Chemical looping gasification of pine wood over layer-confined Ni: Loading-packing synergy and cyclic stability

Amid China's dual-carbon (2030/2060) agenda, chemical looping gasification (CLG) is a vital pathway to tunable, low-emission syngas. This work pursues two complementary objectives. First, develop Ni-based oxygen carriers with interlayer-confined Ni in a 2D lamellar structure and examine how such confinement affects redox stability and syngas selectivity. Second, we optimize the steam-to-carbon ratio to establish a consistent steam-assisted baseline and then elucidate the interplay between Ni loading and bed inventory under steam-assisted biomass CLG, identifying operating conditions that balance instantaneous productivity and cyclic stability. Under optimized steam conditions, the layer-confined Ni–montmorillonite oxygen carrier features open interlamellar channels and finely dispersed Ni. This architecture maintains Ni dispersion and channel continuity during cycling, thereby mitigating sintering, coking, and irreversible phase transformations. On this basis, we systematically vary Ni loading (15–25 wt%) and bed inventory (0.5–2.0 g) to map their coupled effects on gas distribution and cyclic behavior. We find that higher instantaneous activity does not guarantee better durability: 25-Ni (1.0 g) produces higher initial syngas (1196 mL g−1) but drops to 1047 mL g−1 after 20 cycles (≈12.4%), whereas 20-Ni (1.5 g) maintains a similarly high yield (1218 → 1151 mL g−1; ≈5.5%) with a more H2-rich syngas and lower CH4. These trends highlight a practical loading–packing regime in which moderate Ni loading combined with appropriate bed packing matches site accessibility with bed-scale heat and mass transfer. Overall, we propose and validate a layer-confined Ni on 2D lamellae design and its associated loading–packing strategy, providing guidance for achieving selective syngas production with improved cyclic stability in biomass CLG.