The chemical complexity of the interstellar medium and combustion environments pose a challenge to the scientific community seeking to provide a molecular understanding of their combustion. More refined spectroscopic tools and methodologies must be developed to selectively detect and characterize the widening array of fuel and interstellar species. The direct relationship between molecular structure and rotational frequencies makes rotational spectroscopy highly structural specific; therefore, it offers a powerful means of characterizing polar molecules. However, rotational spectra usually contain transitions from multiple components with multiple conformations as well as other dynamical properties interleaved with one another, making the assignment of the spectra very challenging. This thesis describes experimental work using broadband microwave spectroscopy and vacuum ultraviolet time-of-flight mass spectrometry to address a number of challenging problems in the spectroscopy of gas complex mixtures.<div><br></div><div>In the first part of my work, we report details of the design and operation of a single apparatus that combines Chirped-Pulse Fourier Transform Microwave spectroscopy (CP-FTMW) with VUV photoionization Time-of-Flight Mass Spectrometry (VUV TOFMS). The supersonic expansion used for cooling samples is interrogated first by passing through the region between two microwave horns capable of broadband excitation and detection in the 2-18 GHz frequency region of the microwave. After passing through this region, the expansion is skimmed to form a molecular beam, before being probed with 118 nm (10.5 eV) single-photon VUV photoionization in a linear time-of-flight mass spectrometer. The two detection schemes are powerfully complementary to one another. CP-FTMW detects all components with significant permanent dipole moments. Rotational transitions provide high-resolution structural data. VUV TOFMS provides a gentle and general method for ionizing all components of a gas phase mixture with ionization thresholds below 10.5 eV, providing their molecular formulae. The advantages, complementarity, and limitations of the combined methods are illustrated through results on two gas-phase mixtures made up of (i) three furanic compounds, two of which are structural isomers of one another, and (ii) the effluent from a flash pyrolysis source with <i>o-</i>guaiacol as precursor. <br></div><div><br></div><div>The broadband spectrum of 3-phenylpropionitrile was recorded under jet-cooled conditions over the 8-18 GHz region. A novel multi-resonance technique called strong field coherence breaking (SFCB) was implemented to record conformer-specific microwave spectra. This technique involves sweeping the broadband chirp followed by selectively choosing a set of single frequencies pulses to yield a set of rotational transitions that belong to a single entity in the gas-phase mixture, aiding assignment greatly. Transitions belonging to anti and gauche conformers were identified and assigned and accurate experimental rotational constants were determined to provide insight on the molecular structure. Experimental rotational transitions provided relative abundances in the supersonic expansion. A modified line picking scheme was developed in the process to modulate more transitions and improve the overall efficiency of the SFCB multiple selective excitation technique.<br></div><div><br></div><div>The rotational spectrum of 2-hexanone was recorded over the 8-18 GHz region using a CPFTMW spectrometer. SFCB was utilized to selectively modulate the intensities of rotational transitions belonging to the two lowest energy conformers of 2-hexanone, aiding the assignment. In addition, the SFCB method was applied for the first time to selectively identify rotational transitions built off the two lowest energy hindered methyl rotor states of each conformer, 0a₁ and 1e. Since these two states have rotational energy levels with different nuclear spin symmetries, their intensities could be selectively modulated by the resonant monochromatic pulses used in the SFCB method. The difference spectra, final fit and structural parameters are discussed for the three assigned conformers of 2-hexanone.<br></div><div><br></div><div>Developing new experimental techniques that allow for species identification and quantification in the high-temperature environment of reacting flows is a continuing challenge in combustion research. Here, we combine broadband chirped-pulse microwave (rotational) spectroscopy with an atmospheric-pressure jet-stirred reactor as a novel method to identify key reactive intermediates in low-temperature and ozone-assisted oxidation processes. In these experiments, the gas sample, after being withdrawn from reactive dimethyl ether/O₂/Ar, dimethoxy methane/O₂/Ar, and ethylene/O₂/O₃/Ar mixtures, expands via a supersonic expansion into the high vacuum of a microwave spectrometer, where the rotationally cold ensemble of polar molecules is excited with short MW radiation frequency ramps (chirps). The response of the molecular ensemble is detected in the time domain and after a Fourier transformation, the spectral composition of the transient emission is obtained in the frequency domain. The observed rotational frequencies are uniquely correlated to molecular structures and allow for an unambiguous identification of the sampled species. Detection and identification of intermediates such as formaldehyde, methyl formate, formic acid, formic acid anhydride, and the primary ethylene ozonide via literature-known rotational frequencies are evidence for the superb identification capabilities of broadband chirped-pulse microwave spectroscopy. Strong-field coherence breaking is employed to identify and assign transitions due to a specific component. The observation of van der Waals complexes provides an opportunity to detect combustion intermediates and products that are impossible to detect by rotational spectroscopy as isolated molecules. <br></div><div><br></div><div>Lastly, preliminary data on important combustion precursors is studied including pentanal, <i>trans-</i>2-pentenal and <i>o-,m- </i>and <i>p</i>-vinylanisole. The rotational spectrum of these five molecules is recorded from the 8-18 GHz region under jet-cooled conditions. For pentanal and <i>trans-</i>2-pentenal, SFCB was utilized to dissect the broadband spectrum, identifying the four and two lowest energy structures, respectively. The structural parameters and finals fits are provided. <br></div>

<p>   </p> <p>Ambient Mass Spectrometry Imaging (MSI) is a powerful analytical tool in biomedical research that enables simultaneous label-free spatial mapping of hundreds of molecules in biological samples under native conditions. Nanospray desorption electrospray ionization (nano-DESI) is an emergent ambient MSI technique developed in 2010 that uses localized liquid extraction of molecules directly from surfaces. Like other liquid-extraction based techniques, nano-DESI relies on gentle removal of molecules from surfaces and soft ionization. High sensitivity and spatial resolution, versatility of the solvent composition, which may be used to tailor the extraction and ionization of selected molecules, quantification capabilities at the single-pixel level as well as compensation for matrix effects by adding a known standard to the solvent, and online derivatization are key features of nano-DESI MSI that position it as a unique analytical tool for studying biological systems. </p> <p>Despite the advantages that nano-DESI provides, there are still challenges associated with the structural characterization, extraction, and detection of certain molecular classes. Therefore, my dissertation research has focused on addressing these analytical challenges by developing innovative approaches that substantially enhance the performance of the nano-DESI technique in the study of complex biological systems. </p> <p>In this thesis, a systematic study of the solvent composition is carried out to aid in the detection of neutral lipids such as triglycerides thereby expanding the molecular coverage of nano-DESI experiments. Taking advantage of the versatility of the solvent composition, I developed an approach for the online derivatization of unsaturated lipids into lipid hydroperoxides using the reaction of singlet oxygen with C=C bonds. This method further expands the specificity of nano-DESI MSI by enabling the detection and imaging of positional lipid isomers. To aid in the analysis of complex mixtures and provide additional structural information in the form of collision cross sections, coupling of nano-DESI with a drift-tube ion mobility spectrometry is also reported along with examples of the powerful capabilities of this platform. Lastly, nano-DESI MSI is used to address the complexity in the analysis of individual skeletal muscle fibers. This collaborative project involves the development of a robust image registration approach of immunofluorescence imaging and high-spatial resolution nano-DESI MSI to obtain accurate chemical maps specific to each fiber type. The developments described in this thesis are key to understanding the dynamic metabolic processes on a molecular level with an unprecedented specificity and sensitivity.</p> <p>  </p>

No description available.

Despite comprehensive studies addressing the chemical kinetics of butanol isomers, relevant uncertainties associated with the emissions of relevant pollutants persists. Also, a lack of chemistry knowledge of processes designed to produce biofuels limits their implementation at industrial scales. Therefore, the first objective of this thesis was to use cutting-edge kinetic theories to calculate rate constants of propen-2-ol, 1-pronenol, and vinyl alcohol keto-enol tautomerizations, which account for the production of the harmful carbonyl species. The second objective was to use the predictive capabilities of dynamic theories to reveal new chemistry of syngas oxy-combustion in supercritical CO2 and complexities of the zeolite dealumination, two processes involved in coal and biomass conversion. Rate constants computations considered transition state theory with variational effects, tunneling correction, and multistructural torsional anharmonicity. The study also included pressure effects by using and improving the system-specific quantum Rice-Ramsperger-Kassel/modified strong collision model. The atomistic simulations used ReaxFF force fields in hydrogen/oxygen/carbon monoxide/ carbon dioxide mixtures to represent the syngas system and an MFI zeolite with different water loading to model the dealumination. The results show that the studied assisted tautomerizations have much lower energy barriers than the unimolecular process. However, the “catalytic” effect is efficient only if the partner molecule is at high concentrations. Pressure effects are pronounced in the chemically activated tautomerizations, and the improved algorithm to compute pressure-dependent rate constants overcomes the initial difficulties associated with its application to C3 or larger molecules at temperatures above 800-1000 K. Reactive molecular dynamics simulations revealed the role of CO2 as an initiator in the syngas oxy-combustion and a new step involving the formation of formic acid. Those simulations for the zeolite dealumination process also showed that proton transfer, framework flexibility, and aluminum dislodging mediated by silicon reactions are complex dynamic phenomena determining the process. These aspects complement the dealumination theory uncovered so far and establish new paths in the study of water-zeolite interactions. Overall, the rate constants computed in this work reduce relevant uncertainties in the chemical kinetic mechanisms of alcohol oxidation, and the molecular dynamics simulations broaden the chemical knowledge of processes aimed at the utilization of alternative energy resources.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Data on the process performance at different operating conditions are required to determine the feasibility of a separation process. Such data can be experimentally measured, but due to the time and costs associated with pilot plant scale experiments, the use of predictive process models are often preferred. The main aim of this project is to establish a working process model in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process aimed at the separation of mixtures of detergent range alkanes and alcohol isomers where similar boiling points or low relative volatilities can occur. Currently, an azeotropic distillation process is employed for the separation of detergent range alkanes and alcohols. Although this process shows good separation performance, some concerns regarding the operating conditions are raised: the preferred entrainer, diethylene glycol, is toxic to humans; very low operating pressures of 0.016 – 0.031 MPa and high temperatures of 473 K are required; additional processing units and materials are required to remove the entrainer from the product streams. An alternative process, supercritical fluid fractionation, is proposed in this work after previous studies have reported that this process have potential for the separation of alkanes and alcohols. The supercritical fluid fractionation process addresses the concerns of the azeotropic distillation process in the following ways: a non-toxic solvent, CO2, is used as the separating agent; mild temperatures of 344 K is proposed, but at the cost of the low operating pressures of the azeotropic process; and a single process unit and no additional material is required to separate the solvent from the product streams. A process model was developed in Aspen Plus® to evaluate the separation performance of the newly proposed supercritical fluid fractionation process and compare it to the current azeotropic distillation process. The development of the process model included the development of an accurate thermodynamic model in Aspen Plus®. After thorough evaluation of a number of cubic equations of state, the RK-ASPEN model was found to be superior in its representation and prediction of phase transition pressures for multi-component mixtures of detergent range alkanes and alcohols in the temperature range 318 – 348 K. Phase transition pressures could be predicted with an error of less than 6 % with the inclusion of regressed polar parameters and binary solute-solvent interaction parameters for two multi-component mixtures: CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) and CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol). Polar parameters were regressed from pure component vapour pressure data predicted with correlations available in Aspen Plus®. Binary interaction parameters were regressed from experimental bubble and dew point data. Binary bubble and dew point data were measured for a number of systems containing ethane or CO2 and a C10-alkane or C10-alcohol isomer at temperatures between 308 K and 353 K, and compositions ranging between 0.01 and 0.7 mass fraction solute. A comparison between the phase equilibrium data measured for these systems revealed that the structure of the molecule, and not only the molecular weight, influences its solubility in the supercritical solvent. The phase transition pressures of n-decane, 2-methylnonane, 3-methylnonane and 4-methylnonane did not differ significantly in CO2 or ethane, and these compounds will in all likelihood not be separated in a supercritical fluid fractionation process. The phase transition pressures measured for the C10-alcohol isomers decreased in both CO2 and ethane in the following order: 1-decanol, 3,7-dimethyl-1-octanol, 2-decanol, 2,6-dimethyl-2-octanol and 3,7-dimethyl-3-octanol. The position of the hydroxyl group and the number, length and position of the side branches, all influence the solubility behaviour and phase transition pressures of the isomeric alcohols in the supercritical solvent. Since the use of ethane did not show any significant benefits with regard to selectivity, the use of the less harmful and less expensive solvent, CO2, in further investigations was justified. The RK-ASPEN thermodynamic model, with the inclusion of the regressed polar and binary solute-solvent interaction parameters, was implemented in the process model and the separation performance of the process was simulated at different operating conditions for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) mixture. A comparison to experimental pilot plant data revealed that the model cannot be used to predict the separation performance at low fractionation temperatures (316 K) due to shortcomings in the thermodynamic model. However, the performance of the process at high fractionation temperatures (344 K) could be predicted well, with an error of 10 – 36 %. Simulations for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) mixtures showed that the composition of the feed mixture have a significant effect on the location and size of the operating window and optimum operating conditions. The optimum operating conditions were defined as the conditions where an acceptable selectivity ratio and alcohol recovery occurred simultaneously. Since the selectivity ratio and alcohol recovery have opposing optimization approaches, a number of possible optimum operating conditions exist, based on the product specifications. When an alcohol and an alkane with similar phase behaviour exist in a mixture, a distinct minimum selectivity ratio will occur at a point within the extract-to-feed ratio limits of the process. When the alkanes and alcohols present in a mixture do not have similar or overlapping phase transition pressures, the minimum selectivity ratio will typically cover a small range of extract-to-feed ratios at the high end limit of the extract-to-feed ratio range. To summarize: A process model was established in Aspen Plus® that can be used to determine the feasibility and separation performance of a supercritical fractionation process for a feed mixture of detergent range alkane and alcohol isomers. The model was used to prove that an SFF process is a feasible alternative process to consider for the removal of alkanes from mixtures of detergent range alcohol isomers, even where overlapping boiling points or low relative volatilities occur. During the development of the process model, the following significant novel contributions were made: · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical ethane, as published in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical CO2, as published in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · A thermodynamic model was developed in Aspen Plus® that can accurately predict the phase transition pressures of binary, ternary and multi-component mixtures of detergent range alkanes and alcohols in supercritical CO2, as published in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · A process model was developed in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process for the separation of mixtures of detergent range alkanes and alcohols. · Experimental and simulated results indicated that a supercritical fluid fractionation process can be implemented successfully to separate an alkane from a mixture of alcohol isomers, as was shown for two mixtures: CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol). / AFRIKAANSE OPSOMMING: Data oor die omvang van skeiding by verskillende bedryfstoestande word benodig om die lewensvatbaarheid van ’n skeidingsproses te bepaal. Sulke data kan eksperimenteel gemeet word, maar as gevolg van die tyd en kostes geassosieer met eksperimente op loodsaanlegskaal, word die gebruik van prosesmodelle verkies. Die hoofdoel van hierdie projek is om ’n werkende prosesmodel, wat daarop gemik is om C8 – C20 alkane en alkohol isomere te skei, in Aspen Plus® tot stand te bring om die omvang van die skeiding van ’n superkritiese fraksioneringsproses te meet. Tans word azeotropiese distillasie gebruik vir die skeiding van C8 – C20 alkane en alkoholisomere. Alhoewel goeie skeiding met hierdie proses bewerkstellig word, is daar sekere eienskappe van die proses wat aandag vereis: die voorgestelde skeidingsagent, dietileen glikol, is giftig vir mense; baie lae bedryfsdrukke van 0.016 – 0.031 MPa en hoë temperature van 473 K word benodig; addisionele proseseenhede en materiaal is nodig om die skeidingsagent van die produkte te verwyder. Die gebruik van ’n alternatiewe proses - superkritiese fraksionering - word in hierdie werk voorgestel nadat vorige studies getoon het dat hierdie proses die potensiaal het om alkane en alkohole te skei. Die superkritiese fraksioneringsproses spreek al die kommerwekkende eienskappe van azeotropiese distillasie aan soos volg: ’n veilige oplosmiddel, CO2, word as die skeidingsagent gebruik; gemiddelde temperature van 344 K word voorgestel, maar ten koste van lae bedryfsdrukke; ’n enkele proseseenheid en geen addisionele materiaal word benodig om die oplosmiddel van die produkte te skei nie. ’n Prosesmodel is in Aspen Plus® ontwikkel om die omvang van die skeiding wat deur die voorgestelde superkritiese fraksioneringsproses teweeggebring is, te evalueer en te vergelyk met die azeotropiese distillasieproses wat tans in gebruik is. Die ontwikkeling van die prosesmodel sluit die ontwikkeling van ’n akkurate termodinamiese model in Aspen Plus® in. Na deeglike evaluasie van ’n aantal kubiese toestandsvergelykings is gevind dat die RK-ASPEN-model die faseoorgangsdrukke van multi-komponentmengsels van C8 – C20 alkane en alkohole die beste voorspel binne die temperatuurbereik van 318 – 348 K. Faseoorgangsdrukke kon voorspel word met ’n fout van minder as 6 % met die insluiting van voorafbepaalde polêre parameters en binêre interaksie-parameters vir twee multi-komponentmengsels: CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) and CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol). Polêre parameters is bepaal met dampdruk data, wat voorspel is met korrelasies in Aspen Plus®. Binêre interaksieparameters is van eksperimentele faseoorgangsdata bepaal. Binêre faseoorgangsdata is vir ’n aantal sisteme wat uit etaan of CO2 en ’n C10-alkaan- of C10-alkohol-isomeer bestaan, gemeet by temperature tussen 308 K en 353 K en samestellings van tussen 0.01 en 0.7 massafraksie van die opgeloste stof. ’n Vergelyking tussen die gemete fase-ewewigsdata het onthul dat die struktuur van die molekuul, en nie net die molekulêre massa nie, die oplosbaarheid van die stof in die superkritiese oplosmiddel beïnvloed. Die faseoorgangsdrukke van n-dekaan, 2-metielnonaan, 3-metielnonaan en 4-metielnonaan het geen skynbare verskille getoon in etaan of CO2 nie en dus sal hierdie stowwe in alle waarkynlikheid nie met ’n superkritiese fraksioneringsproses geskei kan word nie. Die faseoorgangsdrukke wat vir die C10-alkohol gemeet is, het in beide etaan en CO2 afgeneem in die volgende volgorde: 1-dekanol, 3,7-dimetiel-1-oktanol, 2-dekanol, 2,6-dimetiel-2-oktanol en 3,7-dimetiel-3-oktanol. Die posisie van die hidroksielgroep en die aantal, lengte en posisie van die sytakke beïnvloed die oplosbaarheidsgedrag van die alkohol-isomere in die superkritiese oplosmiddel. Aangesien die gebruik van etaan nie enige voordele ten opsigte van selektiwiteit inhou nie, is die gebruik van die minder skadelike en goedkoper oplosmiddel, CO2, vir verdere ondersoeke geregverdig. Die ontwikkelde termodinamiese model, met die insluiting van die polêre parameters en binêre interaksieparameters, is in die prosesmodel ingesluit en die omvang van die skeiding van die proses is gesimuleer by verskillende bedryfstoestande vir die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) mengsel. ’n Vergelyking tussen die gesimuleerde data en die eksperimentele loodsaanlegdata het onthul dat die model nie die omvang van die skeiding kan voorspel by lae fraksioneringstemperature (316 K) nie as gevolg van die tekortkominge in die termodinamiese model. Die omvang van die skeiding by hoë temperature (344 K) kon egter goed voorspel word met ’n fout van 10 – 36 %. Simulasies van die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) mengsels het getoon dat die samestelling van die voermengsel ’n beduidende effek op die grootte van die bedryfsvenster en optimum bedryfstoestande het. Die optimum bedryfstoestande word gedefinieer as die toestande waar ’n aanvaarbare selektiwiteitsverhouding en alkoholherwinning terselfdertyd voorkom. Aangesien die selektiwiteitsverhouding en alkoholherwinning teenstrydige optimeringsbenaderings het, bestaan daar ’n aantal optimum bedryfstoestande gebaseer op die produkspesifikasies. Wanneer ’n alkohol en ’n alkaan met ooreenstemmende fasegedrag saam in ’n mengsel voorkom, bestaan daar ’n duidelike minimum selektiwiteitsverhouding by ’n punt binne die ekstrak-tot-voer-verhoudingslimiete van die proses. Wanneer die alkane en alkohole in ’n mengsel nie ooreenstemmende fasegedrag toon nie, sal die minimum selektiwiteitsverhouding oor ’n reeks ekstrak-tot-voer-verhoudings voorkom, tipies by die hoë limiet van die ekstrak-tot-voer-verhoudingsreeks. Om op te som: ’n Prosesmodel is in Aspen Plus® tot stand gebring wat die lewensvatbaarheid en omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses vir voermengsels van C8 – C20 alkane en alkohol-isomere kan voorspel. Die model is gebruik om te bewys dat ’n superkritiese proses ’n lewensvatbare alternatiewe proses is om te oorweeg vir die verwydering van alkane uit mengsels van alkohol-isomere, self waar ooreenstemmende kookpunte of lae relatiewe vlugtigheid tussen komponente voorkom. Tydens die ontwikkeling van die prosesmodel is die volgende beduidende nuwe bydraes gemaak: · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan- en C10-alkohol-isomere in superkritiese etaan, soos gepubliseer in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan and C10-alkohol isomere in superkritiese CO2, soos gepubliseer in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · ’n Termodinamiese model is ontwikkel in Aspen Plus® wat die faseoorgangsdrukke van binêre, ternêre en multi-komponent mengsels van C8 – C20 alkane en alkohol-isomere in superkritiese CO2 akkuraat kan voorspel, soos gepubliseer in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · ’n Prosesmodel is ontwikkel in Aspen Plus® wat die omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses, gemik op die skeiding van mengsels van C8 – C20 alkane en alkohol-isomere, kan voorspel. · Eksperimentele en gesimuleerde resultate toon aan dat ’n superkritiese fraksioneringsproses suksesvol geïmplementeer kan word vir die skeiding van ’n alkaan vanuit ’n mengsel van alkohol-isomere, soos bewys vir twee mengsels: CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol).

<p>Disease-specific compounds (biomarkers) are analyzed in clinical laboratories to assist with diagnosing diseases. This thesis describes development and validation of liquid chromatography tandem mass spectrometry (LC-MS/MS) based tests for diagnosing a diverse group of endocrine and metabolic diseases. The analytical methods used on-line and off-line sample extraction and analytical derivatization as means of enhancing the analytical sensitivity, specificity and clinical utility. All developed methods were extensively validated and reference intervals for the biomarker concentrations were established in blood samples of healthy adults and children. Advantages of the LC-MS/MS as an analytical technique include possibility of simultaneous measurement of multiple analytes and ability of confirming their identity. In this thesis we proposed and evaluated approaches for the assessment of the specificity of analysis in the methods that use tandem mass spectrometry detection. To enhance throughput of the LC-MS/MS tests for the biomarkers that have endogenous or exogenous isomers an approach was developed for quantitation of isomers from unresolved chromatographic peaks. Using methods developed in this thesis we performed a study of the steroidogenesis in ovarian follicles of healthy women and women with polycystic ovary syndrome (PCOS). Obtained data on the steroid concentrations and associations between the steroid metabolites in the pathway would be helpful for better understanding of the ovarian pathophysiology. Potential biomarkers of PCOS were identified in the thesis; further studies will be necessary to confirm their clinical utility.</p>

A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal–organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

L’objectif de cette thèse est de développer une méthode expérimentale permettant de mesurer simultanément des coefficients de co-diffusion dans les zéolithes, pour des mélanges de paraffines en C6 mono et di-branchées, dont les cinétiques de diffusion sont très différentes. Les espèces sont le 2- et le 3-methyl-pentane (2MP et 3MP) et le 2-2- et le 2-3-dimethyl-butane (22DMB et 23DMB) et l'adsorbant est une silicalite. Cette méthode est basée sur la réponse en sortie d’un lit fixe d’adsorbant à une variation cyclique de la composition à son entrée. La conception d’un modèle faisant intervenir des paramètres cinétiques et thermodynamiques a également être effectuée afin de simuler les courbes de perçages des différents constituants en mélange et sur plusieurs cycles. Les conditions expérimentales sont proches des conditions industrielles, à savoir en phase liquide et à fort taux de remplissage de l’adsorbant (185°C et 35 bars) L’écriture d’un modèle de diffusion, basé sur l’équation de Maxwell-Stefan appliquée au "Dusty Gas Model", dans ces conditions de fonctionnement, implique d’introduire des grandeurs volumiques qui permettent de redéfinir les contraintes liées à la saturation de l'adsorbant. De plus, tout en conservant la simplicité du modèle "Single File Diffusion" (pas de contre-diffusion microporeuse), nous avons montré que la prise en compte d’un flux volumique relatif associé au solide permet de conserver l’indépendance des coefficients de diffusion dans le cristal. Les simulations des courbes de perçage – sur un seul cycle pour les molécules rapides et sur plusieurs cycles pour les molécules lentes – indiquent que les coefficients de diffusion des différents isomères suivent l'ordre suivant : D3MP ˜ D2MP > D23DMB > D22DMB, avec un écart de trois ordres de grandeurs entre le 3MP et le 22DMB, ce qui laisse supposer qu'un procédé de séparation basé sur une sélectivité diffusionnelle peut être envisagé. Cependant, les tests de perçage en condition cyclique permettant de caractériser de manière plus précise le système, il a été possible de mettre en évidence une très lente accumulation du 22DMB au cours des cycles sous certaines conditions opératoires, phénomène qui peut s'avérer indétectable sur un faible nombre de cycles et/ou sur le profils de concentration des autres espèces. Ce phénomène a pour conséquence de diminuer les performances de l'adsorbant, aussi bien d'un point de vue capacitif que d'un point de vue sélectif / The aim of this work is to develop a new experimental method in order to determine simultaneously co-diffusion coefficients in zeolites for mixtures of single- and di-branched C6 paraffins, with totally different diffusion kinetics. The species are 2- and 3-methyl-pentane (2MP and 3MP) and 2-2- and 2-3-dimethyl-butane (22DMB and 23DMB) and the adsorbent is a silicalite. This method is based on the output measurement of an adsorbent column subjected to cyclic variations of its input concentration. The analysis of the mixture experimental breakthrough curves, on several cycles, is carried out using a mathematical model, based on Maxwell-Stefan theory of multi-component diffusion, allowing an estimation of thermodynamic and kinetic parameters. The experimental conditions are close to industrial constraints, i.e. at very high adsorption loading, and in the liquid phase (185°C and 35 bars). This requires to develop a modified Maxwell-Stefan diffusion model, applied to the "Dusty Gas Model", including volume constraints in the crystal which implies to redefine the adsorbent saturation. Moreover, while preserving the simplicity of the "Single File Diffusion" model (no counter-diffusion), a relative volumetric flow of the solid is taken into account, allowing to ensure the independence of the diffusion coefficient of each component in the adsorbent. The Maxwell-Stefan diffusion coefficients for the different isomers, obtained from breakthrough curves simulations – on one cycle for fast diffusing species and several cycles for slow molecules – are in the sequence : D3MP ˜ D2MP, > D23DMB > D22DMB, with a difference of three orders of magnitude between 3MP and 22DMB. This implies that a separation process based on kinetic selectivity can be considered. The cyclic breakthrough experiments, allowing a better characterization of the system, highlight a very slow accumulation of the 22DMB isomer during cycles for specific operating conditions, which may be undetectable on a small number of cycles and on the profiles of the other components.. This phenomenon involves a decrease of the adsorbent performances, in terms of capacity as well as selectivity

Afin de répondre aux demandes des industriels de nouveaux matériaux poreux sont testés pour de nouvelles applications ou pour améliorer les procédés existants. Les adsorbants de types Metal Organic Frameworks(MOFs) ont des structures construites à partir d'unités inorganiques reliées entre elles par des ligands organiques. La possibilité de varier ces deux entités, offre une grande diversité de structures avec des cavités de tailles contrôlées. L'objectif de cette thèse a été d'évaluer les performances des MOFs pour l'adsorption de composés organiques et de comprendre les mécanismes d'adsorption. Les deux problématiques sélectionnées sont d'intérêt pour l'industrie pétrochimique. La séparation du para-xylène des autres isomères du xylène et de l'éthylbenzene, permets de répondre à la demande de matière première pour la synthèse du polytéréphtalate d'éthylène. L'adsorption des composés azotés et soufrés (teneur fixée par des législations), permets la purification de carburants. Notre étude thermodynamique est basée sur la réalisation d'isothermes d'adsorption et la détermination d'enthalpies d'adsorption par microcalorimétrie en phase liquide. L'adsorption des vapeurs des xylènes purs a été étudiée pour comprendre l'effet du solvant. Une grande variété de comportement a été observée selon les structures des MOFs. Nous avons par exemple mis en évidence l'effet de l'empilement moléculaire des isomères du xylène sur la sélectivité des MOFs. Nous avons démontré que la flexibilité des MOFs intervient sur les interactions au cours de l'adsorption des xylènes. Nous avons mis en évidence une sélectivité des MOFs possédant un centre métallique insaturé en faveur des composés azotés / In order to meet the industrials requirements, new porous materials are tested for new applications or to improve existing processes. The Metal Organic Frameworks (MOFs) are hybrids crystalline compounds made up of clusters (or chains) of metal ions coordinated by organic linkers to form three dimensional structures. The ability to vary these two entities offers to MOFs a wide variety of organized structure with pore sizes controlled. The aim of this thesis was to evaluate the MOF performances for the adsorption of organic compounds and also understand the related adsorption mechanism. The two selected issues are of interest for the petrochemical industry. The para-xylène separation from the other xylene isomers (ortho, meta) and ethylbenzene, allows to meet the demand for raw materials in the polyethylene terephthalate (PET) synthesis. The nitrogen and sulphur compounds adsorption allows the purification of fuels (sulphur content set by legislation). We present a thermodynamic study of adsorption from solution based on the determination of adsorption isotherms by depletion method and adsorption enthalpies by microcalorimetry. The pure xylenes vapour adsorption was also studied to understand the solvent effect. A wide variety of behaviour has been observed depending on MOF structures. For example we demonstrated the effect of xylene isomers molecular packing on MOF selectivity. Furthermore we have shown that the MOF structure flexibility influence the interactions involved during xylene isomers adsorption. We also demonstrated that MOF with unsaturated metallic centres present selectivity for nitrogen compounds (Lewis acid/base).

Doctor of Philosophy / Department of Mechanical Engineering / Steven J. Eckels / Byron W. Jones / Poor air quality in commercial aircraft cabins can be caused by volatile organophosphorus (OP) compounds emitted from the jet engine bleed air system during smoke/fume incidents. Tri-cresyl phosphate (TCP), a common anti-wear additive in turbine engine oils, is an important component in today’s global aircraft operations. However, exposure to TCP increases risks of certain adverse health effects. This research analyzed used aircraft cabin air filters for jet engine oil contaminants and designed a jet engine bleed air simulator (BAS) to replicate smoke/fume incidents caused by pyrolysis of jet engine oil. Field emission scanning electron microscopy (FESEM) with X-ray energy dispersive spectroscopy (EDS) and neutron activation analysis (NAA) were used for elemental analysis of filters, and gas chromatography interfaced with mass spectrometry (GC/MS) was used to analyze used filters to determine TCP isomers. The filter analysis study involved 110 used and 74 incident filters. Clean air filter samples exposed to different bleed air conditions simulating cabin air contamination incidents were also analyzed by FESEM/EDS, NAA, and GC/MS. Experiments were conducted on a BAS at various bleed air conditions typical of an operating jet engine so that the effects of temperature and pressure variations on jet engine oil aerosol formation could be determined. The GC/MS analysis of both used and incident filters characterized tri-m-cresyl phosphate (TmCP) and tri-p-cresyl phosphate (TpCP) by a base peak of an m/z = 368, with corresponding retention times of 21.9 and 23.4 minutes. The hydrocarbons in jet oil were characterized in the filters by a base peak pattern of an m/z = 85, 113. Using retention times and hydrocarbon thermal conductivity peak (TCP) pattern obtained from jet engine oil standards, five out of 110 used filters tested had oil markers. Meanwhile 22 out of 74 incident filters tested positive for oil fingerprints. Probit analysis of jet engine oil aerosols obtained from BAS tests by optical particle counter (OPC) revealed lognormal distributions with the mean (range) of geometric mass mean diameter (GMMD) = 0.41 (0.39, 0.45) [mu]m and geometric standard deviation (GSD), [sigma][subscript]g = 1.92 (1.87, 1.98). FESEM/EDS and NAA techniques found a wide range of elements on filters, and further investigations of used filters are recommended using these techniques. The protocols for air and filter sampling and GC/MS analysis used in this study will increase the options available for detecting jet engine oil on cabin air filters. Such criteria could support policy development for compliance with cabin air quality standards during incidents.