Chemical etching optimization of 3D printed α-Al2O3 monoliths to enhance the catalytic applications

Direct Ink Writing has been demonstrated to be a promising route to produce ceramic catalysts with complex geometries and enhanced catalytic performances. To increase the catalytic performances, chemical etching can be conducted to get an interconnected and hierarchical porous structure, to increase the surface area and the contact time of the reactants. In this work, DIW alpha (α)-Al2O3 catalysts were chemically etched with hydrofluoric acid (HF). Several combinations of acid concentrations and etching times were studied to find the optimal etching condition. For HF concentration of 5, 20 and 40wt. %, the optimal etching time was 48, 24 and 5h, respectively, being 40wt. % the concentration that shows the greatest increase of surface porosity (of around 5%). HF etching can produce an interconnected porosity on 3DP α-Al2O3, but it does not yield improvement in catalytic performances when the content of fluor (F) is higher than 10 at. % since it produces parasite reactions.