Examinando por Autor "Paniagua, Marta"

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Aldol condensation of furfural and methyl isobutyl ketone over Zr-MOF-808/silica hybrid catalysts
(Elsevier, 2023) Morales, Gabriel; Paniagua, Marta; Flor, Daniel de la; Sanz, María; Leo, Pedro; López-Aguado, Clara; Hernando, Héctor; Orr, Samantha A.; Wilson, Karen; Lee, Adam F.; Melero, Juan A.
Mesoporous silica-supported Zr-MOF-808 catalysts have been synthesised and tested in the aldol condensation of (biomass-derived) furfural and methyl isobutyl ketone to bio-jet fuel precursors. Growth of Zr-MOF-808 nanocrystals over silica scaffolds results in well-dispersed Zr species which confer strong Lewis acidity as determined by FTIR of chemisorbed pyridine. Hybrid Zr-MOF-808/silica materials exhibit higher condensation activity than the unsupported crystalline Zr-MOF-808 (which is also prone to rapid deactivation). Textural properties of the silica support strongly influence the catalytic performance, with a high surface area and sufficiently large mesopore desirable. In the screening, the optimum Zr-MOF-808/MCM-41 catalyst delivered 68 % furfural conversion and 90 % selectivity to the C11 aldol adduct, 1-(furan-2-yl)-5-methylhex-1-en-3-one, at 130 ◦C and a furfural:Zr mass ratio of 150:1. Although more stable than the pure Zr-MOF-808, the Zr-MOF-808/MCM-41 also suffered significant deactivation over successive condensation reactions due to strongly adsorbed organic residues, however this was largely ameliorated by decreasing the furfural:Zr ratio to 75:1, which also led to an outstanding catalytic performance (100 % furfural conversion and adduct selectivity), likely because of the suppression of furfural polymerization.
Beta zeolite as an efficient catalyst for the synthesis of diphenolic acid (DPA) from renewable levulinic acid
(Elsevier, 2022) Morales, Gabriel; Melero, Juan A.; Paniagua, Marta; López-Aguado, Clara; Vidal, Nora
The solvent-free production of diphenolic acid (DPA) from levulinic acid (LA) and phenol is studied using readily accessible commercial acid zeolites like Beta, ZSM-5 and USY. Acid zeolites are cost-effective catalysts, and they are herein benchmarked against the sulfonic acid resins Amberlyst-15 and Nafion®, and sulfonic acidfunctionalized SBA-15 silicas. Beta zeolite with a moderate aluminum content (H-Beta 19, Si/Al=23) presents the best catalytic performance, owing to the right combination of the shape selectivity effect conferred by the BEA structure, and the adequate balance of acidity (Al content and speciation). The optimization of the reaction conditions is tackled by the response surface methodology using as optimization factors the temperature, the PhOH:LA molar ratio, and the catalyst loading. Thus, under the optimized reaction conditions (12 mmol LA, 140 ᵒC, 0.30 g catalyst loading, PhOH:LA = 6:1 mol), over 70% yield to DPA with LA conversion around 77% is obtained after 72 h. Despite the catalyst shows a progressive activity decay in successive uses because of fouling, removal of the formed organic deposits by calcination in air allows restoring the starting catalytic performance.
Boosting the activity of UiO-66(Zr) by defect engineering: efficient aldol condensation of furfural and MIBK for the production of bio jet-fuel precursors
(Royal Society of Chemistry, 2024-05-30) Sanz, María; Leo, Pedro; Palomino, Carlos; Paniagua, Marta; Morales, Gabriel; Melero, Juan A.
The production of jet-fuel precursors from furfural via aldol-condensation with methyl-isobutyl ketone (MIBK) over defect-engineered UiO-66(Zr) catalysts is presented. The catalysts are prepared using formic acid (FA), trifluoroacetic acid (TFA) and HCl as synthesis modulators, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance. An extensive characterization of the modified catalysts by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), transmission electron microscopy, and FTIR spectroscopy of adsorbed acetonitrile, confirmed the incorporation of missing-linker and missing-node defects within the MOF structure, enabling the explanation of the enhancement in the catalytic process. The analysis of the reaction kinetics evidences that, working under moderate temperature conditions, conversion of furfural and selectivity to the desired adduct (FuMe) close to 100% can be achieved, avoiding the formation of degradation and bulkier compounds. Finally, despite the generation of defects within the UiO-66(Zr) structure, the resultant catalyst displays good reusability in low furfural concentration mediums.
Dehydration of C6-monosaccharides to 5-hydroxymethylfurfural in dimethyl sulfoxide using sulfonic acid heterogeneous catalysts
(Elsevier, 2014) Morales, Gabriel; Melero, Juan A.; Paniagua, Marta; Iglesias, Jose; Hernández, Blanca; Sanz, María
The use of sulfonic acid-functionalized heterogeneous catalysts in conjunction with the use of dimethyl sulfoxide (DMSO) as solvent in the catalytic dehydration of C6 monosaccharides into 5-hydroxymethylfurfural (HMF) has been shown as an interesting alternative route for the production of this platform molecule. Amberlyst-70 was selected as the most active catalyst, ascribing its higher catalytic performance to its higher concentration of sulfonic acid sites, as compared with the rest of the evaluated catalysts. Starting from fructose, the use of Amberlyst-70 led to 93 mol% yield to HMF after just 1h. For glucose, a much more difficult reaction, reaction conditions (time, temperature and catalyst loading) where optimized for Amberlyst-70 via response surface methodology leading to a maximum HMF yield of 33 mol% at 147ºC, 23 wt% catalyst loading based on glucose loading and 24h. Noticeably, DMSO promotes the dehydration of glucose into anhydroglucose, which acts as a reservoir of substrate facilitating the production of HMF, since it reduces the extent of side-reactions. A study of catalyst¿s reuse, without regeneration treatment, evidenced a gradual decay in catalytic activity, though not very significant.
Efficient Self-Condensation of Cyclohexanone into Biojet Fuel Precursors over Sulfonic Acid-Modified Silicas: Insights on the Effect of Pore Size and Structure
(ACS, 2024) Martín, Antonio; Arribas-Yuste, Esther; Paniagua, Marta; Morales, Gabriel; Melero, Juan A.
Mesoporous silica materials with different pore structures and sizes have been used for supporting aryl sulfonic acid catalytic sites via a postsynthetic grafting approach. The synthesized materials have been evaluated in the solventless acid-catalyzed self-condensation of cyclohexanone (CHO) to obtain the corresponding C12 adducts. These compounds display great potential as oxygenated fuel precursors as they can be transformed into jet fuel range alkanes in a subsequent hydrodeoxygenation process. In this work, the synthesized catalysts have displayed high selectivity values toward monocondensed compounds (>95%), thus limiting the formation of undesired heavier condensation products, together with CHO conversion values in the range 20–40% after 2 h of reaction at 100 °C. The structural and textural properties of the supports play an important role in the catalytic performance. Moreover, the activity per acid center is correlated with the textural properties of the supports, indicating that a lower surface density of the anchored aryl sulfonic groups affords an improvement in their specific activity. Finally, the benefit of using supports with large pore sizes and open structures, which limit the fouling of the catalysts by organic deposits, is demonstrated in a stability and reusability test.
Insights into the influence of feed impurities on catalytic performance in the solvent-free dimerization of renewable levulinic acid
(Elsevier, 2023) Paniagua, Marta; Morales, Gabriel; Melero, Juan A.; García-Salgado, Daniel
Bio-jet fuel precursors can be produced from the solvent-free aldol dimerization of levulinic acid. The influence of the most common impurities accompanying the levulinic acid produced in lignocellulosic biorefineries (sulfuric acid, water, formic acid, and furfural) has been studied on the catalytic performance of different kinds of heterogeneous acid catalysts: (i) sulfonic acid-based materials, such as propyl-sulfonic acid-modified SBA-15, and the sulfonic acid resin Amberlyst-70, and (ii) commercial acid zeolites, such as H-Beta-19 and H-Beta-75. Furfural is the impurity that produces the greatest detrimental effect on the performances of all the catalysts tested. Catalyst deactivation is observed due to the formation of organic deposits on the catalyst surface (identified by TGA and acid-base titration), phenomenon that is accentuated when furfural is present in the reaction medium. Amberlyst-70 can recover almost totally the initial catalytic activity with a regeneration step based on washing with an acid solution under reflux. For Beta zeolites, the original activity of the catalyst can be easily and totally recovered through a regeneration process by calcination. H-Beta-19 zeolite is shown as the most suitable catalyst for the aldol dimerization of renewable LA, as its activity is not significantly affected by the presence of most of the impurities in the levels herein analyzed. In addition, a simultaneous mixture of all the impurities produces a synergistic effect, even improving the initial activity of the H-Beta-19 zeolite as a consequence of the sulfuric acid contribution to the catalytic effect.
Oxygenated compounds derived from glycerol for biodiesel formulation: Influence on EN 14214 quality parameters
(ELSEVIER, 2010) Melero, Juan A.; Vicente, Gemma; Morales, Gabriel; Paniagua, Marta; Bustamante, Javier
The methyl esters of fatty acids (biodiesel) obtained via transesterification of vegetable oils or animal fats are an alternative to current fossil fuels. A large amount of glycerol as a by-product is generated in this process and new applications for this surplus need to be found. Thus, the transformation of glycerol into branched oxygen-containing compounds could be an interesting solution to provide an outlet for increasing glycerol stocks. In this work, several oxygenated compounds, obtained by transformation of glycerol via etherification, esterification and acetalisation, have been assessed as components for biodiesel formulation. Different quality parameters have been evaluated following the procedures listed in the EN 14214 European Standard for biodiesel specifications. These parameters have been correlated with the amount of oxygenated derivate present in the biodiesel. The best performance as component for biodiesel formulation has been achieved by the mixture of ethers produced via etherification of glycerol with isobutylene. The addition of these compounds has not only improved the low temperature properties of biodiesel (i.e. pour point and cold filter plugging point) and viscosity, but also did not impair other important biodiesel quality parameters analyzed. Although most of the studied oxygenated derivates do not significantly improve any biodiesel property, they do not exert a significant negative effect either. Furthermore, all of them allow an enhancement of overall yield in the biodiesel production. Nevertheless, further improvement could be addressed with a better purification to reduce the presence of non-desired impurities such as diisobutylenes and unreacted acetic acid, which have a negative influence especially in acid number and oxidation stability.
Sulfonic Mesostructured SBA-15 Silicas for the Solvent-Free Production of Bio-Jet Fuel Precursors via Aldol Dimerization of Levulinic Acid
(ACS, 2021) Paniagua, Marta; Cuevas, Florentina; Morales, Gabriel; Melero, Juan A.
Sulfonic acid-functionalized mesostructured silicas have been evaluated in the solvent-free aldol dimerization of biomass-derived levulinic acid into bio-jet fuel precursors. These compounds produce branched alkanes in a subsequent hydrodeoxygenation process, with suitable properties for being a renewable alternative to conventional fossil aviation fuels. The combination of activity and selectivity toward the desired condensation products achieved over sulfonic acid-functionalized SBA-15 materials is superior to those displayed by other commercial solid acid catalysts. Enhanced textural properties provided by the mesoporous SBA-15 support contribute to such improved catalytic performance. The strength and loading of the mesoporous silica-supported sulfonic acid moieties are also important factors affecting the catalytic performance of the materials. Reaction conditions (temperature, time, and catalyst loading) have been optimized for propylsulfonic acid-functionalized mesostructured silica (Pr-SBA-15) by means of a response surface methodology, leading to a maximum yield to levulinic acid dimerization products of 58.4% (145 °C, 0.15 g of catalyst, 24 h, no solvent). Under these reaction conditions, conversion of levulinic acid is 61.1%, indicating excellent selectivity toward bio-jet fuel precursors. A small catalytic activity decay has been detected in reutilization experiments, attributed to the formation of organic deposits onto the catalyst surface. A mild acid washing of the catalyst allowed a significant recovery of the initial activity.
Synthesis of oxygenated compounds for fuel formulation: Etherification of glycerol with ethanol over sulfonic modified catalysts
(ELSEVIER, 2011-12) Melero, Juan A.; Vicente, Gemma; Paniagua, Marta; Morales, Gabriel; Muñoz, Patricia
The present study is focused on the etherification of glycerol with anhydrous ethanol over arenesulfonic acid-functionalized mesostructured silicas to produce ethyl ethers of glycerol that can be used as gasoline or diesel fuel components. Within the studied range, the best conditions to maximize glycerol conversion and yield towards ethyl-glycerols are: T = 200ºC, ethanol/glycerol molar ratio = 15/1, and catalyst loading = 19 wt.%. Under these reaction conditions, 74% glycerol conversion and 42% yield to ethyl ethers have been achieved after 4 h of reaction but with a significant presence of glycerol by-products. In contrast, lower reaction temperatures (T=160ºC) and moderate catalyst loading (14 wt.%) in presence of a high ethanol concentration (ethanol/glycerol molar ratio = 15/1) are necessary to avoid the formation of glycerol by-products and maximize ethyl-glycerols selectivity. Interestingly, a close catalytic performance to that achieved using high purity glycerol has been obtained with low-grade water-containing glycerol.
Techno-Economic Assessment of Conceptual Design for Gamma-Valerolactone Production over a Bifunctional Zr–Al–Beta Catalyst
(ACS, 2022) López-Aguado, Clara; Martínez del Monte, Daniel; Paniagua, Marta; Morales, Gabriel; Melero, Juan A.
Gamma-valerolactone (GVL) is a promising precursor for the preparation of biofuels and fuel-range hydrocarbons. This work shows the conceptual design of a process for the production of GVL from levulinic acid by means of catalytic transfer hydrogenation (CTH) over a bifunctional Zr–Al–Beta catalyst using an excess of isopropyl alcohol (IPA) acting as the hydrogen donor and solvent. The process is advantageously conducted in the liquid phase under moderate conditions, avoiding the use of high-pressure hydrogen. A techno-economic analysis of the process is presented, considering a production scale of 368.9 kg/h of GVL (ca. 85.5% GVL mass yield from levulinic acid). Such an analysis considers two main process sections, namely, (i) the reaction unit and (ii) the downstream purification section designed to achieve 99 wt % GVL purity together with 95% recovery of unreacted IPA. The analysis provides an investment of 6.4 MM€ with 7.5 MM€ annual operational costs (74% corresponding to reactants). The Minimum Selling Price for GVL is estimated to be 3076 €/ton. Finally, cost sensitivity analyses revealed the high IPA purchasing price and losses in side reactions (autoetherification) as the main obstacles to obtain a GVL competitive market price through this approach.
Tight control of cellulose depolymerization towards glucose in organic electrolyte solutions
(Elsevier, 2014) Iglesias, Jose; Melero, Juan A.; Paniagua, Marta; Andreola, M. Teresa; Barragán, Elena
Organic electrolyte solutions (OES) prepared by combination of an ionic liquid (1-Butyl-3- methylimidadozium chloride) with dimethyl sulfoxide (DMSO) have been tested as reaction media for the controlled hydrolysis of cellulose. The use of these mixtures is justified because of they provide an excellent media for the solubilization of cellulose, while saving a significant fraction of expensive ionic liquids. Cellulose hydrolysis tests performed in presence of these OES media have been used to determine the influence of several important operational reaction variables. These include the determination of the influence of the mineral acid used as catalyst, the reaction temperature, the amount of water as well as the addition rate of the same to the reaction media in the production of glucose. While the presence of mineral acid is mandatory, not only to accomplish cellulose hydrolysis, but to maintain the polysaccharide under solution, the amount of water and its addition rate is crucial to provide a proper control in the hydrolytic cleavage of 1,4-glucoside bondings between glucose units. While low amounts of water hampers the cellulose hydrolysis rate and produces large yields of by products coming from the dehydration of glucose, the opposite leads to the precipitation of the polysaccharide. In both cases a low yield towards glucose is achieved. In this way, the control of the water concentration in the reaction media, together with the use of an appropriate reaction temperature, allows maximizing the production of glucose with an outstanding selectivity towards this monosaccharide, leading to the transformation of more than 90% of the starting dissolved cellulose into glucose. This methodology can be easily adapted to the transformation of other cellulosebased materials, such as biomass-feedstocks like wheat straw or paper-derived materials.