The first part of this work reports on the investigation of the formation constant of molecular silver chloride using ion exchange techniques. In order to determine the formation constant, it was necessary to develop a method of rinsing the sorbed molecular silver chloride from the resin. It was found that desorption with nitrobenzene would remove the sorbed molecular species. However, the formation constant was not calculated since the nitrobenzene used contained hydrogen ion and chloride ion which removed silver ion as well as the molecular species. In the study of the formation of silver sulfide by the reaction between the thioacetamide and silver ion, it was found that the order of the reaction with respect to silver ion was zero at pH values 0.38 and 1.24. The zero order rate constants at these pH values are 1.66 x 10^-6 moles liters^-1 sec^-1 and 9.16 x 10^-6 moles liters^-1 sec^-1 respectively. Qualitative experiments indicate that there is a change in mechanism at a pH value of approximately two.

The independent interconversion of alpha-N-carbobenzoxy-D-glucosaminide to the beta- form, and vice versa, suggests that the proper treatment of the rate data must involve a system of opposing reactions. It is evident from the data cited in the preceding chapter that such opposing rates must necessarily involve the HCl which is included in the reaction mixture. Thus, as the first approach to the analyzed data, it is reasonable to suppose that the rate law for opposing second-order rates will apply. However, it is also apparent from the data that the concentration of HCl used in all this work exceeds the glycoside concentration by a factor of about one hundred times. Therefore, the postulated system of opposing second order processes may be reduced to a system of opposing [pseudo-first-order processes. Such a system can be formulate as follows: [see PDF]

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Gas-phase reaction kinetics is at the center of the evolution of reacting systems. Many important reactions in the gas phase proceed through rovibrationally excited complexes AB* that are formed either from the association of two particles A + B or from the activation of thermalized species AB by collisions between AB and inert colliders. The fate of these rovibrationally excited complexes is governed by the competition among energy-transferring collisions, unimolecular decomposition, and bimolecular reactions -- yielding a strong dependence of all emergent rate constants on temperature, pressure, and composition of the surrounding mixture. In nearly all realistic environments critical to combustion and planetary atmospheres, multiple species are present in significant quantities and thus contribute to the evolution of the rovibrationally excited complexes. A substantial fraction of these species is inert in the sense that they merely participate in energy-transferring collisions, and a portion of them are instead reactive, which participate in reactive collisions and induce reactions with the rovibrationally excited complexes rather than merely transferring energy. Most of the inert species have distinct collisional energy transfer characteristics and thus contribute differently to the energy-transferring collisions -- making the multi-component pressure dependence in mixtures different from the pressure dependence in the constituent components when pure. Accounting for such “mixture effects,” in practice, one employs a “mixture rule” to interpolate kinetic data in mixtures from individual pure bath gas components. While mixture effects for reactions proceeding through a single potential well and a single reaction channel have been extensively investigated, mixture effects and mixture rules for multi-well and/or multi-channel reactions are significantly less characterized despite their ubiquitousness in gas-phase reaction systems. This work presents an investigation of and seeks reliable representations of bath gas mixture effects on multi-channel (both single-well and multi-well) reactions and their impacts on combustion predictions. The performance of different mixture rules for representing multi-component pressure dependence of rate constants for various systems is evaluated through comparisons against ab initio master equation calculations for the mixture. The comparisons revealed that the classic linear mixture rule, the most commonly applied mixture rule, yields substantial deviations (exceeding a factor of 50) for typical combustion mixtures. The comparisons, together with results from combustion simulations, suggest that recently proposed mixture rules based on the reduced pressure provide a considerably more accurate representation of mixture effects for various systems. These new mixture rules are therefore recommended for use in fundamental and applied chemical kinetics investigations. The importance of reactive collisions between the rovibrationally excited complexes AB*, formed from the association of A + B, and reactive colliders C was largely ignored historically. Recent studies have demonstrated that reactive collisions of AB* with C often occur on the same timescale as energy-transferring collisions. And these reactive collisions can induce non-Boltzmann kinetic sequences that proceed through AB* and propagate across multiple coupled potential energy surfaces. The non-Boltzmann kinetic sequences can be represented by the chemically termolecular reactions A + B + C → products in phenomenological kinetic models. While these non-Boltzmann kinetic sequences consume the same set of species as their equivalent thermal sequential pathways, they are kinetically and dynamically distinct and can have substantial impacts on the global reactivity in combustion and atmospheric systems beyond those imposed by thermal sequential pathways. Evaluating the kinetics of non-Boltzmann kinetic sequences requires that rovibrational excitation of reacting complexes from one potential energy surface be carried over to the following and appropriate treatments for the augmentation and dissipation of the energy distributions due to reactions. This work presents a theoretical and computational methodology that couples multiple master equations and derives rate constants for all emergent phenomenological reactions for non-Boltzmann kinetic sequences spanning across the coupled master equations. Results from implementing the methodology for a couple of systems demonstrate that reactive collisions can both increase the overall rate of conversion of reactants to products and alter the branching ratios among final products. Combustion simulations indicate that reactive collisions can have significant impacts on the overall system reactivity. Therefore, suitable rate laws and appropriate treatment are needed for the distinct effects of reactive collisions to be represented in phenomenological kinetic models.

A comparative study of the electro-oxidation of ethanol and methanol was carried out on a Pt/ceria composite electrode prepared by electro-deposition. Modification of the Pt electrode was realized by co-deposition from a 1.0 mM K₂PtCl₆ solution that also contained a 20 mM suspension of ceria. The electro-catalytic activities and stabilities of the Pt/ceria catalyst towards ethanol electro-oxidation reactions (EOR) and methanol electro-oxidation reactions (MOR) were investigated by potentiodynamic and potentiostatic methods in 0.5 M sulfuric acid and 1.0 M sodium hydroxide solutions at various concentrations of ethanol and methanol. The kinetics of ethanol and methanol on a Pt/ceria composite electrode were measured in 0.5 M sulfuric acid and 1.0 M sodium hydroxide solutions using a rotating disk electrode (RDE). Cyclic voltammetry was employed in temperatures ranging from 15 to 55°C to provide quantitative and qualitative information on the kinetics of alcohol oxidation. The temperature dependence of the electro-catalytic activities afforded the determination of apparent activation energies for ethanol and methanol oxidation.

Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et al. mechanism. The dilute mixtures were used to study the OH* emission profiles compared to those of the kinetics model. The model was in poor agreement with the experimental data especially at lower temperatures with an ignition delay difference of more than an order of magnitude. These ignition delay time data supplement the few existing data and are in relative agreement. The species profile comparison of OH* compared to the model also showed poor agreement, with the worst agreement at the highest temperatures. While the disagreements with ignition delay time and profile comparisons cannot be explained at this time, the data presented support other findings. The data provide additional information towards understanding this disagreement relative to syngas mixtures despite the relatively well known kinetics of the primary constituents Hydrogen and Carbon Monoxide.

Exhaust emissions in a vehicle has to flow through an exhaust aftertreatment in a diesel vehicle. In a diesel engine, the exhaust emissions are treated with Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR). Every engine produces a different kind of soot depending on the drive cycle. In this thesis, a study was made on the soot oxidation in DPF so as to reduce the net fuel consumption and hence optimising the engine.This project focuses on DPF, where the soot and ash are trapped on the walls of the filter when the emissions flow through the DPF. Over a period of time, the soot accumulates and causes the pressure inside the filter to increase. To reduce the backpressure due to soot accumulation, soot has to be removed from the filter which is done by a regeneration process in which soot is oxidized. To understand the soot oxidation in the DPF, we study the chemical kinetics of the soot.The soot reacts with NO2, O2, and N2 in a Thermogravimetric Analysis (TGA) instrument, in isothermal conditions. Two soot samples, SORT-1 and FORCED 360 were analyzed with TGA, the rate equations were derived from using Arrhenius type kinetics and the data was processed by MATLAB. The rate at which the soot is oxidized by NO2 and O2 for SORT-1 is higher than for FORCED 360. This trend is observed similarly when both the soot samples react with only O2. When soot oxidation reaction takes place with O2 and NO2 they require a lower temperature of 250 °C-400 °C than compared to samples reacting with only O2 with a temperature of 350 °C - 500 °C. To understand the conditions that affect soot oxidation, the concentration of oxygen was varied and it was found that at higher oxygen concentration the soot oxidized is almost constant. Then soot kinetics were analysed by finding the rate of the reaction, the order of the reaction, and finally the activation energy. The order of the reaction for FORCED 360 and SORT-1 vary and slope of the graph, logarithm of reaction constant vs logarithm of mass shows a non-linearity in the former due to the slower rate of the reaction in SORT-1 than in FORCED 360. The activation energy was found to be 39.3 kJ/mol for SORT-1 and FORCED 360 is 60.8 kJ/mol. / Avgasutsläpp i ett fordon måste strömma genom avgasefterbehandling i ett dieselfordon. I en dieselmotor behandlas avgasutsläppen med dieseloxidationskatalysator (DOC), dieselpartikelfilter (DPF) och selektiv katalytisk reduktion (SCR). Varje motor producerar olika typer av sot beroende på körcykeln. I denna avhandling gjordes en undersökning av sotoxidationen i DPF för att minska nettobränsleförbrukningen och därmed optimera motorn. Detta projekt fokuserar på DPF, där sot och aska fångas på filterväggarna när utsläppen flyter genom dieselpartikelfiltret. Under en tidsperiod ackumuleras sot och får trycket inuti filtret att öka. För att minska mottrycket på grund av sotansamling måste sot avlägsnas från filtret, vilket görs genom en regenereringsprocess där sot oxideras. För att förstå sotoxidationen i DPF studerar vi sotens kemiska kinetik. Sotet reagerar med NO2, O2 och N2 i ett instrument för termogravimetrisk analys (TGA) under isotermiska förhållanden. Två sotprover, SORT-1 och FORCED 360 analyserades med TGA, hastighetsekvationerna härleddes från användning av Arrhenius-typskinetik och data bearbetades av MATLAB. Den hastighet med vilken sot oxideras av NO2 och O2 för SORT-1 är högre än för FORCED 360. Denna trend observeras på liknande sätt när båda sotproverna reagerar med endast O2. När reaktion genom sotoxidation äger rum med O2 och NO2 kräver de en lägre temperatur på 250 ° C - 400 ° C än jämfört med prover som bara reagerar med O2 med en temperatur på 350 ° C - 500 ° C. För att förstå de förhållanden som påverkar sotoxidation varierades syrekoncentrationen och det visade sig att vid högre syrekoncentration var sotet oxiderat nästan konstant. Därefter analyserades sotkinetiken genom att hitta reaktionshastigheten, reaktionsordningen och slutligen aktiveringsenergin. Reaktionsordningen för FORCED 360 och SORT-1 varierar och lutningen i diagrammet, logaritmen för reaktionskonstanten mot logaritmen av massan visar en icke-linjäritet i den tidigare på grund av den långsammare reaktionshastigheten i SORT-1 än i FORCED 360. Aktiveringsenergin konstaterades vara 39,3 kJ / mol för SORT-1 och för FORCED 360, 60,8 kJ / mol.

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