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    Vegetable oils epoxidation : from batch to continuous process

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    Epoxides are a class of compounds characterized by the oxirane functional group, a polar three-terms strain ring composed by two carbon atoms and an oxygen atom. These two properties make the oxirane ring a highly reactive moiety. For this reason, epoxides are important and valuable industrial building blocks for the synthesis of several organic compounds, e.g., di- or polyalcohols, lactones, β-hydroxesters, carbonates etc. In this scenario, Epoxidized Vegetable Oils (EVOs), which are obtained from renewable feedstock, represent noteworthy green platforms to produce chemicals and biomaterials. Epoxides originating from vegetable oils, as well as from derivates of vegetable oils, have already been successfully applied, among others, as plasticizers in the poly(vinyl-chloride) resins, partially replacing phthalates, as intermediates to produce polyurethane, representing an environmentally friendly route compared to the toxic isocyanate process, and as bio-lubricants. Thus, it is possible to understand the ongoing interest, in both academic and industrial research, to this class of value-added chemical compounds. Nevertheless, the industrial synthesis still relies on a semibatch technology, limiting the productivity and selectivity to this platform chemical. The epoxidation via the Prilezhaev reaction method is the synthesis pathway studied in the present work to produce of epoxides from vegetable oils, both edible and not. The choice of studying this synthesis path is because it is the only one with relevant current industrial application in the epoxidation of this promising feedstock and, more importantly, it belongs to the category of green chemistry and green process technology. The reaction system is composed of two immiscible liquid phases and consecutive reactions take place in the two phases and at the interphase between them. The work was mainly focused in the study of the different reaction steps of the Prilezhaev reaction method in order to efficiently shift to a continuous operation. A new and fast analytical method based on protonic nuclear magnetic resonance (1H-NMR) was developed in alternative to the traditional volumetric analytical methods to evaluate the double bond conversion and the selectivity to the target product. At first, the system was studied in semibatch operation in the presence of linseed oil to evaluate the reactivity of this highly unsaturated organic substrate. The aim was to develop a biphasic kinetic model able to predict the behavior of organic substrates with different amounts of double bonds, in a backmixed reactor, in terms of conversion, selectivity and, more importantly, thermal profile. Next, the research was focused on the kinetic study of the percarboxylic acid formation and its decomposition. The former reaction, indeed, is the preliminary reaction step before the epoxidation reaction. An important aspect of the reaction system, because of the immiscibility of the two phases, is the partition of the species, especially the oxygen donor. For this reason, the partition coefficients of formic acid, the precursor of the oxygen donor, were experimentally determined. Finally, the epoxidation reaction via the Prilezhaev concept was successfully carried out in a continuous device obtaining satisfactory results in terms of conversion and selectivity adopting milder conditions than the semibatch process.Epoxider är kemiska komponenter som karakteriseras av funktionella oxirangrupper, Oxiran är en triangulär ring, som består av två kolatomer och en syreatom. Denna struktur innebär att oxiranringen är synnerligen reaktiv. På grund av den höga reaktiviteten är epoxiderna viktiga och värdefulla byggstenar i industriell syntes av flera organiska komponenter, t.ex. di- och polyalkoholer, β-hydroxiestrar och karbonater. I detta scenario representerar epoxiderade växtoljor, som erhålls från förnyelsebar råvara, en betydelsefull grön plattform för produktion av kemikalier och biomaterial. Epoxider som härstammar från växtoljor samt oljederivat har redan tillämpats bl.a. som biosmörjmedel, som mjukgörare i polyvinylkloridhartser, som ersättare av ftalater, och som intermediärer för framställning av polyuretan, där användning av epoxider möjliggör en miljövänlig reaktionsrutt jämfört med den giftiga isocyanatreaktionen. På grund av detta är det lätt att förstå det intensiva akademiska och industriella forskningsintresset för dessa mycket värdefulla kemiska komponenter. Beklagligtvis baserar sig den industriella syntesmetoden av epoxiderade växtoljor fortfarande på halvkontinuerlig teknologi, vilket begränsar både produktiviteten och selektiviteten av dessa eftertraktade plattformkemikalier. Epoxidering av växtoljor enligt Prilezhaevmetoden är den syntesrutt som studerades i detta doktorsarbete för produktion av epoxider utgående från ätbara och icke-ätbara växtoljor. Valet av syntesmetoden baserade sig på det faktum att Prilezhaevmetoden är hittills den enda industriellt relevanta tillämpningen för epoxidering av den miljövänliga råvaran och metoden hör definitivt till kategorierna grön kemi och grön processteknologi. Reaktionssystemet består av två icke-blandbara vätskefaser, där konsekutiva perhydrolys-, epoxiderings- och ringöppningsreaktioner pågår inne i dessa faser och vid fasgränsytan. Arbetet fokuserades huvudsakligen på studier av de olika reaktionsstegen i Prilezhaevmetoden för att effektivt kunna övergå från den nuvarande prekära halvkontinuerliga produktionsprocessen till en kontinuerlig process, som skulle innebära en snabbare syntes och förbättad processäkerhet. En ny och snabb analysmetod baserad på kärnmagnetisk resonansspektroskopi (1H-NMR) utvecklades som alternativ till traditionella volymetriska metoder för att bestämma dubbelbindningarnas omsättning och produktselektivitet. Först studerades den halvkontinuerliga reaktorteknologin i närvaro av linfröolja för att evaluera reaktiviteten av denna i högsta grad omättade organiska råvara. Målet var att utveckla en kinetisk modell för reaktionshastigheterna i tvåfassystemet så att beteendet av organiska molekyler med olika antal dubbelbindningar kan kartläggas i avseende på råvarans omsättning, produktens selektivitet och värmeeffekter. I följande steget fokuserades forskningen på kinetiska studier av bildningen och sönderfallet av perkarboxylsyror. Bildningen av perkarboxylsyra ur tillsatt karboxylsyra, t.ex. myrsyra och väteperoxid är de facto det första reaktionssteget före själva epoxideringsreaktionen. En speciellt viktig aspekt beträffande själva reaktionssystemet är att vatten- och oljefaserna är icke-blandbara, vilket innebär att komponenternas fördelning mellan faserna är av oerhört stor betydelse. Därför bestämdes fördelningskoefficienten av syrekällan, myrsyra experimentellt. I sista skedet kulminerade arbetet i utvecklingen av en helt ny kontinuerlig reaktorteknologi för att uppnå tillfreds-ställande resultat för reaktantomsättningen och produktselektiviten. Den kontinuerliga teknologin som baserar sig på en eller flera seriekopplade kolonnreaktorer visade sig vara överlägsen jämfört med det existerande halvkontinuerliga förfarandet: en klart högre reaktantomsättning och produktselektivitet uppnåddes i den kontinuerliga reaktoranläggningen som också modellerades matematiskt.Gli epossidi sono una classe di composti caratterizzati da un gruppo funzionale ossiranico, un anello a tre termini rigido e polare, composto da due atomi di carbonio ed un atomo di ossigeno. Tali caratteristiche fanno dell’anello ossiranico un gruppo altamente reattivo. Per questa ragione, gli epossidi sono importanti e preziosi intermedi industriali per la sintesi di un’ampia gamma di composti organici, i.e. di- o polialcoli, lattoni, β-idrossiesteri, carbonati etc. A tal proposito, gli oli vegetali epossidati, ottenuti a partire da fonti rinnovabili, rappresentano materiali di partenza notevoli e sostenibili per la produzione di agenti chimici e biomateriali. Gli epossidi ottenuti da oli vegetali, così come dai derivati degli oli vegetali, sono già stati ampiamente utilizzati come plasticizzanti nelle resine poliviniliche, sostituendo parzialmente gli ftalati, come intermedi per la produzione di poliuretano, rappresentando una via di sintesi ecosostenibile rispetto il processo via isocianato, e come biolubrificanti. Quindi, è possibile capire l’attuale interesse, sia da un punto di vista accademico che industriale, verso questa classe di composti chimici. Ciononostante, la sintesi industriale fa ancora affidamento su un processo semicontinuo, limitandone produttività e selettività. Nel presente lavoro di tesi è stata studiata nel dettaglio la reazione di epossidazione, condotta secondo il metodo Prilezhaev, attualmente considerata la via più comune di sintesi per la produzione di epossidi a partire da oli vegetali, edibili e non. La scelta nello studiare tale processo risiede nel fatto che quest’ultimo è l’unico metodo con ampia applicazione nell’attuale pratica industriale per la produzione di epossidi a partire da materiali di partenza promettenti quali gli oli e, molto più importante, tale sintesi appartiene alla categoria della chimica verde e dei processi ecosostenibili. Il sistema di reazione si compone di due liquidi immiscibili e alcune reazioni consecutive che avvengono sia nelle due fasi che all’interfaccia tra le stesse. Il lavoro è stato prevalentemente focalizzato sullo studio dei differenti passaggi nella reazione secondo il metodo Prilezhaev, con lo scopo di trasferire efficientemente il processo in continuo. Un metodo di analisi nuovo e rapido incentrato sulla risonanza magnetica protonica (1H-NMR) è stato sviluppato come alternativa ai tradizionali metodi volumetrici per la valutazione della conversione dei doppi legami e selettività del prodotto desiderato. Inizialmente, il sistema reattivo è stato studiato in presenza di olio di lino in un reattore semicontinuo per valutare la reattività di un substrato organico ad alto contenuto di doppi legami. Lo sviluppo di un modello reattoristico in grado di predire il comportamento di substrati organici a diverso contenuto di doppi legami in un reattore miscelato, in termini di conversione, selettività e, molto più importante, profilo termico, ero lo scopo principale dell’investigazione. Successivamente, la ricerca si è focalizzata sullo studio della cinetica della reazione di formazione e decomposizione dell’acido percarbossilico. La prima reazione infatti è propedeutica all’epossidazione. Un aspetto importante del sistema reattivo, a causa dell’immiscibilità delle due fasi, è la ripartizione delle specie, specialmente la specie ossidante. Per questa ragione, il coefficiente di partizione dell’acido formico, precursore della specie ossidante, è stato determinato sperimentalmente. Infine, il processo di epossidazione secondo il metodo Prilezhaev è stato condotto con successo in un’apparecchiatura operante in continuo, ottenendo eccellenti valori di conversione e selettività in condizioni meno severe rispetto al processo semicontinuo

    Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets

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    Aufgrund ihres Leichtbaupotenzials bei relativ geringen Kosten gewinnen glasfaserverstärkte Polymere in industriellen Anwendungen zunehmend an Bedeutung. Sie verbinden die hohe Festigkeit von Glasfasern mit der Beständigkeit von z.B. duroplastischen Harzen. Bei der Verarbeitung von faserverstärkten Duroplasten kommt es zu einer chemischen Reaktion des Harzes. Die chemische Reaktion geht mit einer chemischen Schrumpfung einher. In Verbindung mit der thermischen Ausdehnung kann das Material bereits beim Herstellungsprozess beschädigt werden. Auch wenn das Komposit nicht vollständig versagt, kann es zu Mikrorissbildung kommen. Diese Schäden können die Blastbarkeit des Bauteils und damit seine Lebensdauer beeinträchtigen. Faserverstärkte Duroplaste enthalten Strukturen auf verschiedenen Längenskalen, die das Verhalten des Gesamtbauteils beeinflussen und daher für eine genaue Vorhersage der Rissbildung berücksichtigt werden müssen. Das Verständnis der Mechanismen der Rissbildung auf den verschiedenen Längenskalaen ist daher von großem Interesse. Auf der Grundlage von Molekulardynamiksimulationen wird ein Harzsystem zusammen mit einer Faseroberfläche und einer Schlichte auf der Nanoskala betrachtet und ein systematisches Verfahren für die Entwicklung eines ausgehärteten Systems vorgestellt. Eine zweistufige Reaktion, eine Polyurethanreaktion und eine radikale Polymerisation, wird auf der Grundlage eines etablierten Ansatzes modelliert. Anhand des fertig ausgehärteten Systems werden Auswertungen über gemittelte Größen und entlang der Normalenrichtung der Faseroberfläche durchgeführt, was eine räumliche Analyse der Faser-Schlichtharz-Grenzfläche erlaubt. Auf der Mikrolängenskala werden die einzelnen Fasern räumlich aufgelöst. Mit Hilfe der Kontinuumsmechanik und der Phasenfeldmethode wird das Versagen während des Aushärtungsprozesses auf dieser Längenskala untersucht. In der Materialwissenschaft wird die Phasenfeldmethode häufig zur Modellierung der Rissausbreitung verwendet. Sie ist in der Lage, das komplexe Bruchverhalten zu beschreiben und zeigt eine gute Übereinstimmung mit analytischen Lösungen. Dennoch sind die meisten Modelle auf homogene Systeme beschränkt, und nur wenige Ansätze für heterogene Systeme existieren. Es werden bestehende Modelle diskutiert und ein neues Modell für heterogene Systeme abgeleitet, das auf einem etablierten Phasenfeldansatz zur Rissausbreitung basiert. Das neue Modell mit mehreren Rissordnungsparametern ist in der Lage, quantitatives Risswachstum vorherzusagen, wo die etablierten Modelle eine analytische Lösung nicht reproduzieren können. Darüber hinaus wird ein verbessertes Homogenisierungsschema, das auf der mechanischen Sprungbedingung basiert, auf das neuartige Modell angewandt, was zu einer Verbesserung der Rissvorhersage selbst bei unterschiedlichen Steifigkeiten und Risswiderständen der betrachteten Materialien führt. Zudem wird zur Erzeugung digitaler Mikrostrukturen, die für Aushärtungssimulationen im Mikrobereich verwendet werden, ein Generator für gekrümmte Faserstrukturen eingeführt. Anschließend wird die Verteilung mechanischer und thermischer Größen für verschiedene Abstraktionsebenen der realen Mikrostruktur sowie für verschiedene Faservolumenanteile verglichen. Schließlich wird das neue Rissausbreitungsmodell mit dem Aushärtungsmodell kombiniert, was die Vorhersage der Mikrorissbildung während des Aushärtungsprozesses von glasfaserverstärktem UPPH-Harz ermöglicht

    Artificial compressibility method for high-pressure transcritical fluids at low Mach numbers

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    Supercritical fluids possess unique properties that makes them relevant in various scientific and engineering applications. However, the experimental investigation of these fluids is challenging due to the high pressures involved and their complex thermophysical behavior. To overcome these limitations, computational researchers employ scale-resolving methods, such as direct numerical simulation and large-eddy simulation to study them. Nonetheless, these methods require substantial computational resources, especially in the case of low-Mach-number regimes due to the disparity between acoustic and hydrodynamic/thermal time scales. This work, therefore, addresses this problem by extending the artificial compressibility method to high-pressure transcritical fluids. This method is based on decoupling the thermodynamic and hydrodynamic parts of the pressure field, such that the acoustic time scales can be externally modified without severely impacting the flow physics of the problem. In addition, the method proposed has two key characteristics: (i) the splitting method presents low computational complexity, and (ii) an automatic strategy for selecting the speedup factor of the approach is introduced. The effectiveness of the resulting methodology is demonstrated through comprehensive numerical tests of increasing complexity, showcasing its ability to accurately simulate a wide range of high-pressure transcritical flows including turbulence. The results obtained indicate that the approach proposed can readily lead to computational speedups larger than without significantly compromising the accuracy of the numerical solutions.This work is funded by the European Union (ERC, SCRAMBLE, 101040379). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.Peer ReviewedPostprint (published version

    Exploring the DNA2-PNA heterotriplex formation in targeting the Bcl-2 gene promoter: A structural insight by physico-chemical and microsecond-scale MD investigation

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    Peptide Nucleic Acids (PNAs) represent a promising tool for gene modulation in anticancer treatment. The uncharged peptidyl backbone and the resistance to chemical and enzymatic degradation make PNAs highly advantageous to form stable hybrid complexes with complementary DNA and RNA strands, providing higher stability than the corresponding natural analogues. Our and other groups’ research has successfully shown that tailored PNA sequences can effectively downregulate the expression of human oncogenes using antigene, antisense, or anti-miRNA approaches. Specifically, we identified a seven bases-long PNA sequence, complementary to the longer loop of the main G-quadruplex structure formed by the bcl2midG4 promoter sequence, capable of downregulating the expression of the antiapoptotic Bcl-2 protein and enhancing the anticancer activity of an oncolytic adenovirus. Here, we extended the length of the PNA probe with the aim of including the double-stranded Bcl-2 promoter among the targets of the PNA probe. Our investigation primarily focused on the structural aspects of the resulting DNA2-PNA heterotriplex that were determined by employing conventional and accelerated microsecond-scale molecular dynamics simulations and chemical-physical analysis. Additionally, we conducted preliminary biological experiments using cytotoxicity assays on human A549 and MDA-MB-436 adenocarcinoma cell lines, employing the oncolytic adenovirus delivery strategy

    Temperature Reduction Technologies Meet Asphalt Pavement: Green and Sustainability

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    This Special Issue, "Temperature Reduction Technologies Meet Asphalt Pavement: Green and Sustainability", covers various subjects related to advanced temperature reduction technologies in bituminous materials. It can help civil engineers and material scientists better identify underlying views for sustainable pavement constructions

    Advanced Monte Carlo simulation techniques to study polymers under equilibrium conditions

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    The advances in materials and biological sciences have necessitated the use of molecular simulations to study polymers. The Markov chain Monte Carlo simulations enable the sampling of relevant microstates of polymeric systems by traversing paths that are impractical in molecular dynamics simulations. Several advances in applying Monte Carlo simulations to polymeric systems have been reported in recent decades. The proposed methods address sampling challenges encountered in studying different aspects of polymeric systems. Tracking the above advances has become increasingly challenging due to the extensive literature generated in the field. Moreover, the incorporation of new methods in the existing Monte Carlo simulation packages is cumbersome due to their complexity. Identifying the foundational algorithms that are common to different methods can significantly ease their implementation and make them accessible to the broader simulation community. The present chapter classifies the Monte Carlo methods for polymeric systems based on their objectives and standard features of their algorithms. We begin the article by providing an overview of advanced Monte Carlo techniques used for polymeric systems and their specific applications. We then classify the above techniques into two broad categories: 1) Monte Carlo moves and 2) Advanced sampling schemes. The former category is further divided to distinguish the Monte Carlo moves in the canonical and other ensembles. The advanced sampling schemes attempt to improve Monte Carlo sampling via approaches other than Monte Carlo moves. We use the above classification to identify common features of the methods and derive general expressions that explain their implementation. Such a strategy can help readers select the methods that are suitable for their study and develop computer programs that can be easily modified to implement new methods.Comment: 22 pages, 4 figures, 2 table

    Molecular dynamics simulation of interfacial tension of the CO2-CH4-water and H2-CH4-water systems at the temperature of 300 K and 323 K and pressure up to 70 MPa

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    Subsurface geologic formations such as depleted hydrocarbon reservoirs, deep saline aquifers and shale formations have been considered promising targets for carbon dioxide and hydrogen storage. A solid understanding of the interfacial properties of multiphase systems, including binary (pure gas-water) and ternary (gas mixtures and water), is vital to assess for reliability and storage capacity of the geological formations. However, most previous experimental and simulation studies for interfacial properties have mainly focused on binary systems at low-medium pressure. Only a few experimental and simulation studies investigated the interfacial tension at high pressure (above 20 MPa) for the CO2-CH4-H2O system, and no simulation data are available for the H2-CH4-H2O system. In this study, Molecular dynamics simulations were used to predict the interfacial tension (γ) for both the binary and ternary system at 300 K and 323 K for a wide pressure range (1.0 to 70 MPa). The study was first conducted for the binary systems (H2O-CO2; H2O-CH4 and H2O[sbnd]H2) and then followed by the ternary systems (CO2-CH4-H2O and H2-CH4-H2O). The γ results were also validated with previous studies by comparing them to experimental and simulation data. The findings of this study indicated that γ data of binary and ternary systems decreased with increasing pressure and temperature. However, at high pressure (above 50 MPa), the γ data at 300 K and 323 K showed a plateau or changed very slightly, apparently not depending significantly on temperature. Furthermore, at a fixed pressure, determined γ values for the ternary system (H2-CH4-H2O) are constantly larger than for the CH4-H2O and CO2-CH4-H2O systems. The results provide extending or new γ data in simulation for the binary and ternary systems and contribute to evaluating the stability and long-term viability of various key Carbon Capture and Storage (CCS) and Underground Hydrocarbon Storage (UHS) related processes in support of the large-scale implementation of a hydrogen economy

    Understanding Gas and Energy Storage in Geological Formations with Molecular Simulations

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    Methane (CH4), the cleanest burning fossil fuel, has the potential to solve the energy crisis owing to the growing population and geopolitical tensions. Whilst highly calorific, realising its potential requires efficient storage solutions, which are safe and less energy-intensive during production and transportation. On the other hand, carbon dioxide (CO2), the by-product of human activities, exacerbates global heating driving climate change. CH4 is abundant in natural systems, in the form of gas hydrate and trapped gas within geological formations. The primary aim of this project was to learn how Nature could store such a large quantity of CH4 and how we can potentially extract and replace the in-place CH4 with atmospheric CO2, thereby reducing greenhouse gas emissions. We studied this question by applying molecular dynamics (MD) and Monte Carlo (MC) simulation techniques. Such techniques allow us to understand the behaviour of confined fluids, i.e., within the micropores of silica and kerogen matrices. Our simulations showed that CH4 hydrate in confinement could form under milder conditions than required, deviating from the typical methane-water phase diagram, complementing experimental observations. This research can contribute to artificial gas hydrate production via porous materials for gas storage. Besides that, the creation of 3D kerogen models via simulated annealing has enabled us to understand how maturity level affects the structural heterogeneity of the matrices and, ultimately CH4 diffusion. Immature and overmature kerogen types were identified to having fast CH4 diffusion. Subsequently, our proof-of-concept study demonstrated the feasibility of recovering CH4 via supercritical CO2 injection into kerogens. Insights from our study also explained why full recovery of CH4 is impossible. A pseudo-second-order rate law can predict the kinetics of such a process and the replacement quantity. A higher CO2 input required than the CH4 recovered highlights the possibility of achieving a net-zero future via geological CO2 sequestration
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