Thesis (Ph. D.)--Landbouwhogeschool te Wageningen, 1981. / Summary in Dutch. Includes bibliographical references (p. 170-176).

No / Mechanistic understanding of competitive destabilization of carbamazepine:nicotinamide and carbamazepine:saccharin cocrystals under solvent free conditions has been investigated. The crystal phase transformations were monitored using hot stage microscopy, variable-temperature powder X-ray diffraction, and sublimation experiments. The destabilization of the two cocrystals occurs via two distinct mechanisms: vapor and eutectic phase formations. Vapor pressure measurements and thermodynamic calculations using fusion and sublimation enthalpies were in good agreement with experimental findings. The mechanistic understanding is important to maintain the stability of cocrystals during solvent free green manufacturing. / EPSRC (EP/J003360/1, EP/ L027011/1). MHD. Bashir would like to thank CARA for providing doctoral degree scholarship.

Yes / A simulation was conducted using Aspen HYSYS® software for an industrial scale condensate stabilization unit and the results of the product composition from the simulation were compared with the plant data. The results were also compared to the results obtained using PRO/II software. It was found that the simulation is closely matched with the plant data and in particular for medium range hydrocarbons. The effects of four process conditions, i.e. feed flow rate, temperature, pressure and reboiler temperature on the product Reid Vapour Pressure (RVP) and sulphur content were also studied. The operating conditions which gave rise to the production of off-specification condensate were found. It was found that at a column pressure of 8.5 barg and reboiler temperature of 180°C, the condensate is successfully stabilised to a RVP of 60.6 kPa (8.78 psia). It is also found that as compared to the other parameters the reboiler temperature is the most influential parameter control the product properties. Among the all sulphur contents in the feed, nP-Mercaptan played a dominant role for the finishing product in terms of sulphur contents.

Yes / In this paper, local meteorological data for a period of 35 years (from 1979 to 2013) from Kuujuaq station have been used to calculate the surface refractivity, N and to estimate the vertical refractivity gradient, dN1, in the lowest atmospheric layer above the ground. Monthly and yearly variations of the mean of N and dN1 are provided. The values obtained are compared with the corresponding values from the ITU maps. The long-term trend of the surface refractivity is also investigated. The data demonstrate that the indices N and dN1 are subject to an evolution which may have significance in the context of climate change (CC). Monthly means of N show an increasing departure from ITU-R values since 1990. Yearly mean values of the dN1 show a progressive decrease over the period of study. Seasonal means of dN1 show a decrease over time, especially for summer. Such a trend may increase the occurrence of super-refraction. However, currently available ITU-R recommendations for microwave link design assume a stationary climate, so there is a need for a new modelling approach.

Les aérosols fins ont un impact environnemental primordial. Ils influencent notamment la santé, ont un impact sur la visibilité et le climat. Les Aérosols Organiques Secondaires (AOS) représentent une fraction importante des aérosols fins. Les AOS résultent de la conversion d'espèces gazeuses, formées au cours de l'oxydation des composés organiques volatils (COV), en particules par des processus de nucléation et/ou condensation sur des aérosols préexistants. L'oxydation gazeuse des COV implique une myriade de composés secondaires intermédiaires pouvant participer à la formation d'AOS. Les AOS regroupent ainsi une très grande variété d'espèces. Afin d'étudier la formation d'AOS, il est nécessaire de développer des schémas chimiques décrivant explicitement la formation des composés secondaires. Le LISA a développé en collaboration avec le NCAR (National Center of Atmospheric Research) un générateur de schémas chimiques d'oxydation des composés organiques volatils : le GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere). Ce travail vise à tester (i) la fiabilité de GECKO-A à reproduire les concentrations d'AOS observées lors d'expériences en chambre de simulation atmosphérique (CSA) et (ii) la sensibilité de la formation d'AOS aux paramètres physico-chimiques tels que les pressions de vapeur saturante, effets de parois des CSA ou encore aux constantes cinétiques de réaction. Afin d'évaluer la pertinence des schémas chimiques générés avec GECKO-A, le modèle a été confronté à des expériences effectuées en CSA visant à évaluer la formation d'AOS. Le paramètre clé du partitionnement des composés organiques semi-volatils est la pression de vapeur saturante (Pvap) des espèces. Les trois méthodes considérées comme les plus fiables disponibles dans la littérature ont été implémentées dans GECKO-A afin de tester la sensibilité de la formation d'AOS à l'estimation des Pvap. Les pressions de vapeur saturantes estimées par les différentes méthodes présentent des valeurs très différentes s'étalant sur plusieurs ordres de grandeur. Malgré ces divergences marquées, la concentration et la spéciation simulées pour l'AOS s'avèrent en définitive peu sensibles à la méthode utilisée pour estimer les pressions de vapeur. Aucune méthode d'estimation de Pvap n'a par ailleurs permis de réconcilier les concentrations modélisées et observées. La concentration d'AOS demeure systématiquement surestimée de l'ordre d'un facteur 2. L'absorption des composés organiques gazeux semi-volatils sur les murs d'une chambre de simulation atmosphérique a ensuite été étudiée. L'intégration de ce processus dans le modèle conduit à diminuer de façon importante les concentrations simulées en AOS, jusqu'à un facteur 2. En outre, les rendements simulés après implémentation de ce processus apparaissent en bon accord avec les rendements mesurés en CSA. L'hypothèse d'une mauvaise représentation de certains processus en phase gazeuse a également été testée via des tests de sensibilité. En particulier, la sensibilité de la formation d'AOS aux constantes de réactions entre les COV et le radical OH a été explorée. Le système a montré une grande sensibilité à la variabilité des constantes cinétiques de réaction des COV avec le radical OH, que ce soit au niveau de l'estimation de la constante cinétique ou au niveau de la détermination du site d'attaque du radical OH. La sensibilité à l'estimation des constantes de décomposition des radicaux alkoxyles a également été testée. Cette étude n'a en revanche montré que peu d'effets sur le rendement en AOS formé / Fine aerosols have an important impact on health, visibility and climate. Secondary Organic Aerosols (SOA) represent an important fraction of fine aerosol composition. SOA are formed by nucleation or condensation onto pre-existing particles of gaseous species formed during the oxidation of emitted volatile organic compounds (VOC). VOC oxidation implies a huge number of secondary intermediates which are potentially involved in SOA formation. In order to study SOA formation, it is necessary to develop chemical schemes describing explicitly the formation and condensation of the gaseous secondary intermediates. The LISA has thus developed in collaboration with NCAR (National Center of Atmospheric Research) a generator of explicit chemical schemes : GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere). This work aims at testing (i) the reliability of GECKO-A to simulate observed SOA concentrations in Atmospheric Simulation Chamber (ASC) and (ii) exploring the SOA sensitivity to physico-chemical parameters such as saturation vapour pressures, chamber walls effects or kinetics rate constants. In order to assess GECKO-A's chemical schemes, the model has been confronted to chamber experiments performed to study SOA. Saturation vapour pressure (Pvap) is the key parameter controlling the gas/particles partitioning of organic compounds The three Pvap estimation methods considered as the more reliable in the literature have been implemented in GECKO-A. Pvap estimated by the three methods differs highly, up to several orders of magnitude. Despite of these discrepancies, simulated SOA concentration and speciation show a low sensitivity to the method used to estimate the Pvap. Moreover, none of the methods were able to make the model fit the observations. SOA concentration is systematically overestimated of a factor 2. Semi volatile organic compounds deposition on a chamber walls has been investigated. The implementation of this process in the model leads to a significant decrease of the simulated SOA concentrations, up to factor of 2. Simulated SOA yields are in good agreement with measured SOA yields. The hypothesis of a misrepresentation of some gaseous processes has then been investigated through sensitivity tests. SOA formation sensitivity to COV+ OH reactions rate constants has been explored. Results exhibited a high sensitivity to the rate constants estimations (regarding the rate constants values estimation, as well as the determination of the OH attack sites). The estimated alkoxy radicals decomposition rate constants have also been tested. This test showed however no significant impact on the simulated SOA yields

In this work VLE data was measured on three different pieces of equipment. Measurements were undertaken in the laboratory of Professor Gmehling in Oldenburg, Germany using two different static cells and in the Thermodynamics Research Unit (TRU), University of Natal, South Africa using a specially designed dynamic still. The three pieces of equipment used are as follows: i.) Static apparatus of Rarey and Gmehling (1993), ii.) Static apparatus of Kolbe and Gmehling (1985) as modified by Fischer and Wilken (2001), and, iii.) Dynamic apparatus ofHarris et al. (2003b). In total 370 data points were measured; fourteen sets of VLE data and eight vapour pressure data sets were measured. The work undertaken in Germany measured the systems hexane (1) + N-methylformarnide (2), benzene (1) + N-methylformamide (2), cWorobenzene (1) + N-methylformarnide (2) and acetonitrile (1) + N-methylformamide (2), at 363.15 K using the equipment of Rarey and Gmehling (1993). The systems CO2 (1) + Napthalene (2) at T = 372.45 K, 403.85 K and 430.65 K and CO2 (1) + Benzoic acid (2) at T= 403.28 K, 432.62 K and 458.37 K were measured on the equipment of Kolbe and GmeWing (1985) (as modified by Fischer and Wilken (2001)). Apart from the CO2 (1) + Napthalene (2) system at T = 372.45 K, all the above-mentioned data are new data. The equipment designed in the TRU was designed to operate between 300 and 700 K and between 1 kPa and 30 MPa. The equipment is of the dynamic recirculating VLE still type (DRVS) and is based on the principles of low-pressure stills. The still is constructed from uniquely machined Stainless-steel components and standard commercial Stainless-steel tubing and valves and is computer controlled to operate either isobarically or isothermally. Vapour pressures were measured on the new equipment for n-heptane, n-decane, n-dodecane, n-hexadecane, l-octadecene, 1-hexadecanol and d,l-menthol at low pressures and for acetone at high pressures. These vapour pressure measurements were used as test systems and ranged from 1.00 kPa to 1 000 kPa and from 308.33 K to 583.90 K. Cyclohexane (1) + ethanol (2) at 40 kPa and n-dodecane (1) + l-octadecene (2) at 26.66 kPa were measured as two isobaric VLE test systems. The VLE data measured for d,l-menthol (1) + l-isomenthol (2) at T= 448.15 K and n-dodecane (1) + l-octadecene (2) at P = 3.0 kPa represent new data measured on the equipment. All the VLE systems were modeled. Two data reduction methods were investigated: i.) the combined (r-rf) method, and, ii.) the direct method (H) method. Several different Gibbs excess models (Wilson, NRTL and UNIQUAC), equations of state (PengRobinson and virial) and mixing rules (Huron-Vidal, Wong-Sandler and Twu-Coon) were used in different combinations to find the best fit for the data. The Maher and Smith (1979) method was used to determine infinite dilution activity coefficients from the very smooth data of the N-methylformamide systems. Excess properties were determined for the CO2 (1) + Napthalene (2) and the CO2 (1) + Benzoic acid (2) systems. Although the equipment of Hams et al. (2003b) was able to measure data at high temperatures and elevated pressures, the precission of the data was not as good as was expected. Measuring the system temperature at elevated temperatures was especially problematic. The problem is attributed to the large mass of Stainless-steel used in the construction of the apparatus. To rectify this problem it is suggested that the equipment be modified to be lighter in weight and only capable of measuring VLE at moderate pressures (less than 3 MPa). / Thesis (Ph.D.)-University of Natal, Durban, 2004.

Orientador: Marco Aurelio Cremasco / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-21T16:19:52Z (GMT). No. of bitstreams: 1 Oliveira_CarlosEduardoLimade_M.pdf: 2139178 bytes, checksum: a60210b4b807de0c845fa8804f6ebb27 (MD5) Previous issue date: 2012 / Resumo: As espécies vegetais Lippia gracilis, popularmente conhecida como "alecrim-da-chapada" ou "alecrim-de-tabuleiro", são arbustos caducifólios, ramificados, com caule quebradiço, de até 2 m de altura...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The plant species Lippia gracilis, popularly known as "alecrim-da-chapada" or "alecrim-de-tabuleiro", are deciduous shrubs, branched, with brittle stems, up to 2 m tall. Belong to the family Verbenaceae and are widely distributed in America and Africa, mainly in tropical countries. ...Note: The complete abstract is available with the full electronic document / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Proprietary mixtures of amines and carboxylic acids are used as volatile corrosion inhibitors (VCIs) for the protection of steel and iron components against atmospheric corrosion during storage and transportation. Interactions between amines and carboxylic acids have been comprehensively reported in the literature. However, little is known about the nature of the vapours these mixtures emit. The present study focused on the development of the evolved gas analysis method which will help in the characterisation of the vapours released by VCIs. In the method, the evaporation of various amine-carboxylic acid binary mixtures was monitored by thermogravimetric analysis (TGA). The nature and the composition of the released vapours was followed by Fourier transform infrared (FTIR) spectroscopy. Mixtures consisting of triethylamine (TEA) and acetic acid were studied as a model compound using TGA-FTIR at 50 °C to validate the TGA-FTIR method. As vaporisation progressed, the composition of the remaining liquid and the emitted vapour converged to a fixed amine content of ca. 27 mol %. This is just above the composition expected for the 1:3 amine: carboxylic acid complex. Mixtures close to this composition also featured the lowest volatility. TGA-FTIR proved to be a convenient method for studying the evaporation of TEA-acetic acid mixtures, and the nature and composition of the released vapours. Amine addition leads to the dissociation of carboxylic acid dimers in favour salt formation. The formation of an ion pair between the amine and carboxylic acid was confirmed by the FTIR spectra of the liquid phase. The resulting amine-carboxylic acid mixtures showed a slow mass loss rate on TGA when compared with the pure amines and pure carboxylic acids. This indicated that the mixtures have low volatility, hence low vapour pressure compared with the pure components. The low vapour pressure of the mixtures was confirmed by the calculated gas permeability values. These values were much higher for the pure amines and the pure carboxylic acids. However, they dropped significantly on amine addition. The strong amine-carboxylic acid interaction is responsible for the suppressed volatility of the mixtures. No interaction is observed between amine and carboxylic acid molecules in the vapour phase at 230 °C. The method developed was applied to characterise the model compounds simulating the amine-carboxylic acid-based volatile corrosion inhibitors. These model systems contained the primary, secondary and tertiary amines (hexylamine, morpholine and triethylamine), as well as carboxylic acids with different chain lengths (acetic, propanoic, hexanoic and octanoic). These systems are usually employed as equimolar mixtures to protect ferrous metals against atmospheric corrosion. The key finding of the study was that the vapours released by such equimolar mixtures initially contain almost exclusively free amine. After prolonged vaporisation, a steady-state “azeotrope”-like composition is approached. It contains excess acid and features impaired corrosion-inhibition efficiencies according to the Skinner test. In part, this behaviour can be attributed to the mismatch between the volatilities of the amine and carboxylic acid constituents. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Chemical Engineering / unrestricted

<p> Techniques have been developed for making cryoscopic and vapour pressure measurements in anhydrous hydrogen fluoride. The cryoscopic constant for the solvent has been determined. </p> <p> The techniques developed have been used to determine the mode and extent of the ionization of some acids and bases of the HF system. The formation and stability of polymeric ions in the solvent has been investigated and the formation of the previously unknown anion As₂F₁₁⁻ has been shown. Cryoscopy has been used to detect a new polymeric 1:1 adduct of XeF₂ and SbF₅. Solutions of cyanides in HF have been investigated and the formation of a new polymeric cation Hg₂CN₃⁺, formed when mercury cyanide dissolves in HF, has been suggested. The results of some experiments on solvolysis reactions are also reported. </p> / Thesis / Doctor of Philosophy (PhD)

This research paper was submitted to the Department of Geography in fulfilment of the requirements of Geography 4C6. / This research details the presence of the land/ sea breeze circulation system near Churchill, Manitoba. Data collected from June 6 to August 13, 1987 were analyzed with respect to wind direction, temperature and vapour pressure to determine the effects of the system on the climate. Results indicate that there is a seasonal progression in wind frequency from dominantly onshore (42% of the time) to dominantly mixed winds (75% of the time). The frequency of the land/ sea breeze increases across the season. Smaller wind velocities, colder temperatures and larger vapour pressures are associated with onshore winds, while offshore winds have greater velocities, higher temperatures, and smaller vapour pressures. Offshore winds are 5-7°C warmer than onshore winds. The sea breeze is larger than the land breeze by a 3:2 ratio. / Thesis / Bachelor of Arts (BA)