Examinando por Autor "Bautista, L. Fernando"

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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.
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.
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.
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.
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.
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.