Catalytic transfer hydrogenation of furfural to furfuryl alcohol over calcined MgFe hydrotalcites

Catalytic transfer hydrogenation is an alternative catalytic approach for the reduction of carbonyl groups, instead of the use of dihydrogen gas. In this sense, a series of catalysts has been prepared by thermal treatment of layered double hydroxides, hydrotalcite type, of Mg(II) and Fe(III), with different Mg/Fe molar ratios. The resulting mixture of metal oxides was characterized by X-ray diffraction, TEM, N2 adsorption-desorption, CO2-TPD, NH3-TPD and XPS, and then catalysts were tested in the Meenwein-Ponndorf-Verley (MPV) reduction of furfural to obtain furfuryl alcohol. The catalytic results show that the catalysts with a Mg/Fe molar ratio of 3 allows reaching the highest furfural conversion at a lower reaction time, with a FOL yield close to 90% after 6 h of reaction at 443 K. The detailed analysis of these catalysts also revealed that the basicity has a more predominant role in the MPV reaction than acid sites.Spanish Ministry of Innovation, Science and Universities (Project RTI2018-094918-B-C44) and FEDER (European Union) funds. J.A.C. and C.G.S. thank University of Malaga for contracts of PhD incorporation. R.M.T. thanks to the Spanish Ministry of Economy and Competitiveness (IEDI-2016-00743) for the financial support within the I3 program

Tailoring basic and acidic properties of MgAl hydrotalcite by fluoride anions: Effect on glycerol oligomerisation

In this work, two families of catalysts based on mixed metal oxides derived from MgAl hydrotalcites were synthesized with a Mg/Al molar ratio of 3. On the one hand, in the first family, the fluoride anion was incorporated in the interlayer space by using ammonium fluoride, exploiting the “memory effect” characteristic of hydrotalcites. In the second family, fluoride anions substituted oxides anions in the layer, incorporating directly them during the precipitation of hydroxides, by using cryolite as a precursor for both fluorine and aluminium. The hydrotalcites were transformed into mixed metal oxides by thermal treatment and tested in the glycerol etherification reaction at 230 ºC, in a batch reactor at atmospheric pressure. The hydrotalcites and the corresponding mixed metal oxides were characterized by different experimental techniques, such as X-ray diffraction (XRD), elemental analysis (CHF), N2 sorption at -196ºC, thermogravimetric analysis (ATD-TG), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of CO2 and NH3 (CO2-TPD and NH3-DTP) and solid state nuclear magnetic resonace (ssNMR) of 19F. It was found that the mixed metal oxides prepared from hydrotalcites, where fluorine was incorporated in the synthesis step using cryolite, achieved the maximum conversion values and complete selectivity towards diglycerol. Diglycerols were the unique detected products and, in some cases, the formation of triglycerols was also detected.Funding for open access charge: Universidad de Málaga / CBU

Synthesis of hollow mesoporous spheres modified with ZrO2 and non-noble metals for the one-step reaction of furfural to 1,4-pentanediol.

The synthesis of these porous SiO2 nanospheres modified with ZrO2 was based on a previous work to which different metal loadings were co-precipitated to obtain a family of catalysts ranging from 15% Cu to 15% Co. For the synthesis of the nanospheres, SiO2 of pore size 0.2-0.3 μm was used, previously dried in an oven and avoiding contact with the atmosphere. Toluene was added and once the silica was dispersed, Zr n-propoxide was added taking care that the atmosphere was kept inert with a continuous stream of He. It was stirred at 115°C for 12 hours. The solid was centrifuged, filtered with a Buchner funnel, washed with toluene and left to dry in an oven at 60°C. For the incorporation of the metal load, the determined amount of nitrate of the metal was dissolved in 100 mL of deionised water and then, the support was added. The pH of the solution was increased adding a NaOH solution to reach a pH of 9 and aged for at least one hour. Filtration is carried out again with a Büchner funnel, the solid is dried and calcined in an oven at about 500°C for 2 hours. EDX images show that the synthesis has generated spheres where Zr, Co and Cu are covering the silica particles. Regarding to the porosity of the catalysts, it can be seen how the introduction of metals decreases both, the BET surface area and the pore volume and size, with Cu being the metal that most reduces these parameters, which was to be expected since its atomic ratio is lower than Co atomic ratio. The catalytic tests were carried out at 170°C and (3-48 h) using different H2 pressures (1-4 MPa). The catalytic results show an almost total conversion of furfural from 3 hours of reaction and an average yield of 10-15% of 1,4-PD, obtaining the highest yield in pentanediols (1,4-PD+1,5-PD) for Zr-HMS-7.5Cu7.5Co catalyst. Other products of interest such as furfuryl alcohol (FOL), tetrahydrofurfuryl alcohol (THFA), 1-pentanediol (1-Pent), 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) are also obtained

Zr-HMS modificado con Cu y Co para la obtención de productos de valor añadido a desde la hidrogenación de furfural.

De los pentanodioles obtenidos de la hidrogenación del furfural, con el empleo de catalizadores basados en metales no nobles, la bibliografía nos muestra un gran volumen de trabajos centrados en 1,2-pentanodiol, mientras que para 1,5-pentanodiol hay menos estudios que consigan rendimientos destacables. En cuanto al 1,4-pentanodiol, los trabajos publicados son escasos y/o muestran rendimientos bajos. Los resultados de este estudio, además de 1,2-pentanodiol (1,2-PD), muestran rendimientos en 1,5-pentanodiol (1,5-PD) y en 1,4-pentanodiol (1,4-PD) muy interesantes. En este trabajo se estudia el efecto en la catálisis de la modificación con metales no nobles de una estructura tipo HMS dopada con zirconio en su superficie externa. La familia de catalizadores se ha denominado como ZrHMS-xCu-xCo, dependiendo de la proporción molar de los metales. Los primeros datos de la caracterización previa a los ensayos catalíticos señalan una relación entre la estructura de los catalizadores y su actividad catalítica, además de entre sus propiedades físico-químicas. Los estudios catalíticos se realizaron en un reactor a presión tipo batch durante 22 h, a 170 ºC y 4 MPa de H2 (Figura 1). En todos los ensayos se pudo observar una conversión completa de furfural y un rendimiento a pentanodioles de hasta un 22%, siendo los catalizadores ZrHMS-15Cu y ZrHMS-7.5Cu-7.5Co los más selectivos a 1,4-pentanodiol. Por otra parte, se observa cómo estos catalizadores son capaces de obtener otros productos de interés como el alcohol tetrahidrofurfurílico (THFA) y 2-metilfurano (2MF). La cinética de la reacción se llevó a cabo entre 3 y 48 h, se modificaron otros parámetros como la presión de H2 y la calidad del furfural empleado. Por las imágenes tomadas por TEM (Figura 2) se puede comprobar que, aunque la forma no es del todo esférica, la dispersión del Zr es homogénea por toda la superficie del catalizador, así como las proporciones de los metales Cu y Co corresponden a lo previsto teóricamente.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Porous SiO2 Nanospheres Modified with ZrO2 and Their Use in One- Pot Catalytic Processes to Obtain Value-Added Chemicals from Furfural

Porous SiO2 nanospheres have been modified with different proportion of ZrO2 to obtain catalysts with Si/Zr molar ratio between 2.5 and 30. These materials were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2 adsorption-desorption at -196 ºC, X-ray photoelectron spectroscopy and pyridine and 2-6-dimethylpyridine thermoprogrammed desorption. The characterization of these catalysts reveals that the incorporation of a high proportion of Zr favors the formation of Lewis acid sites, which are implied in catalytic transfer hydrogenation processes, whereas the low Brönsted acidity promote dehydration reaction, in such a way that it is possible to obtain a wide range of products from FUR through consecutive reactions, such as furfuryl alcohol, i-propyl furfuryl ether, i-propyl levulinate and γ-valerolactone in a range of temperature of 110-170 ºC between 1-6 h of reaction.Spanish Ministry of Science, Innovation and Universities:RTI2018‐94918‐B‐C44; FEDER (European Union) funds: RTI2018‐94918‐B‐C44 and UMA18-FEDERJA-171; University of Malaga; Junta de Andalucía; Funding for open access charge: Universidad de Málaga/CBU

Nanoesferas porosas de SiO2 dopadas con Zr y su uso en procesos catalíticos one-pot para la obtención de productos de alto valor añadido desde furfural

En el presente trabajo, se ha estudiado la modificación de nanoesferas porosas de SiO2 con diferente proporción de Zr para obtener catalizadores con relaciones molares Si/Zr entre 2.5 y 30. Estos materiales se han caracterizado mediante difracción de rayos X, microscopía electrónica de transmisión, microscopía electrónica de barrido, adsorción-desorción de N2 a -196 ºC, espectroscopía de fotoelectrones de rayos X y desorción termoprogramada de piridina y 2-6-dimetilpiridina. La caracterización de estos catalizadores revela que la incorporación de una alta proporción de Zr favorece la formación de sitios ácidos de Lewis, implicados en los procesos de hidrogenación por transferencia catalítica, mientras que la baja acidez de Brönsted promueve la reacción de deshidratación, de tal manera que es posible obtener una amplia gama de productos a partir del FUR mediante reacciones consecutivas, como el alcohol furfurílico (FOL), isopropil furfuril éter (IpFE), levulinato de isopropilo (IpL) y γ-valerolactona (GVL) en un rango de temperatura de 110-170 ºC, después de 1-6 h de reacción. Los ensayos catalíticos muestran que el aumento de la acidez mejora la conversión del FUR, obteniéndose tanto isopropil furfuril éter como levulinato de isopropilo en mayor proporción, a la menor temperatura de reacción (110ºC). Sin embargo, se obtiene un mayor rendimiento de FOL y GVL cuando la temperatura es de 170ºC. Cabe destacar que la proporción de productos no detectados aumenta cuando disminuye la relación molar Si/Zr en los catalizadores y se aumenta la temperatura, debido a la polimerización del propio FUR y FOL en presencia de sitios ácidos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech Ministerio de Ciencia, Innovación y Universidades (RTI2018-94918-B-C44) Fondos FEDER (Unión Europea) (UMA18-FEDERJA-171

Nb-Based Catalysts for the Valorization of Furfural into Valuable Product through in One-Pot Reaction

Nb-based catalysts supported on porous silica with different textural properties have been synthesized, characterized, and tested in the one-pot reaction of furfural to obtain valuable chemicals. The catalytic results reveal that the presence of fluoride in the synthesis, which limits the growing of the porous silica, limits diffusional problems of the porous silica, obtaining higher conversion values at shorter reaction times. On the other hand, the incorporation of NbOx species in the porous silica provides Lewis acid sites and a small proportion of Brönsted acid sites, in such a way that the main products are alkyl furfuryl ethers, which can be used as fuel additives