Fluidized Bed CVD of [5]Al-rich amorphous alumina on powders for catalysis applications

Producing alumina catalysts containing high amounts of penta-coordinated aluminum sites ([5]Al) is of main interest to develop a green production of olefins from biomass. Inspired from an original process developed on planar substrates at low pressure, a Fluidized Bed Chemical Vapor Deposition (CVD) process coupled to a DLI (Direct Liquid Injection) system has been studied at atmospheric pressure to deposit amorphous alumina on soluble NaCl powders, using dimethyl aluminum isopropoxide (DMAI) as precursor. A set of experiments has been performed at 310°C, showing the good reproducibility of the deposition process in terms of deposit morphology, mass and chemical composition. Nuclear Magnetic Resonance of aluminum-27 probing the structure at atomic scale of the deposit indicates the presence of high contents of penta-coordinated aluminum, as it was the case on planar substrates. This demonstrates that this DLI-CVD route from DMAI is robust. Coupled with a fluidized bed, it could lead to massive production of high specific surface area amorphous alumina with high content of penta-coordinated aluminum environments