Promotional effect of Ca on La1-xCaxFeO3 perovskites for ammonia production via steam catalytic gasification of microalgae

Ammonia (NH3) production from nitrogen-rich biomass gasification offers a sustainable route to high-efficiency conversion and storage of renewable energy. La1-xCaxFeO3 perovskites (x = 0, 0.1, 0.2 and 0.3) are proposed as potential catalysts to promote NH3 selectivity. The catalytic performance of La1-xCaxFeO3 perovskites in terms of activity and stability was investigated for ammonia production via steam catalytic gasification of microalgae. The results indicate that Ca substitution facilitates the generation of Fe4+ and oxygen vacancies. Oxygen vacancies are able to supply sufficient active sites for H-O bond breakage in steam, so that the lattice oxygen can be supplemented by O derived from the H-O bond breaking to maintain the structure of perovskites, and two H atoms combine to generate a significant amount of H2. An appropriate amount of Ca doping (x = 0.1, 0.2) enhances the hydrogenation of char-N, the deamination of tar-N, and the conversion of HCN, therefore promoting the NH3 selectivity. However, excessive Ca doping amount (x = 0.3) decreases the NH3 production. La0.8Ca0.2FeO3 perovskite possesses the maximum conversion of fuel-N into NH3 (62.2 %). Moreover, La0.8Ca0.2FeO3 perovskite shows superior stability and excellent resistance to coke formation during long-term cycling.