Artículos SCI

A method consisting of the alkaline hydrolysis of tomato pomace by-products has been optimized to obtain a mixture of unsaturated and polyhydroxylated fatty acids as well as a non-hydrolysable secondary residue. Reaction rates and the activation energy of the hydrolysis were calculated to reduce costs associated with chemicals and energy consumption. Lipid and non-hydrolysable fractions were chemically (infrared (IR) spectroscopy, gas chromatography/mass spectrometry (GC-MS)) and thermally (differential scanning calorimetry (DSC), thermogravimetric analysis (TGA)) characterized. In addition, the fatty acid mixture was used to produce cutin-based polyesters. Freestanding films were prepared by non-catalyzed melt-polycondensation and characterized by Attenuated Total Reflected-Fourier Transform Infrared (ATR-FTIR) spectroscopy, solid-state nuclear magnetic resonance (NMR), DSC, TGA, Water Contact Angles (WCA), and tensile tests. These bio-based polymers were hydrophobic, insoluble, infusible, and thermally stable, their physical properties being tunable by controlling the presence of unsaturated fatty acids and oxygen in the reaction. The participation of an oxidative crosslinking side reaction is proposed to be responsible for such modifications.

In this work, we prepared SiC-supported Pt-Cu thin films by magnetron sputtering for use as catalysts for the combustion of hydrogen under oxidizing conditions. We tested the catalysts as prepared and after chemical dealloying. A methodology is presented to fabricate catalytic thin films of a desired composition with tailored magnetron targets with lower Pt consumption. The deposition gas was changed to prepare columnar (Ar-deposited) and closed-porous (He-deposited) films to study the effect of the microstructure on the activity. The effect of composition was also studied for the columnar samples. The as-prepared Pt-Cu thin films showed significant activity only at temperatures higher than 100 °C. Dealloying permitted an increase in the activity to achieve near room-temperature activity. The dealloyed closed-porous He-deposited sample was the most active, being able to convert as much as 13.15 LH2·min−1 gPt−1 at 70 °C (Ea = 1 kJ mol−1). This sample was preferentially dealloyed on the surface, yielding an almost pure Pt shell (96% at. Pt) and a Cu-depleted interior (71% at. Pt). This compositional inhomogeneity enabled the sample to achieve enhanced activity compared to the Ar-deposited columnar sample (with similar initial composition, but uniformly dealloyed), probably due to the compressive surface lattice strain. The dealloyed closed-porous He-deposited sample was shown to be durable over five cycles.