Examinando por Autor "Melero, J.A."

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Acid-catalyzed etherification of bio-glycerol and isobutylene over sulfonic mesostructured silicas
(ELSEVIER, 2008) Melero, J.A.; Vicente, G.; Morales, G.; Paniagua, M.; Moreno, J. M.; Roldán, R.; Ezquerro, A.; Pérez, C.
Sulfonic-acid functionalized mesostructured silicas have demonstrated an excellent catalytic behavior in the etherification of glycerol with isobutylene to yield tert-butylated derivates. Di-tert-butylglycerols (DTBG) and tri-tert-butylglycerol (TTBG) have shown to be valuable fuel additives leading to decreases in the emission of particulate matter, hydrocarbons, carbon monoxide and unregulated aldehydes. Likewise, said ethers can also act as cold flow improvers for use in biodiesel, reducing also its viscosity. The activities and selectivities achieved over sulfonic acid-functionalized mesostructured silicas are comparable or even superior to those displayed by widely-used macroporous commercial acid resins. Under optimized reaction conditions, these mesostructured catalysts yield a complete glycerol conversion with a combined selectivity towards DTBG and TTBG up to ca. 90%. Furthermore, no formation of undesirable isobutylene oligomers is observed. The acid strength of the sulfonic acid sites has also been found to be an important factor affecting the catalytic performance of these materials.
Activity and resistance of iron-containing amorphous, zeolitic and mesoestructured materials for wet peroxide oxidation of phenol
(ELSEVIER, 2005) Calleja, G.; Melero, J.A.; Martínez, F.; Molina, R.
Iron containing materials have been prepared following several strategies of synthesis and using different silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials was evaluated on heterogeneous Fenton-type processes for the removal of phenol under mild reaction conditions (T=100º, P=0.1 MPa). Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions, by-products distribution (aromatics compounds and carboxylic acids) and degree of metal leached into the aqueous solution. The nature and local environment of iron species is strongly dependent on the synthetic route, which dramatically influences on their catalytic performance. Crystalline iron oxide species supported over mesostructured SBA-15 materials have demonstrated to be the most interesting catalysts for phenol degradation according to its high organic mineralization, low sensitive to be leached out and better oxidant efficiency for Fenton like reactions.
Assessment of Fe2O3/SiO2 catalyst for the continuous treatment of phenol aqueous solutions in a fixed bed reactor
(ELSEVIER, 2010) Botas, Juan Ángel; Melero, J.A.; Martínez, F.; Pariente, M.I.
Different iron-containing catalysts have been tested for the oxidation of phenol aqueous solutions in a catalytic fixed bed reactor in presence of hydrogen peroxide. All the catalysts consist of iron oxide, mainly crystalline hematite particles, over different silica supports(mesostructured SBA-15 silica and non-ordered mesoporous silica). The immobilization of iron species over different silica supports was addressed by direct incorporation of metal during the synthesis or post-synthesis impregnation. The synthesis conditions were tuned up to yield agglomerated catalysts with iron loadings between 10 and 15 wt. %. The influence of the preparation method and the type of silica support was evaluated in a catalytic fixed bed reactor for the continuous oxidation of phenol in terms of its activity (phenol and total organic carbon degradation) as well as its stability (catalyst deactivation by iron leaching). Those catalyst prepared by direct synthesis either in presence (Fe2O3/SBA-15(DS)) or absence(Fe2O3/SiO2(DS)) of template molecules achieved high catalytic performances (TOC reduction of 65 and 52 %, respectively) with remarkable low iron leaching in comparison with the impregnated iron catalysts. Catalytic results demonstrated that the synthesis method plays a crucial role in the dispersion and stability of active species and hence resulting in superior catalytic performances.
Chemically activated hydrochars as catalysts for the treatment of HTC liquor by catalytic wet air oxidation
(Elsevier, 2023) Mora, A. de; Diaz de Tuesta, J.L.; Pariente, M.I.; Segura, Y.; Puyol, D.; Castillo, E.; Lissitsyna, K.; Melero, J.A.; Martínez, F.
Hydrothermal carbonization (HTC) is a highly efficient and valuable technology for treating wet solid wastes and producing solid carbon-based materials named hydrochar. In this work, a hydrochar coming from the HTC of an anaerobic digestion sludge of wastewater treatment plant was used to assess the influence of several activation agents, a base (KOH) and different chloride salts (FeCl3, ZnCl2, and CuCl2) with the exact molar quantities, to develop materials with enhanced surface area and potential inclusion of metal active species for application in wet air oxidation processes. The KOH as an activating agent increased the surface area of hydrochar up to ca. 1000 m2/g of BET surface area. The employment of CuCl2 and FeCl3 as activating agents allows Cu- and Fe-rich doped materials of remarkable surface areas with 49.1 and 42.5 wt% of each metal, respectively. Likewise, the catalytic behavior of the different synthesized carbon-based materials as metal-free and metal-doped catalysts was evaluated for the Catalytic Wet Air Oxidation (CWAO) of a HTC aqueous liquor from a HTC process of animal manure to produce a valuable stream of higher biochemical methane potential in anaerobic digestion. CWAO effluents increased the proportion of carboxylic acids as final by-products due to the oxidation of more complex organic compounds of the initial effluent (ketones, phenols, aromatics and olefins). The CWAO treatments improve the anaerobic digestion rate in biochemical methane potential tests, although the methane production was limited by the lower TOC concentration of the treated streams after CWAO. This research contributes to developing sustainable and efficient strategies for the HTC-liquor treatment, using its solid hydrochar as catalysts, closing the loop of a Circular Economy.
Comprehensive characterization of an oily sludge from a petrol refinery: A step forward for its valorization within the circular economy strategy
(Elsevier, 2021) Jerez, S.; Ventura, M.; Molina, R.; Pariente, M.I.; Martínez, F.; Melero, J.A.
Refinery treatment plants produce large quantities of oily sludge during the petroleum refining processes. The hazardousness associated with the disposal of these wastes, make necessary the development of innovative technologies to handle it adequately, linked to the concepts of circular economy and environmental sustainability. This work provides for the first time a methodology for the deep characterization of this kind of wastes and consequently new insights regarding its valorization. A review of works dealing with the characterization of this type of wastes has been addressed evidencing the complexity and variability of these effluents. The oily sludge under study contains a high concentration of Chemical Oxygen Demand of 196 g COD/L, a Total Kjeldahl Nitrogen of 2.8 g TKN/kg, a phosphorous content as PO43− of 7 g/kg, as well as a great presence of heavy metals in a different range of concentrations. This sludge is composed of three different phases: oily, aqueous and solid. The oily and the solid phases present high percentages of carbon content (84 and 26%, respectively), related to the presence of alkanes ranged from n-C9 to n-C44. Therefore, it could be possible their valorization by the synthesis of catalyst and/or adsorbents. A dark fermentation process could be also proposed for the oily phase to obtain H2 as an alternative energy source. Finally, the aqueous phase contains low carbon and nutrients concentration. A previous thermal pre-treatment applied to the oily sludge might increase nutrient and organic loading in the aqueous phase due to solid destruction, making this aqueous effluent suitable for a further conventional biological treatment.
Coupling membrane separation and photocatalytic oxidation processes for the degradation of pharmaceutical pollutants
(Elsevier, 2013) Martínez, F.; López-Muñoz, M.J.; Aguado, J.; Melero, J.A.; Arsuaga, J.; Sotto, A.; Molina, R.; Segura, Y.; Pariente, M.I.; Revilla, A.; Cerro, L.; Carenas, G.
The coupling of membrane separation and photocatalytic oxidation has been studied for the removal of pharmaceutical pollutants. The retention properties of two different membranes (nanofiltration and reverse osmosis) were assessed. Comparable selectivity on the separation of pharmaceuticals were observed for both membranes, obtaining a permeate stream with concentrations of each pharmaceutical below 0.5 mg/L and a rejected flux highly concentrated (in the range of 16-25 mg/L and 18-32 mg/L of each pharmaceutical for NF-90 and BW-30 membranes, respectively), when an initial stream of six pharmaceuticals was feeding to the membrane system (10 mg/L of each pharmaceutical). The abatement of concentrated pharmaceuticals of the rejected stream was evaluated by means of heterogeneous photocatalytic oxidation using TiO2 and Fe2O3/SBA-15 in presence of hydrogen peroxide as photo-Fenton system. Both photocatalytic treatments showed remarkable removals of pharmaceutical compounds, achieving values between 80 and 100 %. The nicotine was the most refractory pollutant of all the studied pharmaceuticals. Photo-Fenton treatment seems to be more effective than TiO2 photocatalysis, as high mineralization degree and increased nicotine removal were attested. This work can be considered an interesting approach of coupling membrane separation and heterogeneous photocatalytic technologies for the successful abatement of pharmaceutical compounds in effluents of wastewater treatment plants.
Efficient conversion of levulinic acid into alkyl levulinates catalyzed by sulfonic mesostructured silicas
(ELSEVIER, 2013) Melero, J.A.; Morales, G.; Iglesias, J.; Paniagua, M.; Hernández, B.; Penedo, S.
Sulfonic mesoporous silicas have demonstrated an outstanding catalytic performance in the esterification of levulinic acid with different alcohols to produce alkyl levulinates, a family of chemicals considered to be excellent oxygenated fuel extenders for gasoline, diesel and biodiesel. Catalyst screening indicated that propylsulfonic acid-modified SBA-15 material was the most active one, among tested materials, due to a combination of moderately strong sulfonic acid sites with relative high surface hydrophobicity. Under optimized reaction conditions (T = 117 ºC, ethanol/levulinic acid molar ratio = 4.86/1 and catalyst/levulinic acid = 7 wt.% ) almost 100% of levulinic acid conversion was achieved after 2 h of reaction, being negligible the presence of levulinic acid by-products or ethers coming from intermolecular dehydration of alcohols. The catalyst has been reused, without any regeneration treatment, up to three times keeping almost the high initial activity. Interestingly, a close catalytic performance to that achieved using ethanol has been obtained with bulkier alcohols.
Heterogeneous catalytic Wet Peroxide Oxidation Systems for the Treatment of an Industrial Pharmaceutical Wastewater
(ELSEVIER, 2009) Melero, J.A.; Martínez, F.; Botas, Juan Ángel; Molina, R.; Pariente, M.I.
The aim of this work was to assess the treatment of a wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using a Fe2O3/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80ºC using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for a complete carbon depletion and initial pH of ca. 3 allow obtaining TOC degradation around 50% after 200 minutes of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55 hours of reaction. Furthermore, BOD5/COD ratio is increased from 0.20 up to 0.30, whereas the Average Oxidation Stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.
Heterogeneous photo-Fenton degradation of phenolic aqueous solutions
(ELSEVIER, 2005) Martínez, F.; Calleja, G.; Melero, J.A.; Molina, R.
A novel iron-containing mesostructured material has been successfully tested for the heterogeneous photo-Fenton degradation of phenolic aqueous solutions using near UV-visible irradiation (higher than 313 nm) at room temperature and close to neutral pH. This catalyst is a composite material that contains crystalline hematite particles embedded into the mesostructured SBA-15 matrix in a wide distribution of size (30 ¿ 300 nm) and well dispersed ionic iron species within the siliceous framework. The outstanding physicochemical properties make this material a promising photocatalyst leading to better activity than other unsupported iron oxides. An experimental design model has been applied to assign the weight of catalyst and hydrogen peroxide concentrations in the photo-Fenton processes over this particular material. The catalytic performance has been monitored in terms of aromatics and total organic carbon (TOC) conversions, whereas the catalyst stability was evaluated according to the metal leached into the aqueous solution. Hydrogen peroxide concentration plays an important role in the stability of the iron species, preventing their leaching out into the solution, in contrast to the effect shown in typical dark Fenton reaction. The homogeneous leached iron species result in very little contribution to the overall photocatalysis process. Catalyst loadings of 0.5 g/L and concentration of hydrogen peroxide close to the stoichiometric amount have yielded a total abatement of phenol and a remarkable organic mineralization.
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 strategies for the management of a primary refinery oily sludge: A techno-economical assessment of thermal hydrolysis, Fenton, and wet air oxidation treatments
(Elsevier, 2023) Jerez, S.; Ventura, M.; Martínez, F.; Melero, J.A.; Pariente, M.I.
Petroleum refinery wastewater treatment plants produce a significant amount of oily sludge, a hazardous waste that requires proper disposal. It is necessary to develop technologies to treat and valorise it, avoiding the current environmental problems associated with its landfill disposal. This work explores the application of different advanced technologies for the pre-treatment and further valorisation of this oily sludge, which includes thermal hydrolysis, Fenton oxidation, and wet air oxidation. These treatments reduce the solid content by 51–78%. Moreover, the increasing dewaterability and settleability facilitate phase separation, thus enabling further valorisation, obtaining an aqueous effluent more biodegradable (ca. 63%). A conceptual design based on experimental data obtained at bench scale has been developed for the three pre-treatment systems under study. Techno-economic analysis of the three advanced treatments gave unitary costs ranging from 78 €/m3 for thermal hydrolysis to 192 €/m3 for the Fenton treatment, which are all in the low range of the current management cost (70–350 €/m3 ). Thus, the techno-economic analysis developed in this study demonstrates its feasibility compared to the current management of oily sludge from API separators. Thermal hydrolysis can be a low-cost and suitable strategy for producing biodegradable effluent that can be directly treated in the conventional biological treatment plant of the refinery. However, WAO might be a more appropriate option to recover carbon and nutrients for further valorisation in advanced biological processes.
Preparation of titanium molecular species supported on mesostructured silica by different grafting methods
(ELSEVIER, 2002) Calleja, G.; van Grieken, R.; García, R.; Melero, J.A.; Iglesias, J.
Titanium supported on SBA-15 mesoporous silica has been synthesised containing different titanium loadings prepared by chemical grafting using titanocene dichloride as precursor and over different treated silica surfaces. A comparative study using MCM-41 mesoporous silica as support is also reported. The type of silica support and its surface properties as well as the initial concentration of Ti precursor in the organic solution influences clearly the incorporation of Ti species. The materials after grafting treatment were characterized by different conventional techniques including XRD, FT-IR DR UV-Vis and nitrogen adsorption. The titanium containing SBA-15 silica shows hexagonal mesoscopic order and pore sizes up to 70 Å with surface areas up to 600 m2/g and titanium content ranging from 1 to 3 wt. %. DR UV-Vis of Ti containing SBA-15 silica after removal of the organic ligand shows the presence of Ti isolated species tetrahedrally coordinated and the absence of bulky TiO2 phases. Likewise, these materials upon calcination were catalytically active for the epoxidation of styrene with TBHP exhibiting a significant selectivity toward the epoxide.
Selective extraction of high-added value carboxylic acids from aqueous fermentative effluents with new hydrophobic eutectic solvents (HES)
(Elsevier, 2024-10-30) Vidal, N.; Ventura, M.; Martínez, F.; Melero, J.A.
Recovering these carboxylic acids from the fermentative streams in a sustainable, green, and economical way is a significant challenge. This work assessed hydrophobic eutectic solvents (HES) – water-immiscible – for the selective recovery of carboxylic acids via liquid–liquid extraction. Different trioctylphosphine oxide (TOPO) mixtures with menthol and thymol were studied and deeply characterized by 1H and 31P NMR to yield stable eutectic solvents, including a novel experiment of 31P NMR at variable temperatures for the first time. Those stable eutectic solvents were tested in the liquid extraction of complex aqueous mixtures containing C2–C6 carboxylic acids and simple sugars (glucose and xylose). The back-extraction of the carboxylic acids for the recovery of the HES was optimized, being necessary in three stages for the complete cleaning of the eutectic solvent using NaOH 0.1 M. The eutectic mixture of TOPO and thymol in a molar ratio of 1:2 exhibited an overall recovery of C5 and C6 carboxylic acids over 70 %, allowing its selective extraction from the rest of the compounds in the complex mixture. Likewise, this HES (after back extraction) was successfully reused in a second extraction cycle, keeping the performance of the fresh one. Therefore, this study demonstrated that HES can have a high extraction selectivity for carboxylic acids of ≥C5. Moreover, these solvents were stable and allowed reusability, reducing the environmental impact and process costs
Synthesis of titanium containing periodic mesoporous organosilica
(ELSEVIER, 2007) Melero, J.A.; Iglesias, J.; Sáinz-Pardo, J.; Arsuaga, J.M.
Organic-inorganic mesostructured materials were functionalized with titanium by direct synthesis under strong acidic conditions using non-ionic surfactants as structure directing agent and titanocene dichloride as titanium precursor. Materials with different organic content were synthesized with a high mesoscopic order and with incorporation of titanium species in isolated framework positions. The physicochemical properties of the synthesized samples were assessed by different characterization techniques including XRD, 29Si MAS-NMR, nitrogen adsorption/desorption experiments and DR UV-VIS spectroscopy.
Synthesis, characterization and catalytic activity of highly dispersed Mo-SBA-15
(ELSEVIER, 2007) Melero, J.A.; Iglesias, J.; Arsuaga, J.M.; Sainz-Pardo, J.; Frutos, Pilar de; Blázquez, Sandra
Molybdenum-containing SBA-15 materials have been prepared using a co-condensation method with a wide range of metal loadings under acidic conditions and using non-ionic surfactants. These materials display good catalytic activity in the epoxidation of olefins with alkyl hydroperoxides, being the catalytic activity correlated with the nature of supported molybdenum species. The immobilized metal species show different stabilities against leaching depending on their nature. Reutilization catalytic tests indicate that some fraction of the molybdenum show a high stability and it seems to be responsible for the major part of the catalytic activity of these materials. Stable molybdenum species use in a very efficient manner the alkyl hydroperoxide in the epoxidation of olefins whereas leached species leads to non-oxidative consumption of the oxidant and promote secondary reactions.
Tailoring the pore size of hexagonally ordered mesoporous materials containing acid sulfonic groups
(ELSEVIER, 2002) van Grieken, Rafael; Melero, J.A.; Morales, G.
The synergy of catalysis and biotechnology as a tool to modulate the composition of biopolymers (polyhydroxyalkanoates) with lignocellulosic wastes
(Elsevier, 2021) Ventura, M.; Puyol, D.; Melero, J.A.
An integrated method coupling of heterogeneous and biological catalysis has proven effective for producing biopolymers using lignocellulosic urban solid waste as feedstock. Catalysts based on cheap and earth-abundant metals, such as Fe, Mg, Ca, or Zr with basic or acid properties, were used in the pre-treatment step, and phototrophic mixed cultures were chosen for the biological step. By changing catalysts composition, reaction temperature, and catalysts loading, high performance of the catalysts was achieved under the more optimal pre-treatment of lignocellulose waste, with a solid conversion up to 86%, enriching the solid phase in the lignin polymer. The biological conversion of the liquid effluent in a photobioreactor yielded high production of PHA (up to 36 wt% on a dry basis). The characteristics of the polymer were strongly dependent on liquid feed, the composition of which depended on the type of catalysts used in the previous step. A poof of the concept of a new biorefinery design has been presented in this work, showing that it is possible to enhance the advantages of two different disciplines, heterogeneous catalysis, and photoheterotrophic biotechnology.
Treatment of an agrochemical wastewater by integration of heterogeneous catalytic wet hydrogen peroxide oxidation and rotating biological contactors
(Elsevier, 2013-06-15) Melero, J.A.; Pariente, M.I.; Siles, J.A.; Molina, R.; Botas, J.A.; Martinez, F.
The treatment of a non-biodegradable agrochemical wastewater has been studied by coupling of heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and rotating biological contactors (RBCs). The influence of the hydrogen peroxide dosage and the organic content of the wastewater (dilution degree) were studied. The CWHPO of the raw wastewater at 80 ºC and using a moderate amount of oxidant (0.23 gH2O2/gTOC) reduced significantly its total organic carbon content and increased its biodegradability. Likewise, the iron leaching of the heterogeneous catalyst (Fe2O3/SBA- 15) was less than 2 mg/L in the treated effluent. Under the best operating conditions, the resultant CWHPO effluent was successfully co-treated by rotating biological contactors (RBCs) using a simulated municipal wastewater with different percentages of the CWHPO effluent (2.5, 5 and 10 % v/v). The RBCs showed high stability for the treatment of the highest percentage of the CWHPO effluent, achieving total organic carbon (TOC) and total nitrogen (TN) reductions of ca. 78 % and 50 %, respectively. The integration of both processes on a continuous mode has been successfully accomplished for the treatment of the as-received agrochemical wastewater.
Zr-SBA-15 Acid Catalyst: Optimization of the Synthesis and Reaction Conditions for Biodiesel Production from Low-grade Oils and Fats
(Elsevier, 2012-11) Melero, J.A.; Bautista, L.F.; Iglesias, J.; Morales, G.; Sánchez-Vázquez, R.
The production of biodiesel by methanolysis of highly acidic crude palm oil has been optimized for the Zr-SBA-15 heterogeneous acid catalyst. A dual optimization procedure has been carried out using surface response methodology and selecting the yield towards fatty acid methyl esters (FAMEs) as main response factor. Selected target variables for the optimization were: acidity of the synthesis media, zirconium loading, ageing temperature (all three for the synthesis of the catalyst); and temperature, methanol to oil molar ratio, catalyst loading (for the reaction tests). Quadratic equations were obtained for both models and their statistical analysis led to the optimal conditions for Zr-SBA-15 synthesis (0.67 N HCl media concentration, 130ºC ageing temperature, 10 Si/Zr molar ratio), and for the transesterification reaction conditions (209ºC, 12.45 wt% catalyst loading, 45.8 methanol to oil molar ratio). Under these optimized conditions FAME yield reached 92 mol% after 6 h. Additionally, reusability tests revealed that the optimized Zr-SBA-15 catalyst displays an excellent reaction stability, being fully regenerated after calcination at 450ºC. Moreover, the high catalytic activity and stability achieved with crude palm oil is retained when using waste cooking oil (WCO) or low-grade fats such as category-1 fat, waste lard and mixed fats, leading to FAME yields over 90% after 6 hours, for each raw material, and with acidities in the final product lower than 2.5 mg KOH per gram.