On the ultrasound-assisted preparation of Cu/SiO2 system as a selective catalyst for the conversion of biobutanol to butanal

Copper nanoparticles on silica support are cheap and effective catalysts for dehydrogenation of n-butanol, a biomass-derived building block which is increasingly used. Ultrasonically assisted Cu catalysts are prepared, characterized, and tested for the conversion of n-butanol to n-butanal. The best performance in terms of overall conversion of n-butanol and selectivity to butanal was offered by ultrasound-prepared process of the Cu nanoparticles. In conventional wet impregnation method, Cu nanoparticles on the surface of support tend to aggregate in some sort of cubic aggregates with the size of 4–5 µm and because of this, the percentage of the centers of silica (on which intermolecular dehydration reactions occur) is higher compared to Cu metallic centers (that promotes the dehydrogenation reaction). The ultrasound reduction stage used in the preparation of catalysts provides a better coverage of the catalyst surface by Cu nanoparticles that have a more uniform dimension, which offers a greater selectivity to butanal (more than 95%) and a negligible selectivity to butene.