Resumen El pirocloro (H3O)2Sb2O6·nH2O (H2Sb) fue sintetizado mediante tratamiento de óxido de antimonio (III) (Sb2O3) con peróxido de hidrógeno (H2O2), para ser evaluado en la deshidratación de fructosa a 5-hydroxymethylfurfural (HMF) en un sistema bifásico FA/FO (H2O/ MIBK:2butanol). Las pruebas catalíticas se llevaron a cabo en un reactor de vidrio tubular (15 mL) con rosca de teflón. El reactor se cargó con 1.5 ml de solución concentrada de fructosa (30 % p/p), 3.5 ml de solvente extractor MIBK: 2 butanol (7:3) y 50 mg de catalizador. El objetivo fue estudiar el efecto de factores como tiempo y temperatura de reacción, sobre la formación del producto de interés, logrando una conversión de sustrato del 93 % y un rendimiento a HMF del 79 %, luego de 90 min de reacción a 120 °C. Más importante aún, este sistema catalítico fue muy eficiente alcanzando un elevado rendimiento a HMF, superior a los reportados al emplear soluciones concentradas de fructosa (30% p/p). Por lo tanto, el pirocloro H2Sb se presenta como un catalizador muy prometedor para la obtención de HMF mediante trasformaciones de carbohidratos, provenientes de biomasa.

Abstract Pyrochlore (H3O)2Sb2O6·nH2O (H2Sb) was synthesized by treating with antimony oxide (III)(Sb2O3) and hydrogen peroxide (H2O2), to be evaluated in dehydration of fructose to 5-hydroxymethylfurfural (HMF) in a biphasic system FA/FO (H2O/ MIBK:2 butanol). The catalytic tests were carried out in a tubular glass reactor (15 mL) with a Teflon thread. The reactor was loaded with 1.5 ml of concentrated fructose solution (30% w/w), 3.5 ml of extracting solvent MIBK: 2butanol (7:3) and 50 mg of catalyst. The objective was to study the effect of factors such as reaction time and temperature on the formation of interest product, achieving a substrate conversion of 93% and a HMF yield of 79%, after 90 min of reaction at 120° C. More importantly, this catalytic system was very efficient, achieving a high HMF yield, higher than those reported when using concentrated fructose solutions (30% w/w). Therefore, pyrochlore H2Sb is presented as a very promising catalyst for obtaining HMF through carbohydrate transformations from biomass.

Four families of carbon fiber reinforced composites (CFRC) used in aeronautical industry were evaluated by flexural and interlaminar shear tests. It is also characterized three families of non-conditioned and conditioned CFRC by compression test. The composites were obtained by hand lay-up process in autoclave by using prepregs based on epoxy matrices (F155 and F584) and carbon fiber fabric reinforcements (PW-"Plain Weave" and 8HS-"Eight Harness Satin"). The F155-epoxy matrix was cured at 121 °C and the F584-epoxy type at 177 °C. After molding, the laminates were cut in specimens attending the ASTM D790 for the flexural test, the ASTM D2344 for the interlaminar shear test (ILSS) and the ASTM D3410 for the compressive test. The compressive tests were performed for testing the specimens before and after hygrothermal conditioning. The results show that the F584-epoxy matrix laminates present higher mechanical properties when compared to the F155-epoxy ones. The shear-tested samples observed by scanning electron microscopy and that ones tested in flexural, analyzed by stereoscopy, revealed that the fractured surfaces present typical aspects. The compressive results show that the hygrothermal conditioning caused the decrease of the compressive strength in, approximately, 8-20% depending on the laminate type. The failure modes of the tested specimens were evaluated showing good agreement with the literature.