This study investigates the carbonization behavior of Saskatchewan-sourced lignite coal and leonardite through controlled pyrolysis at 450 °C, 650 °C, and 850 °C, with residence times of 30, 75, and 120 min. The influence of temperature and time on product distribution, reaction pathways, and char properties was systematically evaluated to inform sustainable valorization strategies. Char yields decreased progressively with increasing temperature and time, while liquid yields peaked at 650 °C before declining at higher temperatures. Gas production was maximized at 850 °C, with temperature exerting a more pronounced effect on yield distribution than time, attributed to temperature’s role in initiating the various pyrolytic reactions. In contrast, time only impacted the extent of these reactions. Although char yields from both feedstocks were comparable across all conditions, Leonardite consistently produced more gas, whereas lignite yielded more liquid products. Kinetic analysis via the Coats-Redfern method effectively modeled pyrolysis under first-order assumptions up to 700 °C, revealing lower apparent activation energies for leonardite (5–26 kJ/mol) compared to lignite (12–32 kJ/mol) across two devolatilization phases (Stages 1 & 2) due to its weathered, oxygen-dense structure. While higher-order models (second and third orders) and elevated thermal regimes (700–800 °C) modeled complex reactions, lower correlation coefficients (R2 < 0.98) and drastically elevated activation energies (surpassing 250 kJ/mol) of these models highlighted the limitations of classical model-fitting in isolating true chemical kinetics under complex mass-transfer constraints. The findings provide critical insights into the thermochemical conversion of low-rank coals and oxidized humic substances, offering a foundation for their tailored use in carbon-based materials, adsorbents, and energy applications.
- Open Access
- Article
Carbonization of Lignite Coal and Leonardite through Pyrolysis for Sustainable Post-Combustion Applications
- Hussameldin Ibrahim * and
- Jephthah T. Ofoe
Author Information
Received: 09 August 2026 | Revised: 02 September 2026 | Accepted: 07 September 2026 | Published: 04 November 2026
Abstract
Keywords
pyrolysis | temperature | time | product pathways | product distributions
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