Study on K-modified Ca-based dual-functional materials for carbon capture and in-situ methane dry reforming

Integrated carbon capture and in-situ methane dry reforming (ICCU-DRM) is a promising technology for chemical looping transformation, this process involves the sequential switching of feedstocks within a single reactor, allowing CO₂ capture to occur before methane dry reforming without direct CO₂-CH₄ contact. However, a significant challenge in the ICCU-DRM process is the disparity between the optimal temperatures required for carbon capture and dry reforming, with the latter necessitating considerably higher temperatures. This could lead to substantial CO₂ losses when the reaction temperature is elevated to the optimal level for dry reforming. To address this issue and improve CO₂ conversion efficiency, this study explores K doping in synthesizing a dual-functional material, NiCa_1.6K_0.4@Al₂O₃, through extrusion-spheronization. The synthesized material exhibits a stable pore structure and a large internal surface area, crucial for enhancing CO₂ capture. The optimum temperature for DRM is around 800 °C. Notably, the formation of K₂Ca(CO₃)₂ during the calcination of NiCa_1.6K_0.4@Al₂O₃, with a thermal decomposition temperature of approximately 800 °C, plays a crucial role in minimizing CO₂ release during the heating process, thereby significantly improving the CO₂ conversion. To evaluate the impact of K doping on the material, the samples were subjected to carbon capture at 650 °C and dry reforming of methane at 750 °C. The results showed that the CO₂ conversion rate of NiCa_1.6K_0.4@Al₂O₃ reached 52.8 %, compared to only 18.9 % for NiCa₂@Al₂O₃ under the same conditions. Moreover, this study also investigates the impact of carbon capture temperature, dry reforming temperature, and catalytic metal loading on the performance of the ICCU-DRM process.