Design principles for intrinsically circular polymers with tunable properties

Chem · 2021 · 204 citations

• Nanotechnology
• Materials science
• Polymer science

Insight into Polyethylene and Polypropylene Pyrolysis: Global and Mechanistic Models

Energy & Fuels · 2021 · 89 citations

• Thermodynamics
• Chemistry
• Materials science

Pyrolysis of polyolefins has been proposed as a potential resource recovery strategy by converting macromolecules into valuable fuels and chemicals. Due to variations in possible backbone structures, chain-length distributions, and arrangements of pendant groups, their decomposition behavior via pyrolysis can be complex. In the present work, a review of historical data and empirical models for two distinct polyolefins, polyethylene (PE) and polypropylene (PP), is provided followed by a comparison to recent mechanistic models. The characteristic sigmoidal behavior of linear polymer decomposition is captured with global, lumped-species, and mechanistic models of high-density polyethylene. The PE model was extended to simulate PP using the same reaction families and reaction family parameters, but with distinct rate coefficients that accounted for the difference in the structure of PP with its pendant methyl groups compared to PE as manifested through heats of reaction embedded in the Evans–Polanyi relationship, Ea= E0 + γ×ΔHreacn. The change in structure and its associated kinetic parameters resulted in no sigmoidal conversion, consistent with experimental reports for atactic PP. This suggests that mechanistic modeling could be an important complement to global model studies to understand when other effects are at play in the pyrolytic decomposition of polymers such as PP.

Progress in Modeling of Biomass Fast Pyrolysis: A Review

Energy & Fuels · 2020 · 76 citations

• Computer Science
• Biochemical engineering
• Process engineering

Fast pyrolysis of biomass is an important technology in the conversion of lignocellulosic feedstocks to value-added fuels and chemicals. Significant efforts have been dedicated to modeling of these processes to improve the viability of large-scale operation through reactor design, feedstock selection and processing, and optimization of operating conditions, among others. This work is a review of the current progress in the field of modeling of biomass fast pyrolysis processes across multiple length and time scales. Enclosed are summaries of the current state of the art in atomistic and kinetic modeling of biomass fast pyrolysis toward production of fuels and chemicals. Decomposition of aggregate biomass and its individual components was reviewed for models at various scales, highlighting important considerations. Recent applications of machine learning methods to couple multiscale phenomena with the goal of reducing computational complexity were also included. Historical context was provided for existing models and correlations, highlighting some of those most widely applied. Some of the shortcomings and bottlenecks in existing models were identified as areas for further study. Finally, potential future directions for the field are suggested with the goal of improving the viability and sustainability of pyrolysis processes and the applications of multiscale modeling toward this goal.