Structured Alumina Substrates for Environmental Catalysis Produced by Stereolithography

Abstract

Modern catalysts for internal combustion engine applications are traditionally constituted by honeycomb substrates on which a coating of the catalytically active phase is applied. Due to the laminar flow of the gases passing through their straight channels, these structures present low heat and mass transfer, thus leading to relatively large catalyst sizes to compensate for the low catalytic activity per unit of volume. Better conversion efficiency can be achieved if three-dimensional periodic structures are employed, because of the resulting gases’ tortuous paths. Furthermore, the increased catalytic activity implies a reduction in the overall catalyst volume, which can translate to a decreased usage of precious metals as active phase. By exploiting the ceramic Stereolithography technique (i.e., SLA) it is nowadays possible to accurately 3D print complex alumina-based lattices to be used as ceramic substrates for catalysis. In this work, closed-walls lattices consisting of a rotated cubic cell of 2 mm dimensions were designed, 3D printed via SLA and finally washcoated with V2O5-WO3-TiO2. The samples were tested for the selective catalytic reduction of NO by NH3 in a heated quartz glass reactor and the performance of the innovative 3D-printed substrate was compared with the catalytic efficiency of the conventional cordierite honeycombs.

Towards unconstrained catalyst shaping: high accuracy DLP printing of porous γ-Al2O3-based catalysts

“…The consolidation of the ceramic particles in the 3D structure is usually enabled via thermal sintering at temperatures exceeding 1000 °C, which is nowadays a widely accepted method to ensure suitable mechanical properties of the final ceramic bodies. 23 Although enormous progress in 3D printing of non-porous materials such as alumina, 13,24,25 titania 26 and zirconia 27,28 has been made in the recent five years, the same approach is not applicable to obtain porous pellets relevant for catalysis, because thermal sintering destroys the internal porosity of the catalyst material, reducing dramatically the specific surface area. 29 Pyrolysis at a lower temperature is an option that preserves the catalyst porosity; 30 however, the presence of carbon deposits on the final structure can be detrimental for catalytic applications.…”

“…Then, the digital design is sliced in several bidimensional layers and modified in numerical instructions (G-code) that the printer can elaborate. 13 Finally, the 3D printer builds the objects in a layer-by-layer fashion. Therefore, additive manufacturing allows the digital control of the catalyst architectures and fine tuning via topology optimization once the physics of the chemical system is known.…”

Additive manufacturing of advanced ceramics by digital light processing: equipment, slurry, and 3D printing

“…catalytic applications [88][89][90][91][92], ceramic core for investment casting [93][94][95][96][97], dental restoration [6,7,98,99], solid oxide fuel [3,4,100,101], heat exchanger [75,[102][103][104], among others. Figure 5 illustrates some of these potential applications published in related articles.…”