In this work two different synthesis methods of perovskites, SrCo0.5FeO3, were compared: combustion synthesis and oxides mixture aiming at evaluating their use as membranes for partial oxidation of methane. The combustion synthesis method explores an exothermic, generally very fast and self-sustaining chemical reaction between the desired metal salts and a suitable organic fuel, which is ignited at a temperature much lower than the actual phase formation temperature. The oxides mixture are based on a physical mixture of the powder oxides followed by calcination to obtain the desired phase. In order to obtain the membranes, we studied the conformation of bodies and the temperatures of sintering in the two powders synthesized. The powders were analyzed by density and grain size distribution and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). After conformation, in cylindrical form, the green bodies were analyzed by density. After sintering at 1150 °C, the membranes were analyzed by density and they were characterized by XRD and SEM. The powder obtained by combustion synthesis shows lower density and fine grains than the other obtained by oxides mixture. The membranes obtained present very different morphology depending on the precursor powder synthesis. The sintered membranes obtained by combustion method also present a very uniform morphology without segregation.

Hydrogenation of methyl pyruvate on a palladium or platinum surface in the presence of cinchona alkaloids leads to a high degree of enantiodifferentiation. In the present study, the semiempirical AM1 and PM3 methods are employed to perform a detailed analysis of the conformational behavior of cinchonidine and to study its interaction with methyl pyruvate. Nine different minima were located on the potential energy surface for cinchonidine by both the AM1 and the PM3 methods. Some barriers to interconversion between them are relatively high; however, it is always possible to connect two minima through barriers lower than 3.0 kcal/mol so most of the minima can interact with the substrate. The interaction between cinchonidine and methyl pyruvate was calculated by placing methyl pyruvate near the cinchonidine molecule in different orientations and optimizing the final complex. The calculated interaction energy is lower than 3.5 kcal/moland is predominantly due to van der Waals noncovalent interactions. An analysis of the structure of possible pro-R and pro-S complexes indicates that interaction between cinchonidine and methyl pyruvate alone is not enough to induce enantiodifferentiation.

The use of the ion-exchange method and the addition of lithium to Pt/Nb2O5 catalysts were investigated in this work, using techniques of temperature-programmed reduction, H2 and CO chemisorption, UV-Vis diffuse reflectance spectroscopy and the conversion of n-heptane as a catalytic test. The superficial precursor present after the calcination step is platinum oxide, as previously observed for Pt/Nb2O5 catalysts prepared by the incipient wetness method. For some of the samples, autoreduction was observed during the calcination step, with the formation of low dispersion metallic platinum. The Pt/Nb2O5 catalysts prepared by ion exchange showed a high yield of olefins, as compared to aromatics, in the conversion of n-heptane. However, a high yield of hydrogenolysis products was also observed. For some of the lithium-containing samples, there was a suppression of dehydrogenation and aromatization reactions, with an increase in central C-C bond hydrogenolysis.