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In this research, two-stage hydrotreating of bitumen-derived light gas oil (LGO) from Athabasca oil sands was studied. The objective was to catalytically upgrade the LGO by reducing the aromatics content and enhancing the cetane content via inter-stage removal of hydrogen sulfide. The impact of hydrogen sulfide inhibition on aromatics hydrogenation (HDA), hydrodenitrogenation (HDN) and hydrodesulfirization (HDS) activities was investigated. Experiments for this study were carried out in a trickle-bed reactor loaded with commercial NiMo/Al2O3 and lab-prepared NiW/Al2O3 in the stage I and stage II reactors, respectively. Temperature was varied from 350 to 390 oC at the optimum LHSV and pressure conditions of 0.6 h-1 and 11.0 MPa, respectively. The results from two-stage process showed significant improvement in HDA, cetane rating and HDS activities compared to the single-stage process after the inter-stage removal of hydrogen sulfide. Hence, the presence of hydrogen sulfide in the reaction retarded both the HDA and HDS processes in the single-stage operation. Negligible hydrogen sulfide inhibition was however, observed in the HDN process. <p>Prior to the two-stage hydrotreating study, single-stage hydrotreating reactions were carried out over commercial NiMo/Al2O3 catalyst to determine the optimum operating conditions for maximizing hydrogenation of aromatics. A statistical approach via the Analysis of Variance (ANOVA) technique was used to develop regression models for predicting the conversion of aromatics, sulfur and nitrogen in the LGO feed. Experiments were performed at the following operating conditions: temperature (340-390 oC); pressure (6.9-12.4 MPa) and liquid hourly space velocity, LHSV (0.5-2.0 h-1). Hydrogen-to-oil ratio was maintained constant at 550 ml/ml. The results showed that the two-level interaction between temperature and pressure was the only significant interaction parameter affecting HDA while interaction between temperature and LHSV was the most important parameter affecting both HDS and HDN activities. A maximum 63 % HDA was obtained at 379 oC, 11.0 MPa and 0.6 h-1. Experiments with NiW/Al2O3 were also performed in a single-stage reactor with LGO blend feedstock by varying temperature from 340-390 oC at the optimum pressure and space velocity of 11.0 MPa and 0.6 h-1, respectively. The following order of ease of hydrogenation was observed: poly- > di- >> monoaromatics. The order of ease of hydrogenation in other LGO feedstocks (atmospheric light gas oil, ALGO; hydrocrack light gas oil, HLGO; and vacuum light gas oil, VLGO) was studied and found to follow the order: VLGO > ALHO > HLGO. Studies on mild hydrocracking (MHC) in the gas oil feedstocks showed a net increase in gasoline with a corresponding decrease in diesel with increasing temperature. <p>Both the single and two-stage HDA and HDS kinetics were modeled using Langmuir-Hinshelwood rate equations. These models predicted the experimental data with reasonable accuracy. The degree of conversion of the gas oil fractions in ALGO, HLGO and VLGO via mild hydrocracking was best described by a pseudo-first order kinetic model based on a parallel conversion scheme.

In this research, two-stage hydrotreating of bitumen-derived light gas oil (LGO) from Athabasca oil sands was studied. The objective was to catalytically upgrade the LGO by reducing the aromatics content and enhancing the cetane content via inter-stage removal of hydrogen sulfide. The impact of hydrogen sulfide inhibition on aromatics hydrogenation (HDA), hydrodenitrogenation (HDN) and hydrodesulfirization (HDS) activities was investigated. Experiments for this study were carried out in a trickle-bed reactor loaded with commercial NiMo/Al2O3 and lab-prepared NiW/Al2O3 in the stage I and stage II reactors, respectively. Temperature was varied from 350 to 390 oC at the optimum LHSV and pressure conditions of 0.6 h-1 and 11.0 MPa, respectively. The results from two-stage process showed significant improvement in HDA, cetane rating and HDS activities compared to the single-stage process after the inter-stage removal of hydrogen sulfide. Hence, the presence of hydrogen sulfide in the reaction retarded both the HDA and HDS processes in the single-stage operation. Negligible hydrogen sulfide inhibition was however, observed in the HDN process. <p>Prior to the two-stage hydrotreating study, single-stage hydrotreating reactions were carried out over commercial NiMo/Al2O3 catalyst to determine the optimum operating conditions for maximizing hydrogenation of aromatics. A statistical approach via the Analysis of Variance (ANOVA) technique was used to develop regression models for predicting the conversion of aromatics, sulfur and nitrogen in the LGO feed. Experiments were performed at the following operating conditions: temperature (340-390 oC); pressure (6.9-12.4 MPa) and liquid hourly space velocity, LHSV (0.5-2.0 h-1). Hydrogen-to-oil ratio was maintained constant at 550 ml/ml. The results showed that the two-level interaction between temperature and pressure was the only significant interaction parameter affecting HDA while interaction between temperature and LHSV was the most important parameter affecting both HDS and HDN activities. A maximum 63 % HDA was obtained at 379 oC, 11.0 MPa and 0.6 h-1. Experiments with NiW/Al2O3 were also performed in a single-stage reactor with LGO blend feedstock by varying temperature from 340-390 oC at the optimum pressure and space velocity of 11.0 MPa and 0.6 h-1, respectively. The following order of ease of hydrogenation was observed: poly- > di- >> monoaromatics. The order of ease of hydrogenation in other LGO feedstocks (atmospheric light gas oil, ALGO; hydrocrack light gas oil, HLGO; and vacuum light gas oil, VLGO) was studied and found to follow the order: VLGO > ALHO > HLGO. Studies on mild hydrocracking (MHC) in the gas oil feedstocks showed a net increase in gasoline with a corresponding decrease in diesel with increasing temperature. <p>Both the single and two-stage HDA and HDS kinetics were modeled using Langmuir-Hinshelwood rate equations. These models predicted the experimental data with reasonable accuracy. The degree of conversion of the gas oil fractions in ALGO, HLGO and VLGO via mild hydrocracking was best described by a pseudo-first order kinetic model based on a parallel conversion scheme.

Ένα από τα πιο γνωστά και κοινά αρωματικά φυτά της Ελληνικής χλωρίδας είναι η ρίγανη (Origanum vulgare ssp. hirtum), η οποία αποτελεί μέρος της «μεσογειακής» δίαιτας και κύριο συστατικό της Ελληνικής διατροφής, ιδιαίτερα της Κρητικής, για την οποία υπάρχουν εργασίες που αποδεικνύουν ότι προστατεύει την ανθρώπινη υγεία από καρδιακές παθήσεις και πολλές μορφές καρκίνου. Εξεταζόμενη από άποψη, περιβαλλοντική και οικονομική παρουσιάζει ιδιαίτερο ενδιαφέρον στη χώρα μας. Η ρίγανη έχει τη μεγαλύτερη οικονομική αξία από τα υπόλοιπα αρωματικά και φαρμακευτικά φυτά που παράγονται στην Ελλάδα, γιατί οι αντιοξειδωτικές της ιδιότητες σε συνδυασμό με την αντιβακτηριακή και αντιμυκητιακή της δράση, την καθιστούν περιζήτητη στις βιομηχανίες τροφίμων και φαρμάκων. Τα φαρμακευτικά και αρωματικά χαρακτηριστικά της τα οφείλει στην περιεκτικότητα της σε αιθέριο έλαιο και στη χημική του σύσταση. Για τους λόγους αυτούς η αύξηση της παραγωγής της και η διατήρηση ή επαύξηση των ποιοτικών χαρακτηριστικών της παρουσιάζει εξαιρετικό ενδιαφέρον. Σκοπός της παρούσας εργασίας ήταν ο περιορισμός της ποιοτικής υποβάθμισης που υφίσταται η ρίγανη λόγω του μικροβιακού φορτίου που αναπτύσσει, κυρίως κατά το στάδιο της συλλογής ή αποθήκευσής της. Για να επιτευχθεί ο σκοπός αυτός, εξετάστηκε ως τρόπος απολύμανσης της ρίγανης κατά τη διάρκεια αποθήκευσής της η χρήση αερίου όζοντος. Η επιλογή του όζοντος βασίστηκε στην άριστη απολυμαντική δράση που εμφανίζει σε μικροοργανισμούς και έντομα ακόμα και σε πολύ χαμηλές συγκεντρώσεις, καθώς επίσης και σε μία σειρά πλεονεκτημάτων του, με κυριότερα την ταχύτατη δράση του σε συνδυασμό με το υψηλό δυναμικό οξειδοαναγωγής που διαθέτει, καθιστώντας το ισχυρό οξειδωτικό παράγοντα. Η μελέτη της απολυμαντικής δράσης του όζοντος πραγματοποιήθηκε σε πραγματικά δείγματα εμπορικού προϊόντος, το οποίο βρέθηκε επιμολυσμένο με δύο μικροοργανισμούς, το εντεροβακτήριο (Enterobacter aerogenes) και τον επιδερμικό σταφυλόκοκκο. Στα πλαίσια της εργασίας αυτής αναπτύχθηκε διάταξη για οζονισμό ρίγανης, αλλά και άλλων αρωματικών και μη φυτικών υλικών, με προοπτικές εφαρμογής των αποτελεσμάτων της σε μεγαλύτερη κλίμακα (στη βιομηχανία), ενώ παράλληλα εξετάστηκε η ποιοτική και ποσοτική σύσταση του αιθέριου ελαίου της ρίγανης σε σχέση με την επίδραση του όζοντος. Με βάση τα αποτελέσματα που προέκυψαν, μπορεί να εξαχθεί το γενικό συμπέρασμα ότι η προτεινόμενη διεργασία (χρήση όζοντος) είναι εξαιρετικά αποτελεσματική στην απολύμανση της ρίγανης, εκμηδενίζοντας το μικροβιακό φορτίο αυτής, χωρίς να επιδρά τόσο στα ποσοτικά όσο και στα ποιοτικά χαρακτηριστικά του τελικού εμπορικού προϊόντος. Η διεργασία αυτή μπορεί να επεκταθεί, κατά την κρίση μας, και σε άλλα αρωματικά φυτά, και όχι μόνο, συνεισφέροντας στην επίλυση ενός σημαντικού προβλήματος της αντίστοιχης βιομηχανίας διασφαλίζοντας υψηλή αξία στο τελικό εμπορικό προϊόν. / One of the most known and common medicinal plants of Greek flora is origan (Origanum vulgare ssp. hirtum), which makes part of the so-called “Mediterranean” diet and is a major component of the Greek nutrition, especially of that Cretan, for which there are papers demonstrating that protects human health from heart diseases and many forms of cancer. Considered in environmental and economic terms, shows a particular interest in our country. Origano has the highest economic value from the other aromatic and medicinal plants produced in Greece, because the antioxidant properties in combination with its antibacterial and antifungal action, making it much sought after in the food and pharmaceutical industries. Its medicinal and aromatic characteristics are due to its essential oil content and chemical composition. For these reasons, its increased production and maintenance or enhancement of its quality characteristics shows an exceptional interest. The purpose of this study was to limit the qualitative deterioration “suffered” because of origano microbial load that develops, mainly during the collection or storage. To achieve this, the use of ozone gas, as a method of origano disinfection during storage, has been examined. The selection was based on ozone disinfecting excellent action showing in microorganisms and insects even at very low concentrations, as well as a series of advantages, mainly the most rapid action combined with its high redox potential available, making it a powerful oxidizing agent. The study of ozone disinfectant action was conducted on commercial product actual samples, which were found contaminated with two microorganisms, the enterobacterium (Enterobacter aerogenes) and epidermal staphylococcus. As part of this work, a device was developed for origan ozonization, and other aromatic and non-plant materials, with potential application results in a larger scale (manufacturing), while also the qualitative and quantitative composition of the origan essential oil with regards to ozone effect has been examined. Based on the results obtained, it can be concluded that the proposed process (use of ozone) is extremely effective in decontamination of origan, by completely reducing its microbial load, without affecting both the quantitative and the qualitative characteristics of the finished commercial product. This process can be extended, at our discretion, to other herbs also, and beyond, contributing to solving an important problem of the respective industry ensuring a high value to the finished commercial product.

The common discotic mesogen molecules are known to have a flat structure, comprising a rigid core, e.g., polynuclear aromatic structure, and a ring of four to nine flexible aliphatic side chains. We take the electron deficient heterocyclic hexaazatriphenylene (HAT) as our central core and readily synthesized by the condensation of hexaketocyclohexane with the respective 1,2-bis-alkoxy-4,5-diaminobenzene. The new molecules with electron deficient discotic liquid crystal properties are successfully.

The discovery of MCM-41 materials have attracted substantial research attention due to the remarkable features of these materials including a narrow pore size distribution, high surface area, high pore volume, and high thermal and hydrothermal stability, as well as, parallel hexagonal arrangement of uniform cylindrical pores without pore channel intersection. These well-defined structural characteristics make them ideal media to study the adsorption, catalysis, ion exchange, and separation. MCM-41 sample used in this study was synthesized in (Chemical Engineering Department, Gazi University). The MCM-41 was synthesized by using sodium silicate (0.0705 mol, 27% Silica) as a source of silica and surfactant cetyltrimethylammoniumbromides (CTMABr) (0.036 mol) as template. A characteristic feature of this direct hydothermal synthesis was relatively long synthesis time (96 hour at 120&deg / C). MCM-41 was characterized by using XRD, and nitrogen physisorption analysis techniques. The characteristic peak in the low-angle region corresponding to 2&amp / #952 / = 2.406&deg / was obtained for MCM-41 sample indicating high structural ordering of the MCM-41sample. The BET, surface area was found as (492.2 m /g), with an average pore diameter (25 &Aring / ). In this study the sorption equilibrium of C aromatics (p-xylene, m-xylene, o-xylene, and ethylbenzene ) on MCM-41 at different temperatures (30&deg / C, 50&deg / C, 65&deg / C, 80&deg / C) was investigated by using an automated gravimetric electrobalance system. It was found that the amounts of each sorbate (p-xylene, m-xylene, o-xylene, and ethylbenzene) adsorbed at a given relative pressure on MCM-41 decreased when the temperature of the adsorption isotherms increases. The adsorption isotherms were type V, according to IUPAC isotherm classification due to the mesoporous nature of the MCM-41 sample. The hysteresis are associated with condensation-evaporation within a narrow distribution of mesopores with each adsorption isotherms. It was shown that as the temperature for the adsorption isotherms increases the size of hysteresis decreases for each sorbate. The volume of sorbates (V ) were obtained from the mass uptake at maximum relative pressure by taking the normal liquid density at the adsorption temperature for all sorbates. These values are significantly lower than that obtained from low-temperature nitrogen isotherm. The reason of this difference is that the density of the adsorbed phase is unlikely to be exactly the same as that of the liquid adsorptive and curvature of some isotherms at high relative pressure leads to uncertainty in the location of the upper limit for pore filling.

UV radiation can cause harmful effects to human skin, including premature skin ageing and skin cancer. Historically, sunscreens were developed to filter out UVB (290 nm-320 nm), but now the importance of UVA (320 nm-400 nm) sunscreens is realised. The most common UVA sunscreens are based on dibenzoylmethane (1,3-diphenyl propan-l,3-dione, DBM), of which the most common is Parsol 1789 (4'- methoxy 4'-tertiarybutyl DBM). The photochemistry of these materials has, however, been poorly understood. In this work the photophysics and photochemistry of DBM, Parsol 1789, Parsol DAM and ditertiarybutyl DBM have been studied, along with the respective 0-methylated and C-methylated compounds of DBM and Parsol 1789.DBMs exist primarily as an intra-molecularly bonded enol, which absorbs strongly at λ≈340 nm due to a π,π* transition. The absorption spectra of DBMs also exhibit a smaller peak at λ≈250 nm, due to an n,π* transition of the diketone content. At low temperature the main absorption band of DBMs shifts to longer wavelengths and vibrational structure can be observed. The enol form of DBMs fluorescence at low temperature, (v(_0)’→v’’(_0) at λ≈385 nm), and phosphorescence can be observed from both the diketone (λ(_em)≈495 nm,) and enol forms (λ(_em)≈425 nm). Thus the triplet energies of the diketones and enols of the DBMs studied have been measured. 0-methylated DBMs do not possess an intra-molecular H-bond, and the π,π* absorption band falls to lower wavelengths than for chelated DBMs. C-methylated DBMs exist as a diketone structure, and display photophysics typical of an aromatic ketone. It has been suggested that the main process on irradiation of DBM is the formation of a short-lived non-chelated enol, however no direct evidence as to the structure of this species is reported in the literature. Formation of the diketone form of DBM on prolonged irradiation in acetonitrile solution has also been reported, and in this work the quantum yield of this process has been measured; ɸ≈0.01 ± 0.004. In this work, direct (low temperature) IR spectroscopic evidence is presented to prove that the short-lived species produced on irradiation is indeed a non-chelated enol. The infra-red studies also suggest that the non-chelated enol form of DBM form complexes with polar solvents, as has been proposed in the literature. Quantum yields of non-chelated enol formation in cyclohexane at room temperature have been measured to be approximately ɸ=0.5 + 0.07. This work indicates that the rate of transient decay is enhanced by the interaction of the transient molecules with chelated enol molecules or other transient molecules. IR studies of low temperature transient formation confirm the interaction of transient molecules by the observation of inter-molecular hydrogen-bonding. By comparison with the E and Z isomers of 0-methylated DBM it is suggested that at low temperature DBM initially forms a Z-cis non-hydrogen bonded enol, which then converts to an E-trans non-hydrogen bonded enol with further irradiation. The kinetics and the temperature variation of the enol recovery support the theory that there is more than one species formed. The photochemistry of DBM in emulsions has also been studied in this work. It has been shown that the photochemistry occurring on irradiation is similar to that observed in solutions. This indicates that simple solutions are a good model for actual sunscreen formulations. Singlet oxygen is a highly reactive species capable of causing serious biological damage, however this work shows that DBM sunscreens generate singlet oxygen by photosensitisation, with quantum yields ɸ∆≈0.005-0.01. It has also been shown that the lifetime of the excited state of DBM involved in singlet oxygen production is very short, approximately τ <1 µs.

Orientador: Lucia Regina Durrant / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T18:02:39Z (GMT). No. of bitstreams: 1 CuadrosOrellana_Sara_D.pdf: 8786475 bytes, checksum: 37002d082a1fea19d88bc66b7dced99e (MD5) Previous issue date: 2003 / Resumo: O metabolismo de compostos aromáticos depende de fatores físico-químicos como temperatura, pH e salinidade, e é bem conhecido e caracterizado em microrganismos mesófilos e em condições ambientais moderadas. No entanto, pouco se conhece sobre o metabolismo desses compostos em ambientes hipersalinos. este trabalho, cinco ambientes hipersalinos foram analisados quanto à presença de arqueas halofílicas capazes de metabolizar compostos aromáticos: Salar de Uyuni (Bolívia), salinas de Cahuil (Chile), salinas de Cabo Rojo (Porto Rico), sabkhas da região do Golfo Pérsico (Arábia Saudita) e Mar Morto (Israel e Jordânia). A estratégia empregada para o enriquecimento e isolamento de arqueas halofílicas capazes de crescer em presença de compostos aromáticos foi bem sucedida. Foram isoladas 12 linhagens capazes de crescer em presença de 1 ,2--benzoantraceno (2 mM) e 44 linhagens capazes de crescer em presença de ácido p-hidroxibenzóico (10 mM) como única fonte de carbono e energia. O isolado MM 17, proveniente de uma amostra de água do Mar Morto, apresentou o melhor resultado de crescimento e foi capaz de degradar completamente os ácidos benzóico (10 mM) e p-hidroxibenzóico (10 mM) após 200 h de cultivo. As análises bioquímica e genética dos isolados, juntamente com a análise dos perfis de lipídeos polares, indicaram que as linhagens estudadas pertencem a pelo menos dois gêneros: Haloferax e Halobacterium. Foi determinada a secreção de uma proteína de alto peso molecular por Haloferax volcanii em resposta à presença de 2 mM 1 ,2-benzoantraceno no meio de cultivo. Com o objetivo de estudar o mecanismo de secreção protéica em haloarqueas, o qual não é completamente entendido_ foram realizadas a clonagem molecular dos genes secD e secY de Haloferax volcanii, a expressão heteróloga em Escherichia coli e a purificação dos produtos gênicos, além de uma tentativa preliminar de obtenção de anticorpos policlonais através da imunização de coelhos / Abstract: The metabolism of aromatic compounds depends on physical-chemical factors such as temperature, pH and salinity, and is well known and characterized in mesophilic microorganisms under mild environmental conditions. Little is known, however, about the metabolism of these compounds in highly saline environments. Here, five hypersaline sites were tested for the presence of halophilic archaea able to metabolize aromatic compounds: the Uyuni Salt Marsh (Bolivia), the crystallizer ponds in Cahuil (Chile), the crystallizer ponds in Cabo Rojo (Puerto Rico), the sabkhas in the Persian Gulf (Saudi Arabia) and the Dead Sea (Israel and Jordan). The strategy used for the enrichment and isolation of halophilic archaea able to grow in aromatic compounds was successful. Twelve strains able to grow in 1,2-benzoantracene (2 mM) and 44 strains able to grow in p-hydroxybenzoic acid (10 mM) as the sole carbon and energy source were isolated. Strain MM17, isolated from a Dead Sea water sample, showed the best growth and was able to degrade benzoic (10 mM) and p-hydroxybenzoic (10 mM) acids afier 200 h of cultivation. Biochemical and genetic analyses of the isolates, together with the analysis of polar lipid profiles, indicate that the strains belong to at least two different genera: Haloferax and Halobacterium. The secretion of a high molecular weight protein by Haloferax volcanii following cultivation in 2 mM 1,2-benzoantracene was observed. To study the mechanism of protein secretion in halophilic archaea, a process that is not completely understood, preliminary studies were conducted, which included cloning of secO and secY genes of Haloferax volcanii, their heterologous expression in Escherichia coli and the purification of the gene products. In addition, a preliminary attempt to obtain polyclonal antibodies through rabbit immunization was made / Doutorado / Doutor em Ciência de Alimentos