Improving the catalytic performance of Co/BaCeO3 catalyst for ammonia synthesis by Y-modification of the perovskite-type support†

Abstract

Y-modified perovskite-type oxides BaCe_1−xY_xO_3−δ (x = 0–0.30) were synthesised and used as supports for cobalt catalysts. The influence of yttrium content on the properties of the support and catalyst performance in the ammonia synthesis reaction was examined using PXRD, STEM-EDX, and sorption techniques (N₂ physisorption, H₂-TPD, CO₂-TPD). The studies revealed that the incorporation of a small amount of yttrium into barium cerate (up to 10 mol%) increased specific surface area and basicity. The catalyst testing under conditions close to the industrial ones (T = 400–470 °C, p = 6.3 MPa, H₂/N₂ = 3) showed that the most active catalyst was deposited on a support containing 10 mol% Y. The NH₃ synthesis reaction rate was 15–20% higher than that of the undoped Co/BaCeO₃ catalyst. The activity of the catalysts decreased with further increasing Y content in the support (up to 30 mol%). However, all the studied Co/BaCe_1−xY_xO_3−δ catalysts exhibited excellent thermal stability, over 240 h of operation. The particularly beneficial properties of the catalyst containing 10 mol% of Y were associated with the highest basicity of the support surface, favourable adsorption properties (suitable proportion of weakly and strongly hydrogen-binding sites), and preferred size of cobalt particles (60 nm). The Co/BaCe_0.90Y_0.10O_3−δ catalyst showed better ammonia synthesis performance compared to the commercial iron catalyst (ZA-5), giving prospects for process reorganisation towards energy-efficient ammonia production.