Enhancing CO2-to-solid-carbon conversion via flow optimization and water removal in a coupled methanation–reforming reactor

Abstract

Continuous catalytic processes that convert CO₂ into solid carbon offer a promising route for carbon-negative chemical production. In this work, we investigate coupled CO₂ methanation–dry reforming–carbon capture under new operating conditions to significantly improve the carbon capture efficiency. Using the same experimental apparatus as our prior study, we varied the total gas flow rate and implemented a water trap in the carbon-capture unit. Their effects on the reactant conversion, product gas composition, and solid carbon yield were measured. Key results show that the optimized flow conditions (intermediate residence time) and water-trap integration lead to solid carbon production, with the carbon yield increasing from 20% for the original configuration to 60%. The CO₂ and CH₄ conversions remained high (with a stable H₂/CO ratio of 1.6 in the syngas product), indicating that enhanced carbon capture was achieved without sacrificing the syngas generation performance. Characterization of the captured carbon by electron microscopy and Raman spectroscopy revealed the formation of abundant carbon nanotubes/fibers with improved crystallinity under the new conditions. Therefore, the coupled methanation-reforming reactor with flow optimization affords improved control and efficiency for CO₂-to-solid-carbon conversion, enabling the effective sequestration of CO₂ as a stable solid.