Kinetic modeling frameworks for the chemical recycling of polyolefins

Ge, Jiankai

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https://hdl.handle.net/2142/132535 Copy

Description

Title

Kinetic modeling frameworks for the chemical recycling of polyolefins

Author(s)

Ge, Jiankai

Issue Date

2025-12-01

Director of Research (if dissertation) or Advisor (if thesis)

Peters, Baron G

Doctoral Committee Chair(s)

Peters, Baron G

Committee Member(s)

• Schweizer, Kenneth S
• Mironenko, Alexander V
• Bickel Rogers, Elizabeth

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemical recycling
• Kinetics
• Modeling
• Polyolefins

Abstract

Plastics have become essential to modern life, yet their durability has led to a global waste challenge (> 360 Mt per year). Among this gigantic among of plastic wastes, most of them have been landfilled, incinerated, or even mismanaged. Only a small portion of them have been recycled. However, current mechanical recycling cannot solve the issue that material properties will degrade during the recycling process. Chemical recycling offers new pathways by converting polymers back into valuable molecules selectively, but the underlying reactions are extremely complex due to a wide range of chain lengths in polymers, different features and functional groups among products, and different phases in a reactor scale that stretch traditional kinetic tools past their limits. This dissertation develops a set of kinetic modeling frameworks for the chemical recycling of polyolefins. First, we examine mass-transfer limits using a diffusion–reaction model that describes how processive catalysts perform inside stagnant and stirred polymer melts. The core of the dissertation then advances the mechanistic modeling for polyethylene (PE) and polypropylene (PP) depolymerization. We begin with a length-agnostic microkinetic model (MKM) that includes all surface and bulk species for a model compound, allowing extraction of rate constants and validation of mechanistic hypotheses from experiments. Then, we started with PP pyrolysis mechanism to build a continuous feature x population balance models (PBMs) that resolve the realistic molecular weight distribution (MWD) while keeping track of the evolution of functional motifs such as double bonds or end groups with a feature balance framework (FBM). We show how FBMs can be coupled to PBMs to follow both detailed kinetics and evolving MWDs across multiple species and predict experimental observables and MWDs.

Graduation Semester

2025-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/132535

Copyright and License Information

Copyright 2025 Jiankai Ge

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