Platinum (Pt) alloy nanoparticles are used as catalysts in electrochemical cells to reduce oxygen to water and to oxidize hydrogen; the overall reaction converts chemical energy into electrical energy. These nanocatalysts are deposited on a carbon substrate and their catalytic function takes place in acid medium. This harsh environment causes an undesired reaction, which is the dissolution of the metal atoms into the acid medium; thus affecting the catalyst life. This dissertation aims to investigate the dissolution mechanism of fuel cell cathode catalysts at the atomic level starting from the oxygen reaction intermediates on the cathode catalyst surface and propose guidelines to improve cathode catalysts durability based on our proposed mechanism. Density functional theory is employed to study various possible scenarios with the goals of understanding the mechanism of the metal atom dissolution process and establishing some guidelines that permit a rational design of catalysts with better stability against dissolution. A thermodynamic analysis of potential metal dissolution reactions in acid medium is presented first, using density functional theory calculations to explore the relative stabilities of transition metals in relation to that of Pt. The study is performed by comparing the change in reaction Gibbs free energies for different metals in a given dissolution reaction. Then, a series of density functional theory studies, tending to investigate the adsorbed atomic oxygen absorption process from cathode catalyst surface into its subsurface, includes: 1) the oxygen adsorption on various catalyst surfaces and oxygen absorption in subsurface sites to figure out the minimum energy pathway and energy barrier of on-surface oxygen migration and absorption into subsurface; 2) the oxygen coverage, the other oxygen reduction reaction intermediates, and water effects on the oxygen absorption process according to reaction pathways, energy barriers, and thermodynamic analysis; 3) the oxygen absorption process on several Pt-based alloys with various compositions and components to find out the best alloy to inhibit atomic oxygen absorption including both kinetic and thermodynamic analyses, and the effects of such alloyed species on the inhibition process.

The overall objective of this research was to develop and assess a new method, named remedial extraction and catalytic hydrodehalogenation (REACH), for removing and destroying soil contaminants. In particular, I considered hydrophobic halogenated organic compounds (HHOCs). In this research, I developed a closed-loop treatment process that catalytically destroys the contaminants of concern, and does not generate a secondary waste stream. Mixtures of water and ethanol appear to be good candidates for the extraction of 1,2,4,5-tetrachlorobenzne (TeCB) or pentachlorophenol (PCP) from contaminated soil. Palladium-catalyzed hydrodehalogenation (HDH) was applied for destroying TeCB or PCP in mixtures of water and ethanol in a batch mode. The experimental results are all consistent with a Langmuir-Hinshelwood model for heterogeneous catalysis. Major findings that can be interpreted within the Langmuir- Hinshelwood framework are as follows: the rate of HDH depends strongly on the solvent composition, increasing as the water fraction of the solvent increases; the kinetics of the HDH reaction are apparently first-order with respect to the concentration of TeCB in the solvent; and the HDH rate increases as the catalyst concentration in the reactor increases. Also, TeCB is converted rapidly and quantitatively to benzene, with only trace concentrations of 1,2,4-trichlorobenzene appearing as a reactive intermediate. PCP is transformed to phenol by sequential reductive dehalogenation to tetrachlorophenols, then to trichlorophenols, then to phenol. The degradation of PCP does not follow firstorder kinetics, probably because of competitive reactions of intermediate products that are generated during PCP degradation. Following the batch studies, the REACH technology was applied in continuous mode under baseline conditions for a span of 7 weeks to treat soils that had been synthetically contaminated by HHOCs in the laboratory. Extraction of TeCB and PCP from soils was almost completed within two days by a 50:50 mixture of water and ethanol. Higher reaction rates were observed for TeCB than for PCP. The activity of the catalyst was slowly lost as contaminant mass was removed from the soil. The deactivated catalyst was successfully regenerated with a dilute sodium hypochlorite solution. The results of this research suggest that REACH could be a viable technology for some contaminated soils.

Abstract The objective of this study is to compare the performance over copper oxide catalyst under nonselective catalytic reduction of nitric oxide with methane and selective catalytic reduction of nitric oxide with propane. The copper catalysts was prepared by impregnating the support Al2O3 with copper nitrate. In order to find the favorable kind and concentration of acid solution¡Awe conducted the modification of three acid solutions on the support Al2O3 in the same normal concentration in the first¡Aand followed by the test of various concentration of the most-favoured acid. The experiment operated condition was as follow¡G reaction temperature 623K-1023K¡AF/W¡×108000ml/hr.g¡Aoxygen concentration 2¢M¡ANOx inlet concentration 1000ppm. In view of the result of NSCR reactions with methane over Cu/£^-Al2O3 catalyst¡Athe conversion of De-NOx increased with the increasing loading of copper on Cu/£^-Al2O3¡Aand achieved a max. value when copper loading was 8¢Mwt.. The performance of De-NOx over the modified copper catalysts three different acid with the same normal concentraion¡Ashowed that the best reduction efficiency was with nitric acid modified¡Athen with¡Aand followed with acetic acid¡Aphosphoric acids. Through compared the conversion of De-NOx between non-modified Cu/£^-Al2O3 with modified Cu/£^-Al2O3¡Athere had the best efficiency in treating for NO conversion. It showed that the best efficiency in raising the conversion of NO over copper catalyst is modified with nitric acid¡Athere is not helpful on reduction efficiency of NO by modification with acetic and phosphatic acids. Nevertheless¡Athe higher concentration¡]N¡^ of nitric acid is¡Athe higher efficiency of De-NO is¡F For the SCR reactions with propane, when the inlet concentraion NO/C3H8 was 1¡Athere has better reductive activity. The trends for the NO conversion versus reaction temperature were similar for the same catalysts used. In general, the NO conversion was an increasing function of copper loading for these copper catalysts. The 8¢Mwt. Cu/£^-Al2O3 was found to enhance the NO conversion. The activity of acid-treated catalysts in nitric acid with 2¢MO2 present had the best NO conversion, while the same order was in NSCR reaction. Treating the supports with a higher concentration of acid would result in a higher activity for the copper catalyst, implying that acid treatment not only duces surface area to decrease on catalyst and enhance the reactivity, but also the presence of Cu+ and Cu2+ might be responsible for the reaction efficiency. no matter what the reactant is propane or methan , propane is better reactant to catalyst NO to N2.

none

The selective catalytic reduction (SCR) of nitric oxide (NO) with ammonia over vanadia-based (V2O5-WO3/TiO2) and pillared interlayer clay-based (V2O5/Ti-PILC) monolithic honeycomb catalysts using a laboratory laminar-flow reactor was investigated. The experiments used a number of gas compositions to simulate different combustion gases. A Fourier transform infrared (FTIR) spectrometer was used to determine the concentrations of the product species. The major products were nitric oxide (NO), ammonia (NH3), nitrous oxide (N2O), and nitrogen dioxide (NO2). The aim was to delineate the effect of various parameters including reaction temperature, oxygen concentration, NH3-to-NO ratio, space velocity, heating area, catalyst arrangement, and vanadium coating on the removal of nitric oxide. The investigation showed that the change of the parameters significantly affected the removals of NO and NH3 species, the residual NH3 concentration (or NH3 slip), the temperature of the maximum NO reduction, and the temperature of complete NH3 conversion. The reaction temperature was increased from the ambient temperature (25°C) to 450 °C. For both catalysts, high NO and NH3 removals were obtained in the presence of a small amount of oxygen, but no significant influence was observed from 0.1 to 3.0% O2. An increase in NH3-to-NO ratio increased NO reduction but decreased NH3 conversions. For V2O5-WO3/TiO2, the decrease of space velocity increased NO and NH3 removals and broadened the active temperature window (based on NO > 88% and NH3 > 87%) about 50°C. An increase in heating area decreased the reaction temperature of the maximum NO reduction from 350 to 300°C, and caused the active reaction temperature window (between 250 and 400°C) to shift toward 50°C lower reaction temperatures (between 200 and 350°C). The change of catalyst arrangements resulted slight improvement for NO and NH3 removals, therefore, the change might contribute to more gas removals. The catalyst with extra vanadium coating showed higher NO reductions and NH3 conversions than the catalyst without the extra vanadium coating.

Phase selective soluble polymers are useful in organic synthesis because they simplify purification and separation processes. Such selective soluble polymers enable the use of Green chemistry principles to be utilized as ways to simplify catalyst, reagent, and product recovery. Polyisobutylene oligomers serve as examples of such polymers. Vinyl terminated polyisobutylene (PIB) oligomers can be easily transformed into a variety of end-functionalized PIB oligomers. Previous work has shown that PIB oligomers possess nonpolar phase selective solubility that allows them to be used as polymer supports for ligands and catalysts in liquid/liquid biphasic systems. This dissertation focuses on the use of PIB oligomers as supports for a salen Cr(III) complex, a Hoveyda-Grubbs 2nd generation catalyst, and a N-heterocyclic carbene. The syntheses of these PIB-supported ligands and catalysts are simple and straightforward. The synthetic products and the intermediates in these syntheses can all be readily analyzed and monitored by conventional spectroscopic methods. The activity of the PIBsupported catalysts is shown to be analogous to that of other soluble polymer supported catalysts or their non-supported analogs. The PIB-bound catalysts can be separated from products by a latent biphasic, liquid/liquid extractions, or product self-separation systems. The recovered PIB-bound catalysts can then be recycled multiple times.

Electrode is where electricity is generated. Its quality is important to the entire battery performance. In this study, we are going to establish a stable and automatic process for making electrodes as well as required equipment. By this way, the instability in the electrode process can be improved. Electrospray technology is developed to spray the catalyst and reduce the agglomeration. It is shown that the electrode performance is 37% better than before after electrospray is adopted for producing catalyst layer. If we check the catalyst grains by AFM and TEM, we can find that the electrospray does scatter the polymers containing Nafion effectively. Under SEM, the catalyst grains are small and well proportioned on the carbon cloth. Obviously, catalysts are better utilized. All of the above can be used to explain the performance boost.

How effective would the implementation of biodiesel fuel in reducing emissions caused by automobiles and motorcycles in the densely populated regions? The goal of this research is targeted at determining the most proficient methods in depleting the harmful substances emitted from refueling stations and the efficiency of biodiesel fuel in emissions reduction. The initial stages in the research involved the use of aluminum oxide and molecular sieve, which would act as active metals for copper and manganese. Impregnation and solgel method of catalytic production were utilized with 12 sets of oxidized copper, and molecular sieve catalysts, totaling at 24 sets. With results from the primary testing, initial selection of impregnation production methods based on its conversion rate had a carrying capacity of 20% CuMn/ oxidized copper catalyst (Cu: Mn ratio at 1:1), and a 20% CuMn/molecular sieve catalyst (Cu: Mn ratio of 1:1) with the solgel method. The two exogenous tests were not only found to be the most efficient rate of conversion as base standards, but were also found to be the most competent method to date. Approximate calculations from the two catalytic testing showed that CuMn/oxidized copper catalyst conversion are less affected by variation in concentration density. Furthermore, the CuMn/oxidized copper and CuMn/molecular sieve catalysts faced a positive conversion rate when reacted with a decreased space velocity, but leveled off once it reached a specific level. Moreover, the two catalysts also faced an increased conversion rate when conducted with an increase in oxygen concentration, and reached maximized efficiency at 30% concentration. Secondary stage of the research focuses on operational efficiency of the biodiesel fuel, with emphasis on its pollutant emissions and economical standpoint. The initial testing concluded that not only did the fuel has a lower cost in reducing greenhouse gas emission than alternative energy sources, but it can also reduce SOx emissions by 7,200kg, 23 metric tons of PM10, and 262,400 metric tons of CO2 annually when applied with B2 fuel. Pollution reduction assessment indicated that if all diesel powered automobiles utilized the B10 biodiesel fuel, then it¡¦s estimated that it would have an annual THC reduction rate of 2.83x102 metric tons, 1.98x103 tons in COs, 4.56x103 in NOx, and 5.66x101 metric tons in PM gases. Furthermore, if the B20 fuel cells were incorporated, then it¡¦s estimated to have an annual reduction rate of 2.83x102 metric tons in THC, 2.83x103 metric tons of CO, 1.14x103 metric tons of NOx, and 1.16x102 metric tons of PM. Results from the beta stage testing indicated that if B10 fuel were incorporated into all diesel powered automobiles, with a budget of NT$1million would result in an annual reduction rate of 0.57 metric tons of THC, 9.12 metric tons of NOx, 0.11 metric tons of PM and a totaled 9.8 metric tons of reduction. Furthermore, if B20 were implemented, again with NT$1 million budget, we would expect to see annual reductions of 0.06 metric tons of THC, 0.25 metric tons of NOx, 2.51 tons of PM gases, totaling at 2.81 metric tons of reductions.

No description available.

No description available.