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Klettlinger, Jennifer Lindsey SuderFischer-Tropsch Cobalt Catalyst Improvements with the Presence of TiO2, La2O3, and ZrO2 on an Alumina Support
Master of Science in Engineering, University of Akron, 2012, Chemical Engineering
The objective of this study was to evaluate the effect of titanium oxide, lanthanum oxide, and zirconium oxide on alumina supported cobalt catalysts. The hypothesis was that the presence of lanthanum oxide, titanium oxide, and zirconium oxide would reduce the interaction between cobalt and the alumina support. This was of interest because an optimized weakened interaction could lead to the most advantageous cobalt dispersion, particle size, and reducibility. The presence of these oxides on the support were investigated using a wide range of characterization techniques such as SEM, nitrogen adsorption, x-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed reduction after reduction (TPR-AR), and hydrogen chemisorptions/pulse reoxidation. Results indicated that both La2O3 and TiO2 doped supports facilitated the reduction of cobalt oxide species in reference to pure alumina supported cobalt catalysts, however further investigation is needed to determine the effect of ZrO2 on the reduction profile. Results showed an increased corrected cluster size for all three doped supported catalysts in comparison to their reference catalysts. The increase in reduction and an increase in the cluster size led to the conclusion that the support-metal interaction weakened by the addition of TiO2 and La2O3. It is also likely that the interaction decreased upon presence of ZrO2 on the alumina, but further research is necessary. Preliminary results have indicated that the alumina-supported catalysts with titanium oxide and lanthanum oxide present are of interest because of the weakened cobalt support interaction. These catalysts showed an increased extent of reduction, therefore more metallic cobalt is present on the support. However, whether or not there is more cobalt available to participate in the Fischer-Tropsch synthesis reaction (cobalt surface atoms) depends also on the cluster size. On one hand, increasing cluster size alone tends to decrease the active site density; on the other hand, by increasing the size of the cobalt clusters, there is less likelihood of forming oxidized cobalt complexes (cobalt aluminate) during Fischer-Tropsch synthesis. Thus, from the standpoint of stability, improving the extent of reduction while increasing the particle size slightly may be beneficial for maintaining the sites, even if there is a slight decrease in overall initial active site density.

Committee:

Steven Chuang, Dr. (Advisor); George Chase, Dr. (Committee Member); Bi-min Zhang Newby, Dr. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Fischer-Tropsch; cobalt; zirconia; titania; lanthanum oxide; titanium oxide; zirconia oxide; Fischer-Tropsch Catalysis; cobalt catalysts

Jing, YinComputer Simulation of a Plug Flow Reactor for Cobalt Catalyzed Fischer Tropsch Synthesis Using a Microkinetic Model
Master of Science (M.S.), University of Dayton, 2012, Chemical Engineering
With the rising demand for more energy and limited availability of depleting crude oil reserves, it is increasingly important to look for alternatives to classic petroleum production. Fischer-Tropsch synthesis is recognized as a very promising process to convert natural gas, coal and biomass into liquid fuel, which can reduce the dependence on fossil fuel. In order to give more reliable data about catalyst selectivity and yield before bulk production, this research is going to simulate a plug flow reactor used for Fischer-Tropsch synthesis. While these reactors have been simulated before, this research will be the first to combine models of (a) the microkinetics on the catalyst surface, (b) diffusion into and out of the catalyst pore and (c) macroscopic composition profile along the reactor. The method adopted in this research is a combination of numerical techniques, such as Runge-Kutta Method, Shooting Method and Secant Method. The resulting simulation package will offer insights into catalyst design and provide more reliable information on catalyst selectivity and product yield over a wide range of process parameters.

Committee:

Amy Ciric, PhD (Advisor); Heinz Robota, PhD (Committee Member); Michael Elsass, PhD (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Fischer-Tropsch synthesis; kinetics mechanism; cobalt catalysts; H-assisted CO dissociation; simulation

Balagurunathan, JayakishanInvestigation of Ignition Delay Times of Conventional (JP-8) and Synthetic (S-8) Jet Fuels: A Shock Tube Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
The global depletion of petroleum-based fuels has led the world to more closely examine alternate fuels. Therefore, alternate fuels produced from feedstocks such as coal, soybeans, palm oil or switch grass through methods such as coal liquefaction, biomass gasification, and Fischer-Tropsch synthesis have been tested. Among these techniques, fuels generated using Fischer-Tropsch technologies are of interest because they produce clean burning hydrocarbons similar to those found in commercial fuels. Therefore, in this study the Fischer-Tropsch derived S-8 fuel was evaluated as a drop-in replacement for the jet fuel JP-8. The jet fuel JP-8 is comprised of n-, iso- and cyclo- alkanes as well as aromatics while the S-8 fuel is primarily comprised of n- and iso- alkanes. The composition of the fuel affects its ignition characteristics chemically and physically by either advancement or delay of time to ignition. Since this study focused on the chemical effects, the fuels were completely pre-vaporized and pre-mixed. A high pressure, high temperature heated single pulse shock tube was used for this study. The shock tube is an established experimental tool used to obtain ignition delay data behind reflected shock waves under operating conditions relevant to modern engines. The experiments were conducted over a temperature range of 1000-1600 K, a pressure of 19±2 atm, equivalence ratios of 0.5, 1 and 3, within a dwell time of 7.6±0.2 ms and an argon dilution of 93% (v/v). Ignition delay times were measured using the signal from the pressure transducer on the end plate with guidance from the optical diagnostic signal. Along with JP-8 and S-8, the ignition delay of n-heptane was also studied. N-heptane was chosen to represent the n-alkanes in the fuels for this study since it was present in both fuels and also to prove the fact that the n-alkanes were rate controlling. The results indicate that both S-8 and JP-8 fuels have similar ignition delays at corresponding equivalence ratios. The fuel-rich mixtures ignited faster at lower temperatures (<1150 K) and the fuel-lean mixtures ignited faster at higher temperatures (>1150 K). In the transition period between lower to higher temperatures (~1100-1200 K), the equivalence ratio had no significant effect on the ignition delay time. The results also show that the ignition delay time measurements of S-8 and JP-8 fuels are similar to the ignition delay of n-heptane at the equivalence ratio of Φ=0.5 and thereby indicate that the n-alkanes present in these fuels controlled the ignition under these conditions. The ignition delay results of S-8 and JP-8 at Φ=3.0 from this study were also compared to prior work (Kahandawala et al., 2008) on 2-methylheptane and n-heptane/toluene (80/20 liquid vol.%), respectively and found to be indistinguishable. This data serves to extend the gas phase ignition delay database for both JP-8 and S-8 and is the first known data taken for both these fuels at higher temperatures (>1000 K) for an equivalence ratio of 3.0 with argon as the diluent gas.

Committee:

Sukh Sidhu, Dr (Committee Chair); Philip Taylor, Dr (Committee Member); Moshan Kahandawala, Dr (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Alternative Energy; Automotive Engineering; Automotive Materials; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Mechanical Engineering; Petroleum Engineering; Technology

Keywords:

Ignition delay; shock tube; S-8; JP-8; Jet fuels; Fuel characteristics; heated shock tube; Fischer-Tropsch; Alternate fuels; alkanes; synthetic fuel; fuel; iso-alkanes; jayakishan balagurunathan

Potratz, Christopher M.The Synthesis, Structure and Characterization of Extended Cobalt Ruthenium Carbonyl Compounds
Doctor of Philosophy, The Ohio State University, 2010, Chemistry

A series of extended heterotrimetallic compounds of the empirical formula [M(sol)x][CoRu3(CO)13] (M = Li, Na, K, Rb, Cs; sol = diethyl ether (Et2O), N, N-dimethylformamide (DMF), tetrahydrofuran (THF)) were synthesized and characterized using single crystal X-ray diffraction, solution IR and 13C NMR. Substitution of cost effective iron for ruthenium in the synthesis of [CoRu3(CO)13]- had limited success producing [CoFe3(CO)13]- in limited yield. Additionally the crystal structure of [Li(THF)4][CoFe3(CO)13] was collected but was too disordered to obtain a satisfactory refinement. Conversely the ratio of Co to Ru was successfully altered from 1:3 to 3:1 by synthesizing [Co3Ru(CO)12]-. The structure of {Na(THF)4Co3Ru(CO)12} was crystallized in good yield from THF and was compared with the structurally distinct {Na(THF)4CoRu3(CO)13} structure. A solvent dependent structural study of [K(18-crown-6)][Co(CO)4] and [K(18-crown-6)][CoRu3(CO)13] in Et2O, DMF and THF was also conducted. These series of compounds were found to contain isocarbonyl linkages and possess a variety of structural types including: solvent separated ion pairs, discrete molecules, a dimer, 1D polymeric chains, several 2D polymeric sheets and the first examples of isocarbonyl linked 3D polymeric extended arrays. These compounds are also the first examples of isocarbonyl linkages bridging three different metal elements. Additionally the first examples of a metal with a homoleptic isocarbonyl coordination environment were synthesized.

Yb[CoRu3(CO)13]2 was found to be too insoluble in Et2O to form the desired Ln-TM isocarbonyl compounds, thus the Cp ligand was utilized to increase solubility. Several synthetic routes to Cp2Yb(THF)xCoRu3(CO)13 were carried out leading to characterization and crystallization of unpublished structures for the intermediates: Cp2Yb(THF)2, Cp2Yb(THF)Cl, and [Cp2Yb(THF)2][Co(CO)4]. The desired product, Cp2Yb(THF)xCoRu3(CO)13, was successfully synthesized, however growth of X-ray quality crystals was unsuccessful.

Committee:

Sheldon Shore, PhD (Advisor); Pat Woodward, PhD (Committee Member); Malcolm Chisholm, PhD (Committee Member); David Williams, PhD (Committee Member)

Subjects:

Chemistry

Keywords:

alkali; alkaline earth; lanthanide; transition metal; isocarbonyls; Fischer-Tropsch; hydroformylation

Parker, Grant HoustonPyrolytic Decomposition of Synthetic Paraffinic Kerosene Fuel Compared to JP-7 and JP-8 Aviation Fuels
Master of Science (M.S.), University of Dayton, 2013, Chemical Engineering
Every generation of advanced military aircraft fly higher and faster than previous generations. With these leaps in performance, aircrafts develop enormous heat loads which can exceed aircraft material limitations. To relieve these heat loads, aircraft can utilize the endothermic heat sink capacity of jet fuel realized through pyrolytic decomposition. Improved understanding of the effect of fuel chemical composition on supercritical pyrolytic reactivity under conditions relevant to advanced aircraft operation can assist with the successful development of viable cooling methodologies. The goal of the current study was to compare the pyrolytic reactivity, primary decomposition products, and global reaction rates of fuels with varying chemical composition. A flowing reactor system was used to explore the pyrolytic chemistry of a Synthetic Paraffinic Kerosene (SPK) and specification jet fuels JP-8 and JP-7. The SPK was comprised solely of iso- and n-paraffins, with negligible cycloparaffin and aromatic content, while the specification fuels had chemical compositions consistent with typical petroleum-derived fuels. The pyrolytic studies were performed using stainless steel tube reactors which were 37.5 cm long and 0.5 mm inside diameter, with inlet flow rates of 0.2 to 0.6 mL/min at a pressure of 3.54 MPa. External reactor wall temperatures ranged from 500C to 650C. The liquid to gas conversion by mass was used as a metric for evaluating the pyrolytic reactivity due to the complex multicomponent composition of the test fuels. SPK averaged 45% higher conversion than JP-7 and 75% higher conversion than JP-8 at each respective temperature. All fuels followed similar reactivity trends with respect to controlling reaction chemistry, such as such as decomposition of long chain nparaffins, olefin formation, cycloparaffins formation, aromatic formation, and gas (e.g.,low molecular weight compound) production. Characterization of the relative reactivity of the fuels was performed by assuming the fuels decomposed via a first order, irreversible reaction pathway with respect to the gravimetric liquid to gas conversion. The calculated reaction rates and temperature data were used to develop Arrhenius plots which yielded the following kinetic perimeters: SPK--pre-exponential (A) factor of 2.3 x 10^12 s-1 and activation energy (Ea) of 223 kcal/mol, JP-7--A of 2.1 x 10^12 s-1 and Ea of 226 kcal/mol, and JP-8--A of 4.6 x 10^12 s-1 and Ea of 235 kcal/mol. These parameters can be used to estimate the initial reactivity and decomposition of these fuels under endothermic conditions. SPK fuels are more pyrolytically reactive compared to JP-7 and JP-8 using the liquid to gas conversion metric due to the variation in the neat chemical compositions. The mildly branched paraffins of the SPK with negligible cycloparaffins and aromatics, which can act as hydrogen donors reducing propagation rate, limited the reaction pathways resulting in a high liquid to gas conversion. JP-7 and JP-8 had a lower liquid to gas conversion due to the significantly higher initial concentrations of cycloparaffins and aromatics, thereby enabling these fuels to participate in a greater number of hydrogen donor reactions which lowers the extent of propagation reactions. Implications of these results can vary depending on the heat sink design and endothermic fuel cooling strategy. The propensity of SPK to react at lower temperature can enable SPK fuels to more readily reach the endothermic heating value. Unfortunately, a fuel with a higher pyrolytic reaction rate can also produce carbon deposition more readily. Further development into the design of a hypersonic heat exchanger system and the determination of the acceptable amount of liquid to gas conversion will dictate the optimal endothermic fuel.

Committee:

Matthew DeWitt (Advisor); Kevin Myers (Committee Member); Steven Zabarnick (Committee Member); Richard Striebich (Committee Member)

Subjects:

Aerospace Engineering; Alternative Energy; Chemical Engineering

Keywords:

pyrolysis, endothermic jet fuels, synthetic paraffinic kerosene, hypersonic, endothermic heat sink, pyrolytic decomposition, JP-7, fischer tropsch, FT