Transition metal free dual functional materials (Na/Al2O3) were used for ICCU-RWGS (https://doi.org/10.1016/j.jcou.2022.102049). The authors investigated the two concentrations of CO2, including 5% and 400 ppm. The use of 400 ppm CO2 source is related to direct air capture.
The results are shown in the following figures. A few key points noted from the 400 ppm CO2 ICCU:
1) It took a longer time to capture CO2 from a 400 ppm source than 5%, which is expected.
2) When 5% CO2 was used, the generated CO concentration was around 25% in the gas stream. Regarding 400 ppm CO2, the produced CO concentration was around 20%. This is still significant, considering the extremely low concentration of CO2 in the carbon source.
3) During the 2nd stage of N2 purge, a certain amount of captured CO2 was released.
4) The authors achieved a near-practical H2/CO ratio of 3.3 using 400 ppm CO2 source for ICCU-RWGS.
The authors also compared the influence of the amount of DMFs. Compared to the use of 1 g DFM, the application of 60 g DFM caused a slightly reduce of CO2 conversion. It was suggested that axial temperature distribution was responsible, and this could be solved by reactor design.
“Figure – Concentration profiles during (a) the CO2-capture step using 400 ppm CO2 and (b, c) the conversion step using 60 g of Na/Al2O3 at 500 °C.” (https://doi.org/10.1016/j.jcou.2022.102049)