Abstract
Pyrolysis is a promising thermochemical technique to convert polymers such as waste plastics and lignocellulosic biomass to liquid products that are valuable either directly as or are potentially upgraded to liquid fuels and fine chemical intermediates. Mechanistically, polymer pyrolysis involves a complex set of free radical, concerted, and/or ionic reactions that occur via numerous competing pathways. Engineering these pathways to produce the required molecules warrant a thorough understanding of kinetics of the reactions under different conditions. In this critical review, after emphasizing the need for resource and energy recovery from polymers, the elementary reactions involved in the pyrolysis of polyolefins to various products are discussed along with an elucidation of detailed kinetic modeling. The reactions involved in oxidative pyrolysis of polymers are also discussed with polystyrene autoxidation as an example case. The influence of catalysts such as zeolites in altering the product distribution from pyrolysis of synthetic polymers is discussed. As lignocellulosic biomass is more complex in structure compared to synthetic polymers, the challenges and methodology involved in modeling the degradation of its basic constituents, viz. cellulose, hemicellulose, and lignin, to various organics are discussed. After elucidating the influence of various concerted reactions involved in cellulose pyrolysis on product yields, the effect of catalysts on biomass fast pyrolysis and bio-oil upgradation are discussed. The review concludes with a note on advantages of copyrolysis of synthetic polymers and biomass to enhance the quality of bio-oil that can be easily converted to biofuel with minimal upgradation.
Original language | English (US) |
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Title of host publication | Thermochemical Process Engineering, 2016 |
Editors | Kevin M. Van Geem |
Publisher | Academic Press |
Pages | 95-195 |
Number of pages | 101 |
Volume | 49 |
ISBN (Print) | 9780128097779 |
DOIs | |
State | Published - 2016 |
Keywords
- Catalyst
- Catalytic fast pyrolysis
- Cellulose
- Lignocellulosic biomass
- Mechanism
- Mechanistic kinetic model
- Polymer
- Polyolefins
- Pyrolysis
- Zeolites
ASJC Scopus subject areas
- General Environmental Science
- General Earth and Planetary Sciences