Hydrothermal reduction of CO2 captured as NaHCO3 into formate with metal reductants and catalysts

The hydrothermal reduction of CO2 captured in aqueous solutions using metal reductants is a promising novel approach that achieves high yields of conversion and high selectivity, but it presents the limitation of the high temperatures needed for the reaction to take place. In this work, experiments combining several reductant metals (Zn, Al and Fe), catalysts (Pd/C, Ni, Cu, Fe2O3 and Fe3O4) and temperatures (200, 250 and 300 oC) were per-formed to optimize the process at milder temperatures. Using Al as reductant and Pd/C as catalyst, yields as high as 38 % were obtained at 200oC, compared with the highest yield (57 %) observed at 250 oC. Thus a significant temperature reduction can be achieved using a suitable combination of reductant and catalyst. Using this re-action system, Pd/C as catalyst and Al as reductant, an extensive set of experiments at different times and temperatures were performed in order to determine the kinetics of the process and correlate them to a mathe-matical model of the process. The model correctly reproduces the experimental data with average errors lower than 5.9 %. These results demonstrate the feasibility of lower the operating temperature while maintaining the performance, when using an adequate combination of catalyst and reductant.

Automated summary

The hydrothermal reduction of CO2 captured in aqueous solutions using metal reductants is a promising approach, but it requires high temperatures. This research optimized the process by combining different reductant metals, catalysts, and temperatures to achieve high yields at milder temperatures. By using Al as the reductant and Pd/C as the catalyst, the yield at 200℃ reached 38%, compared to 57% at 250℃. Mathematical modeling accurately reproduced the experimental data, demonstrating the feasibility of lower operating temperatures with the right catalyst and reductant combination.