James R. Brenner

Synthesis and characterization of molybdenum nitride hydrodenitrogenation catalysts

Abstract Details concerning the relationships between the structural, chemical and catalytic properties of Mo nitrides have been elucidated. A series of Mo nitride catalysts were prepared by the temperature programmed reaction of MoO3 with NH3. The structural properties of these nitrides were complex functions of the heating rates and space velocities employed. Two reaction sequences were proposed to account for the synthesis of high, medium and low surface area materials. An interesting conclusion was that the degree of reduction of the molybdate precursor or intermediate governed the structural properties of the product. Some evidence is also presented to suggest that the nucleation and growth rates involved in the transformation of the oxide to the nitride were significantly influenced by the synthesis conditions. The Mo nitrides proved to be exceptional pyridine hydrodenitrogenation catalysts. Their catalytic properties were superior to those of a commercial sulfided Co-Mo hydrotreatment catalyst, having higher activities and better C-N bond hydrogenolysis selectivities. Hydrodenitrogenation over the Mo nitrides appeared to be structure-sensitive. While detailed relationships between the catalytic activity and surface stoichiometry could not be ascertained, there did appear to be a correlation between the activity, and the particle size and grain boundary length. We proposed that at least two types of HDN sites existed on the Mo nitride surfaces; modest activity sites on the particles and high activity sites at grain boundaries. The N/Mo stoichiometry of the highest activity catalyst was near unity suggesting that MoN was present perhaps localized at the grain boundaries. Finally structures near or at the surface were markedly different from those of the bulk. While the predominant bulk phase was γ-Mo2N, the surface appeared to consist of either non-stoichiometric β-Mo16N7 or mixtures of Mo and β-Mo16N7.

Microwave plasma synthesis of carbon-supported ultrafine metal particles

Abstract Microwave plasma decomposition of metal carbonyls has been used to synthesize a series of carbon-supported monometallic (Fe, Co) and bimetallic (Co-Mo) materials. The average metal particle diameters in all cases were less than 10 nm. By using 10% H 2 /Ar instead of pure Ar as a carrier gas, the mean particle diameters could be decreased to less than 2 nm. Although the distribution of particles is slightly broader than those generated by other nanoparticle synthesis methods, the mean diameter of the particles generated using 10% H 2 /Ar is as small as any previously reported for Fe-, Co-, Ni-, or Mo-containing compounds. The ultrafine metal particles were dispersed on moderate surface area amorphous carbon support matrixes derived from the concomitant microwave decomposition of the toluene solvent.

Materials derived from synthetic organo-clay complexes as novel hydrodesulfurization catalyst supports.

A series of mesoporous synthetic organo-clay complexes has been prepared by hydrothermal crystallization of gels containing silica, magnesium hydroxide, lithium fluoride, and an organic of choice, followed by calcination to remove the organics. The organic serves to impart structural order to the inorganic network that does not disappear upon its removal. The choice of organic modifier can be used to control the pore structure of the resulting mesoporous materials. Pore size distributions appear in some cases to be related to the type of polymer packing upon clay formation in situ. These materials are being explored as Co Mo hydrodesulfurization (HDS) catalyst supports. Preliminary HDS results show performance commensurate with commercial catalysis for the mesoporous materials when a model heavy oil feed is used (1 wt% S as dibenzothiophene in hexadecane). Temperature programmed reduction experiments of used catalysts suggest a relationship between HDS activity and ease of reduction of the CoMo/clay catalysts. Reactivity of the CoMo clay also correlates with the percentage of mesopore volume remaining after reaction. Losses in mesopore volume are largely recouped by recalcination, suggesting that reversible coke is formed inside the pore structure of clays faster than inside conventional alumina.

Hydrogen purification with palladium and palladium alloys on porous stainless steel membranes

Hydrogen purification membranes have been prepared via a simultaneous electroless plating of Pd and Ag on a 0.5 ?m media grade Porous Stainless Steel (PSS). Effects of the electroless bath temperature, composition, annealing time and temperature were studied while developing the Pd coating. Very low but measurable N2 fluxes were seen, ranging from 0.010 to 0.020 cm?/cm?-min at temperatures varying from 300?C to 400?C. As no helium flux was observed, it appears that nitrogen diffused, albeit much more slowly, through the same interstitial sites that hydrogen did. H2 permeances varying from (1.9?3.1) ? 10?2 cm?/cm?-min-Pa0.5 were recorded between temperatures from 350?C to 550?C. Sieverts Law was seen to hold true at all temperatures. Short term stability and reproducibility of the H2 permeance were confirmed. The activation energy (Ed) for H2 permeance in the Pd-Ag layer was calculated from the permeance data to be 9 ? 1 kJ/mol.

Development of a Passively Cooled, Electrically Heated Hydride (PACE) Bed

ABSTRACT A nominal 1500 STP-L PAssively Cooled, Electrically heated hydride (PACE) Bed has been developed and tested. The bed contained 12.6 kg of a La-Ni-Al alloy and used aluminum foam to improve heat transfer within the bed. Steady-state temperature measurements made at constant power showed a nonuniform bed temperature profile. Protium absorption rates were measured at pressures of 253 kPa, 413 kPa, and 680 kPa with forced convection cooling air flow rates ranging from 50 to 150 SLPM air. Absorption tests were also performed simulating the absorption of tritium and a method for estimating this rate using protium absorption data presented. Desorption rates were measured at pressures ranging from 20 kPa to 933 kPa using dual and single 400 watt electric heaters and found desorption rates were only impacted at the beginning and the end of a desorption cycle by the use of a single heater.

Collagen incorporation within electrospun conduits reduces lipid oxidation and impacts conduit mechanics.

Modulating the host response, including the accumulation of oxidized lipid species, is important for improving tissue engineered vascular graft (TEVG) viability. Accumulation of oxidized lipids promotes smooth muscle cell (SMC) hyper-proliferation and inhibits endothelial cell migration, which can lead to several of the current challenges for small-diameter TEVGs. Generating biomaterials that reduce lipid oxidation is important for graft survival and this assessment can provide a reliable correlation to clinical situations. In this study, we determined the collagen to poly(ε-caprolactone) (PCL) ratio required to limit the production of pro-inflammatory species, while maintaining the required mechanical strength for the graft. Electrospun conduits were prepared from 0%, 10%, and 25% blends of collagen/PCL (w/w) and implanted in the rat peritoneal cavity for four weeks. The results showed that adding collagen to the PCL conduits reduced the accumulation of oxidized lipid species within the implanted conduits. In addition, the ratio of collagen had a significant impact on the recruited cell phenotype and construct mechanics. All conduits exhibited greater than 44% yield strain and sufficient tensile strength post-implantation. In conclusion, these results demonstrate that incorporating collagen into synthetic electrospun scaffolds, both 10% and 25% blend conditions, appears to limit the pro-inflammatory characteristics after in vivo implantation.

Characterization of HDS/HDN active sites in cluster-derived and conventionally-prepared sulfide catalysts

Abstract The catalytic and sorptive properties of a series of sulfide cluster-derived catalysts were compared to those of an analogous series of conventionally-prepared sulfides. The cluster-derived and conventionally-prepared catalysts had similar hydrotreatment activities and chemisorbed similar amounts of O 2 and NO. From infrared spectroscopy, it was observed that the clusters retained much of their character upon adsorption, and that the CO ligands were lost upon heating up to 350 K. Nitric oxide chemisorbed onto the bimetallic cluster-derived catalysts was initially associated with the Co sites then shifted to the Mo sites upon heating, indicating that the promoter and Mo were in close proximity. For the conventionally-prepared materials, NO adsorption suggested that the promoted and unpromoted sites behaved independently. Nitric oxide was more strongly held to the unpromoted sites in both the cluster-derived and conventionally-prepared materials. Thiophene adsorbed onto the cluster-derived and conventionally-prepared catalysts gave rise to nearly identical infrared spectra. Upon heating, the thiophene peaks disappeared and were replaced by peaks that we have attributed to a linear olefin, which is noteworthy since 1-butene was the primary product from thiophene HDS. Nitric oxide easily displaced adsorbed thiophene from the cluster-derived materials, indicating that NO and thiophene adsorbed onto the same sites.

Designer Carbons Templated by Pillared Clays: Lithium Secondary Battery Anodes

This work describes the designed synthesis and physical characterization of carbons containing predictable microporosity. The approach is to pyrolyze aromatic hydrocarbons such as pyrene within a pillared clay. The pillared clay serves two functions. It performs as the inorganic template around which the designer carbon can be formed, and it acts as the acid catalyst to promote condensation of the aromatics similar to the Scholl reaction. These precursors then undergo thermal polymerization and carbonization at 700{degrees} C. Removal of the pillared clay template is accomplished by standard acid demineralization techniques, leaving behind carbons with 15 to 20 {Angstrom} holes.

Simulation and thermodynamic analysis of extended expansion on a concept rotary engine including its effects on fuel efficiency

Abstract This paper describes a novel method for extended expansion in a rotary combustion engine running ordinary gasoline. The engine consists of a toroidal-shaped piston that rotates around a drum to expand and evacuate the hot gas. There are several problems with today’s internal combustion (IC) engines. Current IC engines do not always have the necessary internal volume to extract the maximum work possible, and since the whole process of compression, combustion, and expansion happen within the same space, excess heat builds up and increases emissions of nitric oxides and nitrogen dioxide. The proposed solution is to redesign the IC engine in order to supply greater expansion ratio by separating the compression and expansion processes. With the concept rotary engine, extending the expansion process showed improvements in the thermal and fuel efficiencies. Using a stroke length between 20 and 25 cm with a compression ratio of 10:1 produced the most efficient results with an efficiency range between 32 and 35%.