Examinando por Autor "Melero, Juan Antonio"

Mostrando 1 - 20 de 21

Application of a Fenton process for the pretreatment of an iron-containing oily sludge: A sustainable management for refinery wastes
(Elsevier, 2021-12-03) Jerez, Sara; Ventura, Maria; Molina, Raul; Martínez, Fernando; Pariente, Maria Isabel; Melero, Juan Antonio
The feasibility of a Fenton-type process for the pretreatment of an oily refinery sludge has been explored taking advantage of the iron contained in the own sludge. This process reduces the content of total petroleum hydro-carbons (TPHs) accompanied by an increase in the total organic carbon concentration in the liquid phase. The effect of the temperature and the hydrogen peroxide loading was thoroughly studied in this work being the oxidant concentration the most critical parameter. Under 60 ◦C and 90 g/L of initial hydrogen peroxide concentration, the Total Organic Carbon (TOC) of the liquid phase was increased up values of 1336 mg/L and with a remarkable contribution of acetic acid as final oxidized compound (396 mgC/L). Additionally, nitrogen and phosphorous compounds were also dissolved in the aqueous phase achieving values of 250 mg/L and 7 mg/L for total Kjeldahl nitrogen and total phosphorous, respectively. Respirometry assays of the aqueous phase after the Fenton pretreatment have evidenced an increase of biodegradability up to 49% which makes this phase suitable for further biological processing in the refinery scheme. The reduction of the content of TPHs (61%) of the oily sludge, has also improved the settleability of the treated effluent (reducing the capillary suction time (CST) in ca. 88%).
Carbonaceous materials from a petrol primary oily sludge: Synthesis and catalytic performance in the wet air oxidation of a spent caustic effluent
(Elsevier, 2024-08) Jerez, Sara; Ventura, María; Martínez, Fernando; Pariente, María Isabel; Melero, Juan Antonio
Oil refineries produce annually large quantities of oily sludge and non-biodegradable wastewater during petroleum refining that require adequate management to minimize its environmental impact. The fraction solid of the oily sludge accounts for 25 wt% and without treatment for their valorization. This work is focused on the valorization of these solid particles through their transformation into porous materials with enhanced properties and with potential application in the catalytic wet air oxidation (CWAO) of a non-biodegradable spent caustic refinery wastewater. Hence, dealing with the valorization and treatment of both refinery wastes in a circular approach aligned with the petrol refinery transformations by 2050. The obtained oily sludge carbonaceous materials showed improved surface area (260–762 m2/g) and a high Fe content. The good catalytic performance of these materials in CWAO processes has been attributed to the simultaneous presence of surface basic sites and iron species. Those materials with higher content of Fe and basic sites yielded the highest degradation of organic compounds present in the spent caustic refinery wastewater. In particular, the best-performing material ACT-NP 1.1 (non-preoxidated and thermically treated with 1:1 mass ratio KOH:solid) showed a chemical oxygen demand (COD) removal of 60 % after 3 h of reaction and with a higher degradation rate than that achieved with thermal oxidation without catalyst (WAO) and that using an iron-free commercial activated carbon. Moreover, the biodegradability of the treated wastewater increased up to 80% (from ca. 31% initially of the untreated effluent). Finally, this material was reused up to three catalytic cycles without losing metal species and keeping the catalytic performance
Contamination of N-poor wastewater with emerging pollutants does not affect the performance of purple phototrophic bacteria and the subsequent resource recovery potential
(2020) Martínez, Fernando; de las Heras, Igor; Molina, Raúl; Segura, Yolanda; Hülsen, Tim; Molina, María Carmen; Gonzalez-Benítez, Natalia; Melero, Juan Antonio; Mohedano, Ángel F.; Puyol, Daniel
Propagation of emerging pollutants (EPs) in wastewater treatment plants has become a warning sign, especially for novel resource-recovery concepts. The fate of EPs on purple phototrophic bacteria (PPB)-based systems has not yet been determined. This work analyzes the performance of a photo-anaerobic membrane bioreactor treating a low-N wastewater contaminated with 25 EPs. The chemical oxygen demand (COD), N and P removal efficiencies were stable (76 ± 8, 62 ± 15 and 36 ± 8 %, respectively) for EPs loading rate ranging from 50 to 200 ng L-1 d-1. The PPB community adapted to changes in both the EPs concentration and the organic loading rate (OLR) and maintained dominance with >85 % of total 16S gene copies. Indeed, an increment of the OLR caused an increase of the biomass growth and activity concomitantly with a higher EPs removal efficiency (30 ± 13 vs 54 ± 11 % removal for OLR of 307 ± 4 and 590 ± 8 mgCOD L-1 d-1, respectively). Biodegradation is the main mechanism of EPs removal due to low EPs accumulation on the biomass, the membrane or the reactor walls. Low EPs adsorption avoided biomass contamination, resulting in no effect on its biological methane potential. These results support the use of PPB technologies for resource recovery with low EPs contamination of the products.
Defective UiO-66(Zr) as an efficient catalyst for the synthesis of bio jet-fuel precursors via aldol condensation of furfural and MIBK
(Elsevier, 2021-07-23) de la Flor, Daniel; López-Aguado, Clara; Paniagua, Marta; Morales, Gabriel; Mariscal, Rafael; Melero, Juan Antonio
The production of jet-fuel precursors from furfural (FUR) via aldol-condensation with methyl-isobutyl ketone (MIBK) over a defective UiO-66(Zr) catalyst is presented. The resultant C11 adduct (FuMe) would allow the selective production of branched alkanes in the range of jet fuel via a subsequent hydrogenation/hydrodeoxygenation process. The catalyst is prepared using formic acid as modulator, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance in this transformation. Thus, the benchmarking with different commercial solid acid catalysts and Zr-based heterogeneous catalysts has identified the defective MOF, UiO-66(Zr)-FA, as clearly superior. An extensive characterization of the modified catalyst by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), acid titration, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform (DRIFT) of adsorbed deuterated acetonitrile, has confirmed the incorporation of missinglinker and missing-node defects within the structure, enabling to explain the enhancement in the catalytic process. The analysis of the reaction kinetics, together with the optimization of the reaction conditions by means of a response surface methodology (allowing predicting the behaviour of the catalytic system under very different conditions) have identified the temperature as the most relevant parameter affecting the selectivity to FuMe. Thus, under the optimized reaction conditions (130 C; 4 h; FUR/Cat = 2; MIBK/FUR = 4), outstanding total FUR conversion and FuMe selectivity (~100%) can be achieved. However, the catalyst gets progressively deactivated in successive catalytic runs under the studied reaction conditions, which is attributed to the formation of organic deposits coming from furfural side reactions.
Degradation of phenolic aqueous solutions by high frequency sono-fenton systems (US-Fe2O3/SBA-15-H2O2)
(Elsevier, 2009) Bremner, David H.; Molina, Raúl; Martínez, Fernando; Melero, Juan Antonio; Segura, Yolanda
The aim of this work is to establish the influence of different ultrasonic frequencies ranging from 20 to 1142 kHz on the efficiency of the US/Fe2O3/SBA-15/H2O2 (sono-Fenton) system. The frequency of 584 kHz has been established as the optimum ultrasonic irradiation for the degradation of aqueous phenol solutions by the sono-Fenton system and the effect of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6 g/L and hydrogen peroxide concentration, close to the stoichiometric amount, show high organic mineralization, accompanied by excellent catalyst stability in a wide range of concentrations of aqueous phenol solutions (0.625 to 10 mM). Additionally, the catalyst can be easily recovered by filtration for reuse in subsequent reactions without appreciable loss of activity. The coupling of US (584 kHz)/Fe-SBA-15/H2O2 at room temperature is revealed as a promising technique for wastewater treatment. Additionally, a new sono-Fenton variant, the so-called latent remediation has also been studied, using ultrasonic irradiation only as pretreatment for 15 minutes in an attempt at reducing the cost of the degradation process. It has been observed that latent remediation provides TOC degradation of around 21 % after 15 min sonication followed by 6 h silent reaction while the typical sono-Fenton reaction affords 29 % TOC reduction after 6h sonication. Keywords: Ultrasound, Sono-Fenton; Phenol; SBA-15.
Effective pharmaceutical wastewater degradation by Fenton oxidation with zero-valent iron
(Elsevier, 2013) Segura, Yolanda; Martínez, Fernando; Melero, Juan Antonio
The pre-treatment of a pharmaceutical wastewater (PWW) by Fenton Oxidation with zero-valent iron (ZVI) and hydrogen peroxide was investigated to improve the degradation of the complex-mixture of organic compounds present in the wastewater. The influence of different crucial parameters such as the initial hydrogen peroxide concentration, the ZVI concentration and the capacity of the ZVI/H2O2 system to treat different organic loading have been evaluated. The optimal conditions for degradation led to TOC reductions of up to 80% in only one hour of treatment. This degree of organic mineralization was reached by using moderate loadings of ZVI and hydrogen peroxide (ZVI/TOC weight and H2O2/TOC molar ratios of 12 and 3.2, respectively). Moreover, the use of waste-metallic iron shavings in terms of TOC removal compared to commercial ZVI powder may be a promising and cheaper development.
Environmental life cycle assessment of polyhydroxyalkanoates production by purple phototrophic bacteria mixed cultures
(Elsevier, 2023) Martin-Gamboa, Mario; Allegue, Luis D.; Puyol, Daniel; Melero, Juan Antonio; Dufour, Javier
Bioplastics offer a promising sustainable alternative to petroleum-based plastics due to their biodegradability as well as favourable thermal and mechanical properties. Among different types of biobased polymers, the production of polyhydroxyalkanoates (PHA) using purple phototrophic bacteria (PPB) and low-value substrates has gained increasing interest. Despite the momentum, challenges regarding the scalability and environmental feasibility of this biopolymer production pathway remain. In response, this study employs an exploratory LCA approach to quantitatively assesses the potential environmental implications of PHA production in powder form and the joint management of the organic fraction of municipal solid waste (OFMSW) through a novel photobiorefinery system that uses PPB mixed cultures. Environmental impacts were tested under multiple improvement scenarios and benchmarked against the production of conventional fossil-based granulate or unprocessed plastics, including low density polyethylene (LDPE), polyethylene terephthalate (PET) and polyurethane (PU). The photobiorefinery stage was found to have the greatest contribution to the impact categories, particularly due to direct emissions, consumption of electricity and production of extractive chemical agents used. These factors accounted for over 70% of the photobiorefinery impact in all cases. Avoided impacts provided net favourable outcomes in terms of carbon footprint and fossil resources when comparing PHA production to conventional plastics, especially PET and PU, with impact reductions ranging from 30% to 60%, respectively. However, when considering other impact categories like eutrophication, this situation was less favourable. The exploration of alternative scenarios offered significant impact reductions, especially when renewable electricity or an environmentally friendly extraction agent is used. Moreover, minimizing methane losses or co-producing hydrogen in the photobiorefinery had a notably positive effect on the carbon footprint, reducing the impact by more than 2 t of CO2 eq per t of PHA powder compared to the base case. Therefore, the implementation of feasible improvement measures in the short term can position PHA produced by mixed cultures as a sustainable alternative to petroleum-based plastics.
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.
Exploring the effects of ZVI addition on resource recovery in the anaerobic digestion process
(2018) Puyol, Daniel; Flores Alsina, Xavier; Segura, Yolanda; Molina, Raúl; Padrino, Beatriz; Fierro, Jose Luis G.; Gernaey, Krist V.; Melero, Juan Antonio; Martínez, Fernando
The influence of Zero Valent Iron (ZVI) addition on the potential resource recovery during the anaerobic digestion (AD) of domestic waste sludge is assessed. Potentially recoverable resources analyzed were nutrients such as struvite to recover P, and energy as biogas to recover C. Short term (biochemical methane potential tests, BMP) and long term (AD1, AD2) experiments are conducted using two types of set-up (batch, continuous). Process data (influent, effluent and biogas) is continuously collected and the dry digested sludge is analyzed by XPS. A mathematical model is developed based on a modified version of the Anaerobic Digestion Model No 1 upgraded with an improved physicochemical description, ZVI corrosion, propionate uptake enhancement and multiple mineral precipitation. The results of all experiments show that ZVI addition increases methane production and promotes the formation of siderite (FeCO3) and vivianite (Fe3(PO4)2), which causes changes in the biogas composition (%CH4 versus %CO2) and reduces P release. The model can satisfactorily reproduce the dynamics of AD processes, nutrient release, pH and methanogenesis in AD1. The proposed approach also describes the changes in the overall performance of the process because of ZVI addition in AD2. A model-based scenario analysis is included balancing chemical-ZVI addition and increased methane production/struvite precipitation. This scenario analysis allows concluding that: (a) the improvement of methane production does not compensate the costs of ZVI purchase, and (b) ZVI dramatically decreases the P recovery potential in the digestate of the AD systems. This is the first study to experimentally and mathematically describe the effect of ZVI on biogas production/composition and on the fate of phosphorus compounds, and its potential implications for potential energy and phosphorus recovery in AD systems.
Fe-N doped carbon materials from oily sludge as electrocatalysts for alkaline oxygen reduction reaction
(Elsevier, 2024-03-01) Jerez, Sara; Pedersen, Angus; Ventura, Maria; Mazzoli, Lorenzo; Pariente, Maria Isabel; Titirici, Magdalena; Melero, Juan Antonio; Barrio, Jesús
Alkaline oxygen reduction reaction (ORR) presents an important role for energy conversion technologies and requires the development of an efficient electrocatalyst. Pt-based catalysts provide suitable activity; however, Pt production accessibility and high costs create hurdles to their commercial implementation. Fe coordinated within N-doped carbon materials (Fe–N–C) are a promising alternative due to their high ORR catalytic activity, although the currently commercially available Fe–N–C materials rely on harsh synthetic protocols which can lead to increased environmental impacts. In this work we target this issue by taking advantage of an oily sludge waste currently generated in refineries to synthesize Fe–N–C materials, thus, avoiding the environmental impact caused by the management of this waste. The solid particles within oily sludge, which present a high concentration of C and Fe, were combined by different nitrogen sources and pyrolyzed at high temperatures. The prepared materials present a hierarchical pore structure with surface areas up to 547 m2 g−1. X-ray photoelectron spectroscopy analysis found that the impregnation of N using phenanthroline promotes the formation of pyridinic-N structures, which enhances the ORR performance compared to melamine doping. Additional doping of Fe with phenanthroline results in an ORR mass activity of 1.23 ± 0.04 A gFeNC at 0.9 VRHE, iR-free in a rotating disc electrode (0.1 M KOH). This catalyst also shows a lower relative loss in activity at 0.9 VRHE after 8000 cycles in O2-saturated conditions compared to a commercial FeNC catalyst, PMF D14401, (−63.5 vs −69 %, respectively), demonstrating promise as a cheap and simple route to Fe–N–C catalysts for alkaline ORR.
Heterogeneous Photo-Fenton Oxidation of Benzoic Acid in Water Effect of Operating Conditions, Reaction By-Products and Coupling with Biological Treatment
(ELSEVIER, 2008) Pariente, M. Isabel; Martínez, Fernando; Melero, Juan Antonio; Botas, Juan Ángel; Velegraki, Theodora; Xekoukoulotakis, Nikolaos P.; Mantzavinos, Dionissios
The heterogeneous photo-Fenton oxidation of benzoic acid, a precursor of several organic pollutants found in agro-industrial effluents, was studied in model aqueous solutions. UVA irradiation was provided by a 125 W medium pressure mercury lamp, while a nanocomposite material of crystalline iron oxides supported over mesostructured SBA-15 was used as the catalyst. Experiments were conducted at benzoic acid initial concentrations between 25 and 450 mg/L, catalyst concentrations between 0.3 and 1.2 g/L and hydrogen peroxide concentrations between 20% and 100% of the stoichiometric amount needed for complete mineralization. Conversion, which was found to be first order regarding benzoic acid concentration, generally increased with increasing the concentration of Fenton¿s reagents and decreasing substrate concentration. HPLC analysis showed that oxidation was accompanied by the formation of several by-products; of these, the three monohydroxybenzoic acids as well as oxalic acid were successfully identified and quantified. By-products were more resistant to oxidation than benzoic acid since COD reduction was generally lower than substrate conversion. Catalyst stability was assessed measuring the extent of iron leaching in the reaction mixture and was found to be excellent as dissolved iron never exceeded 5% relative to the initial iron content. The aerobic biodegradability of benzoic acid before and after photo-Fenton oxidation was assessed by shake flask tests. Chemical oxidation enhanced the biodegradability of benzoic acid although the oxidized solution was more ecotoxic to marine bacteria than the original one. The feasibility of coupling chemical and biological oxidation was also assessed for an actual olive oil mill effluent.
Increasing biodegradability of a real amine-contaminated spent caustic problematic stream through WAO and CWAO oxidation using a high specific surface catalyst from petcoke
(Elsevier, 2023) González, Carlos; Pariente, María Isabel; Molina, Raúl; Espina, L.G.; Masa, María; Bernal, Vicente; Melero, Juan Antonio; Martinez, Fernando
Different operating conditions of wet air oxidation and catalytic wet air oxidation have been studied for the treatment of highly concentrated methyldiethanolamine wastewater streams from amine units of acid gas recovery in petrol refineries. These units occasionally generate streams of high methyldiethanolamine content that require special actions to avoid undesirable impacts on the downstream biological process of the petrochemical wastewater treatment plant due to its inhibition effect. The wet air oxidation treatment achieved remarkable removals of methyldiethanolamine, sulfides, chemical oxygen demand and total organic carbon (99%, 95%, 65% and 38%, respectively). Likewise, activated petroleum coke materials from the own refinery plant were tested as catalysts in the process. These materials were prepared under different conditions (chemical activating agent and thermal carbonization process). The catalytic wet air oxidation treatment using an activated petroleum coke was able to remove the methyldiethanolamine at milder operation conditions keeping a similar performance in terms of wastewater treatment removals as compared to the non-catalytic experiments. This technology significantly increased the biodegradability of the treated effluents ranging from 25 to 70 % due to the formation of more biodegradable substrates (acetic acid and ammonium) for further biological treatment.
Liquid phase rearrangement of long straight-chain epoxides over amorphous, mesostructured and zeolitic catalysts
(ELSEVIER, 2004) Serrano, David P.; van Grieken, Rafael; Melero, Juan Antonio; García, Alicia
A variety of materials with different structural features and acid properties, including amorphous, mesostructured and zeolitic catalysts have been tested in the liquid-phase rearrangement of 1,2-epoxyoctane. The structure and acid strength of the catalysts influence strongly on the activity and product selectivity. The main rearrangement products are the aldehyde, allylic alcohols and diol. Acid sites in the amorphous materials show a poor catalytic activity. Al-TS-1 and Al-Ti-beta, zeolites with medium aluminium content, lead to significant activities and selectivities towards both the aldehyde and the octenols in comparison to those obtained with other zeolitic materials tested. Aluminium-containing mesostructured materials present much higher activities than amorphous and zeolitic catalysts. Al-MCM-41 synthesized by a sol-gel method at room temperature yielded selectivities to octaldehyde and octen-1ols of 40.6% and 44.7%, respectively with a high catalyst activity (TOF of ca. 30.5).
Mineralization of phenol by a heterogeneous ultrasound\Fe-SBA-15\H2O2 process: multivariate study by factorial design of experiments
(Elsevier, 2006) Molina, Raúl; Martínez, Fernando; Melero, Juan Antonio; Bremner, David H.; Chakinala, Anand G.
A novel heterogeneous catalyst has been used for the oxidation of aqueous solutions of phenol by catalytic wet peroxide oxidation assisted by ultrasound irradiation. This composite catalyst material that contains crystalline hematite particles embedded into a mesostructured SBA-15 matrix was used successfully in the oxidation of phenol by heterogeneous Fenton and photo-Fenton processes. Ultrasound is found to enhance the activity of the catalyst in the process, without prejudice to the stability of the iron supported species. The influence of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6 g/L and a concentration of hydrogen peroxide close to twice the stoichiometric amount yield a remarkable organic mineralization, accompanied by excellent catalyst stability. The coupled US/Fe-SBA-15/H2O2 process at room temperature is revealed as a promising technique for wastewater treatment.
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.
Thermal hydrolysis of solid fraction reduces waste disposal and provides a substrate for anaerobic photobiological treatment of refinery wastewater
(Royal Society of Chemistry, 2023-02-15) Jerez, Sara; San Martín, Javier; Ventura, Maria; Pariente, Maria Isabel; Segura, Yolanda; Puyol, Daniel; Molina, Raúl; Melero, Juan Antonio; Martinez, Fernando
Oil refineries generate vast amounts of refinery wastewater (RWW) and oily sludge (OS). Conventional treatments typically manage these effluents separately, and resource recovery potential is not considered. The thermal hydrolysis (TH) of oily sludge at different temperatures from 175 to 200 °C and several hydrolysis times from 30 to 90 minutes has been assessed. The TH reduced the solid fraction of the oily sludge by up to 50% and released substrates in the liquid stream with up to 14 g L−1 of soluble chemical oxygen demand (SCOD) and 592 mg L−1 of NH4+-N. Additionally, the hydrolyzed fraction was assessed as a substrate for the biological treatment of the refinery wastewater. An anaerobic photobiological system based on purple phototrophic bacteria (PPB) was considered to evaluate the co-treatment of both effluents. Batch experiments showed a 10- to 30-fold enhancement of the biomass yield, using both the RWW and the hydrolyzed fraction of the oily sludge. The less energetic TH conditions in terms of temperature and operation time produced the most biodegradable hydrolyzed stream with biomass yields close to those obtained for the control under optimal growth conditions. These results demonstrate the feasibility of the proposed integrated strategy to reduce the solid fraction of the oily sludge by the TH process and to release soluble substrates for a novel anaerobic photobiological treatment along with the RWW.
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.
Understanding the role of Al/Zr ratio in Zr-Al-Beta zeolite: Towards the one-pot production of GVL from glucose
(Elsevier, 2021-04-07) Paniagua, Marta; Morales, Gabriel; Melero, Juan Antonio; Iglesias, Jose; López-Aguado, Clara; Vidal, Nora; Mariscal, Rafael; López-Granados, Manuel; Martínez-Salazar, Irene
The direct one-pot transformation of glucose into γ-valerolactone (GVL) can be accomplished by means of a cascade of reactions in which Brønsted acid-catalyzed transformations are combined with catalytic transfer hydrogenation (CTH) by using 2-propanol as sacrificial alcohol, avoiding the use of high-pressure hydrogen. Catalysts containing Zr Lewis acid sites have been successfully applied in CTH reactions while the acid-driven transformations can be preferentially promoted by Brønsted Al-related acidity. Here, we present the combination of Zr and Al as active sites within a BEA zeolite structure as catalyst, with the possibility of adjusting the Al/ Zr ratio from ∞ (commercial H-Beta) to 0 (aluminium-free Zr-Beta), which show a scale of Brønsted/Lewis acid sites ratios. The Al/Zr ratio has a strong impact on the products distribution. As the Zr content increases, higher amount of GVL is obtained, leading to a maximum over the catalyst with high amount of Zr and low content of Al acid sites (Al/Zr = 0.2). An increase of reaction temperature, as well as reaction time, allows an enhancement of yields towards the desired products, leading to a maximum yield towards GVL of 24 mol% over Zr-Al-Beta (2.0), and a maximum yield towards isopropyl lactate of 26 mol% over Zr-Beta at 190 ◦C.
Unraveling PHA production from urban organic waste with purple phototrophic bacteria via organic overload
(Elsevier, 2022-09-01) Diaz Allegue, Luis; Ventura, Maria; Melero, Juan Antonio; Puyol, Daniel
The production of polyhydroxyalkanoates (PHA) with purple phototrophic bacteria (PPB) has been limited due to low yields and limited knowledge regarding the diverse routes used for carbon biosynthesis. The present study increases PHA accumulation yields using urban organic waste pretreated by steam explosion and acidogenic fermentation as substrate. Throughout the PPB-based photoheterotrophic process in an anaerobic membrane photobioreactor, the organic loading rate (OLR) was modified to increase the amount of PHA and biomass in the reactor. A maximum PHA accumulation of 42% (g(PHA gBiomass)(-1)) on a dry basis was achieved and maintained for 10 d for an OLR of 1 gCOD L-1 d(-1), and hydraulic and sludge retention times of 2 and 6 d, respectively. This PHA accumulation capacity is the maximum obtained using a mixed culture of PPB fed with waste. Also, a medium-chain PHA (polyhydroxyhexanoate) has been quantified, enhancing the physicochemical properties and diversifying their industrial applications. Furthermore, we show novel alternatives to PHA accumulation: carbon storage as glycogen and extracellular polymers while deriving the excess electrons into hydrogen. Finally, a statistical study of microbial communities has settled the environmental variables with the most significant influence on these communities' variability. This work demonstrates the importance of acquiring a thorough understanding of carbon accumulation and electron allocation strategies of PPB under stressful conditions and shows promising results for a larger scale implementation of a PPB-based photobiorefinery, which could valorize urban organic waste to produce different high added-value products within the context of the circular bioeconomy.