Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 149-151).

Thesis (M.S.)--University of Minnesota. / Issued Dec. 1976. Includes bibliographical references (p. BI-1-BIV-2).

Magdeburg, University, Diss., 2005.

Hannover, University, Diss., 2005.

Bochum, Universiẗat, Diss., 2000.

München, Techn. Universiẗat, Diss., 2003.

Bibliography: p. 258-268. / The temperature inside the cylinder of a methanol-fuelled single-cylinder Ricardo E6 research engine running under knocking conditions, is measured by means of Coherent Anti-Stokes Raman Spectroscopy (CARS), and the pressure is measured with a pressure transducer. In order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch spectra at high pressure, a purely experimental technique is employed to derive temperatures from CARS spectra by cross-correlation with a reference library of spectra recorded in an accurately calibrated high-pressure high-temperature optical cell. The temperature and pressure profiles obtained from the engine running under knocking conditions, are then used as input data for chemical kinetic modelling of end-gas autoignition. Five published mechanisms (Grotheer et al 1992, Grotheer and Kelm 1989, Norton and Dryer 1989, Dove and Warnatz 1983, .and Esser and Warnatz 1987) are used in the autoignition study, and the results for the different mechanisms are compared. A good qualitative understanding of the mechanism underlying end-gas autoignition in the engine is obtained, although the calculated autoignition points occur slightly earlier than the observed point. A sensitivity analysis of the methanol autoignition system is undertaken, and the importance of the decomposition of hydrogen peroxide and the hydroperoxyl chemistry is demonstrated. The discrepancies between the predicted results of the different mechanisms is shown to be caused by a small number of sensitive reactions for which there are conflicting data. Finally, a linear mode analysis from the geometric qualitative theory of differential equations is performed on the non-linear chemical rate equations. The equilibrium points in the generalised phase space of the non-linear chemical system are shown to be defined in terms of three regions. The equilibrium points are unstable improper nodes in the first region (T < ll00K), unstable focii in the second region ( 1100K<T<1170K), and stable focii in the third region (T> 1170K).

archives@tulane.edu / Zeolites are microporous crystalline materials that are commercially used in ion exchange, adsorption, and catalysis applications. ZSM-5, the aluminosilicate with the MFI framework topology, is used industrially in fuel upgrading and xylene production, among other applications. Over the last three decades, zeolite research has produced several d- block metal-exchanged MFI zeolites relevant in problems including NOx abatement and partial oxidation of alkanes. Increased attention has been given to Cu, Ni, Fe, and Zn ions in this system, which have demonstrated the ability to activate methane and unlock the pathway for conversion to methanol. The direct partial oxidation of methane using molecular oxygen under mild conditions represents a holy grail reaction. Methane availability is currently experiencing a global excess, so high economic incentives are in place for any conversion scheme. Despite downhill energetics, several metal-exchanged zeolites have demonstrated the ability to oxidize methane without taking the products all the way to carbon dioxide. While conversion remains low, continued research has begun to elucidate the mechanisms by which the process is carried out and strategies for further improvements. Given the potential of MFI type materials, a detailed understanding of the reaction pathway and active sites is highly desirable. The first objective of this dissertation is to describe the chemical composition and state of a suite of exchanged MFI zeolites in a manner that informs the structure of active metal ion sites. This work utilizes the titration of certain metal ions with others to determine relationships between the two, with emphasis placed on stoichiometric exchange. It is concluded that Cu ions are not wholly preferential in the pore structure but in fact establish proportional uptake and retention ratios based in part on the exchange ion and solution conditions. The data also support the theoretical maximum of one stabilized Cu ion per two Z-sites without excessive exchange parameters. Conversely, Zn appears to be capped at one ion per Z-site, whereas Ni experiences a much lower threshold value. However, all ions reported in this dissertation were found to exchange with each other to some extent. The second objective of this dissertation is to detail the effects of these metal exchanges on the activity of MFI zeolites in the partial oxidation of methane. Catalytic testing indicates a broad window of tunable metal contents. Preliminary characterization suggests the existence of a –Cu–O–Cu– active site, where the bridging O acts as the principal methane binding site. Methanol STY* for the Cu-MFI zeolites approached 15 mmol molCu–1 hr–1 at loadings of Cu:Al ≥ 0.2. Titration of Cu-MFI using Na tended to extinguish the little remaining Brønsted acidity, which shut off the reaction entirely. Titration with the three d-block metals yielded mixed results; only 50% exchanged Zn/Cu- MFI zeolites performed better than the Cu standard in their own series. Zeolites with nearly equivalent Cu and Zn outperformed the highest reported literature values by approximately 40% on a per mole Cu basis: 9.41±0.33 vs. 5.2±0.05 mmol CH3OH/molCu/hr . / 1 / Zachary T. Gentle

Berlin, Techn. Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Berlin, Techn. Univ., Diss., 2001. / Computerdatei im Fernzugriff.