Nanostructured Bimetallic (Cu,Ni)/SiO ₂ Catalysts for the Dehydrogenation of Ethanol to Acetaldehyde

Upgrading bioethanol to useful platform chemicals such as acetaldehyde requires the development of more effective and stable catalysts. In the nonoxidative dehydrogenation reaction, classically catalyzed by Cu nanoparticle-based catalysts operating at relatively high temperatures under an inert atmosphere, deactivation usually proceeds through carbonaceous species deposition and active phase sintering. Herein, to improve the sintering resistance and to increase the catalytic activity at low temperature, we exploit the aerosol-assisted sol–gel process to prepare mesoporous bimetallic (Cu,Ni)/SiO 2 catalysts. The peculiar preparation method ensures a thorough dispersion of the metal(s) into the silica matrix before applying calcination that triggers metal exsolution and nanoparticle formation. Keeping the total metal loading constant (7.4 wt %), we examine the influence of substituting Cu for Ni on the speciation of the metal nanoparticles. When the Ni loading is between 1.4 wt % and 3.7 wt %, Ni tends to segregate, forming Ni-enriched nanoparticles at the support surface. Cu species, instead, are partially embedded in the silica matrix. On the contrary, when the loading of Ni is low (0.1 wt %), truly alloyed nanoparticles are formed, with an intimate mixing of the two metals. This last catalyst presented a remarkable acetaldehyde (AcA) productivity of 6.0 g AcA g cat –1 h –1 and T = 673 K as compared to state-of-the-art benchmarks.