One-Step Synthesis of Mesoporous Metal−SiO₂ Particles by an Aerosol-Assisted Self-assembly Process

Abstract

Spherical mesoporous silica particles with entrapped metal nanoparticles are synthesized from a onestep aerosol-assisted self-assembly process using sols of an alkoxysilane, ethanol, surfactant, water, HCl, and metal precursors (e.g., salts or complexes). Utilizing nitrogen as a carrier gas, the sol is sent through an atomizer, producing aerosol droplets, which are passed through a tubular furnace heated to 400 °C. Solvent evaporation from the droplets enriches the nonvolatile components and results in the coassembly of silicate and surfactant into 3-dimensional mesostructures with incorporated metal precursors. Lamellar, cubic, and hexagonal mesostructures are achieved by using different surfactants. Subsequent calcination of the surfactant and reduction of the metal result in spherical mesostructured porous silica particles with supported metal nanoparticles. Nitrogen sorption techniques, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction are used to characterize the particles. Mesoporous silica particles with 0.5% Pd are tested as a catalyst in the hydrodechlorination reaction of 1,2-dichloroethane and exhibit ∼100% conversion above 350 °C and ∼100% ethylene selectivity, demonstrating the potential of such nanocomposites as catalysts.

Aerosol Route to Functional Nanostructured Inorganic and Hybrid Porous Materials

“…By spray-drying, the localization of heteroelements, introduced in the pristine solution as molecular or salt precursors, is very sensitive to both the chemistry of precursors in solution and his reactivity and interactions with structuring agent and silica oligomers. In literature, the following heteroelements have always been incorporated into acidic conditions, which is needed for the structuration of powders by EISA: aluminium, [ 46 , 136-141 ] zirconium, [ 48 , 139 , 142 ] calcium, [ 47 ] iron, [ 143 ] phosphate ions, [ 144 ] palladium, [ 145 ] etc. As heteroelement concentration increases in the solution, the trapping capacity of the structuring agent and silica oligomers play a crucial role in the fi nal localization of metallic centres.…”

Embedded Phases: A Way to Active and Stable Catalysts

“…[51] The method used a solution of TEOS, a surfactant, HCl, and a metal salt that was sprayed and quickly evaporated using an aerosol-assisted method. The rapid hydrolysis of TEOS and the co-assembly of silica into ordered mesoporous structures incorporated metal precursors, and after calcination and reduction, the materials were found to present metallic particles embedded into the silica spheres.…”

Generation and Sizing of Particles for Aerosol-Based Nanotechnology

“…Despite this, pneumatic atomization has been successfully used for synthesizing aerosol nanoparticles from colloid solutions for technological application (e.g. Hampsey et al 2005). …”