Homogeneous catalytic oxidation of styrene and styrene derivatives with H₂O₂in the presence of polyoxotungstates.

Temperature and near infrared (NIR) light responsive multi-walled carbon nanotube (MWCNT)–κ-carrageenan hydrogel composites have been prepared. The effects of the MWCNTs on the microstructure, strength, swelling and release properties of the resultant materials were investigated. MWCNTs acted as reinforcing fillers and enhanced the mechanical properties of the hydrogels, the effect being mostly nanotube concentration dependent. Surface functionalization of nanotubes had a major influence on the swelling of the composites. The increased release of a model drug (methylene blue) in in vitro conditions, from κ-carrageenan hydrogel composites due to the NIR photothermal effect of MWCNTs was demonstrated at the physiological temperature. Thus, these composites are promising materials for the development of carriers for remotely activated drug delivery.

A series of tetrabutylammonium (TBA) salts of the transition metal mono-substituted silicotungstates [SiW₁₁M(H₂O)O₃₉]ⁿ⁻, M = Co^II, Fe^III, Mn^III, (SiW₁₁M) were explored as homogeneous catalysts for the oxidation of geraniol and styrene with H₂O₂. The most active homogeneous catalysts (SiW₁₁Co and SiW₁₁Fe) were immobilized onto an amine-functionalized SBA-15 (aptesSBA-15) and the resulting composites were characterized using several techniques (FT-IR, FT-Raman, UV-Vis/DRS, elemental analysis, powder XRD, SEM and N₂ adsorption–desorption isotherms). The catalytic performance of the new composites SiW₁₁Co@aptesSBA-15 and SiW₁₁Fe@aptesSBA-15 was investigated under similar experimental conditions to those used for homogeneous counterparts. 2,3-Epoxygeraniol and benzaldehyde were the main products obtained from geraniol and styrene oxidation, respectively, for all the catalysts. SiW₁₁Co and SiW₁₁Co@aptesSBA-15 showed to be the most active catalysts for the oxidation of geraniol and styrene. The recyclability of the composite SiW₁₁Co@aptesSBA-15 was investigated for three reaction cycles. The stability of the composites was confirmed using several techniques after catalytic cycles.