Activated triply periodic minimal surfaces (TPMS) gyroid supports for efficient ammonia synthesis in membrane-integrated reactors

Ammonia is an essential chemical widely used in industry, with its production dominated by the highly energy-intensive Haber-Bosch process. Membrane reactor technology offers a promising alternative by integrating reaction and selective product separation, thereby enabling higher process efficiencies and milder operating conditions. In this work, we investigate a new membrane reactor composed of a carbon membrane immersed in an Activated Triply Periodic Minimal Surface (TPMS) gyroid support uniformly coated with a Ru-based catalytic layer. Different operating conditions have been investigated; The most favourable baseline conditions were identified at the lowest WHSV (715 mLn g_cat−1 h−1), and with an under-stoichiometric H₂:N₂ feed ratio of 2:1, reflecting both the proximity to thermodynamic equilibrium and the beneficial impact of reduced hydrogen partial pressure on Ru-based catalysis.At 250 °C and 40 bar, increasing the sweep gas to feed flow ratio (SW) to 10 led NH₃ production rate enhancements of approximately 43 % and corresponding NH₃ yield gains of 15 %, with an NH₃ recovery factor of 84 %. At lower pressure (30 bar) and higher temperatures (350–450 °C), the membrane reactor still enhanced NH₃ production rate at reduced sweep ratios, with gains of about 1-20 % at SW = 1 and 17–41 % at SW = 4 relative to the SCR. However, the NH₃ recovery factor dropped to 64-70 % for SW = 1 and 41-66 % for SW of 4, compared with 87-95 % at 40 bar. This behaviour indicates a clear trade-off between productivity and product recovery as pressure and sweep ratio are adjusted. At 450 °C and 10-40 bar, with a SW = 4, H₂ conversion exceeded the equilibrium value by approximately 15–30 %, and the conversion achieved at 400 °C in the SCR was already attained at 300 °C in the SCMR. At 400 °C and 40 bar with SW = 4, H₂ conversion, NH₃ production rate, and NH₃ yield increased by 83.4 %, 76.9 %, and 53.4 %, respectively, compared to the structured reactor. Overall, these results provide a clear proof of concept for the application of structured membrane reactors to ammonia synthesis, demonstrating that an appropriate combination of structured Ru-based catalysts and carbon membrane integration can deliver enhanced efficiency and equilibrium shifting under milder operating conditions, and offering a solid basis for future scale-up and process optimization studies.