José J. Martínez

Preyssler Heteropolyacids in the Self‐Etherification of 5‐Hydroxymethylfurfural to 5,5′‐[Oxybis(methylene)]bis‐2‐furfural Under Mild Reaction Conditions

The synthesis of 5,5′‐[oxybis(methylene)]bis‐2‐furfural (OBMF) from 5‐hydroxymethylfurfural (5‐HMF) was studied using bulk and alumina‐supported Preyssler heteropolyacids (HPAs). The formation of OBMF was related to the amount of Brønsted acid sites, and the lowest yield of OBMF was obtained with supported HPAs. However, the Lewis acidity of the HPA supported on Al2O3 favored the formation of 2,5‐dimethylfurane. The effects of solvent, catalyst loading, temperature, and reaction time on the selectivity to OBMF from 5‐HMF were studied to optimize OBMF production using bulk Preyssler HPAs; a yield of 84 % to OBMF was obtained at 5 h and 343 K. These results demonstrate that bulk Preyssler HPA is a good candidate for OBMF synthesis under mild reaction conditions.

Valorization of Oleuropein via Tunable Acid-Promoted Methanolysis

The acid-promoted methanolysis of oleuropein was studied using a variety of homogeneous and heterogeneous acid catalysts. Exclusive cleavage of the acetal bond between the glucoside and the monoterpene subunits or further hydrolysis of the hydroxytyrosol ester and subsequent intramolecular rearrangement were observed upon identification of the most efficient catalyst and experimental conditions. Furthermore, selected conditions were tested using oleuropein under continuous flow and using a crude mixture extracted from olive leaves under batch. Formation of (-)-methyl elenolate was also observed in this study, which is a reported precursor for the synthesis of the antihypertensive drug (-)-ajmalicine.

KINETIC STUDY OF THE HYDROGENATION OF CITRAL ON Ir PROMOTED Au/TiO2 CATALYST

ABSTRACT A kinetic study of citral hydrogenation over an Au-Ir/TiO 2 catalyst was performed with the aim to understand the effect of iridium on gold in this catalytic system. Au-Ir/TiO 2 catalyst was prepared by co-deposition precipitation in an atomic ratio of 3/1. The effect of citral concentration, hydrogen pressure and temperature effect were also studied. The product distribution obtained is related with the proportion of Me δ+ /Me 0 sites. The deactivation of the catalyst occurs in the whole studied temperature range, 363 to 403 K, being more drastic as temperature increases due to the irreversible adsorbed CO blocks principally Ir 0 sites. From initial reaction rates treatment an apparent global order close to 1 was determined. A Langmuir-Hinshelwood-type kinetic model involving the surface reaction as the rate limiting step between adsorbed citral and hydrogen on active sites with different nature shows good agreement with experimental initial reaction rates. Keywords: Citral, Au- Ir catalyst, kinetic study.

Hidrogenación de cinamaldehído sobre catalizadores Au/ZrO2 y Au/ZrO2-SiO2. Efecto del soporte y método de preparación

Se prepararon catalizadores de oro soportados en ZrO2 and ZrO2-SiO2 por impregnacion incipiente (Imp.I.) y depositacion-precipitacion con urea (DPU) con una carga nominal del metal del 1 %. Los solidos fueron caracterizados por difraccion de rayos X (DRX), fisisorcion de nitrogeno y reduccion a temperatura programada (TPR). La actividad catalitica fue evaluada en la hidrogenacion de cinamaldehido. La selectividad hacia el producto deseado es influenciada por la fase cristalina o amorfa del soporte y el metodo de deposicion del oro

New application of decaniobate salt as basic solid in the synthesis of 4 H -pyrans by microwave assisted multicomponent reactions

This study focuses on the search of new applications of polyoxometalates known as decaniobate ions [Nb10O28]6−. The decaniobates can be used as basic solid catalysts in multicomponent reactions to obtain good yields to 4H-pyrans (> 95%) under microwave radiation and solvent-free conditions, using several aldehydes with different electron-withdrawing or electron donor substituents. The synthesis of (TMA)6 [Nb10O28]6H2O was performed following a simple protocol (HPNb), which was modified to decrease the number of hexaniobate species that are formed as impurities (HPNb-HF).

Synthesis of 1,4-dihydropyrimidines with immobilized urease: effect of method immobilization on magnetic supports

Abstract The effect of the urease immobilization method was studied on magnetic supports for the Biginelli/Hantzsch reaction. For this purpose, Fe3O4/SiO2 was modified with 3-aminopropyl-triethoxysilane and then activated with glutaraldehyde. A ratio of 500 mg of enzyme per gram of support at 4°C and 18 h were sufficient for the physical adsorption, while 24 h were required for covalent bonding. The Biginelli and Hantzsch reactions were used to evaluate urease application in multicomponent reactions (MCRs). The synthesis of 1,4-dihydropyrimidines was successfully performed using immobilized urease favoring the Hantzsch product. The magnetic properties of the supports allow easy separation, and the urease immobilized by both methods improved the enzymatic activity compared to that of free urease.

Estudio de la zeolita beta modificada con Ce, La, -SO3H y óxidos de hierro en la hidrólisis de celulosa

La acidez de la zeolita beta fue modificada por impregnacion con cerio, lantano, grupos sulfonicos y oxidos de hierro, este ultimo se utilizo para generar propiedades magneticas en el material que permitan la recuperacion del catalizador y reciclaje en reaccion en fase liquida. Los solidos obtenidos fueron caracterizados por DRX, espectroscopia infrarroja FT-IR, la acidez fue obtenida por titulacion y la actividad catalitica fue evaluada en la hidrolisis de celulosa cristalina como porcentaje de azucares reductores totales (ART). La cristalinidad de los solidos impregnados con Oxidos de Ce y La no se ve afectada, caso contrario ocurre cuando se impregna con oxidos de hierro, ademas la acidez disminuye en ambos casos. La incorporacion de grupos sulfonicos tanto a la zeolita beta precursora como a la magnetizada aumenta la acidez y mostro rendimientos del 59% y 38% respectivamente alto rendimiento de azucares reductores totales en la reaccion.