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Item type:Publication, Access status: without files , Adsorptive crystallization of benzoic acid in aerogels from supercritical solutionsIn this work, adsorption and crystallization of benzoic acid in different porous carriers (silica aerogel, MCM41, Trisopor glass, zeolite) from supercritical CO2 solutions is studied. The main purpose is to reveal the influence of the adsorptive properties of the carrier on the crystallization behavior of the solute. Therefore, both adsorption and crystallization processes are studied as a function of carrier's surface properties. Adsorption of the solute and CO2 is measured in situ using a magnetic suspension balance, whereas crystallization is realized in a high pressure view cell. The carriers could be loaded with up to ∼35 wt.% of benzoic acid, depending on the nature and the amount of the functional groups of the carrier. The size of the benzoic acid particles obtained inside the aerogel matrix depends on the crystallization conditions and is in the range of ∼20 nm-50 μm. The crystallinity of the particles was studied and it is shown that the physical state of the loaded benzoic acid inside the pores of aerogels is influenced by benzoic acid-aerogel surface interactions: strong interactions favor the amorphous form, weak interactions favor crystalline particles. The amorphous form of benzoic acid is shown to be stable over a long time period. Thus, silica aerogels can be used for stabilizing amorphous forms of organic compounds, which can be used for instance in pharmaceutical applications for the improvement of drug bioavailability.Publicationtype: Journal Article19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adsorption and thermal release of highly volatile compounds in silica aerogelsThis work reports the adsorption/desorption behaviour of two highly volatile compounds (1-menthol and 2-methoxy pyrazine) in hydrophobic and hydrophilic silica aerogels where CO2 is used as an effective solvent to deliver these compounds to the inner surfaces of the aerogels. The thermal desorption behaviour of both substances depends intimately on the strength of the interactions of the absorbed substance with the type and availability of hydrophobic and hydrophilic surface groups in each aerogel. For example, as much as ∼50 wt% of either compound remains absorbed on the hydrophilic aerogel surface at temperatures of ∼250-300 °C, whereas these same compounds are released from the hydrophobic aerogel at 100-150 °C lower temperatures. The results reported here provide insight into the application of silica gels as delivery/storage devices with potential applications in the food, drug, flavors, and other allied industries.Publicationtype: Journal Article28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Crystallization under supercritical conditions in aerogels(Elsevier, 2007-08-17); ; ; ; In this work crystallization of organic compounds in silica aerogels is studied. The effect of density and surface properties of silica aerogels on crystallization of a model substance, naphthalene, from supercritical CO2 is investigated. It is shown that the surface properties of aerogels play a significant role in affecting the crystallization process. Loadings up to 55 wt% could be achieved for hydrophilic aerogels whereas hydrophobic aerogels could be loaded with ca. 40 wt% of naphthalene. Naphthalene crystals in the range of 500 nm-2 mm were obtained inside the aerogel matrix depending on the crystallization conditions. The potential of this process as "adsorptive crystallization" is discussed.Publicationtype: Journal Article34