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

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 (similar to 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(perpendicular to) = 2.08 at room temperature and g(parallel to) = 2.34, A(parallel to) = 160 x 10(-4) cm(-1) and g(perpendicular to) = 2.10 at 77 K. The resulting material exhibited superior catalytic activity towards the hydrogenation of alpha-beta unsaturated aldehyde in supercritical carbon dioxide. (C) 2003 Elsevier B.V. All rights reserved.