CaCO3 hydrogenation to CH4 using natural limestone and a Ni-based catalyst for CCU applications

Carbon capture and utilization (CCU) has emerged as a promising strategy for mitigating CO 2 emissions while producing valuable chemicals. However, conventional CCU relies on separate capture, purification, and conversion steps. Integrated carbon capture and utilization (ICCU) processes enables the direct conversion of CO 2 from diluted streams in a single unit. In this context, most ICCU approaches have focused on the development of synthetic dual functional materials (DFM), which often involve laborious synthesis routes, high costs and limited long-term stability. In this work, commercially available materials, such as natural limestone and Ni-based catalyst, have been evaluated as an alternative for CCU applications. The hydrogenation of CaCO 3 was investigated to determine the operating conditions that maximize CH 4 production. The influence of temperature, pressure, gas residence time and mass ratio CaCO 3 /catalyst were evaluated to elucidate the governing reaction pathways and thermodynamic limitations. An optimal temperature window between 500–550 ºC was identified, and near-equilibrium CH 4 concentrations were achieved under adequate residence times. Notably, this work represents the first demonstration of CaCO 3 hydrogenation to CH 4 at early-stage TRL-3 reactor, achieving a CH 4 concentration of 9.46 vol% at 8 bar and 550 ºC, in line with equilibrium predictions. The practical application of the proposed CCU route was demonstrated through its integration into a sorption-enhanced methanation (SEM) process over 20 cycles, achieving an overall carbon-to-methane yield of 100% with a remarkable cyclic stability. These findings highlight the potential of commercially available materials for efficient and scalable CH 4 production in CCU applications.