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Studies of cosolvent systems in supercritical ethane using solvated electrons.

Description: In this paper, pulse-radiolytic studies of the methanol-ethane cosolvent system are carried out. Our results show that at temperatures below approximately 110 C, there are high local concentrations of alcohols (clusters) that are capable of solvating an electron, suggesting a size of approximately 4-5 methanol molecules at approximately 0.15 mole fraction alcohol. Reactions have been carried out between these solvated electrons and silver ions that are (presumably) dissolved in other small clusters of alcohols. These results show that the reaction between species in two different clusters is approximately 2 orders of magnitude slower than diffusion-controlled reactions.
Date: November 14, 2000
Creator: Dimitrijevic, N. M.; Bartels, D. M.; Jonah, C. D. & Takahashi, K.
Partner: UNT Libraries Government Documents Department

Advanced Distillation Final Report

Description: The Advanced Distillation project was concluded on December 31, 2009. This U.S. Department of Energy (DOE) funded project was completed successfully and within budget during a timeline approved by DOE project managers, which included a one year extension to the initial ending date. The subject technology, Microchannel Process Technology (MPT) distillation, was expected to provide both capital and operating cost savings compared to conventional distillation technology. With efforts from Velocys and its project partners, MPT distillation was successfully demonstrated at a laboratory scale and its energy savings potential was calculated. While many objectives established at the beginning of the project were met, the project was only partially successful. At the conclusion, it appears that MPT distillation is not a good fit for the targeted separation of ethane and ethylene in large-scale ethylene production facilities, as greater advantages were seen for smaller scale distillations. Early in the project, work involved flowsheet analyses to discern the economic viability of ethane-ethylene MPT distillation and develop strategies for maximizing its impact on the economics of the process. This study confirmed that through modification to standard operating processes, MPT can enable net energy savings in excess of 20%. This advantage was used by ABB Lumus to determine the potential impact of MPT distillation on the ethane-ethylene market. The study indicated that a substantial market exists if the energy saving could be realized and if installed capital cost of MPT distillation was on par or less than conventional technology. Unfortunately, it was determined that the large number of MPT distillation units needed to perform ethane-ethylene separation for world-scale ethylene facilities, makes the targeted separation a poor fit for the technology in this application at the current state of manufacturing costs. Over the course of the project, distillation experiments were performed with the targeted mixture, ethane-ethylene, as ...
Date: March 24, 2010
Creator: Fanelli, Maddalena; Arora, Ravi; Tonkovich, Annalee; Marco, Jennifer & Rode, Ed
Partner: UNT Libraries Government Documents Department

DOE-GO-14154-1 OHIO FINAL report Velocys 30Sept08

Description: The overall goal of the OHIO project was to develop a commercially viable high intensity process to produce ethylene by controlled catalytic reaction of ethane with oxygen in a microchannel reactor. Microchannel technology provides a breakthrough solution to the challenges identified in earlier development work on catalytic ethane oxidation. Heat and mass transfer limitations at the catalyst surface create destructively high temperatures that are responsible for increased production of waste products (CO, CO2, and CH4). The OHIO project focused on microscale energy and mass transfer management, designed to alleviate these transport limitations, thereby improving catalyst selectivity and saving energy-rich feedstock. The OHIO project evaluated ethane oxidation in small scale microchannel laboratory reactors including catalyst test units, and full commercial length single- and multi-channel reactors. Small scale catalyst and single channel results met target values for ethylene yields, demonstrating that the microchannel concept improves mass and heat transport compared to conventional reactors and results in improved ethylene yield. Earlier economic sensitivity studies of ethane oxidation processes suggested that only modest improvements were necessary to provide a system that provides significant feedstock, energy, and capital benefits compared to conventional steam ethane cracking. The key benefit derived from the OHIO process is energy savings. Ethylene production consumes more energy than any other U.S. chemical process.1 The OHIO process offers improved feedstock utilization and substantial energy savings due to a novel reaction pathway and the unique abilities of microchannel process technology to control the reaction temperature and other critical process parameters. Based on projected economic benefits of the process, the potential energy savings could reach 150 trillion Btu/yr by the year 2020, which is the equivalent of over 25 million barrels of oil.
Date: September 30, 2008
Creator: Mazanec, Terry J.
Partner: UNT Libraries Government Documents Department

Effect of catalyst structure on oxidative dehydrogenation of ethane and propane on alumina-supported vanadia

Description: The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominantly as isolated monovanadate species below {approx}2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm2. The rate constant for oxidative dehydrogenation (k1) and its ratio with alkane and alkene combustion (k2/k1 and k3/k1, respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene formation rates (per V-atom) are {approx}8 times higher than ethene formation rates at a given reaction temperature, but the apparent ODH activation energies (E1) are similar for the two reactants and relatively insensitive to vanadia surface density. Ethene and propene formation rates (per V-atom) are strongly influenced by vanadia surface density and reach a maximum value at intermediate surface densities ({approx}8 V/nm2). The ratio of k2/k1 depends weakly on reaction temperature, indicating that activation energies for alkane combustion and ODH reactions are similar. The ratio of k2/k1 is independent of surface density for ethane, but increase slightly with vanadia surface density for propane, suggesting that isolated structures prevalent at low surface densities are slightly more selective for alkane dehydrogenation reactions. The ratio of k3/k1 decreases markedly with increasing reaction temperature for both ethane and propane ODH. Thus, the apparent activation energy for alkene combustion (E3) is much lower than that for alkane dehydrogenation (E1) and the difference between these two activation energies decreases with increasing surface density. The lower alkene selectivities observed at high vanadia surface densities are attributed to an increase in alkene adsorption enthalpies with increasing vanadia surface density. The highest yield of alkene is obtained for catalysts ...
Date: September 11, 2001
Creator: Argyle, Morris D.; Chen, Kaidong; Bell, Alexis T. & Iglesia, Enrique
Partner: UNT Libraries Government Documents Department

Hydrocarbon-free resonance transition 795-nm rubidium laser

Description: An optical resonance transition rubidium laser (5{sup 2}P{sub 1/2} {yields} 5{sup 2}S{sub 1/2}) is demonstrated with a hydrocarbon-free buffer gas. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. However, our experience suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our recent experimental results with a 'clean' helium-only buffer gas system pumped by a Ti:sapphire laser demonstrate all the advantages of the original alkali laser system, but without the reliability issues associated with the use of ethane.
Date: January 9, 2008
Creator: Wu, S Q; Soules, T F; Page, R H; Mitchell, S C; Kanz, V K & Beach, R J
Partner: UNT Libraries Government Documents Department


Description: Potassium, the reaction product of graphite with potassium, and the reaction product of irradiated graphite with potassium were subjected to hydrolysis. The gases evolved from the respective samples were analyzed mass spectroscopically. Hydrocarbons (methane and a trace of ethane) were found in the gas evolved from the irradiated graphite compound only, and the quantity was about that which would have been expected from the number of non-aggregated displaced atoms. The result was obtained for a single set of experiments and must be considered suggestive rather than conclusive. (auth)
Date: September 12, 1955
Creator: Primak, W.L. & Quarterman, L.A.
Partner: UNT Libraries Government Documents Department

Structure sensitive adsorption of hydrogen on ruthenium and ruthenium-silver catalysts supported on silica

Description: Supported metal catalysts typically consist of particles with sizes less than 10 nm, and because of the small crystallite size, low coordination number sites (edges and corners) represent a significant fraction of all surface sites. Furthermore, it has been demonstrated that adsorption rates can be much greater at these low coordination sites than on basal plane sites. What has not been generally appreciated, however, is that preferential adsorption at edge and corner sites may explain the mechanism by which a promoter, or the addition of a second metal to form a bimetallic, can alter the selectivity and rate of reaction. For example, the measurements of hydrogen adsorption onto supported Ru-Ag catalysts show marked decreases in the amount of hydrogen adsorbed relative to the amount adsorbed on Ru catalysts. Although it is known that Ag does not dissociatively adsorb hydrogen, this decrease cannot be explained by a simple one-to-one site blocking mechanism unless Ag preferentially populates edges and corners, thereby reducing the number of Ru edge sites. Indeed, Monte Carlo simulations of Ru-Group IB metal catalysts predict that Group IB metal atoms preferentially populate corner and edge sites of ruthenium crystals. This evidence, taken together, suggests that adsorption occurs preferentially at Ru corner and edge sites, which act as portals onto basal planes. A model based on this portal theory for hydrogen adsorption onto supported ruthenium bimetallic catalysts has been developed using a rate equation approach. Specifically, the model accounts for the following features: (1) preferential adsorption through portals, (2) basal plane site-energy multiplicity, and (3) hydrogen spillover onto the support. A comparison of model predictions with experiment is presented for different concentration of Ag in Ru-Ag catalysts. The portal model of hydrogen adsorption can explain the observed decreased in the amount of hydrogen adsorbed on Ru-Ag catalysts. The model can ...
Date: February 12, 1999
Creator: Kumar, N.
Partner: UNT Libraries Government Documents Department

Aggregation of dialkyl-substituted diphosphonic acids and its effect on metal ion extraction.

Description: Solvent extraction reagents containing the diphosphonic acid group exhibit an extraordinary affinity for tri-, tetra- and hexavalent actinides. Their use has been considered for actinide separation and pre-concentration procedures. Solvent extraction data obtained with P,P{prime}-di(2-ethylhexyl) methane-, ethane- and butanediphosphonic acids exhibit features that are difficult to explain without Knowledge of the aggregation state of the extractants. Information about the aggregation of the dialkyl-substituted diphosphonic acids in aromatic diluents has been obtained using the complementary techniques of vapor pressure osmometry (VPO), small angle neutron scattering (SANS), infrared spectroscopy and molecular mechanics. The results from these techniques provide an understanding of the aggregation behavior of these extractants that is fully compatible with the solvent extraction data. The most important results and their relevance to solvent extraction are reviewed in this paper.
Date: October 22, 1999
Creator: Chiarizia, R.; Barrans, R. E., Jr.; Ferraro, J. R. Herlinger, A. W. & McAlister, D. R.
Partner: UNT Libraries Government Documents Department

Solvated electrons formed in methanol cluster in ethane

Description: The authors have studied the spectral shift of the solvated electron in MeOH/C{sub 2}H{sub 6} mixture using pulse radiolysis. The solvated electrons were formed by ionizing the solution. The spectral shift can be explained in terms of MeOH cluster size formed in the solution. With increasing temperature at constant mole fraction of MeOH, the spectral maximum shifts toward low energy. The width at red side increased with increasing temperature, however, there is no significant changes in the blue side of the spectra with temperature.
Date: March 9, 2000
Creator: Takahashi, K.; Bartels, D. M.; Jonah, C. D. & Dimitrijevic, N. A.
Partner: UNT Libraries Government Documents Department

Friction and wear performance of diamondlike carbon films grown in various source gas plasmas

Description: In this study, the authors investigated the effects of various source gases (methane, ethane, ethylene, and acetylene) on the friction and wear performance of diamondlike carbon (DLC) films prepared in a plasma enhanced chemical vapor deposition (PECVD) system. Films were deposited on AISI H13 steel substrates and tested in a pin-on-disk machine against DLC-coated M50 balls in dry nitrogen. They found a close correlation between friction coefficient and source gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios exhibited lower friction coefficients and higher wear resistance than films grown in source gases with lower hydrogen-to-carbon (H/C) ratios. The lowest friction coefficient (0.014) was achieved with a film derived from methane with an WC ratio of 4, whereas the coefficient of films derived from acetylene (H/C = 1) was of 0.15. Similar correlations were observed for wear rates. Specifically, films derived from gases with lower H/C values were worn out and the substrate material was exposed, whereas films from methane and ethane remained intact and wore at rates that were nearly two orders of magnitude lower than films obtained from acetylene.
Date: January 18, 2000
Creator: Erdemir, A.; Nilufer, I. B.; Eryilmaz, O. L.; Beschliesser, M. & Fenske, G. R.
Partner: UNT Libraries Government Documents Department

Ab initio and density functional studies of hydrocarbon adsorption in zeolites.

Description: The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms and have found equilibrium structures for complexes of methane, ethane, and propane with an acid site. If a large enough cluster is used and correlation effects are included via perturbation theory, the calculated adsorption energy for ethane is about 5 kcal/mol compared with the experimental value of 7.5 kcal/mol. The B3LYP density functional method gives a much smaller binding of {approximately}1 kcal/mol for ethane. The reason for the failure of density fictional theory is unclear.
Date: August 21, 1998
Creator: Curtiss, L. A.
Partner: UNT Libraries Government Documents Department

A computational study of ethane cracking in cluster models of zeolite H-ZSM-5.

Description: Protolytic cracking of ethane by zeolites has been studied using quantum-chemical techniques and a cluster model of the zeolite Broensted acid site. Previous computational studies have utilized small cluster models and have not accounted for the long-range effects of the zeolite lattice. These studies have found reaction barriers for cracking which are significantly higher than experimental values. In this work we used a larger zeolite cluster model containing five tetrahedral (Si, Al) atoms (denoted 5T) and searched for stationary points along one possible reaction path for cracking at the HF/6-31 G(d) level of theory. This path involves a multi-step cracking reaction, in which the proton is first transferred from the acid site to the adsorbed ethane molecule to form an ion-pair equilibrium complex. Subsequently the proton attacks the C-C bond to complete the cracking process. The activation barrier for cracking was calculated, including corrections for (i) vibrational energies at the experimental reaction temperature of 773 K; (ii) electron correlation and an extended basis set at the B3LYP/6-311+G(3df,2p) level; and (iii) the influence of the surrounding zeolite lattice in H-ZSM-5. The barrier we obtain, 53 {+-} 5 kcal/mol, is significantly smaller than previous theoretical results and is in good agreement with typical experimental values for small hydrocarbons. Work is currently in progress to extend this study by carrying out geometry optimization of these complexes using the B3LYP method of density functional theory.
Date: August 21, 1998
Creator: Zygmunt, S. A.
Partner: UNT Libraries Government Documents Department

Investigation on the Flame Extinction Limit of Fuel Blends

Description: Lean flame extinction limits of binary fuel mixtures of methane (CH{sub 4}), propane (C{sub 3}H{sub 8}), and ethane (C{sub 2}H{sub 6}) were measured using a twin-flame counter-flow burner. Experiments were conducted to generate an extinction equivalence ratio vs. global stretch rate plot and an extrapolation method was used to calculate the equivalence ratio corresponding to an experimentally unattainable zero-stretch condition. The foregoing gases were selected because they are the primary constitutes of natural gas, which is the primary focus of the present study. To validate the experimental setup and methodology, the flame extinction limit of pure fuels at zero stretch conditions were also estimated and compared with published values. The lean flame extinction limits of methane (f{sub ext} = 4.6%) and propane (f{sub ext} = 2.25%) flames measured in the present study agreed with the values reported in the literature. It was observed that the flame extinction limit of fuel blends have a polynomial relation with the concentration of component fuels in the mixture. This behavior contradicts with the commonly used linear Le Chatelier's approximation. The experimentally determined polynomial relations between the flame extinction limits of fuel blends (i.e. methane-propane and methane-ethane) and methane concentration are as follows: (1) Methane-Propane--%f{sub ext} = (1.05 x 10{sup -9}) f{sup 5}-(1.3644 x 10{sup -7}) f{sup 4}+(6.40299 x 10{sup -6}) f{sup 3}-(1.2108459 x 10{sup -4}) f{sup 2}+(2.87305329 x 10{sup -3}) f+2.2483; (2) Methane-Ethane--%f{sub ext} = (2.1 x 10{sup -9})f{sup 5}-(3.5752 x 10{sup -7}) f{sup 4}+(2.095425 x 10{sup -5}) f{sup 3}-(5.037353 x 10{sup -4}) f{sup 2} + 6.08980409 f + 2.8923. Where f{sub ext} is the extinction limits of methane-propane and methane-ethane fuel blends, and f is the concentration (% volume) of methane in the fuel mixture. The relations were obtained by fitting fifth order curve (polynomial regression) to experimentally measured extinction limits at different ...
Date: February 1, 2005
Creator: Choudhuri, Ahsan R.
Partner: UNT Libraries Government Documents Department


Description: Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The scope of the work involved designing and developing an airborne, optical remote sensor capable of sensing methane and, if possible, ethane for the detection of natural gas pipeline leaks. Flight testing using a custom dual wavelength, high power fiber amplifier was initiated in February 2005. Ophir successfully demonstrated the airborne system, showing that it was capable of discerning small amounts of methane from a simulated pipeline leak. Leak rates as low as 150 standard cubic feet per hour (scf/h) were detected by the airborne sensor.
Date: April 15, 2005
Creator: Myers, Jerry
Partner: UNT Libraries Government Documents Department

Low Cost Chemical Feedstocks Using an Improved and Energy Efficient Natural Gas Liquid (NGL) Removal Process, Final Technical Report

Description: The overall objective of this project is to develop a new low-cost and energy efficient Natural Gas Liquid (NGL) recovery process - through a combination of theoretical, bench-scale and pilot-scale testing - so that it could be offered to the natural gas industry for commercialization. The new process, known as the IROA process, is based on U.S. patent No. 6,553,784, which if commercialized, has the potential of achieving substantial energy savings compared to currently used cryogenic technology. When successfully developed, this technology will benefit the petrochemical industry, which uses NGL as feedstocks, and will also benefit other chemical industries that utilize gas-liquid separation and distillation under similar operating conditions. Specific goals and objectives of the overall program include: (i) collecting relevant physical property and Vapor Liquid Equilibrium (VLE) data for the design and evaluation of the new technology, (ii) solving critical R&D issues including the identification of suitable dehydration and NGL absorbing solvents, inhibiting corrosion, and specifying proper packing structure and materials, (iii) designing, construction and operation of bench and pilot-scale units to verify design performance, (iv) computer simulation of the process using commercial software simulation platforms such as Aspen-Plus and HYSYS, and (v) preparation of a commercialization plan and identification of industrial partners that are interested in utilizing the new technology. NGL is a collective term for C2+ hydrocarbons present in the natural gas. Historically, the commercial value of the separated NGL components has been greater than the thermal value of these liquids in the gas. The revenue derived from extracting NGLs is crucial to ensuring the overall profitability of the domestic natural gas production industry and therefore of ensuring a secure and reliable supply in the 48 contiguous states. However, rising natural gas prices have dramatically reduced the economic incentive to extract NGLs from domestically produced natural gas. ...
Date: August 10, 2012
Creator: Meyer, Howard, S. & Lu, Yingzhong
Partner: UNT Libraries Government Documents Department

Scaling Relationships for Adsorption Energies of C2 Hydrocarbons on Transition Metal Surfaces

Description: Using density functional theory calculations we show that the adsorption energies for C{sub 2}H{sub x}-type adsorbates on transition metal surfaces scale with each other according to a simple bond order conservation model. This observation generalizes some recently recognized adsorption energy scaling laws for AH{sub x}-type adsorbates to unsaturated hydrocarbons and establishes a coherent simplified description of saturated as well as unsaturated hydrocarbons adsorbed on transition metal surfaces. A number of potential applications are discussed. We apply the model to the dehydrogenation of ethane over pure transition metal catalysts. Comparison with the corresponding full density functional theory calculations shows excellent agreement.
Date: August 18, 2011
Creator: Jones, G
Partner: UNT Libraries Government Documents Department

Processing of Uranium Carbide Reactor Fuels. I. Reaction With Water and HCl

Description: High-purity uranium monocarbide reacted with water at 80 deg C to produce a finely divided, brown U(IV) compound, and 92 nfl (STP) of gas per gram consisting of 11 vol% hydrogen, 86 vol% methane, 2 vol% ethame, and 0.6 vol% propane. At 90 deg C, the products were the same, but the reaction rate was higher. Reaction with 5.6 M HCl was slower than with water, but the gaseous products were essentially the same. In preliminary experiments at 80 deg C with UC-UC/sub 2/ mixtures containing less than 2 wt.% free carbon, the volume of gas evolved per gram of sample hydrolyzed decreased from 92 to 32 ml (STP) and the methane concentration from 86 to 14 vol% as the UC/sub 2/ concentration in the mixture increased from 0 to about 63 wt.%. An attendant increase in the hydrogen and ethane concentrations to 23 and 38 vol%, respectively, also occurred. (anth)
Date: August 15, 1961
Creator: Bradley, M. J. & Ferris, L. M.
Partner: UNT Libraries Government Documents Department

Behavior of excess electrons in supercritical fluids -- Electron attachment

Description: The behavior of excess electrons in supercritical ethane was investigated by measuring mobility and reaction rates. Mobilities wee measured by means of a time-of-flight method at 306--320 K as a function of pressure. Mobility values decreased at all temperatures with increasing pressure, but showed a small minimum or a shoulder at the pressure where the compressibility {chi}{sub T} has a peak. Electron attachment to CO{sub 2}, NO, pyrimidine and C{sub 2}F{sub 4} over the same temperature range was studied as a function of pressure. Both attachment rate constants k{sub a} for NO and C{sub 2}F{sub 4}, and equilibrium constants K({double_bond}k{sub a}/k{sub d}) for CO{sub 2} and pyrimidine increased sharply at pressures of {chi}{sub T} peaks. Activation volumes V{sub a}* and reaction volumes {Delta}V{sub r} are very large and negative in the critical region. The volume change is mainly due to electrostriction around ions formed. The results are compared to volume changes predicted by a compressible continuum model.
Date: July 1, 1999
Creator: Nishikawa, Masaru; Holroyd, R.A. & Itoh, Kengo
Partner: UNT Libraries Government Documents Department