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The importance of alkyl methacrylates has been firmly established within the chemical industry. For example, free radical polymers, which contain the methacrylate backbone are more rigid than acrylate polymers. Several methods have been reported for the production of alkyl methacrylates. The aim of this project is focused on isolating a phase specific iron phosphate catalyst and thereafter testing its efficacy in oxidative reactions to form ethyl methacrylate in a one step process in the gas phase using a fixed bed continuous flow reactor. The catalyst was characterized by using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Brunauer-Emmett-Teller (BET) surface area measurements, Attenuated Total Reflection-Infrared (ATR-IR) Spectroscopy, Scanning Electron Microscopy (SEM), Temperature Programmed Reduction (TPR), Temperature Programmed Oxidation (TPO), Energy Dispersive X-ray (EDX) determination, Temperature Programmed Desorption (TPD), Room Temperature X-ray Diffraction (XRD), In situ X-ray Diffraction (In situ XRD), Thermogravimetric/Differential Thermal Analysis (TGA/DTA), Transmission Electron Microscopy (TEM), Mössbauer Spectroscopy and Raman Spectroscopy. A further venture included employing certain of the above techniques to characterize the cesium promoted iron phosphate catalyst as well as the spent catalysts. The catalytic activity of the iron phosphate based catalyst synthesized was investigated for the oxidative dehydrogenation (ODH) of ethyl isobutyrate (EIB) to ethyl methacrylate (EMA). Reaction conditions which were considered included variation in the contact time, co-feeding water at varying contact times, co-feeding ethanol at varying ratios, as well as co-feeding both ethanol and water and catalyst lifetime and regeneration studies. The cesium promoted iron phosphate catalyst was tested at optimal reaction conditions. The findings of the investigation showed that the tridymite-like FePO4 phase was the most suitable precursor to allow for the formation of the active α-phase during catalytic testing. It was found that the catalyst performed optimally at a contact time of 0.8 seconds and the beneficial effect of co-feeding water and ethanol primarily on conversion and selectivity towards EMA respectively, was demonstrated. Optimal results were obtained at a EIB:EtOH ratio of 1:5 with a conversion of 57 % and a yield of 34 mol %. The lifetime and regeneration studies showed that water had a significant effect on the regeneration of the catalyst after a specific time on stream and a shorter time on stream (i.e. 25 hours) prior to regeneration, minimized rapid deactivation of the catalyst. The characterization results obtained for the spent catalysts showed that under the reaction conditions considered with respect to co-feeds, the active α-phase and the Fe2P2O7 phase dominated. The cesium promoted iron phosphate catalyst was synthesized to favour stabilization of the tridymite-like structure. The results showed that a mixture of phases was observed for the synthesized promoted catalysts and there was an increase in EIB conversion as well as EMA selectivity with a decrease in cesium loading. However, the promoted catalyst with the lowest cesium loading (Cs/Fe = 0.10), showed a lower selectivity towards EMA relative to the unpromoted iron phosphate catalyst. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

Dimethyl ether (DME), as a solution to environmental pollution and diminishing energy supplies, can be synthesized more efficiently, compared to conventional methods, using a catalytic distillation column for methanol dehydration to DME over an active and selective catalyst. In current work, using an autoclave batch reactor, a variety of commercial catalysts are investigated to find a proper catalyst for this reaction at 110-135 C and 900 kPa. Among the -Alumina, Zeolites (HY, HZSM-5 and HM) and ion exchange resins (Amberlyst 15, Amberlyst 35, Amberlyst 36 and Amberlyst 70), Amberlyst 35 and 36 demonstrate good activity for the studied reaction at the desired temperature and pressure. Then, the kinetics of the reaction over Amberlyst 35 is determined. The experimental data are described well by Langmuir-Hinshelwood kinetic expression, for which the surface reaction is the rate determining step. The calculated apparent activation energy for this study is 98 kJ/mol. / Chemical Engineering

Thesis--Harvard University. / Bibliography: leaves 175-183.

As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals inhibited the production of polycyclic aromatic hydrocarbons. At the same time, the addition of DME gave rise to the increase of the flame temperatures, which favored the production of OH radicals. The incremental concentration of OH radicals promoted the oxidation rate of soot particles. Additionally, soot samples from flames with higher DME mixing ratios showed higher O/C, H/C mass ratios and thus better oxidation characteristics. In summary, the addition of DME reduces soot emission in two ways: on the one hand, it inhibits soot nucleation and mass/size growth, then the production of soot particles decreases; on the other hand, it promotes soot oxidation process by increasing the concentration of OH radicals and improving the oxidation behavior of the soot particles, then more particles are oxidized. Both of them are responsible for the reduction of soot emissions at the presence of DME.

<p> The thermolysis of 2-diphenylmethylenehydrazono-5,5-dimethyl-Δ^3-1,3,4-oxadiazoline in vacuum and in chlorobenzene was studied. In both cases a stable 1-(diphenylmethylene)-4, 4-dimethyl-3-oxo-1,2-diazetidinium inner salt was obtained as the major product. The corresponding imino-oxirane, an isomer of the diazetidinium inner salt, is believed to be a precursor of the above product. Thermolysis of the same oxadiazoline in methanol gave benzophenone methyl carbazate and methyl isopropyl ether, probably involving the initial formation of an isocyanate as an intermediate.</p> / Thesis / Master of Science (MSc)

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