As traditional sources of energy become depleted, significant research interest has gone into conversion of biomass into renewable fuels. Biomass-derived synthesis gas typically contains concentrations of approximately 30 to 600 ppm H2S in stream. H2S is a catalyst poison which adversely affects downstream processing of hydrogen for gas to liquid plants. The water-gas shift reaction is an integral part of converting CO and steam to H2 and CO2. Currently, all known water-gas shift catalysts deactivate in sulfur concentrations typical of biomass-derived synthesis gas. Novel catalysts are needed to remain active in the presence of sulfur concentrations in order to boost efficiency and mitigate costs. Previous studies have shown molybdenum to be active in concentrations of sulfur greater than 300 ppm. Cobalt has been shown to be active as a spinel in concentrations of sulfur less than 240 ppm. Ceria has received attention as a WGS catalyst due to its oxygen donating properties. These elements were synthesized via Pechini's method into various blends of spinel metal oxide solutions. Initial activity testing at lower steam to gas ratios produced near equilibrium conversions for a Ce-Co spinel which remained active in 500 ppm H2S over a temperature range of 350 °C to 400 °C. The catalysts became poisoned and deactivated in higher concentrations of sulfur. Addition of molybdenum to the Ce-Co base had little effect on sulfur tolerance, but it did lead to a reduction in selectivity for methanation. Surface area increased due to adsorbed H2S, and X-Ray Diffraction confirmed that bulk sulfiding did not occur. Incorporation of Ce and Co into a Fe spinel hindered conversion at lower temperatures and deactivated in higher levels of sulfur.

The interaction of the 2,3-diazanaphthalene, phthalazine and its 1-substituted derivatives with the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, has been investigated both in vivo and in vitro. Metabolic studies, carried out by treating rabbits with both cold and ¹⁴C-labelled phthalazine, have shown that this compound is extensively metabolised in vivo, the major metabolite being a glucuronide conjugate. Very little unchanged phthalazine or its molybdenum hydroxylase mediated oxidation product 1-hydroxyphthalazine were excreted in the urine. Pretreatment of rabbits with phthalazine or 1-hydroxyphthalazine had no effect upon the activity of the microsomal monooxygenases but caused a significant increase in the specific activities of both aldehyde oxidase and xanthine oxidase. Determination of the molybdenum content of purified aldehyde oxidase fractions using electrothermal atomic absorption spectroscopy has confirmed that an increase in the molybdenum content of the enzyme fraction accompanies the increase in activity. A qualitative assessment of purified aldehyde oxidase fractions using iso-electric focusing has indicated that this enzyme may be composed of 2 or 3 active variants and following pretreatment with either phthalazine or 1-hydroxyphthalazine a further band of enzyme activity is apparent on the electropherogram. The Km value for phthalazine is significantly reduced with enzyme prepared from phthalazine treated rabbits, indicating that a form of the enzyme with a high affinity for phthalazine may have been induced. 1-Hydrazinophthalazine (Hydralazine) and two other hydrazine substituted N-heterocycles, endralazine and 1-hydrazinoisoquinoline have been shown to exert a potent progressive inhibition of aldehyde oxidase in vitro, effective only in the presence of substrate, but are inactive towards xanthine oxidase. In addition, administration of hydralazine to rabbits results in a significant reduction in liver aldehyde oxidase activity. Investigations into the interaction of some of the metabolites of hydralazine with aldehyde oxidase in vitro suggest that hydralazine is also the inhibiting species in vivo.

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No description available.

This dissertation comprises the investigation of two subjects in the field of dimetal paddlewheel-type compounds containing metal-metal bonds: unsolvated transition metal carboxylates and triply bonded divanadium compounds. The first subject is very mature; dichromium tetraacetate was first synthesized in 1844, and hundreds of dimetal tetracarboxylates have been structurally characterized to date. A general question concerning the complexes of the type M2L4-Xn (where n = 0 to 2) is the extent to which the M-M distances are influenced by the presence of axial ligands, X. However, virtually none of the carboxylato complexes crystallize without axial ligands. In the solid state, in the absence of a coordinating solvent, the dimetal units often act as axial ligands to one another. In order to exclude axial coordination, both from donor solvent molecules, and from the aggregation of M24+ units, we have successfully used the bulky 2,4,6-triisopropylbenzoate ligand to bridge the dimetal core. We have investigated the triisopropylbenzoato complexes of some metals which are known for their ability to form a vast array of tetracarboxylato complexes, namely chromium, copper, molybdenum, and rhodium, and have found that these novel compounds display some interesting structural and chemical properties. The second subject of this dissertation is much more contemporary. Although compounds containing multiple bonds between metal atoms have been known since 1964, the first triply-bonded divanadium compound was not synthesized until 1992, and only two additional compounds of this type have been made in the intervening ten years. In order to extend this chemistry, several additional compounds containing a triply bonded V24+ core have recently been characterized. In our study of these compounds, we have discovered the first example of a stable paddlewheel-type compound with a M23+ core.

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No description available.

In the final thesis there is analyzed of chrome-molybdenum steel (5%Cr-0,5%Mo) welded joints strength properties dependence on thermal treatment after welding procedures investigation material. Welded joints ultimate strength and impact strength were determined, changing heat treatment after welding temperatures and exposure time. Heat treatment temperature and time parameter was used to systemize investigation. Received results showed that when performing heat treatment after Cr-Mo steel (5%Cr-0,5%Mo) welding, increasing temperature and time parameter values, welded joints strength characteristics values go down. Welded joints after heat treatment strength properties dependence on temperature and time parameter were determined, increasing this parameter, ultimate strength and impact strength values go down.

I have measured the magnetic and transport properties of Fe and Co in the variable SDW host, CrMo. Analyzing the behaviour of the Neel temperature shows that Co interacts with the SDW, almost an order of magnitude more strongly than does Fe. Also that it magnetically polarizes the SDW more strongly than Fe. Resistivity measurements show that Co reduces the nesting area of the Fermi surface while Fe increases it. Overall, the Neel temperature is strongly reduced by Fe and much less reduced by Co. / Magnetic susceptibility measurements show that Fe supports an effective magnetic moment below T(,N) while Co does not. However, as suggested by Friedel, only nearest neighbour Fe pairs contribute to the effective Fe moment, while isolated Fe moments, like Co, are locked into the SDW antiferromagnetism. / In the absence of SDW formation, the strong interaction between Co and the CrMo host leads to a Kondo state, while the smaller interaction with Fe allows the onset of spin glass ordering.

Layered metal sulfides MoS2 and WS2 exhibit highly anisotropic surface chemistry. Adsorption of molecules is stronger on the atomic layer edges than on atomic planes. The edges are catalytically active in the petroleum hydrodesulfurization, while the layer planes are inert. Dispersing MoS2 and WS2 on the nanometer scale can also lead to the onset of photocatalytic properties due to the bandgap tuning by quantum confinement. In this work, we aim at determining how the adsorption on surface sites is altered for the nanoparticles compared to the bulk sulfides (micron-sized particles). A comparative study of the MoS2 and WS2 nanoparticles and bulk materials is done by attempting the adsorption of small molecules (N2, CO, acetone, and acetonitrile) to probe the surface sites. MoS2 and WS2 nanoparticles were synthesized by thermal decomposition of the metal hexacarbonyls in presence of sulfur in high-boiling solvents. The size range is 5-30 nm from Transmission Electron Microscopy. Transmission Infrared Spectroscopy was used to monitor the spectra of the probe molecules. A dedicated experimental setup has been constructed that consists of a high-vacuum chamber with a base pressure of 5×10-7 Torr. At the lowest achievable temperature of the sample (-145°C), N2, CO, and acetone were found to not adsorb strongly enough to be retained in vacuum on these materials. Acetonitrile was found to adsorb on these materials at -145°C and to desorb between -90°C and -50°C. The nanomaterial samples adsorbed significantly more acetonitrile than the corresponding bulk sulfides, as judged by the infrared signals intensity. Qualitatively, adsorbed acetonitrile species on nanodispersed and bulk sulfides are the same. It is likely that most of the adsorbed acetonitrile observed is physisorbed as ice or adsorbed on the sulfur-terminated terraces. At the final stages of desorprtion, distinctly different adsorbed species are seen whose CN stretching IR bands are shifted to higher frequencies. It is likely that these minority species are at monolayer or submonolayer coverages. The exact nature of the species requires further studies. / Department of Chemistry