Enhanced thermal management in CO2 methanation using spiral-structured catalysts: a comparative study with honeycomb, monolith, and packed-bed systems

Abstract

This study presents a comprehensive evaluation of structured catalyst designs for CO₂ methanation under high-throughput conditions, focusing on spiral-structured catalysts in comparison with metallic honeycomb, cordierite honeycomb, and packed-bed systems. Experimental results revealed that the spiral-structured catalyst consistently exhibited the highest CO₂ conversion and CH₄ selectivity across a wide range of gas flow rates (1–6 L min⁻¹), clearly outperforming conventional catalyst geometries. Thermal measurements demonstrated that the spiral catalyst effectively minimized temperature deviations (ΔT) from the set reactor temperature, significantly suppressing local hotspots and enhancing operational stability. Despite its inherently lower catalyst density due to a highly porous structure, the spiral catalyst maintained the highest catalytic activity normalized by geometric surface area (GSA), reflecting its superior surface utilization efficiency. To quantitatively assess mass-transfer contributions, dimensionless parameters such as Reynolds (Re), Schmidt (Sc), and Sherwood (Sh) numbers were analyzed. All catalyst structures exhibited slopes around 0.7 in plots of ln(Sh) against ln(Re·Sc^1/3), confirming turbulent mass-transfer conditions. The spiral catalyst consistently showed higher Sherwood numbers, indicating improved mass transfer. CFD simulations further confirmed that the spiral geometry induces strong swirl flow, enhances radial mixing, and markedly reduces gas-film boundary-layer thickness, directly facilitating reactant accessibility to catalyst active sites. Collectively, these findings demonstrate that the spiral-structured catalyst integrates superior thermal management with enhanced mass-transfer properties, ensuring stable, efficient, and high-performance CO₂ methanation even under industrially relevant high-throughput conditions.