A Multi-Scale Study of 3d Printed Co-Al2o3 Catalyst Monoliths Versus Spheres

Abstract

This study demonstrates the characteristics of two model packing geometries: 3D printed catalyst monoliths on the one hand, and their conventional counterparts, packed beds of spheres, on the other. Cobalt deposited on alumina is selected as a convenient model system for this work, due to its wide spread use in many catalytic reactions. 3D printed constructs were produced from alumina powder impregnated with cobalt nitrate while the alumina spheres were directly impregnated with the same cobalt nitrate precursor. The form of the catalyst, the impregnation process, as well as the thermal history, were found to have a significant effect on the resulting cobalt phases. Probing the catalyst bodies in situ by XRD-CT indicated that the level of dispersion of identified Co phases (Co3O4 reduced to CoO) across the support is maintained under reduction conditions. However, the CoO average crystallite sizes were in the range of 10 - 20 nm for the spheres, while the CoO average crystallite size was observed to be smaller and in the range of 5 - 12 nm at the end of the reduction and temperature ramp for the 3D printed catalyst. CFD modelling was carried out to assess the effect of the catalyst geometry on the flow patterns by comparing pressure drop and residence time distribution. Finally, the activity of both Cobalt-based catalyst geometries was assessed under model multiphase (selective oxidation) reaction conditions showing the desired 3D printed monolithic geometries can offer distinct advantages to the reactor design. The velocity profiles through the novel 3D printed catalyst/reactor configurations can be tuned to allow for higher reactor performance (increased conversion, yield and TOF).

Keywords: 3D printed catalyst monoliths, in situ synchrotron XRD-CT, Computational fluid dynamics (CFD), selective oxidation reaction, multiphase reaction, packed bed reactor