach will advance the prediction of microstructure-related properties of polymer one step further. K E Y W O R D S branch on branch, LDPE, Monte Carlo simulation, radical polymerization, topological characteristics

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LDPE Production in Tubular Reactors: Comprehensive Model for the Prediction of the Joint Molecular Weight-Short (Long) Chain Branching Distributions

Cited by 15 publications

References 37 publications

Modeling Low‐Density Polyethylene (LDPE) Production in Tubular Reactors: Connecting Polymerization Conditions with Polymer Microstructure and Rheological Behavior

Modeling Low‐Density Polyethylene (LDPE) Production in Tubular Reactors: Connecting Polymerization Conditions with Polymer Microstructure and Rheological Behavior

Low‐density polyethylene tubular reactor control using neural Wiener model predictive control

Prediction of branch on branch and topological characteristics of low‐density polyethylene polymerization by a novel stochastic approach

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