Probing the Selectivity of Acidic Sites in the Oxidative Catalysis of Ethanol: Al x Fe 2 − x (MoO 4 ) 3

ABSTRACT We report the catalytic reactions of ethanol under oxidizing conditions using ball‐milled Al x Fe 2− x (MoO 4 ) 3 (0.25⩽ x Al ⩽1.0) samples of similar particle sizes and surface areas. Characteristic of this series is the increased Mo:(Al+Fe) ratio of 1.7:1.0 in surface near volumes of the bulk. Acetaldehyde (AcH) results from the oxidative dehydrogenation of ethanol as the main product. The selectivity of AcH decreases by about 20% around 250°C in favor of diethyl ether (DEE), regardless of the Al 3+ content. This suggests that the Lewis acidic Al 3+ cations act on the general bulk structure and, in particular, influence the lattice oxygen activity of Mo–O–Fe redox centers. At high conversion rates at elevated temperatures, the overoxidation of ethanol to CO x is reduced compared to Fe 2 (MoO 4 ) 3 in favor of the formation of ethene (dehydration of ethanol). Beyond reporting on the catalytic reactions of these compounds, we provide insights into defect sites in subsurface volumes through methods for characterizing solid‐state materials such as X‐ray powder diffraction, SEM‐EDX, 57 Fe Mössbauer spectroscopy, and thermal analysis.