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A novel hydrogen atom source, involving the 193.3 nm photolysis of nitrous oxide in the presence of hydrogen, is described. The system is shown to provide a very clean source of hydrogen atoms, particularly at temperatures above 400K. The H + C₂H₄ addition reaction is studied as a function of pressure (50-750 Torr He) and temperature (285-604K). Resonance fluorescence was used to monitor hydrogen atom concentrations in real time, following excimer (ArF) photolysis of the N₂0/H₂ precursor. The data are analysed using the Troe factorisation method. A model is developed, which allows the accurate calculation of the rate constant for the H + C₂H₄ reaction over a wide range of temperature and pressure. The direct observation of equilibration in the H + C₂H₄ = C₂H₅ system is reported for the first time, at temperatures between 775 and 850K. Hydrogen atom concentrations were monitored by resonance fluorescence, following 193.3 nm photolysis of the ethylene substrate. The equilibrium constant for the system K_c is determined much more precisely than has previously been possible. The standard heat of formation of the ethyl radical, ΔH^o_f, ₂₉₈(C₂H₅), is evaluated from the measured values of K_c(T), using Third Law methods and the known molecular and atomic parameters of H, C₂H₄ and C₂H₅ giving ΔH^o_f ₂₉₈(C₂H₅) = 28.36 ± 0.40 kcalmol . The quoted errors refer to 95.45% confidence limits and include contributions from the scatter of the data and from estimates of possible systematic errors. An excimer laser flash photolysis/ gas chromatographic end product analysis apparatus is described. The design of the photolysis cell allows its entire contents to be transferred to the analysis column, and enables total C₃ hydrocarbon yields as low as 2.6x10¹² molecules to be detected. A study of the photolysis of acetone at 193.3 nm is presented. The dependence of product yields on pressure (10-500 Torr He), temperature (300,600K), laser pulse energy and the presence of radical scavengers (NO,C₂H₄) is described. Under all experimental conditions, methyl radicals account for >95% of the radical products of the photolysis. The ArF photolysis of acetone is demonstrated to provide a very clean source of methyl radicals, suitable for use in conventional laser flash photolysis /kinetic spectroscopy experiments, at temperatures of up to 825K. Experiments are described, in which ethane and ethane/propylene mixtures, diluted to ∿5% in nitrogen, were pyrolysed in a quartz jetstirred reactor. Temperatures and conversions comparable to those achieved in industrial pyrolysis were employed. A kinetic model of ethane pyrolysis is developed, which qualitatively reproduces the experimental results. It is shown that the model predictions are extremely sensitive to a number of poorly defined rate constants.

There are three related studies within this thesis that examine the relationships between the properties of coals and the characteristics of the chars produced during rapid pyrolysis in a laboratory based Entrained Flow Reactor (EFR) which simulates the rapid rates of heating (104 to 105 °C s-1 ) typical of pulverised fuel boilers. The first study, using a suite of nine coals, investigates the influence of coal rank upon the generation of specific types of char, their respective physical and structural characteristics and their relative combustabilities. The second study, using a suite of twenty-two coals, examines various coal characterisation techniques and the correlations between those techniques and the associated char, and specifically investigates petrographic techniques as a means of characterising coal feedstock. The third study, using freshly mined coals, investigates the effects of oxidation (100°C, air) and weathering (ambient) upon standard analytical techniques and relates such changes to the physical, structural and combustion characteristics of the associated char. There is a common relationship between the elemental oxygen content of the parent coal and the generation of specific types of char for both vitrinite rich coals of differing coal rank and for the oxidised or weathered coals. There is also an inverse relationship (R 2 = 0.97) between the elemental oxygen content of a vitrinite rich coal and the proportion of cenospheres generated by pyrolysis at 1000°C using the EFR. Furthermore, the enhancement of char combustion at 1000°C (in an EFR) is related to the physical and structural characteristics of the char, i.e. the presence or absence of porosity (visible using SEM and TEM), the CO2 surface area and optical texture. A relationship exists (R2 = 0.83) between the morphology of a char (1000°C / N2) and the petrographic composition of the parent coal. The new term microlithotype, is an amalgamation of various vitrinite rich microlithotype classes that simplifies the nomenclature. A combination of calorific value, microlithotype, and coal rank (vitrinite reflectance) illustrates the influence of petrographic composition upon calorific value and also suggests a 'Province' dependency amongst the Cretaceous/Tertiary and Carboniferous coals studied. The coal properties calorific value, microlithotype, and coal rank can be related (R 2 = 0.91) to the proportion of porous chars for the Cretaceous/Tertiary suite of coals, illustrating the use of multivariate analyses when characterising coal feedstock. The effects of oxidation and weathering upon vitrinite fluorescence is also reported. The oxidation of coal at 100°C produces rims of quenched fluorescence which are not apparent within the weathered coals. Furthermore, the intensity of fluorescence at 650 nm (1650) decreases due to progressive oxidation or weathering, but decreases at a rate that is dependent upon the severity (temperature) of the conditions employed. The proposed oxidation quotient (0/Q = I65W%Romax) is a sensitive indicator of the oxidative conditions up to 100°C.

The ability of Pyrolysis-GC/MS analytical system---developed earlier to study the mechanism of Maillard reaction---was further enhanced to include chemical ionization, tandem mass spectrometry and a sample pre-concentration trap essential to detect minor components. Furthermore, the sample delivery during Py-GC/MS analysis was optimized and its relevance to the study of aqueous Maillard model systems was also characterized. The results of these investigations have indicated that the use of higher values of carrier gas flow rates or high constant pressures, during Py-GC/MS analysis can increase the total number of peaks and total area counts of the pyrograms. The influence of the reaction phase on the mechanism of formation of Maillard products was studied by comparison of 13C-label incorporation patterns of the common products formed in model systems consisting of labeled glycine and D-glucoses subjected to both pyrolysis and heating in aqueous solutions. Although pyrolysis reaction produced higher number of products, however, the major pathways of formation of variety of important Maillard products followed the same mechanism under both pyrolytic and aqueous systems. Furthermore, the advantages of the optimized system, were demonstrated both in the investigation of the mechanism of Maillard reaction, using L-serine and L-threonine as model systems and in the study of formation of Maillard generated carcinogens and chemical markers. Analyses of the pyrolysis products of [13C-1], [13C-2] and [13C-3] labeled L-serines and L-threonines have indicated the presence of three initial degradation pathways. Decarboxylation followed by deamination; a retro-aldol reaction and dehydration followed by isomerization, deamination and hydrolysis leading to the formation of pyruvic and 2-ketobutanoic acids. Interestingly, the amino carbonyl interaction between the resulting pyruvic acid and the aminoethanol can lead to the formation of an Amadori product i

High-intensity pyrolysis, rapid heating in an inert gas atmosphere at up to 20 atm pressure, of 6 Australian coals was examined to gain further insight into high-intensity processes such as Integrated Gasification Combined Cycles (IGCC). Experiments focussed on pyrolysis in a specially developed Wire Mesh Reactor (WMR). The particle temperature lagged that of the mesh by 0.2 seconds at a heating rate of 100??~C s -1 and was predicted by modelling. This is part of the reason the volatile yield (VY) results for 10 s hold-time at ???b1.7 wt% daf of coal, is much more reproducible than 1 s hold-time experiments at ???b4.2 wt% daf of coal. Four coals of the same rank did not behave identically when heated. Three of the coals had a pyrolysis VY the same as the proximate VM when heated to 100??~C at 1 atm but the fourth, higher inertinite coal had a 1 atm pyrolysis VY 90% of its proximate VM. All four coals of similar rank had a significant decrease in VY, between 10 and 20 wt% daf of coal, with pressure increasing from 1 to 20 atm. The two lower rank coals showed less decrease in VY with increasing pressure than the higher rank and higher inertinite coals. The lower decrease in VY with increased pressure was mostly attributed to the lower inertinite levels for both the coals of similar rank and VM, and the coals of lower rank. Char characteristics examined focussed on pore Surface Area (SA). For high intensity WMR and Drop Tube Furnace (DTF) pyrolysis experiments CO2 SA for char from a particular coal was similar but the BET SA different. This was due to the char in the WMR experiments having longer to form larger pores determined by BET N2 SA. Both the N2 and CO2 SA was more than an order of magnitude greater than for low intensity pyrolysis char. This highlights that the WMR can be used to attain char with similar CO2 SA characteristics as other high intensity pyrolysis experiments and to provide a more meaningful insight into char reactivity than low intensity chars do.

Thesis (Ph.D.)--University of Tulsa, 1989. / Bibliography: leaves 221-234.

Thesis (M.Sc.) -- University of Adelaide, Dept. of Organic Chemistry, 1971.

Thesis (doctoral)--Göteborg University, 2004. / Includes bibliographical references.