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Rate constants for the pyridine catalyzed ionic decomposition of t-butylperoxyformate (TBF) are measured in 15 non-hydroxylic solvents. The second order rate constants varied by a factor of 40 from the "slowest" solvent, tetra-chloroethylene, to the "fastest", 1,2-dichloroethahe. Ten different empirical equations are found and their ability to correlate the rate constants with bulk solvent properties is compared. The best of the ten equations involves the polarizability and dipole moment of the solvent as follows. log krel = 1.207 (no²-1/no²+2) + 3.99 μ + 0.003 -3 The rate constants for TBF decomposition in other non-hydroxylic solvents are calculated by the empirical equations and are compared with values previously reported. The average deviation of the log k is 0.22. The rate constants for the reaction of methyl iodide with triethylamine are calculated from solvent properties and the values compared to literature values. In this case the average deviation of the log k is 0.31. / Science, Faculty of / Chemistry, Department of / Graduate

The mechanism of permanganate oxidation of fluoral hydrate and its analogue, substituted with deuterium at position-1, has been extensively investigated throughout the pH region 0.7 to 14 and a successful study was made of the behaviour of permanganate in the sulfuric acid region from pH 0.7 to 46.3% H₂SO₄. Compared with 2,2,2-trifluoroethanol and other substituted ethanols which ionise in the pH region, fluoral hydrate is unique since it has two acidic hydrogens, both of which can ionise. The pK[subscript a] for the first ionisation process has been determined to be 10.1. From the kinetic data as well as other supporting evidence, at least four different reaction paths can be distinguished for the permanganate oxidation of fluoral hydrate: (i) Reaction of the di-anion of fluoral hydrate, (ii) Reaction of the mono-anion, (iii) Reaction of the unionised fluoral hydrate with permanganate anion, and (iv) Tentatively proposed reaction of the unionised fluoral hydrate with permanganic acid. The deuterium isotope effects range from k[subscript H]/k[subscript D] = 5 for the oxidation of the di-anion, k[subscript H]/k[subscript D] = 10 for the mono-anion reaction, k[subscript H]/k[subscript D] = 4 for the neutral molecule reaction and k[subscript H]/k[subscript D] = 6 for the permanganic acid oxidation of unionised fluoral hydrate in strong acid. Activation parameters and a positive salt effect show that the transition state formation involves a reaction of similarly charged species; proton tunneling is considered unlikely on the basis of a temperature study. The rate determining step is most consistent with a hydride ion transfer to the permanganate ion. In connexion with the above study, 2,2,2-trifluoroethanol, 1,1,1;3,3,3-hexafluoropropanol-2 and the corresponding 2-d analogue have been examined in somewhat lesser detail. An isotope effect k[subscript H]/k[subscript D] = 20 has been observed for the oxidation of 1,1,1;3,3,3-hexafluoropropanol-2. The pK[subscript a] of permanganic acid has been determined in sulfuric acid by a spectrophotometry method, using two different methods of calculation; pK[subscript a] = -5.1. Formic acid has been oxidised by permanganate in the region 25 to 72 % H₂SO₄ and the reaction in the region from 25 to about 40 % H₂SO₄ is interpreted as the oxidation of the unionised formic acid by permanganic acid. An isotope effect of about 7 is observed in the very strongly acidic region (72 % H₂SO₄), which decreases upon going to 25 % H₂SO₄. Certain 4,4'-disubstituted benzhydrols were oxidised by permanganate in 0.1 M sodium hydroxide, however solubility difficulties prevented any extensive studies. [ ... ] / Science, Faculty of / Chemistry, Department of / Graduate

Kinetics of the Dissolution of Copper in Aqueous Aliphatic Amines. An investigation was made of the dissolution of copper metal in aqueous solutions of methyl, ethyl and n-butyl amine and ammonia, as well as in solutions of their aminium and ammonium ions, under oxygen pressure. Study of the kinetics of the dissolution was carried out over a wide range of concentrations. It was observed that there are two regions of oxygen pressure dependency of the rate. The range of oxygen pressure, where rate is independent of oxygen pressure, was investigated in detail. The rate process has been established to obey the relation R = [formula omitted] [k₂(A) + k₃ (AH⁻⁺)] for all the systems studied. A mechanism for the dissolution reaction has been proposed. Catalytic Reduction of Nickel Ion by Molecular Hydrogen. The rate of precipitation of nickel from salt solution by molecular hydrogen in the presence of catalyst has been investigated over a wide range of concentrations. The variables studied are concentration of nickel, hydrogen pressure, amount of catalyst, concentration of- hydrogen ion and temperature. The rate of reduction is found to obey an equation of the form: [formula omitted] = -k₁[S][PH₂]½[Ni⁺⁺] + k₂[S][H⁺] The activation energy is found to be 25±2 kcal/mol. The equilibrium constant k for the reaction Ni⁺⁺ H2 Ni° + H₂ ⇌ Nº + 2 H⁺ is found to be 4.65 x 10⁻⁶ atm⁻¹ at 140°C. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Kinetics of steam gasification of both delayed and fluid cokes, byproducts from thermal cracking processes of Athabasca bitumen, have been studied in laboratory-size stirred and fixed bed reactors. The hydrogen sulphide in the product gas was captured in-situ using calcined dolomite and limestones as acceptors. Experiments were carried out at atmospheric pressure and at temperatures between 800°C and 930°C. The coke particle size ranged from 0.1 to 3.5 mm, and the steam partial pressure was varied from 15.15 to 60.6 kPa. The carbon and sulphur conversions were computed from the knowledge of gas compositions and flowrates and the gasification kinetics of both species established. The effects of sorbent type, particle size, calcination conditions, and Ca/S molar ratios on the extent of sulphur capture during gasification were examined in separate series of experiments. Scanning electron microscopy, surface area analysis, and mercury porosimetry were employed to relate physical structure changes in the solids to experimental kinetic data. The rate of gasification for the delayed coke was generally higher than that for the fluid coke, and both cokes were almost unreactive to steam gasification at temperatures below 800°C. Increased reaction temperatures or reduced particle sizes increased both carbon as well as sulphur conversion. The carbon conversion rates were found to go through maxima as the time of reaction and extent of conversion increased. As the reaction proceeded the surface area of the coke increased to a maximum of about five times its initial value and thenfell off sharply. The extent of carbon conversion alone dictated the specific surface area irrespective of temperature, particle size and steam partial pressure. Both calcined dolomite and calcined limestone were found to be effective in removing sulphur from the product gas. Sorbents possessing a larger specific area or smaller grain size had higher capacity to accept sulphur. At a Ca/S molar ratio of 2.0, the overall sulphur removal was approximately 90% for the first 3 hrs and the H₂S concentration in the produced gas was reduced to about 200 ppm from nearly 1250 ppm. The rate of sorbent conversion from CaO to CaS decreased monotonically with time. Three available kinetic models for gasification - the Random Capillary Model, the Random Pore Model and the Modified Volumetric Model, were tested with the experimental gasification data. Although reasonable fits were obtained for Xc-t results, the sharp drop in rate at high conversion could not be adequately modelled. Rate constants were established for the initial stage of reaction only. The Grain model and Continuous reaction models were tested with the experimental sulphidation results. The sulphidation process was controlled by chemical reaction at low sorbent conversion, and subsequently by diffusion through the product layer at higher conversions. The reaction rate constant and the effective diffusivity were accordingly established as functions of temperature. Values compared favourably with results of sulphidation kinetics done without simultaneous gasification reported in the literature. The results suggest that the gasification process and the sulphur capture process, which occur together in gasifiers with sorbent injection, can be treated independently. Indexing terms: Gasification, Carbon Conversion, Sulphur Conversion, Sulphur Removal, Calcine, Limestone, Dolomite, Hydrogen Sulphide, Sulphidation. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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