Catalytic Activity of Mixed Al2O3-ZrO2 Oxides for Glucose Conversion into 5-Hydroxymethylfurfural

In the present work, a series of catalysts based on aluminum and zirconium oxides was studied for the transformation of glucose into 5-hydroxymethylfurfural. These catalysts were characterized by using experimental techniques, such as X-ray diffraction, N2 adsorption–desorption at -196 ºC, X-ray photoelectron spectroscopy, temperature-programmed desorption of NH3 and CO2, and scanning transmission electron microscopy. The catalytic behavior in glucose dehydration was evaluated in a water-methyl isobutyl ketone biphasic system, in the presence of CaCl2, in order to minimize losses due to unwanted secondary reactions. High glucose conversion and 5-hydroxymethylfurfural (HMF) yield values were obtained in the presence of an Al(Zr)Ox catalyst with an Al:Zr molar ratio of 7:3, reaching 97% and 47%, respectively, at 150 ºC after 120 min. Under tested conditions, this catalyst retained most of its catalytic activity for four reuses.This research was funded by the Spanish Ministry of Economy and Competitiveness (RTI2018-94918-B-C44), FEDER (European Union) funds (UMA18-FEDERJA-171) and Malaga University

Production of Biofuels by 5-Hydroxymethylfurfural Etherification Using Ion-Exchange Resins as Solid Acid Catalysts

In this work, acidic ion-exchange resins with strong Brönsted sulphonic groups were assessed in the catalytic etherification of the platform molecule 5-(hydroxymethyl)furfural (HMF) to 5-(ethoxymethyl)furfural (EMF), a biofuel with an energy density close to that of gasoline (30 MJ/L) which also reduces emissions of NOx and SOx and solid particles respect to fossil-derived fuels. Catalytic performance was optimized modifying experimental parameters such as reaction time, temperature, and concentration of reagent employed. This process was carried out in batch reactors using ethanol 96% as solvent. Among different cation-exchange resins tested, Purolite CT275DR provided the fastest HMF conversion together with Purolite PD206, and the highest selectivity to EMF, achieving above 70% selectivity at 100 °C. Over time, strong acid sites favoured product hydrolysis opening the furan ring originating ethyl levulinate (EL) to the detriment of EMF selectivity. Purolite CT275DR was also utilised to realize the transformation from sugars directly to EMF in the same reaction medium, in a one-pot process, obtaining relevant results from fructose (37% HMF yield, 21% EMF yield after 5 h), but originating selectively ethylglucosides and ethylgalactosides in the presence of glucose and galactose, respectively, due to the absence of necessary Lewis acid sites to isomerize aldose and proceed with dehydration.Spanish Ministry of Economy and Competitiveness (RTI2018-94918-B-C44), FEDER (European Union) funds (UMA18-FEDERJA-171) and Malaga Universit

CDs and N-CDs preparation from xylose and xylose-enriched biomass liquors for methyl orange photocatalytic degradation.

CDs are newly discovered carbon nanoparticles that present unique properties. Each nanoparticle consists of a graphitic lattice core covered by a functionalized surface composed by several polar functional groups attached1,2. Due to this functionalization, CDs exhibit photoinduced electronic transference, fluorescence and up-conversion photoluminescence3. CDs have raised increasing attention for their undemanding synthesis procedure combined with the fact that they have been proved to be non-toxic and can be modified to reach satisfactory quantum yield values. A current tendency in the obtention of CDs is the pursuit of a synthesis method that fulfils the requirements of green chemistry but keeps production costs low. Therefore, CDs obtained from green precursors coming from biomass is an emergent research topic4,3,5,6,7. The most frequent and best-known method for CDs production is hydrothermal or solvothermal method7,3,2.The acidic conditions required by this method are commonly achieved using mineral acids such as HCl; nonetheless, the hydrothermal method is compatible with heterogeneous catalysis, which have been proved in this work. As a consequence of their photoluminescence and electron transfer properties, CDs can work as electron mediators, photosensitizers, as well as photocatalysts by themselves 10. It has been proved that CDs when photo excited are outstandingly good electron donors and electron acceptors, since either electron acceptors or electron donors are able to quench the photoluminescence emitted by CDs effectively 9.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Si-Al nanospheres for the valorization of galactose and agarose into 5-hydroxymethylfurfural.

5-hydroxymethylfurfural (HMF) is a compound that has gained attention to potentially substitute fossil resources in areas such as the polymer industry or the production of energy vectors. HMF is produced from the acid treatment of hexoses, such as glucose or galactose. In this sense, algae biomass has gained interest as it can be grown in both, sweet and salt water and their growth rate and CO2 fixation are several times higher than those of terrestrial plants. Red algae, which are rich in agarose, a galactose and 1,6-dehydrogalactose heteropolymer, can potentially be used as feedstock to produce HMF [1]. Hence, in this work, alumina supported nanospheres have been synthetised and employed as acid catalysts due to their high acidity and porosity that allows the selective conversion of these biomass derived compounds into valuable HMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influence of Lewis and Brønsted acid catalysts in the transformation of hexoses into 5-ethoxymethylfurfural

Several sulfonated polymers, which are typical Brønsted acid catalysts, have been employed in the production of two biofuels: 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) as main byproduct, and the catalytic results have been attributed to their different chemical and morphological properties. The Purolite CT275DR attained the best results from 5-hydroxymethylfurfural (HMF) with a 63% EMF yield after 16 h at 100 ◦C thanks to their more abundant superficial acid sites. Moreover, Purolite CT275DR was able to efficiently dehydrate and etherify fructose, with a total EMF plus EL yield of 65% after 24 h at 100 ◦C. When glucose or galactose were used as feedstock, alumina was utilized to provide Lewis acid sites, necessary for the transformation of aldoses in so- lution enabling a combined biofuel yield (EMF plus EL) of 40% from glucose after 24 h at 140 ◦C. With the study of the role of each catalyst, both Brønsted and Lewis acid catalysts (resin and alumina, respectively) were required to obtain considerable EMF yields from aldoses. The reutilization of the catalysts employed for 5 cat- alytic runs demonstrated that Purolite CT275DR suffers no appreciable loss of activity, but alumina showed progressive losses in activity in each cycle due to carbonaceous deposits and catalyst loss.Funding for open access charge: Universidad de Málaga / CBUA This research was funded by the Spanish Ministry of Innovation, Science and Universities (RTI2018-094918-B-C44), FEDER (European Union) funds (RTI2018-094918-B-C44 and UMA18-FEDERJA-171) and Malaga University. Authors thank to Universidad de M ́alaga/CBUA for funding for open access charge. C.G.S. acknowledges FEDER funds for her postdoctoral contract (UMA18-FEDERJA-171). B.T.O. acknowledges the Ministerio de Universidades for his predoctoral contract (FPU20/ 02334

Valorisation of glucose into biofuels and high value-added chemicals using zeolites as catalysts.

Hexose sugars can be valorised under acidic conditions to produce the platform chemical 5-hydroxymethylfurfural (HMF), which can be transformed in a broad spectrum of chemicals with applications as biofuels or monomers for polymers [1]. 5-ethoxymethylfurfural (EMF) is one of the derivatives of HMF useful as biofuel or fuel additive, produced usually from the etherification of HMF with ethanol. However, the high price of HMF is an important drawback for its use as feedstock for the production of EMF, which, together with the low yields and selectivity that are often attained by treating biomass or biomass derived compounds, are limiting its industrial application. In this work, several zeolites with different morphologies and chemical compositions have been employed as acid catalysts for the etherification reaction of HMF and ethanol to produce EMF, as well as the direct conversion of glucose into EMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Producción de 5-etoximetilfurfural desde azúcares derivados de la biomasa usando zeolitas en procesos de 1 y 2 pasos

En este trabajo se ha comprobado la efectividad de la zeolita beta (relación molar Si/Al= 10) en la isomerización de glucosa a fructosa y su deshidratación a HMF, y posterior eterificación a EMF, en un solo paso en etanol, y en dos pasos mediante un sistema bifásico agua-etanol-metilisobutilcetona (MIBK). Los resultados muestran selectividades del 70% en la isomerización de glucosa a fructosa en un paso (Figura 1), etapa intermedia en la producción de furanos desde glucosa. Sin embargo, en medio acuoso la deshidratación parece estar severamente desfavorecida. El uso de disolventes de menor polaridad (etanol) disminuye el balance de materia, debido a la promoción de procesos de polimerización. Asimismo, la ausencia de agua facilita la deshidratación de la hexosa y se alcanza un rendimiento de EMF a 3 h del 17%. Desafortunadamente, la deshidratación de fructosa para originar furanos no tiene lugar de forma preferencial sobre otros caminos de reacción que desembocan en la polimerización y formación de huminas, que reducen severamente la selectividad del proceso. La utilización de un sistema bifásico en el que se promueva la deshidratación de los azúcares, previa a la eterificación del HMF, puede ser más favorable respecto al método de producción de EMF desde azúcares o material biomásico en un solo paso. Aplicando un método en 2 pasos, en el primer paso se han encontrado rendimientos en la deshidratación de glucosa a HMF del 60% (Figura 2). La fase orgánica, donde se encuentra la mayor parte del HMF, puede recuperarse y someterse a una segunda etapa, donde tiene lugar la eterificación del HMF, lográndose rendimientos finales de EMF del 37%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Ministerio de Ciencia, Innovación y Universidades, a la Unión Europea (Fondos Feder: RTI2018-094918-B-C44 y UMA18-FEDERJA-171

Recent Advances in Mechanochemical Pretreatment of Lignocellulosic Biomass

Biorefineries are industrial facilities where biomass is converted into chemicals, fuels and energy. The use of lignocellulose as raw material implies the development of pretreatments to reduce its recalcitrant character prior to the processes that lead to the synthesis of the products of interest. These treatments are based on physico-chemical processes where it is necessary to use acids, bases, oxidants, and high pressure and temperature conditions that lead to the depolymerization of lignocellulose at the expense of generating a series of streams that must be treated later or to the production of by-products. In recent years, mechanochemistry is becoming relevant in the design of processes that help in the depolymerization of lignocellulose. These mechanochemical processes are being used in combination with chemicals and/or enzymes, allowing the use of minor loads of reagents or enzymes. In this review, the advances achieved in the use of mechanochemistry for treating lignocellulosic biomass or cellulose will be presented, with special emphasis on how these mechanochemical processes modify the structure of lignocellulose and help subsequent treatments. It will focus on using ball milling or extrusion, ending with a section dedicated to future work needed to implement these technologies at the industrial level.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) and B.T.O. acknowledges Ministerio de Universidades for his predoctoral contract. Partial funding for open access charge: Universidad de Málag

Application of zeolites for the production of biofuels and furans from hexose sugars in ethanol.

The use of zeolites as catalysts in the transformation of glucose and 5-hydroxymethylfurfural (HMF) into 5-ethoxymethylfurfural (EMF) was evaluated. The behaviour of the catalysts could be explained by their morphology, composition, acid properties and chemical coordination of the active sites. The progress of the reaction was followed by High Performance Liquid Chromatography (HPLC) and 13C Nuclear Magnetic Resonance (NMR). Several intermediates were identified, and a reaction path is proposed. Different cosolvents were also employed in this study to enhance the selectivity towards different possible valuable compounds, and they were found to have a positive influence for the production of EMF and furfural.Funding for open access charge: Universidad de Málaga / CBU

Obtención de 5-hidroximetilfurfural a partir de agarosa y galactosa usando nanoesferas de sílica-alúmina.

En los últimos años, existe un gran interés en la obtención de moléculas plataforma mediante el uso de materias primas renovables. El 5-hidroximetilfurfural (HMF), una de estas moléculas plataforma, es un compuesto valioso para la producción de monómeros para polímeros y vectores energéticos y se obtiene de la deshidratación de hexosas en medio ácido. Las algas son una fuente de biomasa rica en carbohidratos que crecen, tanto en aguas dulces como marinas, mucho más rápido que las plantas terrestres, y no necesitan tierras de cultivo fértiles y limitadas, por lo que no competirían con la industria alimentaria. Uno de los polisacáridos presentes en las algas es la agarosa, cuya hidrólisis produce galactosa, una hexosa que puede usarse como precursora de HMF en presencia de un catalizador ácido. En este trabajo se han sintetizado una serie de nanoesferas mesoporosas de óxidos de aluminio y silicio para valorizar los componentes presentes en las algas hacia HMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech