Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity.

The hydroxyl radical (OH) removes most atmospheric pollutants from air. The loss frequency of OH radicals due to the combined effect of all gas-phase OH reactive species is a measureable quantity termed total OH reactivity. Here we present total OH reactivity observations in pristine Amazon rainforest air, as a function of season, time-of-day and height (0?80 m). Total OH reactivity is low during wet (10 s1) and high during dry season (62 s1). Comparison to individually measured trace gases reveals strong variation in unaccounted for OH reactivity, from 5 to 15% missing in wet-season afternoons to mostly unknown (average 79%) during dry season. During dry-season afternoons isoprene, considered the dominant reagent with OH in rainforests, only accounts for B20% of the total OH reactivity. Vertical profiles of OH reactivity are shaped by biogenic emissions, photochemistry and turbulent mixing. The rainforest floor was identified as a significant but poorly characterized source of OH reactivity.

Estudo da síntese e propriedade magnética de ferritas de manganês/cobalto dopadas com níquel

For the chemical method of synthesis of co-precipitation were produced ferrite powders manganese-cobalt equal stoichiometric formula Mn (1-x) Co (x) Fe2O4, for 0 < x < 1, first reagent element using as the hydroxide ammonium and second time using sodium hydroxide. The obtained powders were calcined at 400 ° C, 650 ° C, 900 ° C and 1150 ° C in a conventional oven type furnace with an air atmosphere for a period of 240 minutes. Other samples were calcined at a temperature of 900 ° C in a controlled atmosphere of argon, to evaluate the possible influence of the atmosphere on the final results the structure and morphology. The samples were also calcined in a microwave oven at 400 ° C and 650 ° C for a period of 45 minutes possible to evaluate the performance of this type of heat treatment furnace. It was successfully tested the ability of this group include isomorphic ferrite with the inclusion of nickel cations in order to evaluate the occurrence of disorder in the crystalline structures and their changes in magnetic characteristics.To identify the structural, morphological, chemical composition and proportions, as well as their magnetic characteristics were performed characterization tests of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), thermogravimetric (TG), vibrating sample magnetometry (MAV) and Mössbauer spectroscopy. These tests revealed the occurrence of distortion in the crystal lattice, changes in magnetic response, occurrence of nanosized particles and superparamagnetism

Estudo de reatores eletroquímicos para remoção de Cu2+ , Zn2+, Fenol e BTEX em água produzida

The production of water has become one of the most important wastes in the petroleum industry, specifically in the up stream segment. The treatment of this kind of effluents is complex and normally requires high costs. In this context, the electrochemical treatment emerges as an alternative methodology for treating the wastewaters. It employs electrochemical reactions to increase the capability and efficiency of the traditional chemical treatments for associated produced water. The use of electrochemical reactors can be effective with small changes in traditional treatments, generally not representing a significant additional surface area for new equipments (due to the high cost of square meter on offshore platforms) and also it can use almost the same equipments, in continuous or batch flow, without others high costs investments. Electrochemical treatment causes low environmental impact, because the process uses electrons as reagent and generates small amount of wastes. In this work, it was studied two types of electrochemical reactors: eletroflocculation and eletroflotation, with the aim of removing of Cu2+, Zn2+, phenol and BTEX mixture of produced water. In eletroflocculation, an electrical potential was applied to an aqueous solution containing NaCl. For this, it was used iron electrodes, which promote the dissolution of metal ions, generating Fe2+ and gases which, in appropriate pH, promote also clotting-flocculation reactions, removing Cu2+ and Zn2+. In eletroflotation, a carbon steel cathode and a DSA type anode (Ti/TiO2-RuO2-SnO2) were used in a NaCl solution. It was applied an electrical current, producing strong oxidant agents as Cl2 and HOCl, increasing the degradation rate of BTEX and phenol. Under different flow rates, the Zn2+ was removed by electrodeposition or by ZnOH formation, due the increasing of pH during the reaction. To better understand the electrochemical process, a statistical protocol factor (22) with central point was conducted to analyze the sensitivity of operating parameters on removing Zn2+ by eletroflotation, confirming that the current density affected the process negatively and the flow rate positively. For economical viability of these two electrochemical treatments, the energy consumption was calculated, taking in account the kWh given by ANEEL. The treatment cost obtained were quite attractive in comparison with the current treatments used in Rio Grande do Norte state. In addition, it could still be reduced for the case of using other alternative energy source such as solar, wind or gas generated directly from the Petrochemical Plant or offshore platforms

A Study of the Microwave Carbothermic Reduction of Chromite Ore

Microwave reduction testing using activated charcoal as a reducing agent was performed on a sample of Black Thor chromite ore from the Ring of Fire deposit in Northern Ontario. First, a thermodynamic model was constructed for the system. Activity coefficients for several species were found in the literature. The model predicted chromium grades of 61.60% and recoveries of 93.43% for a 15% carbon addition. Next, reduction testing on the chromite ore was performed. Tests were performed at increasing power levels and reduction times. Testing atmospheres used were air, argon, and vacuum. The reduced product had maximum grades of 72.89% and recoveries of 80.37%. These maximum values were obtained in the same test where an argon atmosphere was used, with a carbon addition of 15%, optimal power level of 1200 W (actual 1171 W), and a time of 400 seconds. During this test, 17.53% of the initial mass was lost as gas, a carbon grade of 1.95% was found for the sintered core product. Additional work is recommended to try and purify the sintered core product as well as reduce more of the initial sample. Changing reagent schemes or a two step reduction / separation process could be implemented.

Heterogeneous Catalysts: Design, Applications and Research Insights

The cyclization of pseudoionone yields a mixture of alpha-ionone, beta-ionone and gamma-ionone. By careful control of reagent and reaction conditions, either the alpha- and beta- isomer can be favoured. The alpha-ionone has violet odour and is widely used in perfumery and flavours. beta-Ionone is the main precursor of Vitamin A and beta-carotene. Traditionally, strong homogeneous catalysts, like sulphuric acid and phosphoric acid have been used. These problems can be overcome by the use of solid acid catalysts. This work reports the cyclization of pseudoionone over USY zeolites, at 80ºC. USY It is observed that the initial activity increases with the Si/Al ratio of zeolite until a maximum, which is obtained with USY3. With higher Si/Al ratio, a decrease in the catalytic activity is observed. Selectivity to ionone isomers is around 42 %, at 75% of pseudoionone conversion, after 24 h of reaction. USY3 zeolite was reused four times with the same catalyst sample in the same condicions. It was observed a stabilization of the catalytic activity, after the second use.

THERMOGRAVIMETRIC ALTERATIONS OF CASSAVA STARCH GRANULES INDUCED BY HYDROGEN PEROXIDE, UV RAYS AND MICROWAVE

Starches are applied in several fields of industry. Amylose and amylopectin (natural polymers) constitute the starch in vegetable cells. In some processes native starches cannot support high stress conditions (high temperatures/acidity). Then, modification methods are developed aiming the improving of starch technological utilization. Oxidative modification with H2O2 has been the subject of many researches. UV rays as well microwave irradiation can be used. The aim was to confirm possible thermogravimetric alterations in native cassava starch (A) granules due to a double starch modification: 1st step) H2O2 standard solutions 0.1 mol L-1 (B), 0.2 mol L-1 (C) and 0.3 mol L-1 (D) and UV rays exposure for 1h; 2nd step) microwave irradiation for 5 min. The results of thermogravimetric curves (TG-DTA) show that the behaviors of the starch proprieties were modified. Highlighting, the modified samples C and D showed a decrease on the thermal stability step. This alteration turned them suitable to many field of industry like the paper one.

Gold Catalyzed Functionalization Of Alkynes And Allenamides

The gold(I)-catalyzed chemoselective dearomatization of β-naphthols is reported through a straightforward approach via [3,3]-sigmatropic rearrangement /allene-cyclyzation cascade processes. Easily accessed naphthyl-propargyl ethers and derivatives in this work are employed as starting materials. Delightfully, an array of deoramatized dyhydrofuryl -naphthalen-2(1H)-ones featured densely functional groups are obtained in high yields (up to 98%) in 10 min reaction time under extremely mild reaction conditions like reagent grade solvent and exposure to air. The potential of accessing to high enantioselectivety on the dearomatized dyhydrofuryl- naphthalen-2(1H)-ones is also approved by the good ee (65%) relying on (R)-xylyl- BINAP(AuCl)2. In addition, complete theoretical elucidation of the reaction pathway is also proposed which addresses a rationale for essential motivation such as regio- and chemoselectivity. Moreover, an efficient gold catalyzed intermolecular dearomatization of substituted β-naphthols with allenamides is presented here. PPh3AuTFA (5 mol %) approves the efficient dearomatively allylation protocol under mild conditions and exhibits high tolerance on substrates scope (24 examples) in good to excellent yield accompanied with high regioselectivity and stereoselectivity. Moreover, the synergistic catalytic system also highlight the synergistic function between the [PPh3Au]+ (π-acid) and TFA− (Lewis base). At last, a new chiral BINOL phosphoric acid silver salt is successfully synthesized and used as the chiral counter anion, which strongly promotes the enantioselectivity (up to 92%). At last but not least, crucially, SmI2 induced enantioselective formal synthesis of strychnine, a complex alkaloid and a classical target used to benchmark new synthetic methods is developed. Enantioselective dearomatising radical cyclisation on to the indole unit and further ET will then give organosamarium that is quenched diastereoselectively by the ester to deliver Strychnine in 7 steps.

Materiali ceramici a struttura Aurivillius per la produzione di solar fuels

Solar fuels from CO2 is a topic of current large scientific and industrial interest. In particular, photo-electrochemical cells (PECs) represent today one of the most promising technology for storing sun energy as chemical bonds exploiting carbon dioxide as starting reagent. In this thesis, the possibility of using Aurivillius-type compounds for the production of solar fuels was deeply investigated. Aurivillius-type perovskites, with general formula Bi(n+1)Fe(n-3)Ti3O(3n+3), were synthesized and fully characterized to study the influence of the number of perovskite layers as well as of the synthesis parameters onto their final properties. In particular, 8 different systems were considered increasing the amount of iron and, as a consequence, the number of perovskite layers. These compounds were synthesized through a standard solid-state reaction method as well as via a sol-gel technique and characterized by XRD, SEM and BET analyses. The band gap value and the photocatalytic activity towards Rhodamine B decomposition were assessed as well. For each system, a screen-printing ink was formulated to be deposited as photo-electrodes onto transparent conducting supports. The photo-electrodes were morphologically characterized by XRD and SEM analysis, and their electrochemical properties (cyclic and linear voltammetry, EIS, Mott-Schottky analysis) were determined. Finally, the most promising materials were tested as photo-cathode inside PEC cell under different illumination conditions, to quantify their ability to convert CO2. The obtained results show the potentiality of Aurivillius-type compounds as innovative material for carbon dioxide photo-electrochemical reduction.

Synthesis of enantiopure cyclopentanones by desymmetrization of allylic cyclobutanols

The interest in five-membered ring molecules derives from their important application in many different fields, such as pharmaceutical and agrochemical areas. A common strategy for their formation is four-membered ring expansion, which also allows to add molecular complexity and functional handles within one single operation starting from readily available starting materials. Organocatalysis can be exploited to promote the reaction and to obtain a good enantio- and diastereoselection. This technique involves the exclusive use of organic molecules as catalysts, without resorting to metals. The aim of this work is to obtain enantiopure cyclopentanones starting from achiral allylic cyclobutanols. The reaction consists in a ring expansion promoted by the addition of a halogen to the double bond of the substrate, with formation of a haliranium ion as intermediate, followed by a semipinacol rearrangement to afford the cyclopentanone. The reaction is catalysed by a chiral phosphoric acid that, besides accelerating the rate of the reaction, transmits a specific chirality thanks to its chiral structure, following the asymmetric catalysis principles. Starting from symmetric trans-allylic cyclobutanols, the whole reaction is a desymmetrization and leads to the formation of two new stereogenic centres: a mixture of diastereoisomers is obtained, each as couple of enantiomers; the ratio between the possible configurations is determined by the relative position that the chiral catalyst and the reagent occupy during the reaction. Since the reaction is already optimized, the original aim was to study the scope: first, the synthesis of a set of allylic cyclobutanols and their relative precursors, in order to have a wider range of substrates; then, the identification of the type of substrate that undergoes the expansion, with the study of enantio- and diastereoselectivity obtained in each case. Due to the Covid-19 emergency, most of the work was developed as a bibliographic study.

Theoretical and experimental studies of gold catalysts for glucose oxidation

The glucaric acid (GLA) has been identified as a “top value-added chemical from biomass” that can be employed for many uses; for instance, it could be a precursor of adipic acid, a monomer of Nylon-6,6. GLA can be synthetized by the oxidation of glucose (GLU), passing through the intermediate gluconic acid (GLO). In recent years, a new process has been sought to obtain GLA in an economic and environmental sustainable way, in order to replace the current use of HNO3 as a stoichiometric oxidant, or electrocatalysis and biochemical synthesis, which show several disadvantages. Thereby, this work is focused on the study of catalysts based on gold nanoparticles supported on activated carbon for the oxidation reaction of GLU to GLA using O2 as an oxidant agent and NaOH as base. The sol-immobilization method leads us to obtain small and well dispersed nanoparticles, characterized by UV-Vis, XRD and TEM techniques. Repeating the reaction on different batches of catalyst, both the synthesis and the reaction were confirmed to be reproducible. The effect of the reaction time feeding GLO as reagent was studied: the results show that the conversion of GLO increases as the reaction time increases; however, the yields of GLA and others increase up to 1 hour, and then they remain constant. In order to obtain information on the catalytic mechanism at the atomistic level, a computational study based on density functional theory and atomistic modeling of the gold nano-catalyst were performed. Highly symmetric (icosahedral and cubo-octahedral) and distorted Au55 nanoparticles have been optimized along with Au(111) and Au(100) surfaces. Distorted structures were found to be more stable than symmetrical ones due to relativistic effects. On these various models the adsorptions of various species involved in the catalysis have been studied, including OH- species, GLU and GLO. The study carried out aims to provide a method for approaching to the study of nanoparticellary catalytic systems.

Deidrogenazione ossidativa del n-butano catalizzata da ossidi metallici difettivi

The oxidative dehydrogenation (ODH) of n-butane is a promising way to synthetize butenes and 1,3-butadiene, currently produced by steam cracking or direct dehydrogenation of n-butane. The addition of oxygen as a reagent leads to the formation of water, a very stable by-product, which makes the process exothermic.In this work, the ODH of n- butane was investigate to selectively obtain butenes and 1,3-butadiene. Four catalysts based on metal oxides (V2O5, La2O3, CeO2 and TiO2) were mixed with Mg metallic powder and reduced at 650 °C for 5 h in 5% H2/Ar atmosphere, with the purpose of creating oxygen vacancies in the crystal lattice of the oxides. Subsequently, the effect of the Mg concentration, and thus the oxygen vacancies concentration, was studied. The titanium oxide-based catalysts were the most active, in terms of butane conversion and selectivity to butenes and 1,3 butadiene. Overall, this study shows that the formation of oxygen vacancies on metal oxides can be influenced by the addition of metallic Mg during the synthesis. In the case of TiO2, this leads to an increase on the activity compared to the untreated sample.

CO2 utilization and alternative solvents: effective tools for sustainable applications

The growing concentration of CO2 in the atmosphere and its harmful consequences has led the scientific community to direct its efforts towards sustainable processes. Among the possible approaches, the use of CO2 and alternative solvents are two strategies that are having widespread diffusion. In this work the reuse of CO2 is expressed by using it as a reaction reagent and as trigger to change the physical properties of a catalyst thus facilitating its recovery. As regards the CO2 use as reagent, two catalytic systems have been developed for the conversion of CO2 and epoxides into cyclic carbonates, used in the synthesis of polymers and as aprotic solvents. Homogeneous catalysts made by choline-based eutectic mixtures and heterogeneous catalysts made from biopolymers and waste pyrolysis have been synthesized and tested on this reaction. The carbonate interchange reaction (CIR) of a diol with a linear carbonate (as dimethyl carbonate) is an interesting alternative, for the synthesis of cyclic carbonates; as the second application of CO2 as polarity trigger, it was used for catalyst recovery. In fact DBU, here used as catalyst, is part of the so called “switchable solvents”: they can pass from a less-polar to a more-polar form (and from being soluble to non-soluble in the reaction mixture) when reacting with CO2 in presence of water or alcohols. Also in this case, heterogeneous catalysts made from biopolymers and waste pyrolysis have been synthesized and tested on CIR. As for the use of alternative solvents, this work focuses on the use of Deep Eutectic Solvents (DESs). They are a new generation of solvents composed by a mixture of two or more substances, liquid at room temperature, and non-volatile. New and biobased DESs were here used: i) as reaction media to carry out chemoenzymatic epoxidation; ii) in the extraction of astaxanthin from microalgae culture.

Low-molecular-weight gels: from the rational design to the application of versatile soft materials

Low-molecular-weight (LMW) gels are a versatile class of soft materials that gained increasing interest over the last few decades. They are made of a small percentage, often lower than 1.0 %, of organic molecules called gelators, dispersed in a liquid medium. Such molecules have a molecular weight usually lower than 1 kDa. The gelator molecules start to interact after the addition of a trigger, and form fibres, whose entanglement traps the solvent through capillary forces. A plethora of LMW gelators have been designed, including short peptides. Such gelators present several advantages: the synthesis is easy and can be easily scaled up; they are usually biocompatible and biodegradable; the gelation phenomenon can be rationalised by making small variation on the peptide scaffold; they find application in several fields. In this thesis, an overview of several peptide based LMW gels is presented. In each study, the gelation conditions were carefully studied, and the final materials were thoroughly investigated. First, the gelation ability of a fluorinated phenylalanine was assessed, to understand how the presence of a rigid moiety and the presence of fluorine may influence the gelation. In this context, a method for the dissolution of sensitive gelators was studied. Then, the control over the gel formation was studied both over time and space, taking advantage of either the pH-annealing of the gel or the reaction-diffusion of a hydrolysing reagent. Some gels were probed for various applications. Due to their ability of trapping water and organic solvents, we used gels for trapping pollutants dissolved in water, as well as a medium for the controlled release of either fragrances or bioactive compounds. Finally, the interaction of the gel matrix with a light-responsive molecule was assessed to understand wether the gel properties or the interaction of the additive with light were affected.

Development of processes for the valorization of lignocellulosic biomass based on renewable energies

The world grapples with climate change from fossil fuel reliance, prompting Europe to pivot to renewable energy. Among renewables, biomass is a bioenergy and bio-carbon source, used to create high-value biomolecules, replacing fossil-based products. Alkyl levulinates, derived from biomass, hold promise as bio-additives and biofuels, especially via acid solvolysis of hexose sugars, necessitating further exploration. Alkyl levulinate's potential extends to converting into γ-valerolactone (GVL), a bio-solvent produced via hydrogenation with molecular-hydrogen. Hydrogen, a key reagent and energy carrier, aids renewable energy integration. This thesis delves into a biorefinery system study, aligning with sustainability goals, integrating biomass valorization, energy production, and hydrogen generation. It investigates optimizing technologies for butyl levulinate production and subsequent GVL hydrogenation. Sustainability remains pivotal, reflecting the global shift towards renewable and carbon bio-resources. The research initially focuses on experimenting with the optimal technology for producing butyl levulinate from biomass-derived hexose fructose. It examines the solvolysis process, investigating optimal conditions, kinetic modeling, and the impact of solvents on fructose conversion. The subsequent part concentrates on the technological aspect of hydrogenating butyl levulinate into GVL. It includes conceptual design, simulation, and optimization of the fructose-to-GVL process scheme based on process intensification. In the final part, the study applies the process to a real case study in Normandy, France, adapting it to local biomass availability and wind energy. It defines a methodology for designing and integrating the energy-supply system, evaluating different scenarios. Sustainability assessment using economic, environmental, and social indicators culminates in an overall sustainability index, indicating scenarios integrating the GVL biorefinery system with wind power and hydrogen energy storage as promising due to high profitability and reduced environmental impact. Sensitivity analyses validate the methodology's reliability, potentially extending to other technological systems.

TIDES unveiled: pioneering green peptides synthesis and oligonucleotides innovations in science

My PhD research focused on the development of environmentally sustainable methods for peptide synthesis. The traditional and toxic solvents and bases used in solid-phase peptide synthesis (SPPS) were replaced with eco-friendly alternatives to reduce the environmental impact. In particular, N-octylpyrrolidone was found to be an effective green solvent in combination with dimethyl carbonate, resulting in a 63-66% reduction in process mass intensity (PMI). In addition, a green base, DEAPA, was identified for Fmoc removal, which showed comparable results to piperidine, while being less regulated and toxic, and able to better control aspartimide-related side reactions. The study extended beyond SPPS to explore liquid-phase peptide synthesis (LPPS) and solution-phase peptide synthesis (SolPPS) using propylphosphonic anhydride (T3P®) as a coupling reagent. The developed green SolPPS using Cbz amino acids achieved exceptional efficiency, minimal racemisation and a PMI of 30 to introduce a single amino acid in the iterative process. This PMI value is the lowest ever reported for an oligopeptide synthesis protocol. This technique was extended to N-Boc amino acids in DCM, requiring aqueous workups and achieving 95% purity of Leu-Enkephalin. Finally, T3P® was found to be suitable for LPPS. An anchor, mimicking a resin, was used to allow precipitation or solubilisation of the growing anchored-peptide, depending on the polarity of the solvent used. Anisole and DCM resulted in a pentapeptide purity of over 95%. While at Oxford University, I synthesized a cleavable fragment that is sensitive to cathepsin B (CatB) and incorporated it into a cyclic antisense oligonucleotide (ASO) targeting the metastasis-associated lung adenocarcinoma transcript 1 (MALAT1). ASO demonstrated good stability in a simulated in vivo environment using human serum and high affinity with complementary RNA. The Cyclic-ASO was opened by CatB in optimal conditions. Experiments highlight therapeutic potential and a novel method for controlling cyclic oligonucleotide activity, potentially enhancing cellular uptake.