Decoding the Hydrogen-Transfer Synergy in Camellia oleifera Shell Hydrochar/HDPE Co-Pyrolysis: A Kinetic and Thermodynamic Perspective.

Authors

Akash Kumar, Lata Kumari, Asma Leghari, Azhar Ali Laghari, Imtiaz Ali Jamro, Moses Akintayo Aborisade, Belay Tafa Oba, Qiuxia Meng, Qiang Zhang

Published in

Polymers. Volume 18. Issue 19. Oct 04, 2026. Epub Oct 04, 2026.

Abstract

This study examined the co-pyrolysis of high-density polyethylene (HDPE) and hydrochar from Camellia oleifera shell (HCS), focusing on thermal decomposition behavior, non-isothermal kinetics, thermodynamics, and the interaction mechanism between the two feedstocks. Hydrothermal carbonization raised the heating value of Camellia oleifera shell from 18.07 MJ/kg (raw CS) to 20.80 MJ/kg (HCS), confirming its fuel-upgrading effect, while HDPE alone reached 46.40 MJ/kg. TG-DTG analysis of HDPE, HCS, and their blends at five HCS:HDPE mass ratios (1:9, 3:7, 5:5, 7:3, and 9:1, denoted 1HCS9HDPE through 9HCS1HDPE) at 5-25 °C/min showed a single sharp decomposition stage for HDPE, a broader profile with much higher char yield for HCS, and non-additive DTG behavior in the blends, pointing to a synergistic interaction. Isoconversional kinetics (FWO, KAS, Starink, Friedman) showed activation energy rising steadily with conversion for HDPE (170-240 kJ/mol), a plateau-then-sharp-rise pattern for HCS (180-400 kJ/mol), and marked fluctuations at intermediate conversion for the balanced blends, a signature of composition-dependent synergy. Thermodynamic analysis (ΔH, ΔG, ΔS) confirmed an endothermic, non-spontaneous process throughout, with entropy trends mirroring the kinetic fluctuations. A hydrogen-radical transfer mechanism between HDPE- and hydrochar-derived intermediates is proposed to explain the reduced char yield and non-additive behavior of the blends. Overall, the results support hydrochar-HDPE co-pyrolysis as a viable route for combined agricultural and plastic waste valorization and provide kinetic and mechanistic data to guide co-pyrolysis process design.

PMID:
42885053
Bibliographic data and abstract were imported from PubMed on 16 Oct 2026.

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