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Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 183-196).

In this research, oxidative dehydrogenation of ethane to ethylene was studied over Cr-O and Cr-V-O mixed oxide catalysts through steady-state and dynamic experiments. The catalysts were prepared by the complexation method. By XRD, presence of Cr2O3 phase in Cr-O / and the small Cr2O3 and V2O4 phases of Cr-V-O were revealed. In H2-TPR, both catalysts showed reduction behaviour. From XPS the likely presence of Cr+6 on fresh Cr-O was found. On Cr-V-O, the possible reduction of V+5 and Cr+6 forms of the fresh sample to V+4, V+3 and Cr+3 states by TPR was discovered through XPS. With an O2/C2H6 feed ratio of 0.17, Cr-O exhibited the highest total conversion value of about 0.20 at 447&deg / C with an ethylene selectivity of 0.82. Maximum ethylene selectivity with Cr-O was obtained as 0.91 at 250&deg / C. An ethylene selectivity of 0.93 was reached with the Cr-V-O at 400&deg / C. In the experiments performed by using CO2 as the mild oxidant, a yield value of 0.15 was achieved at 449&deg / C on Cr-O catalyst. In dynamic experiments performed over Cr-O, with C2H6 pulses injected into O2-He flow, the possible occurrence of two reaction sites for the formation of CO2 and H2O was detected. By Gaussian fits to H2O curves, the presence of at least three production ways was thought to be probable. Different from Cr-O, no CO2 formation was observed on Cr-V-O during pulsing C2H6 to O2-He flow. In the runs performed by O2 pulses into C2H6-He flow over Cr-V-O, formation of CO rather than C2H4 was favored.

>Magister Scientiae - MSc / Palladium can be used as an anodic catalyst for the alkaline direct alcohol fuel cells (ADAFCs). Palladium has displayed high tolerance towards carbon monoxide (CO) poisoning and high catalytic activity for alcohol oxidation reaction in alkaline medium. Palladium-based catalysts have arisen as an alternative to performing alcohol oxidation reaction, especially when combined with other transition metals and multi walled carbon nanotubes (MWCNT) as a support, which induces changes in the palladium electronic structure, and thus, increasing its activity. This research is focused on the development of palladium catalysts incorporated with nickel and tin (transitional metals) on multi walled carbon nanotubes for alkaline direct glycerol fuel cells.

This thesis describes the preparation and characterization of manganese oxide catalysts and their application in the oxidation of acetone, a typical volatile organic compound (VOC), and ozone decomposition. This topic is of great value because of environmental concerns of the elimination of the harmful VOCs and ozone. Manganese oxide was chosen because it is a well-known complete oxidation catalyst for VOCs and also an active catalyst for ozone decomposition. Two cases of studies were carried out in this work. The first study involved the oxidation of acetone using ozone on silica- and alumina-supported manganese oxide catalysts deposited on aluminum oxide foam substrates. The characteristics of the catalysts were determined through various techniques, including x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), and oxygen chemisorption. The use of these techniques allowed better understanding of the nature of the catalysts. Activity tests were carried out in the acetone oxidation reaction and it was found that the usage of ozone substantially reduced the oxidation temperature. Steady-state in situ Raman spectroscopy was also carried out to better understand the mechanism of the acetone oxidation reaction using ozone. The second study involved an investigation of structural and electronic properties of manganese centers of the MnOx/SiO2 and MnOx/Al2O3 catalysts during the ozone decomposition reaction using in situ x-ray absorption spectroscopy (XAS). The number of surface active sites was again determined through TPR and oxygen chemisorption measurements. The performance of the catalysts with different loadings and supports were also compared. / Master of Science

This dissertation addresses the surging global demand for sustainable energy alternatives and biobased products, driven by population growth and the imperative to shift away from finite fossil fuels amidst climate change. The research centers on the catalytic upgrading of rice straw bio-oil, employing bimetallic magnetic nano-catalysts on rice straw-derived biochar to align with the imperative for environmentally conscious energy solutions. In the initial phase, the study systematically explores upgrading processes using varied alcohols, specifically ethanol, and butanol, under mild conditions to enhance bio-oil quality. The detailed evaluation of catalyst composition reveals a notable reduction in oxygen content, coupled with a significant increase in energy density and calorific value. The upgraded bio-oil not only exhibits heightened stability but also undergoes a substantial shift towards a more desirable hydrocarbon-rich composition. The second part of the research optimizes upgrading process parameters catalyst concentration, reaction holding time, and reaction temperature using Response Surface Methodology based on the Box-Behnken experimental design. This optimization refines the catalytic upgrading process, enhancing its efficiency and reliability. Beyond catalytic efficacy, the study considers the magnetic recovery of catalysts for potential reuse, emphasizing sustainability on a broader scale. Set against the backdrop of global energy challenges, this research significantly contributes to advancing the understanding of bimetallic magnetic nano-catalysts. The dissertation unfolds in two parts, with the first segment focusing on Catalytic Upgrading of Rice Straw Bio-Oil via Esterification in Supercritical Ethanol Over Bimetallic Catalyst (CuO-Fe3O4/AcB), involving the variation of Cu and Fe metals on Rice Straw Biochar without hydrogen gas. The exploration continues with the Upgrading of Rice Straw Bio-Oil in Butanol and hydrogen gas Over a Sustainable Magnetic Bimetallic Nano-Catalyst (ZrO2-Fe3O4/AcB). The integrated analytical approach, utilizing XRD, SEM, FT-IR for synthesized catalysts, alongside GC-MS and the Bomb Calorimeter for bio-oil samples, establishes a nuanced understanding crucial for optimizing catalytic performance in sustainable biofuel production.

Abstract The aim of the thesis is to expand the knowledge of the catalytic properties of platinum-loaded zeolite catalysts in the reduction of NOx by hydrocarbons. The work is divided into three parts. First the recent literature of zeolite catalysts has been introduced, secondly the adsorption capacity, activity, and acidity of the catalysts have been studied by TPD and IR techniques, and thirdly the derived reaction mechanisms based on the obtained data are presented. Parent and 1 wt-% Pt-loaded ZSM-5, Beta, Y, and Ferrierite zeolite catalysts have been studied in the C3H6-assisted reduction of NO. The Pd/Al2O3-based catalyst was used as a reference material for the reaction mechanistic studies. Several experimental techniques (in situ DRIFT, activity measurements, CO chemisorption, N2 physisorption, TPD, and TEM) have been used for the characterisation of the catalysts properties. The IR technique was used as the main technique for the determination of activities, surface species, and the acidic properties of the zeolite-based catalysts. The activity studies carried out by the gaseous FTIR technique provide information on the desired reaction products as well as the undesired by-products. The detection and identification of the surface species as well as the reaction intermediates formed were done by the DRIFT method. The activity experiments indicate the effectiveness of the Pt-loaded zeolite catalysts. The reduction of NO was found to decrease in the order: Pt/Beta > Pt/Y > Pt/Ferrierite > Pt/ZSM-5 in the conditions with excess O2. Platinum can be concluded to have an effect on O2 and NO dissociation. Oxidation reactions of NO to NO2 and propene to CO2 were observed to be more intense over the platinum-loaded zeolites than over the parent zeolites. In this work the reaction mechanisms for the C3H6-SCR of NO were derived over the Pt-loaded zeolite as well as the Pd/alumina catalysts based on the data obtained by DRIFT and activity experiments. The kinetics for the NO reduction by CO over Pd/Al2O3 was also derived. With the methods employed, the mechanistic steps over the Pt-loaded zeolites and Pd/Al2O3-based catalysts could be derived quite precisely and easily for C3H6-SCR of NO. Reaction routes were determined to go via different formations of intermediates over the two catalysts, i.e. via organonitrogen and isocyanate routes, respectively. The IR techniques were discovered to be effective tools in applied engineering studies.

Το π–κυμένιο (p–ισοπρόπυλο τολουόλιο) είναι ένα πολύ σημαντικό προϊόν με μεγάλο εμπορικό ενδιαφέρον, καθώς αποτελεί κύριο συστατικό πολλών καλλυντικών, αρωμάτων, φαρμακευτικών προϊόντων, καθώς και την πρώτη ύλη για την παραγωγή της p–κρεσόλης. Η τρέχουσα διαδικασία παραγωγής του π–κυμενίου είναι η κατά Friedel–Crafts αλκυλίωση του τολουολίου με προπυλένιο ή προπανόλη–2, η οποία χρησιμοποιεί μεγάλες ποσότητες επιβλαβών οξέων, προκαλώντας πολλά προβλήματα χειρισμού στους εργαζόμενους με αυτό, προβλήματα διάβρωσης και προβλήματα διάθεσης των παραγόμενων αποβλήτων. Τα τελευταία χρόνια, η Πράσινη Χημεία έχει παρουσιασθεί ως η νέα προσέγγιση της Χημείας για την πρόληψη της μόλυνσης του περιβάλλοντος, καθώς και του σχεδιασμού χημικών προϊόντων και διεργασιών που είναι περισσότερο φιλικά προς το περιβάλλον. Η κατάλυση αποτελεί μία από τις κύριες αρχές, αλλά ταυτόχρονα και εργαλείο της Πράσινης Χημείας. Πιο συγκεκριμένα η ετερογενής κατάλυση, που εξυπηρετεί τους στόχους της Πράσινης Χημείας, λόγω της εξάλειψης της ανάγκης διαχωρισμού του παραγόμενου προϊόντος από τον καταλύτη. Επίσης, μία άλλη βασική παράμετρος της Πράσινης Χημείας είναι η χρήση της βιομάζας, ως ανανεώσιμη πρώτη ύλη, με σκοπό την παραγωγή ενέργειας και χημικών προϊόντων. Στην παρούσα εργασία, μελετάται η δυνατότητα καταλυτικής παραγωγής π–κυμενίου, βασιζόμενη στις αρχές της Πράσινης Χημείας. Για το σκοπό αυτό χρησιμοποιείται ως αντιδρών το α–λεμονένιο, ένα μονοτερπένιο το οποίο αποτελεί ανανεώσιμη πρώτη ύλη, καθώς είναι παραπροϊόν της βιομηχανίας χυμών λεμονιού και πορτοκαλιού, καθώς και της βιομηχανίας χάρτου και πολτού. Πιο αναλυτικά, μελετήθηκε η καταλυτική συμπεριφορά οξειδίων με μεγάλη ειδική επιφάνεια, όπως η SiO2, το MCM–41, ο ζεόλιθος NaY, η γ–Al2O3 και δύο δείγματα TiO2, με διαφορετικές ειδικές επιφάνειες, στην αντίδραση μετατροπής του λεμονενίου προς π–κυμένιο. Επίσης, ερευνήθηκε η επίδραση στη διεργασία τόσο της θερμοκρασίας της αντίδρασης, όσο και της σύστασης της ατμόσφαιρας κάτω από την οποία διεξαγόταν η αντίδραση. Τα πειράματα διεξήχθησαν σε αντιδραστήρα σταθερής κλίνης – ατμοσφαιρικής πίεσης, ενώ για την ανάλυση των λαμβανόμενων προϊόντων χρησιμοποιήθηκε αέριος χρωματογράφος – φασματογράφος μάζας (GC–MS). Από τους καταλύτες που μελετήθηκαν ο πιο αποτελεσματικός αποδείχθηκε η τιτάνια με τη σχετικά μεγάλη ειδική επιφάνεια ακολουθούμενη από την τιτάνια με την χαμηλότερη ειδική επιφάνεια, τον ζεόλιθο NaY και τη γ–Al2O3. Τόσο η σίλικα όσο και το MCM–41 παρουσίασαν μάλλον αμελητέα δραστικότητα. Επίσης, παρατηρήθηκε ότι η απόδοση σε π–κυμένιο αυξανόταν γενικά με τη θερμοκρασία, ενώ δεν επηρεαζόταν πρακτικά από την ατμόσφαιρα που διεξαγόταν η αντίδραση. Τέλος, στους 300 οC και χρησιμοποιώντας την τιτάνια με τη σχετικά μεγάλη ειδική επιφάνεια ως καταλύτη επιτεύχθηκε 90% απόδοση για το π–κυμένιο και 100% μετατροπή για το λεμονένιο. Η αυξημένη απόδοση της τιτάνιας αποδόθηκε σε επιτυχή συγκερασμό ανάμεσα στη σχετικά μεγάλη οξύτητα Brönsted και στη σχετικά εύκολη μεταβολή του λόγου Ti(IV)/Ti(III) κατά τη διάρκεια της αντίδρασης. Τα κινητικά αποτελέσματα επέτρεψαν να γραφεί ένα κινητικό σχήμα για τη διεργασία. / P–cymene is a very important product with great commercial interest because of its use as a main ingredient of cosmetics, perfumes and pharmaceutical products as well as raw material for the production of p–cresol. Current production is achieved by using the Friedel–Crafts reaction of toluene with propylene or propanol–2 which uses large quantities of harmful acids which, in turn, leads to industrial accidents, corrosion problems and the general difficulty of handling toxic wastes. A new concept of chemistry has been developed for confronting environmental problems. Green Chemistry is related to products and processes that are environmentally friendly. One of the basic tools of Green Chemistry is catalysis, mainly heterogeneous catalysis, because it allows the easy separation of the catalysts used from the final product. Moreover, following the principles of the Green Chemistry, biomass should be used in the production of renewable energy and chemical products. The present Thesis deals with the catalytic production of p–cymene based on the principles of Green Chemistry. In particular, we use a–limonene, by–product of the juice of orange and lemon industry as well as the paper industry, to produce p–cymene. A number of oxides with large specific surface area, such as SiO2, MCM–41, zeolite NaY, γ–Al2O3 and two samples of TiO2, were studied as catalysts. The effect of the reaction temperature and the composition of the atmosphere were also studied. All experiments were conducted on a fixed bed micro–reactor operating under atmospheric pressure coupled with an on–line Gas Chromatograph–Mass Spectrometer (GC – MS). The titania with the relatively high specific surface area was proved to be the most efficient catalyst among those studied. The following activity series has been obtained: «high surface area titania > small surface area titania > zeolite NaY > γ–Al2O3 > MCM–41 > SiO2». Negligible activity is exhibited by MCM–41 and SiO2. The percentage yield for p–cymene increases with temperature whereas is practically independent from the carrier gas. Very high percentage yield for p–cymene was obtained at 300οC over the high specific surface area titania (~90%). Complete transformation of a–limonene was obtained over the above catalyst at the same temperature. The very high activity obtained over this catalyst was attributed to good compromise between high acidity and easy transformation of the ratio Ti(IV)/Ti(III) during reaction. The kinetic results allow the clarification of the reaction scheme.

L’objectif de notre travail, était l’étude de deux classes de catalyseurs dans la réaction d’oxydation totale de COV. L’application visée étant la destruction à basse température de ces traces de polluants dans l’air. Des oxydes mixtes Co3O4-CeO2 ont été préparés par co-précipitation. Avec l’oxyde mixte (% atomique Co/Ce = 1), nous avons obtenu les meilleures performances catalytiques et montré que la réactivité étaient exaltée par une forte mobilité des oxygènes de coeur. Des catalyseurs à base d’or (2wt%) et de palladium (1wt%) ont été déposés sur des supports oxydes comme la cérine et le titane afin de favoriser une interaction métal support, ou sur un support alumine. Des solides à base d’alumine dopée au cérium, manganèse, fer et titane ont également été préparés. Pour l’or, l’évolution des performances catalytiques en fonction du support ont été les suivantes: Au2%/Al2O3 < Au2%/TiO2 < Au2%/CeO2, alors que pour le palladium nous avons obtenu les tendances suivantes : Pd1%/CeO2 < Pd1%/Al2O3 < Pd1%/TiO2. Pour l’Au, l’interaction métal support a permis d’expliquer les différences de réactivité alors que pour le palladium, l’activité est liée aux sites actifs de palladium Pd0/PdO présents à la surface. Avec les systèmes dopés, les résultats ont montré que les meilleurs catalyseurs étaient le Au2%/Ce5%/Al2O3 et le Pd1%/Ce5%/Al2O3. Cette exaltation a été attribuée à la grande mobilité des oxygènes en raison d’un défaut de structure induit par l’insertion des ions Al3+ au sein du réseau de la cérine et une forte interaction des particules très bien dispersées / The aim of the work was to study two classes of catalysts for the complete oxidation of volatile organic compounds. The target application for air pollution control is the total abatement of VOC at low temperature. Mixed oxide Co3O4-CeO2, were prepared by co-precipitation method. Among them, the mixed oxide corresponding to Co/Ce atomic ratio close to 1, was the best performing. The participation of surface oxygen species and high bulk mobile oxygen were the factors determining the high activity of Co30Ce in the total oxidation of propylene and toluene. Au (2wt%) and Pd (1wt%) catalysts were prepared over typical reducible oxides, such as CeO2 and TiO2. For comparison, catalysts over Al2O3, were also prepared. Moreover, the effect on the activity of Au and Pd supported over Al2O3 doped by cerium, manganese, iron and titanium was investigated. The so prepared Au and Pd catalysts were compared in the total oxidation of propylene. It was found that the activity of gold catalysts supported over un-doped oxides varied in the order: Au2%/Al2O3 < Au2%/TiO2 < Au2%/CeO2, while a different trend was observed for palladium catalysts: Pd1%/CeO2 < Pd1%/Al2O3 < Pd1%/TiO2. For Au catalysts, the nature of the support and the extent of interaction with the support are the key factors in determining the activity, whilst for the Pd supported ones, the activity seems to be governed by the nature of Pd species, Pd0/PdO, present in the catalyst. Au2%/Ce5%/Al2O3 and Pd1%/Ce5%/Al2O3 appear the best samples. The enhanced catalytic performances were attributed to high-oxygen mobility due to a defective ceria structure induced by the insertion of Al3+ ions into the lattice and also strong metal-support interaction between nanoparticles highly dispersed