Performance of Reverse Water Gas Shift on Coprecipitated and C-Templated BaFe-Hexaaluminate: The Effect of Fe Loading, Texture, and Promotion with K

The effects of chemical composition, texture, and promotion with potassium of coprecipitated and carbon-templated BaFe-hexaaluminate catalysts on their performance in reverse water gas shift (RWGS) reaction were studied in a fixed-bed catalytic reactor at T=350 °C, p=20 bar, H₂: CO₂ of 3. The methane selectivity at these conditions did not exceed 0.1 %. It was established that the rate of RWGS is strongly affected by the catalysts iron content gradually increasing up to 45 % Fe. Decreasing the catalyst nanocrystals platelets size (diameter/thickness) from 500–800/50–80 nm to 150–250/30–50 nm (SEM) by implementing the CT increased the surface area and the rates of reaction. Modeling of the redox cycle of RWGS by CO₂-TPD, TP reaction and TP reduction indicated that H₂ reduction is needed for regeneration of active sites Fe²⁺ ions associated with oxygen vacancies. Potassium displayed a strong promotion effect on the activity of Ba−Fe-hexaaluminates. At optimal K content of 6 wt %, the RWGS rates increased by a factor of 12–15 without changing the TOF number. This was attributed to increasing concentration of active sites due to the reduction of Fe³⁺ ions (XPS).