Supercritical fluids applied to the sol-gel process for preparation of AEROMOSILS/palladium particle nanocomposite catalyst

摘要

A one-pot supercritical fluid (SCF) method was applied to prepare a series of silica aerogels. They were formed from alkoxysilanes by the sol-gel process directly in supercritical carbon dioxide. By this method no additional solvents are needed and the process of drying of wet gel afterwards is simplified. This method was modified by the addition of reactive polydimethylsiloxane (PDMS) chains, which yielded in organically modified silicates, the so-called "ORMOSILS" or in our case "AEROMOSILS" when prepared in the form of aerogels. The investigation of the prepared materials by atomic force microscopy (AFM) showed that they consisted mainly of particles with a diameter of 50-100 nm. 2-3 nm pores in these particles were indicated on the images. Further modification of the SCF method to yield AEROMOSILS with immobilized palladium particles was successful. This material was tested as a catalyst both for batch and continuous supercritical hydrogenation of 2,5-dihydro-2,5-dirnethoxy-furane.