Cu–Ni/SiO₂ Catalysts for Dehydrogenation Reaction of Secondary Butyl Alcohol

Abstract

Cu–Ni/SiO₂ catalysts were prepared by coprecipitation method and used in the dehydrogenation reaction of secondary butyl alcohol to methyl ethyl ketone (MEK). The crystal structure, reduction characteristics, element valence state and dispersibility of the catalysts were investigated using X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H₂-TPR), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray Auger electron spectroscopy (XAES) and high resolution transmission electron microscopy (HRTEM). The role of Ni component in the dehydrogenation reaction of secondary butyl alcohol was analyzed. The results showed that the conversion of secondary butyl alcohol increased to over 99% when using the Cu–Ni/SiO₂ catalyst. The addition of nickel component to Cu/SiO₂ inhibited the agglomeration of copper nanoparticles. The interaction between copper and nickel was strengthened due to the formation of the Cu–Ni compound. This resulted in change to the valence state and improved the dispersion of copper species on the catalyst surface. The Cu⁺/(Cu⁺ + Cu⁰) ratio increased with the addition of nickel component to Cu/SiO₂, which may be responsible for the enhancement of the secondary butyl alcohol conversion. However, the addition of the nickel component increased the reduction temperature of the catalysts and deteriorated their reduction characteristics, which leads to insufficient reduction, resulting in a high content of Cu⁺ species remaining in the catalyst. Therefore, side reactions can occur, which are detrimental to the selectivity and yield of MEK. The selectivity to MEK can reach 98% with the Cu/SiO₂ catalyst, whereas that for the Cu–Ni/SiO₂ catalyst was 97%.