(Ni,Cu) and Cu supported over alumina for ethanol dehydrogenation: Effect of preparation, activation, and operando studies

(Cu,Ni)/Al 2 O 3 catalysts were prepared by different synthetic routes and characterized using several techniques. The effect of H₂ pretreatment on catalytic performance was examined using steady-state and operando tests and compared with a commercial reference. The prereduced bimetallic catalyst prepared via SCS achieved the highest acetaldehyde yield (75 % at 573 K). Pre-reduction enhanced activity and selectivity at low temperatures without altering high-temperature behavior, even though it did not strongly affect stability in short contact time experiments. Operando studies showed that, upon acetaldehyde production, acetate species are formed on Al³⁺ or on exposed reduced transition-metal surfaces, resulting in distinct acetate populations. The interaction of acetate with Cu 0 appears to be weaker when nickel is introduced, particularly with the SCS route. Under operando conditions, activity generally declines at the maximum tested temperature, where acetate species reach their maximum peak intensity; those species remain stable at the surface even upon purging at high temperature. • Catalysts prepared by solution combustion synthesis increase acetaldehyde production. • Prereduction increases acetaldehyde yield at low temperature. • Operando IR experiments reveal that acetate begins to form on Al 3+ or on exposed Cu. • Introducing Ni reduces the interaction between acetate and copper in SCS. • Activity decreases when the acetate species reach maximum intensity.