Examinando por Autor "Ventura, Maria"

Mostrando 1 - 12 de 12

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%).
Cyclopentadienyl–Silsesquioxane Titanium Catalysts: Factors Affecting Their Formation and Activity in Olefin Epoxidation with Aqueous Hydrogen Peroxide
(Wiley, 2016-04-20) Ventura, Maria; Tabernero, Vanessa; Cuenca, Tomas; Royo, Beatriz; Jimenez, Gerardo
The reaction of titanium chlorosilyl-substituted cyclopentadienyl (Cp) complexes, Ti(eta(5)-C5H3R'SiMe2Cl)Cl-3 (R' = H, 1b; SiMe3, 1c), with 1 equiv. of various silsesquioxane trisilanols, R7Si7O9(OH)(3) (R = iBu, 2a; Ph, 2b), affords either corner-capped Cp derivatives, Ti(eta(5)-C5H3R'SiMe2Cl)(R7Si7O12-kappa O-3(3)) (R' = H, R = iBu, 5a, Ph, 5b; R' = SiMe3, R = iBu, 7a, Ph, 7b), or cyclopentadienyl-silsesquioxane complexes, Ti(eta(5)-C5H4SiMe2OR7Si7O11 kappa O-2(2)) Cl (R' = H, R = iBu, 6a, Ph, 6b; R' = SiMe3, R = iBu, 8a, Ph, 8b), depending on the reaction conditions. In any case, upon heating, kinetic products 5 and 7 are transformed into the corresponding thermodynamic products 6 and 8, respectively. The electron-donating ability of the Cp ring is a relevant controlling parameter: a strong p-donor character facilitates the isomerization process. In addition, the nature of the silicon substituents in the silsesquioxane framework, the type of solvent, and the reaction temperature are also factors that significantly affect this process. Cyclopentadienyl-silsesquioxane complexes 6b and 8b are efficient and selective catalysts for epoxidation with aqueous hydrogen peroxide under mild conditions. Such a catalytic efficiency is attributed to the hydrophobic environment generated about the titanium atom by the Cp ring incorporated into the cyclopentadienyl-silsesquioxane ligand
Cyclopentadienyl-silsesquioxane titanium complexes: Highly active catalysts for epoxidation of alkenes with aqueous hydrogen peroxide
(American Chemical Society, 2012-05-17) Ventura, Maria; Gonzalez Mosquera, Marta Elena; Cuenca, Tomas; Royo, Beatriz; Jimenez, Gerardo
Titanium complexes bearing an unprecedented tridentate cyclopentadienyl−silsesquioxanate ligand provide a new class of efficient and selective catalysts for epoxidation of olefins with aqueous hydrogen peroxide under homogeneous conditions.
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.
Selective Aerobic Oxidation of 5-(Hydroxymethyl)furfural to 5-Formyl-2-furancarboxylic Acid in Water
(Wiley-VCH Verlag, 2016) Ventura, Maria; Aresta, Michele; Dibenedetto, Angela
A simple, cheap, and selective catalyst based on copper/cerium oxides is described for the oxidation of 5-(hydroxymethyl)furfural (5-HMF) in water. An almost quantitative conversion (99 %) with excellent (90 %) selectivity towards the formation of 5-formyl-2-furancarboxylic acid, a platform molecule for other high value chemicals, is observed. The catalyst does not require any pretreatment or additives, such as bases, to obtain high yield and selectivity in water as solvent and using oxygen as oxidant. When a physical mixture of the oxides is used, low conversion and selectivity are observed. Air can be used instead of oxygen, but a lower conversion rate is observed if the same overall pressure is used, and the selectivity remains high. The catalyst can be recovered almost quantitatively and reused. Deactivation of the catalyst, observed in repeated runs, is due to the deposition of humins on its surface. Upon calcination the catalyst almost completely recovers its activity and selectivity, proving that the catalyst is robust
Selective Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran or 2-Formyl-5-furancarboxylic Acid in Water by using MgOCeO2 Mixed Oxides as Catalysts
(Wiley-VCH Verlag, 2018) Ventura, Maria; Lobefaro, Francesco; de Giglio, Elvira; Distaso, Monica; Nocito, Francesco; Dibenedetto, Angela
Mixed oxides based on MgO⋅CeO2 were used as efficient catalysts in the aerobic oxidation of 5-hydroxymethylfurfural (5-HMF) to afford, with very high selectivity, either 2,5-diformylfuran (DFF, 99 %) or 2-formyl-5-furancarboxylic acid (FFCA, 90 %), depending on the reaction conditions. 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA, 57–90 %) was formed only at low concentration of 5-HMF (<0.03 m) or in presence of external bases. The conversion of 5-HMF ranged from a few percent to 99 %, according to the reaction conditions. The oxidation was performed in water, with O2 as oxidant, without any additives. The surface characterization of the catalysts gave important information about their acid–base properties, which drive the selectivity of the reaction towards DFF. FFCA was formed from DFF at longer reaction times. Catalysts were studied by XPS and XRD before and after catalytic runs to identify the reason why they undergo reversible deactivation. XRD showed that MgO is hydrated to Mg(OH)2, which, even if not leached out, changes the basic properties of the catalyst that becomes less active after some time. Calcination of the recovered catalyst allows recovery of its initial activity. The catalyst is thus recoverable (>99 %) and reusable. The use of mixed oxides allows tuning of the basicity of the catalysts, avoiding the need for external bases for efficient and selective conversion of 5-HMF and waste formation, resulting in an environmentally friendly, sustainable process.
Selective Oxidation of 5-(Hydroxymethyl)furfural to DFF Using Water as Solvent and Oxygen as Oxidant with Earth-Crust-Abundant Mixed Oxides
(American Chemical Society, 2018-12-28) Nocito, Francesco; Ventura, Maria; Dibenedetto, Angela; Aresta, Michele
5-Hydroxymethylfurfural (5-HMF) can be considered a prominent building block: because of the presence of the alcohol and aldehyde moieties, it can be used to generate useful molecules as chemicals of industrial interest with high added value, monomers for polymers, and even fuels. This article shows how building up mixed oxides of different complexities and properties may drive the selectivity toward one of the possible products generated from 5-HMF. In particular, mixed oxides based on cerium and other metals abundant on the earth-crust perform the selective oxidation of 5-HMF to 2,5-diformylfuran (94%), using oxygen as oxidant and water as solvent. The roles of the reaction conditions (temperature, reaction time, oxygen pressure, concentration of the substrate), the chemical composition, the acidic/basic properties, and redox properties of the catalysts are discussed.
Selective sulfoxidation with hydrogen peroxide catalysed by a titanium catalyst
(Royal Society of Chemistry, 2014-08-21) Postigo, Lorena; Ventura, Maria; Cuenca, Tomás; Jimenez, Gerardo; Royo, Beatriz
A moisture-tolerant cyclopentadienyl-silsesquioxane titanium complex efficiently catalyses the selective oxidation of various types of sulfides to either sulfoxides (TOFs up to 32 530 h(-1)) or sulfones with H2O2 (30% in water) under mild conditions.
Sustainable Synthesis of Oxalic and Succinic Acid through Aerobic Oxidation of C6 Polyols Under Mild Conditions
(Wiley, 2018-08-20) Ventura, Maria; Williamson, David; Lobefaro, Francesco; Jones, Mathew; Mattia, David; Nocito, Francesco; Aresta, Michele; Dibenedetto, Angela
The sustainable chemical industry encompasses a shift from the use of fossil carbon to renewable carbon. The synthesis of chemicals from nonedible biomass (cellulosic or oil) represents one of the key steps for “greening” the chemical industry. In this paper, we report the aerobic oxidative cleavage of C6 polyols (5-HMF, glucose, fructose and sucrose) to oxalic acid (OA) and succinic acid (SA) in water under mild conditions using M@CNT and M@NCNT (M=Fe, V; CNT=carbon nanotubes; NCNT=N-doped CNT), which, under suitable conditions, were recoverable and reusable without any loss of efficiency. The influence of the temperature, O2 pressure (Pmathematical equation ), reaction time and stirring rate are discussed and the best reaction conditions are determined for an almost complete conversion of the starting material and a good OA yield of 48 %. SA and formic acid were the only co-products. The former could be further converted into OA by oxidation in the presence of formic acid, resulting in an overall OA yield of >62 %. This process was clean and did not produce organic waste nor gas emissions.
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.
Tunable mixed oxides based on CeO2 for the selective aerobic oxidation of 5-(hydroxymethyl) furfural to FDCA in water
(Royal Society of Chemistry, 2018-07-31) Ventura, Maria; Nocito, Francesco; de giglio, Elvira; Cometa, Stefania; Altomare, Angela; Dibenedetto, Angela
Chemicals derived from 5-HMF, via selective oxidation of its pending arms are becoming increasingly important due to their applications. This paper discusses the use of Earth crust abundant new mixed oxides based on CeO2 able to perform the selective oxidation of 5-HMF to 2,5-furandicarboxylic acid (99%), in water, using oxygen as the oxidant.
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.