<p> The reaction of lead tetra-acetate with ketone carbohydrazones and 4-substituted semicarbazones gave a series of 2-(substituted imino)-△^3-1,3,4-oxadiazolines. Spectroscopic and chemical evidence is presented to establish the proposed structure, and the scope of the reaction is described. The thermolysis of the 5,5-diaryl-2-phenylimino-△^3-1,3,4-oxadiazolines was studied in chlorobenzene solution. The results of kinetic experiments (gas evolution and infra-red) are reported, and the mechanism of the decomposition is discussed. A survey of the literature pertaining to related lead tetra-acetate oxidations, and to decomposition of cyclic azo compounds is presented.</p> / Thesis / Doctor of Philosophy (PhD)

The ozone decomposition reaction was performed in a 2.5cmx40cmx450cm two dimensional (2D) catalytic fluidized bed reactor. Commercial FCC catalyst impregnated with Fe2O3 was used at superficial gas velocities ranging between 0.006 m/s and 0.55 m/s. The onset velocity of the turbulent regime (uc) was determined as 0.4 m/s. The catalyst activity was optimized so that the effect of inter-phase mass transfer could be accentuated in the conversion reading. It was found that the general bubbling-turbulent model of Thompson et. al. (1999) combined with the mass transfer correlations of Kunii and Levenspiel (1991), Foka et. al. (1996) and Miyauchi et. al. (1980)gave reasonable predictions of the experimental data. The gradual improvement of reactor performance with an increase in superficial velocity (as predicted by the Thompson et. al. model) was not observed; instead a discontinuity of the reactor performance was noted in the vicinity of uc. More experimental work is required to substantiate this observation. Copyright / Dissertation (MEng)--University of Pretoria, 2009. / Chemical Engineering / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20389号 / 工博第4326号 / 新制||工||1670(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 陰山 洋, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

This thesis represents a small contribution to our understanding of metastable patterns in various stochastic models from physics and biology. By a \emph{metastable pattern}, we mean a pattern that appears to persist in a regular fashion on some timescale, but disappears or undergoes an irregular change on a longer timescale. Metastable patterns frequently result from stochastic perturbations of patterns that are stable without perturbation. In this thesis, we study stochastic perturbations of stable spatiotemporal patterns in several classes of PDE and integral equations. In particular, we address two major questions: \begin{enumerate}[Q1.] \item When perturbed by noise, for how long does a pattern that is stable without noise persist? \item How does the stochastic perturbation affect the average behaviour of a pattern on the timescale where it appears to persist? \end{enumerate} To address these questions, we pursue two lines of inquiry: the first based on the theory of \emph{quasi-ergodic measures}, and the second based on \emph{phase decomposition techniques}. In our first line of inquiry we present novel, rigorous connections between metastability of general infinite dimensional stochastic evolution systems and the spectral properties of their sub-Markov generators using the theory of quasi-ergodic measures. To do so, we develop a novel $L^p$-approach to the study of quasi-ergodic measures. We are then able to draw conclusions about the metastability of travelling waves and other patterns in a class of stochastic reaction-diffusion equations. For instance, we obtain a rigorous definition of the \emph{quasi-asymptotic speed}~of a travelling wave in a stochastic PDE. We moreover find that stochastic perturbations of amplitude $\sigma>0$ cause the quasi-asymptotic speed of certain travelling waves to deviate from the deterministic wave speed by a constant that is approximately proportional to $\sigma^2$. In our second line of inquiry, the dynamics of our (infinite dimensional) stochastic evolution system are projected onto a finite dimensional manifold that captures some property of a metastable pattern. While most previous studies using phase reduction techniques have used the \emph{variational phase}, we take an approach based on the \emph{isochronal phase}, inspired by classical work on finite dimensional oscillatory systems. When the pattern in question is a travelling wave, the isochronal phase captures the position of the wave at a given point in time. By exploiting the regularity properties of the isochronal phase, we are able to prove several novel results about the metastable behaviour of the reduced dynamics in the small noise regime in a very large class of stochastic evolution systems. These results allow us to moreover compute the noise-induced changes in the speed of stochastically perturbed travelling waves and other patterns. The results we obtain using this approach are numerically precise, and may be applied to a very general class of stochastic evolution systems.

No description available.

There are many large-scale contacting methods for gas reactions requiring a solid catalyst. The catalytic gas-solid Fluidized Bed Reactor (FBR) is one of the popular methods in industry. In FBRs the bulk of the gas throughput is present as lean bubbles, mostly deprived of solids, bubbling through a solids-rich emulsion phase. The movement of gas into and out of the emulsion often dictates the performance of an FBR. During the past five decades major contributions have been made towards the understanding of FBRs, although numerous gaps still exist, especially at higher bubbling regime velocities. This work follows an integrated approach for the simultaneous measurement of hydrodynamics and reactor performance. Hydrodynamics are measured using fast X-Ray Tomography (XRT), pressure analysis techniques and an optical fibre probe. Reactor performance is measured by utilizing the ozone decomposition reaction. Performance is quantified using a basic two-phase reactor model with an apparent overall interphase mass transfer (K0) parameter. Two 14 cm (ID) fluidized bed columns are used, one setup supporting the ozone decomposition reaction and the other installed within a fast XRT facility. Special emphasis is placed on superficial velocities (U0) spanning the entire bubbling regime up to the onset of the turbulent regime (Uc). The particle types employed are Geldart B sand particles and highly dense ferro-silicon (FeSi) particles. Fines are added to both particle types, resulting in a total of four particle systems (sand baseline; sand with fines; FeSi baseline; FeSi with fines). Time constraints on the XRT equipment limited the tomography measurements to the sand baseline particle system. The hydrodynamics of the other particle systems were limited to the pressure signal and optical probe measurements of the ozone decomposition setup. The results of the sand baseline system suggest that a distinction should be made between the low-interaction bubbling regime and the high-interaction bubbling regime. A change in mass transfer behaviour occurs around a U0/Uc value of 0.25. Reactor performance increases up to U0/Uc = 0.7, after which a decreasing trend is observed. An empirical correlation is proposed for the specific interphase mass transfer (kbe) of the higher velocity bubbling regime. This correlation is based on the integration of the hydrodynamics determined by means of XRT and reactor performance: 4-12 The hydrodynamic parameter β gives the best fit for the entire velocity range with an average error of 8%, although it is not recommended for U0/Uc<0.17. It is observed that the classical approach of penetration theory for interphase mass transfer, performs exceptionally well at low velocities (U0/Uc<0.34). The addition of fines to the FeSi particle type decreases the overall reactor performance, despite decreased bubble sizes. The solids fraction, however, unexpectedly increases with the addition of fines and a collapse of the emulsion phase is measured. It is therefore postulated that though flow in the emulsion phase is much higher for the FeSi baseline system and decreases with the addition of fines. For the sand particle type, the behaviour expected from literature is observed: reactor performance increases, bubble sizes decrease and the solids fraction decreases. Very distinct hydrodynamic behaviour is observed for all the fluidization regimes with XRT. Probability density distributions show there are still two phases present in the turbulent regime and that the emulsion-phase solids fraction remains independent of velocity until fast fluidization sets in. The turbulent regime has unique hydrodynamic behaviour, although voids appear to be a transient structure between the structures of the bubbling and fast fluidization regimes. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Chemical Engineering / unrestricted