Rich H2 catalytic oxidation as a novel methodology for the evaluation of mass transport properties of 3D printed catalyst supports

In this work, we propose a novel methodology for the evaluation of the external mass transfer properties of 3D printed catalyst supports. This protocol relies on the use of a lab scale SLA 3D printer with a resin characterized by a high heat deflection temperature (HDT) for the manufacturing of samples at a lower price and with higher accuracy than equivalent metallic 3D printed structures. Periodic open cellular structure (POCS) samples with Tetrakaidecahedron unit cells (TKKD) were 3D printed and catalytically activated by depositing a 3% Pd/CeO2 washcoat by spin-coating. The washcoat was then consolidated with a two-step heat treatment composed by in-situ calcination in N2 and reduction in N2/H2 stream. Catalytic tests of rich H2 combustion showed the possibility to reach the external mass transfer control at temperatures below the resin HDT. Sherwood numbers were eventually estimated from the oxygen conversions under full external mass transfer control assuming a PFR behaviour. To validate the methodology, 3D printed replicas of open cell foams were also tested, and the results were successfully compared against a well-established literature correlation. Moreover, a one-to-one comparison was performed between the Sherwood numbers of a resin 3D printed structure, tested with the proposed methodology, and a metallic 3D printed structure, tested with the conventional CO oxidation approach. The two methods lead to superimposed results, thus providing the experimental evidence of the equivalence of the two methodologies for the evaluation of the external mass transport properties of complex catalyst substrates.