Molybdates and tungstates belonging to the scheelite family constitute an important class of materials, which have advantages as a relatively low cost and being non-polluting. Barium molybdate (BaMoO4), barium tungstate (BaWO4), calcium molybdate (CaMoO4) and calcium tungstate (CaWO4) have been extensively studied due their photoluminescent properties, besides that they also present catalysis and photocatalysis applications. However, to the best of our knowledge there are no structural characterizations of BaMoO4, BaWO4 and CaMoO4 by x-ray absorption spectroscopy (XAS) in the literature. In this work, powders of these 4 compounds were prepared by microwave-assisted hydrothermal (MAH) method and polymeric precursor method (PPM) and their structural properties were characterized by X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. The morphology and particle size of these crystalline powders were observed by field emission scanning electron microscopy (FE-SEM). Furthermore, BaMoO4, BaWO4 and CaWO4 were employed as solid catalysts towards gas phase toluene oxidation reactions and their optical properties were investigated by ultraviolet visible (UV-Vis) absorption and photoluminescence (PL) measurements. XRD patterns confirm the phase purity of materials from both preparation methods and reveal a preferential growth when the powders are prepared by MAH due polymeric agents and processing using microwave, which was confirmed by FE-SEM. XANES and EXAFS results show that the preparation method did not introduce high disorders into the structure, however the H2 Temperature-Programmed Reduction (H2-TPR) measurements indicated that the catalyst reducibility is affected by the preparation method of the samples. PL emissions were attributed to the charge-transfer transitions within the [WO4]2- and [MoO4]2- complexes. / Os óxidos molibdatos e tungstatos, pertencentes a família das scheelitas, constituem urna importante classe de materiais que apresentam a vantagem de possuem relativo baixo custo e não serem poluentes. Molibdato de bário (BaMoO4), tungstato de bário (BaWO4), molibdato de cálcio (CaMoO4) e o tungstato de cálcio (CaWO4) tern sido extensivamente estudados devido as suas propriedades fotoluminescentes, além de apresentarem aplicações em catálise e fotocatálise. No entanto, não foi encontrada na literatura caracterizações estruturais de BaMoO4, BaWO4 e CaMoO4 por espectroscopia de absorção de raios X (XAS). Neste trabalho, partículas destes quatro compostos foram preparados pelo método hidrotermal assistido por micro-ondas (MAH) e método dos precursores poliméricos (PPM). Suas propriedades estruturais foram caracterizadas por difração de raios X (XRD) e espectroscopia de absorção de raios X na região XANES (do inglês X-Ray Absorption Near Edge Structure) e região EXAFS (do inglês Extended X-Ray Absorption Fine Structure). A morfologia e o tamanho de partícula desses pós cristalinos foram observados por microscopia eletrônica de varredura por emissão de campo (FE-SEM). Além disso, BaMoO4, BaWO4 e CaWO4 foram empregados como catalisadores sólidos para as reações de oxidação de tolueno em fase gasosa e as suas propriedades ópticas foram investigadas por medidas de absorção no ultravioleta/visível (UV-Vis) e fotoluminescência (PL). Os padrões XRD confirmam a pureza de fase dos materiais obtidos em ambos os métodos de preparação e revelam um crescimento preferencial dos pós preparados por MAH devido aos agentes poliméricos e ao processamento usando micro-ondas, esse crescimento foi confirmado pelas micrografias obtidas por FE-SEM. Os resultados de XANES e EXAFS mostram que o método de preparação não introduz desordens elevadas na estrutura, no entanto, as medidas de redução à temperatura programada (H2-TPR) indicaram que a redução do catalisador e afetada pelo método de preparação das amostras. As emissões de PL foram atribuídas às transições de transferência de carga dentro dos complexos [WO4]2- e [MoO4]2-.

The tropospheric reactions of toluene, acting as a model VOC, are investigated using an electron bombardment-matrix isolation system coupled with Fourier transform infrared spectroscopy. Initial experiments to produce the hydroxyl radicals used to initiate the toluene reactions via electron bombardment of water-argon mixtures are performed. The effects of electron current, water concentration, and gas flow rate are investigated. A more efficient method of initiating the toluene reactions, by directly creating benzyl radicals through electron bombardment of toluene is then investigated, and the effects of toluene concentration and electron current on the production of the benzyl radicals is quantified. Benzyl radicals are successfully produced, and identified via FT-IR. The next step is the formation of benzylperoxy radicals, via electron bombardment of toluene-oxygen-argon gas mixtures. Experiments are performed using increasing concentrations of toluene and oxygen, in an attempt to observe the benzylperoxy radical. Two new absorptions are observed in the infrared spectra and are tentatively identified as due to the peroxy group on the benzylperoxy radical. Computational work is also performed to confirm that benzylperoxy radicals can in fact be produced from benzyl radicals and oxygen. The vibrational frequencies of the benzylperoxy radical are also calculated, and used to confirm the possibility that the new absorptions seen in the infrared spectra could in fact be due to benzylperoxy radicals. The overall results from this work demonstrate that it is likely to be possible to use electron bombardment-matrix isolation systems to investigate tropospheric reactions of volatile organics, and that further experiments could be enhanced by structural modifications to the system. / Thesis (Master, Chemistry) -- Queen's University, 2013-11-26 15:57:59.4

by Chiu Peng Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 82-87). / Abstracts in English and Chinese. / Table of Contents --- p.i / Acknowledgements --- p.iv / Abbreviations --- p.v / Abstract --- p.vi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Definition of Carbon Hydrogen Bond Activation (CHA) by Transition Metal Comple --- p.1 x / Chapter 1.2 --- The Importance of Alkane CHA and its Potential Use --- p.1 / Chapter 1.3 --- Difficulties in Alkane CHA --- p.3 / Chapter 1.4 --- The Use of Transition Metal Complexes in CHA Reactions --- p.4 / Chapter 1.5 --- Classification of CHA Reactions --- p.6 / Chapter 1.6 --- The Importance of Toluene and Benzene CHA --- p.11 / Chapter 1.7 --- Difficulties and Challenges in CHA of Toluene --- p.11 / Chapter 1.8 --- Selectivity Control and Rate Promotion --- p.12 / Chapter 1.9 --- Structural Features of Rhodium Porphyrins --- p.17 / Chapter 1.10 --- CHA by Rhodium Porphyrins --- p.19 / Chapter 1.11 --- Objective of Work --- p.21 / Chapter Chapter 2 --- CHA Reactions of Toluenes by Rhodium Porphyrin Chlorides / Chapter 2.1 --- Synthesis of Rhodium Porphyrin Chlorides --- p.22 / Chapter 2.2 --- Temperature Effects of CHA in Toluene --- p.22 / Chapter 2.3 --- Inter and Intra Molecular Exchange of Alkyl Rhodium Porphyrin Complexes --- p.24 / Chapter 2.4 --- Electronic Effect of Rhodium Porphyrin Chlorides --- p.24 / Chapter 2.5 --- Electronic Effect of Toluene Towards CHA --- p.25 / Chapter 2.6 --- X-Ray Data --- p.26 / Chapter 2.7 --- Mechanistic Studies --- p.30 / Chapter 2.8 --- Ligand and Base Effects --- p.32 / Chapter 2.9 --- Optimization of Reaction Conditions --- p.35 / Chapter 2.10 --- Electronic Effect of Toluenes --- p.36 / Chapter 2.11 --- Concentraction Effects of Toluenes (Reactions in Benzene) --- p.38 / Chapter 2.12 --- Porphyrin Effects in CHA of Toluene --- p.39 / Chapter 2.13 --- Mechanistic Studies --- p.40 / Chapter 2.14 --- Conclusion --- p.42 / Chapter 2.15 --- Reaction between Rh(ttp)Me and Toluenes --- p.42 / Chapter 2.16 --- Selective Benzylic CHA --- p.42 / Chapter 2.17 --- Isotope Effect --- p.44 / Chapter 2.18 --- Discussion --- p.44 / Chapter 2.19 --- Exploratory Studies of Other Base-Promoted Reactions --- p.45 / Chapter 2.20 --- Benzylic CHA and Aromatic Carbon Halogen Bond Activation (CXA) Reactions --- p.45 / Chapter 2.21 --- Base-Enhanced Aromatic CXA --- p.48 / Chapter 2.22 --- X-Ray Data --- p.49 / Chapter 2.23 --- Base-Enhanced Benzylic Carbon Carbon Bond Activation (CCA) Reactions --- p.51 / Chapter 2.24 --- Summary --- p.52 / Chapter Chapter 3 --- Experimental Sections --- p.53 / References --- p.82 / Appendix I Crystal Data and Processing Parameters --- p.88 / Appendix II List of Spectra --- p.123 / Spectra --- p.125

Benzene, toluene, and xylene are three basic raw materials for the production of most aromatic derivatives such as polyesters, plastics and detergents. Xylenes (p-, m- and o-) have the greatest market demand with an increasing annual rate of 6%. Owing to the availability of surplus toluene and low value of C9 aromatics, the transalkylation process is aimed at the production of more valued products, such as xylenes. Catalyst deactivation is a key challenge in transalkylation process. Using industrially relevant operating parameters, the transalkylation of 1,2,4-trimethylbenzene (TMB) with toluene was studied. The effect of zeolite structure and acidity, increased reaction pressure and temperature, and very low levels of platinum (Pt) impregnation has been investigated over both H-form and Pt-loaded zeolites: Beta, Mordenite (MOR), and Y. A fixed bed reactor was used at WHSV of 5 h-1, 400 oC, and a 50:50 wt. % toluene:TMB ratio with the order of activity after 50 h time-on-stream (TOS) of Y > Beta >> MOR at 1 bar. At elevated pressure (10 bar), all catalysts showed better performance with significant improvement in MOR as pore blockage was reduced and the order of activity was Beta > MOR > Y. With varying the Si/Al ratio for zeolites Beta (Si/Al = 12.5, 75 and 150) and Y (Si/Al = 2.6, 6, 15 and 30), the highest stability and xylenes yield were achieved over zeolite Beta with lowest Si/Al ratio at 41 wt. % conversion and 25 wt. % xylenes yield. In contrast, zeolites Y with Si/Al ratio of 2.6 showed the highest deactivation rate, whereas over Y zeolites with Si/Al = 6-30, the conversion was between 25-30 wt. % and xylenes yield around 11 wt. % after 50 h TOS. Incorporation of Pt (0.08 wt. %) further improved the activity of all catalysts with the highest conversion after 50 h TOS over Beta (62 wt. %) where Beta and MOR yielded similar levels of xylenes (40 wt. %). All catalysts were further optimized by reducing Pt levels whilst maintaining the desired stability and highest xylenes yield. In order to further develop a cost-effective and eco-friendly catalyst, the addition of alumina binder to Pt-Beta and the possibility of simplified regeneration of Beta/Pt-Beta catalyst were investigated. Firstly, the alumina binder reduced the conversion and xylenes yield, however, this reduction was small up to 40 wt. % added alumina binder (where xylenes yield only dropped to 35 wt. %). Secondly, the regeneration process was carried out using H2 only and up to four cycles (30 h TOS per cycle). The Pt-Beta catalyst found to be stable and the activity was fully restored by a hydrogenation process at 500 oC. However, the activity of Beta dropped gradually after each cycle suggesting that the H2 alone at 500 oC was insufficient in removing coke precursors. The drop in activity was attributed to the disappearance of Brà ̧nsted acid sites over the spent Beta catalyst due to the growth of coke molecules trapped in cavities leading to highly polyaromatic molecules blocking those active sites.

Polymers of various types are added to crude oils and oil products to prevent wax deposition, break water-in-oil emulsions, reduce drag in pipelines and to stabilize asphaltenes. In mixtures where a polymer does not adsorb on colloids, two stable liquid phases can arise due to depletion flocculation. Asphaltenes in heavy oils and toluene mixtures form sterically stabilized colloidal particles. In this work, the addition of a non-adsorbing polymer (polystyrene) to C5 Maya asphaltene + toluene mixtures was investigated experimentally and theoretically. As concentrated asphaltene + toluene mixtures are opaque to visible light, phase volumes and compositions were detected using ultrasound. The sensors comprised two commercial 64 element phased-array acoustic probes. The operation of the view cell, and kinetic and equilibrium data processing procedures were validated using mixtures of methanol + alkanes. Acoustic speed and attenuation profiles were found to provide independent measures of phase separation. At equilibrium, acoustic speed profiles are uniform in each phase with a step change at the interface. Acoustic wave attenuation profiles exhibit a sharp peak/spike at liquid-liquid interfaces. Mixtures of asphaltenes + polystyrene + toluene are shown to exhibit liquid-liquid phase behavior over broad ranges of composition. This is the first report of liquid-liquid phase behavior for such mixtures. One phase is asphaltene rich and the other phase is polystyrene rich. Liquid-liquid critical points were also identified along the liquid-liquid/liquid phase boundary for mixtures with two mean molar masses of polystyrene. Compositions of co-existing phases were computed using phase volume variations along dilution lines, acoustic speed data and a mass balance model. A parameter was introduced to improve the agreement between calculated and experimental speeds of sound. The results of the model indicate that more than half of the asphaltenes, by volume, participate in the depletion flocculation process. Phase compositions were measured independently using UV-visible spectrophotometry. The nominal size of asphaltene colloidal particles participating in the phase separation mechanism was estimated by comparing calculated phase boundaries with the experimental phase diagram. The estimated size of asphaltene colloidal particles is in agreement with the expected size of asphaltenes in toluene mixtures obtained exogenously. / Chemical and Materials Engineering

This study was to investigate the effect on conversion, deactivation of long-term, selectivity of product, and kinetics in deep oxidation of toluene over copper catalyst. The copper catalyst is supported on honeycomb of ceramic monolith (400 cell/inch2). The operation parameters in heterogeneous reactor were performed as follows: 1000 ppm initial concentration of toluene, temperature of reaction in ranging from 200 ¢J to 400 ¢J, 15 % of oxygen concentration, and 4000 hr-1 of space velocity. In the selection of catalyst, we decided to use 20% Cu catalyst for its high conversion, high selectivity and low cost in oxidation of toluene. The conversion of toluene in catalytic reaction was increased with the increasing both of reaction temperature and influent concentration of oxygen, and decreased with the going up of initial concentration of toluene and of space velocity. In the catalyst stability of long-term test, Cu catalysts had a good stability after 7 days reaction in heterogeneous reactor. The tests such as BET, SEM and EA were also determined to verify the stability from surface of catalyst. The kinetics of heterogeneous reactor over Cu catalyst supported on ceramic honeycomb in oxidation of toluene was found that a pseudo-first order could be described by both Power-rate law and Mars-Van Krevelen model. The apparent reaction order and activated energy were obtained in this work.

This experiment is composed of three parts: Gas sampling and analysis by Regenerative Thermal Oxidizer in the factory ¡Afabrication and screening of catalyst, and a discussion about efficiency of Catalytic Oxidation toluene by varied factors. Regarding gas sampling in the factory, we found that the transformation rate of VOCs by Regenerative Thermal Oxidizer(RTO) at operation temperature 982¢J into tolueneis 94.7%, into 2-butanone is 96.5%, into isopropyl alcohol is 95%. Among the three, toluene showed the lowest transformation rate. Regarding catalyst sampling and research, we found that metal catalyst by immersion method(immersion method) ( weight ratio of Cu:Co¡BCu¡GMn and Mn¡GCo is 1¡G1¡BPure Cu¡BPure Co and Pure Mn)and metal load(metal /molecular sieve) is 5%¡B10%. Among the twelve metal catalysts, we figured out 10% metal C-Co(1:1) is the best catalyst concerning transformation rate. Regarding the operation factors, the experiment showed¡G(1)the more the concentration of toluene¡Athe more the temporary inhibition¡Aand therefore, the transformation rate went down¡A(2)The more the speed of inhalation¡Athe time the air stayed still decreased, and a obvious decrease of transformation rate can be seen(3)the increase of oxygen concentration showed a positive effect toward transformation rate.(4)When at a higher reaction temperature, for the above mentioned three factors, the influence upon transformation rate became less. In addition, for the cost evaluation, the 10% metal Cu-Co(weight rate 1:1) catalyst we chose in our experiment is 92.79 Taiwanese Dollars for one batch of 120g and the catalyst per gram is 0.77 Taiwanese Dollars.

No description available.

ABSTRACT PELCHEM, the chemical division of NECSA, produces the fluorocarbon hexafluoropropylene (HFP) onsite. In 2005 PELCHEM initiated research into the wet oxidation of HFP to produce the higher value fluorocarbon hexafluoropropylene oxide (HFPO). Although successful in the conversion of HFP to HFPO, the product stream contained both the product and the unreacted HFP. As a result, PELCHEM contracted the Thermodynamics Research Unit at the University of KwaZulu-Natal to investigate the separation of HFP and HFPO. A solvent selection procedure was used to identifY potential solvents and an initial list of two hundred and seven candidate solvents compiled. Utilising the UNIFAC group contribution method, the initial list was narrowed down to thirty solvents using the criterion of selectivity at infinite dilution. Through the comparison of specific solvent properties such as recoverability, safety, environmental factors and economic considerations, a final list of ten solvents was generated. The list of ten solvents was proposed to PELCHEM who identified four solvents for further studies. The work involving the two solvents, toluene and hexafluoroethane (RI 16), is presented in this dissertation. The solvent toluene has been previously used by the du Pont company for the separation of HFP and HFPO, while R116 is a novel solvent for this application. The solvent selection procedure was performed in collaboration with a member of the Thermodynamics Research Unit, and the work on the remaining two solvents is presented in the dissertation of (Nelson 2008). Experimental binary high pressure vapour liquid equilibrium data were measured for the HFP + toluene, HFPO + toluene, R116 + HFP, and R116 + HFPO systems at two temperatures: 273.15 and 3 13.15 K. Pure component vapour pressure data for HFPO in the temperature range of 271.90 to 318.20 K were also measured. The HPVLE measurements were performed at the Thermodynamics Energy and Phase Equilibria laboratories at Ecoles des Mines de Paris using two experimental techniques and equipment. The binary systems involving toluene were measured on a static synthetic Pressure Volume Temperature apparatus equipped with a variable volume cell. The binary systems involving RI16 were measured on a static analytic apparatus equipped with a Rapid On-line Sampler Injector. None of the systems measured for this project have been reported in the literature. The four binary systems and the pure component vapour pressure measurements thus constitute new data sets. All experimental data were modelled via the direct method using the computer software Thermopack. Three model combinations were used to represent the data: the Peng-Robinson equation of state with the Wong-Sandler mixing rules, the Peng-Robinson equation of state with the Modified-Huron-Vidal first order mixing rules, and the Soave-Redlich-Kwong equation of state with the Wong-Sandler mixing rules. The Mathias-Copeman alpha function was used in conjunction with the equation of state models, and the NRTL activity coefficient model was incorporated into the mixing rules. Due to time constraints, experimental data for the binary system HFP + HFPO were not measured. Data for this system was predicted at two temperatures, 273.15 and 313.15 K, via the PSRK-UNIFAC method. The critical line for the supercritical systems R116 + HFP and R116 + HFPO were calculated in Thermopack. PELCHEM required a commercial grade HFPO product stream of purity greater than 99 % (mole), and a purified HFP product stream of purity greater than 95 % for the recycle and conversion of HFP into HFPO. Using the regressed experimental high pressure vapour liquid equilibrium data, two preliminary separation processes were designed in Aspen Plus to achieve these objectives. The first scheme involved toluene and utilised the process of extractive distillation with toluene introduced as a liquid solvent. The toluene bonded to the HFP and was removed as a bottoms product which allowed a purified HFPO stream to be recovered as a distillate. The second scheme involved RI16 and utilised the process of gas stripping, with a liquid mixture of HFP and HFPO contacted with a gaseous stream of R116. The R116 removed the HFP from the liquid mixture, resulting in a purified HFPO stream. The toluene process resulted in an overall HFPO product recovery of 98.46 % and HFPO product purity of99.88 % (mole). The RI16 process resulted in an overall HFPO product recovery of96.57 % and HFPO product purity of99.71 %. For the component HFP, the toluene process resulted in an overall HFP product recovery of 99.42 % and product purity of96.41 %. The RI16 process resulted in an overall product recovery of99.36 % and product purity of93.45 %. From a comparison of the preliminary design of the separation processes on the basis of patent issues, performance, and other miscellaneous factors, it was concluded that the RI16 process compared favourably to the process involving the solvent toluene. The preliminary process designs were presented to PELCHEM in 2007, and pending further experimental work PELCHEM plans to patent the RI16 separation process. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

Thesis (Ph.D.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 135 pages. Includes Vita. Includes bibliographical references.