Corrosion Mechanisms of Stainless Steels in SCWG of Biomass: Influence of Feedstock Chemistry and Catalysts - CANCELLED (C2026-00248)
CANCELLED
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Supercritical Water Gasification (SCWG) offers a promising thermochemical pathway for hydrogen production from wet and lignocellulosic biomass. However, the extreme conditions inherent to SCWG—high temperatures and pressures, aggressive byproducts, and reducing environments pose severe corrosion challenges to reactor materials. In this study, we investigate the corrosion behavior of selected stainless steels and Ni-based alloys under various SCWG conditions using model compounds (cellulose, xylan, and lignin) and real biomass (pinewood sawdust, corn stalk), with and without alkaline catalysts such as NaOH. Experimental findings reveal that corrosion is significantly influenced by the synergistic effects of biomass-derived species, catalytic activity, and gas-phase reactions. Notably, Alloy 625, typically resistant to supercritical water, undergoes accelerated degradation under SCWG due to the presence of phenolic intermediates and reducing gases (H₂ and CO), which destabilize protective Cr₂O₃ layers. Lignin-rich feedstocks induce pronounced sulfidation via H₂S generation, while alkaline catalysts modulate corrosion by altering gas speciation and promoting protective carbonaceous deposits. This work provides mechanistic insights into SCWG corrosion pathways, highlighting the critical roles of feedstock composition, catalyst type, and evolving gas environments. The outcomes underscore the need for tailored materials selection and corrosion mitigation strategies to ensure the long-term viability of SCWG reactors for sustainable hydrogen production.
