Vanadium As a Potential Membrane Material for Carbon Capture: Effects of Minor Flue Gas Species

Vanadium and its surface oxides were studied as a potential nitrogen-selective membrane material for indirect carbon capture from coal or natural gas power plants. The effects of minor flue gas components (SO₂, NO, NO₂, H₂O, and O₂) on vanadium at 500-600 °C were investigated by thermochemical exposure in combination with X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and in situ X-ray diffraction (XRD). The results showed that SO₂, NO, and NO₂ are unlikely to have adsorbed on the surface vanadium oxides at 600 °C after exposure for up to 10 h, although NO and NO₂ may have exhibited oxidizing effects (e.g., exposure to 250 ppmv NO/N₂ resulted in an 2.4 times increase in surface V₂O₅ compared to exposure to just N₂). We hypothesize that decomposition of surface vanadium oxides and diffusion of surface oxygen into the metal bulk are both important mechanisms affecting the composition and morphology of the vanadium membrane. The results and hypothesis suggest that the carbon capture performance of the vanadium membrane can potentially be strengthened by material and process improvements such as alloying, operating temperature reduction, and flue gas treatment.