Properties and Characterization of Silica Aerogel-Metal Composites Produced by a Supercritical Impregnation process
Sustainable process-product development & green chemistry
SCF as Solvent Substitutes (T1-8)
Keywords: supercritical fluids, impregnation, aerogel, composite.
Silica aerogels have unique properties such as large surface area, small pores, good transparency, good electrical, acoustic and thermal insulation. These properties provide the material with a large spectrum of potential applications, among others as catalyst support and insulator. However, the field of application of silica aerogel can be enlarged by the production of new composites formed by an active substance trapped in a matrix of aerogel. This kind of composites can be prepared by post-treatment of the dried aerogel with a supercritical fluid (SCF). This method is based on the fact that the open pore network of silica aerogel facilitates the transport of the SCF trough the volume of the material. A SCF is a fluid that has been heated and compressed above its critical temperature and pressure. The properties of a SCF are intermediate between those of a gas and a liquid and can be adjusted by slight changes in temperature or pressure. Carbon dioxide is particularly attractive because it is chemically inert, non-toxic, environmentally acceptable and leaves no residue in the treated materials.
In the present work, silica aerogel has been loaded with ferrocene and cobaltocene by impregnation from a supercritical carbon dioxide phase. After depressurization, the impregnated metallocene has been reduced to elemental metal by heat treatment.
The effect of metallocene concentration, temperature, pressure and depressurization mode on aerogel properties have been studied. The obtained products have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and FT-IR spectrophotometry.
First results show that metallocenes can be uniformly dispersed into the aerogel. Moreover, metal loading and particle size are controllable by properly changing operating conditions.
Presented Monday 17, 16:00 to 16:20, in session SCF as Solvent Substitutes (T1-8).
