Optimización de KIT6-Zr sulfatado para la obtención de isosorbida

En los últimos años, el desarrollo de nuevos procesos catalíticos para la transformación de azúcares está situando a la biomasa lignocelulósica en un lugar privilegiado como materia prima sostenible y renovable para la producción de biocombustibles y productos de alto valor añadido. En este contexto, la hidrogenación de glucosa a sorbitol, y su posterior doble deshidratación y ciclación para obtener isosorbida mediante el uso de catalizadores sólidos ácidos, está atrayendo el interés científico. La isosorbida posee excelentes propiedades físico-químicas aplicables a diversos campos de la industria, siendo un importante intermedio farmacéutico (como diurético, y tratamientos de hidrocefalia y glaucoma), aditivo para mejorar la resistencia y rigidez de polímeros tales como tereftalato de polietileno (PET) y monómero para la producción de polímeros biodegradables. En el presente trabajo se han optimizado distintos parámetros entre los que destacan las relaciones molares Si/Zr y el tiempo de envejecimiento en la síntesis de KIT6 sulfatado, así como para evaluar y mejorar su comportamiento catalítico en la producción de isosorbida a partir de sorbitol fundido. Se ha logrado alcanzar un rendimiento en isosorbida del 58%, a 175ºC, después de 3 horas de reacción con un 10 wt.% de catalizador. Todos los catalizadores se han caracterizado mediante DRX, SEM-EDS, adsorción de N2, XPS y la acidez por NH3-DTP y FTIR de piridina, para establecer relaciones estructura-actividad catalítica.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Sílices mesoporosas KIT-6 funcionalizadas como catalizadores ácidos para la deshidratación de sorbitol a isosorbida

La modificación de sílices mesoporosas mediante la incorporación de heteroátomos (Zr, Al, Ti, entre otros) y/o tratamiento con ácidos minerales es una estrategia atractiva en catálisis heterogénea para la preparación de catalizadores ácidos para una gran variedad de procesos de alto interés industrial. De este modo, los catalizadores SBA-15 funcionalizados con ácido arenosulfónico se han evaluado en la acetalización del heptanal, y para la producción de 5-hidroximetilfurfural a partir de la deshidratación de fructosa se han empleado también catalizadores de SBA-15 funcionalizados con ácido sulfónico. Sus altas conversiones se explican por el carácter hidrofóbico asociado a su estructura organosilícea y a la fortaleza de sus sitios ácidos. En este contexto, la arquitectura de los poros, la concentración y fortaleza de los sitios ácidos son factores importantes, directamente relacionados con el rendimiento catalítico en muchas de las reacciones de interés, como es el caso de la deshidratación de sorbitol a isosorbida. Por lo tanto, el objetivo de este trabajo es el estudio de las propiedades catalíticas de una sílice KIT6 conteniendo diferentes cantidades de circonio, así como la influencia de su posterior sulfatación, en la deshidratación de sorbitol. Los datos de caracterización físico-química y los resultados catalíticos indican que la incorporación de circonio reduce la microporosidad, pero la presencia de sitios ácidos de Brönsted permite alcanzar altas selectividades a isosorbida. Además, se observan variaciones en las propiedades texturales al modificar los tiempos de hidrólisis y envejecimiento. Es posible alcanzar un rendimiento del 52% en isosorbida con catalizadores impregnados a volumen incipiente, a 140 h y después de sólo 3 h de tiempo de reacción.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Enhanced acidity properties of KIT6_Zr as solid catalyst for the dehydration of sorbitol to isosorbide

he modification of mesoporous silicas by incorporating heteroatoms (Zr, Al, Ti, among others) and / or treatment with mineral acids are an attractive strategy in heterogeneous catalysis for the preparation of solid acid catalysts for a variety of processes of industrial interest. In this context, the architecture of the pores and the concentration and strength of acid sites are important factors, directly related to the catalytic performance in the dehydration of sorbitol to isosorbide. In order to modulate the surface acidity of a mesoporous KIT-6-type silica, the Si/Zr molar ratio has been varied using TEOS and iso-propoxidezirconium, as precursors. Besides, different sulfation treatments of the zirconium-doped KIT-6 catalyst were carried out: i) immersion in a concentrated sulfuric acid solution, under stirring, ii) impregnation at incipient volume with sulfuric acid and iii) impregnation of a KIT-6 silica with zirconium sulfate solution and varying thecalcination temperature. These catalysts were evaluated in the dehydration of sorbitol in a batch reactor, in molten medium, at different reaction times and temperatures. The zirconium sulfate-based catalyst calcined at 350ºC reaches an isosorbide yield of 55%, at only 140°C, which can be explained by its higher concentration of acid sites. Moreover, this catalyst possesses a high surface area and Brönsted acidity. The physical-chemical characterization data and catalytic results demonstrate that the incorporation of zirconium reduces slightlythe microporosity, although the presence of Brönsted acid sites allows attaining high selectivities to isosorbide. In addition, variations in textural properties are observed by modifying hydrolysis and aging times.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Sulphated KIT6-Zr as an efficient solid acid catalyst for the production of isosorbide from sorbitol

In recent years, the development of new catalytic processes for the transformation of sugars is converting lignocellulosic biomass in a sustainable and renewable feedstock for the production of biofuels and high value-added chemicals. In this context, the hydrogenation of glucose to sorbitol, and its subsequent double dehydration and cyclization allows to obtain isosorbide. Much attention is being paid in the development of active and selective solid acid catalysts to transform sorbitol into isosorbide. The present work deals with the optimization of different parameters, such as the Si/Zr molar ratio and aging time, in the hydrothermal synthesis of sulphated KIT6. The catalytic activity of the synthesized catalysts was evaluated in the production of isosorbide from molten sorbitol. An isosorbide yield of 58% has been reached at 175 °C after 3 hours of reaction with 10 wt% catalyst. All catalysts have been characterized by various techniques, including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), N2 adsorption at -196ºC, X-ray photoelectron spectroscopy (XPS) and the acidity has been measured by NH3-TPD and FTIR of adsorbed pyridine, to elucidate structure-activity relationships.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

γ-Al2O3 as acid catalyst for dehydration of glucose to 5-hydroxymethylfurfural

Currently, the search and development of sustainable feedstocks for chemicals derived from petrol have gained worldwide attraction because of the instability of the price of crude oil, the reduction of fossil oil reserves, and the environmental concerns associated to the greenhouse effect caused by CO2 emissions, being biomass one of the world’s most important renewable carbon sources. The major component of plant-derived biomass are carbohydrates, being of great importance to develop efficient and green approaches to their valorization by conversion into high value-added products. Thus, glucose can be transformed by dehydration into 5-hydroxymethylfurfural (HMF), which is a versatile and key intermediate for the production of a wide variety of biobased chemicals and it is attracting much attention in biofuels and chemical industry. Different catalytic systems have been evaluated for HMF production from C6 carbohydrates as glucose, mostly based on heterogeneous catalysis as alternative to the use of liquid mineral acids. On the other hand, the high surface area, large pore size and thermal and hydrothermal stabilities of some mesoporous solids make them suitable for many catalytic processes. In the present work, the dehydration of glucose to HMF has been evaluated by using different mesoporous γ-Al2O3 with acid, neutral or basic character, in a biphasic water–MIBK solvent system to avoid the HMF degradation and its possible reaction with the intermediates from glucose to give soluble polymers and humins or acetalization with glucose. Different experimental parameters, such as reaction temperature and time, as well as the addition of inorganic salts have been studied in order to reach the maximum HMF yield.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Ministry of Economy and Competitiveness (CTQ2012-38204-C04-02 project), Junta de Andalucía (RNM-1565) and FEDER fund

Gas phase selective hydrogenation of furfural to furfuryl alcohol and 2-methylfuran over Cu-CeO2 coprecipitated catalysts

Furfural is an important chemical derived from lignocellulosic biomass, in particular from C5 sugars like xylose, and it is considered as a platform molecule of great potential for the synthesis of a broad spectrum of chemicals. In this sense, furfuryl alcohol and 2-methylfuran are two important chemicals which can be produced through furfural hydrogenation, either in liquid or vapor phase, although the latter is preferred because it can be carried out at atmospheric pressure. Industrially, a copper chromite catalyst is used, although this catalyst can become very toxic due to the presence of chromium. Therefore, much attention is being paid to the development of chromium-free catalysts, more sustainable and environmentally friendly, as those based on Cu or Ni which are active and selective towards the formation of furfuryl alcohol and 2-methylfuran. Furfuryl alcohol is mainly used for the production of thermostatic resins, intermediate in the manufacture of lysine, vitamin C and dispersing agents. Meanwhile, 2-methyl furan is used in the synthesis of pesticides, or in the pharmaceutical and fragrance industries. The aim of this work is the synthesis of a series of copper based catalysts, which have been synthesized by coprecipitation of copper and cerium(IV) and subsequent thermal programmed reduction. This method allows increasing the dispersion of Cu particles, while the use of a support like CeO2 can modify the electronic density of the active phase, which can influence the catalytic activity and resistance to deactivation.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Economy and Competitiveness Ministry (Project CTQ2012-38204-C03-02), Junta de Andalucía (Project: RNM-1565) and FEDER funds of the European Unio

Valorization of carbohydrates: dehydration of sorbitol to isosorbide in the presence of acidic zeolites

Currently, the growing interest in the use of biomass as a renewable and sustainable raw material for the production of energy, chemicals and biofuels is driving the development of new catalytic processes and technologies for its conversion. In this context, the transformation of lignocellulosic biomass can lead to a variety of platform chemicals, with a broad spectrum of applications. Sorbitol is one of the useful biomass-derived chemicals that is obtained by catalytic hydrogenation of glucose, which subsequent dehydration and intramolecular cyclization in acid medium gives rise to the formation of isosorbide. This is a high value-added chemical widely used as intermediate in the pharmaceutical industry, additive polymers such as polyethylene terephthalate (PET) and production of biodegradable polymers. Mineral acids such as sulphuric and hydrochloric acids have efficient catalytic properties for dehydration of sorbitol. However, the well-known drawbacks associated to homogeneous catalysis have promoted the studies of heterogeneous catalytic processes. Thus, solid acid catalysts such as zeolites, tetravalent metal phosphates and sulfated copper oxide have been reported as alternative solid catalysts. Nevertheless, sometimes, drastic experimental conditions are required to reach a high catalytic activity. In the present work, different commercial zeolites, in their protonic form, have been evaluated as acid solid catalysts for sorbitol dehydration, and several experimental variables have been optimizedUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Ministerio de Economía y Competitividad (CTQ2012-38204-C04-02 project), Junta de Andalucía (RNM-1565) y Fondos FEDER de la U

Mesoporous niobium oxide for dehydration of D-xylose into furfural

Se ha demostrado que el óxido de niobio mesoporoso es un catalizador eficaz para la deshidratación de D-xilosa a furfural, alcanzando una conversión del 92% y un rendimiento de furfural 49,3% a 170º C y 90 minutos. La lixiviación de Nb, determinada por ICP-MS, era inferior al 0,5% en peso de la concentración de Nb inicial, confirmando de este modo la estabilidad del catalizador ácido sólido.El furfural posee un gran potencial como molécula plataforma de origen renovable para la síntesis de una alta variedad de compuestos químicos. Se obtiene mediante la deshidratación de pentosas, principalmente a partir de D-xilosa, proceso catalizado por ácidos minerales en fase homogénea. Por tanto, dentro de la química verde y la búsqueda de sostenibilidad de los procesos catalíticos, es necesaria su sustitución por catalizadores sólidos ácidos que sean tolerantes al agua, ya que es el disolvente más utilizado para esta reacción. El óxido de niobio posee propiedades ácidas y es insoluble en agua, pero su superficie específica es muy baja. Por lo tanto, resulta muy interesante la síntesis de un óxido de niobio mesoporoso para emplearlo como catalizador en esta reacción. En este trabajo, se ha sintetizado un Nb2O5 mesoporoso y se ha evaluado su comportamiento catalítico en la obtención de furfural a partir de D-xilosa.Spanish Ministry of Science and Innovation (ENE2009-12743-C04-03 project)Junta de Andalucía (P09-FQM-5070).Ministry of Science and Innovation for the financial support under the Program Ramón y Cajal (RYC-2008-03387)

Gestión del circulante. Una aplicación práctica para la PYME

Nunca a liquidez foi un ben tan prezado. A Gran Crise de 2008 contraeu a demanda e estrangulou o crédito. E a que apunta tras a sacudida do COVID confirma que o que ten liquidez quizá poida aguantar e sobrevivir. Esa é a terapia que se prescribe ás empresas desde as políticas públicas. A xestión do circulante debe orientarse, máis que nunca, a preservar a liquidez e, tamén, a apoiar a rendibilidade. Este traballo tratar de ocupar un espazo de coñecemento útil para un estudante de finanzas e para un xestor financeiro. Faio coa humildade que debe ter o coñecemento cando un financeiro ha de enfrontarse ás súas limitacións

Furfuryl alcohol production by liquid phase catalytic transfer hydrogenation of furfural on alumina as Lewis acid catalyst

Currently, much attention is being paid to the development of efficient and environmentally friendly technologies for the sustainable production of energy, fuels and chemicals [1]. In this context, lignocellulosic biomass appears as a renewable alternative feedstock to fossil resources. Thus, dehydration of C5 carbohydrates leads to furfural (FUR), a versatile platform molecule for the synthesis of a large spectrum of chemicals. Among them, the most important is furfuryl alcohol (FOL), accounting for 65% of FUR production, which finds application in the preparation of resins used as high-quality cores and molds for metal casting, reactive solvent for phenolic resins in the refractory industry, chemical building block for the synthesis of tetrahydrofurfuryl alcohol and pharmaceuticals and manufacture of fragrances [2,3]. FOL is prepared industrially by the catalytic hydrogenation of furfural, which can be carried out in vapor or liquid-phases, being the former in the presence of copper chromite the preferred industrial route. However, other products such as 2-methylfuran, tetrahydrofurfuryl alcohol and 2-methyl tetrahydrofuran can result from furfural hydrogenation, besides furan and THF, different pentanediols, 2-pentanone and 2-pentanol, cyclopentanone and cyclopentanol. The selectivity pattern depends strongly on reaction conditions and on the nature of the catalyst used. Nevertheless, a synthetic approach based on the catalytic transfer hydrogenation (CTH), based on the Meerwein-Ponndorf-Verley (MPV) reduction of an aldehyde (or ketone) coupled to the oxidation of a secondary alcohol, has been also proposed, which does not require supply of external hydrogen and the alcohol can be chosen in order to produce an aldehyde or ketone with industrial applications [4,5]. The present contribution deals with the production of FOL from furfural by CTH, using different commercial aluminas as catalysts and a secondary alcohol as hydrogen donor, in liquid phase. The results have demonstrated that the formation of other by-products is minimized and FOL is produced in high yield, at temperatures ranging between 90 and 150ºC, by using 2-propanol. Thus, full conversion of furfural and a FOL selectivity higher than 90 mol% are attained after only 2 h, at 150ºC, a FUR concentration of 0.25 M in 2-propanol and a catalyst/FUR weight ratio of 1:1 (Fig. 1). A reaction mechanism, involving Lewis acid sites present on the alumina surface in the activation of FUR and 2-propanol, has been put forward. Different experimental parameters (FUR concentration, reaction temperature, catalyst loading, type of alumina and nature of alcohol) have been optimized in order to achieve suitable FOL yields. Moreover, reutilization has been evaluated to support the advantage of the heterogeneous catalytic process which allows the reuse of the solid catalyst. Finally, and considering that dehydration of xylose to furfural is accomplished in the presence of solid acid catalysts, the one-pot synthesis of FOL from xylose has been undertaken by tuning selected experimental variables.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec