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The purpose of this work is to identify surface intermediates during the catalytic oxidation of isobutanol in a Fourier transform infrared (FTIR) reaction chamber at various temperatures and equivalence ratios (). This was achieved by collecting infrared spectra of surface species and locating peaks that would characterize the presence of these intermediates and products, such as carbon dioxide (CO2), olefins, and aldehydes. The reaction was studied using γ-Al2O3, Rh/Al2O3, and Pd/Al2O3 powders as catalysts at temperatures from 100?500 ?C over three equivalence ratios: 0.1718, 1.4248, and 3.501. By comparing the ratio of the intensity of the CH peak representative of isobutanol to the intensity of the C=O peak representative of aldehydes, it is possible to elucidate a trend in the activation of aldehyde formation from isobutanol. The results show that increasing temperature promotes aldehyde formation on the surface of each catalyst. In addition, it is shown that palladium (Pd) activates the formation of aldehydes and CO2 at a lower temperature than a rhodium (Rh) catalyst.

The catalytic production of economically important four-carbon olefins was achieved through catalytic oxidative dehydration of 1-butanol, 2-butanol, and isobutanol using a millisecond contact time reactor. Both alumina foam and rhodium-alumina foam catalysts convert these four-carbon alcohols into four-carbon olefins, with contact time equal to 25 ms over a wide range of equivalence ratios (phi) from 0.176 to 6.338 (or C/O(air) ratio from 0.0659 to 2.11). The cracking of the carbon backbone was found to be minimal. A mixture of butene isomers was obtained due to the isomerization of the carbocation intermediates. The degree of this isomerization was determined by analyzing the ratios of butenes/(total olefins), 1-butene/2-butene, cis-2- butene/trans-2-butene, and isobutene/(linear butenes). In addition, a reaction mechanism of the catalytic oxidative dehydration of butanol in short contact times was proposed. In this mechanism, the C-O bond of the majority of butanol was broken to form olefinic species on the alumina surface. These surface olefinic species would undergo successive oxidation to form CO and/or CO(2), depending on the availability of oxygen., The original document contains color images.

A flame synthesis method has been used to prepare nanosized, high-surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction and then gas to particle conversion. The specific surface areas of the synthesized powders ranged from 127 to 163 sq m/g. High-resolution transmission electron microscope imaging showed that the particle diameters for the ceria materials are in the range of 3-10 nm, and a thin layer of amorphous material was observed on the surface of the particles. The presence and surface enrichment of the transition-metal oxides (CuO, NiO, and Fe2O3) on the ceria particles were detected using X-ray photoelectron spectroscopy. Electron energy-loss spectroscopic studies suggest the formation of a core-shell structure in the as-prepared particles. Extended X-ray absorption fine structure studies suggest that the dopants in all M-Ce-O systems are almost isostructural with their oxide counterparts, indicating the doping materials form separate oxide phases (CuO, Fe2O3, NiO) within the host matrix (CeO2). Etching results confirm that most of the transition-metal oxides are present on the surface of CeO2, easily dissolved by nitric acid. The performance of the flame-synthesized catalysts was examined toward water-gas shift (WGS) activity for fuel processing applications. The WGS activity of metal ceria catalysts decreases in the order Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO2 with a feed mixture having a hydrogen to carbon monoxide (H2/CO) ratio of 1. There was no methane formation for these catalysts under the tested conditions., Sponsored in part DOE Grant Nos. DE-FG02-03ER15476, and DE-FG02-05ER15688, and DOE Contract No. DE-AC02-98CH10886. Published in Applied Materials and Interfaces, v1 n11 p2624-2635, 2009.

The combustion of energy dense liquid fuels in a catalytic micro-combustor is an attractive alternative to cumbersome batteries. To miniaturize the reactor, I developed an evaporation model to calculate the minimum distance required for complete droplet vaporization. By increasing the ambient temperature from 298 K to 325 K, the distance required for complete evaporation of a 6.5 micron droplet decreases from 3 to 0.15 cm. A platinum mesh acted as a baseline measurement and demonstrated 75% conversion of ethanol. I then selected a more active rhodium-coated alumina foam with a larger surface area and attained 100% conversion of ethanol and 95% conversion of butanol under fuel lean conditions. Effluent post-combustion gas analysis showed that varying the equivalence ratio results in two distinct regimes. A regime of high carbon selectivity for CO2 occurs at low equivalence ratios and corresponds to complete combustion with a typical temperature of 775 K that is ideal for PbTe thermoelectric devices. Conversely, for equivalence ratios greater than 1, carbon selectivity for CO2 decreases and hydrogen production increases. By tuning the equivalence ratio, I have shown that a single device can combust completely for thermoelectric applications, or operate as a fuel reformer to produce hydrogen gas for fuel cells., The original document contains color images.

Microscale combustion differs from the mesoscale or large-scale combustion, in general. As the size of the combustor decreases, surface-to-volume ratio (S/V) increases. Surface effects (interfacial phenomena) and time-scaling become more important. Heat recirculation, combustion in porous media, and catalytic combustion are employed to achieve combustion in microscale. The microscale combustion devices can be integrated with thermoelectric and thermophotovoltaic devices for power and energy applications. Recent advances in microscale combustion are summarized in this report., The original document contains color images.

The goal of this research was to explore the use of nanotube titanium dioxide (TiO2) as an electrode material in dye-sensitized solar cells in order to further the development of solar cell technology. TiO2 nanotubes were successfully synthesized by hydrothermal methods, working solar cells were constructed, and comparisons were made between nanospherical TiO2 and nanotubular TiO2. The results showed an increase in the maximum photocurrent density, Jsc, at the expense of a lowered fill factor that led to a lowered cell efficiency. It is suggested that improvements can be realized by the use of aligned TiO2 nanotubes in order to enable a higher packing density of the nanotubes that would lead to a higher photocurrent density per square centimeter, thereby converting a portion of the incoming solar energy into electrical energy., The original document contains color images. Project No. FY07-SED-01.

This paper describes our research efforts towards the preparation of high surface area ceria oxide (CeO2) containing catalysts for fuel processing and therefore for fuel cells applications. In the present work, we present a simple. single step flame synthesis method to prepare high surface area ceria based fuel reformation catalysts using aqueous solutions of metal acetate precursors. The specific surface areas of the synthesized powders are in the range of 130 and 163(meter squared)/g. High-resolution transmission electron microscopic (TEM) characterization showed that the particle sizes for the ceria materials are in the range of 3 and 10 nm. X-ray diffraction (XRD) and X-ray photoelectron spectra show the presence of transition metal oxide in the as prepared catalysts. The catalysts also test for water-gas-shift (WGA) reaction., See also ADM001736, Proceedings for the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2004. The original document contains color images. Prepared in cooperation with Dept. of Chemical Engineering, University of Maryland, College Park, MD.

Military jet fuel (JP-8) has been successfully reformed to produce synthesis gas (hydrogen and carbon monoxide) selectivity with a rhodium-based catalyst. Time-on-stream experiment indicates that the catalysts remains stable and active for at least 4 hours using a jet fuel (310 ppm sulfur) straight from the pump without pre-reforming sulfur removal. The dry gas composition of the product (reformate) includes about 15% hydrogen, 20% CO, 1% methane, 58% nitrogen and others. This JP-8 reformer can potentially be integrated with a reformate sulfur sorption bed and a solid oxide fuel cell for tactical power applications., See also ADM001736, Proceedings of the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2004. The original document contains color images.