Hydrothermal synthesis and characterization of copper containing crystalline silicate mesoporous materials from gel mixture

摘要

Novel copper-containing crystalline silicate mesoporous materials (SCMM) have been synthesized by the hydrothermal treatment of slurries of silicon―magnesium―copper hydroxide precipitates along with quaternary ammonium salt. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed a house-of-cards type structure consists of very thin platy silicates. Nitrogen adsorption―desorption isotherms of calcined material show that it has a high surface area (～550 m~2 g~(-1)) and porosity properties. Pore characteristics are similar to that of MCM-41 and FSM-16, and fine-tuning of the pore size was achieved easily by modulating the synthesis temperature. Identification and the location of copper species in Cu-SCMM were done by X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR), respectively. ESR data of air-dried Cu-SCMM consist of clearly defined g_(‖) = 2.34, A_(‖) = 140 x 10~(-4) cm~(-1) and g_⊥ = 2.08 at room temperature and g_(‖) = 2.34, A_(?)= 160 x 10~(-4) cm~(-1) and g_⊥ = 2.10 at 77 K. The resulting material exhibited superior catalytic activity towards the hydrogenation of α―β unsaturated aldehyde in supercritical carbon dioxide.