Regulation mechanism of the specific surface area of alumina ceramic carriers with hierarchical porosity fabricated by powder bed fusion

Abstract

High-specific-surface-area ceramic catalyst carriers with hierarchical pores are conducive to catalytic reactions and filtration processes in the chemical engineering industry. However, conventional processes have difficulty manufacturing porous ceramics with extremely intricate structures. Herein, a novel method was proposed to fabricate alumina ceramic catalyst carriers with a high specific surface area (SSA) and hierarchical porosity by powder bed fusion (PBF) using micromesoporous γ-alumina as a pore-forming powder and an impregnation process of colloidal silica. Hierarchical porosity adjustable on the nm (6.03–32.37 nm), μm (24–30 μm), and mm (0.5~4.4 mm) scales was obtained by adopting and adjusting the PBF, impregnation process on preforms and postsintering process. The impacts of SiO2 content and post sintering temperatures on mechanical properties, pore characteristics, and SSA have been scientifically researched. The PBF-formed alumina ceramics possessed a crush strength of 45.88 ± 3.79 N/cm, high SSA of 56.324 m2/g, and porosity of 72.88 ± 3.37 % with multimodal distributions at 12.24 nm, 32.37 nm, and 24.18 μm. The improvement of SSA was mainly attributed to the use of micromesoporous γ-alumina and an impregnation process to reduce 3D-printing defects to obtain the hierarchical porosity (nm ~ μm scales) and required strength at a lower sintering temperature. Monolithic catalyst carriers with controllable porous structures have been manufactured to facilitate industrial recycling and improve efficiency.