Gold nanoparticles have shown excellent activity for selective oxidation of alcohols; such catalytic systems are highly dependent on the initial activation of the substrates, which must occur on the catalyst surface in heterogeneous catalysts. In many cases, an extra base addition is required, although the basicity of the support may also be of significant importance. Here, we explored the intrinsic basicity of magnesium-based enrichments on CoFe₂O₄ magnetic nanoparticles for the oxidation of benzyl alcohol using molecular oxygen as oxidant. The MgO and Mg(OH)₂ enrichments enabled gold impregnation, which was not possible on the bare CoFe₂O₄ nanoparticles. The Au/MgO/CoFe₂O₄ and Au/Mg(OH)₂/CoFe₂O₄ catalysts reached 42% and 18% conversion, respectively without base promotion, in 2.5 hour and 2 bar of O₂. When the catalysts were tested with sub-stoichiometric amounts of base, they became more active (>70% of conversion) and stable in successive recycling experiments without metal leaching, under the same reaction conditions. We also showed the oxide phases of the enrichments performed using Rietveld refinements and how the Mg(OH)₂ phase interferes with the activity of MgO-based materials.

The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)₂ by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of O₂ and without extra-base addition, the calcined support reached 54.6% (100 °C) and 67.4% (140 °C) of conversion, presenting the remarkable and unexplored intrinsic basicity that strontium-based materials retain. With sub-stoichiometric K₂CO₃ adding, under the same catalytic conditions, the catalyst conducted the reaction with similar activity, but with excellent reusability in the process, without any gold leaching. We investigated the influence that the support synthesis method and the solvent used for the NPs stabilization have on the oxidation activity. The produced materials were fully characterized by XPS, Rietveld refinement, and TEM.

This work describes the preparation of babassu, castor oil biodiesel and mixtures in various proportions of these oils, using alkaline compounds of strontium (SrCO3 + SrO + Sr (OH)2) as heterogeneous catalysts. The mixture of oils of these oleaginous sources was used in the production of biodiesel with quality parameters that meet current legislation. The catalyst was characterized by X-ray diffractometry (XDR), physisorption of gas (BET method), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The viscometric technique was used to monitor the optimization. The transesterification reactions performed using strontium compounds reached conversion rates of 97.2% babassu biodiesel (BB), 96.4% castor oil biodiesel (COB) and 95.3% Babassu/Castor Oil Biodiesel 4:1 (BBCO41). Printed in Brazil - ©2013 Sociedade Brasileira de Química

This work described a new magnetic material enriched with strontium as catalyst to produce babassu biodiesel. The use of magnetic materials has attracted attention due to easy and fast separation from reaction medium. Moreover, they are ecologically correct, due to they generate less discards to the environment. Techniques of analysis and characterization were carried out to check the synthesis of magnetite and strontium ferrite, besides to verify the presence of hydroxide and carbonate in the structure of the strontium oxide. The best catalytic activities presented conversions of 78.6% and 89.7% when using the catalysts SrO/Fe₃O₄ and SrO/SrFe₂O₄, respectively. Density studies of the alkali active sites were performed to elucidate the best activity for the catalyst composed with SrFe₂O₄.