<p> An experimental investigation has been conducted into the reduction of iron oxides under blast furnace conditions. The necessary equipment has been designed, constructed and tested, and a program of study on two types of prereduced ore materials has been completed.</p> / Thesis / Master of Science (MSc)

When speciality chemicals are manufactured within the pharmaceutical industry, they are often produced in stirred batch/semi-batch reactors. A ‘methodology’ was explored, to help with the development of continuous fixed-bed catalytic reactors for this sector. This was tested on two different types of model reactions: (a) In the first, the viability of producing tertiary amines via ‘borrowing hydrogen’ was explored, and the reaction of morpholine and benzyl alcohol was studied, on Ru and Pt catalysts. This provided an opportunity for an early involvement in small-scale batch testing of catalysts, and then experiments were performed with the catalyst supported on granules in a packed bed (i.d. = 7 mm, length = 300 mm). Although it was shown that continuous processing is viable, and that high conversions (e.g. 73 to 98%, at 150 ºC) could be achieved, unfortunately further work was necessary to identify a more robust catalyst system, before moving on to pilot-scale trials. (b) In the second, the partial oxidation of benzyl alcohol to benzaldehyde was studied, using a Pt catalyst on a carbon support. This proved to be successful, and the reaction was finally demonstrated at pilot-scale. Carbon monoliths were used as catalyst supports (monolith o.d. = 19 mm; length = 50 mm long; square 0.7 mm x 0.7 mm channels; catalyst loading 2.5 and 2.7 wt% Pt). With a liquid flow of 1 L h-1 and a reactant concentration of ~1 mol L-1, operating at 110 ºC, conversion ranged from 80 to 90% and selectivity from 65 to 99%. The catalyst system was tested for 160 h of operation, and retained its performance. While testing the 2nd reaction, a pilot-scale reactor was also developed, which could be used for a variety of novel reactions. The design was flexible and it was easy to insert and remove the catalytic monoliths.

A fundamental kinetic model based upon the Hougen-Watson formalism was derived as a basis not only for a better understanding of the reaction behavior but also for the design and simulation of industrial reactors. Kinetic experiments were carried out using a commercial potassium-promoted iron catalyst in a tubular reactor under atmospheric pressure. Typical reaction conditions were temperature = 620oC, steam to ethylbenzene mole ratio = 11, and partial pressure of N2 diluent = 0.432 bar. Experimental data were obtained for different operating conditions, i.e., temperature, feed molar ratio of steam to ethylbenzene, styrene to ethylbenzene, and hydrogen to ethylbenzene and space time. The effluent of the reactor was analyzed on-line using two GCs. Kinetic experiments for the formation of minor by-products, i.e. phenylacetylene, α-methylstyrene, β-methylstyrene, etc, were conducted as well. The reaction conditions were: temperature = 600oC ~ 640oC, a molar ratio of steam to ethylbenzene = 6.5, and partial pressure of N2 diluent = 0.43 bar and 0.64 bar. The products were analyzed by off-line GC. The mathematical model developed for the ethylbenzene dehydrogenation consists of nonlinear simultaneous differential equations in multiple dependent variables. The parameters were estimated from the minimization of the multiresponse objective function which was performed by means of the Marquardt algorithm. All the estimated parameters satisfied the statistical tests and physicochemical criteria. The kinetic model yielded an excellent fit of the experimental data. The intrinsic kinetic parameters were used with the heterogeneous fixed bed reactor model which is explicitly accounting for the diffusional limitations inside the porous catalyst. Multi-bed industrial adiabatic reactors with axial flow and radial flow were simulated and the effect of the operating conditions on the reactor performance was investigated. The dynamic equilibrium coke content was calculated using detailed kinetic model for coke formation and gasification, which was coupled to the kinetic model for the main reactions. The calculation of the dynamic equilibrium coke content provided a crucial guideline for the selection of the steam to ethylbenzene ratio leading to optimum operating conditions.

L'objet de cette thèse est la conception, le développement et la caractérisation d'un réacteur micro-ondes en continu pour mener tout type de réactions chimiques à températures élevées de manière fiable et dans des conditions optimisées. Le développement de ce réacteur a tout d'abord nécessité la caractérisation diélectrique et magnétique des matériaux et milieux utilisés. La simulation numérique a ensuite été utilisée afin de prédire les distributions de champ et température au sein des matériaux. L'interaction entre les ondes et les différents milieux a été finement étudiée. Elle démontre non seulement l'influence de la nature diélectrique du milieu réactionnel et du ratio volumique du fluide dans le réacteur sur le chauffage micro-ondes, mais aussi celle des dimensions de l'applicateur et de la disposition du réacteur dans ce dernier. L'hydrodynamique a également été introduite dans la simulation permettant de prédire les profils de température dans le réacteur en fonctionnement continu. L'ensemble des résultats numériques a fait l'objet de validations expérimentales qui ont aussi permis d'affiner le modèle thermique de l'ensemble conçu. Au final, une réaction de diestérification a été mise en œuvre et démontre l'efficacité thermique et chimique du réacteur. Au-delà de ce prototype, cette thèse établit un schéma général de conception d'un procédé chimique continu sous micro-ondes en ordonnant les étapes, respectant les règles clés de l'électromagnétisme, optimisant la propagation des ondes et les performances thermiques du système. / The aim of this thesis is the development and characterisation of an intensified continuous microwave reactor for green chemistry. The development of this reactor required, at first, the characterisation of the dielectric and magnetic properties of the used materials. A numerical simulation was then used to predict the field and temperature profiles within the materials. The influence of different parameters on the microwave heating was also studied, such as the influence of the dielectric nature of the reaction medium, the ratio of the fluid in the reactor, the arrangement of the reactor in the applicator and the size and shape of the latter. Hydrodynamics were also taken into account in the simulation to predict the temperature profiles in the reactor. All the numerical results were validated experimentally. Experimental results also made it possible to refine the thermal model of the reactor. In the end, an esterification reaction was carried out and it proved the thermal and chemical efficiency of the designed reactor. Beyond this prototype, this thesis establishes a general scheme for the design of a continuous chemical process under microwaves whilst following the key rules of electromagnetism and optimising the wave propagation and the thermal performance of the reactor.

Ignition and combustion characteristics of n-butanol/air, 2-butanol.air and isobutanol/air mixtures at stoichiometric (ϕ = 1) and lean (ϕ = 0.5) conditions were investigated in a micro flow reactor with a controlled temperature profile from 323 K to 1313 K, under atmospheric pressure. Sole distinctive weak flame was observed for each mixture, with inlet fuel/air mixture velocity set low at 2 cm/s. One-dimensional computation with comprehensive chemistry and transport was conducted. At low mixture velocities, one-stage oxidation was confirmed from heat release rate profiles, which was broadly in agreement with the experimental results. The weak flame positions were congruent with literature describing reactivity of the butanol isomers. These weak flame responses were also found to mirror the trend in Anti-Knock Indexes of the butanol isomers. Flux and sensitivity analyses were performed to investigate the fuel oxidation pathways at low and high temperatures. Further computational investigations on oxidation of butanol isomers at higher pressure of 5 atm indicated two-stage oxidation through the heat release rate profiles. Low temperature chemistry is accentuated in the region near the first weak cool flame for oxidation under higher pressure, and its impact on key species – such as hydroxyl radical, hydrogen peroxide and carbon monoxide – were considered. Both experimental and computational findings demonstrate the advantage of employing the micro flow reactor in investigating oxidation processes in the temperature region of interest along the reactor channel. By varying physical conditions such as pressure, the micro flow reactor system is proven to be highly beneficial in elucidating oxidation behavior of butanol isomers in conditions in engines such as those that mirror HCCI operations.

<p> The homogeneous partial oxidation of ortho-xylene vapour by air in a 316 s.s. flow reactor was studied in this work, which was conducted in connection with, and preceding an investigation of the kinetics of catalytic vapour-phase partial oxidation of a-xylene. The main purpose of the present work was to make an exploratory study of the contribution of the homogeneous reaction, if any, in as much as it would affect the catalytic oxidation to be studied on the same experimental set-up. This would permit the correction for the rate of homogeneous reaction during the catalytic reaction under a range of experimental conditions, or, reveal conditions under which the catalytic reaction could be conducted with minimum contribution by the homogeneous reaction. </p> <p> The three variables studied and the range of conditions for each are as follows : 1. Air: o-xylene molar ratio: ,124 to J78 2. Residence time: 0.443 sec. to 0.539 sec. 3. Temperature: 430° C to 490° c </p> <p>The reaction product stream was analyzed mainly by Gas Chromatography, both qualitatively and quantitatively. Qualitative analyses of liquid samples of the reactor condensate were also conducted using a Nuclear Magnetic Resonance Spectrometer, Mass Spectrometer, Infrared Spectrophotometer and also by conventional chemical techniques. </p> <p> Product analysis indicated a-xylene oxide as the reaction product at the lmv conversions studied. An empirical correlation obtained by statistical analysis of the experimental data, relating the conversions obtained and the variables studied, has been proposed to calculate the extent of the homogeneous reaction under the conditions of a catalytic reaction study. The results obtained in this work are consistent with the suggested kinetics and mechanism for this reaction. </p> / Thesis / Master of Engineering (MEngr)

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The scientific community is undergoing a paradigm shift with the realization that the formation of carbonate minerals with diverse compositions and textures can be understood within the framework of multiple pathways to mineralization. A variety of common minerals can form via an amorphous pathway, where molecules or clusters aggregate to form a metastable amorphous phase that later transforms to one or more crystalline polymorphs. Amorphous calcium carbonate (ACC) is now recognized in a wide variety of natural environments. Recent studies indicate the chemical signatures and properties of the carbonate polymorphs that transform from an ACC pathway may obey a different set of dependencies than those established for the "classical" step-growth process. The Mg content of ACC and calcite is of particular interest as a minor element that is frequently found in ACC and the final crystalline products of calcified skeletons or sediments at significant concentrations. Previous studies of ACC have provided important insights into ACC properties, but a quantitative understanding of the controls on ACC composition and the effect of mineralization pathway on Mg signatures in calcite has not been established. This study utilized a new mixed-flow reactor (MFR) procedure to synthesize ACC from well-characterized solutions that maintain a constant supersaturation. The experimental design controlled the input solution Mg/Ca ratio, total carbonate concentration, and pH to produce ACC with systematic chemical compositions. Results show that ACC composition is regulated by the interplay of three factors at steady state conditions: 1) Mg/Ca ratio, 2) total carbonate concentration, and 3) solution pH. Findings from transformation experiments show a systematic and predictable chemical framework for understanding polymorph selection during ACC transformation. Furthermore, results suggest a chemical basis for a broad range of Mg contents in calcite, including high Mg calcite. We find that the final calcite produced from ACC is similar to the composition of the initial ACC phase, suggesting that calcite composition reflects local conditions of formation, regardless of the pathway to mineralization. The findings from this study provide a chemical road map to future studies on ACC composition, ACC transformation, polymorph selection, and impurities in calcite. / Ph. D.