On the scaling-up of 3D-printed metallic POCS structured catalysts membrane reactors

This work reports the first experimental demonstration of a scaled-up multi-membrane reactor for ammonia synthesis, integrating four tubular carbon molecular sieve membranes (CMSMs) with two 3D-printed metallic Periodic Open Cellular Structure (POCS) supports of Gyroid and Body-Centred Cubic (BCC) geometry, manufactured in Inconel 625 by Laser Powder Bed Fusion and washcoated with a Ru-based catalyst via a scaled-up dip-spin coating procedure. The coating protocol transferred to both topologies at the larger scale without modification, with optical microscopy confirming uniform, crack-free coverage.. Novolac-based CMSM carbonized at 550 °C were characterised by organic elemental analysis, XPS, and Raman spectroscopy, confirming a defect-rich, turbostratic sp 2 carbon matrix with microporous architecture. Baseline testing in the conventional reactor over 350–450 °C and 20–40 bar(g) demonstrated that Gyroid and BCC configurations deliver virtually identical catalytic performance, reflecting the dominance of reaction kinetics and thermodynamics over geometry-dependent transport resistances. Upon membrane integration, this geometry-independence was preserved, and the membrane consistently enhanced NH 3 production rates across all operating conditions. Beyond-equilibrium operation, with H 2 conversion and NH 3 yield reproducibly exceeding thermodynamic limits, was achieved exclusively at low wight hourly space velocity (WHSV) and a sweep ratio (SW) of 4: H 2 conversion surpassed equilibrium by 30% at 400 °C and 110% at 450 °C, with NH 3 yield gains of 65% and 170% over the conventional reactor. Scaling from one to four membranes yielded a membrane-area-normalised productivity improvement of up to 424% at 350 °C and 40 bar(g), providing a strong foundation for continued scale-up of membrane reactors for ammonia synthesis.