(2026) Journal of Analytical and Applied Pyrolysis_Process intensification of sunflower seed hull pyrolysis via CO₂-assisted catalytic upgrading

Kwon D.; Song H.; Kwon E.E.

(Elsevier B.V.) Journal of Analytical and Applied Pyrolysis ISSN: 1652370 Vol.198 Issue. Article No.107903 DOI: 10.1016/j.jaap.2026.107903

To optimize the thermochemical valorization of sunflower seed hull (SSH), a food-industry residue, this study systematically investigated a CO₂-assisted pyrolysis process. The primary objective was to optimize syngas production and fundamentally investigate the reactive behavior of CO₂. To achieve this, the process configuration was stepwise upgraded from single-stage (SP) to multi-stage (MP), and ultimately to Ni-based catalytic pyrolysis (CP). In SP, CO₂-induced homogeneous reactions increased the CO yield from 7.06 mmol (under N₂) to 24.34 mmol (under CO₂), while decreasing the bio-oil yield from 45.54 to 39.20 wt%. Although MP was introduced to intensify syngas production, the additional effect of CO₂ was limited. By contrast, CP strengthened the CO₂ functional role. Under CO₂, the H₂ and CO yields reached 21.12 mmol and 96.14 mmol, respectively, while the bio-oil yield decreased to 5.63 wt% (compared with 8.49 wt% under N₂). CO₂ activated on the catalyst surface formed reactive intermediates that reacted with volatiles, promoting deoxygenation and cracking to enhance syngas production. Decreasing the carrier-gas flow rate further enhanced the CO₂-over-N₂ effect on syngas yield, from 9.30% (800 mL min⁻¹) to 15.57% (200 mL min⁻¹), indicating residence-time-dependent CO₂ participation. Consequently, the optimized CP under CO₂ (200 mL min⁻¹) achieved a maximum energy recovery of 48.79%, a 5.5-fold increase over SP under N₂. To conclude, food-industry residues can be sustainably upgraded into value-added syngas via CO₂-assisted catalytic pyrolysis, supporting the progress of clean energy system. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

This study was supported by the National Research Foundation of Korea (NRF) and funded by the Korean Government (MSIT) (No. RS− 2023-NR077231). Dohee Kwon also acknowledges the financial support from the Hyundai Motor Chung Mong-Koo Foundation.