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Ammonia borane is a promising hydrogen storage material due to its high gravimetric capacity (19.6 % wt), but it also presents limitations such as a slow hydrogen release with a long induction time, a difficult regeneration, or the formation of foams and gaseous by-products during thermolysis. Previous studies have shown that by nanoconfinement of ammonia borane within a porous support some of these limitations can be overcome due to the reduction and stabilization of ammonia borane particle size. However, this effect was only observed with moderate ammonia borane loadings, as with higher loadings the pores of the support became obstructed. In this work, silica aerogels produced by CO2 drying, with pore volumes up to 2 cm3/g, have been used to confine ammonia borane. The influence of the amount of ammonia borane loaded on the aerogel support on the thermal and structural properties of the material has been analyzed. It has been found that more than 60 wt% of ammonia borane can be effectively stored in the pores of the aerogel support. The resulting material shows faster hydrogen release kinetics by thermolysis at 80ºC, due to a significant reduction in the mea size of ammonia borane after confinement and the participation of SiOH and SiOSi groups of silica aerogel in the decomposition mechanism., 2018-09-20, Spanish Ministry of Economy and Competitiveness project ENE2011-24547

Ethane 1, 2 diamineborane (EDAB) was micronized from THF solutions using Supercritical Antisolvent (SAS) process. The influence of temperature, solute concentration and carbon dioxide fraction on the final properties of EDAB particles was studied. By SAS micronization, the original prismatic EDAB particles of about 400 µm with a crystallite size of 100 nm were converted into microspheres of less than 2 µm with a crystallite size of 50 nm. This reduction in the particle and grain sizes resulted in an improvement in thermal properties. The kinetics of release of hydrogen by thermolysis at 100ºC was also significantly enhanced due to the reduction in the diffusion length, reducing the time needed for the decomposition of the hydride by a factor of six. Moreover, a suppression of induction time was obtained by destabilization of the hydride after treatment. XRD and FTIR analyses showed that no chemical decomposition and no variation of the crystalline structure took place by SAS processing., 2018-07-15, Spanish Ministry of Economy and Competitiveness project ENE2014-53459-R

Producción Científica, Herbal medicinal plants are important sources of bioactive, medicinal compounds. In this work, impregnation of phytol as a model compound and multicomponent Clinacanthus nutans (C. nutans) plant extracts into alginate and silica aerogels was investigated, applying two different methods: wet impregnation and supercritical impregnation. Two types of C. nutans extracts were prepared by microwave-assisted extraction (MAE) using either ethanol-water solvent mixtures or pure ethanol as solvent. The impregnated compounds were analyzed by Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and chromatography (HPLC and UPLC–MS/MS). Results showed that supercritical impregnation method yielded the highest loading content with silica aerogels, with a content of 30.1 ± 0.6 wt% of the model compound phytol, and 11.5 ± 0.4 and 23.9 ± 1.0 wt% of the extracts obtained with ethanol/water and pure ethanol solvents, respectively. In the wet impregnation method, alginate aerogels exhibited higher loading than the silica aerogels regardless of their surface area properties, indicating that in this case other properties of carrier materials and the nature of compounds have a stronger influence on the compounds loading than the surface properties of the carrier. Impregnation in alginate aerogels yielded higher total phenols and flavonoids contents than in silica aerogels. Plasticized alginate biopolymer was formed when the supercritical impregnation was performed with excess of phytol at 200 bar and 40 °C, indicating that the swelling and/or plasticizing effect of SCCO2 was remarkable combined with the effect of excess solute. Release kinetics results indicate that the alginate aerogel impregnated with the extract obtained with pure ethanol is suitable for controlled drug release whereas the alginate aerogel impregnated with the ethanol/water extract is more appropriate for fast release purposes. The release kinetics results were fitted into several mathematical models: zero order, first order and Higuchi model, to evaluate the mechanism of the release. Results showed that diffusion and erosion and/or swelling control the release of extract from the aerogels., Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13)