Examinando por Autor "Morales, Gabriel"

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Acid-catalyzed production of biodiesel over arenesulfonic SBA-15: insights into the role of water in the reaction network
(Elsevier, 2014) Melero, Juan A.; Bautista, L. Fernando; Morales, Gabriel; Iglesias, Jose; Sánchez-Vázquez, Rebeca
This work presents a systematic approach to understand the effect of the presence of water in highly acidic crude palm oil-typical conditions of low grade oleaginous feedstock- on the performance of arene-SO3H-SBA-15 catalyst in the batch-production of biodiesel. The addition of small amounts of water (1 wt%) to the reaction medium led to a clear reduction of the observed yield to fatty acid methyl esters (FAME), being this decay usually attributed to the highly hydrophilic nature of arenesulfonic acid groups, and the associated difficulties of hydrophobic substrates to access these catalytic acid sites. However, the addition of larger amounts of water -up to 10 wt%- did not cause a proportional decay in the yield to FAME, but a higher production of free fatty acids (FFA). This is attributed to the promotion of acid-catalyzed hydrolysis of both starting triglycerides and formed FAME. The net result is not only a significant reduction of the final FAME yield, but also the appearance of high acid values, i.e. FFA contents, in the final biodiesel. Consequently, the overall process is simultaneously affected by transesterification, esterification and hydrolysis reactions, all of them catalyzed by Brønsted acid sites and dependent on the reaction conditions -temperature and water concentration- to different extents. Several strategies devoted to manage such behavior of sulfonic acid-modified SBA-15 catalysts in presence of water, aiming to maximize FAME yield while minimizing FFA content, have been explored: (1) minimization of the water content in the reacting media by pre-drying of feedstock and catalyst; (2) addition of molecular sieves to the reacting media as water scavengers, (3) hydrophobization of the catalyst surface to minimize the water uptake by the catalyst; and (4) use of a decreasing reaction temperature profile in order to first promote transesterification at high temperature and then reduce the temperature to keep at a minimum the hydrolysis of formed FAME. All these strategies resulted in an improvement of the catalytic performance, especially the use of a decreasing temperature profile. The results showed by the latter strategy open new possibilities and reaction pathways in which readily available, low-grade, cheap oleaginous feedstock with high water and FFA contents can be efficiently converted into biodiesel.
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.
Aqueous-sensitive reaction sites in sulfonic acid-functionalized mesoporous silicas
(ELSEVIER, 2008) Morales, Gabriel; Athens, George; Chmelka, Bradley F.; van Grieken, Rafael; Melero, Juan A.
Local differences in surface hydrophilicities/hydrophobicities of propyl- and arene-sulfonic-acid modified mesoporous silica and organosilica catalysts have been compared and correlated with their bulk catalytic properties for aqueous-sensitive organic reactions. Syntheses of propyl- and arene-SO3H-modified mesoporous silicas and organosilicas yield materials with different hydrophilicities, especially when ethylsiloxane moieties are incorporated into the silica frameworks. Solid-state two-dimensional (2D) 13C{1H} and 29Si{1H} heteronuclear correlation (HETCOR) NMR spectra prove that the incorporation of hydrophobic ethylsiloxane groups into functionalized mesoporous silica frameworks result in reduced interactions of adsorbed water with the silica framework in general and, importantly, in the immediate vicinities of the SO3H active sites. The hydrophilic/hydrophobic character of the surface, as well as the active site properties depend on the functional species attached. Propyl-sulfonic acid moieties are less acidic but more hydrophobic than arene-SO3H species, leading to superior overall activities for water-mediated acid-catalyzed organic reactions. The etherification of vanillyl alcohol (4-hydroxy-3-methoxybenzylalcohol) with 1-hexanol to yield 4-hydroxy-3-methoxybenzyl-1-hexyl ether is shown to proceed significantly more effectively on SO3H-modified mesoporous organosilicas, compared to wholly siliceous mesoporous supports. The correlation of macroscopic adsorption and reaction results with 2D NMR measurements allows the hydrophilic/hydrophobic surface properties of the mesoporous support to be optimized with respect to water-retention capacities and activities for water-sensitive organic reactions.
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.
Biodiesel production from crude palm oil using sulfonic acid-modified mesostructured catalysts
(ELSEVIER, 2010) Melero, Juan A.; Bautista, L. Fernando; Morales, Gabriel; Iglesias, Jose; Sánchez-Vázquez, Rebeca
Biodiesel production from crude palm oil containing high percentage of free fatty acids over sulfonic acid-functionalized SBA-15 materials (propyl-SO3H, arene-SO3H, perfluoro-SO3H) has been studied. The catalytic results showed that sulfonic acid-modified mesostructured materials were more active than conventional ion-exchange sulfonic resins (Amberlyst-36 and SAC-13) in the simultaneous esterification of free fatty acids and transesterification of triglycerides with methanol. The reusability of the catalysts was also investigated showing high stability for propyl-SO3H and arene-SO3H-modified mesostructured materials. In contrast, ionic exchange sulfonic acid resins displayed low conversion rates, being stronger this decay of activity in the second consecutive catalytic run. Interestingly, perfluorosulfonic acid-functionalized SBA-15 sample yielded a dramatic loss of activity indicating that Si-O-C bonding is not stable under the reaction conditions as compared with Si-C bond present in propyl-SO3H and arene-SO3H catalysts. Further functionalization of arene-SO3H SBA-15 catalyst with hydrophobic trimethylsilyl groups enhanced its catalytic performance. This material was able to produce a yield to FAME of ca. 95 % as determined by 1H NMR in four hours of reaction with a moderate methanol to oil molar ratio (20:1), 140 ºC and a catalyst concentration of 6 wt% referred to starting oil.
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.
Continuous production of biodiesel from low grade feedstock in presence of Zr-SBA-15: Catalyst performance and resistance against deactivation
(Elsevier, 2014) Iglesias, Jose; Melero, Juan A.; Bautista, L. Fernando; Morales, Gabriel; Sánchez-Vázquez, Rebeca
Zirconium-containing SBA-15 materials have been used in the production of fatty acid methyl esters from low grade oleaginous feedstock. Its resistance against deactivation has been assessed by means of studying the effect of conventional impurities present in lipid wastes over the catalytic performance of this material. Alkaline metal cations like potassium could interact with Brønsted acid sites, causing their neutralization by ion exchange and a limited, but not complete, deactivation of the material. Additionally, organic unsaponifiable compounds like retinoids or phospholipids - being studied in this work as retinol and lecithin, respectively - strongly interact with the catalyst surface, leading to a strong deactivation of the material, though reversible, since they are fully regenerated by calcination in air. Catalytic assays in continuous mode in a fixed bed reactor suggest a higher resistance of Zr-SBA-15/bentonite pellets against catalyst deactivation. Bentonite clay, which has been used as binding agent for the preparation of the particulate catalyst, seems to be responsible for this behavior, acting as poison scavenger and preventing the access of the impurities to the catalytic acid sites and consequently their deactivation.
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.
Etherification of benzyl alcohols with 1-hexanol over organosulfonic acid mesostructured materials
(ELSEVIER, 2006) van Grieken, Rafael; Melero, Juan Antonio; Morales, Gabriel
Etherification of benzyl alcohols with 1-hexanol was performed in liquid phase over propyl- and arene-SO3H modified mesostructured SBA-15 silica. H2O TPD measurements indicate a stronger interaction of arenesulfonic acid sites with water molecules than that occurring in propylsulfonic groups. Hence, the higher catalytic activity of propylsulfonic modified SBA-15 material is related to the more hydrophobic microenvironment of -SO3H sites which reduces the acid site deactivation associated with adsorption of water generated during the reaction. Moreover, propyl- and arene-sulfonic functionalized SBA-15 material show a clear improvement of the catalytic performances as compared to other commercial homogeneous and heterogeneous acid catalysts in this particular reaction.
Friedel Crafts acylation of aromatic compounds over arenesulfonic containing mesostructured SBA-15 materials
(ELSEVIER, 2004) Melero, Juan A.; van Grieken, Rafael; Morales, Gabriel; Nuño, Vanesa
Arenesulfonic modified mesostructured SBA-15 is shown as an active catalyst for acylation of aromatic compounds using acetic anhydride as acylating agent. The arenesulfonic acid-centers located within the mesostructured SBA-15 show a greater reaction rate (normalised on the concentration of sulfonic groups) as compared to other sulfonated catalysts and even in solventless conditions. This high activity is accompanied with a remarkable stability without leaching of sulphur species during the reaction. Moreover, an increase of the amount of acid centres does not modify the activity of the material per acid center. Thus, this work introduces a new application of these sulfonated mesostructured materials, not described in literature up to now, and in an important organic reaction.
Fries rearrangement of phenyl acetate over sulfonic modified mesostructured SBA-15 materials
(ELSEVIER, 2005) van Grieken, Rafael; Melero, Juan A.; Morales, Gabriel
Arenesulfonic modified mesostructured SBA-15 is shown as an active catalyst in the liquid-phase Fries rearrangement of phenyl acetate. The arenesulfonic acid-centers located within the structure of SBA-15 show high catalytic performance as compared to other homogeneous and heterogeneous acid catalysts. This high activity is accompanied with a remarkable stability without leaching of sulphur species during the reaction. Reaction conditions have been investigated in order to optimize production of hydroxyacetophenones. Strong adsorption of reaction products and/or coke deposition on the sulfonic acid sites rapidly deactivates the catalyst. Interestingly, when dichloromethane is used as solvent the deactivation process is slowed down drastically. Finally, this contribution supports a new application of these sulfonated mesostructured materials in the production of fine chemicals.
Immobilization strategies for laccase from Trametes versicolor on mesostructured silica materials and the application to the degradation of naphthalene
(ELSEVIER, 2010) Bautista, L. Fernando; Morales, Gabriel; Sanz, Raquel
The oxidation of naphthalene by immobilized laccase from Trametes versicolor has been performed using diverse immobilization strategies on mesostructured silica materials. Laccase was immobilized by physical adsorption on several SBA-15 with different textural properties and by covalent attachment on functionalized SBA-15 prepared by co-condensation method (direct synthesis). The adsorption of laccase was partially reversible and showed some degree of lixiviation. However, covalently attached laccase to aminopropyl and aminobutyl functionalized SBA-15 exhibited important activity for the degradation of naphthalene with, respectively, 35% and 39%wt of removal in 5 hours. The aminopropyl biocatalyst retained higher activity after repeated uses than the corresponding aminobutyl.
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.
Low-grade oils and fats: effect of several impurities on biodiesel production over sulfonic acid heterogeneous catalysts
(ELSEVIER, 2011) Morales, Gabriel; Bautista, L. Fernando; Melero, J.A.; Iglesias, José; Sánchez-Vázquez, Rebeca
Different lipidic wastes and low-grade oils and fats have been characterized and evaluated as feedstocks for the acid-catalyzed production of FAME. The characterization of these materials has revealed significant contents of free fatty acids, Na, K, Ca, Mg, P, unsaponifiable matter and humidity. Arenesulfonic acid-functionalized SBA-15 silica catalyst has provided yields to FAME close to 80% in the simultaneous esterification-transesterification of the different feedstocks, regardless of their nature and properties, using methanol under the following reaction conditions: 160ºC, 2 h, 30 methanol to oil molar ratio, 8 wt% catalyst loading, and 2000 rpm stirring rate. Nevertheless, reutilization of the catalyst is compromised by high levels of impurities, especially because of deactivation by strong interaction of unsaponifiable matter with the catalytic sites. The conditioning of these materials by aqueous washing in the presence of cationic-exchange resin Amberlyst-15, followed by a drying step, resulted in a lower deactivation of the catalyst.
New insights in the deactivation of sulfonic modified SBA-15 catalysts for biodiesel production from low-grade oleaginous feedstock
(Elsevier, 2014) Iglesias, Jose; Melero, Juan A.; Bautista, L. Fernando; Morales, Gabriel; Sánchez-Vázquez, Rebeca; Wilson, Karen; Lee, Adam F.
Arenesulfonic-acid functionalized SBA-15 materials have been used in the production of biodiesel from low grade oleaginous feedstock. These materials display an outstanding catalytic activity, being able to promote the transformation of crude palm oil with methanol into fatty acid methyl esters with high yield (85%) under mild reaction conditions. However, high sensitivity of the catalyst against poisoning by different substances has also been detected. Thus, alkaline metal cations, such as sodium or potassium exert a negative influence on the catalytic activity of these materials, being necessary amounts around 500 ppm of sodium in the reaction media to decrease the catalytic activity of these materials to a half of its initial value in just two reaction runs. The deactivation of arenesulfonic acid functionalized SBA-15 materials seems to occur in this case by ion exchange of the acid protons at the sulfonic groups. Organic unsaponifiable compounds like lecithin or retinol also induce a negative influence in the catalytic activity of these sulfonic acid-based materials, though not so intense as in the case of alkaline metals. The deactivating mechanism associated to the influence of the organic compounds seems to be linked to the adsorption of such substances onto the catalytic acid sites as well as on the silica surface. The accumulation of lecithin in the surface of catalyst, observed by means of thermogravimetric analysis, suggest the creation of a strong interaction, probably by ion pair, between this compound and the sulfonic acid group.
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.
Production of biodiesel from waste cooking oil in a continuous packed bed reactor with an agglomerated Zr-SBA-15/bentonite catalyst
(ELSEVIER, 2013) Melero, Juan A.; Bautista, L. Fernando; Iglesias, Jose; Morales, Gabriel; Sánchez-Vázquez, Rebeca
Zr-SBA-15 material has been agglomerated with bentonite clay to form a macroscopic structured catalyst with particle sizes of 1.5 mm with the purpose of being used in the continuous production of biodiesel from waste cooking oil on a packed bed reactor. The influence of different reaction parameters was assessed including methanol to oil molar ratio, residence time and temperature. The pellet-type Zr-SBA-15/bentonite catalyst was highly active in the continuous flow process leading to a steady molar FAME yield of ca. 96 % at 210 ºC and 70 bar with a methanol to oil molar ratio of 50:1 and a residence time of 30 min. Long-time on stream experiments revealed an outstanding stability of the Zr-SBA-15 particulate material, since this provided a sustained FAME yield of 96% for over 260 hours, being negligible the deactivation of the catalyst during this period. Bentonite clay partially contributed to the methanolysis reaction of triglycerides during the early stages of the reaction, but after a short period (1 hour) its influence on the reaction became very low. In this way, the outstanding catalytic performance of the agglomerated catalyst must be attributed mainly to the presence of active acid sites in the the Zr-SBA-15 material. The leaching of metal species (Na, K, Ca and Mg) coming from bentonite binder was low in the outlet effluent. Catalyst did not suffer any significant changes in physicochemical properties after the long-time on stream experiment, preserving zirconium content and acid capacity.
Production of Sorbitol via Catalytic Transfer Hydrogenation of Glucose
(MDPI, 2020-03-07) García, Beatriz; Moreno, Jovita; Morales, Gabriel; Melero, Juan Antonio; Iglesias, Jose
Sorbitol production from glucose was studied through catalytic transfer hydrogenation (CTH) over Raney nickel catalysts in alcohol media, used as solvents and hydrogen donors. It was found that alcohol sugars, sorbitol and mannitol, can be derived from two hydrogen transfer pathways, one produced involving the sacrificing alcohol as a hydrogen donor, and a second one involving glucose disproportionation. Comparison between short-chain alcohols evidenced that ethanol was able to reduce glucose in the presence of Raney nickel under neutral conditions. Side reactions include fructose and mannose production via glucose isomerization, which occur even in the absence of the catalyst. Blank reaction tests allowed evaluating the extension of the isomerization pathway. The influence of several operation parameters, like the temperature or the catalyst loading, as well as the use of metal promoters (Mo and Fe-Cr) over Raney nickel, was examined. This strategy opens new possibilities for the sustainable production of sugar alcohols.
Ru-ZrO2-SBA-15 as efficient and robust catalyst for the aqueous phase hydrogenation of glucose to sorbitol
(2020-02-05) Melero, Juan Antonio; Moreno, Jovita; Iglesias, Jose; Morales, Gabriel; Fierro, Jose Luis García; Sánchez Vázquez, Rebeca; Cubo, A.; García, Beatriz
The hydrogenation of aqueous solutions of glucose into sorbitol has been tackled in the presence of rutheniumfunctionalized catalysts using mesostructured pure-silica SBA-15 and ZrO2-coated SBA-15 materials as supports. The influence of the metal loading and the presence of ZrO2 in the supports on the catalytic activity of these materials have been evaluated. Metal loading is a major factor affecting the dispersion of the ruthenium active phase, but the presence of a zirconia layer onto the catalyst support revealed to be a key parameter to control not only the dispersion of Ru particles, but also their stability. Catalysts characterization and reaction tests to evaluate the catalytic performance of Ru-containing materials evidenced the beneficial influence of ZrO2-containing supports to prevent the agglomeration of Ru nanoparticles during hydrogenation tests, thus leading to more robust catalysts. This work proposes an approach to the preparation of active and stable catalysts for aqueous phase hydrogenation of biomass-derived carbohydrates.