Impact of Co impregnation on 3D printed alumina supports for Fischer-Tropsch synthesis

3D printing of catalyst has made a significant headway the past decade. Very often metal species on 3D printed supports are being used in catalysis. However, there is no standardized method of impregnation of 3D printed structures. In this work, the impact of the step in the production process where the impregnation is done was studied. Cobalt on alumina catalyst structures were synthesized using direct ink writing (DIW), characterized and tested in Fischer-Tropsch synthesis. Three different impregnation methods were tested (A) incipient wetness impregnation of the structure after printing (B) adding the metal salt precursor to the printing recipe and (C) impregnation of the alumina powder before printing. The catalysts exhibited significant differences in final properties, including pore volume in the fibers of the structure, cobalt nanoparticle size and metal-support interaction. When using the catalysts in Fischer-Tropsch synthesis, the activity of the catalyst impregnated after printing, was more than double the one with the metal salt in the print paste. The difference in conversion showed a clear correlation with the reducibility of the metal species measured with H2-TPR.