Washcoated additively manufactured TPMS structures as catalytic converters for engines: A proof of concept

Transitioning towards cleaner combustion technologies requires catalytic converters with high conversion efficiency, thermal stability, and low pressure drop. This proof-of-concept study evaluated additively manufactured triply periodic minimal surface (TPMS) architectures as catalytic carriers for exhaust-gas aftertreatment. The investigated set comprised eight stainless-steel TPMS monoliths based on Schwarz–diamond, gyroid, and Schwarz–primitive geometries in various orientations and a straight-channel reference monolith. All the monoliths were fabricated by laser powder bed fusion (PBF-LB/M), washcoated with 2 wt% Pt/γ-Al$_2$O$_3$, and tested using exhaust gas from a compressed natural gas engine. The carriers exhibited accurate external dimensions, continuous washcoat coverage, and low washcoat loss in adhesion tests. The TPMS architectures provided specific surface areas up to 1.65 mm$^{−1}$, compared with 0.82 mm$^{−1}$ for the reference, while several configurations maintained pressure drops per unit length comparable to or lower than the reference monolith. The unrotated Schwarz–diamond structure with a 5 mm unit cell achieved the highest CO conversion of approximately 99 % and the highest washcoat-loading-normalised CO conversion, although this was accompanied by a comparatively high pressure drop. ... mehrIn contrast, the 10 mm gyroid configuration provided one of the most favourable conversion–pressure-drop balances. Under stoichiometric conditions (air–fuel equivalence ratio, λ=1), the two highest-conversion TPMS configurations exceeded 90 % CO conversion, with simultaneous methane (CH$_4$) conversion and reduction of nitrogen oxides (NO$_x$) observed across the investigated TPMS configurations. Overall, the results indicate that TPMS topology, unit cell orientation, and specific surface area jointly affect catalyst utilisation and hydrodynamic resistance, highlighting the potential of additively manufactured TPMS catalyst carriers for advanced emission-control applications.