Application of fumed silica supported copper catalysts in the dehydrogenation of sec-butanol to methyl ethyl ketone

Cu/SiO₂ catalysts were prepared by impregnation method using fumed silica as a carrier. The performances of these catalysts in the dehydrogenation reaction of sec-butanol (SBA) to methyl ethyl ketone (MEK) were tested and compared with those of the catalysts prepared by ammonia evaporation method. Some physical and chemical properties of the catalysts were characterized and the catalytic mechanism was revealed. The results showed that compared with the catalysts prepared by the ammonia evaporation method, the catalysts prepared by fumed silica impregnation method have some reticulated structures, possessing larger specific surface areas, stronger alkalinity, higher dispersion and lower reduction temperature. Therefore, the latter catalysts have higher (Cu⁰ + Cu⁺)/Cu²⁺ and more Cu⁰ species after being reduced, which leads to a better catalytic performance. The conversion of sec-butanol, the selectivity and the yield of methyl ethyl ketone by using the Cu/SiO₂ catalysts prepared by the impregnation method are up to 98.3%, 99.9% and 98.2% at an actual copper loading of 2.38% (w%). DFT calculations showed that the reaction path of the dehydrogenation process of sec-butanol over copper-based catalysts is –O–H breaking to form alkoxyls, followed by the dehydrogenation of α-C in the alkoxyls, where the former process is the decisive speed step of the reaction.