3D printed hierarchical spinel monolithic catalysts for highly efficient semi-hydrogenation of acetylene

Porous monolithic catalysts with high specific surface areas, which can not only facilitate heat/mass transfer, but also help to expose active sites, are highly desired in strongly exothermic or endothermic gas–solid phase reactions. In this work, hierarchical spinel monolithic catalysts with a porous woodpile architecture were fabricated via extrusion-based three-dimensional (3D) printing (direct ink writing, DIW in brief) of aluminate-intercalated layered double hydroxide (AI-LDH) followed by low temperature calcination. The intercalation of aluminate in LDH is found crucial to tailor the M²⁺/Al³⁺ ratio, integrate LDH nanosheets into monolithic catalyst, and enable the conversion of LDH to spinel at the temperature as low as 500 °C with high specific surface areas (> 350 m²/g). The rapid mass/heat transfer resulted from the versatile 3D network at macroscale and the highly dispersed and fully exposed active sites benefited from the porous structure at microscale endow the 3D-printed Pd loaded spinel MgAl-mixed metal oxide (3D-AI-Pd/MMO) catalyst with excellent catalytic performance in semi-hydrogenation of acetylene, achieving 100% conversion at 60 °C with more than 84% ethylene selectivity.