3D-Printed Fe-doped silicon carbide monolithic catalysts for wet peroxide oxidation processes

Abstract

The catalyst stability has become a key issue for wet peroxide oxidation (CWPO) processes. Herein, an alternative method for the manufacturing of iron (Fe) catalysts by using three-dimensional (3D) printing techniques is proposed to enhance the Fe immobilization, where these metallic nanoparticles are part of a printable aqueous silicon carbide (SiC)-based ink. Cylindrical Fe/SiC monoliths (D ∼ 13 mm, H ∼ 4.5 mm, 74 squared cells cm−2) are manufactured by direct ink writing (Robocasting) and further treatment up to 1500 °C into a spark plasma sintering (SPS) furnace to assure a certain mechanical integrity. It was found that the increasing SPS temperature progressively decreases the porosity -or increases the apparent density- of the printed struts, lowering the accessibility of reactants to the Fe sites but improving the catalyst mechanical strength and leaching resistance. 3D Fe/SiC monoliths treated at 1200 °C arise as robust catalysts for CWPO processes due to the combination of good catalytic activity, highly- efficient H2O2 decomposition, long-term stability and excellent mechanical strength. A simple potential kinetic model is proposed, capable of describing the phenol disappearance, TOC removal and H2O2 consumption. The results of this study point out a new approach for the conformation by Robocasting of metal-based catalysts in suitable morphological 3D-structures for scaling-up reactions.