No description available.

No description available.

The rising environmental and financial consequences of using fossil fuels as an energy source and energy carrier are a global concern. Described herein are two hydrogen-storing technologies, each of which was envisioned as a potential solution to said consequences: hydrogen-storing polymethylpyridylsiloxanes for use as an alternative energy carrier to fossil fuels; and thermally regenerative fuel cell systems to supplement or supplant vehicular alternators. A thermally regenerative fuel cell (TRFC) system is being developed to convert waste heat from an internal combustion engine (ICE) system into electricity that can be used to power auxiliary vehicular components. The TRFC system will comprise a dehydrogenation reactor and a fuel cell positioned relative to the ICE system such that the two components are held at 200 °C and 100 °C, respectively. 1-Phenyl-1-propanol has been identified as an optimal hydrogen storing liquid (XH2) that will selectively dehydrogenate over a heterogeneous catalyst to give a dehydrogenated liquid (propiophenone, X) and H2. The heterogeneous catalyst that currently provides the best selectivity (99.65%) for X at 200 °C is Pd/SiO2. A selectivity of ≥ 99.9% was desired to obtain the longest possible operational lifetime for the working fluids XH2/X. To increase the selectivity for X from 99.65% to ≥ 99.9%, size and shape specific Pd nanoparticles were synthesized. Pd nanocubes (20 nm) provided the best selectivity for X at 99.26%. It was concluded that a reproducible selectivity for X of ≥ 99.9% was not currently obtainable, and that a selectivity for X no greater than 99 % should be assumed when calculating the working fluids’ operational lifetime. Hydrogen-storing polymethylpyridylsiloxanes were proposed as energy carrier alternatives to fossil fuels. Polymethylpyridylsiloxanes were considered, in part, due to the expansive liquid ranges of siloxane polymers [-40 ˚C to 250 ˚C]; this would allow the polymethylpyridylsiloxanes to be stored and pumped into vehicles using existing refueling infrastructure. Polymethylpyridylsiloxanes, and analogs thereof, however, were not successfully synthesized and reversibly hydrogenated: either the desired product(s) could not be synthesized, isolated, and/or purified; or, hydrogenation resulted in product decomposition. It was concluded, therefore, that implementing polymethylpyridylsiloxanes as hydrogen-storing liquids is not viable. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-12-24 01:01:16.857

The addition of an aldehyde C−H bond across a ketone functionality, formally a hydroacylation, has emerged as an atom-economical approach to the synthesis of esters. While this is an efficient strategy for producing biologically-relevant materials, the field of transition metal-catalyzed ketone hydroacylation is currently limited to intramolecular systems. The development of a new rhodium catalyst will be presented, and its application to intermolecular ketone hydroacylation will be discussed. Ester products were synthesized from unfunctionalized, aliphatic aldehydes and chelating ketones in excellent yields under relatively mild reaction conditions. Efforts towards an asymmetric intermolecular ketone hydroacylation will be described, including the application of known chiral catalysts and the development of novel chiral phosphine ligands for asymmetric catalysis. Ester products were obtained in as high as 78% enantiomeric excess.

<p>Over the recent past, organometallic chemistry has grown and the impact of catalytic applications in various chemical technologies has rapidly evolved from the realm of academic laboratories into full-scale industrial processes. Pyrrole-imine ligands were prepared by condensation of pyrrole-2-carboxylaldehyde with propyl amine, 2,6-diisopropylanaline, poly(propylene) imine dendrimer and 3-aminopropyl-triethoxysilane to give the desired ligands in good yields. These ligands were charaterized via combination of techniques to establish the molecular structure. Microanalysis was performed to confirm the purity of the product.</p>

No description available.

No description available.

No description available.

A stable high temperature gold nano-catalyst: synthesis, characterization and application The ability of supported gold nanoparticles to catalyse many reactions even at very low temperatures has spurred a great deal of research into the eld. Reactions such as CO oxidation and NOx reduction have many industrial applications as well as uses in the motor industry for catalytic converters. The interest is both for scienti c as well as economic reasons as gold supplies far exceed all PGM supplies. Scienti cally gold catalysts are able to catalyze reactions from below 0°C, a feat that no PGM catalyst can achieve. The low temperature activity of gold catalysts will reduce the emission of pollutants during start up. Since the discovery and development of gold catalysts one of the most researched topics has been nding ways to stabilise the gold nanoparticles on the support surface. The importance of gold nanoparticle stability is crucial as the catalysts are only highly active if the gold nanoparticles are less than 5 nm in size. A number of companies have worked to develop gold catalysts that are stable for long durations at temperatures over 450°C with no signi cant progress made over the last two decades other than a catalyst produced by Toyota. In this thesis, literature reviews of current support materials as well as synthesis methods are investigated in order to determine reasons for the instability of current gold catalysts. Further, the Mintek Aurolite catalyst is tested and its deactivation mechanisms probed using in-situ VT-PXRD, Rietveld re nement, TEM, HR-TEM, as well as CO oxidation tests. Testing revealed aws in the support structure of the catalyst which resulted in dramatic deactivation. As titania is such a common support material for many reactions in industry as well as being known to be one of the best supports for gold it was chosen as a support material. However, as is revealed, in its current forms and morphologies it is unable to provide the thermodynamically stable and high surface areas that are required for a stable catalyst After the development of a robust and reproducible synthesis method for the deposition of gold and other PGM's a number of supports were tested. These include silica and zirconia as well as titania derivatives such as Degussa P25 and commercial anatase. Initially these supports o er high usable surface areas but after a relatively small amount of time complete deactivation occurs. Reasons for this deactivation are determined and the information gained is used to develop supports that can combat these deactivation processes. Phase pure nano anatase is synthesised which produced a support with an incredibly large surface area compared to the aforementioned supports. The catalyst was able to withstand temperatures over 450°C for longer durations compared to other catalysts exposed to the same conditions. However, the phase conversion of the anatase to its thermodynamically stable form rutile once again deactivated the catalyst with time. Finally a rutile nanosupport is developed with the desired morphology and thermodynamic stability needed for high temperature applications. The catalyst is able to withstand temperatures over 550°C for more than 200 hours as well as still being active after exposure to 810°C. The industrial Aurolite catalyst showed complete deactivation after just 12 hours at 500°C. The catalyst produced in this thesis has been shown to be one of the most stable and thermally resistant gold catalysts in the world.

Zeolite catalysts were prepared by carrying out an ion-exchange process of transition metals and impregnation to incipient-wetness method of metal catalyst using a chlorine free gold precursor, KAu(CN)2. The instability of Au/Y (3.74wt%Au) resulted in low CO oxidation activity (~ 18 % conversion at 450 0C), suggesting that the reduced gold metal atoms are bound to the zeolite by a weak interaction. This is subject to migration within the passages of the zeolite during use. The presence of proton stabilized most of Au clusters (electron deficient species) within the HY zeolite, resulting in small amounts of gold species migrating to the outer surface. Interestingly the CO oxidation activity of Au/HY is half that of Au/Y, which clearly indicate that the presence of metallic gold plays a significant role during CO oxidation. The loading of Au/M-Y (M = Ni2+, Fe3+, Co2+ or Cr3+) were varied from 1.67- 7.48wt%Au and from 1.76-5.45wt%M. Modification of this Y structure with transition metals has been found to be beneficial for both activity and stability of smaller gold clusters, by strengthening the interaction between gold and zeolite exchange sites and by large magnitude in maintaining the dispersion of gold. This suggests that the unreduced chromium ions function as a chemical anchors for reduced Au metal and that the reduced atoms of gold may form small clusters with the anchoring metal. TPR profile has confirmed that the introduction of 1.67wt%Au on Fe-Y (1.88wt%Fe) increased the stability of Fe ions as stabilizer metal. However, as the gold loading of Au/Fe-Y catalyst increases the TPR profile shows that the stability of Fe ions decreases and hence the activity of catalysts. An increase in transition metal content, above 1.88wt%Fe was found to lower the CO oxidation activity. A TPR profile has confirmed that as the reduction potential became more negative, the activity of supported Au increases following the sequence: Ni2+, 0.23 << Fe3+, -0.41 < Cr3+, -0.56. The estimated particle sizes of gold by X-ray diffraction were found to be ~ 12 nm for Ni2+, ~ 7 nm for Fe3+, and ~ 5 nm for Cr3+ stabilized metal. Samples of Au/HY (3.77wt%Au) have been prepared by an ion-exchange method using Au(III) ethylenediamine complex-ions, [Au(en)2]3+. Following a pretreatment in an O2 atmosphere, the catalyst showed the existence of an induction period before reaching a steady state activity; suggesting the need for activating gold prior to catalyzing CO oxidation reaction. As-prepared catalyst contained 85% of gold in the Au3+ valence state as confirmed by Mössbauer spectroscopy. The catalyst was treated with various reducing agents (such as NaBH4); to yield stable and active smaller gold clusters (< 2 nm) inside the HY cavities, as revealed by X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and Uv- Vis Spectrophotometer. DRIFTS revealed that electron-deficient particles (Auó+- CO species) of gold clusters, inside the HY framework and in contact with protons are active species for CO oxidation. CO activity and formation of smaller gold clusters depends on the nature and molar ratio of reducing agents, and the source of gold. The induction period observed for unreduced Au catalyst is a slow step in the activation of gold active sites. Treatment of Au/Y (3.46wt%Au) with sodium borohydride enhanced the activation of gold active species and hence improves the catalytic activity. The NaBH4 treated Au/Y (3.73wt%Au) catalyst has shown, for the first time, activity of approximately 28% CO conversion. The catalyst showed almost the same activity and induction period as that of the untreated Au/HY (3.77wt%Au) catalyst, which leaves much to be investigated about the behaviour of Au on Y zeolite upon treatment with a proper reducing agent. The protons have been found to stabilize the smaller Au nanoparticles within the zeolite cavities. The modification of zeolite-Y was carried out by treatment with different alkali metal nitrates such as LiNO3, NaNO3 and KNO3 before introducing gold from different sources, (i.e. gold ethylenediamine complex ion, Au(en)2Cl3; chloroauric acid, HAuCl4; or potassium dicyano aurate, KAu(CN)2 complex). The CO oxidation activity of the catalysts was found to depend on the nature of the gold source and on the type of alkali metal nitrate used. The order of activity was as follows: HAuCl4 >> KAu(CN)2 > Au(en)2Cl3. It was found that the activity of catalysts prepared by deposition of Au from an aqueous solution of chloroauric acid on Na-modified zeolites-Y, increased as a result of an increase in the amount of Au deposited as confirmed X-ray fluorescence spectroscopy (XRF). The Kmodified zeolite-Y had a smaller amount of Au deposited (i.e. Au/KY, 0.454wt%Au; Au/NaY, 0.772wt%Au and Au/LiY, 0.212wt%Au) and hence the CO oxidation activity was lower than that of Na-modified zeolites-Y. Thus, the order of the catalytic activity is as follows: Na > K > Li. The XRD studies have revealed that metallic gold particles sizes do not depend on the nature of alkali metal nitrates used to modify the zeolite-Y surface and the zeolite-Y crystallinity has been maintained. Monometallic Au/NaY (0.772wt%Au, treated with NaNO3) was found to be active in ethylene hydrogenation with ~5% conversion. Treatment of catalysts with NaBH4 was found to lower the catalytic activity of the catalysts, contrary to activities observed on CO oxidation and these concluded that cationic gold are responsible for the observed activity. The activity was found to depend on the source of Au used, and the order is as follows; HAuCl4 >> KAu(CN)2 > Au(en)Cl3. Bimetallic catalysts of Au/M-Y (where Au represent gold from KAu(CN)2, and M = Ni2+, Fe3+, or Cr3+) were found to be more active compared to monometallic catalysts due to promotional effect of transition metal. The order of activity of the bimetallic system at 260 0C was as follows; Ni2+ >> Fe3+ > Cr3+, and at 150 0C, was Ni2+ >> Cr3+ > Fe3+, contradicting the order of activity observed on CO oxidation. Formation of carbonaceous deposits on the surface of the catalyst at temperature higher than 260 0C has been confirmed. Cu modified Au/TiO2 (anatase, 200m2/g) has been prepared by incipient-wetness method by either introducing the modifier, before or after Au loading. Such catalysts were found to give high and stable activity for the water-gas shift (WGS) reaction, when compared to unmodified Au/TiO2 catalysts. It has been suggested that an increase in activity on modified Au/TiO2, is mainly due to the existence of a synergetic interaction between Cu and Au, since the activity of both Cu/TiO2 and Au/TiO2 is lower than that of bimetallic system. The presence of nitrates on Cuc-Au/TiO2 (c Cu precursor is Cu(NO3)2*2.5H2O) has been found to be detrimental to the activity of Au on TiO2; due to the poisoning of Au active sites and enhancement of Au agglomeration by NO2 - formed during the reaction. An increase in Cu loading lowers the activity of Au. A XANES spectrum has confirmed that gold exists as either Au+/Au0 during WGS reaction and Cu exists as copper ions (Cu+/Cu2+) before and during WGS reaction. Formation of bimetallic particles was not detected by EXAFS data analysis. The observed effects are interpreted as a mutual influence of gold and copper ions and reduced species of gold and copper due to their competing for ion exchange sites. Cu has no promotional effect on low temperature CO oxidation and on preferential CO oxidation in excess of hydrogen.