Comparative study of silica-supported copper catalysts prepared by different methods: formation and transition of copper phyllosilicate

Abstract

Cu/SiO₂ catalysts prepared by ion exchange (IE), deposition precipitation (DP), homogeneous deposition–precipitation (HDP) using urea hydrolysis and ammonia evaporation (AE) were systematically characterized focusing on the formation and transition of copper phyllosilicate. It was generated during the AE, IE and HDP methods and decomposed to CuO after calcination at 450 °C, which was supported by BET, TPR, XRD and TEM. Copper phyllosilicate can be reduced to Cu⁰ rather than Cu⁺ below 350 °C. The formation of copper phyllosilicate promoted the dispersion of copper species. The Cu/SiO₂ catalyst prepared by the AE method possessed the highest Cu⁰ dispersion due to the high content of copper phyllosilicate in the catalyst precursor and thus exhibited the best activity for the hydrogenation of methyl acetate.