Highly Dispersed MoO3/Al2O3 Shell‐Core Composites Synthesized by CVD of Mo(CO)6 under Atmospheric Pressure

Abstract

MoO3/γ‐Al2O3 composites are synthesized by CVD under atmospheric pressure using Mo(CO)6 as the precursor and porous γ‐Al2O3 particles in a horizontal, rotating, hot‐wall reactor, which is also used for calcination in air. The composites are characterized by N2 physisorption, atomic absorption spectroscopy, X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and laser Raman spectroscopy (LRS). The synthesized samples exhibit excellent porosity, even at high Mo loadings. A much higher Mo yield is achieved when applying sublimation‐adsorption in static air instead of using flowing N2. A high degree of Mo dispersion on alumina is confirmed by XRD, LRS, and TEM; with a Mo surface density as high as 5.2 atoms nm−2, the sample is X‐ray amorphous, there are no polymeric molybdate species detectable by LRS, and the island size of the molybdate species is about 1 nm according to TEM. The XPS analysis shows that exclusively MoVI species are present on all synthesized samples. Thus, the applied rotating, hot‐wall reactor achieves efficient mixing and homogeneous deposition.