Recent Advances in Mesoporous Materials and Their Biomedical Applications

Since the beginning of civilization, porous materials have been used for medical purposes. Some studies have reported that the first uses of applications of porous materials were carried out by the Ancient Egyptian or Western Africans, where porous charcoal or clay minerals were used as antidiarrheal medicine [1,2]. The use of charcoal continued to be used for medical purposes throughout history. Indeed, the Hindi civilization used charcoal for the purification of H2O [3]. More recently, the British Empire added charcoal to water barrels to increase the durability of drinking water [4]. Nowadays, charcoal is used as animal feed because it helps in the health and growth of the animals [5]. Regarding clay minerals, the use of kaolinite or montmorillonite is actually employed in some medicine such as Kaopectate® due to its good antidiarrheal applications [2,6]. 8 (...)This research was funded by the Spanish Ministry of Science and Innovation (PID2021-122736OB-C42), FEDER (European Union) funds (PID2021-122736OB-C42, P20-00375, UMA20-FEDERJA88). Partial funding for open access charge: Universidad de Málag

Green approach to the Isosorbide Conversion into Dimethyl isosorbide

Isosorbide is one of the most promising products derived from sorbitol. It has already found many applications, mainly in the polymer industry and medicine, such as isosorbide polycarbonate1 (DURABIO®) and isosorbide nitrates as vasodilator for angina pectoris2. The methylation of the two hydroxyl groups of isosorbide molecule gives rise to the formation of dimethyl isosorbide (DMI), which is a high boiling solvent (235ºC), used in skin care formulations because of its solubilising capacity and performance enhancing of many different topical skin actives3. Currently, DMI synthesis implies the use of methyl halides or dimethyl sulfate. A safer and more environmental benign approach has been proposed by Tundo et al4 by employing dimethylcarbonate (DMC) as both reactant and solvent in the presence of sodium methoxide. In the present work, the synthesis of DMI in an excess of DMC by using a MgAl mixed oxides (MgAlOx), as heterogeneous catalyst, under mild reaction conditions, is proposed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto Plan Nacional CTQ2015-64226-C3-3-R Fondos FEDE

Cr-free Ni/MgO catalysts for hydrogenation of furfural

In the last century, the industrial development and the increase of the world population have caused the depletion of fossil reserves. This fact together with others factors have led to the search of alternative. Biomass is emerging as a widely available source to produce energy and, excluding fossil fuels, is the only source that can provide liquid fuels and chemicals. Lignocellulose is formed by cellulose, hemicellulose, lignin and other extractable components. In the case of hemicellulose, its hydrolysis leads to the formation of xylans and pentosans, which after dehydration can give rise to furfural. The high interest for furfural is attributed to its chemical structure, which provide high reactivity, making it potentially interesting for the synthesis of a vast variety of high value-added chemicals. Two of these important chemicals are furfuryl alcohol (FOL) and 2-methylfuran (MF), can be synthesized through hydrogenation of furfural, either in liquid or vapor phase. FOL is mainly used for the production of thermostatic resins, intermediates in the manufacture of lysines, vitamin C and dispersing agents. Meanwhile, MF is used in the synthesis of pesticides, in the pharmaceutical or perfume industries. Industrially, copper chromite catalyst is used, although the toxicity associated to the presence of chromium species has prompted the search of Cr-free catalysts. Therefore, much attention is being paid to the development of more sustainable and environmentally friendly catalysts, among them, catalytic systems based on Cu or Ni have demonstrated to be active and selective towards the formation of FOL and MF. The dispersion of metalspecies and their interaction with the support are key parameters that affect the catalytic activity and stabilityof catalysts. The use of metal oxides as supports can allow to obtain highly active and stable catalytic systems, and the electronic density of metal sites can be modified. The present work is aimed at the synthesis by Ni/MgO catalysts and the evaluation of their catalytic performance in the gas phase hydrogenation of furfural, at atmospheric pressure. x-Ni_MgO catalysts have been tested in the furfural hydrogenation, attaining the full furfural conversion with the 0.20-Ni_MgO catalyst, after 5 h of TOS, at 190 °C, by feeding a 5% furfural solution in cyclopentyl methyl ether, at a constant flow of hydrogen of 10 ml min-1. In all cases, catalysts are highly selective to furan. The analysis of the influence of the reaction temperature has revealed the existence of a volcano distribution, attaining the best catalytic performance at 190 °C. However, all catalysts suffer a progressive deactivation with TOS, by deposition of reactants and product.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech Ministerio de Economía y Competitividad (Proyecto CTQ2015-64226-C3-3-R) Fondos FEDE

Catalytic heterogeneous route for the synthesis of dimethyl isosorbide using dimethyl carbonate as methylating agent

In this contribution a heterogeneous catalytic route is envisaged by using as catalyst MgAlOx mixed oxides derived from hydrotalcite thermally treated (Mg/Al molar ratio of 3). The complete conversion of isosorbide is accomplished within the first hour but the DMI is not observed until 7 hours of reaction and its yield increases up to 100% after 24 hours of time on stream. The reutilization of the catalyst has shown a decline in DMI yield up to 52% after 4 runs even though the isosorbida conversion was of 100%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Hydrogenation of furfural over supported Pd catalysts

Lignocellulosic biomass is the most abundant and economical non-fossil carbon source. Furthermore, it is not competitive with the food chain, coming from lignocellulosic wastes including agricultural and food processing, local urban solid and forestry wastes. However, these are made up of complex carbohydrates (mainly, cellulose and hemicellulose), which require to be broken down in their respective monomers. The hemicellulose is mainly composed of pentosans, which, after an initial hydrolysis step, are dehydrated to furfural. Furfural is an important platform molecule, since it has a wide range of applications, being considered the main chemical, aside from bioethanol, obtained from the sugar platform for the synthesis of chemicals, for plastics, agrochemical and pharmaceutical industries. In the present work, the hydrogenation of furfural in gas phase has been studied by using Pd as active phase, and different metal oxides as support, in order to elucidate the influence of the support on the catalytic performance. Furfural can be converted into chemicals with important applications in many different industrial fields. Thus, reduction of furfural can proceed through different pathways depending on the experimental conditions, where the nature of the catalysts plays a key role. In the case of Pd-based catalysts, the main products come from the decarbonylation of furfural.The catalytic results reveals that the nature of the support exerts an important influence on furfural conversion and yield. The highest conversion (92% after 5 h of TOS at 463 K) was attained with a Pd-SiO2 catalyst, with a furan yield of 70 mol%. This catalyst is the most selective to furan and a moderate deactivation is only observed after 5 h reaction. The catalytic performance demonstrates that decarbonylation reaction was the main pathway, although the formation of furfuryl alcohol and 2-methylfuran also suggests that the hydrogenation of the carbonyl group of furfural takes place.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Desarrollo de catalizadores sólidos para la síntesis sostenible de dimetil isosorbida

En los últimos años, el interés creciente por la biomasa lignocelulósica como fuente renovable y sostenible para la producción de energía, biocombustibles y productos químicos con un amplio espectro de aplicaciones ha impulsado el desarrollo de nuevos procesos para su transformación integrada en las denominadas biorrefinerías. En este sentido, la hidrogenación de glucosa permite la síntesis de sorbitol, una de las moléculas plataforma identificadas por el Departamento de Energía deEstados Unidos como materiales de partida para la síntesis de productos químicos derivados de la biomasa mediante procesos catalíticos. Así, por ejemplo, su deshidratación y ciclación en medio ácido permite obtener isosorbida, de gran utilidad como intermedio para la industria farmacéutica y en la producción de polímeros biodegradables, entre otras aplicaciones. Además, su metilación conduce a la formación de dimetil isosorbida(DMI), un disolvente industrial sostenible de alto punto de ebullición (235ºC), con aplicaciones en farmacia y productos para el cuidado personal. El dimetilcarbonato (DMC) se ha propuesto como alternativa sostenible al uso de fosgeno para reacciones de carboximetilación, y de dimetil sulfato o haluros de metilo en reacciones de metilación, e incluso para la síntesis de isosorbida con bases fuertes. Por otra parte, la síntesis de dimetil isosorbida se ve favorecida por la reactividad de los grupos hidroxilos de la isosorbida, que pueden metilarse en presencia de un agente metilante adecuado a temperaturas moderadas, donde el DMC se ha empleado de forma satisfactoria, empleando catalizadores básicos como carbonato o metóxidos alcalinos disueltos en DMC. En esta comunicación se presentan los resultados más relevantes de la síntesis de DMI a partir de isosorbida, mediante catálisis heterogénea, en presencia de óxidos mixtos de Mg/Al obtenidos por calcinación de hidrotalcitas, y con DMC como agente metilante.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)