Examinando por Autor "Iglesias, Jose"

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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.
Agglomeration of Ti-SBA-15 with clays for liquid phase olefin epoxidation in a continuous fixed bed reactor.
(ELSEVIER, 2008) Melero, Juan A.; Iglesias, Jose; Sainz-Pardo, Javier; Frutos, Pilar de; Blázquez, Sandra
Titanium-containing SBA-15 material has been agglomerated with bentonite clay to form macroscopic structured catalyst particles with the purpose of being used in continuous epoxidation processes on a fixed bed reactor. The binding conditions, the mass ratio catalyst to binding agent as well as the calcination temperature of the material were studied to improve as much as possible the catalytic behavior and mechanical strength of the titanium-based catalyst. The binded material has been finally tested in the liquid epoxidation of 1-octene with ethyl benzyl hydroperoxide in a continuous up-flow fixed bed reactor. Reaction results reveal a better catalytic performance of this catalyst, both regarding to the conversion of the olefin and efficient use of the oxidant, than conventional commercially available TiO2-SiO2, specially when pellet surface hydrophobization is performed by silylation treatment.
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.
Catalytic Transfer Hydrogenation of Glucose to Sorbitol with Raney Ni Catalysts Using Biomass-Derived Diols as Hydrogen Donors
(ACS, 2021) García, Beatriz; Orozco-Saumell, Ana; López Granados, Manuel; Moreno, Jovita; Iglesias, Jose
The catalytic transfer hydrogenation (CTH) of glucose to sorbitol has been studied using a wide collection of different biomass-derived alcohols and diols as hydrogen donors. Catalytic activity results reflect the feasibility to conduct this transformation in the presence of conventional, commercially available Raney Ni-type sponges as catalysts. Sacrificial diols displayed a superior performance as hydrogen donors as compared to short-chain alcohols, including secondary alcohols. Among them, terminal diols such as 1,4-butanediol and 1,5-pentanediol were revealed as excellent hydrogen donors, providing a high selectivity in the conversion of glucose into sorbitol. As for the catalysts, molybdenum promotion provided a very high catalytic activity to sponge nickel catalysts, even under mild temperature conditions. The transformation was also studied in a fixed-bed reactor under continuous-flow operation conditions. Results demonstrate that the catalysts are highly stable and able to operate for at least 550 h on stream with a high selectivity in the CTH of glucose to sorbitol.
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.
Direct synthesis of organically modified Ti-SBA-15 materials
(ELSEVIER, 2008) Iglesias, Jose; Melero, Juan A.; Sainz-Pardo, Javier
Organically-modified Ti-SBA-15 materials have been prepared through a direct synthesis procedure based on the co-condensation of tetraethyl orthosilicate (TEOS), alkyltriethoxysilanes (R-TES) and titanocene dichloride as silicon, organic species and titanium sources respectively. The prehydrolysis time for the TEOS and the amount and type of alkyl functionality were studied in order to achieve mesostructured organic-modified Ti-SBA-15 materials. The synthesized samples were assayed in the catalytic epoxidation of 1-octene with TBHP as oxidant. The catalytic results reveal a direct correlation between the activity of the catalyst per titanium site and the length of the alkyl chain. Higher lengths of the alkyl chain induce a significant increase of the activity of the titanium sites due to the enhancement of their hydrophobic microenvironment. Likewise, improved efficiency in the use of the oxidant has also been observed when using organic modified Ti-SBA-15 materials, being correlated this effect with the reduction of the non-oxidative decomposition of TBHP. Finally, the reutilisation tests indicate very high stability of the prepared catalysts in epoxidation reactions with TBHP.
Efficient Conversion of Glucose to Methyl Lactate with Sn-USY: Retro-aldol Activity Promotion by Controlled Ion Exchange
(ACS, 2022) Jimenez-Martin, Jose M.; Orozco-Saumell, Ana; Hernando, Héctor; Linares, María; Mariscal, Rafael; López Granados, Manuel; García, Alicia; Iglesias, Jose
Sn-USY materials have been prepared through an optimized post-synthetic catalytic metalation procedure. These zeolites displayed, upon ion exchange with alkaline metals, an outstanding activity in the direct transformation of glucose into methyl lactate, yielding more than 70% of the starting glucose as the target product, and an overall combined retro-aldol condensation product yield above 95% in a short reaction time (<4 h). This outstanding catalytic performance is ascribed to the neutralization of Brønsted acid sites, the consequent depression of side reactions, and a higher population of tin open sites in the ion-exchanged Sn-USY zeolites. Reusability tests evidenced some loss of catalytic activity, partially caused by the closing of tin sites, although the use of small amounts of water in the reaction media demonstrated that this deactivation mechanism can be, at least, partially alleviated.
Highly Ti-loaded MCM-41: Effect of the metal precursor and loading on the titanium distribution and on the catalytic activity in different oxidation processes
(ELSEVIER, 2010) Iglesias, Jose; Melero, Juan A.; Sanchez-Sanchez, Manuel
Ti-MCM-41 materials have been prepared by co-condensation of tetraethylorthosilicate with two different titanium sources: titanocene dichloride and titanium isopropoxide. The hydrophobic nature of cyclopentadienyl rings has been used to enhance the interaction between the titanocene dichloride starting compound and the surfactant micelles leading to, after calcination, titanium centers finally located in the surface of the mesopores. In this way, increasing the content of titanocene dichloride in the synthesis gel causes the formation of titanium dioxide nanofibers inside the mesoporous system ¿ clearly visible by TEM analysis ¿ for high metal loadings. Such Ti distribution, which has not been observed when using titanium isopropoxide, confers to these Ti-MCM-41 materials a different catalytic behavior to that of conventional Ti-MCM-41 materials for a given Ti content. Thus, samples prepared with titanocene dichloride display higher catalytic activity in the epoxidation of 1-octene and in the oxidative bromination of phenol red than samples prepared with titanium isopropoxide. Besides, in both reactions, the maximum of catalytic activity is reached for lower titanium loading when titanocene dichloride is the starting Ti source as a consequence of a better accessibility of reactants to the final Ti centres.
Life cycle assessment applied to bio-based platform molecules: Critical review of methodological practices
(Elsevier, 2023) Blanco-Cejas, Jorge; Martín, Sandra; Linares, María; Iglesias, Jose; Moreno, Jovita
Bio-based platform molecules are chemicals identified as key agents in the development of circular bioeconomy. Their penetration into the current market would sustain the shift of a chemical industry mainly based on the use of petrochemical feedstock to the use of resources of biological origin. Bio-based platform chemicals have received much attention during the last decades, and thus, there is plenty of literature focused on their production throughout a plethora of different technologies. Nevertheless, most of these procedures lack of maturity and are subject to constraints. Thus, the way to ensure improved environmental sustainability is through the application of tools such as life cycle assessment (LCA). Although the integration of LCA is increasingly common during the design phase of these processes, the diverse modeling options can lead to very unlike results. Converging practices around consensus methodologies would lead to more reliable and comparable results. The purpose of this review is to identify the critical points of divergence that hinder this comparison and try to reconcile them towards the best options within biomass-derived platform chemicals specific context. The performed meta-analysis revealed the existence of three key aspects to be considered in the comparison of LCA studies: cradle-to-gate scope (mostly intermediate chemicals), prospective analysis (technologies under development), and multifunctional processes (biorefineries with several valuable outputs). Regarding the scope, reconciling the temporal scope of the studies with the correct allocation of biogenic carbon fluxes is the aspect that requires a deeper discussion. Evaluating novel technologies (characterized by industrial data scarcity) require careful scaling of the systems, as well as rigorous calculations of the uncertainty of results. Concerning multifunctionality, modelling many flows and their interactions is the most challenging task. Within this context, the consequential perspective seems a more correct approach to capture all the elements of these novel and complex systems, although the lack of data can make it unfeasible in numerous cases. Finally, a limited comparison is performed based on the key aspects previously identified. Thus, broader conclusions are inferred for the most promising routes to produce three bio-based platforms among the selected as a case study: lactic acid (chemo-catalytic transformation of swine manure), succinic acid (fermentative pathways using lignocellulosic biomass), and ethylene (wood gasification).
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.
Novel Titanocene-Tartrate complexes as catalysts for the asymmetric epoxidation of allylic alcohols
(ELSEVIER, 2007) van Grieken, Rafael; Garcia, Rafael A.; Calleja, Guillermo; Iglesias, Jose
This communication presents the synthesis of novel titanocene-based chiral complexes and their application as catalysts for asymmetric oxidation reactions. These new complexes drive the catalytic asymmetric oxidation of allylic alcohols without the requirement of low temperature conditions, a usual drawback in asymmetric synthesis. Results from catalytic studies shows the enantioselectivity of these chiral complexes strongly depends on the steric hindrances caused by the chiral ligand and the alkyl hydroperoxide oxidant around the titanium centre.
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.
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.
Transformation of Glucose into Sorbitol on Raney Nickel Catalysts in the Absence of Molecular Hydrogen: Sugar Disproportionation vs Catalytic Hydrogen Transfer
(2019-03-01) García, Beatriz; Moreno, Jovita; Iglesias, Jose; Melero, Juan Antonio; Morales, Gabriel
Raney nickel catalysts have been tested in the transformation of glucose into sorbitol through a hydrogen transfer pathway in the presence of short chain alcohols. Comparison between different sacrificing alcohols evidenced that catalytic hydrogen transfer (CHT) was only possible from ethanol under the tested neutral conditions. Catalytic tests showed that together with CHT route, sorbitol was also produced by means of sugar disproportionation, with the simultaneous production of gluconolactone, which takes place easily in the presence of the Raney Ni catalysts. Studies on the influence of the catalyst loading on the production of sorbitol revealed the existence of a catalyst activation step, attributed to the generation of metal-hydride species, the truly catalytic sites for hydrogenation. However, a catalyst deactivation phenomenon was detected as well. In this case, TGA and FTIR analysis allowed ascribing the adsorption of organic species, coming from the oxidation of glucose (such as gluconic acid), onto the catalyst surface, to the most plausible cause for the deactivation of the catalyst. Catalyst recycling tests evidenced the deactivation occurred mainly during the first use of the Raney Ni catalyst.
Valorization of hemicellulosic sugars to sugar alcohols by Raney nickel mediated hydrogen transfer
(Elsevier, 2024-01-19) García, Beatriz; Montaña, Maia; Gonzalez, Miguel Ángel; Morales, Jovita; Iglesias, Jose
The versatility of the pathway to produce polyols from sugars through catalytic transfer hydrogenation (CTH) using commercial Raney nickel catalysts and 1,4-butanediol as hydrogen source has been explored. The results reveal that the nickel purity of the catalyst is a key parameter in process selectivity and presents the CTH route as a promising alternative to conventional hydrogenation processes, effective for the complete valorization of the sugar platform, including hexoses, pentoses and disaccharides. The study uncovers a significant influence of sugar structure on the resulting reactions, with threo-configured sugars displaying enhanced selectivity, while erythro-configured sugars demonstrate elevated conversion rates and the production of a broader spectrum of sugar alcohol isomers. Furthermore, a computational study, using density functional theory (DFT) calculations, has been carried out to describe the performance of the disaccharides and correlate it with their activity in the reaction media.