Facile synthesis of supported RuO2·xH2O nanoparticles on Co–Al hydrotalcite for the catalytic oxidation of alcohol: effect of temperature pretreatment

Abstract

RuO₂·xH₂O supported on a CoAl-LDH catalyst was synthesized by the co-precipitation (CP) method and the deposition–precipitation (DP) method for the selective oxidation of alcohols. The catalyst prepared by the CP method exhibited higher activity compared with that obtained by the DP method due to stronger interaction between RuO₂ and the CoAl-LDH support as well as the slightly smaller particle size of the RuO₂ nanoparticles. The influence of the temperature pretreatment on catalytic performance was then investigated. Among the catalysts pretreated at different temperature, RuO₂/CoAl-LDH treated at 200 °C showed the highest activity with a TOF of 142 h⁻¹, which was nearly 55% higher than that of the untreated catalyst. It could be related to not only the suitable amount of RuO₂·xH₂O for β-H cleavage, but also the presence of Co³⁺ species for the activation of O₂ molecules and storage of the resulting active O* species. Furthermore, the strong interaction between RuO₂ and the support was revealed to promote the adsorption and activation of benzyl alcohol and thus enhance the catalytic performance. Significantly, RuO₂/CoAl-LDH treated at 200 °C was found to selectively oxidize various alcohols to the corresponding aldehydes and ketones with respectable activity and had greater advantage comparable to that of some Ru catalysts.