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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Analytical Pyrolysis and Microextraction Methods to Characterize Oil and Biochar from Thermal and Catalytic Cracking of Biomass

Conti, Roberto <1986> January 1900 (has links)
In this dissertation thermal and catalytic pyrolysis of protein-rich biomass was investigated. The study was focused on the liquid and solid products. This thesis was aimed to gather chemical information on the thermal behavior of proteinaceous substrates in the presence of zeolite and compare with lignocellulosic biomass. Furthermore, the thesis was focused on the development of reliable analytical methods by means of Py-GC-MS in order to predicting bio-oil composition and to investigating biochar structure and its correlation with thermal stability. In addition a sampling procedure for the direct analysis of pyrolysis vapours based on absorption onto a microfiber (SPME) was developed. Py-GC-MS was applied as screening method to study the effect of different catalysts (H-ZSM5, MCM-41) and biomass-catalyst weight ratio on aromatic hydrocarbons production. The obtained results demonstrated that Py-GC-MS enable the selection of pyrolysis conditions. H-ZSM5 confirmed to be the catalyst with the best performance in terms of hydrocarbon production. In addition, the chemical composition observed by Py-GC-MS significantly reflects that obtained on bench scale. However, some difference has been found. Indeed, formation of high molecular weight PAHs have been observed only on bench scale and nitrogen-containing compounds and oxygenated compounds exhibited some difference related to condensation step. Problems during condensation step led to using SPME as at-line monitoring technique during the process capable of hot gas phase analysis. Strong similarity between GC-MS analysis of hot vapours and bio-oil from condensation traps were found. Finally, Py-GC-MS was applied to the chemical characterization of biochars obtained under different pyrolysis conditions or from different feedstock. Py-GC-MS can provide molecular indices useful to gather information on biochar thermal stability and to predicting the biochar carbonization degree. Furthermore, the molecular pattern resulting from Py-GC-MS could be utilized to infer information on the nature of the initial substrate and differentiate biochars.
52

Coupling Reactions Between Aromatic Carbon - and Nitrogen - Nucleophiles and Electrophiles: Reaction Intermediates, Products and their Properties

Cino, Silvia <1985> January 1900 (has links)
During my PhD I was involved in many studies concerning the nucleophilic (SNAr) and electrophilic (SEAr) aromatic substitution reactions. My research activity was focused on the study of different electrophile/nucleophile combinations between strongly activated species, with the purpose to investigate on their reactivity, to detect new intermediates of the aromatic substitution reaction and to obtain new higly conjugated structures bearing contemporaneously electron donor and acceptor moieties on the same unit for application in different fields. Different reactions between both neutral or charged electrophilic and nucleophilic species were performed and from their combinations new products for applications in different fields (e.g. medicine, biology and materials) were obtained and new intermediates of the aromatic substitution reactions [e.g. Wheland (W), Meisenheimer (M), and even Wheland-Meisenheimer (WM)], were detected and characterized, mainly using NMR spectroscopic techniques. In particular the involved nucleophilic species were: tri- and diaminobenzene derivatives, trihydroxybenzene, trimethoxybenzene, anisole derivatives and aminothiazole derivatives; whereas the selected electrophilic species were: aryldiazonium ions, benzofuroxan and benzofurazan derivatives, thiophene derivatives and benzhydrylium ions. Furthermore, the last year of my PhD course, I spent a period in the Department of Chemistry, Ludwig-Maximilians-University of Munich, in collaboration with Prof. Herbert Mayr’s group, with the aim to investigate on the nucleophilic reactivities of di- and triaminobenzene derivatives performing their combination with different reference electrophiles, selected from the Mayr’s reactivity scales.
53

Sviluppo ambientalmente sostenibile di processi chimici e metodi sintetici innovativi focalizzati alla sintesi di nuove librerie molecolari / Environmentally Sustainable Design of Innovative Chemical Processes and Synthetic Methods Focused on the Synthesis of Novel Molecular Libraries

Armenise, Nicola <1985> January 1900 (has links)
Questa tesi è mirata ad essere un lavoro che racchiude alcuni dei vari aspetti rilevanti che collegano la Green Chemistry alla sostenibilità ambientale. La tesi riguarda lo sviluppo sostenibile attraverso capitoli che concorrono alla progettazione di processi chimici eco-compatibili innovativi e approcci verdi per ridurre al minimo e/o rimediare l'inquinamento ambientale. In questo contesto, il mio progetto di dottorato ha affrontato tre temi principali: 1. Progettazione, sintesi e caratterizzazione di nuove molecole di tensioattivo che impiegano materie prime rinnovabili, acido itaconico e ammine lipofile, come materiali di partenza; il Capitolo 2 descrive questo argomento. 2. Sviluppo di una procedura sostenibile finalizzata alla sintesi multicomponente a cascata di biarilcalconi in acqua pura o in condizioni di catalisi micellare; in quest'ultimo caso, uno dei tensioattivi precedentemente sintetizzati è stato ampiamente impiegato; il Capitolo 5 descrive questo argomento. Capitolo 3 e Capitolo 4 descrivono il contesto scientifico e le innovazioni più importanti che hanno aperto la strada a i risultati conseguiti durante il 2 ° anno del corso di dottorato; il primo è una panoramica sull'uso dell'acqua come solvente per reazioni organiche; il secondo è una panoramica sulle reazioni di cross-coupling e lo sfruttamento in questo contesto della catalisi micellare. 3. Progettazione, sintesi e impiego di ligandi di tipo fenantrolinico deuterati per l'ossidazione aerobica palladio catalizzata del metil-glucoside, consentendo un elevato miglioramento della prestazione in questa reazione impegnativa; il Capitolo 7 raccoglie i risultati ottenuti, mentre il capitolo 6 riassume i più importanti progressi ottenuti negli ultimi anni nelle ossidazioni aerobiche di alcoli palladio-catalizzate. / This thesis is intended to be a work that encompasses some of the various relevant aspects linking the Green Chemistry practice to environmental sustainability. The thesis covers sustainable development through chapters that contribute to the design of novel environmentally benign chemical processes and green approaches to minimize and/or remediate environmental pollution. In this context, my PhD project has faced three main topics: 1. Design, synthesis and characterization of new surfactant molecules employing renewable feedstocks, itaconic acid and fatty amines, as starting materials; Chapter 2 describes this topic. 2. Development of a sustainable procedure aimed to the multicomponent cascade synthesis of biaryl-based chalcones in pure water or under micellar catalysis conditions; in the latter case, one of the surfactants previously synthesized has been widely employed; Chapter 5 describes this topic. Chapter 3 and Chapter 4 describe the scientific context and the most important innovations that have paved the way to the results achieved during the 2nd year of PhD course; the former is an overview on the use of water as solvent for organic reactions; the latter is an overview on cross-coupling reactions and the exploitation in this context of micellar catalysis. 3. Design, synthesis and exploitation of deuterated phenanthroline-type ligands for the aerobic palladium-catalyzed oxidation of methyl glucoside, allowing a high performance improvement in this challenging reaction; Chapter 7 collects the obtained results, while Chapter 6 summarizes the most important advances obtained in the last years in the palladium-catalyzed aerobic oxidations of alcohols.
54

Cinchona alkaloids and BINOL derivatives as privileged catalysts or ligands in asymmetric synthesis

Paradisi, Enrico <1986> 15 April 2014 (has links)
During the last fifteen years organocatalysis emerged as a powerful tool for the enantioselective functionalization of the most different organic molecules. Both C-C and C-heteroatom bonds can be formed in an enantioselective fashion using many types of catalyst and the field is always growing. Many kind of chiral catalysts have emerged as privileged, but among them Proline, cinchona alkaloids, BINOL, and their derivatives showed to be particularly useful chiral scaffolds. This thesis, after a short presentation of many organocatalysts and activation modes, focuses mainly on cinchona alkaloid derived primary amines and BINOL derived chiral Brønsted acids, describing their properties and applications. Then, in the experimental part, these compounds are used for the catalysis of new transformations. The enantioselective Friedel-Crafts alkylation of cyclic enones with naphthols using cinchona alkaloid derived primary amines as catalysts is presented and discussed. The results of this work were very good and this resulted also in a publication. The same catalysts are then used to accomplish the enantioselective addition of indoles to cyclic enones. Many catalysts in combination with many acids as co-catalysts were tried and the reaction was fully studied. Selective N-alkylation was obtained in many cases, in combination with quite good to good enantioselectivities. Also other kind of catalysis were tried for this reaction, with interesting results. Another aza-Michael reaction between OH-free hydroxylamines and nitrostyrene using cinchona alkaloid derived thioureas is briefly discussed. Then our attention focused on Brønsted acid catalyzed transformations. With this regard, the Prins cyclization, a reaction never accomplished in an enantioselective fashion until now, is presented and developed. The results obtained are promising. In the last part of this thesis the work carried out abroad is presented. In Prof. Rueping laboratories, an enantioselective Nazarov cyclization using cooperative catalysis and the enantioselective desymmetrization of meso-hydrobenzoin catalyzed by Brønsted acid were studied.
55

Enantioselective Reactions Promoted by Organocatalytic Species From The Natural Chiral Pool

Gioia, Claudio <1984> 12 April 2012 (has links)
During the course of my Ph.D. in the laboratories directed by Prof. Alfredo Ricci at the Department of Organic Chemistry “A. Mangini” of the University of Bologna, I was involved in the study and the application of a number of organocatalytic systems, all coming from the natural chiral pool. The first part of this thesis will be devoted to new homogeneous organocatalytic reactions promoted by Cinchona alkaloid-based organocatalysts. Quinine based catalysts were found to be a very effective catalyst for Diels-Alder reactions involving 3-vinylindoles. Excellent results in terms of yields and enantioselectivities were achieved, outlining also a remarkable organocatalytic operational mode mimicking enzymatic catalysis. The same reaction with 2-vinylindoles showed a completely different behaviour resulting in an unusual resolution-type process. The asymmetric formal [3+2] cycloaddition with in situ generated N-carbamoyl nitrones using Cinchona-derived quaternary ammonium salts as versatile catalysts under phase transfer conditions, outlines another application in organocatalysis of this class of alkaloids. During the seven months stage in the Prof. Helma Wennemers’ group at the Department of Chemistry of the University of Basel (Switzerland) I have been involved in organocatalysis promoted by oligopeptides. My contribution regarded the 1,4-addition reaction of aldehydes to nitroolefins. In the work performed at the Department of Organic Chemistry “A. Mangini” of the University of Bologna, in collaboration with the ‘Institut Charles Gerhardt-Montpellier, of Montpellier (France) the possibility of performing for the first time heterogeneous organocatalysis by using a natural polysaccharide biopolymer as the source of chirality was disclosed. With chitosan, derived from deacetylation of chitin, a highly enantioselective heterogeneous organocatalytic aldol reaction could be performed. The use of an eco-friendly medium such as water, the recyclability of the catalytic specie and the renewable nature of the polysaccharide are assets of this new approach in organocatalysis and open interesting perspectives for the use of biopolymers.
56

Nuovi materiali da nucleosidi modificati

Lena, Stefano <1972> 28 May 2007 (has links)
No description available.
57

Nuovi processi catalitici di tipo acido-base a basso impatto ambientale

Ardizzi, Mattia <1979> 15 June 2007 (has links)
No description available.
58

Catalizzatori altamente versatili per reazioni regio e stereoselettive in fase omogenea ed eterogenea

Tommasi, Simona <1980> 16 May 2007 (has links)
No description available.
59

Studio di rivestimenti antiriflesso da sol-gel dip-coating per impianti solari termodinamici

Bezzi, Federica <1978> 15 June 2007 (has links)
Negli impianti utilizzati per la produzione di energia elettrica che sfruttano l'energia solare, quali la tecnologia solare a concentrazione (Solare Termodinamico) sviluppata da ENEA, per minimizzare le dispersioni di calore è necessaria una elevata selettività spettrale. Per ottimizzare l'efficienza dell'impianto è quindi necessario lo sviluppo di materiali innovativi, in grado di minimizzare la quantità di energia dispersa per riflessione. In questo studio, per incrementare la trasmittanza solare dei componenti in vetro presenti nei tubi ricevitori dell'impianto, sono state utilizzate tipologie diverse di rivestimenti antiriflesso (multistrato e a singolo strato poroso). I rivestimenti sono stati ottenuti mediante via umida, con tecnica di sol-gel dip-coating. I sol coprenti sono stati preparati da alcossidi o sali metallici precursori degli ossidi che costituiscono il rivestimento. Sono state approfondite sia la fase di sintesi dei sol coprenti, sia la fase di deposizione sul substrato, che ha richiesto la progettazione e realizzazione di una apparecchiatura prototipale, ossia di un dip-coater in grado di garantire un accurato controllo della velocità di emersione e dell'ambiente di deposizione (temperatura e umidità). Il materiale multistrato applicato su vetro non ha migliorato la trasmittanza del substrato nell'intervallo di lunghezze d'onda dello spettro solare, pur presentando buone caratteristiche antiriflesso nell'intervallo dell'UV-Vis. Al contrario, l'ottimizzazione del rivestimento a base di silice porosa, ha portato all'ottenimento di indici di rifrazione molto bassi (1.15 to 1.18) e ad un incremento della trasmittanza solare dal 91.5% al 96.8%, efficienza superiore agli attuali rivestimenti disponibili in commercio.
60

Fabbricazione non convenzionale di nanostrutture a base di carbonio per biosensori

Facchini, Massimo <1978> 14 May 2007 (has links)
No description available.

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