This thesis describes research that has been carried out during the years 2009-2013 as a part of my PhD project related to the method of selected ion flow tube mass spectrometry (SIFT-MS) and its application in interdisciplinary areas of research. SIFT-MS is a method that allows accurate quantification of trace gases and vapours presented in humid air with the focus on human breath; without any sample preparation and in real time. The thesis is divided into several parts. The first part reviews the history of mass spectrometry as a background for the quantitative analytical methods as PTR-MS and SIFT-MS. The second part discusses the detailed history of development of SIFT-MS, starting from principles of selected ion flow tube (SIFT) technique that has been used for study of ion-molecule reactions in the gas phase and forms the basis of SIFT-MS. The next part discusses volatile organic compounds of different biological origin: bacterial, plant and human breath metabolites that can be analyzed in real time using SIFT-MS. The main part "Results and Discussion" is divided into several subsections that serve as commentaries to the enclosed research papers published in peer reviewed journals. The first is a detailed step by step overview of the kinetics of ion molecule reactions which is the basis of...

This study presents a detailed gas-phase and surface kinetic model for n-tetradecane autothermal reforming to deconvolute the complex reaction network that provides the mechanistic understanding of reforming chemistry in a packed-bed reactor. A thermodynamic analysis study for diesel reforming was performed to map the carbon formation boundary for various reforming processes. Through a Langmuir-Hinshelwood-Hougen-Watson (LHHW) type of kinetic model, which was derived using a simple mechanistic study, the need for a detailed kinetic study including both gas-phase reactions and surface reactions was identified. Pt-CGO (Pt on Gd doped CeO2) and Rh-pyrochlore catalysts were synthesized and characterized. In an accelerated test for reforming of commercial-diesel, Rh-pyrochlore catalyst showed stable performance for 24 hrs, whereas Pt-CGO catalyst deteriorated in 4 hrs. Minimum structural change in Rh-pyrochlore catalyst compared to Pt-CGO catalyst was observed using redox experiments. An experimental kinetic study with an inert silica bed provided clear evidence that the gas-phase reactions are important to the kinetics of hydrocarbon reforming. “Reaction Mechanism Generator” (RMG) software was employed to generate a detailed gas-phase kinetic model containing nine thousand three hundred and forty-seven elementary reactions and four hundred and fifty-nine species. The model was validated against n-tetradecane ignition delay data, and inert bed autothermal reforming data. The RMG model was also extended to capture the high pressure and low temperature pyrolysis chemistry to predict pyrolysis experimental data. The reactor simulation using the RMG model identified the detailed chemistry of the reactions in the pre-catalytic zone. Gas-phase oxidation/pyrolysis converts the heavier hydrocarbons and oxygen in the pre-catalytic zone to lower molecular weight products prior to reaching the catalyst surface. The steam reforming reactions that are dominant on the surface of the catalyst primarily involve lower molecular weight oxidation/pyrolysis products. A multi-component micro-kinetic model containing two hundred and seventy surface reactions and fifty-two adspecies was developed using a semi-empirical Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Transition State Theory estimates were used for elementary reactions up to C3 species, and simple fragmentation reactions were assumed for higher hydrocarbon species. Model simulations indicated on the catalyst surface that hydrogen is initially produced by the water-gas-shift reaction and subsequently by steam reforming reactions. A major reaction path for ethylene formation from 1,3 butadiene in the post-catalytic zone of the reactor was also identified. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-04-24 13:23:31.163

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