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Sample records for catalytic ozonation-biological coupled

  1. Direct catalytic cross-coupling of organolithium compounds

    NASA Astrophysics Data System (ADS)

    Giannerini, Massimo; Fañanás-Mastral, Martín; Feringa, Ben L.

    2013-08-01

    Catalytic carbon-carbon bond formation based on cross-coupling reactions plays a central role in the production of natural products, pharmaceuticals, agrochemicals and organic materials. Coupling reactions of a variety of organometallic reagents and organic halides have changed the face of modern synthetic chemistry. However, the high reactivity and poor selectivity of common organolithium reagents have largely prohibited their use as a viable partner in direct catalytic cross-coupling. Here we report that in the presence of a Pd-phosphine catalyst, a wide range of alkyl-, aryl- and heteroaryl-lithium reagents undergo selective cross-coupling with aryl- and alkenyl-bromides. The process proceeds quickly under mild conditions (room temperature) and avoids the notorious lithium halogen exchange and homocoupling. The preparation of key alkyl-, aryl- and heterobiaryl intermediates reported here highlights the potential of these cross-coupling reactions for medicinal chemistry and material science.

  2. Catalytic migratory oxidative coupling of nitrones.

    PubMed

    Hashizume, Shogo; Oisaki, Kounosuke; Kanai, Motomu

    2011-08-19

    A Cu(I)-catalyzed migratory oxidative coupling between nitrones and heterocycles or a methylamine is described. Selective C-C bond-formation proceeds through cleavage of two C(sp(3))-H bonds concomitant with C═N double bond-migration. The reaction provides an alternating nitrone moiety, allowing for further synthetically useful transformations. Radical clock studies suggest that the nucleophilic addition of nitrones to an oxidatively generated carbocation is a key step. PMID:21766802

  3. A Practical and Catalytic Reductive Olefin Coupling

    PubMed Central

    2015-01-01

    A redox-economic method for the direct coupling of olefins that uses an inexpensive iron catalyst and a silane reducing agent is reported. Thus, unactivated olefins can be joined directly to electron-deficient olefins in both intra- and intermolecular settings to generate hindered bicyclic systems, vicinal quaternary centers, and even cyclopropanes in good yield. The reaction is not sensitive to oxygen or moisture and has been performed on gram-scale. Most importantly, it allows access to many compounds that would be difficult or perhaps impossible to access using other methods. PMID:24428607

  4. Catalytic bismetallative multicomponent coupling reactions: scope, applications, and mechanisms.

    PubMed

    Cho, Hee Yeon; Morken, James P

    2014-07-01

    Catalytic reactions have played an indispensable role in organic chemistry for the last several decades. In particular, catalytic multicomponent reactions have attracted significant attention due to their efficiency and expediency towards complex molecule synthesis. The presence of bismetallic reagents (e.g. B-B, Si-Si, B-Si, Si-Sn, etc.) in this process renders the products enriched with various functional groups and multiple stereocenters. For this reason, catalytic bismetallative coupling is considered an effective method to generate the functional and stereochemical complexity of simple hydrocarbon substrates. This review highlights key developments of transition-metal catalyzed bismetallative reactions involving multiple π components. Specifically, it will highlight the scope, synthetic applications, and proposed mechanistic pathways of this process.

  5. Catalytic bismetallative multicomponent coupling reactions: scope, applications, and mechanisms

    PubMed Central

    Cho, Hee Yeon

    2014-01-01

    Catalytic reactions have played an indispensable role in organic chemistry for the last several decades. In particular, catalytic multicomponent reactions have attracted a lot of attention due to their efficiency and expediency towards complex molecule synthesis. The presence of bismetallic reagents (e.g. B–B, Si–Si, B–Si, Si–Sn, etc.) in this process renders the products enriched with various functional groups and multiple stereocenters. For this reason, catalytic bismetallative coupling is considered an effective method to generate the functional and stereochemical complexity of simple hydrocarbon substrates. This review highlights key developments of transition-metal catalyzed bismetallative reactions involving multiple π components. Specifically, it will highlight the scope, synthetic applications, and proposed mechanistic pathways of this process. PMID:24736839

  6. Real time chemical imaging of a working catalytic membrane reactor during oxidative coupling of methane.

    PubMed

    Vamvakeros, A; Jacques, S D M; Middelkoop, V; Di Michiel, M; Egan, C K; Ismagilov, I Z; Vaughan, G B M; Gallucci, F; van Sint Annaland, M; Shearing, P R; Cernik, R J; Beale, A M

    2015-08-18

    We report the results from an operando XRD-CT study of a working catalytic membrane reactor for the oxidative coupling of methane. These results reveal the importance of the evolving solid state chemistry during catalytic reaction, particularly the chemical interaction between the catalyst and the oxygen transport membrane.

  7. Studies of coupled chemical and catalytic coal conversion methods

    SciTech Connect

    Stock, L.M.

    1990-01-01

    This report concerns our research on base-catalyzed coal solubilization and a new approach for hydrogen addition. The work on base-catalyzed, chemical solubilization is continuing. this report is focused on the hydrogenation research. Specifically it deals with the use of arene chromium carbonyl complexes as reagents for the addition of dideuterium to coal molecules. In one phase of the work, he has established that the aromatic hydrocarbons in a representative coal liquid can be converted in very good yield to arene chromium carbonyl compounds. In a second phase of the work directly related to our objective of improved methods for catalytic hydrogenation, he has established that the aromatic constituents of the same coal liquid add dideuterium in the presence of added napththalene chromium carbonyl.

  8. Studies of coupled chemical and catalytic coal conversion methods

    SciTech Connect

    Stock, L.M.; Chatterjee, K.; Cheng, C.; Ettinger, M.; Flores, F.; Jiralerspong, S.; Miyake, M.; Muntean, J.

    1991-12-01

    The objective of this research was to convert coal into a soluble substance under mild conditions. The strategy involved two steps, first to breakdown the macromolecular network of coal, and second to add hydrogen catalytically. We investigated different basic reagents that could, in priciple, break down coal`s structure and alkylation strategies that might enhance its solubility. We examined O- and C-alkylation, the importance of the strength of the base, the character of the added alkyl groups and other reaction parameters. This work provided new information concerning the way in which hydrogen bonding, polarization interactions between aromatic structures and covalent bonding could be disrupted and solubility enhanced. The objective of our research was to explore new organochromium chemistry that might be feasible for the hydrogenation of coal under mild conditions.

  9. Studies of coupled chemical and catalytic coal conversion methods

    SciTech Connect

    Stock, L.M.; Chatterjee, K.; Cheng, C.; Ettinger, M.; Flores, F.; Jiralerspong, S.; Miyake, M.; Muntean, J.

    1991-12-01

    The objective of this research was to convert coal into a soluble substance under mild conditions. The strategy involved two steps, first to breakdown the macromolecular network of coal, and second to add hydrogen catalytically. We investigated different basic reagents that could, in priciple, break down coal's structure and alkylation strategies that might enhance its solubility. We examined O- and C-alkylation, the importance of the strength of the base, the character of the added alkyl groups and other reaction parameters. This work provided new information concerning the way in which hydrogen bonding, polarization interactions between aromatic structures and covalent bonding could be disrupted and solubility enhanced. The objective of our research was to explore new organochromium chemistry that might be feasible for the hydrogenation of coal under mild conditions.

  10. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer

    PubMed Central

    2015-01-01

    Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups. PMID:26439818

  11. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer.

    PubMed

    Miller, David C; Choi, Gilbert J; Orbe, Hudson S; Knowles, Robert R

    2015-10-28

    Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups.

  12. Quantum chemical study of the catalytic oxidative coupling of methane

    SciTech Connect

    Onal, I.; Senkan, S.

    1997-10-01

    Oxidative coupling of methane reaction pathways on MgO and lithium-modified MgO were theoretically studied using the semiempirical MNDO-PM3 molecular orbital method. The surface of the MgO catalyst was modeled by a Mg{sub 9}O{sub 9} molecular cluster containing structural defects such as edges and corners. Lithium-promoted magnesia was simulated by isomorphic substitution of Mg{sup 2+} by Li{sup +}; the excess negative charge of the cluster was compensated by a proton connected to a neighboring O{sup 2{minus}} site. Heterolytic adsorption of methane was found to be directly related to the coordination number of both the lattice oxygen and the metal sites. Energetically the most favorable site pair was Mg{sub 3c}-O{sub 3c} with a neighboring Li{sub 4c} site present. Various sequential oxygen and methane adsorption pathways were explored resulting in CH{sub 3}OH formation with lower energy barriers for the Li-modified MgO cluster as compared to unmodified MgO.

  13. Spatially coupled catalytic ignition of CO oxidation on Pt: mesoscopic versus nano-scale

    PubMed Central

    Spiel, C.; Vogel, D.; Schlögl, R.; Rupprechter, G.; Suchorski, Y.

    2015-01-01

    Spatial coupling during catalytic ignition of CO oxidation on μm-sized Pt(hkl) domains of a polycrystalline Pt foil has been studied in situ by PEEM (photoemission electron microscopy) in the 10−5 mbar pressure range. The same reaction has been examined under similar conditions by FIM (field ion microscopy) on nm-sized Pt(hkl) facets of a Pt nanotip. Proper orthogonal decomposition (POD) of the digitized FIM images has been employed to analyze spatiotemporal dynamics of catalytic ignition. The results show the essential role of the sample size and of the morphology of the domain (facet) boundary in the spatial coupling in CO oxidation. PMID:26021411

  14. Catalytic partial oxidation coupled with membrane purification to improve resource and energy efficiency in syngas production.

    PubMed

    Iaquaniello, G; Salladini, A; Palo, E; Centi, G

    2015-02-01

    Catalytic partial oxidation coupled with membrane purification is a new process scheme to improve resource and energy efficiency in a well-established and large scale-process like syngas production. Experimentation in a semi industrial-scale unit (20 Nm(3)  h(-1) production) shows that a novel syngas production scheme based on a pre-reforming stage followed by a membrane for hydrogen separation, a catalytic partial oxidation step, and a further step of syngas purification by membrane allows the oxygen-to-carbon ratio to be decreased while maintaining levels of feed conversion. For a total feed conversion of 40 %, for example, the integrated novel architecture reduces oxygen consumption by over 50 %, with thus a corresponding improvement in resource efficiency and an improved energy efficiency and economics, these factors largely depending on the air separation stage used to produce pure oxygen.

  15. Catalytic partial oxidation coupled with membrane purification to improve resource and energy efficiency in syngas production.

    PubMed

    Iaquaniello, G; Salladini, A; Palo, E; Centi, G

    2015-02-01

    Catalytic partial oxidation coupled with membrane purification is a new process scheme to improve resource and energy efficiency in a well-established and large scale-process like syngas production. Experimentation in a semi industrial-scale unit (20 Nm(3)  h(-1) production) shows that a novel syngas production scheme based on a pre-reforming stage followed by a membrane for hydrogen separation, a catalytic partial oxidation step, and a further step of syngas purification by membrane allows the oxygen-to-carbon ratio to be decreased while maintaining levels of feed conversion. For a total feed conversion of 40 %, for example, the integrated novel architecture reduces oxygen consumption by over 50 %, with thus a corresponding improvement in resource efficiency and an improved energy efficiency and economics, these factors largely depending on the air separation stage used to produce pure oxygen. PMID:25571881

  16. Coupling of downstream RNA polymerase-promoter interactions with formation of catalytically competent transcription initiation complex

    PubMed Central

    Mekler, Vladimir; Minakhin, Leonid; Borukhov, Sergei; Mustaev, Arkady; Severinov, Konstantin

    2014-01-01

    Bacterial RNA polymerase (RNAP) makes extensive contacts with duplex DNA downstream of the transcription bubble in initiation and elongation complexes. We investigated the role of downstream interactions in formation of catalytically competent transcription initiation complex by measuring initiation activity of stable RNAP complexes with model promoter DNA fragments whose downstream ends extend from +3 to +21 relative to the transcription start site at +1. We found that DNA downstream of position +6 does not play a significant role in transcription initiation when RNAP-promoter interactions upstream of the transcription start site are strong and promoter melting region is AT-rich. Further shortening of downstream DNA dramatically reduces efficiency of transcription initiation. The boundary of minimal downstream DNA duplex needed for efficient transcription initiation shifted further away from the catalytic center upon increasing the GC content of promoter melting region or in the presence of bacterial stringent response regulators DksA and ppGpp. These results indicate that the strength of RNAP-downstream DNA interactions has to reach a certain threshold to retain the catalytically competent conformation of the initiation complex and that establishment of contacts between RNAP and downstream DNA can be coupled with promoter melting. The data further suggest that RNAP interactions with DNA immediately downstream of the transcription bubble are particularly important for initiation of transcription. We hypothesize that these active center-proximal contacts stabilize the DNA template strand in the active center cleft and/or position the RNAP clamp domain to allow RNA synthesis. PMID:25311862

  17. Enzyme as catalytic wheel powered by a Markovian engine: conformational coupling and barrier surfing models

    NASA Astrophysics Data System (ADS)

    Tsong, Tian Yow; Chang, Cheng-Hung

    2005-05-01

    We examine a typical Michaelis-Menten Enzyme (MME) and redress it to form a transducer of free energy, and electric, acoustic, or other types of energy. This amendment and extension is necessary in lieu of recent experiments in which enzymes are shown to perform pump, motor, and locomotion functions resembling their macroscopic counterparts. Classical textbook depicts enzyme, or an MME, as biocatalyst which can enhance the rate of a chemical reaction by lowering the activation barrier but cannot shift the thermodynamic equilibrium of the biochemical reaction. An energy transducer, on the other hand, must also be able to harvest, store, or divert energy and in doing so alter the chemical equilibrium, change the energy form, fuel an energy consuming process, or perform all these functions stepwise in one catalytic turnover. The catalytic wheel presented in this communication is both a catalyst and an energy transducer and can perform all these tasks with ease. A Conformational Coupling Model for the rotary motors and a Barrier Surfing Model for the track-guided stepping motors and transporters, are presented and compared. It is shown that the core engine of the catalytic wheel, or a Brownian motor, is a Markovian engine. It remains to be seen if this core engine is the basic mechanism for a wide variety of bio-molecular energy transducers, as well as certain other dynamic systems, for example, the Parrondo's Games.

  18. Electronic Coupling and Catalytic Effect on H2 Evolution of MoS2/Graphene Nanocatalyst

    PubMed Central

    Liao, Ting; Sun, Ziqi; Sun, Chenghua; Dou, Shi Xue; Searles, Debra J.

    2014-01-01

    Inorganic nano-graphene hybrid materials that are strongly coupled via chemical bonding usually present superior electrochemical performance. However, how the chemical bond forms and the synergistic catalytic mechanism remain fundamental questions. In this study, the chemical bonding of the MoS2 nanolayer supported on vacancy mediated graphene and the hydrogen evolution reaction of this nanocatalyst system were investigated. An obvious reduction of the metallic state of the MoS2 nanolayer is noticed as electrons are transferred to form a strong contact with the reduced graphene support. The missing metallic state associated with the unsaturated atoms at the peripheral sites in turn modifies the hydrogen evolution activity. The easiest evolution path is from the Mo edge sites, with the presence of the graphene resulting in a decrease in the energy barrier from 0.17 to 0.11 eV. Evolution of H2 from the S edge becomes more difficult due to an increase in the energy barrier from 0.43 to 0.84 eV. The clarification of the chemical bonding and catalytic mechanisms for hydrogen evolution using this strongly coupled MoS2/graphene nanocatalyst provide a valuable source of reference and motivation for further investigation for improved hydrogen evolution using chemically active nanocoupled systems. PMID:25174324

  19. Promotion of enzyme flexibility by dephosphorylation and coupling to the catalytic mechanism of a phosphohexomutase.

    PubMed

    Lee, Yingying; Villar, Maria T; Artigues, Antonio; Beamer, Lesa J

    2014-02-21

    The enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) from Pseudomonas aeruginosa catalyzes an intramolecular phosphoryl transfer across its phosphosugar substrates, which are precursors in the synthesis of exoproducts involved in bacterial virulence. Previous structural studies of PMM/PGM have established a key role for conformational change in its multistep reaction, which requires a dramatic 180° reorientation of the intermediate within the active site. Here hydrogen-deuterium exchange by mass spectrometry and small angle x-ray scattering were used to probe the conformational flexibility of different forms of PMM/PGM in solution, including its active, phosphorylated state and the unphosphorylated state that occurs transiently during the catalytic cycle. In addition, the effects of ligand binding were assessed through use of a substrate analog. We found that both phosphorylation and binding of ligand produce significant effects on deuterium incorporation. Phosphorylation of the conserved catalytic serine has broad effects on residues in multiple domains and is supported by small angle x-ray scattering data showing that the unphosphorylated enzyme is less compact in solution. The effects of ligand binding are generally manifested near the active site cleft and at a domain interface that is a site of conformational change. These results suggest that dephosphorylation of the enzyme may play two critical functional roles: a direct role in the chemical step of phosphoryl transfer and secondly through propagation of structural flexibility. We propose a model whereby increased enzyme flexibility facilitates the reorientation of the reaction intermediate, coupling changes in structural dynamics with the unique catalytic mechanism of this enzyme.

  20. Rate turnover in mechano-catalytic coupling: A model and its microscopic origin

    SciTech Connect

    Roy, Mahua; Grazioli, Gianmarc; Andricioaei, Ioan

    2015-07-28

    A novel aspect in the area of mechano-chemistry concerns the effect of external forces on enzyme activity, i.e., the existence of mechano-catalytic coupling. Recent experiments on enzyme-catalyzed disulphide bond reduction in proteins under the effect of a force applied on the termini of the protein substrate reveal an unexpected biphasic force dependence for the bond cleavage rate. Here, using atomistic molecular dynamics simulations combined with Smoluchowski theory, we propose a model for this behavior. For a broad range of forces and systems, the model reproduces the experimentally observed rates by solving a reaction-diffusion equation for a “protein coordinate” diffusing in a force-dependent effective potential. The atomistic simulations are used to compute, from first principles, the parameters of the model via a quasiharmonic analysis. Additionally, the simulations are also used to provide details about the microscopic degrees of freedom that are important for the underlying mechano-catalysis.

  1. Catalytic asymmetric reductive coupling of alkynes and aldehydes: enantioselective synthesis of allylic alcohols and alpha-hydroxy ketones.

    PubMed

    Miller, Karen M; Huang, Wei-Sheng; Jamison, Timothy F

    2003-03-26

    A highly enantioselective method for catalytic reductive coupling of alkynes and aldehydes is described. Allylic alcohols are afforded with complete E/Z selectivity, generally >95:5 regioselectivity, and in up to 96% ee. In conjunction with ozonolysis, this process is complementary to existing methods of enantioselective alpha-hydroxy ketone synthesis. PMID:12643701

  2. Mechanistic Studies of Gold and Palladium Cooperative Dual-Catalytic Cross-Coupling Systems

    PubMed Central

    Al-Amin, Mohammad; Roth, Katrina E.; Blum, Suzanne A.

    2014-01-01

    Double-label crossover, modified-substrate, and catalyst comparison experiments in the gold and palladium dual-catalytic rearrangement/cross-coupling of allenoates were performed in order to probe the mechanism of this reaction. The results are consistent with a cooperative catalysis mechanism whereby 1) gold activates the substrate prior to oxidative addition by palladium, 2) gold acts as a carbophilic rather than oxophilic Lewis acid, 3) competing olefin isomerization is avoided, 4) gold participates beyond the first turnover and therefore does not serve simply to generate the active palladium catalyst, and 5) single-electron transfer is not involved. These experiments further demonstrate that the cooperativity of both gold and palladium in the reaction is essential because significantly lower to zero conversion is achieved with either metal alone in comparison studies that examined multiple potential gold, palladium, and silver catalysts and precatalysts. Notably, employment of the optimized cocatalysts, PPh3AuOTf and Pd2dba3, separately (i.e., only Au or only Pd) results in zero conversion to product at all monitored time points compared to quantitative conversion to product when both are present in cocatalytic reactions. PMID:24757581

  3. Application of integrated ozone biological aerated filters and membrane filtration in water reuse of textile effluents.

    PubMed

    He, Yaozhong; Wang, Xiaojun; Xu, Jinling; Yan, Jinli; Ge, Qilong; Gu, Xiaoyang; Jian, Lei

    2013-04-01

    A combined process including integrated ozone-BAFs (ozone biological aerated filters) and membrane filtration was first applied for recycling textile effluents in a cotton textile mill with capacity of 5000 m(3)/d. Influent COD (chemical oxygen demand) in the range of 82-120 mg/L, BOD5 (5-day biochemical oxygen demand) of 12.6-23.1 mg/L, suspended solids (SSs) of 38-52 mg/L and color of 32-64° were observed during operation. Outflows with COD≤45 mg/L, BOD5≤7.6 mg/L, SS≤15 mg/L, color≤8° were obtained after being decontaminated by ozone-BAF with ozone dosage of 20-25 mg/L. Besides, the average removal rates of PVA (polyvinyl alcohol) and UV254 were 100% and 73.4% respectively. Permeate water produced by RO (reverse osmosis) could be reused in dyeing and finishing processes, while the RO concentrates could be discharged directly under local regulations with COD≤100 mg/L, BOD5≤21 mg/L, SS≤52 mg/L, color≤32°. Results showed that the combined process could guarantee water reuse with high quality, and solve the problem of RO concentrate disposal.

  4. Ozone-biological activated carbon as a pretreatment process for reverse osmosis brine treatment and recovery.

    PubMed

    Lee, Lai Yoke; Ng, How Yong; Ong, Say Leong; Hu, Jiang Yong; Tao, Guihe; Kekre, Kiran; Viswanath, Balakrishnan; Lay, Winson; Seah, Harry

    2009-09-01

    Ozonation was used in this study to improve biodegradability of RO brine from water reclamation facilities. An ozone dosage ranging from 3 to 10 mg O(3)/L and contact times of 10 and 20 min in batch studies were found to increase the biodegradability (BOD(5)/TOC ratio) of the RO brine by 1.8-3.5 times. At the same time, total organic carbon (TOC) removal was in the range of 5.3-24.5%. The lab-scale ozone-biological activated carbon (BAC) at an ozone dosage of 6.0mg O(3)/L with 20-min contact time was able to achieve 3 times higher TOC removal compared to using BAC alone. Further processing with Capacitive Deionization (CDI) process was able to generate a product water with better water quality than the RO feed water, i.e., with more than 80% ions removal and a lower TOC concentration. The ozone-BAC pretreatment has the potential of reducing fouling in the CDI process. PMID:19580984

  5. Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter.

    PubMed

    Fu, Zhimin; Zhang, Yugao; Wang, Xiaojun

    2011-02-01

    In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O(3)-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O(3)-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7h, 9.2h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O(3)-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O(3)-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O(3)-BAF combine process for textile wastewater treatment.

  6. Ozone-biological activated carbon as a pretreatment process for reverse osmosis brine treatment and recovery.

    PubMed

    Lee, Lai Yoke; Ng, How Yong; Ong, Say Leong; Hu, Jiang Yong; Tao, Guihe; Kekre, Kiran; Viswanath, Balakrishnan; Lay, Winson; Seah, Harry

    2009-09-01

    Ozonation was used in this study to improve biodegradability of RO brine from water reclamation facilities. An ozone dosage ranging from 3 to 10 mg O(3)/L and contact times of 10 and 20 min in batch studies were found to increase the biodegradability (BOD(5)/TOC ratio) of the RO brine by 1.8-3.5 times. At the same time, total organic carbon (TOC) removal was in the range of 5.3-24.5%. The lab-scale ozone-biological activated carbon (BAC) at an ozone dosage of 6.0mg O(3)/L with 20-min contact time was able to achieve 3 times higher TOC removal compared to using BAC alone. Further processing with Capacitive Deionization (CDI) process was able to generate a product water with better water quality than the RO feed water, i.e., with more than 80% ions removal and a lower TOC concentration. The ozone-BAC pretreatment has the potential of reducing fouling in the CDI process.

  7. Two-stage, closed coupled catalytic liquefaction of coal. Sixteenth quarterly report, 1 July 1992--30 September 1992

    SciTech Connect

    Comolli, A.G.; Johanson, E.S.; Karolkiewicz, W.F.; Lee, L.K.; Stalzer, R.H.

    1992-12-01

    This quarterly report covers activities of the Two-Stage, Close-Coupled Catalytic Liquefaction of Coal Program during the period of July 1--September 30, 1992, at Hydrocarbon Research, Inc., in Lawrenceville and Princeton, New Jersey. This DOE contract period is from October 1, 1998 to December 31, 1992. The overall purpose of the program is to achieve higher yields of better quality transportation and turbine fuels and to lower the capital and production costs in order to make the products from direct coal liquefaction competitive with other fossil fuel products. The quarterly report covers work on Laboratory testing, Bench Scale Studies and PDU Activities focusing on scale-up of the Catalytic Two-Stage Liquefaction (CTSL) processing of sub-bituminous Black Thunder Coal.

  8. Non-catalytic direct synthesis of graphene on Si (111) wafers by using inductively-coupled plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hwang, Sung Won; Shin, Hyunho; Lee, Bongsoo; Choi, Suk-Ho

    2016-08-01

    We employ inductively-coupled plasma chemical vapor deposition for non-catalytic growth of graphene on a Si (111) wafer or glass substrate, which is useful for practical device applications of graphene without transfer processes. At a RF power (P) of 500 W under C2H2 flow, defect-free 3 ˜ 5-layer graphene is grown on Si (111) wafers, but on glass substrate, the layer is thicker and defective, as characterized by Raman spectroscopy and electron microscopy. The graphene is produced on Si (111) for P down to 190 W whereas it is almost not formed on glass for P < 250 W, possibly resulting from the weak catalytic-reaction-like effect on glass. These results are discussed based on possible growth mechanisms.

  9. Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

    PubMed Central

    Mallia, Carl J; Burton, Paul M; Smith, Alexander M R; Walter, Gary C

    2016-01-01

    Summary A flow system to perform Chan–Lam coupling reactions of various amines and arylboronic acids has been realised employing molecular oxygen as an oxidant for the re-oxidation of the copper catalyst enabling a catalytic process. A tube-in-tube gas reactor has been used to simplify the delivery of the oxygen accelerating the optimisation phase and allowing easy access to elevated pressures. A small exemplification library of heteroaromatic products has been prepared and the process has been shown to be robust over extended reaction times. PMID:27559412

  10. Catalytic Chan-Lam coupling using a 'tube-in-tube' reactor to deliver molecular oxygen as an oxidant.

    PubMed

    Mallia, Carl J; Burton, Paul M; Smith, Alexander M R; Walter, Gary C; Baxendale, Ian R

    2016-01-01

    A flow system to perform Chan-Lam coupling reactions of various amines and arylboronic acids has been realised employing molecular oxygen as an oxidant for the re-oxidation of the copper catalyst enabling a catalytic process. A tube-in-tube gas reactor has been used to simplify the delivery of the oxygen accelerating the optimisation phase and allowing easy access to elevated pressures. A small exemplification library of heteroaromatic products has been prepared and the process has been shown to be robust over extended reaction times. PMID:27559412

  11. Redox and Lewis acid relay catalysis: a titanocene/zinc catalytic platform in the development of multicomponent coupling reactions.

    PubMed

    Gianino, Joseph B; Campos, Catherine A; Lepore, Antonio J; Pinkerton, David M; Ashfeld, Brandon L

    2014-12-19

    A titanocene-catalyzed multicomponent coupling is described herein. Using catalytic titanocene, phosphine, and zinc dust, zinc acetylides can be generated from the corresponding iodoalkynes to affect sequential nucleophilic additions to aromatic aldehydes. The intermediate propargylic alkoxides are trapped in situ with acetic anhydride, which are susceptible to a second nucleophilic displacement upon treatment with a variety of electron-rich species, including acetylides, allyl silanes, electron-rich aromatics, silyl enol ethers, and silyl ketene acetals. Additionally, employing cyclopropane carboxaldehydes led to ring-opened products resulting from iodine incorporation. Taken together, these results form the basis for a new mode of three-component coupling reactions, which allows for rapid access to value added products in a single synthetic operation.

  12. Visible to near-infrared plasmon-enhanced catalytic activity of Pd hexagonal nanoplates for the Suzuki coupling reaction

    NASA Astrophysics Data System (ADS)

    Trinh, T. Thuy; Sato, Ryota; Sakamoto, Masanori; Fujiyoshi, Yoshifumi; Haruta, Mitsutaka; Kurata, Hiroki; Teranishi, Toshiharu

    2015-07-01

    Photocatalytic conversion of solar energy to chemical energy is an efficient process in green chemistry because it facilitates room temperature chemical transformations by generating electronically excited states in photocatalysts. We report here on the robust synthesis, detailed structural characterization, and especially photocatalytic properties of plasmonic Pd hexagonal nanoplates for chemical reactions. The Pd hexagonal nanoplates are twin crystals, and composed of the top and bottom faces enclosed by the {111} planes with stacking faults and the side surfaces bound by mixed six {111} and six {100} planes. The Pd hexagonal nanoplates with well-defined and tunable longitudinal localized surface plasmon resonance (LSPR) have enabled the direct harvesting of visible to near-infrared light for catalytic cross coupling reactions. Upon plasmon excitation, the catalytic Suzuki coupling reactions of iodobenzene and phenylboronic acid accelerate by a plasmonic photocatalytic effect of plasmon induced hot electrons. The turnover frequency (TOF) of the Pd hexagonal nanoplates in a reaction illuminated with a λ = 300-1000 nm Xenon lamp at 176 mW cm-2 was 2.5 and 2.7 times higher than that of non-plasmonic {111}-enclosed Pd nanooctahedra and {100}-enclosed Pd nanocubes, respectively, and 1.7 times higher than the TOF obtained when the reaction was thermally heated to the same temperature.Photocatalytic conversion of solar energy to chemical energy is an efficient process in green chemistry because it facilitates room temperature chemical transformations by generating electronically excited states in photocatalysts. We report here on the robust synthesis, detailed structural characterization, and especially photocatalytic properties of plasmonic Pd hexagonal nanoplates for chemical reactions. The Pd hexagonal nanoplates are twin crystals, and composed of the top and bottom faces enclosed by the {111} planes with stacking faults and the side surfaces bound by mixed six {111

  13. Exergy and Economic Analysis of Catalytic Coal Gasifiers Coupled With Solid Oxide Fuel Cells

    SciTech Connect

    Siefert, Nicholas; Litster, Shawn

    2011-01-01

    The National Energy Technology Laboratory (NETL) has undertaken a review of coal gasification technologies that integrate with solid oxide fuel cells (SOFC) to achieve system efficiencies near 60% while capturing and sequestering >90% of the carbon dioxide. One way to achieve an overall system efficiency of greater than 60% is in a power plant in which a catalytic coal gasifier produces a syngas with a methane composition of roughly 25% on a dry volume basis and this is sent to a SOFC, with CO{sub 2} capture occurring either before or after the SOFC. Integration of a catalytic gasifier with a SOFC, as opposed to a conventional entrained flow gasifier, is improved due to (a) decreased exergy destruction inside a catalytic, steam-coal gasifier producing a high-methane content syngas, and (b) decreased exergy destruction in the SOFC due to the ability to operate at lower air stoichiometric flow ratios. For example, thermal management of the SOFC is greatly improved due to the steam-methane reforming in the anode of the fuel cell. This paper has two main goals. First, we converted the levelized cost of electricity (LCOE) estimates of various research groups into an average internal rate of return on investment (IRR) in order to make comparisons between their results, and to underscore the increased rate of return on investment for advanced integrated gasification fuel cell systems with carbon capture & sequestration (IGFC-CCS) compared with conventional integrated gasification combined cycle (IGCC-CCS) systems and pulverized coal combustion (PCC-CCS) systems. Using capital, labor, and fuel costs from previous researchers and using an average price of baseload electricity generation of $61.50 / MW-hr, we calculated inflation-adjusted IRR values of up to 13%/yr for catalytic gasification with pressurized fuel cell and carbon dioxide capture and storage (CCS), whereas we calculate an IRR of ~4%/yr and ~2%/yr for new, conventional IGCC-CCS and PCC-CCS, respectively. If the

  14. Biogenic synthesis of palladium nanoparticles using Pulicaria glutinosa extract and their catalytic activity towards the Suzuki coupling reaction.

    PubMed

    Khan, Mujeeb; Khan, Merajuddin; Kuniyil, Mufsir; Adil, Syed Farooq; Al-Warthan, Abdulrahman; Alkhathlan, Hamad Z; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H

    2014-06-28

    Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report a facile and eco-friendly method for the synthesis of palladium (Pd) nanoparticles (NPs) using an aqueous solution of Pulicaria glutinosa, a plant widely found in a large region of Saudi Arabia, as a bioreductant. The as-prepared Pd NPs were characterized using ultraviolet-visible (UV-vis) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform-infrared spectroscopy (FT-IR). The hydroxyl groups of the plant extract (PE) molecules were found mainly responsible for the reduction and growth of Pd NPs. FT-IR analysis confirmed the dual role of the PE, both as a bioreductant as well as a capping ligand, which stabilizes the surface of Pd NPs. The crystalline nature of the Pd NPs was identified using XRD analysis which confirmed the formation of a face-centered cubic structure (JCPDS: 87-0641, space group: Fm3m (225)). Furthermore, the as-synthesized Pd NPs demonstrated excellent catalytic activity towards the Suzuki coupling reaction under aqueous and aerobic conditions. Kinetic studies of the catalytic reaction monitored using GC confirmed that the reaction completes in less than 5 minutes.

  15. Studies of coupled chemical and catalytic coal conversion methods. Tenth quarterly report, January--March 1990

    SciTech Connect

    Stock, L.M.

    1990-12-31

    This report concerns our research on base-catalyzed coal solubilization and a new approach for hydrogen addition. The work on base-catalyzed, chemical solubilization is continuing. this report is focused on the hydrogenation research. Specifically it deals with the use of arene chromium carbonyl complexes as reagents for the addition of dideuterium to coal molecules. In one phase of the work, he has established that the aromatic hydrocarbons in a representative coal liquid can be converted in very good yield to arene chromium carbonyl compounds. In a second phase of the work directly related to our objective of improved methods for catalytic hydrogenation, he has established that the aromatic constituents of the same coal liquid add dideuterium in the presence of added napththalene chromium carbonyl.

  16. Promotion and Suppression of Centriole Duplication Are Catalytically Coupled through PLK4 to Ensure Centriole Homeostasis.

    PubMed

    Kim, Minhee; O'Rourke, Brian P; Soni, Rajesh Kumar; Jallepalli, Prasad V; Hendrickson, Ronald C; Tsou, Meng-Fu Bryan

    2016-08-01

    PLK4 is the major kinase driving centriole duplication. Duplication occurs only once per cell cycle, forming one new (or daughter) centriole that is tightly engaged to the preexisting (or mother) centriole. Centriole engagement is known to block the reduplication of mother centrioles, but the molecular identity responsible for the block remains unclear. Here, we show that the centriolar cartwheel, the geometric scaffold for centriole assembly, forms the identity of daughter centrioles essential for the block, ceasing further duplication of the mother centriole to which it is engaged. To ensure a steady block, we found that the cartwheel requires constant maintenance by PLK4 through phosphorylation of the same substrate that drives centriole assembly, revealing a parsimonious control in which "assembly" and "block for new assembly" are linked through the same catalytic reaction to achieve homeostasis. Our results support a recently deduced model that the cartwheel-bound PLK4 directly suppresses centriole reduplication.

  17. Redox-coupled structural changes of the catalytic a' domain of protein disulfide isomerase.

    PubMed

    Inagaki, Koya; Satoh, Tadashi; Yagi-Utsumi, Maho; Le Gulluche, Anne-Charlotte; Anzai, Takahiro; Uekusa, Yoshinori; Kamiya, Yukiko; Kato, Koichi

    2015-09-14

    Protein disulfide isomerase functions as a folding catalyst in the endoplasmic reticulum. Its b' and a' domains provide substrate-binding sites and undergo a redox-dependent domain rearrangement coupled to an open-closed structural change. Here we determined the first solution structure of the a' domain in its oxidized form and thereby demonstrate that oxidation of the a' domain induces significant conformational changes not only in the vicinity of the active site but also in the distal b'-interfacial segment. Based on these findings, we propose that this conformational transition triggers the domain segregation coupled with the exposure of the hydrophobic surface.

  18. Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement.

    PubMed

    Zhang, Liang; Lovinger, Gabriel J; Edelstein, Emma K; Szymaniak, Adam A; Chierchia, Matteo P; Morken, James P

    2016-01-01

    Transition metal catalysis plays a central role in contemporary organic synthesis. Considering the tremendously broad array of transition metal-catalyzed transformations, it is remarkable that the underlying elementary reaction steps are relatively few in number. Here, we describe an alternative to the organometallic transmetallation step that is common in many metal-catalyzed reactions, such as Suzuki-Miyaura coupling. Specifically, we demonstrate that vinyl boronic ester ate complexes, prepared by combining organoboronates and organolithium reagents, engage in palladium-induced metallate rearrangement wherein 1,2-migration of an alkyl or aryl group from boron to the vinyl α-carbon occurs concomitantly with C-Pd σ-bond formation. This elementary reaction enables a powerful cross-coupling reaction in which a chiral Pd catalyst merges three simple starting materials-an organolithium, an organoboronic ester, and an organotriflate-into chiral organoboronic esters with high enantioselectivity.

  19. The Ketene-Surrogate Coupling: Catalytic Conversion of Aryl Iodides to Aryl Ketenes via Ynol Ethers**

    PubMed Central

    Zhang, Wenhan; Ready, Joseph M.

    2014-01-01

    tert-Butoxyacetylene is shown to undergo Sonogashira coupling with aryl iodides to yield aryl-substituted tert-butyl ynol ethers. These intermediates participate in a [1,5]-hydride shift, which results in the extrusion of isobutylene and the generation of aryl ketenes. The ketenes are trapped in situ with multiple nucleophiles or undergoelectrocyclic ring closure to yield hydroxynaphthalenes and quinolines. PMID:24975840

  20. Proton-coupled electron transfer dynamics in the catalytic mechanism of a [NiFe]-hydrogenase.

    PubMed

    Greene, Brandon L; Wu, Chang-Hao; McTernan, Patrick M; Adams, Michael W W; Dyer, R Brian

    2015-04-01

    The movement of protons and electrons is common to the synthesis of all chemical fuels such as H2. Hydrogenases, which catalyze the reversible reduction of protons, necessitate transport and reactivity between protons and electrons, but a detailed mechanism has thus far been elusive. Here, we use a phototriggered chemical potential jump method to rapidly initiate the proton reduction activity of a [NiFe] hydrogenase. Coupling the photochemical initiation approach to nanosecond transient infrared and visible absorbance spectroscopy afforded direct observation of interfacial electron transfer and active site chemistry. Tuning of intramolecular proton transport by pH and isotopic substitution revealed distinct concerted and stepwise proton-coupled electron transfer mechanisms in catalysis. The observed heterogeneity in the two sequential proton-associated reduction processes suggests a highly engineered protein environment modulating catalysis and implicates three new reaction intermediates; Nia-I, Nia-D, and Nia-SR(-). The results establish an elementary mechanistic understanding of catalysis in a [NiFe] hydrogenase with implications in enzymatic proton-coupled electron transfer and biomimetic catalyst design.

  1. Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.

    PubMed

    Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

    2014-08-20

    The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

  2. The effect of external magnetic fields on the catalytic activity of Pd nanoparticles in Suzuki cross-coupling reactions.

    PubMed

    Gao, Lei; Wang, Changlai; Li, Ren; Li, Ran; Chen, Qianwang

    2016-04-21

    Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the adsorption system, which is beneficial to the reaction. From the analysis of the partial density states, it could be seen that the 2p orbital of the carbon atom in bromobenzene and the 4d orbital of the Pd atom overlap more closely in the presence of MFs, which is beneficial for the electron transfer from the Pd substrate to the bromobenzene molecule. This study is helpful in understanding the interaction between MFs and catalysts and regulating the process of catalytic reactions via MFs. PMID:27043428

  3. Insights into the effects of surface properties of oxides on the catalytic activity of Pd for C-C coupling reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Sai; Li, Jing; Gao, Wei; Qu, Yongquan

    2015-02-01

    Understanding the interaction between Pd nanocatalysts and metal oxide supports for heterogeneous C-C coupling reactions is still ambiguous since many factors influence the catalytic behavior of Pd nanocatalysts. Herein, three porous nanorods of CeO2 with controllable surface properties were employed as supports for Pd nanocatalysts with similar dispersion, which avoided the impact of other factors including surface area, morphology and accessible active sites. It provides an ideal approach to probe synergetic catalytic behavior of metal nanoparticles on supports. The results obtained by studying three C-C coupling reactions (Ullman, Suzuki and Heck) indicate a strong correlation between the surface properties of supports and the catalytic activity of Pd nanocatalysts: supports with a strong basicity and a high concentration of oxygen vacancies result in a rich electron density of Pd and accelerate the first step of oxidative addition reaction for C-C coupling. The infrared spectroscopic study on ν[CO] of CO-treated catalysts and XPS analysis of the Pd(3d) core level provide strong evidence supporting the interaction of Pd/supports for C-C coupling reactions.Understanding the interaction between Pd nanocatalysts and metal oxide supports for heterogeneous C-C coupling reactions is still ambiguous since many factors influence the catalytic behavior of Pd nanocatalysts. Herein, three porous nanorods of CeO2 with controllable surface properties were employed as supports for Pd nanocatalysts with similar dispersion, which avoided the impact of other factors including surface area, morphology and accessible active sites. It provides an ideal approach to probe synergetic catalytic behavior of metal nanoparticles on supports. The results obtained by studying three C-C coupling reactions (Ullman, Suzuki and Heck) indicate a strong correlation between the surface properties of supports and the catalytic activity of Pd nanocatalysts: supports with a strong basicity and a

  4. Catalytic Alkene Carboaminations Enabled by Oxidative Proton-Coupled Electron Transfer

    PubMed Central

    Choi, Gilbert J.; Knowles, Robert R.

    2015-01-01

    Here we describe a dual catalyst system comprised of an iridium photocatalyst and weak phosphate base that is capable of both selectively homolyzing the N–H bonds of N-arylamides (bond dissociation free energies ~ 100 kcal/mol) via concerted proton-coupled electron transfer (PCET) and mediating efficient carboamination reactions of the resulting amidyl radicals. This manner of PCET activation, which finds its basis in numerous biological redox processes, enables the formal homolysis of a stronger amide N–H bond in the presence of weaker allylic C–H bonds, a selectivity that is uncommon in conventional molecular H atom acceptors. Moreover, this transformation affords access to a broad range of structurally complex heterocycles from simple amide starting materials. The design, synthetic scope, and mechanistic evaluation of the PCET process are described. PMID:26166022

  5. Simple catalytic mechanism for the direct coupling of α-carbonyls with functionalized amines: a one-step synthesis of Plavix.

    PubMed

    Evans, Ryan W; Zbieg, Jason R; Zhu, Shaolin; Li, Wei; MacMillan, David W C

    2013-10-30

    The direct α-amination of ketones, esters, and aldehydes has been accomplished via copper catalysis. In the presence of catalytic copper(II) bromide, a diverse range of carbonyl and amine substrates undergo fragment coupling to produce synthetically useful α-amino-substituted motifs. The transformation is proposed to proceed via a catalytically generated α-bromo carbonyl species; nucleophilic displacement of the bromide by the amine then delivers the α-amino carbonyl adduct while the catalyst is reconstituted. The practical value of this transformation is highlighted through one-step syntheses of two high-profile pharmaceutical agents, Plavix and amfepramone. PMID:24107144

  6. Theoretical Study of Plasmon-Enhanced Surface Catalytic Coupling Reactions of Aromatic Amines and Nitro Compounds.

    PubMed

    Zhao, Liu-Bin; Zhang, Meng; Huang, Yi-Fan; Williams, Christopher T; Wu, De-Yin; Ren, Bin; Tian, Zhong-Qun

    2014-04-01

    Taking advantage of the unique capacity of surface plasmon resonance, plasmon-enhanced heterogeneous catalysis has recently come into focus as a promising technique for high performance light-energy conversion. This work performs a theoretical study on the reaction mechanism for conversions of p-aminothiophenol (PATP) and p-nitrothiophenol (PNTP) to aromatic azo species, p,p'-dimercaptoazobenzene (DMAB). In the absence of O2 or H2, the plasmon-driven photocatalysis mechanism (hot electron-hole reactions) is the major reaction channel. In the presence of O2 or H2, the plasmon-assisted surface catalysis mechanism (activated oxygen/hydrogen reactions) is the major reaction channel. The present results show that the coupling reactions of PATP and PNTP strongly depend on the solution pH, the irradiation wavelength, the irradiation power, and the nature of metal substrates as well as the surrounding atmosphere. The present study has drawn a fundamental physical picture for understanding plasmon-enhanced heterogeneous catalysis.

  7. The effect of external magnetic fields on the catalytic activity of Pd nanoparticles in Suzuki cross-coupling reactions

    NASA Astrophysics Data System (ADS)

    Gao, Lei; Wang, Changlai; Li, Ren; Li, Ran; Chen, Qianwang

    2016-04-01

    Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the adsorption system, which is beneficial to the reaction. From the analysis of the partial density states, it could be seen that the 2p orbital of the carbon atom in bromobenzene and the 4d orbital of the Pd atom overlap more closely in the presence of MFs, which is beneficial for the electron transfer from the Pd substrate to the bromobenzene molecule. This study is helpful in understanding the interaction between MFs and catalysts and regulating the process of catalytic reactions via MFs.Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the

  8. High-temperature catalytic oxidative conversion of propane to propylene and ethylene involving coupling of exothermic and endothermic reactions

    SciTech Connect

    Choudhary, V.R.; Rane, V.H.; Rajput, A.M.

    2000-04-01

    Coupling of the exothermic catalytic oxidative conversion and endothermic thermal cracking (noncatalytic) reactions of propane to propylene and ethylene over the SrO/La{sub 2}O{sub 3}/SA5205 catalyst in the presence of steam and limited oxygen was investigated at different process conditions (temperature, 700--850 C; C{sub 3}H{sub 8}/O{sub 2} ratio in feed, 2.0--8.0; H{sub 2}O/C{sub 3}H{sub 8} ratio, 0.5--2.5; space velocity, 2,000--15,000 cm{sup 3}/g h). In the presence of steam and limited O{sub 2}, the endothermic thermal cracking and exothermic oxidative conversion reactions occur simultaneously and there is no coke formation on the catalyst. Because of the direct coupling of exothermic and endothermic reactions, this process occurs in a most energy efficient and safe manner. The propane conversion, selectivity for propylene, and net heat of reaction ({Delta}H{sub r}) in the process are strongly influenced by the temperature and concentration of O{sub 2} relative to the propane in the feed. The C{sub 3}H{sub 6}/C{sub 2}H{sub 4} product ratio is also strongly influenced by the temperature, C{sub 3}H{sub 8}/O{sub 2} feed ratio, and space velocity. The net heat of reaction can be controlled by manipulating the reaction temperature and C{sub 3}H{sub 8}/O{sub 2} ratio in the feed; the process exothermicity is reduced drastically with increasing the temperature and/or C{sub 3}H{sub 8}/O{sub 2} feed ratio.

  9. Copper(I) complexes with trispyrazolylmethane ligands: synthesis, characterization, and catalytic activity in cross-coupling reactions.

    PubMed

    Haldón, Estela; Álvarez, Eleuterio; Nicasio, M Carmen; Pérez, Pedro J

    2012-08-01

    Three novel Cu(I) complexes bearing tris(pyrazolyl)methane ligands, Tpm(x), have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC(pz)(3)), Tpm*, (HC(3,5-Me(2)-pz)(3)), and Tpm(Ms), (HC(3-Ms-pz)(3)). X-ray diffraction studies have shown that the Tpm and Tpm(Ms) derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature (1)H NMR studies in CDCl(3) have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu(I)-phthalimidate with iodobenzene afforded the expected C-N coupling product in 76% yield accounting for its role as an intermediate in this transformation.

  10. Catalytic Upgrading of Biomass-Derived Compounds via C-C Coupling Reactions. Computational and Experimental Studies of Acetaldehyde and Furan Reactions in HZSM-5

    SciTech Connect

    Liu, Cong; Evans, Tabitha J.; Cheng, Lei; Nimlos, Mark R.; Mukarakate, Calvin; Robichaud, David J.; Assary, Rajeev S.; Curtiss, Larry A.

    2015-10-02

    These catalytic C–C coupling and deoxygenation reactions are essential for upgrading of biomass-derived oxygenates to fuel-range hydrocarbons. Detailed understanding of mechanistic and energetic aspects of these reactions is crucial to enabling and improving the catalytic upgrading of small oxygenates to useful chemicals and fuels. Using periodic density functional theory (DFT) calculations, we have investigated the reactions of furan and acetaldehyde in an HZSM-5 zeolite catalyst, a representative system associated with the catalytic upgrading of pyrolysis vapors. Comprehensive energy profiles were computed for self-reactions (i.e., acetaldehyde coupling and furan coupling) and cross-reactions (i.e., acetaldehyde + furan) of this representative mixture. Major products proposed from the computations are further confirmed using temperature controlled mass spectra measurements. Moreover, the computational results show that furan interacts with acetaldehyde in HZSM-5 via an alkylation mechanism, which is more favorable than the self-reactions, indicating that mixing furans with aldehydes could be a promising approach to maximize effective C–C coupling and dehydration while reducing the catalyst deactivation (e.g., coke formation) from aldehyde condensation.

  11. 2D/2D nano-hybrids of γ-MnO₂ on reduced graphene oxide for catalytic ozonation and coupling peroxymonosulfate activation.

    PubMed

    Wang, Yuxian; Xie, Yongbing; Sun, Hongqi; Xiao, Jiadong; Cao, Hongbin; Wang, Shaobin

    2016-01-15

    Two-dimensional reduced graphene oxide (2D rGO) was employed as both a shape-directing medium and support to fabricate 2D γ-MnO2/2D rGO nano-hybrids (MnO2/rGO) via a facile hydrothermal route. For the first time, the 2D/2D hybrid materials were used for catalytic ozonation of 4-nitrophenol. The catalytic efficiency of MnO2/rGO was much higher than either MnO2 or rGO only, and rGO was suggested to play the role for promoting electron transfers. Quenching tests using tert-butanol, p-benzoquinone, and sodium azide suggested that the major radicals responsible for 4-nitrophenol degradation and mineralization are O2(-) and (1)O2, but not ·OH. Reusability tests demonstrated a high stability of the materials in catalytic ozonation with minor Mn leaching below 0.5 ppm. Degradation mechanism, reaction kinetics, reusability and a synergistic effect between catalytic ozonation and coupling peroxymonosulfate (PMS) activation were also discussed.

  12. N- vs. C-Domain Selectivity of Catalytic Inactivation of Human Angiotensin Converting Enzyme by Lisinopril-Coupled Transition Metal Chelates

    PubMed Central

    Hocharoen, Lalintip; Joyner, Jeff C.; Cowan, J. A.

    2014-01-01

    The N- and C-terminal domains of human somatic Angiotensin I Converting Enzyme (sACE-1) demonstrate distinct physiological functions, with resulting interest in the development of domain-selective inhibitors for specific therapeutic applications. Herein, the activity of lisinopril-coupled transition metal chelates were tested for both reversible binding and irreversible catalytic inactivation of sACE-1. C/N domain binding selectivity ratios ranged from 1 to 350, while rates of irreversible catalytic inactivation of the N- and C-domains were found to be significantly greater for the N-domain, suggesting a more optimal orientation of the M-chelate-lisinopril complexes within the active site of the N-domain of sACE-1. Finally, the combined effect of binding selectivity and inactivation selectivity was assessed for each catalyst (double-filter selectivity factors), and several catalysts were found to cause domain-selective catalytic inactivation. The results of this study demonstrate the ability to optimize the target selectivity of catalytic metallopeptides through both binding and orientation factors (double-filter effect). PMID:24228790

  13. Details in the catalytic mechanism of mammalian thioredoxin reductase 1 revealed using point mutations and juglone-coupled enzyme activities.

    PubMed

    Xu, Jianqiang; Cheng, Qing; Arnér, Elias S J

    2016-05-01

    The mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a key enzyme in redox regulation, antioxidant defense, and cellular growth. TrxR1 can catalyze efficient reduction of juglone (5-hydroxy-1,4-naphthoquinone; walnut toxin) in a reaction which, in contrast to reduction of most other substrates of TrxR1, is not dependent upon an intact selenocysteine (Sec, U) residue of the enzyme. Using a number of TrxR1 mutant variants, we here found that a sole Cys residue at the C-terminal tail of TrxR1 is required for high-efficiency juglone-coupled NADPH oxidase activity of Sec-deficient enzyme, occurring with mixed one- and two-electron reactions producing superoxide. The activity also utilizes the FAD and the N-terminal redox active disulfide/dithiol motif of TrxR1. If a sole Cys residue at the C-terminal tail of TrxR1, in the absence of Sec, was moved further towards the C-terminal end of the protein compared to its natural position at residue 497, juglone reduction was, surprisingly, further increased. Ala substitutions of Trp407, Asn418 and Asn419 in a previously described "guiding bar", thought to mediate interactions of the C-terminal tail of TrxR1 with the FAD/dithiol site at the N-terminal domain of the other subunit in the dimeric enzyme, lowered turnover with juglone about 4.5-fold. Four residues of Sec-deficient TrxR1 were found to be easily arylated by juglone, including the Cys residue at position 497. Based upon our observations we suggest a model for involvement of the juglone-arylated C-terminal motif of TrxR1 to explain its high activity with juglone. This study thus provides novel insights into the catalytic mechanisms of TrxR1. One-electron juglone reduction by TrxR1 producing superoxide should furthermore contribute to the well-known prooxidant cytotoxicity of juglone. PMID:26898501

  14. Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

    2010-01-01

    We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

  15. Catalytic Activity of Cationic and Neutral Silver(I)-XPhos Complexes with Nitrogen Ligands or Tolylsulfonate for Mannich and Aza-Diels-Alder Coupling Reactions.

    PubMed

    Grirrane, Abdessamad; Álvarez, Eleuterio; García, Hermenegildo; Corma, Avelino

    2016-01-01

    Cationic and neutral silver(I)-L complexes (L=Buchwald-type biaryl phosphanes) with nitrogen co-ligands or organosulfonate counter ions have been synthesised and characterised through their structural and spectroscopic properties. At room temperature, both cationic and neutral silver(I)-L complexes are extremely active catalysts in the promotion of the single and double A(3) coupling of terminal (di)alkynes, pyrrolidine and formaldehyde. In addition, the aza-Diels-Alder two- and three-component coupling reactions of Danishefsky's diene with an imine or amine and aldehyde are efficiently catalysed by these cationic or neutral silver(I)-L complexes. The solvent influences the catalytic performance due to limited complex solubility or solvent decomposition and reactivity. The isolation of new silver(I)-L complexes with reagents as ligands lends support to mechanistic proposals for such catalytic processes. The activity, stability and metal-distal arene interaction of these silver(I)-L catalysts have been compared with those of analogous cationic gold(I) and copper(I) complexes. PMID:26598792

  16. Dynamic coupling between the LID and NMP domain motions in the catalytic conversion of ATP and AMP to ADP by adenylate kinase

    NASA Astrophysics Data System (ADS)

    Jana, Biman; Adkar, Bharat V.; Biswas, Rajib; Bagchi, Biman

    2011-01-01

    The catalytic conversion of adenosine triphosphate (ATP) and adenosine monophosphate (AMP) to adenosine diphosphate (ADP) by adenylate kinase (ADK) involves large amplitude, ligand induced domain motions, involving the opening and the closing of ATP binding domain (LID) and AMP binding domain (NMP) domains, during the repeated catalytic cycle. We discover and analyze an interesting dynamical coupling between the motion of the two domains during the opening, using large scale atomistic molecular dynamics trajectory analysis, covariance analysis, and multidimensional free energy calculations with explicit water. Initially, the LID domain must open by a certain amount before the NMP domain can begin to open. Dynamical correlation map shows interesting cross-peak between LID and NMP domain which suggests the presence of correlated motion between them. This is also reflected in our calculated two-dimensional free energy surface contour diagram which has an interesting elliptic shape, revealing a strong correlation between the opening of the LID domain and that of the NMP domain. Our free energy surface of the LID domain motion is rugged due to interaction with water and the signature of ruggedness is evident in the observed root mean square deviation variation and its fluctuation time correlation functions. We develop a correlated dynamical disorder-type theoretical model to explain the observed dynamic coupling between the motion of the two domains in ADK. Our model correctly reproduces several features of the cross-correlation observed in simulations.

  17. Dynamic coupling between the LID and NMP domain motions in the catalytic conversion of ATP and AMP to ADP by adenylate kinase.

    PubMed

    Jana, Biman; Adkar, Bharat V; Biswas, Rajib; Bagchi, Biman

    2011-01-21

    The catalytic conversion of adenosine triphosphate (ATP) and adenosine monophosphate (AMP) to adenosine diphosphate (ADP) by adenylate kinase (ADK) involves large amplitude, ligand induced domain motions, involving the opening and the closing of ATP binding domain (LID) and AMP binding domain (NMP) domains, during the repeated catalytic cycle. We discover and analyze an interesting dynamical coupling between the motion of the two domains during the opening, using large scale atomistic molecular dynamics trajectory analysis, covariance analysis, and multidimensional free energy calculations with explicit water. Initially, the LID domain must open by a certain amount before the NMP domain can begin to open. Dynamical correlation map shows interesting cross-peak between LID and NMP domain which suggests the presence of correlated motion between them. This is also reflected in our calculated two-dimensional free energy surface contour diagram which has an interesting elliptic shape, revealing a strong correlation between the opening of the LID domain and that of the NMP domain. Our free energy surface of the LID domain motion is rugged due to interaction with water and the signature of ruggedness is evident in the observed root mean square deviation variation and its fluctuation time correlation functions. We develop a correlated dynamical disorder-type theoretical model to explain the observed dynamic coupling between the motion of the two domains in ADK. Our model correctly reproduces several features of the cross-correlation observed in simulations.

  18. Green synthesis, characterization and catalytic activity of the Pd/TiO2 nanoparticles for the ligand-free Suzuki-Miyaura coupling reaction.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad

    2016-03-01

    A green synthesis process was developed for production of the Pd/TiO2 nanoparticles (NPs) without using toxic, hazardous and dangerous materials. Myrtus communis L. leaf extract serves as a mild, renewable and non-toxic reducing agent. The advantages of this biosynthesis method include use of cheap, clean, nontoxic and environmentally benign precursors and simple procedures without time-consuming polymerization and problems with treatment of a highly viscous polymeric resin. More importantly, the synthesized Pd/TiO2 NPs presented excellent catalytic activity for ligand-free Suzuki-Miyaura coupling which could be easily separated from the reaction mixture and reused many times with no loss of activity. Therefore, these properties indicate demonstrative benefits of the catalyst. The Pd/TiO2 NPs was characterized by FESEM, TEM, FT-IR, UV-vis spectroscopy and EDS. PMID:26674227

  19. Determination of trace uranium by resonance fluorescence method coupled with photo-catalytic technology and dual cloud point extraction.

    PubMed

    Li, Jiekang; Li, Guirong; Han, Qian

    2016-12-01

    In this paper, two kinds of salophens (Sal) with different solubilities, Sal1 and Sal2, have been respectively synthesized, and they all can combine with uranyl to form stable complexes: [UO2(2+)-Sal1] and [UO2(2+)-Sal2]. Among them, [UO2(2+)-Sal1] was used as ligand to extract uranium in complex samples by dual cloud point extraction (dCPE), and [UO2(2+)-Sal2] was used as catalyst for the determination of uranium by photocatalytic resonance fluorescence (RF) method. The photocatalytic characteristic of [UO2(2+)-Sal2] on the oxidized pyronine Y (PRY) by potassium bromate which leads to the decrease of RF intensity of PRY were studied. The reduced value of RF intensity of reaction system (ΔF) is in proportional to the concentration of uranium (c), and a novel photo-catalytic RF method was developed for the determination of trace uranium (VI) after dCPE. The combination of photo-catalytic RF techniques and dCPE procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimal conditions, the linear calibration curves range for 0.067 to 6.57ngmL(-1), the linear regression equation was ΔF=438.0 c (ngmL(-1))+175.6 with the correlation coefficient r=0.9981. The limit of detection was 0.066ngmL(-1). The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0-103.5%. The mechanisms of the indicator reaction and dCPE are discussed.

  20. Catalytic cross-coupling of diazo compounds with coinage metal-based catalysts: an experimental and theoretical study.

    PubMed

    Rivilla, Ivan; Sameera, W M C; Alvarez, Eleuterio; Díaz-Requejo, M Mar; Maseras, Feliu; Pérez, Pedro J

    2013-03-28

    We examined the ability of Tp(x)M (Tp(x) = hydrotris(pyrazolyl)borate ligand; M = Cu and Ag) and IPrMCl (IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene; M = Cu, Ag, Au) complexes as catalyst precursors for the cross-coupling of diazo compounds. Experimental data showed that the metal centre can be tuned with the appropriate selection of the ligand to yield either the homo- or hetero-coupling (cross-coupling) products. A computational study of the reaction mechanism allowed the rationalization of the experimental reactivity patterns, and the identification of the key reaction step controlling the selectivity: the initial reaction between the metallocarbene intermediate and one of the diazo compounds.

  1. Shape dependent catalytic activity of nanoflowers and nanospheres of Pd4S generated via one pot synthesis and grafted on graphene oxide for Suzuki coupling.

    PubMed

    Singh, Ved Vati; Kumar, Umesh; Tripathi, Sandeep Nath; Singh, Ajai Kumar

    2014-09-01

    Nanoflowers and nanospheres of Pd4S have been prepared for the first time from a single source precursor complex, [PdCl2(PhS-CH2CH2CH2-NH2)] (), by its one pot thermolysis at 195 °C. In oleylamine, flower shaped nanoparticles of Pd4S were formed but in an oleic acid (OA) and octadecene (ODE) mixture (1 : 1) the product was nanospheres of Pd4S (size in the range ∼23-38 nm and 15-28 nm, respectively). These nanoparticles (NPs) were grafted on graphene oxide (GO) at room temperature to prepare nanocomposites, GO-Pd4S. HRTEM, powder X-ray diffraction (PXRD) and TEM-EDX have been used to authenticate the nanoparticles and their composites. XPS of Pd4S NPs indicates the oxidation states of Pd and S are both zero with a Pd : S ratio ∼4.1 : 0.9. For the catalysis of Suzuki-Miyaura coupling reactions the nanoparticles individually and in the form of composites with GO were explored. The flower shaped NPs are superior than the spherical ones for this catalysis in aqueous ethanol and the catalytic efficiency increases on grafting the nanoflowers/spheres onto GO. The conversion was ∼99% (in 5 h; at 80 °C) for the composite of graphene oxide (GO) with the Pd4S nanoflowers (Pd: 0.2 mol%). The catalytic efficiency follows the order GO-Pd4S-nanoflowers > GO-Pd4S-nanospheres > Pd4S nanoflowers > Pd4S nanospheres. The recyclability of the GO-Pd4S nanoflower catalyst was examined for the coupling reaction and conversion was found to be ∼46% in the fourth run even after increasing the reaction time to 12 h. To understand whether the catalytic process with the GO-Pd4S nanoflowers was homogeneous or heterogeneous mercury poisoning, triphenylphosphine and three phase tests were carried out. They suggest that active Pd leached from GO-Pd4S nanoflowers does the catalysis significantly in a homogeneous fashion. Overall the catalysis appears to be a cocktail of homogeneous and some heterogeneous nature.

  2. Carboxylic acid-grafted mesoporous material and its high catalytic activity in one-pot three-component coupling reaction

    NASA Astrophysics Data System (ADS)

    Gomes, Ruth; Dutta, Saikat; Bhaumik, Asim

    2014-11-01

    A new carboxylic acid functionalized mesoporous organic polymer has been synthesized via in situ radical polymerization of divinylbenzene and acrylic acid using a mesoporous silica as a seed during the polymerization process under solvothermal conditions. The mesoporous material MPDVAA-1 has been thoroughly characterized employing powder XRD, solid state 13C cross polarization magic angle spinning-nuclear magnetic resonance, FT-IR spectroscopy, N2 sorption, HR-TEM, and NH3 temperature programmed desorption-thermal conductivity detector (TPD-TCD) analysis to understand its porosity, chemical environment, bonding, and surface properties. The mesoporous polymer was used as a catalyst for a three comp onent Biginelli condensation between various aldehydes, β-keto esters, and urea/thioureas to give 3,4-dihydropyrimidine-2(1H)-ones. The reactions were carried out under conventional heating as well as solvent-free microwave irradiation of solid components, and in both the cases, the mesoporous polymer MPDVAA-1 proved to be a powerful, robust, and reusable catalyst with high catalytic efficiency.

  3. Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst.

    PubMed

    Baran, Talat; Inanan, Tülden; Menteş, Ayfer

    2016-07-10

    The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, (1)H NMR, (13)C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H2O2 decomposition reaction with considerable high activity using comparatively small loading catalyst (10mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature. PMID:27106147

  4. Native Electrophoresis-Coupled Activity Assays Reveal Catalytically-Active Protein Aggregates of Escherichia coli β-Glucuronidase

    PubMed Central

    Burchett, Gina G.; Folsom, Charles G.; Lane, Kimberly T.

    2015-01-01

    β-glucuronidase is found as a functional homotetramer in a variety of organisms, including humans and other animals, as well as a number of bacteria. This enzyme is important in these organisms, catalyzing the hydrolytic removal of a glucuronide moiety from substrate molecules. This process serves to break down sugar conjugates in animals and provide sugars for metabolism in bacteria. While β-glucuronidase is primarily found as a homotetramer, previous studies have indicated that the human form of the protein is also catalytically active as a dimer. Here we present evidence for not only an active dimer of the E. coli form of the protein, but also for several larger active complexes, including an octomer and a 16-mer. Additionally, we propose a model for the structures of these large complexes, based on computationally-derived molecular modeling studies. These structures may have application in the study of human disease, as several diseases have been associated with the aggregation of proteins. PMID:26121040

  5. Carboxylic acid-grafted mesoporous material and its high catalytic activity in one-pot three-component coupling reaction

    SciTech Connect

    Gomes, Ruth; Bhaumik, Asim; Dutta, Saikat

    2014-11-01

    A new carboxylic acid functionalized mesoporous organic polymer has been synthesized via in situ radical polymerization of divinylbenzene and acrylic acid using a mesoporous silica as a seed during the polymerization process under solvothermal conditions. The mesoporous material MPDVAA-1 has been thoroughly characterized employing powder XRD, solid state {sup 13}C cross polarization magic angle spinning-nuclear magnetic resonance, FT-IR spectroscopy, N{sub 2} sorption, HR-TEM, and NH{sub 3} temperature programmed desorption-thermal conductivity detector (TPD-TCD) analysis to understand its porosity, chemical environment, bonding, and surface properties. The mesoporous polymer was used as a catalyst for a three comp onent Biginelli condensation between various aldehydes, β-keto esters, and urea/thioureas to give 3,4-dihydropyrimidine-2(1H)-ones. The reactions were carried out under conventional heating as well as solvent-free microwave irradiation of solid components, and in both the cases, the mesoporous polymer MPDVAA-1 proved to be a powerful, robust, and reusable catalyst with high catalytic efficiency.

  6. Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst.

    PubMed

    Baran, Talat; Inanan, Tülden; Menteş, Ayfer

    2016-07-10

    The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, (1)H NMR, (13)C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H2O2 decomposition reaction with considerable high activity using comparatively small loading catalyst (10mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature.

  7. Native functionality in triple catalytic cross-coupling: sp³ C-H bonds as latent nucleophiles.

    PubMed

    Shaw, Megan H; Shurtleff, Valerie W; Terrett, Jack A; Cuthbertson, James D; MacMillan, David W C

    2016-06-10

    The use of sp(3) C-H bonds--which are ubiquitous in organic molecules--as latent nucleophile equivalents for transition metal-catalyzed cross-coupling reactions has the potential to substantially streamline synthetic efforts in organic chemistry while bypassing substrate activation steps. Through the combination of photoredox-mediated hydrogen atom transfer (HAT) and nickel catalysis, we have developed a highly selective and general C-H arylation protocol that activates a wide array of C-H bonds as native functional handles for cross-coupling. This mild approach takes advantage of a tunable HAT catalyst that exhibits predictable reactivity patterns based on enthalpic and bond polarity considerations to selectively functionalize α-amino and α-oxy sp(3) C-H bonds in both cyclic and acyclic systems.

  8. Native functionality in triple catalytic cross-coupling: sp³ C-H bonds as latent nucleophiles.

    PubMed

    Shaw, Megan H; Shurtleff, Valerie W; Terrett, Jack A; Cuthbertson, James D; MacMillan, David W C

    2016-06-10

    The use of sp(3) C-H bonds--which are ubiquitous in organic molecules--as latent nucleophile equivalents for transition metal-catalyzed cross-coupling reactions has the potential to substantially streamline synthetic efforts in organic chemistry while bypassing substrate activation steps. Through the combination of photoredox-mediated hydrogen atom transfer (HAT) and nickel catalysis, we have developed a highly selective and general C-H arylation protocol that activates a wide array of C-H bonds as native functional handles for cross-coupling. This mild approach takes advantage of a tunable HAT catalyst that exhibits predictable reactivity patterns based on enthalpic and bond polarity considerations to selectively functionalize α-amino and α-oxy sp(3) C-H bonds in both cyclic and acyclic systems. PMID:27127237

  9. Cooperative activation of cyclobutanones and olefins leads to bridged-ring systems by a catalytic [4+2] coupling

    PubMed Central

    Ko, Haye Min; Dong, Guangbin

    2014-01-01

    Bridged-ring systems are widely found in natural products and successful syntheses of them frequently feature intramolecular Diels-Alder (IMDA) reactions. These reactions are subclassified as either type I or type II IMDAs depending on how the diene motif is tethered to the rest of the substrate - type I are tethered at the 1-position of the diene and type II at the 2-position. While the type I IMDA has been used to great success, the molecular scaffolds accessible by type II IMDAs are limited by the strain inherent in the formation of a sp2-carbon at a bridgehead position. Here, we describe a complementary approach that provides access to these structures through the C−C activation of cyclobutanones and their coupling with olefins. Various alkenes have been coupled with cyclobutanones to provide a range of bridged skeletons. The ketone group of the products serves as a convenient handle for downstream functionalization. PMID:25054946

  10. Catalytic conversion of sugarcane bagasse to cellulosic ethanol: TiO2 coupled nanocellulose as an effective hydrolysis enhancer.

    PubMed

    Jabasingh, S Anuradha; Lalith, D; Prabhu, M Arun; Yimam, Abubekker; Zewdu, Taye

    2016-01-20

    The present study deals with the production of cellulosic ethanol from bagasse using the synthesized TiO2 coupled nanocellulose (NC-TiO2) as catalyst. Aspergillus nidulans AJSU04 cellulase was used for the hydrolysis of bagasse. NC-TiO2 at various concentrations was added to bagasse in order to enhance the yield of reducing sugars. Complex interaction between cellulase, bagasse, NC-TiO2 and the reaction environment is thoroughly studied. A mathematical model was developed to describe the hydrolysis reaction. Ethanol production from enzymatically hydrolyzed sugarcane bagasse catalyzed with NC-TiO2 was carried out using Saccharomyces cerevisiae ATCC 20602. The glucose release rates and ethanol concentrations were determined. Ethanol produced was found to be strongly dependent on pretreatment given, hydrolysis and fermentation conditions. The study confirmed the promising accessibility of NC-TiO2, for enhanced glucose production rates and improved ethanol yield.

  11. Catalytic conversion of sugarcane bagasse to cellulosic ethanol: TiO2 coupled nanocellulose as an effective hydrolysis enhancer.

    PubMed

    Jabasingh, S Anuradha; Lalith, D; Prabhu, M Arun; Yimam, Abubekker; Zewdu, Taye

    2016-01-20

    The present study deals with the production of cellulosic ethanol from bagasse using the synthesized TiO2 coupled nanocellulose (NC-TiO2) as catalyst. Aspergillus nidulans AJSU04 cellulase was used for the hydrolysis of bagasse. NC-TiO2 at various concentrations was added to bagasse in order to enhance the yield of reducing sugars. Complex interaction between cellulase, bagasse, NC-TiO2 and the reaction environment is thoroughly studied. A mathematical model was developed to describe the hydrolysis reaction. Ethanol production from enzymatically hydrolyzed sugarcane bagasse catalyzed with NC-TiO2 was carried out using Saccharomyces cerevisiae ATCC 20602. The glucose release rates and ethanol concentrations were determined. Ethanol produced was found to be strongly dependent on pretreatment given, hydrolysis and fermentation conditions. The study confirmed the promising accessibility of NC-TiO2, for enhanced glucose production rates and improved ethanol yield. PMID:26572403

  12. Green synthesis of Pd/CuO nanoparticles by Theobroma cacao L. seeds extract and their catalytic performance for the reduction of 4-nitrophenol and phosphine-free Heck coupling reaction under aerobic conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar; Bagherzadeh, Mojtaba

    2015-06-15

    We report the green synthesis of palladium/CuO nanoparticles (Pd/CuO NPs) using Theobroma cacao L. seeds extract and their catalytic activity for the reduction of 4-nitrophenol and Heck coupling reaction under aerobic conditions. The catalyst was characterized using the powder XRD, TEM, EDS, UV-vis and FT-IR. This method has the advantages of high yields, elimination of surfactant, ligand and homogeneous catalysts, simple methodology and easy work up. The catalyst can be recovered from the reaction mixture and reused several times without any significant loss of catalytic activity.

  13. Coupling of kinetic Monte Carlo simulations of surface reactions to transport in a fluid for heterogeneous catalytic reactor modeling

    SciTech Connect

    Schaefer, C.; Jansen, A. P. J.

    2013-02-07

    We have developed a method to couple kinetic Monte Carlo simulations of surface reactions at a molecular scale to transport equations at a macroscopic scale. This method is applicable to steady state reactors. We use a finite difference upwinding scheme and a gap-tooth scheme to efficiently use a limited amount of kinetic Monte Carlo simulations. In general the stochastic kinetic Monte Carlo results do not obey mass conservation so that unphysical accumulation of mass could occur in the reactor. We have developed a method to perform mass balance corrections that is based on a stoichiometry matrix and a least-squares problem that is reduced to a non-singular set of linear equations that is applicable to any surface catalyzed reaction. The implementation of these methods is validated by comparing numerical results of a reactor simulation with a unimolecular reaction to an analytical solution. Furthermore, the method is applied to two reaction mechanisms. The first is the ZGB model for CO oxidation in which inevitable poisoning of the catalyst limits the performance of the reactor. The second is a model for the oxidation of NO on a Pt(111) surface, which becomes active due to lateral interaction at high coverages of oxygen. This reaction model is based on ab initio density functional theory calculations from literature.

  14. Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce–W–O catalyst system

    NASA Astrophysics Data System (ADS)

    Sugiura, Kei; Ogo, Shuhei; Iwasaki, Kousei; Yabe, Tomohiro; Sekine, Yasushi

    2016-04-01

    We examined oxidative coupling of methane (OCM) over various Ce–W–O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W–O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field.

  15. Coupling of kinetic Monte Carlo simulations of surface reactions to transport in a fluid for heterogeneous catalytic reactor modeling

    NASA Astrophysics Data System (ADS)

    Schaefer, C.; Jansen, A. P. J.

    2013-02-01

    We have developed a method to couple kinetic Monte Carlo simulations of surface reactions at a molecular scale to transport equations at a macroscopic scale. This method is applicable to steady state reactors. We use a finite difference upwinding scheme and a gap-tooth scheme to efficiently use a limited amount of kinetic Monte Carlo simulations. In general the stochastic kinetic Monte Carlo results do not obey mass conservation so that unphysical accumulation of mass could occur in the reactor. We have developed a method to perform mass balance corrections that is based on a stoichiometry matrix and a least-squares problem that is reduced to a non-singular set of linear equations that is applicable to any surface catalyzed reaction. The implementation of these methods is validated by comparing numerical results of a reactor simulation with a unimolecular reaction to an analytical solution. Furthermore, the method is applied to two reaction mechanisms. The first is the ZGB model for CO oxidation in which inevitable poisoning of the catalyst limits the performance of the reactor. The second is a model for the oxidation of NO on a Pt(111) surface, which becomes active due to lateral interaction at high coverages of oxygen. This reaction model is based on ab initio density functional theory calculations from literature.

  16. Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce–W–O catalyst system

    PubMed Central

    Sugiura, Kei; Ogo, Shuhei; Iwasaki, Kousei; Yabe, Tomohiro; Sekine, Yasushi

    2016-01-01

    We examined oxidative coupling of methane (OCM) over various Ce–W–O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W–O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field. PMID:27118726

  17. Catalytic destruction of brominated aromatic compounds studied in a catalyst microbed coupled to gas chromatography/mass spectrometry.

    PubMed

    Blazsó, Marianne; Czégény, Zsuzsanna

    2006-10-13

    The capability of solid porous catalysts has been studied for the destruction or modification of halogenated aromatic compounds contaminating the pyrolysis oil of recycled plastics from electronic waste. A fast and simple experimental procedure is carried out using a micropyrolyser coupled to GC-MS in such a way that catalyst microbed was placed in the sample tube of the pyrolyser. The pyrolysis products of polycarbonate blended with a frequently applied flame retardant tetrabromobisphenol A (TBBPA) and epoxy resin containing TBBPA monomer units have been analysed, and the brominated components were compared with the thermal decomposition products of TBBPA and its diallyl ether. When TBBPA vapour passes through molecular sieve 4A a slight debromination and a partial cleavage of bisphenol A into phenols occur. Over molecular sieves of larger pore size (13X and NaY zeolite) an important decrease of TBBPA amount is observed indicating effective trapping ability of these catalysts of basic character for brominated aromatic compounds. A total chemical modification of the vapour was achieved by Al-MCM-41 catalyst that split TBBPA into bromophenols. Analogous results were obtained by carrying out similar experiments on diallyl ether of TBBPA. Moreover, it was revealed that brominated bisphenol A compounds are modified essentially the same way, either evaporated or evolved from a polycarbonate blend or produced by pyrolysis from an epoxy resin.

  18. Evolution of catalytic function

    NASA Technical Reports Server (NTRS)

    Joyce, G. F.

    1993-01-01

    An RNA-based evolution system was constructed in the laboratory and used to develop RNA enzymes with novel catalytic function. By controlling the nature of the catalytic task that the molecules must perform in order to survive, it is possible to direct the evolving population toward the expression of some desired catalytic behavior. More recently, this system has been coupled to an in vitro translation procedure, raising the possibility of evolving protein enzymes in the laboratory to produce novel proteins with desired catalytic properties. The aim of this line of research is to reduce darwinian evolution, the fundamental process of biology, to a laboratory procedure that can be made to operate in the service of organic synthesis.

  19. Fundamental studies of the mechanism of catalytic reactions with catalysts effective in the gasification of carbon solids and the oxidative coupling of methane. Quarterly report, 1 January--31 March 1994

    SciTech Connect

    Iglesia, E.; Heinemann, H.; Perry, D.L.

    1994-03-01

    This report describes work in progress on three tasks: (1) Catalytic steam gasification of coals and cokes; (2) Oxidative coupling of methane; and (3) Synthesis and characterization of catalysts. Since Task 1 is complete, a final report has been written. This report describes membrane reactors, cyclic methane conversion reactors, theoretical descriptions of reaction-separation schemes, and time-space relationships in cyclic and membrane reactors, all subtasks of Task 2. Initial studies under Task 3 are briefly described.

  20. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  1. Close-coupled Catalytic Two-Stage Liquefaction (CTSL{trademark}) process bench studies. Final report, [October 1, 1988--July 31, 1993

    SciTech Connect

    Comolli, A.G.; Johanson, E.S.; Karolkiewicz, W.F.; Lee, L.K.; Popper, G.A.; Stalzer, R.H.; Smith, T.O.

    1993-06-01

    This is the final report of a four year and ten month contract starting on October 1, 1988 to July 31, 1993 with the US Department of Energy to study and improve Close-Coupled Catalytic Two-Stage Direct Liquefaction of coal by producing high yields of distillate with improved quality at lower capital and production costs in comparison to existing technologies. Laboratory, Bench and PDU scale studies on sub-bituminous and bituminous coals are summarized and referenced in this volume. Details are presented in the three topical reports of this contract; CTSL Process Bench Studies and PDU Scale-Up with Sub-Bituminous Coal-DE-88818-TOP-1, CTSL Process Bench Studies with Bituminous Coal-DE-88818-TOP-2, and CTSL Process Laboratory Scale Studies, Modelling and Technical Assessment-DE-88818-TOP-3. Results are summarized on experiments and studies covering several process configurations, cleaned coals, solid separation methods, additives and catalysts both dispersed and supported. Laboratory microautoclave scale experiments, economic analysis and modelling studies are also included along with the PDU-Scale-Up of the CTSL processing of sub-bituminous Black Thunder Mine Wyoming coal. During this DOE/HRI effort, high distillate yields were maintained at higher throughput rates while quality was markedly improved using on-line hydrotreating and cleaned coals. Solid separations options of filtration and delayed coking were evaluated on a Bench-Scale with filtration successfully scaled to a PDU demonstration. Directions for future direct coal liquefaction related work are outlined herein based on the results from this and previous programs.

  2. Catalytic membranes beckon

    SciTech Connect

    Caruana, C.M.

    1994-11-01

    Chemical engineers here and abroad are finding that the marriage of catalysts and membranes holds promise for faster and more specific reactions, although commercialization of this technology is several years away. Catalytic membrane reactors (CMRs) combine a heterogeneous catalyst and a permselective membrane. Reactions performed by CMRs provide higher yields--sometimes as much as 50% higher--because of better reaction selectivity--as opposed to separation selectivity. CMRs also can work at very high temperatures, using ceramic materials that would not be possible with organic membranes. Although the use of CMRs is not widespread presently, the development of new membranes--particularly porous ceramic and zeolite membranes--will increase the potential to improve yields of many catalytic processes. The paper discusses ongoing studies, metal and advanced materials for membranes, the need for continued research, hydrogen recovery from coal-derived gases, catalytic oxidation of sulfides, CMRs for water purification, and oxidative coupling of methane.

  3. Total Synthesis of Macrocarpines D and E via an Enolate-Driven Copper-Mediated Cross-Coupling Process: Replacement of Catalytic Palladium with Copper Iodide.

    PubMed

    Rahman, M Toufiqur; Deschamps, Jeffrey R; Imler, Gregory H; Schwabacher, Alan W; Cook, James M

    2016-09-01

    An enolate driven copper-mediated cross-coupling process enabled cheaper and greener access to the key pentacyclic intermediates required for the enantiospecific total synthesis of a number of C-19 methyl substituted sarpagine/macroline indole alkaloids. Replacement of palladium (60-68%) with copper iodide (82-89%) resulted in much higher yields. The formation of an unusual 7-membered cross-coupling product was completely inhibited by using TEMPO as a radical scavenger. Further functionalization led to the first enantiospecific total synthesis of macrocarpines D and E. PMID:27526647

  4. Catalytic reactor

    SciTech Connect

    Aaron, Timothy Mark; Shah, Minish Mahendra; Jibb, Richard John

    2009-03-10

    A catalytic reactor is provided with one or more reaction zones each formed of set(s) of reaction tubes containing a catalyst to promote chemical reaction within a feed stream. The reaction tubes are of helical configuration and are arranged in a substantially coaxial relationship to form a coil-like structure. Heat exchangers and steam generators can be formed by similar tube arrangements. In such manner, the reaction zone(s) and hence, the reactor is compact and the pressure drop through components is minimized. The resultant compact form has improved heat transfer characteristics and is far easier to thermally insulate than prior art compact reactor designs. Various chemical reactions are contemplated within such coil-like structures such that as steam methane reforming followed by water-gas shift. The coil-like structures can be housed within annular chambers of a cylindrical housing that also provide flow paths for various heat exchange fluids to heat and cool components.

  5. Role of Ag2S coupling on enhancing the visible-light-induced catalytic property of TiO2 nanorod arrays

    PubMed Central

    Li, Zhengcao; Xiong, Shan; Wang, Guojing; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    In order to obtain a better photocatalytic performance under visible light, Ag2S-coupled TiO2 nanorod arrays (NRAs) were prepared through the electron beam deposition with glancing angle deposition (GLAD) technique, annealing in air, followed by the successive ionic layer absorption and reaction (SILAR) method. The properties of the photoelectrochemical and photocatalytic degradation of methyl orange (MO) were thus conducted. The presence of Ag2S on TiO2 NRAs was observed to have a significant improvement on the response to visible light. It’s resulted from that Ag2S coupling can improve the short circuit photocurrent density and enhance the photocatalytic activity remarkably. PMID:26790759

  6. Green synthesis of CuO nanoparticles by aqueous extract of Anthemis nobilis flowers and their catalytic activity for the A³ coupling reaction.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar

    2015-12-01

    CuO nanoparticles (NPs) were prepared by Anthemis nobilis flowers extract as a reducing and stabilizing agent and employed in catalyzing an aldehyde-amine-alkyne coupling reaction. The synthesized CuO NPs was characterized by SEM, EDS, XRD, FT-IR and UV-visible techniques. A diverse range of propargylamines were obtained in a good to high yield. Furthermore, the separation and reuse of CuO NPs was very simple, effective and economical.

  7. Selective extraction and release using (EDTA-Ni)-layered double hydroxide coupled with catalytic oxidation of 3,3',5,5'-tetramethylbenzidine for sensitive detection of copper ion.

    PubMed

    Tang, Sheng; Chang, Yuepeng; Chia, Guo Hui; Lee, Hian Kee

    2015-07-23

    Copper is an important heavy metal in various biological processes. Many methods have been developed for detecting of copper ions (Cu(2+)) in aqueous samples. However, an easy, cheap, selective and sensitive method is still desired. In this study, a selective extraction-release-catalysis approach has been developed for sensitive detection of copper ion. Ethylenediaminetetraacetic acid (EDTA) chelated with nickel ion (Ni(2+)) were intercalated in a layered double hydroxide via a co-precipitation reaction. The product was subsequently applied as sorbent in dispersive solid-phase extraction for the enrichment of Cu(2+) at pH 6. Since Cu(2+) has a stronger complex formation constant with EDTA, Ni(2+) exchanged with Cu(2+) selectively. The resulting sorbent containing Cu(2+) was transferred to catalyze the 3,3',5,5'-tetramethylbenzidine oxidation reaction, since Cu(2+) could be released by the sorbent effectively and has high catalytic ability for the reaction. Blue light emitted from the oxidation product was measured by ultraviolet-visible spectrophotometry for the determination of Cu(2+). The extraction temperature, extraction time, and catalysis time were optimized. The results showed that this method provided a low limit of detection of 10nM, a wide linear range (0.05-100μM) and good linearity (r(2)=0.9977). The optimized conditions were applied to environmental water samples. Using Cu(2+) as an example, this work provided a new and interesting approach for the convenient and efficient detection of metal cations in aqueous samples. PMID:26231895

  8. Selective extraction and release using (EDTA-Ni)-layered double hydroxide coupled with catalytic oxidation of 3,3',5,5'-tetramethylbenzidine for sensitive detection of copper ion.

    PubMed

    Tang, Sheng; Chang, Yuepeng; Chia, Guo Hui; Lee, Hian Kee

    2015-07-23

    Copper is an important heavy metal in various biological processes. Many methods have been developed for detecting of copper ions (Cu(2+)) in aqueous samples. However, an easy, cheap, selective and sensitive method is still desired. In this study, a selective extraction-release-catalysis approach has been developed for sensitive detection of copper ion. Ethylenediaminetetraacetic acid (EDTA) chelated with nickel ion (Ni(2+)) were intercalated in a layered double hydroxide via a co-precipitation reaction. The product was subsequently applied as sorbent in dispersive solid-phase extraction for the enrichment of Cu(2+) at pH 6. Since Cu(2+) has a stronger complex formation constant with EDTA, Ni(2+) exchanged with Cu(2+) selectively. The resulting sorbent containing Cu(2+) was transferred to catalyze the 3,3',5,5'-tetramethylbenzidine oxidation reaction, since Cu(2+) could be released by the sorbent effectively and has high catalytic ability for the reaction. Blue light emitted from the oxidation product was measured by ultraviolet-visible spectrophotometry for the determination of Cu(2+). The extraction temperature, extraction time, and catalysis time were optimized. The results showed that this method provided a low limit of detection of 10nM, a wide linear range (0.05-100μM) and good linearity (r(2)=0.9977). The optimized conditions were applied to environmental water samples. Using Cu(2+) as an example, this work provided a new and interesting approach for the convenient and efficient detection of metal cations in aqueous samples.

  9. TDLAS-based NH3 mole fraction measurement for exhaust diagnostics during selective catalytic reduction using a fiber-coupled 2.2-µm DFB diode laser

    NASA Astrophysics Data System (ADS)

    Stritzke, Felix; Diemel, Oliver; Wagner, Steven

    2015-04-01

    A new developed tunable diode laser spectrometer for the measurement of ammonia (NH3) mole fractions in exhaust gas matrices with strong CO2 and H2O background at temperatures up to 800 K is presented. In situ diagnostics in harsh exhaust environments during SCR after treatment are enabled by the use of ammonia transitions in the ν2 + ν3 near-infrared band around 2300 nm. Therefore, three lines have been selected, coinciding near 2200.5 nm (4544.5 cm-1) with rather weak temperature dependency and minimal interference with CO2 and H2O. A fiber-coupled 2.2-μm distributed feedback laser diode was used and attached to the hot gas flow utilizing adjustable gas tight high-temperature fiber ports. The spectrometer spans four coplanar optical channels across the measurement plane and simultaneously detects the direct absorption signal via a fiber-coupled detector unit. An exhaust simulation test rig was used to characterize the spectrometer's performance in ammonia-doped hot gas environments. We achieved a temporal resolution of 13 Hz and temperature-dependent precisions of NH3 mole fraction ranging from 50 to 70 ppmV. There the spectrometer achieved normalized ammonia detection limits of 7-10 and 2-3.

  10. A facile method for the synthesis of copper modified amine-functionalized mesoporous zirconia and its catalytic evaluation in C-S coupling reaction.

    PubMed

    Mallick, Sujata; Rana, Surjyakanta; Parida, Kulamani

    2011-09-28

    A new copper modified amine functionalized zirconia has been synthesized by a co-condensation method using zirconium butoxide and aminopropyltriethoxy-silane (APTES) in the presence of a cationic surfactant CTAB followed by impregnation of copper. Nitrogen adsorption-desorption, X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), (13)C nuclear magnetic resonance (NMR), scanning electron micrography (SEM), transmittance electron micrography (TEM), thermo gravimetric analysis-differential thermal analysis (TGA-DTA), X-ray photoelectron spectroscopy (XPS) and UV-vis DRS spectroscopic tools are used to characterize the materials. FT-IR and DRS results indicated the incorporation of Cu and amino groups on the surface of zirconia. This Cu-anchored mesoporous material acts as an efficient, reusable catalyst in the aryl-sulfur coupling reaction between aryl iodide and thiophenol for the synthesis of value added diarylsulfides. PMID:21826356

  11. Raney nickel catalytic device

    DOEpatents

    O'Hare, Stephen A.

    1978-01-01

    A catalytic device for use in a conventional coal gasification process which includes a tubular substrate having secured to its inside surface by expansion a catalytic material. The catalytic device is made by inserting a tubular catalytic element, such as a tubular element of a nickel-aluminum alloy, into a tubular substrate and heat-treating the resulting composite to cause the tubular catalytic element to irreversibly expand against the inside surface of the substrate.

  12. Cyclometalated iridium complexes of bis(aryl) phosphine ligands: catalytic C-H/C-D exchanges and C-C coupling reactions.

    PubMed

    Campos, Jesús; Espada, María F; López-Serrano, Joaquín; Carmona, Ernesto

    2013-06-01

    This work details the synthesis and structural identification of a series of complexes of the (η(5)-C5Me5)Ir(III) unit coordinated to cyclometalated bis(aryl)phosphine ligands, PR'(Ar)2, for R' = Me and Ar = 2,4,6-Me3C6H2, 1b; 2,6-Me2-4-OMe-C6H2, 1c; 2,6-Me2-4-F-C6H2, 1d; R' = Et, Ar = 2,6-Me2C6H3, 1e. Both chloride- and hydride-containing compounds, 2b-2e and 3b-3e, respectively, are described. Reactions of chlorides 2 with NaBArF (BArF = B(3,5-C6H3(CF3)2)4) in the presence of CO form cationic carbonyl complexes, 4(+), with ν(CO) values in the narrow interval 2030-2040 cm(-1), indicating similar π-basicity of the Ir(III) center of these complexes. In the absence of CO, NaBArF forces κ(4)-P,C,C',C″ coordination of the metalated arm (studied for the selected complexes 5b, 5d, and 5e), a binding mode so far encountered only when the phosphine contains two benzylic groups. A base-catalyzed intramolecular, dehydrogenative, C-C coupling reaction converts the κ(4) species 5d and 5e into the corresponding hydrido phosphepine complexes 6d and 6e. Using CD3OD as the source of deuterium, the chlorides 2 undergo deuteration of their 11 benzylic positions whereas hydrides 3 experience only D incorporation into the Ir-H and Ir-CH2 sites. Mechanistic schemes that explain this diversity have come to light thanks to experimental and theoretical DFT studies that are also reported. PMID:23675910

  13. The catalytic effect of sodium and lithium ions on coupled sorption-reduction of chromate at the biotite edge-fluid interface

    NASA Astrophysics Data System (ADS)

    Ilton, Eugene S.; Veblen, David R.; Moses, Carl O.; Raeburn, Stuart P.

    1997-09-01

    Large single crystals of biotite and near-endmember phlogopite were reacted with aqueous solutions bearing 20 μM Cr(VI) and different concentrations of NaCl, LiCl, RbCl, CsCl, NaClO 4, and Na 2SO 4. Solutions were maintained at 25 ± 0.5°C, 1 atm, and pH = 4.00 ± 0.02. Samples were extracted from the reaction chamber at 1, 3, 5, 10, and 20 h. The edges and basal planes of the reacted micas were analyzed by X-ray photoelectron spectroscopy (XPS) for major elements and Cr. XPS analyses of biotite show trivalent chromium on edge surfaces but no detectable chromium on the basal plane. XPS analyses of near-endmember phlogopites that were reacted in the same experiments as biotite showed no detectable Cr on either the basal plane or edge surfaces. Increasing Na and Li salt concentrations increased the rate of coupled sorption-reduction of chromate at the biotite edge-fluid interface, where the order of effectiveness was NaCl ˜ NaClO 4 > Na 2SO 4 > LiCl. In contrast, no Cr was detected on mica edges after reaction in RbCl and CsCl solutions. Comparison of equimolar NaCl and LiCl experiments indicate that the active agent is Na and Li, not ionic strength or the anion. Sulfate tends to block the reaction more so than chloride. We conclude that it is the substitution of hydrated cations for interlayer K in biotite that enhances the heterogeneous reduction of chromate at the biotite edge-fluid interface.

  14. Switchable catalytic DNA catenanes.

    PubMed

    Hu, Lianzhe; Lu, Chun-Hua; Willner, Itamar

    2015-03-11

    Two-ring interlocked DNA catenanes are synthesized and characterized. The supramolecular catenanes show switchable cyclic catalytic properties. In one system, the catenane structure is switched between a hemin/G-quadruplex catalytic structure and a catalytically inactive state. In the second catenane structure the catenane is switched between a catalytically active Mg(2+)-dependent DNAzyme-containing catenane and an inactive catenane state. In the third system, the interlocked catenane structure is switched between two distinct catalytic structures that include the Mg(2+)- and the Zn(2+)-dependent DNAzymes. PMID:25642796

  15. Topological entropy of catalytic sets: Hypercycles revisited

    NASA Astrophysics Data System (ADS)

    Sardanyés, Josep; Duarte, Jorge; Januário, Cristina; Martins, Nuno

    2012-02-01

    The dynamics of catalytic networks have been widely studied over the last decades because of their implications in several fields like prebiotic evolution, virology, neural networks, immunology or ecology. One of the most studied mathematical bodies for catalytic networks was initially formulated in the context of prebiotic evolution, by means of the hypercycle theory. The hypercycle is a set of self-replicating species able to catalyze other replicator species within a cyclic architecture. Hypercyclic organization might arise from a quasispecies as a way to increase the informational containt surpassing the so-called error threshold. The catalytic coupling between replicators makes all the species to behave like a single and coherent evolutionary multimolecular unit. The inherent nonlinearities of catalytic interactions are responsible for the emergence of several types of dynamics, among them, chaos. In this article we begin with a brief review of the hypercycle theory focusing on its evolutionary implications as well as on different dynamics associated to different types of small catalytic networks. Then we study the properties of chaotic hypercycles with error-prone replication with symbolic dynamics theory, characterizing, by means of the theory of topological Markov chains, the topological entropy and the periods of the orbits of unimodal-like iterated maps obtained from the strange attractor. We will focus our study on some key parameters responsible for the structure of the catalytic network: mutation rates, autocatalytic and cross-catalytic interactions.

  16. Controlling the catalytic aerobic oxidation of phenols.

    PubMed

    Esguerra, Kenneth Virgel N; Fall, Yacoub; Petitjean, Laurène; Lumb, Jean-Philip

    2014-05-28

    The oxidation of phenols is the subject of extensive investigation, but there are few catalytic aerobic examples that are chemo- and regioselective. Here we describe conditions for the ortho-oxygenation or oxidative coupling of phenols under copper (Cu)-catalyzed aerobic conditions that give rise to ortho-quinones, biphenols or benzoxepines. We demonstrate that each product class can be accessed selectively by the appropriate choice of Cu(I) salt, amine ligand, desiccant and reaction temperature. In addition, we evaluate the effects of substituents on the phenol and demonstrate their influence on selectivity between ortho-oxygenation and oxidative coupling pathways. These results create an important precedent of catalyst control in the catalytic aerobic oxidation of phenols and set the stage for future development of catalytic systems and mechanistic investigations. PMID:24784319

  17. Catalytic Organometallic Reactions of Ammonia

    PubMed Central

    Klinkenberg, Jessica L.

    2012-01-01

    Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466

  18. Rich catalytic injection

    DOEpatents

    Veninger, Albert

    2008-12-30

    A gas turbine engine includes a compressor, a rich catalytic injector, a combustor, and a turbine. The rich catalytic injector includes a rich catalytic device, a mixing zone, and an injection assembly. The injection assembly provides an interface between the mixing zone and the combustor. The injection assembly can inject diffusion fuel into the combustor, provides flame aerodynamic stabilization in the combustor, and may include an ignition device.

  19. Two stage catalytic combustor

    NASA Technical Reports Server (NTRS)

    Alvin, Mary Anne (Inventor); Bachovchin, Dennis (Inventor); Smeltzer, Eugene E. (Inventor); Lippert, Thomas E. (Inventor); Bruck, Gerald J. (Inventor)

    2010-01-01

    A catalytic combustor (14) includes a first catalytic stage (30), a second catalytic stage (40), and an oxidation completion stage (49). The first catalytic stage receives an oxidizer (e.g., 20) and a fuel (26) and discharges a partially oxidized fuel/oxidizer mixture (36). The second catalytic stage receives the partially oxidized fuel/oxidizer mixture and further oxidizes the mixture. The second catalytic stage may include a passageway (47) for conducting a bypass portion (46) of the mixture past a catalyst (e.g., 41) disposed therein. The second catalytic stage may have an outlet temperature elevated sufficiently to complete oxidation of the mixture without using a separate ignition source. The oxidation completion stage is disposed downstream of the second catalytic stage and may recombine the bypass portion with a catalyst exposed portion (48) of the mixture and complete oxidation of the mixture. The second catalytic stage may also include a reticulated foam support (50), a honeycomb support, a tube support or a plate support.

  20. Catalytic distillation structure

    DOEpatents

    Smith, Jr., Lawrence A.

    1984-01-01

    Catalytic distillation structure for use in reaction distillation columns, a providing reaction sites and distillation structure and consisting of a catalyst component and a resilient component intimately associated therewith. The resilient component has at least about 70 volume % open space and being present with the catalyst component in an amount such that the catalytic distillation structure consist of at least 10 volume % open space.

  1. Catalytic distillation process

    DOEpatents

    Smith, Jr., Lawrence A.

    1982-01-01

    A method for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C.sub.4 feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

  2. Catalytic distillation process

    DOEpatents

    Smith, L.A. Jr.

    1982-06-22

    A method is described for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C[sub 4] feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

  3. Catalytic distillation structure

    DOEpatents

    Smith, L.A. Jr.

    1984-04-17

    Catalytic distillation structure is described for use in reaction distillation columns, and provides reaction sites and distillation structure consisting of a catalyst component and a resilient component intimately associated therewith. The resilient component has at least about 70 volume % open space and is present with the catalyst component in an amount such that the catalytic distillation structure consists of at least 10 volume % open space. 10 figs.

  4. Clean catalytic combustor program

    NASA Technical Reports Server (NTRS)

    Ekstedt, E. E.; Lyon, T. F.; Sabla, P. E.; Dodds, W. J.

    1983-01-01

    A combustor program was conducted to evolve and to identify the technology needed for, and to establish the credibility of, using combustors with catalytic reactors in modern high-pressure-ratio aircraft turbine engines. Two selected catalytic combustor concepts were designed, fabricated, and evaluated. The combustors were sized for use in the NASA/General Electric Energy Efficient Engine (E3). One of the combustor designs was a basic parallel-staged double-annular combustor. The second design was also a parallel-staged combustor but employed reverse flow cannular catalytic reactors. Subcomponent tests of fuel injection systems and of catalytic reactors for use in the combustion system were also conducted. Very low-level pollutant emissions and excellent combustor performance were achieved. However, it was obvious from these tests that extensive development of fuel/air preparation systems and considerable advancement in the steady-state operating temperature capability of catalytic reactor materials will be required prior to the consideration of catalytic combustion systems for use in high-pressure-ratio aircraft turbine engines.

  5. Catalytic combustion over hexaaluminates

    SciTech Connect

    Ramesh, K.S.; Kingsley, J.J.; Hubler, T.L.; McCready, D.E.; Cox, J.L.

    1997-12-31

    Combustion is the oldest and most extensively used process for the production of light, heat, and energy utilization. Mankind has sought to control combustion since prehistoric times to more effectively utilize the combustible material, control the products of combustion, and harness the energy released during combustion. Catalysts provide the means to control the reactions of combustion beyond what can be achieved in the homogeneous gas phase (1). Catalysts also enable operation outside the range of flammability limits and control atmospheric pollutants of combustion, mainly NO{sub x}, carbon monoxide, and particles of incomplete combustion (soot). The major technical difficulty that has hindered widespread application of catalytic combustion devices is their poor performance, particularly durability of their ceramic substrates and catalytically active phases in the high temperature environment. Catalytic combustion of hydrocarbons over metals and metal oxide catalysts has been explored extensively. Recent reviews of materials for high temperature catalytic combustion have been provided by Marcus et al. (2) and Trim (3). Hexaaluminates which show good thermal stability above 1200{degrees}C are one class of metal oxides receiving consideration for application in high temperature combustion devices. Matsuda et al. (4) have developed thermally stable La-hexaaluminates with the same layer structure as Ba-hexaaluminate and have investigated their catalytic application. Machida et al. (5-7) have investigated the catalytic properties of a number of hexaaluminates of BaMAl{sub 11}O{sub 19-{alpha}}(M=Cr, Mn,Fe,Co,Ni). Here we report the synthesis, properties and catalytic combustion of some new hexaaluminates.

  6. Transient catalytic combustor model

    NASA Technical Reports Server (NTRS)

    Tien, J. S.

    1981-01-01

    A quasi-steady gas phase and thermally thin substrate model is used to analyze the transient behavior of catalytic monolith combustors in fuel lean operation. The combustor response delay is due to the substrate thermal inertia. Fast response is favored by thin substrate, short catalytic bed length, high combustor inlet and final temperatures, and small gas channel diameters. The calculated gas and substrate temperature time history at different axial positions provides an understanding of how the catalytic combustor responds to an upstream condition change. The computed results also suggest that the gas residence times in the catalytic bed in the after bed space are correlatable with the nondimensional combustor response time. The model also performs steady state combustion calculations; and the computed steady state emission characteristics show agreement with available experimental data in the range of parameters covered. A catalytic combustor design for automotive gas turbine engine which has reasonably fast response ( 1 second) and can satisfy the emission goals in an acceptable total combustor length is possible.

  7. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

    2013-08-27

    A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

  8. Catalytic coherence transformations

    NASA Astrophysics Data System (ADS)

    Bu, Kaifeng; Singh, Uttam; Wu, Junde

    2016-04-01

    Catalytic coherence transformations allow the otherwise impossible state transformations using only incoherent operations with the aid of an auxiliary system with finite coherence that is not being consumed in any way. Here we find the necessary and sufficient conditions for the deterministic and stochastic catalytic coherence transformations between a pair of pure quantum states. In particular, we show that the simultaneous decrease of a family of Rényi entropies of the diagonal parts of the states under consideration is a necessary and sufficient condition for the deterministic catalytic coherence transformations. Similarly, for stochastic catalytic coherence transformations we find the necessary and sufficient conditions for achieving a higher optimal probability of conversion. We thus completely characterize the coherence transformations among pure quantum states under incoherent operations. We give numerous examples to elaborate our results. We also explore the possibility of the same system acting as a catalyst for itself and find that indeed self-catalysis is possible. Further, for the cases where no catalytic coherence transformation is possible we provide entanglement-assisted coherence transformations and find the necessary and sufficient conditions for such transformations.

  9. Catalytic hydrotreating process

    DOEpatents

    Karr, Jr., Clarence; McCaskill, Kenneth B.

    1978-01-01

    Carbonaceous liquids boiling above about 300.degree. C such as tars, petroleum residuals, shale oils and coal-derived liquids are catalytically hydrotreated by introducing the carbonaceous liquid into a reaction zone at a temperature in the range of 300.degree. to 450.degree. C and a pressure in the range of 300 to 4000 psig for effecting contact between the carbonaceous liquid and a catalytic transition metal sulfide in the reaction zone as a layer on a hydrogen permeable transition metal substrate and then introducing hydrogen into the reaction zone by diffusing the hydrogen through the substrate to effect the hydrogenation of the carbonaceous liquid in the presence of the catalytic sulfide layer.

  10. Catalytic molecular beacons.

    PubMed

    Stojanovic, M N; de Prada, P; Landry, D W

    2001-06-01

    We have constructed catalytic molecular beacons from a hammerhead-type deoxyribozyme by a modular design. The deoxyribozyme was engineered to contain a molecular beacon stem-loop module that, when closed, inhibits the deoxyribozyme module and is complementary to a target oligonucleotide. Binding of target oligonucleotides opens the beacon stem-loop and allosterically activates the deoxyribozyme module, which amplifies the recognition event through cleavage of a doubly labeled fluorescent substrate. The customized modular design of catalytic molecular beacons allows for any two single-stranded oligonucleotide sequences to be distinguished in homogenous solution in a single step. Our constructs demonstrate that antisense conformational triggers based on molecular beacons can be used to initiate catalytic events. The selectivity of the system is sufficient for analytical applications and has potential for the construction of deoxyribozyme-based drug delivery tools specifically activated in cells containing somatic mutations.

  11. Fluid catalytic cracking

    SciTech Connect

    Bartley, B.H.; Petty, R.H.

    1982-08-17

    Gaseous sulfur compounds are removed from a sulfur-containing gas mixture by reacting sulfur oxides in the gas mixture with alumina in association with bismuth. The process is particularly useful in fluid catalytic cracking of sulfur-containing petroleum charge stocks wherein sulfur is contained in coke deposited on the fluidized cracking catalyst. By the process of this invention, sulfur oxides may be removed from regenerator off-gases from a fluidized catalytic cracking unit by incorporating particulate alumina impregnated with bismuth in particulate cracking catalyst whereby sulfur oxides generated in the regeneration of the catalyst are reacted with bismuth-impregnated alumina. Sulfur oxides produced during regeneration of the catalyst by burning the coke with air are captured and converted to hydrogen sulfide in the cracking reactor. The hydrogen sulfide so produced is readily separated from petroleum products of the catalytic cracking reaction process.

  12. Steam reformer with catalytic combustor

    DOEpatents

    Voecks, Gerald E.

    1990-03-20

    A steam reformer is disclosed having an annular steam reforming catalyst bed formed by concentric cylinders and having a catalytic combustor located at the center of the innermost cylinder. Fuel is fed into the interior of the catalytic combustor and air is directed at the top of the combustor, creating a catalytic reaction which provides sufficient heat so as to maintain the catalytic reaction in the steam reforming catalyst bed. Alternatively, air is fed into the interior of the catalytic combustor and a fuel mixture is directed at the top. The catalytic combustor provides enhanced radiant and convective heat transfer to the reformer catalyst bed.

  13. Steam reformer with catalytic combustor

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E. (Inventor)

    1990-01-01

    A steam reformer is disclosed having an annular steam reforming catalyst bed formed by concentric cylinders and having a catalytic combustor located at the center of the innermost cylinder. Fuel is fed into the interior of the catalytic combustor and air is directed at the top of the combustor, creating a catalytic reaction which provides sufficient heat so as to maintain the catalytic reaction in the steam reforming catalyst bed. Alternatively, air is fed into the interior of the catalytic combustor and a fuel mixture is directed at the top. The catalytic combustor provides enhanced radiant and convective heat transfer to the reformer catalyst bed.

  14. Fluid catalytic cracking

    SciTech Connect

    Petty, R.H.; Bartley, B.H.

    1984-05-01

    A fluid catalytic cracking process is disclosed for sulfur-containing petroleum charge stocks. Sulfur contained in coke deposited on the fluidized cracking catalyst in the reactor is converted to sulfur oxides in the regenerator and removed from regenerator off-gases by incorporating a composite of alumina and bismuth oxides in a particulate cracking catalyst. Sulfur oxides produced during regeneration of the catalyst by burning the coke with air in the regenerator are captured by the alumina-bismuth oxides composite and converted to hydrogen sulfide in the cracking reactor. The hydrogen sulfide so produced is readily separated from petroleum products of the catalytic cracking reaction process.

  15. Catalytic coal liquefaction process

    DOEpatents

    Garg, D.; Sunder, S.

    1986-12-02

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids. 1 fig.

  16. Catalytic coal liquefaction process

    DOEpatents

    Garg, Diwakar; Sunder, Swaminathan

    1986-01-01

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids.

  17. Catalytic efficiency of designed catalytic proteins

    PubMed Central

    Korendovych, Ivan V; DeGrado, William F

    2014-01-01

    The de novo design of catalysts that mimic the affinity and specificity of natural enzymes remains one of the Holy Grails of chemistry. Despite decades of concerted effort we are still unable to design catalysts as efficient as enzymes. Here we critically evaluate approaches to (re)design of novel catalytic function in proteins using two test cases: Kemp elimination and ester hydrolysis. We show that the degree of success thus far has been modest when the rate enhancements seen for the designed proteins are compared with the rate enhancements by small molecule catalysts in solvents with properties similar to the active site. Nevertheless, there are reasons for optimism: the design methods are ever improving and the resulting catalyst can be efficiently improved using directed evolution. PMID:25048695

  18. Catalytic efficiency of designed catalytic proteins.

    PubMed

    Korendovych, Ivan V; DeGrado, William F

    2014-08-01

    The de novo design of catalysts that mimic the affinity and specificity of natural enzymes remains one of the Holy Grails of chemistry. Despite decades of concerted effort we are still unable to design catalysts as efficient as enzymes. Here we critically evaluate approaches to (re)design of novel catalytic function in proteins using two test cases: Kemp elimination and ester hydrolysis. We show that the degree of success thus far has been modest when the rate enhancements seen for the designed proteins are compared with the rate enhancements by small molecule catalysts in solvents with properties similar to the active site. Nevertheless, there are reasons for optimism: the design methods are ever improving and the resulting catalyst can be efficiently improved using directed evolution.

  19. Catalytic converter with thermoelectric generator

    SciTech Connect

    Parise, R.J.

    1998-07-01

    The unique design of an electrically heated catalyst (EHC) and the inclusion of an ECO valve in the exhaust of an internal combustion engine will meet the strict new emission requirements, especially at vehicle cold start, adopted by several states in this country as well as in Europe and Japan. The catalytic converter (CC) has been a most useful tool in pollution abatement for the automobile. But the emission requirements are becoming more stringent and, along with other improvements, the CC must be improved to meet these new standards. Coupled with the ECO valve, the EHC can meet these new emission limits. In an internal combustion engine vehicle (ICEV), approximately 80% of the energy consumed leaves the vehicle as waste heat: out the tail pipe, through the radiator, or convected/radiated off the engine. Included with the waste heat out the tail pipe are the products of combustion which must meet strict emission requirements. The design of a new CC is presented here. This is an automobile CC that has the capability of producing electrical power and reducing the quantity of emissions at vehicle cold start, the Thermoelectric Catalytic Power Generator. The CC utilizes the energy of the exothermic reactions that take place in the catalysis substrate to produce electrical energy with a thermoelectric generator. On vehicle cold start, the thermoelectric generator is used as a heat pump to heat the catalyst substrate to reduce the time to catalyst light-off. Thus an electrically heated catalyst (EHC) will be used to augment the abatement of tail pipe emissions. Included with the EHC in the exhaust stream of the automobile is the ECO valve. This valve restricts the flow of pollutants out the tail pipe of the vehicle for a specified amount of time until the EHC comes up to operating temperature. Then the ECO valve opens and allows the full exhaust, now treated by the EHC, to leave the vehicle.

  20. The evolution of catalytic function

    NASA Astrophysics Data System (ADS)

    Maurel, Marie-Christine; Ricard, Jacques

    2006-03-01

    It is very likely that the main driving force of enzyme evolution is the requirement to improve catalytic and regulatory efficiency which results from the intrinsic performance as well as from the spatial and functional organization of enzymes in living cells. Kinetic co-operativity may occur in simple monomeric proteins if they display “slow” conformational transitions, at the cost of catalytic efficiency. Oligomeric enzymes on the other hand can be both efficient and co-operative. We speculate that the main reason for the emergence of co-operative oligomeric enzymes is the need for catalysts that are both cooperative and efficient. As it is not useful for an enzyme to respond to a change of substrate concentration in a complex kinetic way, the emergence of symmetry has its probable origin in a requirement for “functional simplicity”. In a living cell, enzyme are associated with other macromolecules and membranes. The fine tuning of their activity may also be reached through mutations of the microenvironment. Our hypothesis is that these mutations are related to the vectorial transport of molecules, to achieve the hysteresis loops of enzyme reactions generated by the coupling of reaction and diffusion, through the co-operativity brought about by electric interactions between a charged substrate and a membrane, and last but not least, through oscillations. As the physical origins of these effects are very simple and do not require complex molecular devices, it is very likely that the functional advantage generated by the spatial and functional organization of enzyme molecules within the cell have appeared in prebiotic catalysis or very early during the primeval stages of biological evolution. We shall began this paper by presenting the nature of the probable earliest catalysts in the RNA world.

  1. A graphene-based smart catalytic system with superior catalytic performances and temperature responsive catalytic behaviors.

    PubMed

    Qi, Junjie; Lv, Weipeng; Zhang, Guanghui; Li, Yang; Zhang, Guoliang; Zhang, Fengbao; Fan, Xiaobin

    2013-07-21

    We have successfully developed a unique graphene-based smart catalytic system which consists of the graphene supported Au-Pt bimetallic nanocatalyst with a well-defined core-shell structure and a dextran-based temperature-responsive polymer. The unique catalytic system possesses excellent catalytic performances and the catalytic activities could be readily switched on or off at different temperature windows. PMID:23740038

  2. Catalytic thermal barrier coatings

    DOEpatents

    Kulkarni, Anand A.; Campbell, Christian X.; Subramanian, Ramesh

    2009-06-02

    A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

  3. Catalytic, hollow, refractory spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1987-01-01

    Improved, heterogeneous, refractory catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitable formed of a shell (12) of refractory such as alumina having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be itself catalytic or a catalytically active material coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  4. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J.; Hryn, John N.; Elam, Jeffrey W.

    2009-12-01

    A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

  5. A novel and versatile nanomachine for ultrasensitive and specific detection of microRNAs based on molecular beacon initiated strand displacement amplification coupled with catalytic hairpin assembly with DNAzyme formation.

    PubMed

    Yan, Yurong; Shen, Bo; Wang, Hong; Sun, Xue; Cheng, Wei; Zhao, Hua; Ju, Huangxian; Ding, Shijia

    2015-08-21

    MicroRNAs are small regulatory molecules that can be used as potential biomarkers of clinical diagnosis, and efforts have been directed towards the development of a simple, rapid, and sequence-selective analysis of microRNAs. Here, we report a simple and versatile colorimetric strategy for ultrasensitive and specific determination of microRNAs based on molecular beacon initiated strand displacement amplification (SDA) and catalytic hairpin assembly (CHA) with DNAzyme formation. The presence of target microRNAs triggers strand displacement amplification to release nicking DNA triggers, which initiate CHA to produce large amounts of CHA products. Meanwhile, the numerous CHA products can combine with hemin to form G-quadruplex/hemin DNAzyme, a well-known horseradish peroxidase (HRP) mimic, catalyzing a colorimetric reaction. Moreover, the purification of the SDA mixture has been developed for eliminating matrix interference to decrease nonspecific CHA products. Under the optimal conditions and using the promising amplification strategy, the established colorimetric nanomachine (biosensor) shows high sensitivity and selectivity in a dynamic response range from 5 fM to 5 nM with a detection limit as low as 1.7 fM (S/N = 3). In addition, a versatile colorimetric biosensor has been developed for detection of different miRNAs by only changing the miRNA-recognition domain of molecular beacon. Thus, this colorimetric biosensor may become a potential alternative tool for biomedical research and clinical molecular diagnostics.

  6. Catalytic hydrogenation of carbon monoxide

    SciTech Connect

    Wayland, B.B.

    1992-12-01

    This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

  7. Catalytic reforming methods

    DOEpatents

    Tadd, Andrew R; Schwank, Johannes

    2013-05-14

    A catalytic reforming method is disclosed herein. The method includes sequentially supplying a plurality of feedstocks of variable compositions to a reformer. The method further includes adding a respective predetermined co-reactant to each of the plurality of feedstocks to obtain a substantially constant output from the reformer for the plurality of feedstocks. The respective predetermined co-reactant is based on a C/H/O atomic composition for a respective one of the plurality of feedstocks and a predetermined C/H/O atomic composition for the substantially constant output.

  8. Preconversion catalytic deoxygenation of phenolic functional groups

    SciTech Connect

    Kubiak, C.P.

    1991-01-01

    The deoxygenation of phenols is a conceptually simple, but unusually difficult chemical transformation to achieve. Aryl carbon-oxygen bond cleavage is a chemical transformation of importance in coal liquefaction and the upgrading of coal liquids as well as in the synthesis of natural products. This proposed research offers the possibility of effecting the selective catalytic deoxygenation of phenolic functional groups using CO. A program of research for the catalytic deoxygenation of phenols, via a low energy mechanistic pathway that is based on the use of the CO/CO{sub 2} couple to remove phenolic oxygen atoms, is underway. We are focusing on systems which have significant promise as catalysts: Ir(triphos)OPh, (Pt(triphos)OPh){sup +} and Rh(triphos)OPh. Our studies of phenol deoxygenation focus on monitoring the reactions for the elementary processes upon which catalytic activity will depend: CO insertion into M-OPh bonds, CO{sub 2} elimination from aryloxy carbonyls {l brace}M-C(O)-O-Ph{r brace}, followed by formation of a coordinated benzyne intermediate.

  9. Catalytic applications of bio-inspired nanomaterials

    NASA Astrophysics Data System (ADS)

    Pacardo, Dennis Kien Balaong

    The biomimetic synthesis of Pd nanoparticles was presented using the Pd4 peptide, TSNAVHPTLRHL, isolated from combinatorial phage display library. Using this approach, nearly monodisperse and spherical Pd nanoparticles were generated with an average diameter of 1.9 +/- 0.4 nm. The peptide-based nanocatalyst were employed in the Stille coupling reaction under energy-efficient and environmentally friendly reaction conditions of aqueous solvent, room temperature and very low catalyst loading. To this end, the Pd nanocatalyst generated high turnover frequency (TOF) value and quantitative yields using ≥ 0.005 mol% Pd as well as catalytic activities with different aryl halides containing electron-withdrawing and electron-donating groups. The Pd4-capped Pd nanoparticles followed the atom-leaching mechanism and were found to be selective with respect to substrate identity. On the other hand, the naturally-occurring R5 peptide (SSKKSGSYSGSKGSKRRIL) was employed in the synthesis of biotemplated Pd nanomaterials which showed morphological changes as a function of Pd:peptide ratio. TOF analysis for hydrogenation of olefinic alcohols showed similar catalytic activity regardless of nanomorphology. Determination of catalytic properties of these bio-inspired nanomaterials are important as they serve as model system for alternative green catalyst with applications in industrially important transformations.

  10. Novel Catalytic Membrane Reactors

    SciTech Connect

    Stuart Nemser, PhD

    2010-10-01

    There are many industrial catalytic organic reversible reactions with amines or alcohols that have water as one of the products. Many of these reactions are homogeneously catalyzed. In all cases removal of water facilitates the reaction and produces more of the desired chemical product. By shifting the reaction to right we produce more chemical product with little or no additional capital investment. Many of these reactions can also relate to bioprocesses. Given the large number of water-organic compound separations achievable and the ability of the Compact Membrane Systems, Inc. (CMS) perfluoro membranes to withstand these harsh operating conditions, this is an ideal demonstration system for the water-of-reaction removal using a membrane reactor. Enhanced reaction synthesis is consistent with the DOE objective to lower the energy intensity of U.S. industry 25% by 2017 in accord with the Energy Policy Act of 2005 and to improve the United States manufacturing competitiveness. The objective of this program is to develop the platform technology for enhancing homogeneous catalytic chemical syntheses.

  11. Optical activity of catalytic elements of hetero-metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Antosiewicz, Tomasz J.; Apell, S. Peter; Wadell, Carl; Langhammer, Christoph

    2015-05-01

    Interaction of light with metals in the form of surface plasmons is used in a wide range of applications in which the scattering decay channel is important. The absorption channel is usually thought of as unwanted and detrimental to the efficiency of the device. This is true in many applications, however, recent studies have shown that maximization of the decay channel of surface plasmons has potentially significant uses. One of these is the creation of electron-hole pairs or hot electrons which can be used for e.g. catalysis. Here, we study the optical properties of hetero-metallic nanostructures that enhance light interaction with the catalytic elements of the nanostructures. A hybridized LSPR that matches the spectral characteristic of the light source is excited. This LSPR through coupling between the plasmonic elements maximizes light absorption in the catalytic part of the nanostructure. Numerically calculated visible light absorption in the catalytic nanoparticles is enhanced 12-fold for large catalytic disks and by more 30 for small nanoparticles on the order of 5 nm. In experiments we measure a sizable increase in the absorption cross section when small palladium nanoparticles are coupled to a large silver resonator. These observations suggest that heterometallic nanostructures can enhance catalytic reaction rates.

  12. Synthesis and Suzuki-Miyaura Cross-Coupling of Enantioenriched Secondary Potassium β-Trifluoroboratoamides: Catalytic, Asymmetric Conjugate Addition of Bisboronic Acid and Tetrakis(dimethylamino)diboron to α,β-Unsaturated Carbonyl Compounds.

    PubMed

    Molander, Gary A; Wisniewski, Steven R; Hosseini-Sarvari, Mona

    2013-10-11

    Enantioenriched potassium β-trifluoroboratoamides have been synthesized via an asymmetric, copper-catalyzed 1,4-addition of tetrahydroxydiboron (BBA) and tetrakis(dimethylamino)diboron to α,β-unsaturated amides. These dibora reagents provide access to the desired organotrifluoroborates using effective and atom economical sources of boron. The copper-catalyzed β-boration is extended to α,β-unsaturated ketones and esters. Desired potassium organotrifluoroborates are synthesized with yields up to 92% and enantiomeric ratios up to 98:2. The enantioenriched potassium β-trifluoroboratoamides are successfully cross-coupled with an array of aryl and heteroaryl chlorides in high yield with complete stereochemical fidelity as the transmetalation proceeds through an SE2 mechanism via an open transition state. PMID:24741373

  13. ``OPTICAL Catalytic Nanomotors''

    NASA Astrophysics Data System (ADS)

    Rosary-Oyong, Se, Glory

    D. Kagan, et.al, 2009:'' a motion-based chemical sensing involving fuel-driven nanomotors is demonstrated. The new protocol relies on the use of an optical microscope for tracking charge in the speed of nanowire motors in the presence of target analyte''. Synthetic nanomotors are propelled by catalytic decomposition of .. they do not require external electric, magnetic or optical fields as energy... Accompanying Fig 2.6(a) of optical micrograph of a partial monolayer of silica microbeads [J.Gibbs, 2011 ] retrieves WF Paxton:''rods were characterized by transmission electron & dark-field optical microscopy..'' & LF Valadares:''dimer due to the limited resolution of optical microscopy, however the result..'. Acknowledged to HE. Mr. Prof. SEDIONO M.P. TJONDRONEGORO.

  14. Bifunctional catalytic electrode

    NASA Technical Reports Server (NTRS)

    Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

    2005-01-01

    The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

  15. Catalytic hollow spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1989-01-01

    The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  16. Unsteady catalytic processes and sorption-catalytic technologies

    NASA Astrophysics Data System (ADS)

    Zagoruiko, A. N.

    2007-07-01

    Catalytic processes that occur under conditions of the targeted unsteady state of the catalyst are considered. The highest efficiency of catalytic processes was found to be ensured by a controlled combination of thermal non-stationarity and unsteady composition of the catalyst surface. The processes based on this principle are analysed, in particular, catalytic selective reduction of nitrogen oxides, deep oxidation of volatile organic impurities, production of sulfur by the Claus process and by hydrogen sulfide decomposition, oxidation of sulfur dioxide, methane steam reforming and anaerobic combustion, selective oxidation of hydrocarbons, etc.

  17. Catalytic Microtube Rocket Igniter

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Deans, Matthew C.

    2011-01-01

    Devices that generate both high energy and high temperature are required to ignite reliably the propellant mixtures in combustion chambers like those present in rockets and other combustion systems. This catalytic microtube rocket igniter generates these conditions with a small, catalysis-based torch. While traditional spark plug systems can require anywhere from 50 W to multiple kW of power in different applications, this system has demonstrated ignition at less than 25 W. Reactants are fed to the igniter from the same tanks that feed the reactants to the rest of the rocket or combustion system. While this specific igniter was originally designed for liquid methane and liquid oxygen rockets, it can be easily operated with gaseous propellants or modified for hydrogen use in commercial combustion devices. For the present cryogenic propellant rocket case, the main propellant tanks liquid oxygen and liquid methane, respectively are regulated and split into different systems for the individual stages of the rocket and igniter. As the catalyst requires a gas phase for reaction, either the stored boil-off of the tanks can be used directly or one stream each of fuel and oxidizer can go through a heat exchanger/vaporizer that turns the liquid propellants into a gaseous form. For commercial applications, where the reactants are stored as gases, the system is simplified. The resulting gas-phase streams of fuel and oxidizer are then further divided for the individual components of the igniter. One stream each of the fuel and oxidizer is introduced to a mixing bottle/apparatus where they are mixed to a fuel-rich composition with an O/F mass-based mixture ratio of under 1.0. This premixed flow then feeds into the catalytic microtube device. The total flow is on the order of 0.01 g/s. The microtube device is composed of a pair of sub-millimeter diameter platinum tubes connected only at the outlet so that the two outlet flows are parallel to each other. The tubes are each

  18. Catalytic Polymer Multilayer Shell Motors for Separation of Organics.

    PubMed

    Lin, Zhihua; Wu, Zhiguang; Lin, Xiankun; He, Qiang

    2016-01-26

    A catalytic polymer multilayer shell motor has been developed, which effects fast motion-based separation of charged organics in water. The shell motors are fabricated by sputtering platinum onto the exposed surface of silica templates embedded in Parafilm, followed by layer-by-layer assembly of polyelectrolyte multilayers to the templates. The catalytic shell motors display high bubble propulsion with speeds of up to 260 μm s(-1) (13 body lengths per second). Moreover, the polyelectrolyte multilayers assembled at high pH (pH>9.0) adsorb approximately 89% of dye molecules from water, owing to the electrostatic interaction between the positively charged polymers and the anionic dye molecules, and subsequently release them at neutral pH in a microfluidic device. The efficient propulsion coupled with the effective adsorption behavior of the catalytic shell motors in a microfluidic device results in accelerated separation of organics in water and thus holds considerable promise for water analysis.

  19. Chemically-modified cellulose paper as a microstructured catalytic reactor.

    PubMed

    Koga, Hirotaka; Kitaoka, Takuya; Isogai, Akira

    2015-01-15

    We discuss the successful use of chemically-modified cellulose paper as a microstructured catalytic reactor for the production of useful chemicals. The chemical modification of cellulose paper was achieved using a silane-coupling technique. Amine-modified paper was directly used as a base catalyst for the Knoevenagel condensation reaction. Methacrylate-modified paper was used for the immobilization of lipase and then in nonaqueous transesterification processes. These catalytic paper materials offer high reaction efficiencies and have excellent practical properties. We suggest that the paper-specific interconnected microstructure with pulp fiber networks provides fast mixing of the reactants and efficient transport of the reactants to the catalytically-active sites. This concept is expected to be a promising route to green and sustainable chemistry.

  20. Method for measuring recovery of catalytic elements from fuel cells

    SciTech Connect

    Shore, Lawrence; Matlin, Ramail

    2011-03-08

    A method is provided for measuring the concentration of a catalytic clement in a fuel cell powder. The method includes depositing on a porous substrate at least one layer of a powder mixture comprising the fuel cell powder and an internal standard material, ablating a sample of the powder mixture using a laser, and vaporizing the sample using an inductively coupled plasma. A normalized concentration of catalytic element in the sample is determined by quantifying the intensity of a first signal correlated to the amount of catalytic element in the sample, quantifying the intensity of a second signal correlated to the amount of internal standard material in the sample, and using a ratio of the first signal intensity to the second signal intensity to cancel out the effects of sample size.

  1. Catalytic Membrane Sensors

    SciTech Connect

    Boyle, T.J.; Brinker, C.J.; Gardner, T.J.; Hughes, R.C.; Sault, A.G.

    1998-12-01

    The proposed "catalytic membrane sensor" (CMS) was developed to generate a device which would selectively identify a specific reagent in a complex mixture of gases. This was to be accomplished by modifying an existing Hz sensor with a series of thin films. Through selectively sieving the desired component from a complex mixture and identifying it by decomposing it into Hz (and other by-products), a Hz sensor could then be used to detect the presence of the select component. The proposed "sandwich-type" modifications involved the deposition of a catalyst layered between two size selective sol-gel layers on a Pd/Ni resistive Hz sensor. The role of the catalyst was to convert organic materials to Hz and organic by-products. The role of the membraneo was to impart both chemical specificity by molecukir sieving of the analyte and converted product streams, as well as controlling access to the underlying Pd/Ni sensor. Ultimately, an array of these CMS elements encompassing different catalysts and membranes were to be developed which would enable improved selectivity and specificity from a compiex mixture of organic gases via pattern recognition methodologies. We have successfully generated a CMS device by a series of spin-coat deposited methods; however, it was determined that the high temperature required to activate the catalyst, destroys the sensor.

  2. Catalytic gasification of biomass

    NASA Astrophysics Data System (ADS)

    Robertus, R. J.; Mudge, L. K.; Sealock, L. J., Jr.; Mitchell, D. H.; Weber, S. L.

    1981-12-01

    Methane and methanol synthesis gas can be produced by steam gasification of biomass in the presence of appropriate catalysts. This concept is to use catalysts in a fluidized bed reactor which is heated indirectly. The objective is to determine the technical and economic feasibility of the concept. Technically the concept has been demonstrated on a 50 lb per hr scale. Potential advantages over conventional processes include: no oxygen plant is needed, little tar is produced so gas and water treatment are simplified, and yields and efficiencies are greater than obtained by conventional gasification. Economic studies for a plant processing 2000 T/per day dry wood show that the cost of methanol from wood by catalytic gasification is competitive with the current price of methanol. Similar studies show the cost of methane from wood is competitive with projected future costs of synthetic natural gas. When the plant capacity is decreased to 200 T per day dry wood, neither product is very attractive in today's market.

  3. Fuel-Rich Catalytic Combustion

    NASA Technical Reports Server (NTRS)

    Brabbs, Theodore A.; Olson, Sandra L.

    1987-01-01

    Two-stage combustion system reduces particulate emissions. Program on catalytic oxidation of iso-octane demonstrates feasibility of two-stage combustion system for reducing particulate emissions. With fuel-rich (fuel/air equivalence ratios of 4.8 to 7.8) catalytic-combustion preburner as first stage, combustion process free of soot at reactor-outlet temperatures of 1,200 K or less.

  4. Preconversion catalytic deoxygenation of phenolic functional groups

    SciTech Connect

    Kubiak, C.P.

    1991-01-01

    The deoxygenation of phenols by carbon monoxide mediated by Ir(triphos)(OAr) has provided us with a catalytic phenol deoxygenation pathway, through the elimination of CO{sub 2} and formation of a benzyne intermediate. Although the (Pt(triphos)(O-Ph- Me))PF{sub 6} system is not expected to be as efficient a catalyst as come of the other transition metals systems we are currently exploring, it will provide more information about the deoxygenation mechanism in these triphos complexes. This is due to the presence of the structurally sensitive {sup 31}P-{sup 195}Pt coupling constant and comparisons to the extensively studied Pt(dppe)(O-Ph){sub 2} systems.

  5. Catalytic combustion with steam injection

    NASA Astrophysics Data System (ADS)

    Anderson, D. N.; Tacina, R. R.

    The effects of steam injection on (1) catalytic combustion performance, and (2) the tendency of residual fuel to burn in the premixing duct upstream of the catalytic reactor were determined. A petroleum residual, no. 2 diesel, and a blend of middle and heavy distillate coal derived fuels were tested. Fuel and steam were injected together into the preheated airflow entering a 12 cm diameter catalytic combustion test section. The inlet air velocity and pressure were constant at 10 m/s and 600 kPa, respectively. Steam flow rates were varied from 24 percent to 52 percent of the air flow rate. The resulting steam air mixture temperatures varied from 630 to 740 K. Combustion temperatures were in the range of 1200 to 1400 K. The steam had little effect on combustion efficiency or emissions. It was concluded that the steam acts as a diluent which has no adverse effect on catalytic combustion performance for no. 2 diesel and coal derived liquid fuels. Tests with the residual fuel showed that upstream burning could be eliminated with steam injection rates greater than 30 percent of the air flow rate, but inlet mixture temperatures were too low to permit stable catalytic combustion of this fuel.

  6. Catalytic combustion with steam injection

    NASA Technical Reports Server (NTRS)

    Anderson, D. N.; Tacina, R. R.

    1982-01-01

    The effects of steam injection on (1) catalytic combustion performance, and (2) the tendency of residual fuel to burn in the premixing duct upstream of the catalytic reactor were determined. A petroleum residual, no. 2 diesel, and a blend of middle and heavy distillate coal derived fuels were tested. Fuel and steam were injected together into the preheated airflow entering a 12 cm diameter catalytic combustion test section. The inlet air velocity and pressure were constant at 10 m/s and 600 kPa, respectively. Steam flow rates were varied from 24 percent to 52 percent of the air flow rate. The resulting steam air mixture temperatures varied from 630 to 740 K. Combustion temperatures were in the range of 1200 to 1400 K. The steam had little effect on combustion efficiency or emissions. It was concluded that the steam acts as a diluent which has no adverse effect on catalytic combustion performance for no. 2 diesel and coal derived liquid fuels. Tests with the residual fuel showed that upstream burning could be eliminated with steam injection rates greater than 30 percent of the air flow rate, but inlet mixture temperatures were too low to permit stable catalytic combustion of this fuel.

  7. Two-stage, close coupled catalytic liquefaction of coal

    SciTech Connect

    Comolli, A.G.; Johanson, E.S.; Panvelker, S.V.; Popper, G.A.; Smith, T.O.

    1990-09-01

    During the first quarter of 1990, work was carried out in the microautoclave, microreactor, and Bench-Scale units. An economics analysis on sub-bituminous coal processing at two space velocities was also completed. Several supported catalysts and a sample of iron oxide were screened in the microautoclave unsulfided and sulfided with DMDS and TNPS. A second shipment of Black Thunder coal from Wilsonville, oil agglomerated cleaned Illinois {number sign}6 coal from Homer City, OTISCA cleaned coal a New Mexico coal were evaluated for relative conversions with and without catalyst. Results of Bench-Scale developments with cleaned, oil agglomerated, Illinois {number sign}6 coal from Homer City(CC-6), Dispersed Catalyst/Supported Catalyst Two-Stage and reversed sequential operation (CC-7), on Black Thunder Coal (CC-7), and preliminary observations on OTISCA cleaned coal are presented. The oil agglomerated cleaned coal gave higher conversion and distillate production than the OTISCA cleaned coal. The Dispersed/Supported Two-Stage operation yielded higher gas production than the reverse sequence but also showed the higher coal conversion. Economic analysis of sub-bituminous coal processing at two space velocities showed a 3% higher return on investment with a 50% increase in space velocity. 13 tabs.

  8. Studies of coupled chemical and catalytic coal conversion methods

    SciTech Connect

    Stock, L.M.

    1991-01-01

    When an arene is coordinated to Cr(CO){sub 3}, profound changes in its reactivity occur. Ring and benzylic hydrogen atoms exhibit enhanced acidity, and typical arene reactions such as electrophilic aromatic substitutions are quenched. In contrast, the ring carbon atoms are activated toward attack by nucleophiles. These changes in reactivity are manifestations of the forceful electron withdrawing nature of the Cr(CO){sub 3} component, and of the ability of this group to stabilize charged intermediates. In addition, arenechromium tricarbonyl complexes have been proven to be good catalysts in the hydrogenation of dienes. While most simple complexes such as toluenechromium tricarbonyl require the use of high temperatures and dihydrogen pressures, arenechromium tricarbonyl complexes with napthalene, anthracene, and phenanthrene show remarkable activity under extremely mild conditions. An investigation has been under way in which the chemistry of coal arene-Cr(CO){sub 3} complexes have been studied. 4 figs.

  9. Gold-catalyzed homogeneous oxidative cross-coupling reactions.

    PubMed

    Zhang, Guozhu; Peng, Yu; Cui, Li; Zhang, Liming

    2009-01-01

    Oxidizing gold? A gold(I)/gold(III) catalytic cycle is essential for the first oxidative cross-coupling reaction in gold catalysis. By using Selectfluor for gold(I) oxidation, this chemistry reveals the synthetic potential of incorporating gold(I)/gold(III) catalytic cycles into contemporary gold chemistry and promises a new area of gold research by merging powerful gold catalysis and oxidative metal-catalyzed cross-coupling reactions.

  10. Catalytic distillation water recovery subsystem

    NASA Technical Reports Server (NTRS)

    Budininkas, P.; Rasouli, F.

    1985-01-01

    An integrated engineering breadboard subsystem for the recovery of potable water from untreated urine based on the vapor phase catalytic ammonia removal was designed, fabricated and tested. Unlike other evaporative methods, this process catalytically oxidizes ammonia and volatile hydrocarbons vaporizing with water to innocuous products; therefore, no pretreatment of urine is required. Since the subsystem is fabricated from commercially available components, its volume, weight and power requirements are not optimized; however, it is suitable for zero-g operation. The testing program consists of parametric tests, one month of daily tests and a continuous test of 168 hours duration. The recovered water is clear, odorless, low in ammonia and organic carbon, and requires only an adjustment of its pH to meet potable water standards. The obtained data indicate that the vapor phase catalytic ammonia removal process, if further developed, would also be competitive with other water recovery systems in weight, volume and power requirements.

  11. Catalytic Cracking of Gaseous Heavy Hydrocarbons by Ceramic Filters

    SciTech Connect

    Heidenreich, S.; Nacken, M.; Walch, A.; Chudzinski, S.

    2002-09-19

    The use of syngas from waste or biomass gasification to generate electricity is a way which is attracting increasing attention especially with regard to the demands of regenerable energy consumption and to the reduction of waste disposal. In order to feed the syngas to a gas motor or a gas turbine the gas has to be cleaned. In future also the coupling of biomass gasification with a fuel cell will be applied, which needs a very efficient gas cleaning. The decomposition of tars and the removal of particles from the gas are the key issues of gas cleaning. Up to now these two steps are performed in two separate units. Normally, the tars are decomposed in catalytic beds or honeycomb structures. The catalytic decomposition is achieved at temperatures between 750 C and 900 C depending on the catalyst used. Particles are removed by filtration of the hot gas. Filtration at high temperatures and with high efficiencies is possible when using ceramic filter elements. Ceramic hot gas filters are well established in advanced coal gasification, such as the integrated gasification combined cycle process, as well as in waste and biomass gasification and pyrolysis processes. Since the catalytic reaction requires high temperatures the gas has to be reheated after the particles are removed in the filter or the hot unfiltered gas has to flow through the catalytic unit. If the gas is filtered first, reheating of the gas stream is an additional cost factor. Furthermore, pipes downstream of the filter can be plugged, if the temperature of the gas falls below the condensation temperature of the heavy hydrocarbons. Using the second way of hot unfiltered gas flows through the catalytic unit, there is the problem of deactivation of the catalyst by deposition of dust at higher dust concentrations. At worst the catalytic unit can be plugged by dust deposition.

  12. Catalytic Enantioselective Carboannulation with Allylsilanes

    PubMed Central

    Ball-Jones, Nicolas R.; Badillo, Joseph J.; Tran, Ngon T.; Franz, Annaliese K.

    2015-01-01

    The first catalytic asymmetric carboannulation with allylsilanes is presented. The enantioselective [3+2] annulation is catalyzed using a Sc(III)-indapybox complex with tetrakis-[3,5-bis(trifluoromethyl)phenyl]-borate (BArF) to enhance catalytic activity and control stereoselectivity. Functionalized cyclopentanes containing a quaternary carbon are derived from alkylidene oxindole, coumarin, and malonate substrates with high stereoselectivity. The enantioselective 1,4-conjugate addition and enantioselective lactone formation (via trapping of the β-silyl carbocation) is also described. PMID:25045133

  13. Catalytic enantioselective carboannulation with allylsilanes.

    PubMed

    Ball-Jones, Nicolas R; Badillo, Joseph J; Tran, Ngon T; Franz, Annaliese K

    2014-09-01

    The first catalytic asymmetric carboannulation with allylsilanes is presented. The enantioselective [3+2] annulation is catalyzed using a scandium(III)/indapybox complex with tetrakis-[3,5-bis(trifluoromethyl)phenyl]-borate (BArF) to enhance catalytic activity and control stereoselectivity. Functionalized cyclopentanes containing a quaternary carbon center are derived from alkylidene oxindole, coumarin, and malonate substrates with high stereoselectivity. The enantioselective 1,4-conjugate addition and enantioselective lactone formation (by trapping of the β-silyl carbocation) is also described. PMID:25045133

  14. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

    The decomposition of Fomblin Z25, a commercial perfluoropolyalkylether liquid lubricant, was studied using the Penn State Micro-oxidation Test, and a thermal gravimetric/differential scanning calorimetry unit. The micro-oxidation test was conducted using 440C stainless steel and pure iron metal catalyst specimens, whereas the thermal gravimetric/differential scanning calorimetry tests were conducted using catalytic alumina pellets. Analysis of the thermal data, high pressure liquid chromatography data, and x-ray photoelectron spectroscopy data support evidence that there are two different decomposition mechanisms for Fomblin Z25, and that reductive sites on the catalytic surfaces are responsible for the decomposition of Fomblin Z25.

  15. Controlling structure and porosity in catalytic nanoparticle superlattices with DNA.

    PubMed

    Auyeung, Evelyn; Morris, William; Mondloch, Joseph E; Hupp, Joseph T; Farha, Omar K; Mirkin, Chad A

    2015-02-01

    Herein, we describe a strategy for converting catalytically inactive, highly crystalline nanoparticle superlattices embedded in silica into catalytically active, porous structures through superlattice assembly and calcination. First, a body-centered cubic (bcc) superlattice is synthesized through the assembly of two sets of 5 nm gold nanoparticles chemically modified with DNA bearing complementary sticky end sequences. These superlattices are embedded in silica and calcined at 350 °C to provide access to the catalytic nanoparticle surface sites. The calcined superlattice maintains its bcc ordering and has a surface area of 210 m(2)/g. The loading of catalytically active nanoparticles within the superlattice was determined by inductively coupled plasma mass spectrometry, which revealed that the calcined superlattice contained approximately 10% Au by weight. We subsequently investigate the ability of supported Au nanoparticle superlattices to catalyze alcohol oxidation. In addition to demonstrating that calcined superlattices are effective catalysts for alcohol oxidation, electron microscopy reveals preservation of the crystalline structure of the bcc superlattice following calcination and catalysis. Unlike many bulk nanoparticle catalysts, which are difficult to characterize and susceptible to aggregation, nanoparticle superlattices synthesized using DNA interactions offer an attractive bottom-up route to structurally defined heterogeneous catalysts, where one has the potential to independently control nanoparticle size, nanoparticle compositions, and interparticle spacings.

  16. Catalytic two-stage coal hydrogenation and hydroconversion process

    DOEpatents

    MacArthur, James B.; McLean, Joseph B.; Comolli, Alfred G.

    1989-01-01

    A process for two-stage catalytic hydrogenation and liquefaction of coal to produce increased yields of low-boiling hydrocarbon liquid and gas products. In the process, the particulate coal is slurried with a process-derived liquid solvent and fed at temperature below about 650.degree. F. into a first stage catalytic reaction zone operated at conditions which promote controlled rate liquefaction of the coal, while simultaneously hydrogenating the hydrocarbon recycle oils at conditions favoring hydrogenation reactions. The first stage reactor is maintained at 650.degree.-800.degree. F. temperature, 1000-4000 psig hydrogen partial pressure, and 10-60 lb coal/hr/ft.sup.3 reactor space velocity. The partially hydrogenated material from the first stage reaction zone is passed directly to the close-coupled second stage catalytic reaction zone maintained at a temperature at least about 25.degree. F. higher than for the first stage reactor and within a range of 750.degree.-875.degree. F. temperature for further hydrogenation and thermal hydroconversion reactions. By this process, the coal feed is successively catalytically hydrogenated and hydroconverted at selected conditions, which results in significantly increased yields of desirable low-boiling hydrocarbon liquid products and minimal production of undesirable residuum and unconverted coal and hydrocarbon gases, with use of less energy to obtain the low molecular weight products, while catalyst life is substantially increased.

  17. Catalytic oxidation of waste materials

    NASA Technical Reports Server (NTRS)

    Jagow, R. B.

    1977-01-01

    Aqueous stream of human waste is mixed with soluble ruthenium salts and is introduced into reactor at temperature where ruthenium black catalyst forms on internal surfaces of reactor. This provides catalytically active surface to convert oxidizable wastes into breakdown products such as water and carbon dioxide.

  18. Heterogeneous catalytic alcoholysis of benzonitrile

    SciTech Connect

    Kagarlitskii, A.D.; Dmumakaev, K.Kh.; Bekova, N.S.

    1986-04-01

    The authors investigate the possibility of the direct heterogeneous catalytic synthesis of ethylbenzoate from benzonitrile. The catalysts tested were oxides of aluminium, titanium, and vanadium. The main conversion product detected chromatographically was ethylbenzoate; benzaldehyde, benzamide, and benzanilide were also identified. Aluminium oxide was found to be the most effective catalyst.

  19. High temperature catalytic membrane reactors

    SciTech Connect

    Not Available

    1990-03-01

    Current state-of-the-art inorganic oxide membranes offer the potential of being modified to yield catalytic properties. The resulting modules may be configured to simultaneously induce catalytic reactions with product concentration and separation in a single processing step. Processes utilizing such catalytically active membrane reactors have the potential for dramatically increasing yield reactions which are currently limited by either thermodynamic equilibria, product inhibition, or kinetic selectivity. Examples of commercial interest include hydrogenation, dehydrogenation, partial and selective oxidation, hydrations, hydrocarbon cracking, olefin metathesis, hydroformylation, and olefin polymerization. A large portion of the most significant reactions fall into the category of high temperature, gas phase chemical and petrochemical processes. Microporous oxide membranes are well suited for these applications. A program is proposed to investigate selected model reactions of commercial interest (i.e. dehydrogenation of ethylbenzene to styrene and dehydrogenation of butane to butadiene) using a high temperature catalytic membrane reactor. Membranes will be developed, reaction dynamics characterized, and production processes developed, culminating in laboratory-scale demonstration of technical and economic feasibility. As a result, the anticipated increased yield per reactor pass economic incentives are envisioned. First, a large decrease in the temperature required to obtain high yield should be possible because of the reduced driving force requirement. Significantly higher conversion per pass implies a reduced recycle ratio, as well as reduced reactor size. Both factors result in reduced capital costs, as well as savings in cost of reactants and energy.

  20. Simple, chemoselective, catalytic olefin isomerization.

    PubMed

    Crossley, Steven W M; Barabé, Francis; Shenvi, Ryan A

    2014-12-01

    Catalytic amounts of Co(Sal(tBu,tBu))Cl and organosilane irreversibly isomerize terminal alkenes by one position. The same catalysts effect cycloisomerization of dienes and retrocycloisomerization of strained rings. Strong Lewis bases like amines and imidazoles, and labile functionalities like epoxides, are tolerated.

  1. Social Entrepreneurs and Catalytic Change.

    ERIC Educational Resources Information Center

    Waddock, Sandra A.; Post, James E.

    1991-01-01

    Social entrepreneurs are private citizens who play critical roles in bringing about catalytic changes in the public sector agenda and the perception of social issues. Factors that make their projects--such as the Partnership for a Drug-Free America and Earth Day--successful include problem complexity, credibility, and a commitment to a collective…

  2. Process for Coating Substrates with Catalytic Materials

    NASA Technical Reports Server (NTRS)

    Klelin, Ric J. (Inventor); Upchurch, Billy T. (Inventor); Schryer, David R. (Inventor)

    2004-01-01

    A process for forming catalysts by coating substrates with two or more catalytic components, which comprises the following sequence of steps. First, the substrate is infused with an adequate amount of solution having a starting material comprising a catalytic component precursor, wherein the thermal decomposition product of the catalytic component precursor is a catalytic component. Second, the excess of the solution is removed from the substrate. thereby leaving a coating of the catalytic component precursor on the surface of the substrate. Third, the coating of the catalytic component precursor is converted to the catalytic component by thermal decomposition. Finally, the coated substance is etched to increase the surface area. The list three steps are then repeated for at least a second catalytic component. This process is ideally suited for application in producing efficient low temperature oxidation catalysts.

  3. Polymer and Membrane Design for Low Temperature Catalytic Reactions.

    PubMed

    Villalobos, Luis Francisco; Xie, Yihui; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

    2016-04-01

    Catalytically active asymmetric membranes have been developed with high loadings of palladium nanoparticles located solely in the membrane's ultrathin skin layer. The manufacturing of these membranes requires polymers with functional groups, which can form insoluble complexes with palladium ions. Three polymers have been synthesized for this purpose and a complexation/nonsolvent induced phase separation followed by a palladium reduction step is carried out to prepare such membranes. Parameters to optimize the skin layer thickness and porosity, the palladium loading in this layer, and the palladium nanoparticles size are determined. The catalytic activity of the membranes is verified with the reduction of a nitro-compound and with a liquid phase Suzuki-Miyaura coupling reaction. Very low reaction times are observed.

  4. Stereoselective borylative ketone-diene coupling.

    PubMed

    Cho, Hee Yeon; Yu, Zhiyong; Morken, James P

    2011-10-01

    In the presence of catalytic Ni(cod)(2) and P(t-Bu)(3), ketones, dienes, and B(2)(pin)(2) undergo a stereoselective multicomponent coupling reaction. Upon oxidation, the reaction furnishes 1,3-diols as the major reaction product.

  5. Vapor Phase Catalytic Ammonia Reduction

    NASA Technical Reports Server (NTRS)

    Flynn, Michael T.; Harper, Lynn D. (Technical Monitor)

    1994-01-01

    This paper discusses the development of a Vapor Phase Catalytic Ammonia Reduction (VPCAR) teststand and the results of an experimental program designed to evaluate the potential of the technology as a water purification process. In the experimental program the technology is evaluated based upon product water purity, water recovery rate, and power consumption. The experimental work demonstrates that the technology produces high purity product water and attains high water recovery rates at a relatively high specific power consumption. The experimental program was conducted in 3 phases. In phase I an Igepon(TM) soap and water mixture was used to evaluate the performance of an innovative Wiped-Film Rotating-Disk evaporator and associated demister. In phase II a phenol-water solution was used to evaluate the performance of the high temperature catalytic oxidation reactor. In phase III a urine analog was used to evaluate the performance of the combined distillation/oxidation functions of the processor.

  6. Catalytic combustion of residual fuels

    NASA Technical Reports Server (NTRS)

    Bulzan, D. L.; Tacina, R. R.

    1981-01-01

    A noble metal catalytic reactor was tested using two grades of petroleum derived residual fuels at specified inlet air temperatures, pressures, and reference velocities. Combustion efficiencies greater than 99.5 percent were obtained. Steady state operation of the catalytic reactor required inlet air temperatures of at least 800 K. At lower inlet air temperatures, upstream burning in the premixing zone occurred which was probably caused by fuel deposition and accumulation on the premixing zone walls. Increasing the inlet air temperature prevented this occurrence. Both residual fuels contained about 0.5 percent nitrogen by weight. NO sub x emissions ranged from 50 to 110 ppm by volume at 15 percent excess O2. Conversion of fuel-bound nitrogen to NO sub x ranged from 25 to 50 percent.

  7. Catalytic asymmetric alkylation of acylsilanes.

    PubMed

    Rong, Jiawei; Oost, Rik; Desmarchelier, Alaric; Minnaard, Adriaan J; Harutyunyan, Syuzanna R

    2015-03-01

    The highly enantioselective addition of Grignard reagents to acylsilanes is catalyzed by copper diphosphine complexes. This transformation affords α-silylated tertiary alcohols in up to 97% yield and 98:2 enantiomeric ratio. The competing Meerwein-Ponndorf-Verley reduction is suppressed by the use of a mixture of Lewis acid additives. The chiral catalyst can be recovered as a copper complex and used repeatedly without any loss of catalytic activity. PMID:25403641

  8. Thermodynamics of catalytic nanoparticle morphology

    NASA Astrophysics Data System (ADS)

    Zwolak, Michael; Sharma, Renu; Lin, Pin Ann

    Metallic nanoparticles are an important class of industrial catalysts. The variability of their properties and the environment in which they act, from their chemical nature & surface modification to their dispersion and support, allows their performance to be optimized for many chemical processes useful in, e.g., energy applications and other areas. Their large surface area to volume ratio, as well as varying sizes and faceting, in particular, makes them an efficient source for catalytically active sites. These characteristics of nanoparticles - i.e., their morphology - can often display intriguing behavior as a catalytic process progresses. We develop a thermodynamic model of nanoparticle morphology, one that captures the competition of surface energy with other interactions, to predict structural changes during catalytic processes. Comparing the model to environmental transmission electron microscope images of nickel nanoparticles during carbon nanotube (and other product) growth demonstrates that nickel deformation in response to the nanotube growth is due to a favorable interaction with carbon. Moreover, this deformation is halted due to insufficient volume of the particles. We will discuss the factors that influence morphology and also how the model can be used to extract interaction strengths from experimental observations.

  9. Oxo-rhenium catalyzed reductive coupling and deoxygenation of alcohols.

    PubMed

    Kasner, Gabrielle R; Boucher-Jacobs, Camille; Michael McClain, J; Nicholas, Kenneth M

    2016-06-01

    Representative benzylic, allylic and α-keto alcohols are deoxygenated to alkanes and/or reductively coupled to alkane dimers by reaction with PPh3 catalyzed by (PPh3)2ReIO2 (1). The newly discovered catalytic reductive coupling reaction is a rare C-C bond-forming transformation of alcohols. PMID:27174412

  10. Surface oxygen triggered size change of palladium nano-crystals impedes catalytic efficacy.

    PubMed

    Zou, Jianli; Stewart, Scott G; Raston, Colin L; Iyer, K Swaminathan

    2011-02-14

    Palladium nano-crystals increase in size during the initial recycling in Heck cross coupling reactions. We demonstrate that oxygen adsorbed on the surface of palladium nano-crystals plays a pivotal role in driving the ripening. This in turn is associated with a loss in catalytic activity.

  11. Catalytic synthesis of silicon carbide preceramic polymers: Polycarbosilanes

    SciTech Connect

    Berry, D.H.

    1991-11-01

    Polycarbosilanes are the most successful and widely studied class of polymer precursors for silicon carbide, but traditional methods for thier synthesis are inefficient and nonselective. This project is focused on developing transition metal catalysts for the synthesis of polycarbosilanes and other perceramic polymers. In recent work we have developed the first homogeneous transition metal catalysts for the dehydrogenative coupling of simple alkyl silanes to oligomeric and polymeric carbosilanes, H-(SiR{sub 2}CR{prime}{sub 2}){sub n}-SiR{sub 3}. Future work will help elucidate the mechanism of the catalytic process, explore the use of hydrogen acceptors as reaction accelerators, and develop new and more active catalysts.

  12. Synthesis of (+)-Discodermolide by Catalytic Stereoselective Borylation Reactions**

    PubMed Central

    Yu, Zhiyong; Ely, Robert J.

    2014-01-01

    The marine natural product (+)-discodermolide was first isolated in 1990 and, to this day, remains a compelling synthesis target. Not only does the compound possess fascinating biological activity, but it also presents an opportunity to test current methods for chemical synthesis and provides a forum for the inspiration of new reaction development. In this manuscript, we present a synthesis of discodermolide that employs a previously undisclosed stereoselective catalytic diene hydroboration and also establishes a strategy for chiral enolate alkylation. In addition, this synthesis of discodermolide provides the first examples of diene 1,4-diboration and borylative diene-aldehyde couplings in complex molecule synthesis. PMID:25045037

  13. Synthesis of (+)-discodermolide by catalytic stereoselective borylation reactions.

    PubMed

    Yu, Zhiyong; Ely, Robert J; Morken, James P

    2014-09-01

    The marine natural product (+)-discodermolide was first isolated in 1990 and, to this day, remains a compelling synthesis target. Not only does the compound possess fascinating biological activity, but it also presents an opportunity to test current methods for chemical synthesis and provides an inspiration for new reaction development. A new synthesis of discodermolide employs a previously undisclosed stereoselective catalytic diene hydroboration and also establishes a strategy for the alkylation of chiral enolates. Furthermore, this synthesis of discodermolide provides the first examples of the asymmetric 1,4-diboration of dienes and borylative diene-aldehyde couplings in complex-molecule synthesis.

  14. Catalytic efficiency of enzymes: a theoretical analysis.

    PubMed

    Hammes-Schiffer, Sharon

    2013-03-26

    This brief review analyzes the underlying physical principles of enzyme catalysis, with an emphasis on the role of equilibrium enzyme motions and conformational sampling. The concepts are developed in the context of three representative systems, namely, dihydrofolate reductase, ketosteroid isomerase, and soybean lipoxygenase. All of these reactions involve hydrogen transfer, but many of the concepts discussed are more generally applicable. The factors that are analyzed in this review include hydrogen tunneling, proton donor-acceptor motion, hydrogen bonding, pKa shifting, electrostatics, preorganization, reorganization, and conformational motions. The rate constant for the chemical step is determined primarily by the free energy barrier, which is related to the probability of sampling configurations conducive to the chemical reaction. According to this perspective, stochastic thermal motions lead to equilibrium conformational changes in the enzyme and ligands that result in configurations favorable for the breaking and forming of chemical bonds. For proton, hydride, and proton-coupled electron transfer reactions, typically the donor and acceptor become closer to facilitate the transfer. The impact of mutations on the catalytic rate constants can be explained in terms of the factors enumerated above. In particular, distal mutations can alter the conformational motions of the enzyme and therefore the probability of sampling configurations conducive to the chemical reaction. Methods such as vibrational Stark spectroscopy, in which environmentally sensitive probes are introduced site-specifically into the enzyme, provide further insight into these aspects of enzyme catalysis through a combination of experiments and theoretical calculations.

  15. Modeling a Transient Catalytic Combustor

    NASA Technical Reports Server (NTRS)

    Tien, J. S.

    1985-01-01

    Transient model of monolith catalytic combustor presented in report done under NASA/DOE contract. Model assumes quasi-steady gas phase and thermally "thin" solid. In gas-phase treatment, several quasi-global chemical reactions assumed capable of describing CO and unburnt hydrocarbon emissions in fuel-lean operations. In steady-state computation presented, influence of selected operating and design parameters on minimum combustor length studied. When fast transient responses required, both steady and unsteady studies made to achieve meaningful compromise in design.

  16. Molecular catalytic coal liquid conversion

    SciTech Connect

    Stock, L.M.; Yang, Shiyong

    1995-12-31

    This research, which is relevant to the development of new catalytic systems for the improvement of the quality of coal liquids by the addition of dihydrogen, is divided into two tasks. Task 1 centers on the activation of dihydrogen by molecular basic reagents such as hydroxide ion to convert it into a reactive adduct (OH{center_dot}H{sub 2}){sup {minus}} that can reduce organic molecules. Such species should be robust withstanding severe conditions and chemical poisons. Task 2 is focused on an entirely different approach that exploits molecular catalysts, derived from organometallic compounds that are capable of reducing monocyclic aromatic compounds under very mild conditions. Accomplishments and conclusions are discussed.

  17. Catalytic membranes for fuel cells

    DOEpatents

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2011-04-19

    A fuel cell of the present invention comprises a cathode and an anode, one or both of the anode and the cathode including a catalyst comprising a bundle of longitudinally aligned graphitic carbon nanotubes including a catalytically active transition metal incorporated longitudinally and atomically distributed throughout the graphitic carbon walls of said nanotubes. The nanotubes also include nitrogen atoms and/or ions chemically bonded to the graphitic carbon and to the transition metal. Preferably, the transition metal comprises at least one metal selected from the group consisting of Fe, Co, Ni, Mn, and Cr.

  18. Helix coupling

    DOEpatents

    Ginell, W.S.

    1989-04-25

    A coupling for connecting helix members in series, which consists of a pair of U-shaped elements, one of which is attached to each helix end with the "U" sections of the elements interlocked. The coupling is particularly beneficial for interconnecting helical Nitinol elements utilized in thermal actuators or engines. Each coupling half is attached to the associated helix at two points, thereby providing axial load while being easily removed from the helix, and reusable.

  19. Helix coupling

    DOEpatents

    Ginell, W.S.

    1982-03-17

    A coupling for connecting helix members in series, which consists of a pair of U-shaped elements, one of which is attached to each helix end with the U sections of the elements interlocked. The coupling is particularly beneficial for interconnecting helical Nitinol elements utilized in thermal actuators or engines. Each coupling half is attached to the associated helix at two points, thereby providing axial load while being easily removed from the helix, and reusable.

  20. Computational Introduction of Catalytic Activity into Proteins.

    PubMed

    Bertolani, Steve J; Carlin, Dylan Alexander; Siegel, Justin B

    2016-01-01

    Recently, there have been several successful cases of introducing catalytic activity into proteins. One method that has been used successfully to achieve this is the theozyme placement and enzyme design algorithms implemented in Rosetta Molecular Modeling Suite. Here, we illustrate how to use this software to recapitulate the placement of catalytic residues and ligand into a protein using a theozyme, protein scaffold, and catalytic constraints as input. PMID:27094294

  1. Catalytic Polymer Multilayer Shell Motors for Separation of Organics.

    PubMed

    Lin, Zhihua; Wu, Zhiguang; Lin, Xiankun; He, Qiang

    2016-01-26

    A catalytic polymer multilayer shell motor has been developed, which effects fast motion-based separation of charged organics in water. The shell motors are fabricated by sputtering platinum onto the exposed surface of silica templates embedded in Parafilm, followed by layer-by-layer assembly of polyelectrolyte multilayers to the templates. The catalytic shell motors display high bubble propulsion with speeds of up to 260 μm s(-1) (13 body lengths per second). Moreover, the polyelectrolyte multilayers assembled at high pH (pH>9.0) adsorb approximately 89% of dye molecules from water, owing to the electrostatic interaction between the positively charged polymers and the anionic dye molecules, and subsequently release them at neutral pH in a microfluidic device. The efficient propulsion coupled with the effective adsorption behavior of the catalytic shell motors in a microfluidic device results in accelerated separation of organics in water and thus holds considerable promise for water analysis. PMID:26632275

  2. Catalytic oxidizers and Title V requirements

    SciTech Connect

    Uberoi, M.; Rach, S.E.

    1999-07-01

    Catalytic oxidizers have been used to reduce VOC emissions from various industries including printing, chemical, paint, coatings, etc. A catalytic oxidizer uses a catalyst to reduce the operating temperature for combustion to approximately 600 F, which is substantially lower than thermal oxidation unit. Title V requirements have renewed the debate on the best methods to assure compliance of catalytic oxidizers, with some suggesting the need for continuous emission monitoring equipment. This paper will discuss the various aspects of catalytic oxidation and consider options such as monitoring inlet/outlet temperatures, delta T across the catalyst, periodic laboratory testing of catalyst samples, and preventive maintenance procedures as means of assuring continuous compliance.

  3. Catalytic conversion of light alkanes

    SciTech Connect

    Lyons, J.E.

    1992-06-30

    The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

  4. Metal hybrid nanoparticles for catalytic organic and photochemical transformations.

    PubMed

    Song, Hyunjoon

    2015-03-17

    In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly have multiple components including active metal nanoparticles and metal oxide supports. On the other hand, as nanochemistry has rapidly been developed and been applied to various fields, many researchers have begun to discuss the impact of nanochemistry on heterogeneous catalysis. Metal hybrid nanoparticles bearing multiple components are structurally very close to the actual catalysts, and their uniform and controllable morphology is suitable for investigating the relationship between the structure and the catalytic properties in detail. In this Account, we introduce four typical structures of metal hybrid nanoparticles that can be used to conduct catalytic organic and photochemical reactions. Metal@silica (or metal oxide) yolk-shell nanoparticles, in which metal cores exist in internal voids surrounded by thin silica (or metal oxide) shells, exhibited extremely high thermal and chemical stability due to the geometrical protection of the silica layers against the metal cores. The morphology of the metal cores and the pore density of the hollow shells were precisely adjusted to optimize the reaction activity and diffusion rates of the reactants. Metal@metal oxide core-shell nanoparticles and inverted structures, where the cores supported the shells serving an active surface, exhibited high activity with no diffusion barriers for the reactants and products. These nanostructures were used as effective catalysts for various organic and gas-phase reactions, including hydrogen transfer, Suzuki coupling, and steam methane reforming. In contrast to the yolk- and core-shell structures, an asymmetric arrangement of distinct domains generated acentric dumbbells and tipped rods. A large domain of each component added multiple

  5. Catalytic synthesis of silicon carbide preceramic polymers: Polycarbosilanes

    SciTech Connect

    Berry, D.H.

    1992-10-01

    Polycarbosilanes are the most successful and widely studied class of polymer precursors for silicon carbide, but traditional methods for their synthesis are inefficient and nonselective. This project is focused on developing transition metal catalysts for the synthesis of polycarbosilanes and other preceramic polymers. In recent work we have developed the first homogeneous transition metal catalysts for the dehydrogenative coupling of simple alkyl silanes to oligomeric and polymeric carbosilanes, H-(SiR[sub 2]CR[prime][sub 2])n-SiR[sub 3]. The coupling of alkylgermanes, however, yields the corresponding oligomeric poly(germanes) (Ge-Ge). Future work will help elucidate the mechanisms of these catalytic process, explore the use of hydrogen acceptors as reaction accelerators, and develop new and more active catalysts.

  6. A Single Aspartate Coordinates Two Catalytic Steps in Hedgehog Autoprocessing.

    PubMed

    Xie, Jian; Owen, Timothy; Xia, Ke; Callahan, Brian; Wang, Chunyu

    2016-08-31

    Hedgehog (Hh) signaling is driven by the cholesterol-modified Hh ligand, generated by autoprocessing of Hh precursor protein. Two steps in Hh autoprocessing, N-S acyl shift and transesterification, must be coupled for efficient Hh cholesteroylation and downstream signal transduction. In the present study, we show that a conserved aspartate residue, D46 of the Hh autoprocessing domain, coordinates these two catalytic steps. Mutagenesis demonstrated that D46 suppresses non-native Hh precursor autoprocessing and is indispensable for transesterification with cholesterol. NMR measurements indicated that D46 has a pKa of 5.6, ∼2 units above the expected pKa of aspartate, due to a hydrogen-bond between protonated D46 and a catalytic cysteine residue. However, the deprotonated form of D46 side chain is also essential, because a D46N mutation cannot mediate cholesteroylation. On the basis of these data, we propose that the proton shuttling of D46 side chain mechanistically couples the two steps of Hh cholesteroylation. PMID:27529645

  7. Diesel engine catalytic combustor system. [aircraft engines

    NASA Technical Reports Server (NTRS)

    Ream, L. W. (Inventor)

    1984-01-01

    A low compression turbocharged diesel engine is provided in which the turbocharger can be operated independently of the engine to power auxiliary equipment. Fuel and air are burned in a catalytic combustor to drive the turbine wheel of turbine section which is initially caused to rotate by starter motor. By opening a flapper value, compressed air from the blower section is directed to catalytic combustor when it is heated and expanded, serving to drive the turbine wheel and also to heat the catalytic element. To start, engine valve is closed, combustion is terminated in catalytic combustor, and the valve is then opened to utilize air from the blower for the air driven motor. When the engine starts, the constituents in its exhaust gas react in the catalytic element and the heat generated provides additional energy for the turbine section.

  8. Catalytic ignition of hydrogen and oxygen propellants

    NASA Technical Reports Server (NTRS)

    Zurawski, Robert L.; Green, James M.

    1988-01-01

    An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalysts are presented.

  9. Method of fabricating a catalytic structure

    DOEpatents

    Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.

    2009-09-22

    A precursor to a catalytic structure comprising zinc oxide and copper oxide. The zinc oxide has a sheet-like morphology or a spherical morphology and the copper oxide comprises particles of copper oxide. The copper oxide is reduced to copper, producing the catalytic structure. The catalytic structure is fabricated by a hydrothermal process. A reaction mixture comprising a zinc salt, a copper salt, a hydroxyl ion source, and a structure-directing agent is formed. The reaction mixture is heated under confined volume conditions to produce the precursor. The copper oxide in the precursor is reduced to copper. A method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure.

  10. Catalytic ignition of hydrogen and oxygen propellants

    NASA Technical Reports Server (NTRS)

    Zurawski, Robert L.; Green, James M.

    1988-01-01

    An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalyst are presented.

  11. Catalytic ignition of hydrogen/oxygen

    NASA Technical Reports Server (NTRS)

    Green, James M.; Zurawski, Robert L.

    1988-01-01

    An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen. Shell 405 granular catalyst and a unique monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant inlet temperature, and back pressure were varied parametrically in testing to determine the operational limits of a catalytic igniter. The test results showed that the gaseous hydrogen/oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. The results of the experimental program and the established operational limits for a catalytic igniter using both the granular and monolithic catalysts are presented. The capabilities of a facility constructed to conduct the igniter testing and the advantages of a catalytic igniter over other ignition systems for gaseous hydrogen and oxygen are also discussed.

  12. Silver nanocluster catalytic microreactors for water purification

    NASA Astrophysics Data System (ADS)

    Da Silva, B.; Habibi, M.; Ognier, S.; Schelcher, G.; Mostafavi-Amjad, J.; Khalesifard, H. R. M.; Tatoulian, M.; Bonn, D.

    2016-07-01

    A new method for the elaboration of a novel type of catalytic microsystem with a high specific area catalyst is developed. A silver nanocluster catalytic microreactor was elaborated by doping a soda-lime glass with a silver salt. By applying a high power laser beam to the glass, silver nanoclusters are obtained at one of the surfaces which were characterized by BET measurements and AFM. A microfluidic chip was obtained by sealing the silver coated glass with a NOA 81 microchannel. The catalytic activity of the silver nanoclusters was then tested for the efficiency of water purification by using catalytic ozonation to oxidize an organic pollutant. The silver nanoclusters were found to be very stable in the microreactor and efficiently oxidized the pollutant, in spite of the very short residence times in the microchannel. This opens the way to study catalytic reactions in microchannels without the need of introducing the catalyst as a powder or manufacturing complex packed bed microreactors.

  13. Electrochemical fabrication of Cu(OH) 2 and CuO nanostructures and their catalytic property

    NASA Astrophysics Data System (ADS)

    Ming, Hai; Pan, Keming; Liu, Yang; Li, Haitao; He, Xiaodie; Ming, Jun; Ma, Zheng; Kang, Zhenhui

    2011-07-01

    In this paper, we reported an anodization method for the fabrication of novel uniform Cu(OH) 2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles with advanced structures. The possible formation mechanism of Cu(OH) 2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles was proposed. The good catalytic properties of CuO nanoparticles converted from Cu(OH) 2 nanowires and the CuO shuttle-like nanoparticles were confirmed by evaluating their catalytic ability on the C-N cross coupling of amines with iodobenzene.

  14. Catalytic decarbonylation of biosourced substrates.

    PubMed

    Ternel, Jérémy; Lebarbé, Thomas; Monflier, Eric; Hapiot, Frédéric

    2015-05-11

    Linear α-olefins (LAO) are one of the main targets in the field of surfactants, lubricants, and polymers. With the depletion of petroleum resources, the production of LAO from renewable feedstocks has gained increasing interest in recent years. In the present study, we demonstrated that Ir catalysts were suitable to decarbonylate a wide range of biosourced substrates under rather mild conditions (160 °C, 5 h reaction time) in the presence of potassium iodide and acetic anhydride. The resulting LAO were obtained with good conversion and selectivity provided that the purity of the substrate, the nature of the ligand, and the amounts of the additives were controlled accurately. The catalytic system could be recovered efficiently by using a Kugelrohr distillation apparatus and recycled.

  15. Non-catalytic recuperative reformer

    SciTech Connect

    Khinkis, Mark J.; Kozlov, Aleksandr P.; Kurek, Harry

    2015-12-22

    A non-catalytic recuperative reformer has a flue gas flow path for conducting hot flue gas from a thermal process and a reforming mixture flow path for conducting a reforming mixture. At least a portion of the reforming mixture flow path is embedded in the flue gas flow path to permit heat transfer from the hot flue gas to the reforming mixture. The reforming mixture flow path contains substantially no material commonly used as a catalyst for reforming hydrocarbon fuel (e.g., nickel oxide, platinum group elements or rhenium), but instead the reforming mixture is reformed into a higher calorific fuel via reactions due to the heat transfer and residence time. In a preferred embodiment, extended surfaces of metal material such as stainless steel or metal alloy that are high in nickel content are included within at least a portion of the reforming mixture flow path.

  16. Catalytic Carbonylative Spirolactonization of Hydroxycyclopropanols.

    PubMed

    Davis, Dexter C; Walker, Katherine L; Hu, Chunhua; Zare, Richard N; Waymouth, Robert M; Dai, Mingji

    2016-08-24

    A palladium-catalyzed cascade carbonylative spirolactonization of hydroxycyclopropanols has been developed to efficiently synthesize oxaspirolactones common to many complex natural products of important therapeutic value. The mild reaction conditions, high atom economy, broad substrate scope, and scalability of this new method were highlighted in expedient total syntheses of the Turkish tobacco natural products α-levantanolide and α-levantenolide in two and four steps, respectively. The hydroxycyclopropanol substrates are readily available in one step via a Kulinkovich reaction of the corresponding lactones. Mechanistic studies utilizing high-resolution electrospray ionization mass spectrometry (ESI-MS) identified several key intermediates in the catalytic cycle, as well as those related to catalyst decomposition and competitive pathways. PMID:27459274

  17. APPARATUS FOR CATALYTICALLY COMBINING GASES

    DOEpatents

    Busey, H.M.

    1958-08-12

    A convection type recombiner is described for catalytically recombining hydrogen and oxygen which have been radiolytically decomposed in an aqueous homogeneous nuclear reactor. The device is so designed that the energy of recombination is used to circulate the gas mixture over the catalyst. The device consists of a vertical cylinder having baffles at its lower enda above these coarse screens having platinum and alumina pellets cemented thereon, and an annular passage for the return of recombined, condensed water to the reactor moderator system. This devicea having no moving parts, provides a simple and efficient means of removing the danger of accumulated hot radioactive, explosive gases, and restoring them to the moderator system for reuse.

  18. Wood stove having catalytic converter

    SciTech Connect

    Willson, A.C.

    1982-12-14

    A wood burning stove is formed with double front and rear side walls of heat conductive metal spaced apart by heat conductive spacer fins and providing air passageways by which room air is heated by conduction from the walls which are heated by the burning of wood deposited on a firebox floor supported in heat conducting relationship with the inner side walls. A catalytic converter is disposed over the fire area in the upper portion of the stove, and is arranged to receive preheated fresh secondary air which mixes with hot, incompletely combusted compounds from the fire and, in the presence of the catalyst, induces a secondary combustion of the substances. This mixture is channeled into a heat extraction chamber where the secondary combustion is completed and the resultant heat is transferred to the metal body of the stove. An exhaust passageway is provided for releasing the products of complete combustion into the atmosphere.

  19. Catalytic reactor with improved burner

    DOEpatents

    Faitani, Joseph J.; Austin, George W.; Chase, Terry J.; Suljak, George T.; Misage, Robert J.

    1981-01-01

    To more uniformly distribute heat to the plurality of catalyst tubes in a catalytic reaction furnace, the burner disposed in the furnace above the tops of the tubes includes concentric primary and secondary annular fuel and air outlets. The fuel-air mixture from the primary outlet is directed towards the tubes adjacent the furnace wall, and the burning secondary fuel-air mixture is directed horizontally from the secondary outlet and a portion thereof is deflected downwardly by a slotted baffle toward the tubes in the center of the furnace while the remaining portion passes through the slotted baffle to another baffle disposed radially outwardly therefrom which deflects it downwardly in the vicinity of the tubes between those in the center and those near the wall of the furnace.

  20. Nonadiabatic Coupling

    NASA Astrophysics Data System (ADS)

    Kryachko, Eugene S.

    The general features of the nonadiabatic coupling and its relation to molecular properties are surveyed. Some consequences of the [`]equation of motion', formally expressing a [`]smoothness' of a given molecular property within the diabatic basis, are demonstrated. A particular emphasis is made on the relation between a [`]smoothness' of the electronic dipole moment and the generalized Mulliken-Hush formula for the diabatic electronic coupling.

  1. Revolutionary systems for catalytic combustion and diesel catalytic particulate traps.

    SciTech Connect

    Stuecker, John Nicholas; Witze, Peter O.; Ferrizz, Robert Matthew; Cesarano, Joseph, III; Miller, James Edward

    2004-12-01

    This report is a summary of an LDRD project completed for the development of materials and structures conducive to advancing the state of the art for catalyst supports and diesel particulate traps. An ancillary development for bio-medical bone scaffolding was also realized. Traditionally, a low-pressure drop catalyst support, such as a ceramic honeycomb monolith, is used for catalytic reactions that require high flow rates of gases at high-temperatures. A drawback to the traditional honeycomb monoliths under these operating conditions is poor mass transfer to the catalyst surface in the straight-through channels. ''Robocasting'' is a unique process developed at Sandia National Laboratories that can be used to manufacture ceramic monoliths with alternative 3-dimensional geometries, providing tortuous pathways to increase mass transfer while maintaining low-pressure drops. These alternative 3-dimensional geometries may also provide a foundation for the development of self-regenerating supports capable of trapping and combusting soot particles from a diesel engine exhaust stream. This report describes the structures developed and characterizes the improved catalytic performance that can result. The results show that, relative to honeycomb monolith supports, considerable improvement in mass transfer efficiency is observed for robocast samples synthesized using an FCC-like geometry of alternating rods. Also, there is clearly a trade-off between enhanced mass transfer and increased pressure drop, which can be optimized depending on the particular demands of a given application. Practical applications include the combustion of natural gas for power generation, production of syngas, and hydrogen reforming reactions. The robocast lattice structures also show practicality for diesel particulate trapping. Preliminary results for trapping efficiency are reported as well as the development of electrically resistive lattices that can regenerate the structure by combusting the

  2. Structure-based identification of catalytic residues.

    PubMed

    Yahalom, Ran; Reshef, Dan; Wiener, Ayana; Frankel, Sagiv; Kalisman, Nir; Lerner, Boaz; Keasar, Chen

    2011-06-01

    The identification of catalytic residues is an essential step in functional characterization of enzymes. We present a purely structural approach to this problem, which is motivated by the difficulty of evolution-based methods to annotate structural genomics targets that have few or no homologs in the databases. Our approach combines a state-of-the-art support vector machine (SVM) classifier with novel structural features that augment structural clues by spatial averaging and Z scoring. Special attention is paid to the class imbalance problem that stems from the overwhelming number of non-catalytic residues in enzymes compared to catalytic residues. This problem is tackled by: (1) optimizing the classifier to maximize a performance criterion that considers both Type I and Type II errors in the classification of catalytic and non-catalytic residues; (2) under-sampling non-catalytic residues before SVM training; and (3) during SVM training, penalizing errors in learning catalytic residues more than errors in learning non-catalytic residues. Tested on four enzyme datasets, one specifically designed by us to mimic the structural genomics scenario and three previously evaluated datasets, our structure-based classifier is never inferior to similar structure-based classifiers and comparable to classifiers that use both structural and evolutionary features. In addition to the evaluation of the performance of catalytic residue identification, we also present detailed case studies on three proteins. This analysis suggests that many false positive predictions may correspond to binding sites and other functional residues. A web server that implements the method, our own-designed database, and the source code of the programs are publicly available at http://www.cs.bgu.ac.il/∼meshi/functionPrediction.

  3. The Influence of Elastic Strain on Catalytic Activity in the Hydrogen Evolution Reaction.

    PubMed

    Yan, Kai; Maark, Tuhina Adit; Khorshidi, Alireza; Sethuraman, Vijay A; Peterson, Andrew A; Guduru, Pradeep R

    2016-05-17

    Understanding the role of elastic strain in modifying catalytic reaction rates is crucial for catalyst design, but experimentally, this effect is often coupled with a ligand effect. To isolate the strain effect, we have investigated the influence of externally applied elastic strain on the catalytic activity of metal films in the hydrogen evolution reaction (HER). We show that elastic strain tunes the catalytic activity in a controlled and predictable way. Both theory and experiment show strain controls reactivity in a controlled manner consistent with the qualitative predictions of the HER volcano plot and the d-band theory: Ni and Pt's activities were accelerated by compression, while Cu's activity was accelerated by tension. By isolating the elastic strain effect from the ligand effect, this study provides a greater insight into the role of elastic strain in controlling electrocatalytic activity. PMID:27079940

  4. A catalytic approach to estimate the redox potential of heme-peroxidases

    SciTech Connect

    Ayala, Marcela . E-mail: maa@ibt.unam.mx; Roman, Rosa; Vazquez-Duhalt, Rafael

    2007-06-08

    The redox potential of heme-peroxidases varies according to a combination of structural components within the active site and its vicinities. For each peroxidase, this redox potential imposes a thermodynamic threshold to the range of oxidizable substrates. However, the instability of enzymatic intermediates during the catalytic cycle precludes the use of direct voltammetry to measure the redox potential of most peroxidases. Here we describe a novel approach to estimate the redox potential of peroxidases, which directly depends on the catalytic performance of the activated enzyme. Selected p-substituted phenols are used as substrates for the estimations. The results obtained with this catalytic approach correlate well with the oxidative capacity predicted by the redox potential of the Fe(III)/Fe(II) couple.

  5. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    PubMed Central

    Wang, Yang-Gang; Mei, Donghai; Glezakou, Vassiliki-Alexandra; Li, Jun; Rousseau, Roger

    2015-01-01

    Catalysis by gold supported on reducible oxides has been extensively studied, yet issues such as the nature of the catalytic site and the role of the reducible support remain fiercely debated topics. Here we present ab initio molecular dynamics simulations of an unprecedented dynamic single-atom catalytic mechanism for the oxidation of carbon monoxide by ceria-supported gold clusters. The reported dynamic single-atom catalytic mechanism results from the ability of the gold cation to strongly couple with the redox properties of the ceria in a synergistic manner, thereby lowering the energy of redox reactions. The gold cation can break away from the gold nanoparticle to catalyse carbon monoxide oxidation, adjacent to the metal/oxide interface and subsequently reintegrate back into the nanoparticle after the reaction is completed. Our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in catalysis. PMID:25735407

  6. Effect of Porosity on Surface Catalytic Efficiency

    NASA Technical Reports Server (NTRS)

    Stewart, David A.; Pallix, Joan; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    This paper describes the effect of surface porosity of thermal protection materials on surface catalytic efficiency using test data taken from both arc-jet and side-arm reactor facilities. Relative surface porosity of the samples varied from 6% to 50%. Surface porosity was measured using a flow apparatus and Bernoulli equation. The surface catalytic efficiency of the materials was calculated using aerothermodynamic, and kinetic theories. The catalytic efficiency of the materials are compared at surface temperatures between room temperature and 2500 F. The data are presented in the form of graphs and tables.

  7. Catalytic reaction in confined flow channel

    DOEpatents

    Van Hassel, Bart A.

    2016-03-29

    A chemical reactor comprises a flow channel, a source, and a destination. The flow channel is configured to house at least one catalytic reaction converting at least a portion of a first nanofluid entering the channel into a second nanofluid exiting the channel. The flow channel includes at least one turbulating flow channel element disposed axially along at least a portion of the flow channel. A plurality of catalytic nanoparticles is dispersed in the first nanofluid and configured to catalytically react the at least one first chemical reactant into the at least one second chemical reaction product in the flow channel.

  8. FLEXIBLE COUPLING

    DOEpatents

    Babelay, E.F.

    1962-02-13

    A flexible shaft coupling for operation at speeds in excess of 14,000 rpm is designed which requires no lubrication. A driving sleeve member and a driven sleeve member are placed in concentric spaced relationship. A torque force is transmitted to the driven member from the driving member through a plurality of nylon balls symmetrically disposed between the spaced sleeves. The balls extend into races and recesses within the respective sleeve members. The sleeve members have a suitable clearance therebetween and the balls have a suitable radial clearance during operation of the coupling to provide a relatively loose coupling. These clearances accommodate for both parallel and/or angular misalignments and avoid metal-tometal contact between the sleeve members during operation. Thus, no lubrication is needed, and a minimum of vibrations is transmitted between the sleeve members. (AEC)

  9. Prosthesis coupling

    NASA Technical Reports Server (NTRS)

    Reswick, J. B.; Mooney, V.; Bright, C. W.; Owens, L. J. (Inventor)

    1979-01-01

    A coupling for use in an apparatus for connecting a prosthesis to the bone of a stump of an amputated limb is described which permits a bio-compatible carbon sleeve forming a part of the prosthesis connector to float so as to prevent disturbing the skin seal around the carbon sleeve. The coupling includes a flexible member interposed between a socket that is inserted within an intermedullary cavity of the bone and the sleeve. A lock pin is carried by the prosthesis and has a stem portion which is adapted to be coaxially disposed and slideably within the tubular female socket for securing the prosthesis to the stump. The skin around the percutaneous carbon sleeve is able to move as a result of the flexing coupling so as to reduce stresses caused by changes in the stump shape and/or movement between the bone and the flesh portion of the stump.

  10. Vacuum-insulated catalytic converter

    DOEpatents

    Benson, David K.

    2001-01-01

    A catalytic converter has an inner canister that contains catalyst-coated substrates and an outer canister that encloses an annular, variable vacuum insulation chamber surrounding the inner canister. An annular tank containing phase-change material for heat storage and release is positioned in the variable vacuum insulation chamber a distance spaced part from the inner canister. A reversible hydrogen getter in the variable vacuum insulation chamber, preferably on a surface of the heat storage tank, releases hydrogen into the variable vacuum insulation chamber to conduct heat when the phase-change material is hot and absorbs the hydrogen to limit heat transfer to radiation when the phase-change material is cool. A porous zeolite trap in the inner canister absorbs and retains hydrocarbons from the exhaust gases when the catalyst-coated substrates and zeolite trap are cold and releases the hydrocarbons for reaction on the catalyst-coated substrate when the zeolite trap and catalyst-coated substrate get hot.

  11. Fundamental studies of catalytic gasification

    SciTech Connect

    Heinemann, H.; Somorjai, G.A.

    1990-06-01

    Previous work has shown that chars and coal can be gasified with steam in the presence of alkali-transition metal oxide catalysts or alkali-earth alkali catalysts at relatively low temperatures. These studies are to be extended to the investigation of the amounts of catalysts required and whether a throw away catalyst can be used. Fresh versus stored char will be gasified to determine the role of oxidation of the char on gasification rates. Less expensive catalyst materials such as sodium instead of potassium and iron instead of nickel will be explored. Reaction rates will be determined in the presence of nitrogen, Co and CO{sub 2}. Reactions of methane and carbon solids in the presence of an oxidizing agent such as water, oxygen, and/or carbon dioxide will be explored in the presence of similar catalyst. This quarter, additional experiments on catalytic gasification of coal were carried out. Major emphasis, however, was on the production of C{sub 2} and higher hydrocarbons from methane at very high selectivities. Catalysts studied include KCaNiO. 6 figs., 1 tab.

  12. Halogen Chemistry on Catalytic Surfaces.

    PubMed

    Moser, Maximilian; Pérez-Ramírez, Javier

    2016-01-01

    Halogens are key building blocks for the manufacture of high-value products such as chemicals, plastics, and pharmaceuticals. The catalytic oxidation of HCl and HBr is an attractive route to recover chlorine and bromine in order to ensure the sustainability of the production processes. Very few materials withstand the high corrosiveness and the strong exothermicity of the reactions and among them RuO2 and CeO2-based catalysts have been successfully applied in HCl oxidation. The search for efficient systems for HBr oxidation was initiated by extrapolating the results of HCl oxidation based on the chemical similarity of these reactions. Interestingly, despite its inactivity in HCl oxidation, TiO2 was found to be an outstanding HBr oxidation catalyst, which highlighted that the latter reaction is more complex than previously assumed. Herein, we discuss the results of recent comparative studies of HCl and HBr oxidation on both rutile-type (RuO2, IrO2, and TiO2) and ceria-based catalysts using a combination of advanced experimental and theoretical methods to provide deeper molecular-level understanding of the reactions. This knowledge aids the design of the next-generation catalysts for halogen recycling. PMID:27131113

  13. A review of tin oxide-based catalytic systems: Preparation, characterization and catalytic behavior

    NASA Technical Reports Server (NTRS)

    Hoflund, Gar B.

    1987-01-01

    This paper reviews the important aspects of the preparation, characterization and catalytic behavior of tin oxide-based catalytic systems including doped tin oxide, mixed oxides which contain tin oxide, Pt supported on tin oxide and Pt/Sn supported on alumina. These systems have a broad range of applications and are continually increasing in importance. However, due to their complex nature, much remains to be understood concerning how they function catalytically.

  14. Tremendous effect of the morphology of birnessite-type manganese oxide nanostructures on catalytic activity.

    PubMed

    Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Ren, Lu; Zhao, Xiujian

    2014-09-10

    The octahedral layered birnessite-type manganese oxide (OL-1) with the morphologies of nanoflowers, nanowires, and nanosheets were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric/differential scanning calorimetry (TG/DSC), Brunnauer-Emmett-Teller (BET), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS). The OL-1 nanoflowers possess the highest concentration of oxygen vacancies or Mn(3+), followed by the OL-1 nanowires and nanosheets. The result of catalytic tests shows that the OL-1 nanoflowers exhibit a tremendous enhancement in the catalytic activity for benzene oxidation as compared to the OL-1 nanowires and nanosheets. Compared to the OL-1 nanosheets, the OL-1 nanoflowers demonstrate an enormous decrease (ΔT(50) = 274 °C; ΔT(90) > 248 °C) in reaction temperatures T50 and T90 (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation. The origin of the tremendous effect of morphology on the catalytic activity for the nanostructured OL-1 catalysts is experimentally and theoretically studied via CO temperature-programmed reduction (CO-TPR) and density functional theory (DFT) calculation. The tremendous catalytic enhancement of the OL-1 nanoflowers compared to the OL-1 nanowires and nanosheets is attributed to their highest surface area as well as their highest lattice oxygen reactivity due to their higher concentration of oxygen vacancies or Mn(3+), thus tremendously improving the catalytic activity for the benzene oxidation.

  15. Thicker is better? Synthesis and evaluation of well-defined polymer brushes with controllable catalytic loadings.

    PubMed

    Fernandes, Antony E; Dirani, Ali; d'Haese, Cécile; Deumer, Gladys; Guo, Weiming; Hensenne, Peter; Nahra, Fady; Laloyaux, Xavier; Haufroid, Vincent; Nysten, Bernard; Riant, Olivier; Jonas, Alain M

    2012-12-01

    Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface-initiated atom-transfer radical polymerization (SI-ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn complexed with [Pd(OAc)(2)] to afford hybrid catalytic surfaces. A series of catalytic samples of various thicknesses (ca. 20-160 nm) and associated palladium loadings (ca. 10-45 nmol  cm(-2)) were obtained by adjusting the SI-ATRP reaction time and characterized by ellipsometry, X-ray reflectivity, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS revealed a near-linear relationship between thickness of the polymer brush and palladium content, which confirmed the robustness of the preparation and postmodification sequence presented herein, rendering possible the creation of functional architectures with predefined catalytic potential. The activities of the catalytic PBs were determined by systematically exploring a full range of substrate-to-catalyst ratios in a model palladium(0)-catalyzed reaction. Quantitative transformations were observed for loadings down to 0.03 mol % and a maximum turnover number (TON) of around 3500 was established for the system. Comparison of the catalytic performances evidenced a singular influence of the thickness on conversions and TONs. The limited recyclability of the hairy catalysts has been attributed to palladium leaching. PMID:23032959

  16. Chemical and catalytic properties of elemental carbon

    SciTech Connect

    Chang, S.G.; Brodzinsky, R.; Gundel, L.A.; Novakov, T.

    1980-10-01

    Elemental carbon particles resulting from incomplete combustion of fossil fuel are one of the major constituents of airborne particulate matter. These particles are a chemically and catalytically active material and can be an effective carrier for other toxic air pollutants through their adsorptive capability. The chemical, adsorptive, and catalytic behaviors of carbon particles depend very much on their crystalline structure, surface composition, and electronic properties. This paper discusses these properties and examines their relevance to atmospheric chemistry.

  17. Correlation of Catalytic Rates With Solubility Parameters

    NASA Technical Reports Server (NTRS)

    Lawson, Daniel D.; England, Christopher

    1987-01-01

    Catalyst maximizes activity when its solubility parameter equals that of reactive species. Catalytic activities of some binary metal alloys at maximum when alloy compositions correspond to Hildebrand solubility parameters equal to those of reactive atomic species on catalyst. If this suggestive correlation proves to be general, applied to formulation of other mixed-metal catalysts. Also used to identify reactive species in certain catalytic reactions.

  18. Autonomously motile catalytic nanomotors by bubble propulsion

    NASA Astrophysics Data System (ADS)

    Gibbs, J. G.; Zhao, Y.-P.

    2009-04-01

    A bubble propulsion model based on catalyzed hydrogen peroxide decomposition and momentum change via O2 bubbles detaching from the catalytic surface is proposed to explain the autonomous motion of catalytic nanomotors. The propelling force closely depends upon the surface tension of the liquid as well as the bulk concentration of hydrogen peroxide, and the model predictions are supported by the experimental data of Pt-coated spherical silica microbead motors.

  19. Catalytic Radical Domino Reactions in Organic Synthesis

    PubMed Central

    Sebren, Leanne J.; Devery, James J.; Stephenson, Corey R.J.

    2014-01-01

    Catalytic radical-based domino reactions represent important advances in synthetic organic chemistry. Their development benefits synthesis by providing atom- and step-economical methods to complex molecules. Intricate combinations of radical, cationic, anionic, oxidative/reductive, and transition metal mechanistic steps result in cyclizations, additions, fragmentations, ring-expansions, and rearrangements. This Perspective summarizes recent developments in the field of catalytic domino processes. PMID:24587964

  20. An Iron Reservoir to the Catalytic Metal

    PubMed Central

    Liu, Fange; Geng, Jiafeng; Gumpper, Ryan H.; Barman, Arghya; Davis, Ian; Ozarowski, Andrew; Hamelberg, Donald; Liu, Aimin

    2015-01-01

    The rubredoxin motif is present in over 74,000 protein sequences and 2,000 structures, but few have known functions. A secondary, non-catalytic, rubredoxin-like iron site is conserved in 3-hydroxyanthranilate 3,4-dioxygenase (HAO), from single cellular sources but not multicellular sources. Through the population of the two metal binding sites with various metals in bacterial HAO, the structural and functional relationship of the rubredoxin-like site was investigated using kinetic, spectroscopic, crystallographic, and computational approaches. It is shown that the first metal presented preferentially binds to the catalytic site rather than the rubredoxin-like site, which selectively binds iron when the catalytic site is occupied. Furthermore, an iron ion bound to the rubredoxin-like site is readily delivered to an empty catalytic site of metal-free HAO via an intermolecular transfer mechanism. Through the use of metal analysis and catalytic activity measurements, we show that a downstream metabolic intermediate can selectively remove the catalytic iron. As the prokaryotic HAO is often crucial for cell survival, there is a need for ensuring its activity. These results suggest that the rubredoxin-like site is a possible auxiliary iron source to the catalytic center when it is lost during catalysis in a pathway with metabolic intermediates of metal-chelating properties. A spare tire concept is proposed based on this biochemical study, and this concept opens up a potentially new functional paradigm for iron-sulfur centers in iron-dependent enzymes as transient iron binding and shuttling sites to ensure full metal loading of the catalytic site. PMID:25918158

  1. Direct electrochemistry of Megasphaera elsdenii iron hydrogenase. Definition of the enzyme's catalytic operating potential and quantitation of the catalytic behaviour over a continuous potential range.

    PubMed

    Butt, J N; Filipiak, M; Hagen, W R

    1997-04-01

    The Fe-hydrogenase from Megasphaera elsdenii undergoes direct electron exchange with glassy carbon electrodes. Cyclic voltammetry defines the catalytic-performance of the enzyme over a continuous but precisely defined range of potentials. In the presence of H2 and protons the bias of the enzyme towards H2 production is readily visualised. Variation of the response with pH indicates that protein ionisations with pK of approximately 6.7 and 8.3 regulate the catalytic activity. Possible origins for these observations in the chemistry of the H2-activating site are discussed. The mid-wave potential of the catalytic response, Emid, is defined as the catalytic operating potential of the enzyme. Under an atmosphere of hydrogen Emid = -421 +/- 10 mV, pH 7 with a variation of -21 +/- 4 mV pH-1, 22 degrees C. Deviation of Emid from the thermodynamic potential of the hydrogen/proton couple reflects the enzyme's influence over the catalysed reaction. Emid is the reduction potential of the H2-activating centre (H-cluster) in the absence of kinetic bottle-necks at other steps in the reaction mechanism.

  2. Catalytic Reduction of CO2 by Renewable Organohydrides.

    PubMed

    Lim, Chern-Hooi; Holder, Aaron M; Hynes, James T; Musgrave, Charles B

    2015-12-17

    Dihydropyridines are renewable organohydride reducing agents for the catalytic reduction of CO2 to MeOH. Here we discuss various aspects of this important reduction. A centerpiece, which illustrates various general principles, is our theoretical catalytic mechanism for CO2 reduction by successive hydride transfers (HTs) and proton transfers (PTs) from the dihydropyridine PyH2 obtained by 1H(+)/1e(-)/1H(+)/1e(-) reductions of pyridine. The Py/PyH2 redox couple is analogous to NADP(+)/NADPH in that both are driven to effect HTs by rearomatization. High-energy radical intermediates and their associated high barriers/overpotentials are avoided because HT involves a 2e(-) reduction. A HT-PT sequence dictates that the reduced intermediates be protonated prior to further reduction for ultimate MeOH formation; these protonations are aided by biased cathodes that significantly lower the local pH. In contrast, cathodes that efficiently reduce H(+) such as Pt and Pd produce H2 and create a high interfacial pH, both obstructing dihydropyridine production and formate protonation and thus ultimately CO2 reduction by HTPTs. The role of water molecule proton relays is discussed. Finally, we suggest future CO2 reduction strategies by organic (photo)catalysts. PMID:26722706

  3. Palladium-Catalyzed Cross Coupling of Secondary and Tertiary Alkyl Bromides with a Nitrogen Nucleophile

    PubMed Central

    2016-01-01

    We report a new class of catalytic reaction: the thermal substitution of a secondary and or tertiary alkyl halide with a nitrogen nucleophile. The alkylation of a nitrogen nucleophile with an alkyl halide is a classical method for the construction of C–N bonds, but traditional substitution reactions are challenging to achieve with a secondary and or tertiary alkyl electrophile due to competing elimination reactions. A catalytic process could address this limitation, but thermal, catalytic coupling of alkyl halides with a nitrogen nucleophile and any type of catalytic coupling of an unactivated tertiary alkyl halide with a nitrogen nucleophile are unknown. We report the coupling of unactivated secondary and tertiary alkyl bromides with benzophenone imines to produce protected primary amines in the presence of palladium ligated by the hindered trialkylphosphine Cy2t-BuP. Mechanistic studies indicate that this amination of alkyl halides occurs by a reversible reaction to form a free alkyl radical. PMID:27725963

  4. Photoredox Catalysis in Nickel-Catalyzed Cross-Coupling.

    PubMed

    Cavalcanti, Livia N; Molander, Gary A

    2016-08-01

    The traditional transition metal-catalyzed cross-coupling reaction, although well suited for C(sp2)-C(sp2) cross-coupling, has proven less amenable toward coupling of C(sp3)-hybridized centers, particularly using functional group tolerant reagents and reaction conditions. The development of photoredox/Ni dual catalytic methods for cross-coupling has opened new vistas for the construction of carbon-carbon bonds at C(sp3)-hybridized centers. In this chapter, a general outline of the features of such processes is detailed. PMID:27573391

  5. Preconversion catalytic deoxygenation of phenolic functional groups. Quarterly technical progress report, January 1, 1995--March 31, 1995

    SciTech Connect

    Kubiak, C.P.

    1995-10-01

    The viability of the catalytic deoxygenation of phenols by carbon monoxide has been established in our laboratory. We are currently studying new transition metal catalysts for the efficient and selective deoxygenation of phenols using the carbon monoxide/carbon dioxide couple to remove phenolic oxygen atoms.

  6. Nitrene Metathesis and Catalytic Nitrene Transfer Promoted by Niobium Bis(imido) Complexes.

    PubMed

    Kriegel, Benjamin M; Bergman, Robert G; Arnold, John

    2016-01-13

    We report a metathesis reaction in which a nitrene fragment from an isocyanide ligand is exchanged with a nitrene fragment of an imido ligand in a series of niobium bis(imido) complexes. One of these bis(imido) complexes also promotes nitrene transfer to catalytically generate asymmetric dialkylcarbodiimides from azides and isocyanides in a process involving the Nb(V)/Nb(III) redox couple. PMID:26698833

  7. Catalytic activity of nuclease P1: Experiment and theory

    SciTech Connect

    Miller, J.H.; Falcone, J.M.; Shibata, M.; Box, H.C.

    1994-10-01

    Nuclease P1 from Penicillium citrinum is a zinc dependent glyco-enzyme that recognizes single stranded DNA and RNA as substrates and hydrolyzes the phosphate ester bond. Nuclease Pl seems to recognize particular conformations of the phosphodiester backbone and shows significant variation in the rate of hydrolytic activity depending upon which nucleosides are coupled by the phosphodiester bond. The efficiency of nuclease Pl in hydrolyzing the phosphodiester bonds of a substrate can be altered by modifications to one of the substrate bases induced by ionizing radiation or oxidative stress. Measurements have been made of the effect of several radiation induced lesions on the catalytic rate of nuclease Pl. A model of the structure of the enzyme has been constructed in order to better understand the binding and activity of this enzyme on various ssDNA substrates.

  8. Kinetically controlled E-selective catalytic olefin metathesis.

    PubMed

    Nguyen, Thach T; Koh, Ming Joo; Shen, Xiao; Romiti, Filippo; Schrock, Richard R; Hoveyda, Amir H

    2016-04-29

    A major shortcoming in olefin metathesis, a chemical process that is central to research in several branches of chemistry, is the lack of efficient methods that kinetically favor E isomers in the product distribution. Here we show that kinetically E-selective cross-metathesis reactions may be designed to generate thermodynamically disfavored alkenyl chlorides and fluorides in high yield and with exceptional stereoselectivity. With 1.0 to 5.0 mole % of a molybdenum-based catalyst, which may be delivered in the form of air- and moisture-stable paraffin pellets, reactions typically proceed to completion within 4 hours at ambient temperature. Many isomerically pure E-alkenyl chlorides, applicable to catalytic cross-coupling transformations and found in biologically active entities, thus become easily and directly accessible. Similarly, E-alkenyl fluorides can be synthesized from simpler compounds or more complex molecules.

  9. Kinetically controlled E-selective catalytic olefin metathesis.

    PubMed

    Nguyen, Thach T; Koh, Ming Joo; Shen, Xiao; Romiti, Filippo; Schrock, Richard R; Hoveyda, Amir H

    2016-04-29

    A major shortcoming in olefin metathesis, a chemical process that is central to research in several branches of chemistry, is the lack of efficient methods that kinetically favor E isomers in the product distribution. Here we show that kinetically E-selective cross-metathesis reactions may be designed to generate thermodynamically disfavored alkenyl chlorides and fluorides in high yield and with exceptional stereoselectivity. With 1.0 to 5.0 mole % of a molybdenum-based catalyst, which may be delivered in the form of air- and moisture-stable paraffin pellets, reactions typically proceed to completion within 4 hours at ambient temperature. Many isomerically pure E-alkenyl chlorides, applicable to catalytic cross-coupling transformations and found in biologically active entities, thus become easily and directly accessible. Similarly, E-alkenyl fluorides can be synthesized from simpler compounds or more complex molecules. PMID:27126041

  10. VOC Destruction by Catalytic Combustion Microturbine

    SciTech Connect

    Tom Barton

    2009-03-10

    This project concerned the application of a catalytic combustion system that has been married to a micro-turbine device. The catalytic combustion system decomposes the VOC's and transmits these gases to the gas turbine. The turbine has been altered to operate on very low-level BTU fuels equivalent to 1.5% methane in air. The performance of the micro-turbine for VOC elimination has some flexibility with respect to operating conditions, and the system is adaptable to multiple industrial applications. The VOC source that was been chosen for examination was the emissions from coal upgrading operations. The overall goal of the project was to examine the effectiveness of a catalytic combustion based system for elimination of VOCs while simultaneously producing electrical power for local consumption. Project specific objectives included assessment of the feasibility for using a Flex-Microturbine that generates power from natural gas while it consumes VOCs generated from site operations; development of an engineering plan for installation of the Flex-Microturbine system; operation of the micro-turbine through various changes in site and operation conditions; measurement of the VOC destruction quantitatively; and determination of the required improvements for further studies. The micro-turbine with the catalytic bed worked effectively to produce power on levels of fuel much lower than the original turbine design. The ability of the device to add or subtract supplemental fuel to augment the amount of VOC's in the inlet air flow made the device an effective replacement for a traditional flare. Concerns about particulates in the inlet flow and the presence of high sulfur concentrations with the VOC mixtures was identified as a drawback with the current catalytic design. A new microturbine design was developed based on this research that incorporates a thermal oxidizer in place of the catalytic bed for applications where particulates or contamination would limit the lifetime of

  11. SOFC system with integrated catalytic fuel processing

    NASA Astrophysics Data System (ADS)

    Finnerty, Caine; Tompsett, Geoff. A.; Kendall, Kevin; Ormerod, R. Mark

    In recent years, there has been much interest in the development of solid oxide fuel cell technology operating directly on hydrocarbon fuels. The development of a catalytic fuel processing system, which is integrated with the solid oxide fuel cell (SOFC) power source is outlined here. The catalytic device utilises a novel three-way catalytic system consisting of an in situ pre-reformer catalyst, the fuel cell anode catalyst and a platinum-based combustion catalyst. The three individual catalytic stages have been tested in a model catalytic microreactor. Both temperature-programmed and isothermal reaction techniques have been applied. Results from these experiments were used to design the demonstration SOFC unit. The apparatus used for catalytic characterisation can also perform in situ electrochemical measurements as described in previous papers [C.M. Finnerty, R.H. Cunningham, K. Kendall, R.M. Ormerod, Chem. Commun. (1998) 915-916; C.M. Finnerty, N.J. Coe, R.H. Cunningham, R.M. Ormerod, Catal. Today 46 (1998) 137-145]. This enabled the performance of the SOFC to be determined at a range of temperatures and reaction conditions, with current output of 290 mA cm -2 at 0.5 V, being recorded. Methane and butane have been evaluated as fuels. Thus, optimisation of the in situ partial oxidation pre-reforming catalyst was essential, with catalysts producing high H 2/CO ratios at reaction temperatures between 873 K and 1173 K being chosen. These included Ru and Ni/Mo-based catalysts. Hydrocarbon fuels were directly injected into the catalytic SOFC system. Microreactor measurements revealed the reaction mechanisms as the fuel was transported through the three-catalyst device. The demonstration system showed that the fuel processing could be successfully integrated with the SOFC stack.

  12. Simultaneous probing of bulk liquid phase and catalytic gas-liquid-solid interface under working conditions using attenuated total reflection infrared spectroscopy

    SciTech Connect

    Meemken, Fabian; Müller, Philipp; Hungerbühler, Konrad; Baiker, Alfons

    2014-08-15

    Design and performance of a reactor set-up for attenuated total reflection infrared (ATR-IR) spectroscopy suitable for simultaneous reaction monitoring of bulk liquid and catalytic solid-liquid-gas interfaces under working conditions are presented. As advancement of in situ spectroscopy an operando methodology for gas-liquid-solid reaction monitoring was developed that simultaneously combines catalytic activity and molecular level detection at the catalytically active site of the same sample. Semi-batch reactor conditions are achieved with the analytical set-up by implementing the ATR-IR flow-through cell in a recycle reactor system and integrating a specifically designed gas feeding system coupled with a bubble trap. By the use of only one spectrometer the design of the new ATR-IR reactor cell allows for simultaneous detection of the bulk liquid and the catalytic interface during the working reaction. Holding two internal reflection elements (IRE) the sample compartments of the horizontally movable cell are consecutively flushed with reaction solution and pneumatically actuated, rapid switching of the cell (<1 s) enables to quasi simultaneously follow the heterogeneously catalysed reaction at the catalytic interface on a catalyst-coated IRE and in the bulk liquid on a blank IRE. For a complex heterogeneous reaction, the asymmetric hydrogenation of 2,2,2-trifluoroacetophenone on chirally modified Pt catalyst the elucidation of catalytic activity/enantioselectivity coupled with simultaneous monitoring of the catalytic solid-liquid-gas interface is shown. Both catalytic activity and enantioselectivity are strongly dependent on the experimental conditions. The opportunity to gain improved understanding by coupling measurements of catalytic performance and spectroscopic detection is presented. In addition, the applicability of modulation excitation spectroscopy and phase-sensitive detection are demonstrated.

  13. Synthesis of mesoporous Co/Ce-SBA-15 materials and their catalytic performance in the catalytic oxidation of benzene

    SciTech Connect

    Mu Zhen; Li Jinjun; Tian Hua; Hao Zhengping Qiao Shizhang

    2008-10-02

    Cerium-containing SBA-15 mesoporous materials, with different Ce/Si molar ratios, were synthesized by a direct hydrothermal synthesis method and further modified by impregnation with 10, 15 and 20 wt.% Co. Characterizations by powder X-ray diffraction (XRD), N{sub 2} sorption, inductively coupled plasma (ICP) and UV-vis spectroscopy were carried out. The small-angle XRD and N{sub 2} sorption characterizations showed that these Co supported materials have less-ordered mesoporous structures with partial blockage of pores, and their specific surface area, pore volume and pore size were relatively lower than those of unsupported cerium-containing SBA-15. Spinel Co{sub 3}O{sub 4} constituted the predominant cobalt phase in the prepared catalysts, and CeO{sub 2} was also detected. All the Co supported catalysts exhibited high catalytic activity in the oxidation of benzene.

  14. Using Catalytic Atom Maps to Predict the Catalytic Functions Present in Enzyme Active Sites

    PubMed Central

    Nosrati, Geoffrey R.; Houk, K. N.

    2012-01-01

    Catalytic Atom Maps (CAMs) are minimal models of enzyme active sites. The structures in the Protein Data Bank (PDB) were examined to determine if proteins with CAM-like geometries in their active sites all share the same catalytic function. We combined the CAM-based search protocol with a filter based on the weighted contact number (WCN) of the catalytic residues, a measure of the “crowdedness” of the microenvironment around a protein residue. Using this technique, a CAM based on the Ser-His-Asp catalytic triad of trypsin was able to correctly identify catalytic triads in other enzymes within 0.5 Å RMSD of the Catalytic Atom Map with 96% accuracy. A CAM based on the Cys-Arg-(Asp/Glu) active site residues from the tyrosine phosphatase active site achieved 89% accuracy in identifying this type of catalytic functionality. Both of these Catalytic Atom Maps were able to identify active sites across different fold types. Finally, the PDB was searched to locate proteins with catalytic functionality similar to that present in the active site of orotidine 5′-monophosphate decarboxylase (ODCase), whose mechanism is not known with certainty. A CAM, based on the conserved Lys-Asp-Lys-Asp tetrad in the ODCase active site, was used to search the PDB for enzymes with similar active sites. The ODCase active site has a geometry similar to that of Schiff base-forming Class I aldolases, with lowest aldolase RMSD to the ODCase CAM at 0.48 Å. The similarity between this CAM and the aldolase active site suggests that ODCase has the correct catalytic functionality present in its active site for the generation of a nucleophilic lysine. PMID:22909276

  15. Catalytic Combustor for Fuel-Flexible Turbine

    SciTech Connect

    W. R. Laster; E. Anoshkina

    2008-01-31

    Under the sponsorship of the U. S. Department of Energy's National Energy Technology Laboratory, Siemens Westinghouse has conducted a three-year program to develop an ultra low NOx, fuel flexible catalytic combustor for gas turbine application in IGCC. The program is defined in three phases: Phase 1 - Implementation Plan, Phase 2 - Validation Testing and Phase 3 - Field Testing. Both Phase 1 and Phase 2 of the program have been completed. In IGCC power plants, the gas turbine must be capable of operating on syngas as a primary fuel and an available back-up fuel such as natural gas. In this program the Rich Catalytic Lean (RCLTM) technology is being developed as an ultra low NOx combustor. In this concept, ultra low NOx is achieved by stabilizing a lean premix combustion process by using a catalytic reactor to oxidize a portion of the fuel, increasing the temperature of fuel/air mixture prior to the main combustion zone. In Phase 1, the feasibility of the catalytic concept for syngas application has been evaluated and the key technology issues identified. In Phase II the technology necessary for the application of the catalytic concept to IGCC fuels was developed through detailed design and subscale testing. Phase III (currently not funded) will consist of full-scale combustor basket testing on natural gas and syngas.

  16. Catalytic Combustor for Fuel-Flexible Turbine

    SciTech Connect

    Laster, W. R.; Anoshkina, E.

    2008-01-31

    Under the sponsorship of the U. S. Department of Energy’s National Energy Technology Laboratory, Siemens Westinghouse has conducted a three-year program to develop an ultra low NOx, fuel flexible catalytic combustor for gas turbine application in IGCC. The program is defined in three phases: Phase 1- Implementation Plan, Phase 2- Validation Testing and Phase 3 – Field Testing. Both Phase 1 and Phase 2 of the program have been completed. In IGCC power plants, the gas turbine must be capable of operating on syngas as a primary fuel and an available back-up fuel such as natural gas. In this program the Rich Catalytic Lean (RCLTM) technology is being developed as an ultra low NOx combustor. In this concept, ultra low NOx is achieved by stabilizing a lean premix combustion process by using a catalytic reactor to oxidize a portion of the fuel, increasing the temperature of fuel/air mixture prior to the main combustion zone. In Phase 1, the feasibility of the catalytic concept for syngas application has been evaluated and the key technology issues identified. In Phase II the technology necessary for the application of the catalytic concept to IGCC fuels was developed through detailed design and subscale testing. Phase III (currently not funded) will consist of full-scale combustor basket testing on natural gas and syngas.

  17. Catalytic Combustor for Fuel-Flexible Turbine

    SciTech Connect

    W. R. Laster; E. Anoshkina; P. Szedlacsek

    2006-03-31

    Under the sponsorship of the U.S. Department of Energy's National Energy Technology Laboratory, Siemens Westinghouse is conducting a three-year program to develop an ultra low NOx, fuel flexible catalytic combustor for gas turbine application in IGCC. The program is defined in three phases: Phase 1-Implementation Plan, Phase 2-Validation Testing and Phase 3-Field Testing. The Phase 1 program has been completed. Phase II was initiated in October 2004. In IGCC power plants, the gas turbine must be capable of operating on syngas as a primary fuel and an available back-up fuel such as natural gas. In this program the Rich Catalytic Lean (RCL{trademark}) technology is being developed as an ultra low NOx combustor. In this concept, ultra low NOx is achieved by stabilizing a lean premix combustion process by using a catalytic reactor to react part of the fuel, increasing the fuel/air mixture temperature. In Phase 1, the feasibility of the catalytic concept for syngas application has been evaluated and the key technology issues identified. In Phase II the catalytic concept will be demonstrated through subscale testing. Phase III will consist of full-scale combustor basket testing on natural gas and syngas.

  18. Convective stability in the presence of a catalytic chemical reaction. I.

    NASA Technical Reports Server (NTRS)

    Wankat, P. C.; Schowalter, W. R.

    1971-01-01

    A linear analysis of hydrodynamic stability has been applied to a problem in which a fluid mixture is contained between two horizontal planes. One species diffuses to the lower plane where it is destroyed by a rapid exothermic or endothermic catalytic reaction. Results show that important coupling takes place between thermal and concentration fields. This coupling gives rise to unusual stabilizing or destabilizing effects, depending upon the value of Lewis number. Several examples are discussed. It is also shown how the results can be applied to other problems involving heat and mass transfer.

  19. Visible Light Mediated Photoredox Catalytic Arylation Reactions.

    PubMed

    Ghosh, Indrajit; Marzo, Leyre; Das, Amrita; Shaikh, Rizwan; König, Burkhard

    2016-08-16

    Introducing aryl- and heteroaryl moieties into molecular scaffolds are often key steps in the syntheses of natural products, drugs, or functional materials. A variety of cross-coupling methods have been well established, mainly using transition metal mediated reactions between prefunctionalized substrates and arenes or C-H arylations with functionalization in only one coupling partner. Although highly developed, one drawback of the established sp2-sp2 arylations is the required transition metal catalyst, often in combination with specific ligands and additives. Therefore, photoredox mediated arylation methods have been developed as alternative over the past decade. We begin our survey with visible light photo-Meerwein arylation reactions, which allow C-H arylation of heteroarenes, enones, alkenes, and alkynes with organic dyes, such as eosin Y, as the photocatalyst. A good number of examples from different groups illustrate the broad application of the reaction in synthetic transformations. While initially only photo-Meerwein arylation-elimination processes were reported, the reaction was later extended to photo-Meerwein arylation-addition reactions giving access to the photoinduced three component synthesis of amides and esters from alkenes, aryl diazonium salts, nitriles or formamides, respectively. Other substrates with redox-active leaving groups have been explored in photocatalyzed arylation reactions, such as diaryliodonium and triarylsulfonium salts, and arylsulfonyl chlorides. We discus some examples with their scope and limitations. The scope of arylation reagents for photoredox reactions was extended to aryl halides. The challenge here is the extremely negative reduction potential of aryl halides in the initial electron transfer step compared to, e.g., aryl diazonium or diaryliodonium salts. In order to reach reduction potentials over -2.0 V vs SCE two consecutive photoinduced electron transfer steps were used. The intermediary formed colored radical

  20. Visible Light Mediated Photoredox Catalytic Arylation Reactions.

    PubMed

    Ghosh, Indrajit; Marzo, Leyre; Das, Amrita; Shaikh, Rizwan; König, Burkhard

    2016-08-16

    Introducing aryl- and heteroaryl moieties into molecular scaffolds are often key steps in the syntheses of natural products, drugs, or functional materials. A variety of cross-coupling methods have been well established, mainly using transition metal mediated reactions between prefunctionalized substrates and arenes or C-H arylations with functionalization in only one coupling partner. Although highly developed, one drawback of the established sp2-sp2 arylations is the required transition metal catalyst, often in combination with specific ligands and additives. Therefore, photoredox mediated arylation methods have been developed as alternative over the past decade. We begin our survey with visible light photo-Meerwein arylation reactions, which allow C-H arylation of heteroarenes, enones, alkenes, and alkynes with organic dyes, such as eosin Y, as the photocatalyst. A good number of examples from different groups illustrate the broad application of the reaction in synthetic transformations. While initially only photo-Meerwein arylation-elimination processes were reported, the reaction was later extended to photo-Meerwein arylation-addition reactions giving access to the photoinduced three component synthesis of amides and esters from alkenes, aryl diazonium salts, nitriles or formamides, respectively. Other substrates with redox-active leaving groups have been explored in photocatalyzed arylation reactions, such as diaryliodonium and triarylsulfonium salts, and arylsulfonyl chlorides. We discus some examples with their scope and limitations. The scope of arylation reagents for photoredox reactions was extended to aryl halides. The challenge here is the extremely negative reduction potential of aryl halides in the initial electron transfer step compared to, e.g., aryl diazonium or diaryliodonium salts. In order to reach reduction potentials over -2.0 V vs SCE two consecutive photoinduced electron transfer steps were used. The intermediary formed colored radical

  1. Temperature Modulation of a Catalytic Gas Sensor

    PubMed Central

    Brauns, Eike; Morsbach, Eva; Kunz, Sebastian; Baeumer, Marcus; Lang, Walter

    2014-01-01

    The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms) was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal. PMID:25356643

  2. Electro Catalytic Oxidation (ECO) Operation

    SciTech Connect

    Morgan Jones

    2011-03-31

    The power industry in the United States is faced with meeting many new regulations to reduce a number of air pollutants including sulfur dioxide, nitrogen oxides, fine particulate matter, and mercury. With over 1,000 power plants in the US, this is a daunting task. In some cases, traditional pollution control technologies such as wet scrubbers and SCRs are not feasible. Powerspan's Electro-Catalytic Oxidation, or ECO{reg_sign} process combines four pollution control devices into a single integrated system that can be installed after a power plant's particulate control device. Besides achieving major reductions in emissions of sulfur dioxide (SO{sub 2}), nitrogen oxides (NOx), fine particulate matter (PM2.5) and mercury (Hg), ECO produces a highly marketable fertilizer, which can help offset the operating costs of the process system. Powerspan has been operating a 50-MW ECO commercial demonstration unit (CDU) at FirstEnergy Corp.'s R.E. Burger Plant near Shadyside, Ohio, since February 2004. In addition to the CDU, a test loop has been constructed beside the CDU to demonstrate higher NOx removal rates and test various scrubber packing types and wet ESP configurations. Furthermore, Powerspan has developed the ECO{reg_sign}{sub 2} technology, a regenerative process that uses a proprietary solvent to capture CO{sub 2} from flue gas. The CO{sub 2} capture takes place after the capture of NOx, SO{sub 2}, mercury, and fine particulate matter. Once the CO{sub 2} is captured, the proprietary solution is regenerated to release CO{sub 2} in a form that is ready for geological storage or beneficial use. Pilot scale testing of ECO{sub 2} began in early 2009 at FirstEnergy's Burger Plant. The ECO{sub 2} pilot unit is designed to process a 1-MW flue gas stream and produce 20 tons of CO{sub 2} per day, achieving a 90% CO{sub 2} capture rate. The ECO{sub 2} pilot program provided the opportunity to confirm process design and cost estimates, and prepare for large scale capture and

  3. Atomic-structural synergy for catalytic CO oxidation over palladium-nickel nanoalloys.

    PubMed

    Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Joseph, Pharrah; Mayzel, Dina; Prasai, Binay; Wang, Lingyan; Engelhard, Mark; Zhong, Chuan-Jian

    2014-05-14

    Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly active and stable catalysts. However, the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium-nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of ~50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.

  4. Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium-Nickel Nanoalloys

    SciTech Connect

    Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Joseph, Pharrah; Mayzel, Dina; Prasai, Binay; Wang, Lingyan; Engelhard, Mark H.; Zhong, Chuan-Jian

    2014-05-05

    Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly-active and stable catalysts. However the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium-nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable a maximal catalytic activity at Pd:Ni ratio of ~50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.

  5. Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium-Nickel Nanoalloys

    SciTech Connect

    Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Joseph, Pharrah; Mayzel, Dina; Prasai, Binay; Wang, Lingyan; Engelhard, Mark; Zhong, Chuan-Jian

    2014-05-05

    Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly active and stable catalysts. However, the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium–nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of ~50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.

  6. Voltage-dependent motion of the catalytic region of voltage-sensing phosphatase monitored by a fluorescent amino acid

    PubMed Central

    Sakata, Souhei; Jinno, Yuka; Kawanabe, Akira; Okamura, Yasushi

    2016-01-01

    The cytoplasmic region of voltage-sensing phosphatase (VSP) derives the voltage dependence of its catalytic activity from coupling to a voltage sensor homologous to that of voltage-gated ion channels. To assess the conformational changes in the cytoplasmic region upon activation of the voltage sensor, we genetically incorporated a fluorescent unnatural amino acid, 3-(6-acetylnaphthalen-2-ylamino)-2-aminopropanoic acid (Anap), into the catalytic region of Ciona intestinalis VSP (Ci-VSP). Measurements of Anap fluorescence under voltage clamp in Xenopus oocytes revealed that the catalytic region assumes distinct conformations dependent on the degree of voltage-sensor activation. FRET analysis showed that the catalytic region remains situated beneath the plasma membrane, irrespective of the voltage level. Moreover, Anap fluorescence from a membrane-facing loop in the C2 domain showed a pattern reflecting substrate turnover. These results indicate that the voltage sensor regulates Ci-VSP catalytic activity by causing conformational changes in the entire catalytic region, without changing their distance from the plasma membrane. PMID:27330112

  7. The Direct Catalytic Asymmetric Aldol Reaction

    PubMed Central

    Brindle, Cheyenne S.

    2013-01-01

    Asymmetric aldol reactions are a powerful method for the construction of carbon-carbon bonds in an enantioselective fashion. Historically this reaction has been performed in a stoichiometric fashion to control the various aspects of chemo-, diastereo-, regio- and enantioselectivity, however, a more atom economical approach would unite high selectivity with the use of only a catalytic amount of a chiral promoter. This critical review documents the development of direct catalytic asymmetric aldol methodologies, including organocatalytic and metal-based strategies. New methods have improved the reactivity, selectivity and substrate scope of the direct aldol reaction and enabled the synthesis of complex molecular targets PMID:20419212

  8. Continuous in vitro evolution of catalytic function

    NASA Technical Reports Server (NTRS)

    Wright, M. C.; Joyce, G. F.

    1997-01-01

    A population of RNA molecules that catalyze the template-directed ligation of RNA substrates was made to evolve in a continuous manner in the test tube. A simple serial transfer procedure was used to achieve approximately 300 successive rounds of catalysis and selective amplification in 52 hours. During this time, the population size was maintained against an overall dilution of 3 x 10(298). Both the catalytic rate and amplification rate of the RNAs improved substantially as a consequence of mutations that accumulated during the evolution process. Continuous in vitro evolution makes it possible to maintain laboratory "cultures" of catalytic molecules that can be perpetuated indefinitely.

  9. Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes.

    PubMed

    Coombs, John R; Morken, James P

    2016-02-18

    Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis. PMID:26764019

  10. A premixed hydrogen/oxygen catalytic igniter

    NASA Technical Reports Server (NTRS)

    Green, James M.

    1989-01-01

    The catalytic ignition of hydrogen and oxygen propellants was studied using a premixing hydrogen/oxygen injector. The premixed injector was designed to eliminate problems associated with catalytic ignition caused by poor propellant mixing in the catalyst bed. Mixture ratio, mass flow rate, and propellant inlet temperature were varied parametrically in testing, and a pulse mode life test of the igniter was conducted. The results of the tests showed that the premixed injector eliminated flame flashback in the reactor and increased the life of the igniter significantly. The results of the experimental program and a comparison with data collected in a previous program are given.

  11. Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes.

    PubMed

    Coombs, John R; Morken, James P

    2016-02-18

    Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis.

  12. A novel aromatic carbocation-based coupling reagent for esterification and amidation reactions.

    PubMed

    Nguyen, Thanh V; Lyons, Demelza J M

    2015-02-21

    A novel tropylium-based coupling reagent has been developed to facilitate the synthesis of a series of esters, amides, lactones and peptides under mild reaction conditions. Remarkably, this reagent can be used in catalytic amounts in conjunction with a sacrificial reagent, offering a new and efficient method for nucleophilic coupling reactions of carboxylic acids.

  13. Dark coupling

    SciTech Connect

    Gavela, M.B.; Hernández, D.; Honorez, L. Lopez; Mena, O.; Rigolin, S. E-mail: d.hernandez@uam.es E-mail: omena@ific.uv.es

    2009-07-01

    The two dark sectors of the universe—dark matter and dark energy—may interact with each other. Background and linear density perturbation evolution equations are developed for a generic coupling. We then establish the general conditions necessary to obtain models free from non-adiabatic instabilities. As an application, we consider a viable universe in which the interaction strength is proportional to the dark energy density. The scenario does not exhibit ''phantom crossing'' and is free from instabilities, including early ones. A sizeable interaction strength is compatible with combined WMAP, HST, SN, LSS and H(z) data. Neutrino mass and/or cosmic curvature are allowed to be larger than in non-interacting models. Our analysis sheds light as well on unstable scenarios previously proposed.

  14. Thermoacoustic couple

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1983-10-04

    An apparatus and method for determining acoustic power density level and its direction in a fluid using a single sensor are disclosed. The preferred embodiment of the apparatus, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

  15. One-step and rapid synthesis of porous Pd nanoparticles with superior catalytic activity toward ethanol/formic acid electrooxidation

    NASA Astrophysics Data System (ADS)

    Hong, Wei; Fang, Youxing; Wang, Jin; Wang, Erkang

    2014-02-01

    Porous Pd nanoparticles are successfully prepared by a rapid, one-step, and efficient route with high yield in aqueous solution. The developed method is very simple, just by mixing sodium tetrachloropalladate, polyvinylpyrrolidone and hydroquinone and heated at 70 °C for 15 min. The structure and composition are analyzed by transmission electron microscope, selected-area electron diffraction, inductively coupled plasma optical emission spectrometer, X-ray diffraction, energy dispersive X-ray spectrum and X-ray photoelectron spectroscopy. Electrochemical catalytic measurement results prove that the as synthesized porous Pd nanoparticles exhibit superior catalytic activity towards ethanol and formic acid electrooxidation.

  16. A Bioinspired Catalytic Aerobic Oxidative C–H Functionalization of Primary Aliphatic Amines: Synthesis of 1,2-Disubstituted Benzimidazoles

    PubMed Central

    Nguyen, Khac Minh Huy; Largeron, Martine

    2015-01-01

    Aerobic oxidative C–H functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems. PMID:26206475

  17. The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers

    SciTech Connect

    Olek, Anna T.; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N.; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; Himmel, Michael E.; Bolin, Jeffrey T.; Carpita, Nicholas C.

    2014-07-10

    Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. As a result, the arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize.

  18. The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers

    DOE PAGES

    Olek, Anna T.; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N.; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; et al

    2014-07-10

    Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongatedmore » structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. As a result, the arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize.« less

  19. Critical catalytic functional groups in the mechanism of aspartate-beta-semialdehyde dehydrogenase.

    PubMed

    Blanco, Julio; Moore, Roger A; Faehnle, Christopher R; Viola, Ronald E

    2004-10-01

    Aspartate-beta-semialdehyde dehydrogenase (ASADH) catalyzes the reductive dephosphorylation of beta-aspartyl phosphate to L-aspartate-beta-semialdehyde in the aspartate biosynthetic pathway. This pathway is not found in humans or other eukaryotic organisms, yet is required for the production of threonine, isoleucine, methionine and lysine in most microorganisms. The mechanism of this enzyme has been examined through the structures of two active-site mutants of ASADH from Haemophilus influenzae. Replacement of the enzyme active-site cysteine with serine (C136S) leads to a dramatic loss of catalytic activity caused by the expected decrease in nucleophilicity, but also by a change in the orientation of the serine hydroxyl group relative to the cysteine thiolate. In contrast, in the H277N active-site mutant the introduced amide is oriented in virtually the same position as that of the histidine imidazole ring. However, a shift in the position of the bound reaction intermediate to accommodate this shorter asparagine side chain, coupled with the inability of this introduced amide to serve as a proton acceptor, results in a 100-fold decrease in the catalytic efficiency of H277N relative to the native enzyme. These mutant enzymes have the same overall fold and high structural identity to native ASADH. However, small perturbations in the positioning of essential catalytic groups or reactive intermediates have dramatic effects on catalytic efficiency. PMID:15388927

  20. Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

    PubMed

    Shim, Wang Geun; Nahm, Seung Won; Park, Hyuk Ryeol; Yun, Hyung Sun; Seo, Seong Gyu; Kim, Sang Chai

    2011-02-01

    To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

  1. The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers.

    PubMed

    Olek, Anna T; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; Himmel, Michael E; Bolin, Jeffrey T; Carpita, Nicholas C

    2014-07-01

    Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. The arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize. PMID:25012190

  2. The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers.

    PubMed

    Olek, Anna T; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; Himmel, Michael E; Bolin, Jeffrey T; Carpita, Nicholas C

    2014-07-01

    Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. The arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize.

  3. Catalytic desulfurization of industrial waste gases

    SciTech Connect

    Dupin, Th.

    1985-07-30

    Industrial waste gases containing objectionable/polluting compounds of sulfur, e.g., H/sub 2/S, SO/sub 2/ and such organosulfur derivatives as COS, CS/sub 2/ and mercaptans, are catalytically desulfurized, e.g., by Claus process, employing an improved catalyst comprising titanium dioxide and calcium, barium, strontium or magnesium sulfate.

  4. Catalytic Converters Maintain Air Quality in Mines

    NASA Technical Reports Server (NTRS)

    2014-01-01

    At Langley Research Center, engineers developed a tin-oxide based washcoat to prevent oxygen buildup in carbon dioxide lasers used to detect wind shears. Airflow Catalyst Systems Inc. of Rochester, New York, licensed the technology and then adapted the washcoat for use as a catalytic converter to treat the exhaust from diesel mining equipment.

  5. Rapid Deployment of Rich Catalytic Combustion

    SciTech Connect

    Richard S. Tuthill

    2004-06-10

    The overall objective of this research under the Turbines Program is the deployment of fuel flexible rich catalytic combustion technology into high-pressure ratio industrial gas turbines. The resulting combustion systems will provide fuel flexibility for gas turbines to burn coal derived synthesis gas or natural gas and achieve NO{sub x} emissions of 2 ppmvd or less (at 15 percent O{sub 2}), cost effectively. This advance will signify a major step towards environmentally friendly electric power generation and coal-based energy independence for the United States. Under Phase 1 of the Program, Pratt & Whitney (P&W) performed a system integration study of rich catalytic combustion in a small high-pressure ratio industrial gas turbine with a silo combustion system that is easily scalable to a larger multi-chamber gas turbine system. An implementation plan for this technology also was studied. The principal achievement of the Phase 1 effort was the sizing of the catalytic module in a manner which allowed a single reactor (rather than multiple reactors) to be used by the combustion system, a conclusion regarding the amount of air that should be allocated to the reaction zone to achieve low emissions, definition of a combustion staging strategy to achieve low emissions, and mechanical integration of a Ceramic Matrix Composite (CMC) combustor liner with the catalytic module.

  6. Process for catalytically oxidizing cycloolefins, particularly cyclohexene

    DOEpatents

    Mizuno, Noritaka; Lyon, David K.; Finke, Richard G.

    1993-01-01

    This invention is a process for catalytically oxidizing cycloolefins, particularly cyclohexenes, to form a variety of oxygenates. The catalyst used in the process is a covalently bonded iridium-heteropolyanion species. The process uses the catalyst in conjunction with a gaseous oxygen containing gas to form 2-cyclohexen-1-ol and also 2-cyclohexen-1-one.

  7. Catalytic processes for space station waste conversion

    NASA Technical Reports Server (NTRS)

    Schoonover, M. W.; Madsen, R. A.

    1986-01-01

    Catalytic techniques for processing waste products onboard space vehicles were evaluated. The goal of the study was the conversion of waste to carbon, wash water, oxygen and nitrogen. However, the ultimate goal is conversion to plant nutrients and other materials useful in closure of an ecological life support system for extended planetary missions. The resulting process studied involves hydrolysis at 250 C and 600 psia to break down and compact cellulose material, distillation at 100 C to remove water, coking at 450 C and atmospheric pressure, and catalytic oxidation at 450 to 600 C and atmospheric pressure. Tests were conducted with a model waste to characterize the hydrolysis and coking processes. An oxidizer reactor was sized based on automotive catalytic conversion experience. Products obtained from the hydrolysis and coking steps included a solid residue, gases, water condensate streams, and a volatile coker oil. Based on the data obtained, sufficient component sizing was performed to make a preliminary comparison of the catalytic technique with oxidation for processing waste for a six-man spacecraft. Wet oxidation seems to be the preferred technique from the standpoint of both component simplicity and power consumption.

  8. SELECTIVE CATALYTIC REDUCTION MERCURY FIELD SAMPLING PROJECT

    EPA Science Inventory

    The report details an investigation on the effect of selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and flue gas conditioning on the speciation and removal of mercury at power plants. If SCR and/or SNCR systems enhance mercury conversion/capture, t...

  9. Toward Facilitative Mentoring and Catalytic Interventions

    ERIC Educational Resources Information Center

    Smith, Melissa K.; Lewis, Marilyn

    2015-01-01

    In TESOL teacher mentoring, giving advice can be conceptualized as a continuum, ranging from directive to facilitative feedback. The goal, over time, is to lead toward the facilitative end of the continuum and specifically to catalytic interventions that encourage self-reflection and autonomous learning. This study begins by examining research on…

  10. Purification of reformer streams by catalytic hydrogenation

    SciTech Connect

    Polanek, P.J.; Hooper, H.M.; Mueller, J.; Walter, M.; Emmrich, G.

    1996-12-01

    Catalytic Reforming is one of the most important processes to produce high grade motor gasolines. Feedstocks are mainly gasoline and naphtha streams from the crude oil distillation boiling in the range of 212 F to 350 F. By catalytic reforming the octane number of these gasoline components is increased from 40--60 RON to 95--100 RON. Besides isomerization and dehydrocyclization reactions mainly formation of aromatics by dehydrogenation of naphthenes occur. Thus, catalytic reformers within refineries are an important source of BTX--aromatics (benzene, toluene, xylenes). Frequently, high purity aromatics are recovered from these streams using modern extractive distillation or liquid extraction processes, e.g. the Krupp-Koppers MORPHYLANE{reg_sign} process. Aromatics product specifications, notably bromine index and acid wash color, have obligated producers to utilize clay treatment to remove trace impurities of diolefins and/or olefins. The conventional clay treatment is a multiple vessel batch process which periodically requires disposal of the spent clay in a suitable environmental manner. BASF, in close cooperation with Krupp-Koppers, has developed a continuous Selective Catalytic Hydrogenation Process (SCHP) as an alternative to clay treatment which is very efficient, cost effective and environmentally compatible. In the following the main process aspects including the process scheme catalyst and operating conditions is described.

  11. Performance characterization of a hydrogen catalytic heater.

    SciTech Connect

    Johnson, Terry Alan; Kanouff, Michael P.

    2010-04-01

    This report describes the performance of a high efficiency, compact heater that uses the catalytic oxidation of hydrogen to provide heat to the GM Hydrogen Storage Demonstration System. The heater was designed to transfer up to 30 kW of heat from the catalytic reaction to a circulating heat transfer fluid. The fluid then transfers the heat to one or more of the four hydrogen storage modules that make up the Demonstration System to drive off the chemically bound hydrogen. The heater consists of three main parts: (1) the reactor, (2) the gas heat recuperator, and (3) oil and gas flow distribution manifolds. The reactor and recuperator are integrated, compact, finned-plate heat exchangers to maximize heat transfer efficiency and minimize mass and volume. Detailed, three-dimensional, multi-physics computational models were used to design and optimize the system. At full power the heater was able to catalytically combust a 10% hydrogen/air mixture flowing at over 80 cubic feet per minute and transfer 30 kW of heat to a 30 gallon per minute flow of oil over a temperature range from 100 C to 220 C. The total efficiency of the catalytic heater, defined as the heat transferred to the oil divided by the inlet hydrogen chemical energy, was characterized and methods for improvement were investigated.

  12. Novel Metal Nanomaterials and Their Catalytic Applications.

    PubMed

    Wang, Jiaqing; Gu, Hongwei

    2015-01-01

    In the rapidly developing areas of nanotechnology, nano-scale materials as heterogeneous catalysts in the synthesis of organic molecules have gotten more and more attention. In this review, we will summarize the synthesis of several new types of noble metal nanostructures (FePt@Cu nanowires, Pt@Fe₂O₃ nanowires and bimetallic Pt@Ir nanocomplexes; Pt-Au heterostructures, Au-Pt bimetallic nanocomplexes and Pt/Pd bimetallic nanodendrites; Au nanowires, CuO@Ag nanowires and a series of Pd nanocatalysts) and their new catalytic applications in our group, to establish heterogeneous catalytic system in "green" environments. Further study shows that these materials have a higher catalytic activity and selectivity than previously reported nanocrystal catalysts in organic reactions, or show a superior electro-catalytic activity for the oxidation of methanol. The whole process might have a great impact to resolve the energy crisis and the environmental crisis that were caused by traditional chemical engineering. Furthermore, we hope that this article will provide a reference point for the noble metal nanomaterials' development that leads to new opportunities in nanocatalysis. PMID:26393550

  13. SELECTIVE CATALYTIC REDUCTION MERCURY FIELD SAMPLING PROJECT

    EPA Science Inventory

    A lack of data still exists as to the effect of selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and flue gas conditioning on the speciation and removal of mercury (Hg) at power plants. This project investigates the impact that SCR, SNCR, and flue gas...

  14. Final Technical Report [Development of Catalytic Alkylation and Fluoroalkylation Methods

    SciTech Connect

    Vicic, David A.

    2014-05-01

    In the early stages of this DOE-funded research project, we sought to prepare and study a well-defined nickel-alkyl complex containing tridentate nitrogen donor ligands. We found that reaction of (TMEDA)NiMe2 (1) with terpyridine ligand cleanly led to the formation of (terpyridyl)NiMe (2), which we also determined to be an active alkylation catalyst. The thermal stability of 2 was unlike that seen for any of the active pybox ligands, and enabled a number of key studies on alkyl transfer reactions to be performed, providing new insights into the mechanism of nickel-mediated alkyl-alkyl cross-coupling reactions. In addition to the mechanistic studies, we showed that the terpyridyl nickel compounds can catalytically cross-couple alkyl iodides in yields up to 98% and bromides in yields up to 46 %. The yields for the bromides can be increased up to 67 % when the new palladium catalyst [(tpy’)Pd-Ph]I is used. The best route to the targeted [(tpy)NiBr] (1) was found to involve the comproportionation reaction of [(dme)NiBr{sub 2}] and [Ni(COD){sub 2}] in the presence of two equivalents of terpyridine. This reaction was driven to high yields of product formation (72 % isolated) by the precipitation of 1 from THF solvent.

  15. Highly Selective Formation of n-Butanol from Ethanol through the Guerbet Process: A Tandem Catalytic Approach.

    PubMed

    Chakraborty, Sumit; Piszel, Paige E; Hayes, Cassandra E; Baker, R Tom; Jones, William D

    2015-11-18

    A highly selective (>99%) tandem catalytic system for the conversion of ethanol (up to 37%) to n-butanol, through the Guerbet process, has been developed using a bifunctional iridium catalyst coupled with bulky nickel or copper hydroxides. These sterically crowded nickel and copper hydroxides catalyze the key aldol coupling reaction of acetaldehyde to exclusively yield the C4 coupling product, crotonaldehyde. Iridium-mediated dehydrogenation of ethanol to acetaldehyde has led to the development of an ethanol-to-butanol process operated at a lower temperature. PMID:26526779

  16. Architecture and function of metallopeptidase catalytic domains

    PubMed Central

    Cerdà-Costa, Núria; Gomis-Rüth, Francesc Xavier

    2014-01-01

    The cleavage of peptide bonds by metallopeptidases (MPs) is essential for life. These ubiquitous enzymes participate in all major physiological processes, and so their deregulation leads to diseases ranging from cancer and metastasis, inflammation, and microbial infection to neurological insults and cardiovascular disorders. MPs cleave their substrates without a covalent intermediate in a single-step reaction involving a solvent molecule, a general base/acid, and a mono-or dinuclear catalytic metal site. Most monometallic MPs comprise a short metal-binding motif (HEXXH), which includes two metal-binding histidines and a general base/acid glutamate, and they are grouped into the zincin tribe of MPs. The latter divides mainly into the gluzincin and metzincin clans. Metzincins consist of globular ∼130–270-residue catalytic domains, which are usually preceded by N-terminal pro-segments, typically required for folding and latency maintenance. The catalytic domains are often followed by C-terminal domains for substrate recognition and other protein–protein interactions, anchoring to membranes, oligomerization, and compartmentalization. Metzincin catalytic domains consist of a structurally conserved N-terminal subdomain spanning a five-stranded β-sheet, a backing helix, and an active-site helix. The latter contains most of the metal-binding motif, which is here characteristically extended to HEXXHXXGXX(H,D). Downstream C-terminal subdomains are generally shorter, differ more among metzincins, and mainly share a conserved loop—the Met-turn—and a C-terminal helix. The accumulated structural data from more than 300 deposited structures of the 12 currently characterized metzincin families reviewed here provide detailed knowledge of the molecular features of their catalytic domains, help in our understanding of their working mechanisms, and form the basis for the design of novel drugs. PMID:24596965

  17. Evolution of catalytic RNA in the laboratory

    NASA Technical Reports Server (NTRS)

    Joyce, Gerald F.

    1992-01-01

    We are interested in the biochemistry of existing RNA enzymes and in the development of RNA enzymes with novel catalytic function. The focal point of our research program has been the design and operation of a laboratory system for the controlled evolution of catalytic RNA. This system serves as working model of RNA-based life and can be used to explore the catalytic potential of RNA. Evolution requires the integration of three chemical processes: amplification, mutation, and selection. Amplification results in additional copies of the genetic material. Mutation operates at the level of genotype to introduce variability, this variability in turn being expressed as a range of phenotypes. Selection operates at the level of phenotype to reduce variability by excluding those individuals that do not conform to the prevailing fitness criteria. These three processes must be linked so that only the selected individuals are amplified, subject to mutational error, to produce a progeny distribution of mutant individuals. We devised techniques for the amplification, mutation, and selection of catalytic RNA, all of which can be performed rapidly in vitro within a single reaction vessel. We integrated these techniques in such a way that they can be performed iteratively and routinely. This allowed us to conduct evolution experiments in response to artificially-imposed selection constraints. Our objective was to develop novel RNA enzymes by altering the selection constraints in a controlled manner. In this way we were able to expand the catalytic repertoire of RNA. Our long-range objective is to develop an RNA enzyme with RNA replicase activity. If such an enzyme had the ability to produce additional copies of itself, then RNA evolution would operate autonomously and the origin of life will have been realized in the laboratory.

  18. Using catalytic atom maps to predict the catalytic functions present in enzyme active sites.

    PubMed

    Nosrati, Geoffrey R; Houk, K N

    2012-09-18

    Catalytic atom maps (CAMs) are minimal models of enzyme active sites. The structures in the Protein Data Bank (PDB) were examined to determine if proteins with CAM-like geometries in their active sites all share the same catalytic function. We combined the CAM-based search protocol with a filter based on the weighted contact number (WCN) of the catalytic residues, a measure of the "crowdedness" of the microenvironment around a protein residue. Using this technique, a CAM based on the Ser-His-Asp catalytic triad of trypsin was able to correctly identify catalytic triads in other enzymes within 0.5 Å rmsd of the CAM with 96% accuracy. A CAM based on the Cys-Arg-(Asp/Glu) active site residues from the tyrosine phosphatase active site achieved 89% accuracy in identifying this type of catalytic functionality. Both of these CAMs were able to identify active sites across different fold types. Finally, the PDB was searched to locate proteins with catalytic functionality similar to that present in the active site of orotidine 5'-monophosphate decarboxylase (ODCase), whose mechanism is not known with certainty. A CAM, based on the conserved Lys-Asp-Lys-Asp tetrad in the ODCase active site, was used to search the PDB for enzymes with similar active sites. The ODCase active site has a geometry similar to that of Schiff base-forming Class I aldolases, with lowest aldolase rmsd to the ODCase CAM at 0.48 Å. The similarity between this CAM and the aldolase active site suggests that ODCase has the correct catalytic functionality present in its active site for the generation of a nucleophilic lysine. PMID:22909276

  19. Retrofitting gear couplings with diaphragm couplings

    SciTech Connect

    Mancuso, J.R. )

    1988-10-01

    Retrofitting a coupling should not be an afterthought when upgrading a system. Couplings are an integral part of a drive train and should be a major consideration. This article discusses guidelines that should be used when replacing gear couplings with diaphragm couplings. Reviewed are the coupling selection process: how and to what extent the desired diaphragm couplings should be matched to the gear coupling. Also discussed are the details of coupling modification that can be made to accommodate system performance. Included are how changes in materials, configuration and design can help tune a diaphragm coupling to meet the characteristics of the previous gear couplings. The article also discusses the retrofit process for a specific syngas train at International Minerals and Chemical Corp., Sterlington, La.

  20. Catalytic Synthesis of Oxygenates: Mechanisms, Catalysts and Controlling Characteristics

    SciTech Connect

    Klier, Kamil; Herman, Richard G

    2005-11-30

    This research focused on catalytic synthesis of unsymmetrical ethers as a part of a larger program involving oxygenated products in general, including alcohols, ethers, esters, carboxylic acids and their derivatives that link together environmentally compliant fuels, monomers, and high-value chemicals. The catalysts studied here were solid acids possessing strong Brnsted acid functionalities. The design of these catalysts involved anchoring the acid groups onto inorganic oxides, e.g. surface-grafted acid groups on zirconia, and a new class of mesoporous solid acids, i.e. propylsulfonic acid-derivatized SBA-15. The former catalysts consisted of a high surface concentration of sulfate groups on stable zirconia catalysts. The latter catalyst consists of high surface area, large pore propylsulfonic acid-derivatized silicas, specifically SBA-15. In both cases, the catalyst design and synthesis yielded high concentrations of acid sites in close proximity to one another. These materials have been well-characterization in terms of physical and chemical properties, as well as in regard to surface and bulk characteristics. Both types of catalysts were shown to exhibit high catalytic performance with respect to both activity and selectivity for the bifunctional coupling of alcohols to form ethers, which proceeds via an efficient SN2 reaction mechanism on the proximal acid sites. This commonality of the dual-site SN2 reaction mechanism over acid catalysts provides for maximum reaction rates and control of selectivity by reaction conditions, i.e. pressure, temperature, and reactant concentrations. This research provides the scientific groundwork for synthesis of ethers for energy applications. The synthesized environmentally acceptable ethers, in part derived from natural gas via alcohol intermediates, exhibit high cetane properties, e.g. methylisobutylether with cetane No. of 53 and dimethylether with cetane No. of 55-60, or high octane properties, e.g. diisopropylether with

  1. N-heterocyclic carbene organocatalytic reductive β,β-coupling reactions of nitroalkenes via radical intermediates.

    PubMed

    Du, Yu; Wang, Yuhuang; Li, Xin; Shao, Yaling; Li, Guohui; Webster, Richard D; Chi, Yonggui Robin

    2014-11-01

    An unprecedented N-heterocyclic carbene catalytic reductive β,β-carbon coupling of α,β-nitroalkenes, by using an organic substrate to mimic the one-electron oxidation role of the pyruvate ferredoxin oxidoreductase (PFOR) in living systems, has been developed. The reaction goes through a radical anion intermediate generated under a catalytic redox process. For the first time, the presence of radical anion intermediate in NHC organocatalysis is observed and clearly verified. PMID:25343564

  2. Palladium Nanoparticle-Loaded Cellulose Paper: A Highly Efficient, Robust, and Recyclable Self-Assembled Composite Catalytic System.

    PubMed

    Zheng, Guangchao; Kaefer, Katharina; Mourdikoudis, Stefanos; Polavarapu, Lakshminarayana; Vaz, Belén; Cartmell, Samantha E; Bouleghlimat, Azzedine; Buurma, Niklaas J; Yate, Luis; de Lera, Ángel R; Liz-Marzán, Luis M; Pastoriza-Santos, Isabel; Pérez-Juste, Jorge

    2015-01-15

    We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent. The prepared Pd NP-loaded paper substrates were tested for several model reactions such as the oxidative homocoupling of arylboronic acids, the Suzuki cross-coupling reaction, and nitro-to-amine reduction, and they display efficient catalytic activity and excellent recyclability and reusability. This approach of using NP-loaded paper substrates as reusable catalysts is expected to open doors for new types of catalytic support for practical applications. PMID:26263455

  3. Main problems in the theory of modeling of catalytic processes

    SciTech Connect

    Pisarenko, V.N.

    1994-09-01

    This paper formulates the main problems in the theory of modeling of catalytic processes yet to be solved and describes the stages of modeling. Fundamental problems of model construction for the physico-chemical phenomena and processes taking place in a catalytic reactor are considered. New methods for determining the mechanism of a catalytic reaction and selecting a kinetic model for it are analyzed. The use of the results of specially controlled experiments for the construction of models of a catalyst grain and a catalytic reactor is discussed. Algorithms are presented for determining the muliplicity of stationary states in the operation of a catalyst grain and a catalytic reactor.

  4. Synthetic and Thermodynamic Investigations of Ancillary Ligand Influence on Catalytic Organometallic Systems. Final Report

    SciTech Connect

    Nolan, Steven

    2003-03-20

    During the grant period we have been involved in synthesizing and experimentally determining solution enthalpy values associated with partially fluorinated ligands. This has lead to the publication of manuscripts dealing with synthetic, calorimetric and catalytic behavior of partially fluorinated ligands. The collaboration with Los Alamos researchers has lead to the publication of catalytic results in sc CO{sub 2} which have proven very interesting. Furthermore, we have also examined ligands that behave as phosphine mimics. The N-heterocyclic carbenes have been explored as alternatives for tertiary phosphines and have resulted in the design and construction of efficient palladium and nickel system capable of performing C-C and C-N cross coupling reactions. The initial studies in this areas were made possible by exploratory work conducted under the DOE/EPSCoR grant.

  5. Catalytic reduction of CN-, CO, and CO2 by nitrogenase cofactors in lanthanide-driven reactions.

    PubMed

    Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W

    2015-01-19

    Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN(-)), carbon monoxide (CO), and carbon dioxide (CO2) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI2) and 2,6-lutidinium triflate (Lut-H) are employed as a reductant and a proton source, respectively. Driven by SmI2, the cofactors catalytically reduce CN(-) or CO to C1-C4 hydrocarbons, and CO2 to CO and C1-C3 hydrocarbons. The C-C coupling from CO2 indicates a unique Fischer-Tropsch-like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN(-), CO, and CO2 by isolated cofactors suggests the possibility to develop nitrogenase-based electrocatalysts for the production of hydrocarbons from these carbon-containing compounds.

  6. Imaging Isolated Gold Atom Catalytic Sites in Zeolite NaY

    SciTech Connect

    Lu, Jing; Aydin, C.; Browning, Nigel D.; Gates, Bruce C.

    2012-06-11

    Gold, the most stable metallic element, attracted wide attention as a catalyst only after the discovery that gold nanoclusters on oxide supports are highly active and selective for reactions including numerous oxidation,[1–8] hydrogenation,[9–11] hydroamination,[12, 13] ring expansion,[14, 15] and coupling[16, 17] reactions. The catalytic properties of supported gold strongly dependent on the gold–support interactions and the size of the active species, which must be small—typically clusters with diameters of the order of 1 nm.[18–20] Frequent discoveries of new gold-catalyzed reactions are leading the science; understanding has been slow to emerge.[21] Major challenges are to identify the catalytically active species and to characterize gold–support interactions.

  7. Synthesis and characterization of vanadium nanoparticles on activated carbon and their catalytic activity in thiophene hydrodesulphurization

    NASA Astrophysics Data System (ADS)

    Pinto, Susana; D'Ornelas, Lindora; Betancourt, Paulino

    2008-06-01

    Vanadium nanoparticles (˜7 nm) stabilized on activated carbon were synthesized by the reduction of VCl 3·3THF with K[BEt 3H]. This material was characterized by inductive coupled plasma-atomic emission spectroscopy (ICP-AES), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses. The catalytic performance of the carbon-supported vanadium was studied using thiophene hydrodesulfurization (HDS) as model reaction at 300 °C and P = 1 atm. The catalytic activity of the vanadium carbide phase on the activated carbon carrier was more significant than that of the reference catalysts, alumina supported NiMoS. The method proposed for the synthesis of such a catalyst led to an excellent performance of the HDS process.

  8. Engineering a hyper-catalytic enzyme by photo-activated conformation modulation

    SciTech Connect

    Agarwal, Pratul K

    2012-01-01

    Enzyme engineering for improved catalysis has wide implications. We describe a novel chemical modification of Candida antarctica lipase B that allows modulation of the enzyme conformation to promote catalysis. Computational modeling was used to identify dynamical enzyme regions that impact the catalytic mechanism. Surface loop regions located distal to active site but showing dynamical coupling to the reaction were connected by a chemical bridge between Lys136 and Pro192, containing a derivative of azobenzene. The conformational modulation of the enzyme was achieved using two sources of light that alternated the azobenzene moiety in cis and trans conformations. Computational model predicted that mechanical energy from the conformational fluctuations facilitate the reaction in the active-site. The results were consistent with predictions as the activity of the engineered enzyme was found to be enhanced with photoactivation. Preliminary estimations indicate that the engineered enzyme achieved 8-52 fold better catalytic activity than the unmodulated enzyme.

  9. Structure, microstructure, and size dependent catalytic properties of nanostructured ruthenium dioxide

    SciTech Connect

    Nowakowski, Pawel; Dallas, Jean-Pierre; Villain, Sylvie; Kopia, Agnieszka; Gavarri, Jean-Raymond

    2008-05-15

    Nanostructured powders of ruthenium dioxide RuO{sub 2} were synthesized via a sol gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO{sub 2} nanopowders were characterized by X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Rietveld refinement of mean crystal structure was performed on RuO{sub 2} nanopowders and crystallized standard RuO{sub 2} sample. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range of 4-10 nm, with a minimum of crystallite dimension for pH=1.5. A good agreement between crystallite sizes calculated from Williamson Hall approach of X-ray data and from direct TEM observations was obtained. The tetragonal crystal cell parameter (a) and cell volumes of nanostructured samples were characterized by values greater than the values of standard RuO{sub 2} sample. In addition, the [Ru-O{sub 6}] oxygen octahedrons of rutile structure also depended on crystal size. Catalytic conversion of methane by these RuO{sub 2} nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO{sub 2}) was maximum for sample prepared at pH=1.5, and mainly correlated to crystallite dimensions. No significant catalytic effect was observed from sintered RuO{sub 2} samples. - Graphical abstract: Nanosized crystals of RuO{sub 2} prepared by sol gel route, at pH=0.4 and 1.5. Mean size values , respectively, 10 and 8 nm.

  10. Molecular basis of the general base catalysis of an α/β-hydrolase catalytic triad.

    PubMed

    Sun, Yueru; Yin, Shuhui; Feng, Yitao; Li, Jie; Zhou, Jiahai; Liu, Changdong; Zhu, Guang; Guo, Zhihong

    2014-05-30

    The serine-histidine-aspartate triad is well known for its covalent, nucleophilic catalysis in a diverse array of enzymatic transformations. Here we show that its nucleophilicity is shielded and its catalytic role is limited to being a specific general base by an open-closed conformational change in the catalysis of (1R,6R)-2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase (or MenH), a typical α/β-hydrolase fold enzyme in the vitamin K biosynthetic pathway. This enzyme is found to adopt an open conformation without a functional triad in its ligand-free form and a closed conformation with a fully functional catalytic triad in the presence of its reaction product. The open-to-closed conformational transition involves movement of half of the α-helical cap domain, which causes extensive structural changes in the α/β-domain and forces the side chain of the triad histidine to adopt an energetically disfavored gauche conformation to form the functional triad. NMR analysis shows that the inactive open conformation without a triad prevails in ligand-free solution and is converted to the closed conformation with a properly formed triad by the reaction product. Mutation of the residues crucial to this open-closed transition either greatly decreases or completely eliminates the enzyme activity, supporting an important catalytic role for the structural change. These findings suggest that the open-closed conformational change tightly couples formation of the catalytic triad to substrate binding to enhance the substrate specificities and simultaneously shield the nucleophilicity of the triad, thus allowing it to expand its catalytic power beyond the nucleophilic catalysis.

  11. Method and apparatus for a catalytic firebox reactor

    DOEpatents

    Smith, Lance L.; Etemad, Shahrokh; Ulkarim, Hasan; Castaldi, Marco J.; Pfefferle, William C.

    2001-01-01

    A catalytic firebox reactor employing an exothermic catalytic reaction channel and multiple cooling conduits for creating a partially reacted fuel/oxidant mixture. An oxidation catalyst is deposited on the walls forming the boundary between the multiple cooling conduits and the exothermic catalytic reaction channel, on the side of the walls facing the exothermic catalytic reaction channel. This configuration allows the oxidation catalyst to be backside cooled by any fluid passing through the cooling conduits. The heat of reaction is added to both the fluid in the exothermic catalytic reaction channel and the fluid passing through the cooling conduits. After discharge of the fluids from the exothermic catalytic reaction channel, the fluids mix to create a single combined flow. A further innovation in the reactor incorporates geometric changes in the exothermic catalytic reaction channel to provide streamwise variation of the velocity of the fluids in the reactor.

  12. Catalytic treatment of air-stripping effluents

    SciTech Connect

    Kosusko, M.; Mullins, M.E.; Rogers, T.N.; Ramanathan, K.

    1987-12-01

    The paper reviews the applicability of catalytic oxidation to control ground-water air-stripping gaseous effluents with emphasis on system designs and case histories. The contaminants and catalyst poisons encountered in stripping operations are also reviewed. Vapor-phase carbon adsorption and thermal incineration, the treatment methods that have been applied most often, have some disadvantages: adsorption merely transfers the contaminant to a solid phase, which in turn requires disposal or regeneration; and thermal incineration may be expensive, since it requires a substantial energy input to destroy dilute gas-phase contaminants. A new alternative is appearing in the form of catalytic oxidation. Like thermal incineration, it is an ultimate disposal method, but the energy costs are lower.

  13. Catalytic combustion of coal-derived liquids

    NASA Technical Reports Server (NTRS)

    Bulzan, D. L.; Tacina, R. R.

    1981-01-01

    A noble metal catalytic reactor was tested with three grades of SRC 2 coal derived liquids, naphtha, middle distillate, and a blend of three parts middle distillate to one part heavy distillate. A petroleum derived number 2 diesel fuel was also tested to provide a direct comparison. The catalytic reactor was tested at inlet temperatures from 600 to 800 K, reference velocities from 10 to 20 m/s, lean fuel air ratios, and a pressure of 3 x 10 to the 5th power Pa. Compared to the diesel, the naphtha gave slightly better combustion efficiency, the middle distillate was almost identical, and the middle heavy blend was slightly poorer. The coal derived liquid fuels contained from 0.58 to 0.95 percent nitrogen by weight. Conversion of fuel nitrogen to NOx was approximately 75 percent for all three grades of the coal derived liquids.

  14. Catalytic, hollow, refractory spheres, conversions with them

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1989-01-01

    Improved, heterogeneous, refractory catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitable formed of a shell (12) of refractory such as alumina having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be itself catalytic or a catalytically active material coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  15. In vitro selection of catalytic RNAs

    NASA Technical Reports Server (NTRS)

    Chapman, K. B.; Szostak, J. W.

    1994-01-01

    In vitro selection techniques are poised to allow a rapid expansion of the study of catalysis by RNA enzymes (ribozymes). This truly molecular version of genetics has already been applied to the study of the structures of known ribozymes and to the tailoring of their catalytic activity to meet specific requirements of substrate specificity or reaction conditions. During the past year, in vitro selection has been successfully used to isolate novel RNA catalysts from random sequence pools.

  16. Catalytic extraction processing of contaminated scrap metal

    SciTech Connect

    Griffin, T.P.; Johnston, J.E.; Payea, B.M.; Zeitoon, B.M.

    1995-12-01

    Molten Metal Technology was awarded a contract to demonstrate the applicability of the Catalytic Extraction Process, a proprietary process that could be applied to US DOE`s inventory of low level mixed waste. This paper is a description of that technology, and included within this document are discussions of: (1) Program objectives, (2) Overall technology review, (3) Organic feed conversion to synthetic gas, (4) Metal, halogen, and transuranic recovery, (5) Demonstrations, (6) Design of the prototype facility, and (7) Results.

  17. Control of a catalytic fluid cracker

    SciTech Connect

    Arbel, A.; Huang, Z.; Rinard, I.; Shinnar, R.

    1993-12-13

    Control offers an important tool for savings in refineries, mainly by integration of process models into on-line control. This paper is part of a research effort to better understand problems of partial control; control of a Fluid Catalytic Cracker (FCC) is used as example. Goal is to understand better the control problems of an FCC in context of model based control of a refinery, and to understand the general problem of designing partial control systems.

  18. Catalytic fast pyrolysis of lignocellulosic biomass

    SciTech Connect

    Liu, Changjun; Wang, Huamin; Karim, Ayman M.; Sun, Junming; Wang, Yong

    2014-11-21

    Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy Q3 carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel—bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating values, high corrosiveness, high viscosity, and instability; they also greatly Q4 limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality.

  19. Catalytic fast pyrolysis of lignocellulosic biomass.

    PubMed

    Liu, Changjun; Wang, Huamin; Karim, Ayman M; Sun, Junming; Wang, Yong

    2014-11-21

    Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel-bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating value, high corrosiveness, high viscosity, and instability; they also greatly limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality.

  20. Preface: Challenges for Catalytic Exhaust Aftertreatment

    SciTech Connect

    Nova, Isabella; Epling, Bill; Peden, Charles HF

    2014-03-31

    This special issue of Catalysis Today continues the tradition established since the 18th NAM in Cancun, 2003, of publishing the highlights coming from these catalytic after-treatment technologies sessions, where this volume contains 18 papers based on oral and poster presentations of the 23rd NAM, 2013. The guest editors would like to thank all of the catalyst scientists and engineers who presented in the "Emission control" sessions, and especially the authors who contributed to this special issue of Catalysis Today.

  1. Catalytic anomeric aminoalkynylation of unprotected aldoses.

    PubMed

    Kimura, Yasuaki; Ito, Soichi; Shimizu, Yohei; Kanai, Motomu

    2013-08-16

    A copper(I)-catalyzed anomeric aminoalkynylation reaction of unprotected aldoses was realized. Use of an electron-deficient phosphine ligand, boric acid to stabilize the iminium intermediate, and a protic additive (IPA) to presumably enhance reversible carbohydrate-boron complexation were all essential for efficient conversion. The reaction proceeded well even with a natural disaccharide substrate, suggesting that the developed catalytic reaction could be useful for the synthesis of glycoconjugates with minimum use of protecting groups. PMID:23901780

  2. Catalytic Asymmetric Synthesis of Phosphine Boronates.

    PubMed

    Hornillos, Valentín; Vila, Carlos; Otten, Edwin; Feringa, Ben L

    2015-06-26

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds. PMID:25950871

  3. Catalytic fast pyrolysis of lignocellulosic biomass.

    PubMed

    Liu, Changjun; Wang, Huamin; Karim, Ayman M; Sun, Junming; Wang, Yong

    2014-11-21

    Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel-bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating value, high corrosiveness, high viscosity, and instability; they also greatly limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality. PMID:24801125

  4. Catalytic pyrolysis of olive mill wastewater sludge

    NASA Astrophysics Data System (ADS)

    Abdellaoui, Hamza

    From 2008 to 2013, an average of 2,821.4 kilotons/year of olive oil were produced around the world. The waste product of the olive mill industry consists of solid residue (pomace) and wastewater (OMW). Annually, around 30 million m3 of OMW are produced in the Mediterranean area, 700,000 m3 year?1 in Tunisia alone. OMW is an aqueous effluent characterized by an offensive smell and high organic matter content, including high molecular weight phenolic compounds and long-chain fatty acids. These compounds are highly toxic to micro-organisms and plants, which makes the OMW a serious threat to the environment if not managed properly. The OMW is disposed of in open air evaporation ponds. After evaporation of most of the water, OMWS is left in the bottom of the ponds. In this thesis, the effort has been made to evaluate the catalytic pyrolysis process as a technology to valorize the OMWS. The first section of this research showed that 41.12 wt. % of the OMWS is mostly lipids, which are a good source of energy. The second section proved that catalytic pyrolysis of the OMWS over red mud and HZSM-5 can produce green diesel, and 450 °C is the optimal reaction temperature to maximize the organic yields. The last section revealed that the HSF was behind the good fuel-like properties of the OMWS catalytic oils, whereas the SR hindered the bio-oil yields and quality.

  5. A revolution in micropower : the catalytic nanodiode.

    SciTech Connect

    Cross, Karen Charlene; Heller, Edwin J.; Figiel, Jeffrey James; Coker, Eric Nicholas; Creighton, James Randall; Koleske, Daniel David; Bogart, Katherine Huderle Andersen; Coltrin, Michael Elliott; Pawlowski, Roger Patrick; Baucom, Kevin C.

    2010-11-01

    Our ability to field useful, nano-enabled microsystems that capitalize on recent advances in sensor technology is severely limited by the energy density of available power sources. The catalytic nanodiode (reported by Somorjai's group at Berkeley in 2005) was potentially an alternative revolutionary source of micropower. Their first reports claimed that a sizable fraction of the chemical energy may be harvested via hot electrons (a 'chemicurrent') that are created by the catalytic chemical reaction. We fabricated and tested Pt/GaN nanodiodes, which eventually produced currents up to several microamps. Our best reaction yields (electrons/CO{sub 2}) were on the order of 10{sup -3}; well below the 75% values first reported by Somorjai (we note they have also been unable to reproduce their early results). Over the course of this Project we have determined that the whole concept of 'chemicurrent', in fact, may be an illusion. Our results conclusively demonstrate that the current measured from our nanodiodes is derived from a thermoelectric voltage; we have found no credible evidence for true chemicurrent. Unfortunately this means that the catalytic nanodiode has no future as a micropower source.

  6. Kinetic modelling of heterogeneous catalytic systems

    NASA Astrophysics Data System (ADS)

    Stamatakis, Michail

    2015-01-01

    The importance of heterogeneous catalysis in modern life is evidenced by the fact that numerous products and technologies routinely used nowadays involve catalysts in their synthesis or function. The discovery of catalytic materials is, however, a non-trivial procedure, requiring tedious trial-and-error experimentation. First-principles-based kinetic modelling methods have recently emerged as a promising way to understand catalytic function and aid in materials discovery. In particular, kinetic Monte Carlo (KMC) simulation is increasingly becoming more popular, as it can integrate several sources of complexity encountered in catalytic systems, and has already been used to successfully unravel the underlying physics of several systems of interest. After a short discussion of the different scales involved in catalysis, we summarize the theory behind KMC simulation, and present the latest KMC computational implementations in the field. Early achievements that transformed the way we think about catalysts are subsequently reviewed in connection to latest studies of realistic systems, in an attempt to highlight how the field has evolved over the last few decades. Present challenges and future directions and opportunities in computational catalysis are finally discussed.

  7. Vapor-Driven Propulsion of Catalytic Micromotors.

    PubMed

    Dong, Renfeng; Li, Jinxing; Rozen, Isaac; Ezhilan, Barath; Xu, Tailin; Christianson, Caleb; Gao, Wei; Saintillan, David; Ren, Biye; Wang, Joseph

    2015-08-18

    Chemically-powered micromotors offer exciting opportunities in diverse fields, including therapeutic delivery, environmental remediation, and nanoscale manufacturing. However, these nanovehicles require direct addition of high concentration of chemical fuel to the motor solution for their propulsion. We report the efficient vapor-powered propulsion of catalytic micromotors without direct addition of fuel to the micromotor solution. Diffusion of hydrazine vapor from the surrounding atmosphere into the sample solution is instead used to trigger rapid movement of iridium-gold Janus microsphere motors. Such operation creates a new type of remotely-triggered and powered catalytic micro/nanomotors that are responsive to their surrounding environment. This new propulsion mechanism is accompanied by unique phenomena, such as the distinct off-on response to the presence of fuel in the surrounding atmosphere, and spatio-temporal dependence of the motor speed borne out of the concentration gradient evolution within the motor solution. The relationship between the motor speed and the variables affecting the fuel concentration distribution is examined using a theoretical model for hydrazine transport, which is in turn used to explain the observed phenomena. The vapor-powered catalytic micro/nanomotors offer new opportunities in gas sensing, threat detection, and environmental monitoring, and open the door for a new class of environmentally-triggered micromotors.

  8. Demonstration of catalytic combustion with residual fuel

    NASA Technical Reports Server (NTRS)

    Dodds, W. J.; Ekstedt, E. E.

    1981-01-01

    An experimental program was conducted to demonstrate catalytic combustion of a residual fuel oil. Three catalytic reactors, including a baseline configuration and two backup configurations based on baseline test results, were operated on No. 6 fuel oil. All reactors were multielement configurations consisting of ceramic honeycomb catalyzed with palladium on stabilized alumina. Stable operation on residual oil was demonstrated with the baseline configuration at a reactor inlet temperature of about 825 K (1025 F). At low inlet temperature, operation was precluded by apparent plugging of the catalytic reactor with residual oil. Reduced plugging tendency was demonstrated in the backup reactors by increasing the size of the catalyst channels at the reactor inlet, but plugging still occurred at inlet temperature below 725 K (845 F). Operation at the original design inlet temperature of 589 K (600 F) could not be demonstrated. Combustion efficiency above 99.5% was obtained with less than 5% reactor pressure drop. Thermally formed NO sub x levels were very low (less than 0.5 g NO2/kg fuel) but nearly 100% conversion of fuel-bound nitrogen to NO sub x was observed.

  9. Highly sensitive catalytic spectrophotometric determination of ruthenium

    NASA Astrophysics Data System (ADS)

    Naik, Radhey M.; Srivastava, Abhishek; Prasad, Surendra

    2008-01-01

    A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of L-phenylalanine ( L-Pheala) by KMnO 4 in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526 nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (Δ At) versus added Ru(III) amounts in the range of 0.101-2.526 ng ml -1 is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5 min is 0.08 ng ml -1, and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.

  10. IFP solutions for revamping catalytic reforming units

    SciTech Connect

    Gendler, J.L.; Domergue, B.; Mank, L.

    1996-12-01

    The decision-making process for the refiner considering a revamp of a catalytic reforming unit comprises many factors. These may be grouped in two broad areas: technical and economic. This paper presents the results of a study performed by IFP that illustrates catalytic reforming unit revamp options. Three IFP processes are described and operating conditions, expected yields, and economic data are presented. The following options are discussed: base case Conventional, fixed-bed, semi-regenerative catalytic reformer; Case 1--revamp using IFP Dualforming technology; Case 2--revamp using IFP Dualforming Plus technology; and Case 3--revamp to IFP Octanizing technology. The study illustrates various options for the refiner to balance unit performance improvements with equipment, site, and economic constraints. The study was performed assuming design feedrate of 98.2 tons/hour (20,000 BPSD) in all cases. Because of the increased need for octane in many refineries, the study assumed that operating severity was set at a design value of 100 research octane number clear (RON). In all of the cases in this study, it was assumed that the existing recycle compressor was reused. Operating pressure differences between the cases is discussed separately. Also, in all cases, a booster compressor was included in order to return export hydrogen pressure to that of the conventional unit.

  11. Vapor-Driven Propulsion of Catalytic Micromotors

    PubMed Central

    Dong, Renfeng; Li, Jinxing; Rozen, Isaac; Ezhilan, Barath; Xu, Tailin; Christianson, Caleb; Gao, Wei; Saintillan, David; Ren, Biye; Wang, Joseph

    2015-01-01

    Chemically-powered micromotors offer exciting opportunities in diverse fields, including therapeutic delivery, environmental remediation, and nanoscale manufacturing. However, these nanovehicles require direct addition of high concentration of chemical fuel to the motor solution for their propulsion. We report the efficient vapor-powered propulsion of catalytic micromotors without direct addition of fuel to the micromotor solution. Diffusion of hydrazine vapor from the surrounding atmosphere into the sample solution is instead used to trigger rapid movement of iridium-gold Janus microsphere motors. Such operation creates a new type of remotely-triggered and powered catalytic micro/nanomotors that are responsive to their surrounding environment. This new propulsion mechanism is accompanied by unique phenomena, such as the distinct off-on response to the presence of fuel in the surrounding atmosphere, and spatio-temporal dependence of the motor speed borne out of the concentration gradient evolution within the motor solution. The relationship between the motor speed and the variables affecting the fuel concentration distribution is examined using a theoretical model for hydrazine transport, which is in turn used to explain the observed phenomena. The vapor-powered catalytic micro/nanomotors offer new opportunities in gas sensing, threat detection, and environmental monitoring, and open the door for a new class of environmentally-triggered micromotors. PMID:26285032

  12. Turning goals into results: the power of catalytic mechanisms.

    PubMed

    Collins, J

    1999-01-01

    Most executives have a big, hairy, audacious goal. They write vision statements, formalize procedures, and develop complicated incentive programs--all in pursuit of that goal. In other words, with the best of intentions, they install layers of stultifying bureaucracy. But it doesn't have to be that way. In this article, Jim Collins introduces the catalytic mechanism, a simple yet powerful managerial tool that helps translate lofty aspirations into concrete reality. Catalytic mechanisms are the crucial link between objectives and performance; they are a galvanizing, nonbureaucratic means to turn one into the other. What's the difference between catalytic mechanisms and most traditional managerial controls? Catalytic mechanisms share five characteristics. First, they produce desired results in unpredictable ways. Second, they distribute power for the benefit of the overall system, often to the discomfort of those who traditionally hold power. Third, catalytic mechanisms have teeth. Fourth, they eject "viruses"--those people who don't share the company's core values. Finally, they produce an ongoing effect. Catalytic mechanisms are just as effective for reaching individual goals as they are for corporate ones. To illustrate how catalytic mechanisms work, the author draws on examples of individuals and organizations that have relied on such mechanisms to achieve their goals. The same catalytic mechanism that works in one organization, however, will not necessarily work in another. Catalytic mechanisms must be tailored to specific goals and situations. To help readers get started, the author offers some general principles that support the process of building catalytic mechanisms effectively. PMID:10539210

  13. Turning goals into results: the power of catalytic mechanisms.

    PubMed

    Collins, J

    1999-01-01

    Most executives have a big, hairy, audacious goal. They write vision statements, formalize procedures, and develop complicated incentive programs--all in pursuit of that goal. In other words, with the best of intentions, they install layers of stultifying bureaucracy. But it doesn't have to be that way. In this article, Jim Collins introduces the catalytic mechanism, a simple yet powerful managerial tool that helps translate lofty aspirations into concrete reality. Catalytic mechanisms are the crucial link between objectives and performance; they are a galvanizing, nonbureaucratic means to turn one into the other. What's the difference between catalytic mechanisms and most traditional managerial controls? Catalytic mechanisms share five characteristics. First, they produce desired results in unpredictable ways. Second, they distribute power for the benefit of the overall system, often to the discomfort of those who traditionally hold power. Third, catalytic mechanisms have teeth. Fourth, they eject "viruses"--those people who don't share the company's core values. Finally, they produce an ongoing effect. Catalytic mechanisms are just as effective for reaching individual goals as they are for corporate ones. To illustrate how catalytic mechanisms work, the author draws on examples of individuals and organizations that have relied on such mechanisms to achieve their goals. The same catalytic mechanism that works in one organization, however, will not necessarily work in another. Catalytic mechanisms must be tailored to specific goals and situations. To help readers get started, the author offers some general principles that support the process of building catalytic mechanisms effectively.

  14. Iron-catalysed cross-coupling of organolithium compounds with organic halides

    PubMed Central

    Jia, Zhenhua; Liu, Qiang; Peng, Xiao-Shui; Wong, Henry N. C.

    2016-01-01

    In past decades, catalytic cross-coupling reactions between organic halides and organometallic reagents to construct carbon–carbon bond have achieved a tremendous progress. However, organolithium reagents have rarely been used in cross-coupling reactions, due mainly to their high reactivity. Another limitation of this transformation using organolithium reagents is how to control reactivity with excellent selectivity. Although palladium catalysis has been applied in this field recently, the development of an approach to replace catalytic systems of noble metals with nonprecious metals is currently in high demand. Herein, we report an efficient synthetic protocol involving iron-catalysed cross-coupling reactions employing organolithium compounds as key coupling partners to unite aryl, alkyl and benzyl fragments and also disclose an efficient iron-catalysed release-capture ethylene coupling with isopropyllithium. PMID:26847602

  15. Microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne.

    PubMed

    Feng, Huangdi; Ermolat'ev, Denis S; Song, Gonghua; Van der Eycken, Erik V

    2011-09-16

    A novel and efficient microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne (OA(2)-coulpling) has been developed. This new multicomponent coupling constitutes an efficient approach for the synthesis of polysubstituted propargylamines in the presence of a catalytic amount of copper(I) catalyst. PMID:21823621

  16. Spatial self organization of surface structure during an oscillating catalytic reaction

    NASA Astrophysics Data System (ADS)

    Cox, M. P.; Ertl, G.; Imbihl, R.

    1985-04-01

    Under appropriate conditions, the rate of catalytic CO oxidation on a Pt(100) surface exhibits sustained temporal oscillations which are associated with a periodic surface-structural transformation from, the reconstructed (hex) to the nonreconstructed (1×1) phase and back again. By use of a newly developed scanning low-energy electron diffraction technique it is demonstrated that spatial self-organization in the oscillations involves a wavelike propagation of alternating bands of the two surface-structural modifications across the entire scanned area. These features can be modeled by numerical solution of a set of coupled differential equations.

  17. Dynamical quorum sensing and synchronization in collections of excitable and oscillatory catalytic particles

    NASA Astrophysics Data System (ADS)

    Tinsley, M. R.; Taylor, A. F.; Huang, Z.; Wang, F.; Showalter, K.

    2010-06-01

    We present experimental studies of interacting excitable and oscillatory catalytic particles in well-stirred and spatially distributed systems. A number of distinct paths to synchronized oscillatory behavior are described. We present an example of a Kuramoto type transition in a well-stirred system with a collective rhythm emerging on increasing the number density of oscillatory particles. Groups of spatially distributed oscillatory particles become entrained to a common frequency by organizing centers. Quorum sensing type transitions are found in populations of globally and locally coupled excitable particles, with a sharp transition from steady state to fully synchronized behavior at a critical density or group size.

  18. The Concise Guide to Pharmacology 2013/14: Catalytic Receptors

    PubMed Central

    Alexander, Stephen PH; Benson, Helen E; Faccenda, Elena; Pawson, Adam J; Sharman, Joanna L; Spedding, Michael; Peters, John A; Harmar, Anthony J

    2013-01-01

    The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Catalytic receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates. PMID:24528241

  19. [Reductive dechlorination of trichloroacetic acid by bioelectrochemically catalytic method].

    PubMed

    Li, Yu-Ping; Cao, Hong-Bin; Zhang, Yi

    2005-07-01

    Direct electrochemical behaviors of hemoglobin (Hb) immobilized on carbon nanotube (CNT) modified carbon paste electrode with adsorption were investigated. Cyclic voltammetry of Hb-CNT-modified electrode showed a pair of well-defined and nearly reversible peaks for HbhemeFe(III) /Fe(II) redox couple in pH = 7 PBS buffers. The electrocatalytic behaviors of Hb-CNT-modified electrode for the reductive dechlorination of trichloroacetic acid (TCA) were studied by cyclic voltammmetry and fixed-potential electrolysis technique, and the reductive mechanism of TCA was discussed by analysis of reduction products. The results showed that Hb-CNT-modified electrode possessed good electro-catalytic activity for reduction of TCA and the dechlorination of TCA was stepwise, following the pathway of trichloroacetic--> dichloroacetic--> monochloroacetic--> acetic. The dechlorination of TCA in waster water was investigated using a two-compartment flow reactor with working electrode compartment packed with Hb-CNT-modified graphite electrode. The conversion of TCA was 40.13% with electrolysis for 180 min at - 0.60V (vs. SCE).

  20. Structural Basis for Catalytic Activation of a Serine Recombinase

    SciTech Connect

    Keenholtz, Ross A.; Rowland, Sally-J.; Boocock, Martin R.; Stark, W. Marshall; Rice, Phoebe A.

    2014-10-02

    Sin resolvase is a site-specific serine recombinase that is normally controlled by a complex regulatory mechanism. A single mutation, Q115R, allows the enzyme to bypass the entire regulatory apparatus, such that no accessory proteins or DNA sites are required. Here, we present a 1.86 {angstrom} crystal structure of the Sin Q115R catalytic domain, in a tetrameric arrangement stabilized by an interaction between Arg115 residues on neighboring subunits. The subunits have undergone significant conformational changes from the inactive dimeric state previously reported. The structure provides a new high-resolution view of a serine recombinase active site that is apparently fully assembled, suggesting roles for the conserved active site residues. The structure also suggests how the dimer-tetramer transition is coupled to assembly of the active site. The tetramer is captured in a different rotational substate than that seen in previous hyperactive serine recombinase structures, and unbroken crossover site DNA can be readily modeled into its active sites.

  1. Catalytic bioscavengers in nerve agent poisoning: A promising approach?

    PubMed

    Worek, Franz; Thiermann, Horst; Wille, Timo

    2016-02-26

    The repeated use of the nerve agent sarin against civilians in Syria in 2013 emphasizes the continuing threat by chemical warfare agents. Multiple studies demonstrated a limited efficacy of standard atropine-oxime treatment in nerve agent poisoning and called for the development of alternative and more effective treatment strategies. A novel approach is the use of stoichiometric or catalytic bioscavengers for detoxification of nerve agents in the systemic circulation prior to distribution into target tissues. Recent progress in the design of enzyme mutants with reversed stereo selectivity resulting in improved catalytic activity and their use in in vivo studies supports the concept of catalytic bioscavengers. Yet, further research is necessary to improve the catalytic activity, substrate spectrum and in vivo biological stability of enzyme mutants. The pros and cons of catalytic bioscavengers will be discussed in detail and future requirements for the development of catalytic bioscavengers will be proposed.

  2. Insights into the catalytic mechanism of synthetic glutathione peroxidase mimetics.

    PubMed

    Bhowmick, Debasish; Mugesh, Govindasamy

    2015-11-01

    Glutathione Peroxidase (GPx) is a key selenoenzyme that protects biomolecules from oxidative damage. Extensive research has been carried out to design and synthesize small organoselenium compounds as functional mimics of GPx. While the catalytic mechanism of the native enzyme itself is poorly understood, the synthetic mimics follow different catalytic pathways depending upon the structures and reactivities of various intermediates formed in the catalytic cycle. The steric as well as electronic environments around the selenium atom not only modulate the reactivity of these synthetic mimics towards peroxides and thiols, but also the catalytic mechanisms. The catalytic cycle of small GPx mimics is also dependent on the nature of peroxides and thiols used in the study. In this review, we discuss how the catalytic mechanism varies with the substituents attached to the selenium atom.

  3. Catalytic Mechanism of Human Alpha-galactosidase

    SciTech Connect

    Guce, A.; Clark, N; Salgado, E; Ivanen, D; Kulinskaya, A; Brumer, H; Garman, S

    2010-01-01

    The enzyme {alpha}-galactosidase ({alpha}-GAL, also known as {alpha}-GAL A; E.C. 3.2.1.22) is responsible for the breakdown of {alpha}-galactosides in the lysosome. Defects in human {alpha}-GAL lead to the development of Fabry disease, a lysosomal storage disorder characterized by the buildup of {alpha}-galactosylated substrates in the tissues. {alpha}-GAL is an active target of clinical research: there are currently two treatment options for Fabry disease, recombinant enzyme replacement therapy (approved in the United States in 2003) and pharmacological chaperone therapy (currently in clinical trials). Previously, we have reported the structure of human {alpha}-GAL, which revealed the overall structure of the enzyme and established the locations of hundreds of mutations that lead to the development of Fabry disease. Here, we describe the catalytic mechanism of the enzyme derived from x-ray crystal structures of each of the four stages of the double displacement reaction mechanism. Use of a difluoro-{alpha}-galactopyranoside allowed trapping of a covalent intermediate. The ensemble of structures reveals distortion of the ligand into a {sup 1}S{sub 3} skew (or twist) boat conformation in the middle of the reaction cycle. The high resolution structures of each step in the catalytic cycle will allow for improved drug design efforts on {alpha}-GAL and other glycoside hydrolase family 27 enzymes by developing ligands that specifically target different states of the catalytic cycle. Additionally, the structures revealed a second ligand-binding site suitable for targeting by novel pharmacological chaperones.

  4. Catalytic Activities Of [GADV]-Peptides

    NASA Astrophysics Data System (ADS)

    Oba, Takae; Fukushima, Jun; Maruyama, Masako; Iwamoto, Ryoko; Ikehara, Kenji

    2005-10-01

    We have previously postulated a novel hypothesis for the origin of life, assuming that life on the earth originated from “[GADV]-protein world”, not from the “RNA world” (see Ikehara's review, 2002). The [GADV]-protein world is constituted from peptides and proteins with random sequences of four amino acids (glycine [G], alanine [A], aspartic acid [D] and valine [V]), which accumulated by pseudo-replication of the [GADV]-proteins. To obtain evidence for the hypothesis, we produced [GADV]-peptides by repeated heat-drying of the amino acids for 30 cycles ([GADV]-P30) and examined whether the peptides have some catalytic activities or not. From the results, it was found that the [GADV]-P30 can hydrolyze several kinds of chemical bonds in molecules, such as umbelliferyl-β-D-galactoside, glycine-p-nitroanilide and bovine serum albumin. This suggests that [GADV]-P30 could play an important role in the accumulation of [GADV]-proteins through pseudo-replication, leading to the emergence of life. We further show that [GADV]-octapaptides with random sequences, but containing no cyclic compounds as diketepiperazines, have catalytic activity, hydrolyzing peptide bonds in a natural protein, bovine serum albumin. The catalytic activity of the octapeptides was much higher than the [GADV]-P30 produced through repeated heat-drying treatments. These results also support the [GADV]-protein-world hypothesis of the origin of life (see Ikehara's review, 2002). Possible steps for the emergence of life on the primitive earth are presented.

  5. Thin film porous membranes for catalytic sensors

    SciTech Connect

    Hughes, R.C.; Boyle, T.J.; Gardner, T.J.

    1997-06-01

    This paper reports on new and surprising experimental data for catalytic film gas sensing resistors coated with nanoporous sol-gel films to impart selectivity and durability to the sensor structure. This work is the result of attempts to build selectivity and reactivity to the surface of a sensor by modifying it with a series of sol-gel layers. The initial sol-gel SiO{sub 2} layer applied to the sensor surprisingly showed enhanced O{sub 2} interaction with H{sub 2} and reduced susceptibility to poisons such as H{sub 2}S.

  6. Catalytic asymmetric formal synthesis of beraprost.

    PubMed

    Kobayashi, Yusuke; Kuramoto, Ryuta; Takemoto, Yoshiji

    2015-01-01

    The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an enantioselective intramolecular oxa-Michael reaction of an α,β-unsaturated amide mediated by a newly developed benzothiadiazine catalyst. The Weinreb amide moiety and bromo substituent of the Michael adduct were utilized for the C-C bond formations to construct the scaffold. All four contiguous stereocenters of the tricyclic core were controlled via Rh-catalyzed stereoselective C-H insertion and the subsequent reduction from the convex face.

  7. Catalytic asymmetric formal synthesis of beraprost

    PubMed Central

    Kobayashi, Yusuke; Kuramoto, Ryuta

    2015-01-01

    Summary The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an enantioselective intramolecular oxa-Michael reaction of an α,β-unsaturated amide mediated by a newly developed benzothiadiazine catalyst. The Weinreb amide moiety and bromo substituent of the Michael adduct were utilized for the C–C bond formations to construct the scaffold. All four contiguous stereocenters of the tricyclic core were controlled via Rh-catalyzed stereoselective C–H insertion and the subsequent reduction from the convex face. PMID:26734111

  8. Process for catalytic reaction of heavy oils

    SciTech Connect

    Ushio, M.; Ishii, T.; Morita, T.; Oishi, Y.

    1984-11-13

    A process for catalytic reaction of heavy oils and a particulate solid medium, which comprises withdrawing a part or the whole of the used medium from the reactor, separating the withdrawn particles into the particles which have been rendered magnetic by the deposition thereon of nickel, vanadium, iron and copper originally contained in the heavy oils, and non-magnetic particles, using a high gradient magnetic separator which is so designed that a ferromagnetic matrix is placed in a uniform high magnetic field, and returning the non-magnetic particles of the medium into the reactor for re-use.

  9. Transient Numerical Modeling of Catalytic Channels

    NASA Technical Reports Server (NTRS)

    Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

    2007-01-01

    This paper presents a transient model of catalytic combustion suitable for isolated channels and monolith reactors. The model is a lumped two-phase (gas and solid) model where the gas phase is quasi-steady relative to the transient solid. Axial diffusion is neglected in the gas phase; lateral diffusion, however, is accounted for using transfer coefficients. The solid phase includes axial heat conduction and external heat loss due to convection and radiation. The combustion process utilizes detailed gas and surface reaction models. The gas-phase model becomes a system of stiff ordinary differential equations while the solid phase reduces, after discretization, into a system of stiff ordinary differential-algebraic equations. The time evolution of the system came from alternating integrations of the quasi-steady gas and transient solid. This work outlines the numerical model and presents some sensitivity studies on important parameters including internal transfer coefficients, catalytic surface site density, and external heat-loss (if applicable). The model is compared to two experiments using CO fuel: (1) steady-state conversion through an isothermal platinum (Pt) tube and (2) transient propagation of a catalytic reaction inside a small Pt tube. The model requires internal mass-transfer resistance to match the experiments at lower residence times. Under mass-transport limited conditions, the model reasonably predicted exit conversion using global mass-transfer coefficients. Near light-off, the model results did not match the experiment precisely even after adjustment of mass-transfer coefficients. Agreement improved for the first case after adjusting the surface kinetics such that the net rate of CO adsorption increased compared to O2. The CO / O2 surface mechanism came from a sub-set of reactions in a popular CH4 / O2 mechanism. For the second case, predictions improved for lean conditions with increased external heat loss or adjustment of the kinetics as in the

  10. Catalytic combustion with incompletely vaporized residual fuel

    NASA Technical Reports Server (NTRS)

    Rosfjord, T. J.

    1981-01-01

    Catalytic combustion of fuel lean mixtures of incompletely vaporized residual fuel and air was investigated. The 7.6 cm diameter, graded cell reactor was constructed from zirconia spinel substrate and catalyzed with a noble metal catalyst. Streams of luminous particles exited the rector as a result of fuel deposition and carbonization on the substrate. Similar results were obtained with blends of No. 6 and No. 2 oil. Blends of shale residual oil and No. 2 oil resulted in stable operation. In shale oil blends the combustor performance degraded with a reduced degree of fuel vaporization. In tests performed with No. 2 oil a similar effect was observed.

  11. The Catalytic Enantioselective Total Synthesis of (+)-Liphagal**

    PubMed Central

    Day, Joshua J.; McFadden, Ryan M.; Virgil, Scott C.; Kolding, Helene; Alleva, Jennifer L.; Stoltz, Brian M.

    2012-01-01

    Ring a ding: The first catalytic enantioselective total synthesis of the meroterpenoid natural product (+)-liphagal is disclosed. The approach showcases a variety of technology including enantioselective enolate alkylation, a photochemical alkyne-alkene [2+2] reaction, microwave-assisted metal catalysis, and an intramolecular aryne capture cyclization reaction. Pivotal to the successful completion of the synthesis was a sequence involving ring expansion from a [6-5-4] tricycle to a [6-7] bicyclic core followed by stereoselective hydrogenation of a sterically occluded tri-substituted olefin to establish the trans homodecalin system found in the natural product. PMID:21671325

  12. Catalytic Enantioselective Synthesis of Quaternary Carbon Stereocenters

    PubMed Central

    Quasdorf, Kyle W.; Overman, Larry E.

    2015-01-01

    Preface Quaternary carbon stereocenters–carbon atoms to which four distinct carbon substituents are attached–are common features of molecules found in nature. However, prior to recent advances in chemical catalysis, there were few methods available for constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for synthesizing organic molecules containing such carbon atoms. This progress now makes it possible to selectively incorporate quaternary stereocenters in many high-value organic molecules for use in medicine, agriculture, and other areas. PMID:25503231

  13. Enzymatic Catalytic Beds For Oxidation Of Alcohols

    NASA Technical Reports Server (NTRS)

    Jolly, Clifford D.; Schussel, Leonard J.

    1993-01-01

    Modules containing beds of enzymatic material catalyzing oxidation of primary alcohols and some other organic compounds developed for use in wastewater-treatment systems of future spacecraft. Designed to be placed downstream of multifiltration modules, which contain filters and sorbent beds removing most of non-alcoholic contaminants but fail to remove significant amounts of low-molecular-weight, polar, nonionic compounds like alcohols. Catalytic modules also used on Earth to oxidize primary alcohols and other compounds in wastewater streams and industrial process streams.

  14. Transport in a Microfluidic Catalytic Reactor

    SciTech Connect

    Park, H G; Chung, J; Grigoropoulos, C P; Greif, R; Havstad, M; Morse, J D

    2003-04-30

    A study of the heat and mass transfer, flow, and thermodynamics of the reacting flow in a catalytic microreactor is presented. Methanol reforming is utilized in the fuel processing system driving a micro-scale proton exchange membrane fuel cell. Understanding the flow and thermal transport phenomena as well as the reaction mechanisms is essential for improving the efficiency of the reforming process as well as the quality of the processed fuel. Numerical studies have been carried out to characterize the transport in a silicon microfabricated reactor system. On the basis of these results, optimized conditions for fuel processing are determined.

  15. Cross-Electrophile Coupling: Principles of Reactivity and Selectivity

    PubMed Central

    2015-01-01

    A critical overview of the catalytic joining of two different electrophiles, cross-electrophile coupling (XEC), is presented with an emphasis on the central challenge of cross-selectivity. Recent synthetic advances and mechanistic studies have shed light on four possible methods for overcoming this challenge: (1) employing an excess of one reagent; (2) electronic differentiation of starting materials; (3) catalyst–substrate steric matching; and (4) radical chain processes. Each method is described using examples from the recent literature. PMID:24820397

  16. Quorum Sensing and Synchronization in Populations of Coupled Chemical Oscillators

    NASA Astrophysics Data System (ADS)

    Taylor, Annette F.; Tinsley, Mark R.; Showalter, Kenneth

    2013-12-01

    Experiments and simulations of populations of coupled chemical oscillators, consisting of catalytic particles suspended in solution, provide insights into density-dependent dynamics displayed by many cellular organisms. Gradual synchronization transitions, the "switching on" of activity above a threshold number of oscillators (quorum sensing) and the formation of synchronized groups (clusters) of oscillators have been characterized. Collective behavior is driven by the response of the oscillators to chemicals emitted into the surrounding solution.

  17. Operation regimes in catalytic combustion: H{sub 2}/air mixtures near Pt

    SciTech Connect

    Park, Y.K.; Bui, P.A.; Vlachos, D.G.

    1998-09-01

    The influence of a platinum catalyst on flammability limits and operation windows for catalytic and catalyst-assisted homogeneous oxidation is studied, for the first time to the authors` knowledge, as a function of H{sub 2} in air composition in a stagnation-point flow geometry. The results show that the coupling between the homogeneous and heterogeneous chemistries leads to relatively easy startup, the coexistence of catalytically (partially) and homogeneously (completely) ignited branches under certain conditions, and the expansion of the fuel-lean and rich flammability limits. A strategy to attain virtually any desired operation regime is discussed. It is shown that synergism between homogeneous and heterogeneous chemistries leads to higher combustion efficiency and lower fuel emissions at elevated temperatures for fuel-lean mixtures only. Analysis of the flammability limits indicates that heat generated by surface reactions is primarily responsible for expansion of the flammability limits. Finally, a direct transition to flames occurs over a wide range of composition upon catalytic ignition in the absence of surface heat loss.

  18. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    SciTech Connect

    Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; Li, Jun; Rousseau, Roger J.

    2015-03-04

    Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO2 catalyst, which is a lower energy pathway than that of CO oxidation at the interface with the metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.

  19. Light-concentrating plasmonic Au superstructures with significantly visible-light-enhanced catalytic performance.

    PubMed

    Yang, Jinhu; Li, Ying; Zu, Lianhai; Tong, Lianming; Liu, Guanglei; Qin, Yao; Shi, Donglu

    2015-04-22

    Noble metals are well-known for their surface plasmon resonance effect that enables strong light absorption typically in the visible regions for gold and silver. However, unlike semiconductors, noble metals are commonly considered incapable of catalyzing reactions via photogenerated electron-hole pairs due to their continuous energy band structures. So far, photonically activated catalytic system based on pure noble metal nanostructures has seldom been reported. Here, we report the development of three different novel plasmonic Au superstructures comprised of Au nanoparticles, multiple-twinned nanoparticles and nanoworms assembling on the surfaces of SiO2 nanospheres respectively via a well-designed synthetic strategy. It is found that these novel Au superstructures show enhanced broadband visible-light absorption due to the plasmon resonance coupling within the superstructures, and thus can effectively focus the energy of photon fluxes to generate much more excited hot electrons and holes for promoting catalytic reactions. Accordingly, these Au superstructures exhibit significantly visible-light-enhanced catalytic efficiency (up to ∼264% enhancement) for the commercial reaction of p-nitrophenol reduction. PMID:25840556

  20. Stability, surface features, and atom leaching of palladium nanoparticles: toward prediction of catalytic functionality.

    PubMed

    Ramezani-Dakhel, Hadi; Mirau, Peter A; Naik, Rajesh R; Knecht, Marc R; Heinz, Hendrik

    2013-04-21

    Surfactant-stabilized metal nanoparticles have shown promise as catalysts although specific surface features and their influence on catalytic performance have not been well understood. We quantify the thermodynamic stability, the facet composition of the surface, and distinct atom types that affect rates of atom leaching for a series of twenty near-spherical Pd nanoparticles of 1.8 to 3.1 nm size using computational models. Cohesive energies indicate higher stability of certain particles that feature an approximate 60/20/20 ratio of {111}, {100}, and {110} facets while less stable particles exhibit widely variable facet composition. Unique patterns of atom types on the surface cause apparent differences in binding energies and changes in reactivity. Estimates of the relative rate of atom leaching as a function of particle size were obtained by the summation of Boltzmann-weighted binding energies over all surface atoms. Computed leaching rates are in good qualitative correlation with the measured catalytic activity of peptide-stabilized Pd nanoparticles of the same shape and size in Stille coupling reactions. The agreement supports rate-controlling contributions by atom leaching in the presence of reactive substrates. The computational approach provides a pathway to estimate the catalytic activity of metal nanostructures of engineered shape and size, and possible further refinements are described.

  1. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    DOE PAGES

    Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; Li, Jun; Rousseau, Roger J.

    2015-03-04

    Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO2 catalyst, which is a lower energy pathway than that of CO oxidation at the interface with themore » metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.« less

  2. Hydrogen-assisted catalytic ignition characteristics of different fuels

    SciTech Connect

    Zhong, Bei-Jing; Yang, Fan; Yang, Qing-Tao

    2010-10-15

    Hydrogen-assisted catalytic ignition characteristics of methane (CH{sub 4}), n-butane (n-C{sub 4}H{sub 10}) and dimethyl ether (DME) were studied experimentally in a Pt-coated monolith catalytic reactor. It is concluded that DME has the lowest catalytic ignition temperature and the least required H{sub 2} flow, while CH{sub 4} has the highest catalytic ignition temperature and the highest required H{sub 2} flow among the three fuels. (author)

  3. Ionizable Side Chains at Catalytic Active Sites of Enzymes

    PubMed Central

    Jimenez-Morales, David; Liang, Jie

    2012-01-01

    Catalytic active sites of enzymes of known structure can be well defined by a modern program of computational geometry. The CASTp program was used to define and measure the volume of the catalytic active sites of 573 enzymes in the Catalytic Site Atlas database. The active sites are identified as catalytic because the amino acids they contain are known to participate in the chemical reaction catalyzed by the enzyme. Acid and base side chains are reliable markers of catalytic active sites. The catalytic active sites have 4 acid and 5 base side chains, in an average volume of 1072 Å3. The number density of acid side chains is 8.3 M (in chemical units); the number density of basic side chains is 10.6 M. The catalytic active site of these enzymes is an unusual electrostatic and steric environment in which side chains and reactants are crowded together in a mixture more like an ionic liquid than an ideal infinitely dilute solution. The electrostatics and crowding of reactants and side chains seems likely to be important for catalytic function. In three types of analogous ion channels, simulation of crowded charges accounts for the main properties of selectivity measured in a wide range of solutions and concentrations. It seems wise to use mathematics designed to study interacting complex fluids when making models of the catalytic active sites of enzymes. PMID:22484856

  4. Piloted rich-catalytic lean-burn hybrid combustor

    DOEpatents

    Newburry, Donald Maurice

    2002-01-01

    A catalytic combustor assembly which includes, an air source, a fuel delivery means, a catalytic reactor assembly, a mixing chamber, and a means for igniting a fuel/air mixture. The catalytic reactor assembly is in fluid communication with the air source and fuel delivery means and has a fuel/air plenum which is coated with a catalytic material. The fuel/air plenum has cooling air conduits passing therethrough which have an upstream end. The upstream end of the cooling conduits is in fluid communication with the air source but not the fuel delivery means.

  5. Catalytic hydrothermal liquefaction of water hyacinth.

    PubMed

    Singh, Rawel; Balagurumurthy, Bhavya; Prakash, Aditya; Bhaskar, Thallada

    2015-02-01

    Thermal and catalytic hydrothermal liquefaction of water hyacinth was performed at temperatures from 250 to 300 °C under various water hyacinth:H2O ratio of 1:3, 1:6 and 1:12. Reactions were also carried out under various residence times (15-60 min) as well as catalytic conditions (KOH and K2CO3). The use of alkaline catalysts significantly increased the bio-oil yield. Maximum bio-oil yield (23 wt%) comprising of bio-oil1 and bio-oil2 as well as conversion (89%) were observed with 1N KOH solution. (1)H NMR and (13)C NMR data showed that both bio-oil1 and bio-oil2 have high aliphatic carbon content. FTIR of bio-residue indicated that the usage of alkaline catalyst resulted in bio-residue samples with lesser oxygen functionality indicating that catalyst has a marked effect on nature of the bio-residue and helps to decompose biomass to a greater extent compared to thermal case. PMID:25240515

  6. Computational and Physical Analysis of Catalytic Compounds

    NASA Astrophysics Data System (ADS)

    Wu, Richard; Sohn, Jung Jae; Kyung, Richard

    2015-03-01

    Nanoparticles exhibit unique physical and chemical properties depending on their geometrical properties. For this reason, synthesis of nanoparticles with controlled shape and size is important to use their unique properties. Catalyst supports are usually made of high-surface-area porous oxides or carbon nanomaterials. These support materials stabilize metal catalysts against sintering at high reaction temperatures. Many studies have demonstrated large enhancements of catalytic behavior due to the role of the oxide-metal interface. In this paper, the catalyzing ability of supported nano metal oxides, such as silicon oxide and titanium oxide compounds as catalysts have been analyzed using computational chemistry method. Computational programs such as Gamess and Chemcraft has been used in an effort to compute the efficiencies of catalytic compounds, and bonding energy changes during the optimization convergence. The result illustrates how the metal oxides stabilize and the steps that it takes. The graph of the energy computation step(N) versus energy(kcal/mol) curve shows that the energy of the titania converges faster at the 7th iteration calculation, whereas the silica converges at the 9th iteration calculation.

  7. Catalytic reactor for low-Btu fuels

    SciTech Connect

    Smith, Lance; Etemad, Shahrokh; Karim, Hasan; Pfefferle, William C.

    2009-04-21

    An improved catalytic reactor includes a housing having a plate positioned therein defining a first zone and a second zone, and a plurality of conduits fabricated from a heat conducting material and adapted for conducting a fluid therethrough. The conduits are positioned within the housing such that the conduit exterior surfaces and the housing interior surface within the second zone define a first flow path while the conduit interior surfaces define a second flow path through the second zone and not in fluid communication with the first flow path. The conduit exits define a second flow path exit, the conduit exits and the first flow path exit being proximately located and interspersed. The conduits define at least one expanded section that contacts adjacent conduits thereby spacing the conduits within the second zone and forming first flow path exit flow orifices having an aggregate exit area greater than a defined percent of the housing exit plane area. Lastly, at least a portion of the first flow path defines a catalytically active surface.

  8. Catalytic pyrolysis of automobile shredder residue

    SciTech Connect

    Arzoumanidis, G.G.; McIntosh, M.J.; Steffensen, E.J.

    1995-07-01

    In the United States, approximately 10 million automobiles are scrapped and shredded each year. The mixture of plastics and other materials remaining after recovery of the metals is known as Automobile Shredder Residue (ASR). In 1994, about 3.5 million tons of ASR was produced and disposed of in landfills. However, environmental, legislative, and economic considerations are forcing the industry to search for recycling or other alternatives to disposal. Numerous studies have been done relating the ASR disposal problem to possible recycling treatments such as pyrolysis, gasification, co-liquefaction of ASR with coal, chemical recovery of plastics from ASR, catalytic pyrolysis, reclamation in molten salts, and vacuum pyrolysis. These and other possibilities have been studied intensively, and entire symposia have been devoted to the problem. Product mix, yields, toxicology issues, and projected economics of conceptual plant designs based on experimental results are among the key elements of past studies. Because the kinds of recycling methods that may be developed, along with their ultimate economic value, depend on a very large number of variables, these studies have been open-ended. It is hoped that it may be useful to explore some of these previously studied areas from fresh perspectives. One such approach, currently under development at Argonne National Laboratory, is the catalytic pyrolysis of ASR.

  9. Cutoff lensing: predicting catalytic sites in enzymes

    NASA Astrophysics Data System (ADS)

    Aubailly, Simon; Piazza, Francesco

    2015-10-01

    Predicting function-related amino acids in proteins with unknown function or unknown allosteric binding sites in drug-targeted proteins is a task of paramount importance in molecular biomedicine. In this paper we introduce a simple, light and computationally inexpensive structure-based method to identify catalytic sites in enzymes. Our method, termed cutoff lensing, is a general procedure consisting in letting the cutoff used to build an elastic network model increase to large values. A validation of our method against a large database of annotated enzymes shows that optimal values of the cutoff exist such that three different structure-based indicators allow one to recover a maximum of the known catalytic sites. Interestingly, we find that the larger the structures the greater the predictive power afforded by our method. Possible ways to combine the three indicators into a single figure of merit and into a specific sequential analysis are suggested and discussed with reference to the classic case of HIV-protease. Our method could be used as a complement to other sequence- and/or structure-based methods to narrow the results of large-scale screenings.

  10. Catalytic hydrothermal liquefaction of water hyacinth.

    PubMed

    Singh, Rawel; Balagurumurthy, Bhavya; Prakash, Aditya; Bhaskar, Thallada

    2015-02-01

    Thermal and catalytic hydrothermal liquefaction of water hyacinth was performed at temperatures from 250 to 300 °C under various water hyacinth:H2O ratio of 1:3, 1:6 and 1:12. Reactions were also carried out under various residence times (15-60 min) as well as catalytic conditions (KOH and K2CO3). The use of alkaline catalysts significantly increased the bio-oil yield. Maximum bio-oil yield (23 wt%) comprising of bio-oil1 and bio-oil2 as well as conversion (89%) were observed with 1N KOH solution. (1)H NMR and (13)C NMR data showed that both bio-oil1 and bio-oil2 have high aliphatic carbon content. FTIR of bio-residue indicated that the usage of alkaline catalyst resulted in bio-residue samples with lesser oxygen functionality indicating that catalyst has a marked effect on nature of the bio-residue and helps to decompose biomass to a greater extent compared to thermal case.

  11. Catalytic hydroprocessing of heavy oil feedstocks

    NASA Astrophysics Data System (ADS)

    Okunev, A. G.; Parkhomchuk, E. V.; Lysikov, A. I.; Parunin, P. D.; Semeikina, V. S.; Parmon, V. N.

    2015-09-01

    A grave problem of modern oil refining industry is continuous deterioration of the produced oil quality, on the one hand, and increase in the demand for motor fuels, on the other hand. This necessitates processing of heavy oil feedstock with high contents of sulfur, nitrogen and metals and the atmospheric residue. This feedstock is converted to light oil products via hydrogenation processes catalyzed by transition metal compounds, first of all, cobalt- or nickel-promoted molybdenum and tungsten compounds. The processing involves desulfurization, denitrogenation and demetallization reactions as well as reactions converting heavy hydrocarbons to lighter fuel components. The review discusses the mechanisms of reactions involved in the heavy feedstock hydroprocessing, the presumed structure and state of the catalytically active components and methods for the formation of supports with the desired texture. Practically used and prospective approaches to catalytic upgrading of heavy oil feedstock as well as examples of industrial processing of bitumen and vacuum residues in the presence of catalysts are briefly discussed. The bibliography includes 140 references.

  12. Catalytic Activity of a Binary Informational Macromolecule

    NASA Technical Reports Server (NTRS)

    Reader, John S.; Joyce, Gerald F.

    2003-01-01

    RNA molecules are thought to have played a prominent role in the early history of life on Earth based on their ability both to encode genetic information and to exhibit catalytic function. The modern genetic alphabet relies on two sets of complementary base pairs to store genetic information. However, due to the chemical instability of cytosine, which readily deaminates to uracil, a primitive genetic system composed of the bases A, U, G and C may have been difficult to establish. It has been suggested that the first genetic material instead contained only a single base-pairing unie'. Here we show that binary informational macromolecules, containing only two different nucleotide subunits, can act as catalysts. In vitro evolution was used to obtain ligase ribozymes composed of only 2,6-diaminopurine and uracil nucleotides, which catalyze the template-directed joining of two RNA molecules, one bearing a 5'-triphosphate and the other a 3'-hydroxyl. The active conformation of the fastest isolated ribozyme had a catalytic rate that was about 36,000-fold faster than the uncatalyzed rate of reaction. This ribozyme is specific for the formation of biologically relevant 3',5'-phosphodiester linkages.

  13. Lube catalytic dewaxing-hydrotreating process

    SciTech Connect

    Harandi, M.N.

    1989-08-01

    This patent describes a method of producing a catalytically dewaxed, hydrotreated lubricating oil of improved quality. It comprises: catalytically dewaxing a hydrocarbon lubricating oil fraction by contacting the fraction during a dewaxing/hydrotreating cycle with a zeolitic dewaxing catalyst in the presence of hydrogen under dewaxing conditions, to produce a dewaxed effluent, hydrotreating the dewaxed effluent by contacting the effluent during the dewaxing/hydrotreating cycle with a hydrotreating catalyst. The catalyst comprising a metal hydrogen component on a porous non-acidic support in the presence of hydrogen under hydrotreating conditions, to produce a hydrotreated, dewaxed effluent, reactivating the dewaxing catalyst at the end of the dewaxing/hydrotreating cycle contacting the dewaxing catalyst with hydrogen at an elevated temperature to restore dewaxing activity to the catalyst, oxidatively regenerating the hydrotreating catalyst at the end of the dewaxing/hydrotreating cycle by contacting the hydrotreating catalyst with an oxygen containing gas at an elevated temperature to restore hydrotreating activity to the catalyst, repeating the first two steps with the reactivated dewaxing and regenerated hydrotreating catalyst in a new dewaxing/hydrotreating cycle in which aromatic components formed by the hydrogenative reactivation of the dewaxing catalyst in the third step and sorbed on the dewaxing catalyst pass with the dewaxed effluent form the dewaxing catalyst to the hydrotreating catalyst on which they are sorbed during the initial stages of the dewaxing/hydrotreating cycle.

  14. Catalytic decomposition of petroleum into natural gas

    SciTech Connect

    Mango, F.D.; Hightower, J.

    1997-12-01

    Petroleum is believed to be unstable in the earth, decomposing to lighter hydrocarbons at temperatures > 150{degrees}C. Oil and gas deposits support this view: gas/oil ratios and methane concentrations tend to increase with depth above 150{degrees}C. Although oil cracking is suggested and receives wide support, laboratory pyrolysis does not give products resembling natural gas. Moreover, it is doubtful that the light hydrocarbons in wet gas (C{sub 2}-C{sub 4}) could decompose over geologic time to dry gas (>95% methane) without catalytic assistance. We now report the catalytic decomposition of crude oil to a gas indistinguishable from natural gas. Like natural gas in deep basins, it becomes progressively enriched in methane: initially 90% (wet gas) to a final composition of 100% methane (dry gas). To our knowledge, the reaction is unprecedented and unexpectedly robust (conversion of oil to gas is 100% in days, 175{degrees}C) with significant implications regarding the stability of petroleum in sedimentary basins. The existence or nonexistence of oil in the deep subsurface may not depend on the thermal stability of hydrocarbons as currently thought. The critical factor could be the presence of transition metal catalysts which destabilize hydrocarbons and promote their decomposition to natural gas.

  15. Structured materials for catalytic and sensing applications

    NASA Astrophysics Data System (ADS)

    Hokenek, Selma

    The optical and chemical properties of the materials used in catalytic and sensing applications directly determine the characteristics of the resultant catalyst or sensor. It is well known that a catalyst needs to have high activity, selectivity, and stability to be viable in an industrial setting. The hydrogenation activity of palladium catalysts is known to be excellent, but the industrial applications are limited by the cost of obtaining catalyst in amounts large enough to make their use economical. As a result, alloying palladium with a cheaper, more widely available metal while maintaining the high catalytic activity seen in monometallic catalysts is, therefore, an attractive option. Similarly, the optical properties of nanoscale materials used for sensing must be attuned to their application. By adjusting the shape and composition of nanoparticles used in such applications, very fine changes can be made to the frequency of light that they absorb most efficiently. The design, synthesis, and characterization of (i) size controlled monometallic palladium nanoparticles for catalytic applications, (ii) nickel-palladium bimetallic nanoparticles and (iii) silver-palladium nanoparticles with applications in drug detection and biosensing through surface plasmon resonance, respectively, will be discussed. The composition, size, and shape of the nanoparticles formed were controlled through the use of wet chemistry techniques. After synthesis, the nanoparticles were analyzed using physical and chemical characterization techniques such as X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Scanning Transmission Electron Microscopy- Energy-Dispersive Spectrometry (STEM-EDX). The Pd and Ni-Pd nanoparticles were then supported on silica for catalytic testing using mass spectrometry. The optical properties of the Ag-Pd nanoparticles in suspension were further investigated using ultraviolet-visible spectrometry (UV-Vis). Monometallic palladium particles have

  16. Kumada–Grignard-type biaryl couplings on water

    PubMed Central

    Bhattacharjya, Anish; Klumphu, Piyatida; Lipshutz, Bruce H.

    2015-01-01

    Well-established, traditional Kumada cross-couplings involve preformed Grignard reagents in dry ethereal solvent that typically react, e.g., with aryl halides via Pd catalysis to afford products of net substitution. Therefore, in the work described, which appears to be counterintuitive, exposure of these same aromatic halides to catalytic amounts of Pd(II) and excess magnesium metal in pure water leads to symmetrical/unsymmetrical biaryls, indicative of a net Kumada-like biaryl coupling. Evidence is presented suggesting that Grignard reagents, formed in situ in water, may be involved. PMID:26084774

  17. Nanorods, nanospheres, nanocubes: Synthesis, characterization and catalytic activity of nanoferrites of Mn, Co, Ni, Part-89

    SciTech Connect

    Singh, Supriya; Srivastava, Pratibha; Singh, Gurdip

    2013-02-15

    Graphical abstract: Prepared nanoferrites were characterized by FE-SEM and bright field TEM micrographs. The catalytic effect of these nanoferrites was evaluated on the thermal decomposition of ammonium perchlorate using TG and TG–DSC techniques. The kinetics of thermal decomposition of AP was evaluated using isothermal TG data by model fitting as well as isoconversional method. Display Omitted Highlights: ► Synthesis of ferrite nanostructures (∼20.0 nm) by wet-chemical method under different synthetic conditions. ► Characterization using XRD, FE-SEM, EDS, TEM, HRTEM and SAED pattern. ► Catalytic activity of ferrite nanostructures on AP thermal decomposition by thermal techniques. ► Burning rate measurements of CSPs with ferrite nanostructures. ► Kinetics of thermal decomposition of AP + nanoferrites. -- Abstract: In this paper, the nanoferrites of Mn, Co and Ni were synthesized by wet chemical method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive, X-ray spectra (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HR-TEM). It is catalytic activity were investigated on the thermal decomposition of ammonium perchlorate (AP) and composite solid propellants (CSPs) using thermogravimetry (TG), TG coupled with differential scanning calorimetry (TG–DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + nanoferrites have also been investigated using isoconversional and model fitting approaches which have been applied to data for isothermal TG decomposition. The burning rate of CSPs was considerably enhanced by these nanoferrites. Addition of nanoferrites to AP led to shifting of the high temperature decomposition peak toward lower temperature. All these studies reveal that ferrite nanorods show the best catalytic activity superior to that of nanospheres and nanocubes.

  18. Peptide-Directed PdAu Nanoscale Surface Segregation: Toward Controlled Bimetallic Architecture for Catalytic Materials.

    PubMed

    Bedford, Nicholas M; Showalter, Allison R; Woehl, Taylor J; Hughes, Zak E; Lee, Sungsik; Reinhart, Benjamin; Ertem, S Piril; Coughlin, E Bryan; Ren, Yang; Walsh, Tiffany R; Bunker, Bruce A

    2016-09-27

    Bimetallic nanoparticles are of immense scientific and technological interest given the synergistic properties observed when two different metallic species are mixed at the nanoscale. This is particularly prevalent in catalysis, where bimetallic nanoparticles often exhibit improved catalytic activity and durability over their monometallic counterparts. Yet despite intense research efforts, little is understood regarding how to optimize bimetallic surface composition and structure synthetically using rational design principles. Recently, it has been demonstrated that peptide-enabled routes for nanoparticle synthesis result in materials with sequence-dependent catalytic properties, providing an opportunity for rational design through sequence manipulation. In this study, bimetallic PdAu nanoparticles are synthesized with a small set of peptides containing known Pd and Au binding motifs. The resulting nanoparticles were extensively characterized using high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Structural information obtained from synchrotron radiation methods was then used to generate model nanoparticle configurations using reverse Monte Carlo simulations, which illustrate sequence dependence in both surface structure and surface composition. Replica exchange with solute tempering molecular dynamics simulations were also used to predict the modes of peptide binding on monometallic surfaces, indicating that different sequences bind to the metal interfaces via different mechanisms. As a testbed reaction, electrocatalytic methanol oxidation experiments were performed, wherein differences in catalytic activity are clearly observed in materials with identical bimetallic composition. Taken together, this study indicates that peptides could be used to arrive at bimetallic surfaces with enhanced catalytic properties, which could be leveraged

  19. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

    PubMed Central

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F.; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M.; Parvulescu, Vasile I.; García, Hermenegildo

    2015-01-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C–N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets. PMID:26509224

  20. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F.; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M.; Parvulescu, Vasile I.; García, Hermenegildo

    2015-10-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C-N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets.

  1. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film.

    PubMed

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M; Parvulescu, Vasile I; García, Hermenegildo

    2015-01-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C-N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets. PMID:26509224

  2. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    PubMed Central

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-01-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs. PMID:24495979

  3. An alternative synthetic approach for efficient catalytic conversion of syngas to ethanol.

    PubMed

    Yue, Hairong; Ma, Xinbin; Gong, Jinlong

    2014-05-20

    Ethanol is an attractive end product and a versatile feedstock because a widespread market exists for its commercial use as a fuel additive or a potential substitute for gasoline. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, particularly those containing six carbons, but coproducts 5-carbon sugars and lignin remain unusable. Another major process for commercial production of ethanol is hydration of ethylene over solid acidic catalysts, yet not sustainable considering the depletion of fossil fuels. Catalytic conversion of synthetic gas (CO + H2) could produce ethanol in large quantities. However, the direct catalytic conversion of synthetic gas to ethanol remains challenging, and no commercial process exists as of today although the research has been ongoing for the past 90 years, since such the process suffers from low yield and poor selectivity due to slow kinetics of the initial C-C bond formation and fast chain growth of the C2 intermediates. This Account describes recent developments in an alternative approach for the synthesis of ethanol via synthetic gas. This process is an integrated technology consisting of the coupling of CO with methanol to form dimethyl oxalate and the subsequent hydrogenation to yield ethanol. The byproduct of the second step (methanol) can be separated and used in circulation as the feedstock for the coupling step. The coupling reaction of carbon monoxide for producing dimethyl oxalate takes place under moderate reaction conditions with high selectivity (∼95%), which ideally leads to a self-closing, nonwaste, catalytic cycling process. This Account also summarizes the progress on the development of copper-based catalysts for the hydrogenation reaction with remarkable efficiencies and stability. The unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) species are responsible for the activity of the catalyst with high yield of ethanol (∼91%). The understanding of

  4. Study of Single Catalytic Events at Copper-in-Charcoal: Localization of Click Activity Through Subdiffraction Observation of Single Catalytic Events.

    PubMed

    Decan, Matthew R; Scaiano, Juan C

    2015-10-15

    Single molecule fluorescence microscopy reveals that copper-in-charcoal--a high performance click catalyst- has remarkably few catalytic sites, with 90% of the charcoal particles being inactive, and for the catalytic ones the active sites represent a minute fraction (∼0.003%) of the surface. The intermittent nature of the catalytic events enables subdiffraction resolution and mapping of the catalytic sites.

  5. Catalytic activities of platinum nanotubes: a density functional study

    NASA Astrophysics Data System (ADS)

    Mukherjee, Prajna; Gupta, Bikash C.; Jena, Puru

    2015-10-01

    In this work we investigate the catalytic properties of platinum nanotubes using density functional theory based calculations. In particular, we study the dissociation of hydrogen and oxygen molecules as well as oxidation of CO molecules. The results indicate that platinum nanotubes have good catalytic properties and can be effectively used in converting CO molecule to CO2.

  6. An effective and catalytic oxidation using recyclable fluorous IBX.

    PubMed

    Miura, Tsuyoshi; Nakashima, Kosuke; Tada, Norihiro; Itoh, Akichika

    2011-02-14

    Oxidation of alcohols in the presence of a catalytic amount of fluorous IBX and Oxone as a co-oxidant resulted in the corresponding carbonyl compounds in good to high yields. The fluorous IBX is readily recovered as insoluble fluorous IBA from the reaction mixture by simple filtration, and can be reused without significant loss of the catalytic activity.

  7. Microscale Synthesis of Chiral Alcohols via Asymmetric Catalytic Transfer Hydrogenation

    ERIC Educational Resources Information Center

    Peeters, Christine M.; Deliever, Rik; De Vos, Dirk

    2009-01-01

    Synthesis of pure enantiomers is a key issue in industry, especially in areas connected to life sciences. Catalytic asymmetric synthesis has emerged as a powerful and practical tool. Here we describe an experiment on racemic reduction and asymmetric reduction via a catalytic hydrogen transfer process. Acetophenone and substituted acetophenones are…

  8. [Study on catalytic oxidation of benzene by microwave heating].

    PubMed

    Zhang, Yu-cai; Bo, Long-li; Wang, Xiao-hui; Liu, Hai-nan; Zhang, Hao

    2012-08-01

    The performance in catalytic oxidation of benzene was investigated in two different heating modes, microwave heating and conventional electric furnace heating. The effects of copper (Cu)-manganese (Mn) mass ratio, doping dose of cerium (Ce) and calcination temperature on the catalytic activity of Cu-Mn-Ce/molecular sieve catalyst were also checked in catalytic oxidation of benzene with microwave heating, and the catalysts were subsequently characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the catalyst had better catalytic activity for the oxidation of benzene under microwave heating than electric furnace heating, and high oxidation efficiency for benzene was reached due to the "local hot spots" and dipole polarization effect of microwave and stable bed reaction temperature. Under the conditions of Cu, Mn and Ce mass ratio 1:1:0.33 and calcination temperature 500 degrees C, the catalyst had the optimal catalytic activity for benzene oxidation, and its light-off temperature and complete combustion temperature were 165 degrees C and 230 degrees C, respectively. It was indicated by characteristics of XRD and SEM that the presence of copper and manganese oxides and Cu1.5Mn1.5O4 with spinel crystal improved the catalytic activity of the catalyst, and the doping of Ce promoted the dispersion and regularization of active components. High calcination temperature led to the sintering of the catalyst surface and agglomeration of active components, which decreased the catalytic activity of the catalyst in the catalytic oxidation

  9. Catalytic arene hydrogenation using early transition metal hydride compounds

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d[sup 0]-metal hydride compounds, and stoichiometric reactivity of d[sup 0] metal hydrido, aryloxide compounds. (DLC)

  10. Computer model of catalytic combustion/Stirling engine heater head

    NASA Technical Reports Server (NTRS)

    Chu, E. K.; Chang, R. L.; Tong, H.

    1981-01-01

    The basic Acurex HET code was modified to analyze specific problems for Stirling engine heater head applications. Specifically, the code can model: an adiabatic catalytic monolith reactor, an externally cooled catalytic cylindrical reactor/flat plate reactor, a coannular tube radiatively cooled reactor, and a monolithic reactor radiating to upstream and downstream heat exchangers.

  11. Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals

    PubMed Central

    Vats, T.; Dutt, S.; Kumar, R.; Siril, P. F.

    2016-01-01

    Amazing conductivity, perfect honeycomb sp2 arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity. PMID:27619321

  12. Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals.

    PubMed

    Vats, T; Dutt, S; Kumar, R; Siril, P F

    2016-09-13

    Amazing conductivity, perfect honeycomb sp(2) arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity.

  13. Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals

    NASA Astrophysics Data System (ADS)

    Vats, T.; Dutt, S.; Kumar, R.; Siril, P. F.

    2016-09-01

    Amazing conductivity, perfect honeycomb sp2 arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity.

  14. Fabrication of Au–Pd nanoparticles/graphene oxide and their excellent catalytic performance

    SciTech Connect

    He, Yongqiang; Zhang, Nana; Zhang, Lei; Gong, Qiaojuan; Yi, Maocong; Wang, Wei; Qiu, Haixia; Gao, Jianping

    2014-03-01

    Graphical abstract: - Highlights: • Au and Pd nanoparticles loaded on GO were fabricated without adding any reducing agents. • The Au–Pd NPs/GO were excellent catalysts for the reduction of 4-nitrophenol. • The Au–Pd NPs/GO showed superior catalytic activity for the Suzuki reaction. • The Au–Pd NPs/GO exhibit good reusability. - Abstract: A simple method to fabricate clean Au–Pd nanoparticles on graphene oxide (Au–Pd NPs/GO) without using any reducing agent or surfactant has been developed. GO simultaneously reduced the Au and Pd precursors to form a stable suspension of the Au–Pd NPs/GO. The nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and inductively coupled plasma. The Au–Pd NPs/GO exhibited catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol and for the Suzuki–Miyaura coupling reaction of chlorobenzene and phenylboronic acid in aqueous media.

  15. Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals.

    PubMed

    Vats, T; Dutt, S; Kumar, R; Siril, P F

    2016-01-01

    Amazing conductivity, perfect honeycomb sp(2) arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity. PMID:27619321

  16. The Work-Centered Couple.

    ERIC Educational Resources Information Center

    Sperry, Len; Carlson, Jon

    1991-01-01

    Sketches taxonomy of work-centered couple. Briefly describes five couple types: the dual-career couple, the commuting couple, the military couple, the executive couple, and the family business couple. Notes that issues of work and career can greatly impact the lives of these couples. Encourages family psychology to further explore this area of…

  17. Catalytic Domain Architecture of Metzincin Metalloproteases*

    PubMed Central

    Gomis-Rüth, F. Xavier

    2009-01-01

    Metalloproteases cleave proteins and peptides, and deregulation of their function leads to pathology. An understanding of their structure and mechanisms of action is necessary to the development of strategies for their regulation. Among metallopeptidases are the metzincins, which are mostly multidomain proteins with ∼130–260-residue globular catalytic domains showing a common core architecture characterized by a long zinc-binding consensus motif, HEXXHXXGXX(H/D), and a methionine-containing Met-turn. Metzincins participate in unspecific protein degradation such as digestion of intake proteins and tissue development, maintenance, and remodeling, but they are also involved in highly specific cleavage events to activate or inactivate themselves or other (pro)enzymes and bioactive peptides. Metzincins are subdivided into families, and seven such families have been analyzed at the structural level: the astacins, ADAMs/adamalysins/reprolysins, serralysins, matrix metalloproteinases, snapalysins, leishmanolysins, and pappalysins. These families are reviewed from a structural point of view. PMID:19201757

  18. Make the most of catalytic hydrogenations

    SciTech Connect

    Landert, J.P.; Scubla, T.

    1995-03-01

    Liquid-phase catalytic hydrogenation is one of the most useful and versatile reactions available for organic synthesis. Because it is environmentally clean, it has replaced other reduction processes, such as the Bechamp reaction, and zinc and sulfide reductions. Moreover, the economics are favorable, provided that raw materials free of catalyst poisons are used. The hydrogenation reaction is very selective with appropriate catalysts and can often be carried out without a solvent. Applications include reduction of unsaturated carbon compounds to saturated derivatives (for example, in vegetable-oil processing), carbonyl compounds to alcohols (such as sorbitol), and nitrocompounds to amines. the reactions are usually run in batch reactors to rapidly reach complete conversion and allow quick change-over of products. The paper describes the basics of hydrogenation; steering clear of process hazards; scale-up and optimization; and system design in practice.

  19. Infrared and catalytic burner technology assessment

    NASA Astrophysics Data System (ADS)

    Kesselring, J. P.; Krill, W. V.; Schreiber, R. J.

    1981-02-01

    A review of the state of the art in infrared and catalytic burner development shows that four basic types of IR burners are currently in use. Eight commercial and/or residential appliances were characterized to assess the applicability of these burners. The refractory monolith tile and the fiber matrix burners appear most applicable for appliance use. Conceptual designs for the eight appliances with IR burners were prepared to evaluate the technical feasibility. These appliances are shown to have significant fuel efficiency increase and NOx and CO emission reduction benefits. Four appliances -- the commercial rangetop, deep fat fryer, commercial water heater, and warm air furnance -- also appear economically competitive, and recommended approaches for further development are presented. Lists of IR burner literature and patents are also presented.

  20. Catalytic control over supramolecular gel formation

    NASA Astrophysics Data System (ADS)

    Boekhoven, Job; Poolman, Jos M.; Maity, Chandan; Li, Feng; van der Mee, Lars; Minkenberg, Christophe B.; Mendes, Eduardo; van Esch, Jan H.; Eelkema, Rienk

    2013-05-01

    Low-molecular-weight gels show great potential for application in fields ranging from the petrochemical industry to healthcare and tissue engineering. These supramolecular gels are often metastable materials, which implies that their properties are, at least partially, kinetically controlled. Here we show how the mechanical properties and structure of these materials can be controlled directly by catalytic action. We show how in situ catalysis of the formation of gelator molecules can be used to accelerate the formation of supramolecular hydrogels, which drastically enhances their resulting mechanical properties. Using acid or nucleophilic aniline catalysis, it is possible to make supramolecular hydrogels with tunable gel-strength in a matter of minutes, under ambient conditions, starting from simple soluble building blocks. By changing the rate of formation of the gelator molecules using a catalyst, the overall rate of gelation and the resulting gel morphology are affected, which provides access to metastable gel states with improved mechanical strength and appearance despite an identical gelator composition.

  1. Propulsion Mechanism of Catalytic Microjet Engines.

    PubMed

    Fomin, Vladimir M; Hippler, Markus; Magdanz, Veronika; Soler, Lluís; Sanchez, Samuel; Schmidt, Oliver G

    2014-02-01

    We describe the propulsion mechanism of the catalytic microjet engines that are fabricated using rolled-up nanotech. Microjets have recently shown numerous potential applications in nanorobotics but currently there is a lack of an accurate theoretical model that describes the origin of the motion as well as the mechanism of self-propulsion. The geometric asymmetry of a tubular microjet leads to the development of a capillary force, which tends to propel a bubble toward the larger opening of the tube. Because of this motion in an asymmetric tube, there emerges a momentum transfer to the fluid. In order to compensate this momentum transfer, a jet force acting on the tube occurs. This force, which is counterbalanced by the linear drag force, enables tube velocities of the order of 100 μm/s. This mechanism provides a fundamental explanation for the development of driving forces that are acting on bubbles in tubular microjets. PMID:25177214

  2. Catalytic cartridge SO.sub.3 decomposer

    DOEpatents

    Galloway, Terry R.

    1982-01-01

    A catalytic cartridge internally heated is utilized as a SO.sub.3 decomposer for thermochemical hydrogen production. The cartridge has two embodiments, a cross-flow cartridge and an axial flow cartridge. In the cross-flow cartridge, SO.sub.3 gas is flowed through a chamber and incident normally to a catalyst coated tube extending through the chamber, the catalyst coated tube being internally heated. In the axial-flow cartridge, SO.sub.3 gas is flowed through the annular space between concentric inner and outer cylindrical walls, the inner cylindrical wall being coated by a catalyst and being internally heated. The modular cartridge decomposer provides high thermal efficiency, high conversion efficiency, and increased safety.

  3. Catalytic cartridge SO.sub.3 decomposer

    DOEpatents

    Galloway, Terry R.

    1982-01-01

    A catalytic cartridge surrounding a heat pipe driven by a heat source is utilized as a SO.sub.3 decomposer for thermochemical hydrogen production. The cartridge has two embodiments, a cross-flow cartridge and an axial flow cartridge. In the cross-flow cartridge, SO.sub.3 gas is flowed through a chamber and incident normally to a catalyst coated tube extending through the chamber, the catalyst coated tube surrounding the heat pipe. In the axial-flow cartridge, SO.sub.3 gas is flowed through the annular space between concentric inner and outer cylindrical walls, the inner cylindrical wall being coated by a catalyst and surrounding the heat pipe. The modular cartridge decomposer provides high thermal efficiency, high conversion efficiency, and increased safety.

  4. Biofuel from fast pyrolysis and catalytic hydrodeoxygenation.

    SciTech Connect

    Elliott, Douglas C.

    2015-09-04

    This review addresses recent developments in biomass fast pyrolysis bio-oil upgrading by catalytic hydrotreating. The research in the field has expanded dramatically in the past few years with numerous new research groups entering the field while existing efforts from others expand. The issues revolve around the catalyst formulation and operating conditions. Much work in batch reactor tests with precious metal catalysts needs further validation to verify long-term operability in continuous flow systems. The effect of the low level of sulfur in bio-oil needs more study to be better understood. Utilization of the upgraded bio-oil for feedstock to finished fuels is still in an early stage of understanding.

  5. Tuning the Catalytic Activity of Subcellular Nanoreactors.

    PubMed

    Jakobson, Christopher M; Chen, Yiqun; Slininger, Marilyn F; Valdivia, Elias; Kim, Edward Y; Tullman-Ercek, Danielle

    2016-07-31

    Bacterial microcompartments are naturally occurring subcellular organelles of bacteria and serve as a promising scaffold for the organization of heterologous biosynthetic pathways. A critical element in the design of custom biosynthetic organelles is quantitative control over the loading of heterologous enzymes to the interior of the organelles. We demonstrate that the loading of heterologous proteins to the 1,2-propanediol utilization microcompartment of Salmonella enterica can be controlled using two strategies: by modulating the transcriptional activation of the microcompartment container and by coordinating the expression of the microcompartment container and the heterologous cargo. These strategies allow general control over the loading of heterologous proteins localized by two different N-terminal targeting peptides and represent an important step toward tuning the catalytic activity of bacterial microcompartments for increased biosynthetic productivity.

  6. Stoichiometric and catalytic synthesis of alkynylphosphines.

    PubMed

    Bernoud, Elise; Veillard, Romain; Alayrac, Carole; Gaumont, Annie-Claude

    2012-01-01

    Alkynylphosphines or their borane complexes are available either through C-P bond forming reactions or through modification of the phosphorus or the alkynyl function of various alkynyl phosphorus derivatives. The latter strategy, and in particular the one involving phosphoryl reduction by alanes or silanes, is the method of choice for preparing primary and secondary alkynylphosphines, while the former strategy is usually employed for the synthesis of tertiary alkynylphosphines or their borane complexes. The classical C-P bond forming methods rely on the reaction between halophosphines or their borane complexes with terminal acetylenes in the presence of a stoichiometric amount of organometallic bases, which precludes the access to alkynylphosphines bearing sensitive functional groups. In less than a decade, efficient catalytic procedures, mostly involving copper complexes and either an electrophilic or a nucleophilic phosphorus reagent, have emerged. By proceeding under mild conditions, these new methods have allowed a significant broadening of the substituent scope and structure complexity. PMID:23222904

  7. Contact structure for use in catalytic distillation

    DOEpatents

    Jones, Jr., Edward M.

    1985-01-01

    A method and apparatus for conducting catalytic chemical reactions and fractionation of the reaction mixture, comprising and feeding reactants into a distillation column reactor contracting said reactant in a liquid phase with a fixed bed catalyst in the form of a contact catalyst structure, consisting of closed porous containers containing the catalyst for the reaction and a clip means to hold and support said containers, which are disposed above, i.e., on the distillation trays in the tower. The trays have weir means to provide a liquid level on the trays to substantially cover the containers. In other words, the trays function in their ordinary manner with the addition thereto of the catalyst. The reaction mixture is concurrently fractionated in the column.

  8. Contact structure for use in catalytic distillation

    DOEpatents

    Jones, E.M. Jr.

    1985-08-20

    A method and apparatus are disclosed for conducting catalytic chemical reactions and fractionation of the reaction mixture, comprising and feeding reactants into a distillation column reactor contracting said reactant in a liquid phase with a fixed bed catalyst in the form of a contact catalyst structure, consisting of closed porous containers containing the catalyst for the reaction and a clip means to hold and support said containers, which are disposed above, i.e., on the distillation trays in the tower. The trays have weir means to provide a liquid level on the trays to substantially cover the containers. In other words, the trays function in their ordinary manner with the addition thereto of the catalyst. The reaction mixture is concurrently fractionated in the column. 7 figs.

  9. Contact structure for use in catalytic distillation

    DOEpatents

    Jones, Jr., Edward M.

    1984-01-01

    A method for conducting catalytic chemical reactions and fractionation of the reaction mixture comprising feeding reactants into a distillation column reactor contracting said reactant in liquid phase with a fixed bed catalyst in the form of a contact catalyst structure consisting of closed porous containers containing the catatlyst for the reaction and a clip means to hold and support said containers, which are disposed above, i.e., on the distillation trays in the tower. The trays have weir means to provide a liquid level on the trays to substantially cover the containers. In other words, the trays function in their ordinary manner with the addition thereto of the catalyst. The reaction mixture is concurrently fractionated in the column.

  10. Contact structure for use in catalytic distillation

    DOEpatents

    Jones, E.M. Jr.

    1984-03-27

    A method is described for conducting catalytic chemical reactions and fractionation of the reaction mixture comprising feeding reactants into a distillation column reactor, contracting said reactant in liquid phase with a fixed bed catalyst in the form of a contact catalyst structure consisting of closed porous containers containing the catalyst for the reaction and a clip means to hold and support said containers, which are disposed above, i.e., on the distillation trays in the tower. The trays have weir means to provide a liquid level on the trays to substantially cover the containers. In other words, the trays function in their ordinary manner with the addition thereto of the catalyst. The reaction mixture is concurrently fractionated in the column. 7 figs.

  11. Catalytic Conia-ene and related reactions.

    PubMed

    Hack, Daniel; Blümel, Marcus; Chauhan, Pankaj; Philipps, Arne R; Enders, Dieter

    2015-10-01

    Since its initial inception, the Conia-ene reaction, known as the intramolecular addition of enols to alkynes or alkenes, has experienced a tremendous development and appealing catalytic protocols have emerged. This review fathoms the underlying mechanistic principles rationalizing how substrate design, substrate activation, and the nature of the catalyst work hand in hand for the efficient synthesis of carbocycles and heterocycles at mild reaction conditions. Nowadays, Conia-ene reactions can be found as part of tandem reactions, and the road for asymmetric versions has already been paved. Based on their broad applicability, Conia-ene reactions have turned into a highly appreciated synthetic tool with impressive examples in natural product synthesis reported in recent years. PMID:26031492

  12. Catalytic cracking process with vanadium passivation

    SciTech Connect

    Kennedy, J.V.; Jossens, L.W.

    1991-03-26

    This paper discusses a process for the catalytic cracking of metal-containing hydrocarbonaceous feedstock. It comprises contacting the feedstock under cracking conditions with a dual component catalyst composition. The catalyst composition comprises a first component comprising an active cracking catalyst; and a second component, as a separate and distinct entity, the second component comprising the following materials: a calcium and magnesium containing material selected from the group consisting of dolomite, substantially amorphous calcium magnesium silicate, calcium magnesium oxide, calcium magnesium acetate, calcium magnesium carbonate, and calcium magnesium subcarbonate; a magnesium containing material comprising a hydrous magnesium silicate; and a binder selected from the group consisting of kaolin, bentonite, montmorillonite, saponite, hectorite, alumina, silica, titania, zirconia, silica-alumina, and combinations thereof.

  13. Basicity, Catalytic and Adsorptive Properties of Hydrotalcites

    NASA Astrophysics Data System (ADS)

    Figueras, Francois

    Solid bases have numerous potential applications, not only as catalyst for the manufacture of fine chemicals, in refining and petrochemistry, but also for adsorption and anion exchange. The present processes use liquid bases, typically alcoholic potash, and require neutralisation of the reaction medium at the end of the reaction, with production of salts. The substitution of these liquid bases by solids would provide cleaner and safer processes, due to the reduction of salts, and facilitate separation of the products and recycling of the catalyst. This chapter reviews the recent ideas on the modification of the basic properties of hydrotalcites by anion exchange and on the catalytic properties of solid bases as catalysts. Many examples of successful applications are given, with emphasis to industrial processes recently presented such as isomerisation of olefins. The basic properties of hydrotalcites can also be used to carry the exchange of toxic anions, humic acids or dyes, and have driven recent developments proposing HDT as drug carriers.

  14. Soluble organic nanotubes for catalytic systems.

    PubMed

    Xiong, Linfeng; Yang, Kunran; Zhang, Hui; Liao, Xiaojuan; Huang, Kun

    2016-03-18

    In this paper, we report a novel method for constructing a soluble organic nanotube supported catalyst system based on single-molecule templating of core–shell bottlebrush copolymers. Various organic or metal catalysts, such as sodium prop-2-yne-1-sulfonate (SPS), 1-(2-(prop-2-yn-1-yloxy)ethyl)-1H-imidazole (PEI) and Pd(OAc)2 were anchored onto the tube walls to functionalize the organic nanotubes via copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Depending on the 'confined effect' and the accessible cavity microenvironments of tubular structures, the organic nanotube catalysts showed high catalytic efficiency and site-isolation features. We believe that the soluble organic nanotubes will be very useful for the development of high performance catalyst systems due to their high stability of support, facile functionalization and attractive textural properties. PMID:27308672

  15. Catalytic Conia-ene and related reactions.

    PubMed

    Hack, Daniel; Blümel, Marcus; Chauhan, Pankaj; Philipps, Arne R; Enders, Dieter

    2015-10-01

    Since its initial inception, the Conia-ene reaction, known as the intramolecular addition of enols to alkynes or alkenes, has experienced a tremendous development and appealing catalytic protocols have emerged. This review fathoms the underlying mechanistic principles rationalizing how substrate design, substrate activation, and the nature of the catalyst work hand in hand for the efficient synthesis of carbocycles and heterocycles at mild reaction conditions. Nowadays, Conia-ene reactions can be found as part of tandem reactions, and the road for asymmetric versions has already been paved. Based on their broad applicability, Conia-ene reactions have turned into a highly appreciated synthetic tool with impressive examples in natural product synthesis reported in recent years.

  16. Propulsion Mechanism of Catalytic Microjet Engines

    PubMed Central

    Fomin, Vladimir M.; Hippler, Markus; Magdanz, Veronika; Soler, Lluís; Sanchez, Samuel; Schmidt, Oliver G.

    2014-01-01

    We describe the propulsion mechanism of the catalytic microjet engines that are fabricated using rolled-up nanotech. Microjets have recently shown numerous potential applications in nanorobotics but currently there is a lack of an accurate theoretical model that describes the origin of the motion as well as the mechanism of self-propulsion. The geometric asymmetry of a tubular microjet leads to the development of a capillary force, which tends to propel a bubble toward the larger opening of the tube. Because of this motion in an asymmetric tube, there emerges a momentum transfer to the fluid. In order to compensate this momentum transfer, a jet force acting on the tube occurs. This force, which is counterbalanced by the linear drag force, enables tube velocities of the order of 100 μm/s. This mechanism provides a fundamental explanation for the development of driving forces that are acting on bubbles in tubular microjets. PMID:25177214

  17. Catalytic carbon membranes for hydrogen production

    SciTech Connect

    Damle, A.S.; Gangwal, S.K.

    1992-01-01

    Commercial carbon composite microfiltration membranes may be modified for gas separation applications by providing a gas separation layer with pores in the 1- to 10-nm range. Several organic polymeric precursors and techniques for depositing a suitable layer were investigated in this project. The in situ polymerization technique was found to be the most promising, and pure component permeation tests with membrane samples prepared with this technique indicated Knudsen diffusion behavior. The gas separation factors obtained by mixed-gas permeation tests were found to depend strongly on gas temperature and pressure indicating significant viscous flow at high-pressure conditions. The modified membranes were used to carry out simultaneous water gas shift reaction and product hydrogen separation. These tests indicated increasing CO conversions with increasing hydrogen separation. A simple process model was developed to simulate a catalytic membrane reactor. A number of simulations were carried out to identify operating conditions leading to product hydrogen concentrations over 90 percent. (VC)

  18. Simulation of catalytic oxidation and selective catalytic NOx reduction in lean-exhaust hybrid vehicles

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Chakravarthy, Veerathu K

    2012-01-01

    We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel powered hybrid vehicles. The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust. Our results illustrate the potential impact of DOC and SCR interactions for lean hybrid electric and plug-in hybrid electric vehicles.

  19. Nonequilibrium Relaxation of Conformational Dynamics Facilitates Catalytic Reaction in an Elastic Network Model of T7 DNA Polymerase.

    PubMed

    Zhao, Ziqing W; Xie, X Sunney; Ge, Hao

    2016-03-24

    Nucleotide-induced conformational closing of the finger domain of DNA polymerase is crucial for its catalytic action during DNA replication. Such large-amplitude molecular motion is often not fully accessible to either direct experimental monitoring or molecular dynamics simulations. However, a coarse-grained model can offer an informative alternative, especially for probing the relationship between conformational dynamics and catalysis. Here we investigate the dynamics of T7 DNA polymerase catalysis using a Langevin-type elastic network model incorporating detailed structural information on the open conformation without the substrate bound. Such a single-parameter model remarkably captures the induced conformational dynamics of DNA polymerase upon dNTP binding, and reveals its close coupling to the advancement toward transition state along the coordinate of the target reaction, which contributes to significant lowering of the activation energy barrier. Furthermore, analysis of stochastic catalytic rates suggests that when the activation energy barrier has already been significantly lowered and nonequilibrium relaxation toward the closed form dominates the catalytic rate, one must appeal to a picture of two-dimensional free energy surface in order to account for the full spectrum of catalytic modes. Our semiquantitative study illustrates the general role of conformational dynamics in achieving transition-state stabilization, and suggests that such an elastic network model, albeit simplified, possesses the potential to furnish significant mechanistic insights into the functioning of a variety of enzymatic systems.

  20. Functional Association of Catalytic and Ancillary Modules Dictates Enzymatic Activity in Glycoside Hydrolase Family 43 β-Xylosidase*

    PubMed Central

    Moraïs, Sarah; Salama-Alber, Orly; Barak, Yoav; Hadar, Yitzhak; Wilson, David B.; Lamed, Raphael; Shoham, Yuval; Bayer, Edward A.

    2012-01-01

    β-Xylosidases are hemicellulases that hydrolyze short xylo-oligosaccharides into xylose units, thus complementing endoxylanase degradation of the hemicellulose component of lignocellulosic substrates. Here, we describe the cloning, characterization, and kinetic analysis of a glycoside hydrolase family 43 β-xylosidase (Xyl43A) from the aerobic cellulolytic bacterium, Thermobifida fusca. Temperature and pH optima of 55–60 °C and 5.5–6, respectively, were determined. The apparent Km value was 0.55 mm, using p-nitrophenyl xylopyranoside as substrate, and the catalytic constant (kcat) was 6.72 s−1. T. fusca Xyl43A contains a catalytic module at the N terminus and an ancillary module (termed herein as Module-A) of undefined function at the C terminus. We expressed the two recombinant modules independently in Escherichia coli and examined their remaining catalytic activity and binding properties. The separation of the two Xyl43A modules caused the complete loss of enzymatic activity, whereas potent binding to xylan was fully maintained in the catalytic module and partially in the ancillary Module-A. Nondenaturing gel electrophoresis revealed a specific noncovalent coupling of the two modules, thereby restoring enzymatic activity to 66.7% (relative to the wild-type enzyme). Module-A contributes a phenylalanine residue that functions as an essential part of the active site, and the two juxtaposed modules function as a single functional entity. PMID:22270362

  1. The Structure of the Catalytic Domain of a Plant Cellulose Synthase and Its Assembly into Dimers[C][W][OPEN

    PubMed Central

    Olek, Anna T.; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N.; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; Himmel, Michael E.; Bolin, Jeffrey T.; Carpita, Nicholas C.

    2014-01-01

    Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. The arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize. PMID:25012190

  2. Ni-Catalyzed Dehydrogenative Cross-Coupling: Direct Transformation of Aldehydes to Esters and Amides

    PubMed Central

    Whittaker, Aaron M.; Dong, Vy M.

    2015-01-01

    By exploring a new mode of Ni-catalyzed cross-coupling, we have developed a protocol to transform both aromatic and aliphatic aldehydes into either esters or amides directly. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, including the use of either α,α,α-trifluoroacetophenone or excess aldehyde. We present mechanistic data that supports a catalytic cycle involving oxidative addition into the aldehyde C–H bond. PMID:25424967

  3. Nickel-catalyzed dehydrogenative cross-coupling: direct transformation of aldehydes into esters and amides.

    PubMed

    Whittaker, Aaron M; Dong, Vy M

    2015-01-19

    By exploring a new mode of nickel-catalyzed cross-coupling, a method to directly transform both aromatic and aliphatic aldehydes into either esters or amides has been developed. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, including the use of either α,α,α-trifluoroacetophenone or excess aldehyde. Mechanistic data that supports a catalytic cycle involving oxidative addition into the aldehyde C-H bond is also presented. PMID:25424967

  4. Copper nanoparticle-catalyzed cross-coupling of alkyl halides with Grignard reagents.

    PubMed

    Kim, Ju Hyun; Chung, Young Keun

    2013-12-01

    A cross-coupling reaction between alkyl bromides and chlorides and various Grignard reagents was carried out in the presence of commercially available copper or copper oxide nanoparticles as a catalyst and an alkyne additive. The catalytic system shows high activity, a broad scope, and good functional group tolerance. PMID:24146018

  5. Biorhythm in Couple Counseling

    ERIC Educational Resources Information Center

    Araoz, Daniel L.

    1977-01-01

    Twelve couples in marital counseling were studied during 12 months on the basis of their biorhythms. For each couple a compatibility percentage was obtained. It was found that difficulties in their interaction correlated highly with dissonance in their biorhythms. (Author)

  6. Catalytic production of methyl acrylates by gold-mediated cross coupling of unsaturated aldehydes with methanol

    NASA Astrophysics Data System (ADS)

    Karakalos, Stavros; Zugic, Branko; Stowers, Kara J.; Biener, Monika M.; Biener, Juergen; Friend, Cynthia M.; Madix, Robert J.

    2016-10-01

    Modern methods of esterification, one of the most important reactions in organic synthesis, are reaching their limits, as far as waste and expense are concerned. Novel chemical approaches to ester formation are therefore of importance. Here we report a simple procedure free of caustic reagents or byproducts for the facile direct oxidative methyl esterification of aldehydes over nanoporous Au catalysts. Complementary model studies on single crystal gold surfaces establish the fundamental reactions involved. We find that methanol more readily reacts with adsorbed active oxygen than do the aldehydes, but that once the aldehydes do react, they form strongly-bound acrylates that block reactive sites and decrease the yields of acrylic esters under steady flow conditions at 420 K. Significant improvements in yield can be achieved by operating at higher temperatures, which render the site-blocking acrylates unstable.

  7. In Vivo Evolution of a Catalytic RNA Couples Trans-Splicing to Translation

    PubMed Central

    Olson, Karen E.; Dolan, Gregory F.; Müller, Ulrich F.

    2014-01-01

    How does a non-coding RNA evolve in cells? To address this question experimentally we evolved a trans-splicing variant of the group I intron ribozyme from Tetrahymena over 21 cycles of evolution in E.coli cells. Sequence variation was introduced during the evolution by mutagenic and recombinative PCR, and increasingly active ribozymes were selected by their repair of an mRNA mediating antibiotic resistance. The most efficient ribozyme contained four clustered mutations that were necessary and sufficient for maximum activity in cells. Surprisingly, these mutations did not increase the trans-splicing activity of the ribozyme. Instead, they appear to have recruited a cellular protein, the transcription termination factor Rho, and facilitated more efficient translation of the ribozyme’s trans-splicing product. In addition, these mutations affected the expression of several other, unrelated genes. These results suggest that during RNA evolution in cells, four mutations can be sufficient to evolve new protein interactions, and four mutations in an RNA molecule can generate a large effect on gene regulation in the cell. PMID:24466112

  8. Bio oil synthesis by coupling biological biomass pretreatment and catalytic hydroliquefaction process.

    PubMed

    Hamieh, S; Beauchet, R; Lemee, L; Toufaily, J; Koubaissy, B; Hamieh, T; Pouilloux, Y; Pinard, L

    2014-03-01

    The bio-oil synthesis from a mixture of wastes (7wt.% straw, 38wt.% wood, and 45wt.% grass) was carried out by direct liquefaction reaction using Raney Nickel as catalyst and tetralin as solvent. The green wastes were biologically degraded during 3 months. Longer the destructuration time; higher the yield into oil is. Biological pretreatment of green wastes promotes the liquefaction process. Among the components of degraded biomass, Humin, the major fraction (60-80wt.%) that was favored by the biological treatment, yields to a bio oil extremely energetic with a HHV close to biopetroleum (40MJ kg(-1)), contrariwise, Fulvic acids (2-12wt.%), the minor fraction is refractory to liquefaction reaction.

  9. Studies of coupled chemical and catalytic coal conversion methods. Ninth quarterly report, October, November, December 1989

    SciTech Connect

    Stock, L.M.

    1989-12-31

    A new base catalyzed C-alkylation reaction that employs a mixture of n-butyllithium and potassium t-butoxide in refluxing heptane to produce coal anions that are subsequently treated with n-alkyl halides at 0{degree}C has been developed. Almost quantitative pyridine solubilization was achieved by C-octylation of a Lower Kittanning coal, PSOC 1197. C-Octylation was less successful for the solubilization of bituminous Illinois No. 6 coal, APCSP 3, and subbituminous Wyodak coal, APCSP 2, which gave 35 and 33% soluble material, respectively. Their O-methyl derivatives yielded 43 and 20% soluble material in the same reaction. The observations are in accord with the concept of Ouchi and his associates that higher rank coals, although more aromatic in character, have a lower degree of polymerization than low rank coals. Relatively mild chemical reactions, such as Calkylation, that lead to modest changes in molecular dimensions, can disrupt intermolecular forces and accomplish solubilization.

  10. Cu-based Polyoxometalate Catalyst for Efficient Catalytic Hydrogen Evolution.

    PubMed

    Lv, Hongjin; Gao, Yuanzhe; Guo, Weiwei; Lauinger, Sarah M; Chi, Yingnan; Bacsa, John; Sullivan, Kevin P; Wieliczko, Marika; Musaev, Djamaladdin G; Hill, Craig L

    2016-07-01

    Copper-based complexes have been largely neglected as potential water reduction catalysts. This article reports the synthesis and characterization of a tetra-copper-containing polyoxotungstate, Na3K7[Cu4(H2O)2(B-α-PW9O34)2]·30H2O (Na3K7-Cu4P2). Cu4P2 is a water-compatible catalyst for efficient visible-light-driven hydrogen evolution when coupled to (4,4'-di-tert-butyl-2,2'-dipyridyl)-bis(2-phenylpyridine(1H))-iridium(III) hexafluorophosphate ([Ir(ppy)2(dtbbpy)][PF6]) as a light absorber and triethanolamine (TEOA) as sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of ∼1270 per Cu4P2 catalyst is obtained after 5 h of irradiation (light-emitting diode; λ = 455 nm; 20 mW); a photochemical quantum efficiency of as high as 15.9% is achieved. Both oxidative and reductive quenching pathways are observed by measuring the luminescence intensity of excited state [Ir(ppy)2(dtbbpy)](+*) in the presence of Cu4P2 or TEOA, respectively. Many stability studies (e.g., UV-vis absorption, FT-IR, dynamic light scattering, transmission electron microscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy) show that catalyst Cu4P2 undergoes slow decomposition under turnover conditions; however, both the starting Cu4P2 as well as its molecular decomposition products are the dominant catalytically active species for H2 evolution not Cu or CuOx particles. Considering the high abundance and low cost of copper, the present work provides considerations for the design and synthesis of efficient, molecular, water-compatible Cu-based water reduction catalysts. PMID:27322394

  11. Orion EFT-1 Catalytic Tile Experiment Overview and Flight Measurements

    NASA Technical Reports Server (NTRS)

    Salazar, Giovanni; Amar, Adam; Hyatt, Andrew; Rezin, Marc D.

    2016-01-01

    This paper describes the design and results of a surface catalysis flight experiment flown on the Orion Multipurpose Crew Vehicle during Exploration Flight Test 1 (EFT1). Similar to previous Space Shuttle catalytic tile experiments, the present test consisted of a highly catalytic coating applied to an instrumented TPS tile. However, the present catalytic tile experiment contained significantly more instrumentation in order to better resolve the heating overshoot caused by the change in surface catalytic efficiency at the interface between two distinct materials. In addition to collecting data with unprecedented spatial resolution of the "overshoot" phenomenon, the experiment was also designed to prove if such a catalytic overshoot would be seen in turbulent flow in high enthalpy regimes. A detailed discussion of the results obtained during EFT1 is presented, as well as the challenges associated with data interpretation of this experiment. Results of material testing carried out in support of this flight experiment are also shown. Finally, an inverse heat conduction technique is employed to reconstruct the flight environments at locations upstream and along the catalytic coating. The data and analysis presented in this work will greatly contribute to our understanding of the catalytic "overshoot" phenomenon, and have a significant impact on the design of future spacecraft.

  12. Synthesis of DMF-protected Au NPs with different size distributions and their catalytic performance in the Ullmann homocoupling of aryl iodides.

    PubMed

    Yao, Wang; Gong, Wei-Jie; Li, Hong-Xi; Li, Fei-Long; Gao, Jun; Lang, Jian-Ping

    2014-11-14

    DMF-stabilized Au nanoparticles (NPs) with three different particle sizes were prepared by controlling the reaction temperatures and times. In the absence of any additional ligands, these Au NPs showed high catalytic activity in the Ullmann homocoupling of aryl iodides in DMF. The effects of Au particle size on the coupling reaction were investigated by the use of three Au catalysts with mean particle sizes of ca. 1.0 nm, 2.5 nm, and 5.5 nm, respectively. The catalytic activity of the Au NPs was found to be in the order of Au (2.5 nm) > Au (<1.0 nm) > Au (5.5 nm), indicating that surface Au atoms do not have the same catalytic activity toward such a homocoupling reaction.

  13. Pyridoxal-5'-phosphate-dependent catalytic antibodies.

    PubMed

    Gramatikova, Svetlana; Mouratou, Barbara; Stetefeld, Jörg; Mehta, Perdeep K; Christen, Philipp

    2002-11-01

    Strategies for expanding the catalytic scope of antibodies include the incorporation of inorganic or organic cofactors into their binding sites. An obvious choice is pyridoxal-5'-phosphate (PLP), which is probably the most versatile organic cofactor of enzymes. Monoclonal antibodies against the hapten N(alpha)-(5'-phosphopyridoxyl)-L-lysine, a stable analog of the covalent coenzyme-substrate adducts were screened by a competition ELISA for binding of the PLP-amino acid Schiff base adduct. The Schiff base with its C4'-N alpha double bond is, in contrast to the hapten, a planar compound and is an obligatory intermediate in all PLP-dependent reactions of amino acids. This highly discriminating screening step eliminated all but 5 of 24 hapten-binding antibodies. The five remaining antibodies were tested for catalysis of the PLP-dependent alpha,beta-elimination reaction of beta-chloroalanine. Antibody 15A9 complied with this selection criterion and catalyzed in addition the cofactor-dependent transamination reaction of hydrophobic D-amino acids and oxo acids (k(cat)'=0.42 min(-1) with D-alanine at 25 degrees C). Homology modeling together with alanine scanning yielded a 3D model of Fab 15A9. The striking analogy between antibody 15A9 and PLP-dependent enzymes includes the following features: (1) The binding sites accommodate the planar coenzyme-amino acid adduct. (2) The bond at C alpha to be broken lies together with the C alpha-N bond in a plane orthogonal to the plane of coenzyme and imine bond. (3) The alpha-carboxylate group of the substrate is bound by an arginine residue. (4) The coenzyme-substrate adduct assumes a cisoid conformation. (5) PLP markedly contributes to catalytic efficiency, being a 10(4) times more efficient amino group acceptor than pyruvate. The protein moiety, however, ensures reaction as well as substrate specificity, and further accelerates the reaction (in 15A9 k(cat (Ab x PLP))'/k(cat (PLP))'=5 x 10(3)). The analogies of antibody 15A9 with

  14. Synergize fuel and petrochemical processing plans with catalytic reforming

    SciTech Connect

    1997-03-01

    Depending on the market, refiner`s plans to produce clean fuels and higher value petrochemicals will weigh heavily on the catalytic reformer`s flexibility. It seems that as soon as a timely article related to catalytic reforming operations is published, a new {open_quotes}boutique{close_quotes} gasoline fuel specification is slapped on to existing fuel standards, affecting reformer operations and processing objectives. Just as importantly, the petrochemical market (such as aromatics) that refiners are targeting, can be very fickle. That`s why process engineers have endeavored to maintain an awareness of the flexibility that technology suppliers are building into modern catalytic reformers.

  15. Design of Catalytically Amplified Sensors for Small Molecules

    PubMed Central

    Makhlynets, Olga V.; Korendovych, Ivan V.

    2014-01-01

    Catalytically amplified sensors link an allosteric analyte binding site with a reactive site to catalytically convert substrate into colored or fluorescent product that can be easily measured. Such an arrangement greatly improves a sensor’s detection limit as illustrated by successful application of ELISA-based approaches. The ability to engineer synthetic catalytic sites into non-enzymatic proteins expands the repertoire of analytes as well as readout reactions. Here we review recent examples of small molecule sensors based on allosterically controlled enzymes and organometallic catalysts. The focus of this paper is on biocompatible, switchable enzymes regulated by small molecules to track analytes both in vivo and in the environment. PMID:24970222

  16. Controlled synthesis of porous platinum nanostructures for catalytic applications.

    PubMed

    Cao, Yanqin; Zhang, Junwei; Yang, Yong; Huang, Zhengren; Long, Nguyen Viet; Nogami, Masayuki

    2014-02-01

    Porous platinum, that has outstanding catalytic and electrical properties and superior resistant characteristics to corrosion, has been widely applied in chemical, petrochemical, pharmaceutical, electronic, and automotive industries. As the catalytic activity and selectivity depend on the size, shape and structure of nanomaterials, the strategies for controlling these factors of platinum nanomaterials to get excellent catalytic properties are discussed. Here, recent advances in the design and preparation of various porous platinum nanostructures are reviewed, including wet-chemical synthesis, electro-deposition, galvanic replacement reaction and de-alloying technology. The applications of various platinum nanostructures are also discussed, especially in fuel cells. PMID:24749422

  17. Enhanced performance of supported HfO2 counter electrodes for redox couples used in dye-sensitized solar cells.

    PubMed

    Yun, Sining; Pu, Haihui; Chen, Junhong; Hagfeldt, Anders; Ma, Tingli

    2014-02-01

    Mesoporous-graphitic-carbon-supported HfO2 (HfO2 -MGC) nanohybrids were synthesized by using a soft-template route. Characterization and a systematic investigation of the catalytic properties, stability, and catalytic mechanism were performed for HfO2 -MGC counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The new HfO2 -MGC as a CE in DSSCs showed a surprisingly high efficiency of 7.75 % for the triiodide/iodide redox couple and 3.69 % for the disulfide/thiolate redox couple, greater than the Pt electrode in the corresponding electrolyte system, which opens up a possibility for its practical application.

  18. Correlation resonance generated by coupled enzymatic processing.

    PubMed

    Mather, William H; Cookson, Natalie A; Hasty, Jeff; Tsimring, Lev S; Williams, Ruth J

    2010-11-17

    A major challenge for systems biology is to deduce the molecular interactions that underlie correlations observed between concentrations of different intracellular molecules. Although direct explanations such as coupled transcription or direct protein-protein interactions are often considered, potential indirect sources of coupling have received much less attention. Here we show how correlations can arise generically from a posttranslational coupling mechanism involving the processing of multiple protein species by a common enzyme. By observing a connection between a stochastic model and a multiclass queue, we obtain a closed form expression for the steady-state distribution of the numbers of molecules of each protein species. Upon deriving explicit analytic expressions for moments and correlations associated with this distribution, we discover a striking phenomenon that we call correlation resonance: for small dilution rate, correlations peak near the balance-point where the total rate of influx of proteins into the system is equal to the maximum processing capacity of the enzyme. Given the limited number of many important catalytic molecules, our results may lead to new insights into the origin of correlated behavior on a global scale.

  19. Study of the dynamics of the MoO2-Mo2C system for catalytic partial oxidation reactions

    NASA Astrophysics Data System (ADS)

    Cuba Torres, Christian Martin

    On a global scale, the energy demand is largely supplied by the combustion of non-renewable fossil fuels. However, their rapid depletion coupled with environmental and sustainability concerns are the main drivers to seek for alternative energetic strategies. To this end, the sustainable generation of hydrogen from renewable resources such as biodiesel would represent an attractive alternative solution to fossil fuels. Furthermore, hydrogen's lower environmental impact and greater independence from foreign control make it a strong contender for solving this global problem. Among a wide variety of methods for hydrogen production, the catalytic partial oxidation offers numerous advantages for compact and mobile fuel processing systems. For this reaction, the present work explores the versatility of the Mo--O--C catalytic system under different synthesis methods and reforming conditions using methyl oleate as a surrogate biodiesel. MoO2 exhibits good catalytic activity and exhibits high coke-resistance even under reforming conditions where long-chain oxygenated compounds are prone to form coke. Moreover, the lattice oxygen present in MoO2 promotes the Mars-Van Krevelen mechanism. Also, it is introduced a novel beta-Mo2C synthesis by the in-situ formation method that does not utilize external H2 inputs. Herein, the MoO 2/Mo2C system maintains high catalytic activity for partial oxidation while the lattice oxygen serves as a carbon buffer for preventing coke formation. This unique feature allows for longer operation reforming times despite slightly lower catalytic activity compared to the catalysts prepared by the traditional temperature-programmed reaction method. Moreover, it is demonstrated by a pulse reaction technique that during the phase transformation of MoO2 to beta-Mo2C, the formation of Mo metal as an intermediate is not responsible for the sintering of the material wrongly assumed by the temperature-programmed method.

  20. Enhancing catalytic performance of palladium in gold and palladium alloy nanoparticles for organic synthesis reactions through visible light irradiation at ambient temperatures.

    PubMed

    Sarina, Sarina; Zhu, Huaiyong; Jaatinen, Esa; Xiao, Qi; Liu, Hongwei; Jia, Jianfeng; Chen, Chao; Zhao, Jian

    2013-04-17

    The intrinsic catalytic activity of palladium (Pd) is significantly enhanced in gold (Au)-Pd alloy nanoparticles (NPs) under visible light irradiation at ambient temperatures. The alloy NPs strongly absorb light and efficiently enhance the conversion of several reactions, including Suzuki-Miyaura cross coupling, oxidative addition of benzylamine, selective oxidation of aromatic alcohols to corresponding aldehydes and ketones, and phenol oxidation. The Au/Pd molar ratio of the alloy NPs has an important impact on performance of the catalysts since it determines both the electronic heterogeneity and the distribution of Pd sites at the NP surface, with these two factors playing key roles in the catalytic activity. Irradiating with light produces an even more profound enhancement in the catalytic performance of the NPs. For example, the best conversion rate achieved thermally at 30 °C for Suzuki-Miyaura cross coupling was 37% at a Au/Pd ratio of 1:1.86, while under light illumination the yield increased to 96% under the same conditions. The catalytic activity of the alloy NPs depends on the intensity and wavelength of incident light. Light absorption due to the Localized Surface Plasmon Resonance of gold nanocrystals plays an important role in enhancing catalyst performance. We believe that the conduction electrons of the NPs gain the light absorbed energy producing energetic electrons at the surface Pd sites, which enhances the sites' intrinsic catalytic ability. These findings provide useful guidelines for designing efficient catalysts composed of alloys of a plasmonic metal and a catalytically active transition metal for various organic syntheses driven by sunlight.

  1. Enhancing catalytic performance of palladium in gold and palladium alloy nanoparticles for organic synthesis reactions through visible light irradiation at ambient temperatures.

    PubMed

    Sarina, Sarina; Zhu, Huaiyong; Jaatinen, Esa; Xiao, Qi; Liu, Hongwei; Jia, Jianfeng; Chen, Chao; Zhao, Jian

    2013-04-17

    The intrinsic catalytic activity of palladium (Pd) is significantly enhanced in gold (Au)-Pd alloy nanoparticles (NPs) under visible light irradiation at ambient temperatures. The alloy NPs strongly absorb light and efficiently enhance the conversion of several reactions, including Suzuki-Miyaura cross coupling, oxidative addition of benzylamine, selective oxidation of aromatic alcohols to corresponding aldehydes and ketones, and phenol oxidation. The Au/Pd molar ratio of the alloy NPs has an important impact on performance of the catalysts since it determines both the electronic heterogeneity and the distribution of Pd sites at the NP surface, with these two factors playing key roles in the catalytic activity. Irradiating with light produces an even more profound enhancement in the catalytic performance of the NPs. For example, the best conversion rate achieved thermally at 30 °C for Suzuki-Miyaura cross coupling was 37% at a Au/Pd ratio of 1:1.86, while under light illumination the yield increased to 96% under the same conditions. The catalytic activity of the alloy NPs depends on the intensity and wavelength of incident light. Light absorption due to the Localized Surface Plasmon Resonance of gold nanocrystals plays an important role in enhancing catalyst performance. We believe that the conduction electrons of the NPs gain the light absorbed energy producing energetic electrons at the surface Pd sites, which enhances the sites' intrinsic catalytic ability. These findings provide useful guidelines for designing efficient catalysts composed of alloys of a plasmonic metal and a catalytically active transition metal for various organic syntheses driven by sunlight. PMID:23566035

  2. Effective function annotation through catalytic residue conservation.

    PubMed

    George, Richard A; Spriggs, Ruth V; Bartlett, Gail J; Gutteridge, Alex; MacArthur, Malcolm W; Porter, Craig T; Al-Lazikani, Bissan; Thornton, Janet M; Swindells, Mark B

    2005-08-30

    Because of the extreme impact of genome sequencing projects, protein sequences without accompanying experimental data now dominate public databases. Homology searches, by providing an opportunity to transfer functional information between related proteins, have become the de facto way to address this. Although a single, well annotated, close relationship will often facilitate sufficient annotation, this situation is not always the case, particularly if mutations are present in important functional residues. When only distant relationships are available, the transfer of function information is more tenuous, and the likelihood of encountering several well annotated proteins with different functions is increased. The consequence for a researcher is a range of candidate functions with little way of knowing which, if any, are correct. Here, we address the problem directly by introducing a computational approach to accurately identify and segregate related proteins into those with a functional similarity and those where function differs. This approach should find a wide range of applications, including the interpretation of genomics/proteomics data and the prioritization of targets for high-throughput structure determination. The method is generic, but here we concentrate on enzymes and apply high-quality catalytic site data. In addition to providing a series of comprehensive benchmarks to show the overall performance of our approach, we illustrate its utility with specific examples that include the correct identification of haptoglobin as a nonenzymatic relative of trypsin, discrimination of acid-d-amino acid ligases from a much larger ligase pool, and the successful annotation of BioH, a structural genomics target.

  3. The Catalytic Mechanism of Carbonic Anhydrase

    PubMed Central

    Lindskog, Sven; Coleman, Joseph E.

    1973-01-01

    It is shown that an “inverse” relationship between the pH dependencies of the rates of hydration of CO2 and dehydration of HCO3- by carbonic anhydrase (EC 4.2.1.1) is a direct consequence of the thermodynamic equilibrium between CO2 and HCO3- and independent of any assumptions about the catalytic mechanism. It is further shown that proposed mechanisms for carbonic anhydrase involving HCO3- as the substrate in the dehydration reaction and a proton transfer reaction, EH+ ⇌ E + H+, as an obligatory step during catalysis obey the rule of microscopic reversibility. This includes mechanisms in which the proton dissociation is from a zinc-coordinated water molecule. Such mechanisms can be in accord with the observed rapid turnover rates of the enzyme, since rapid proton exchange can occur with the buffer components, EH+ + B ⇌ E + BH+. Mechanisms in which H2CO3 is the substrate in dehydration avoid the proton-transfer step, but require that H2CO3 combines with enzyme more rapidly than in a diffusion-controlled reaction. Physico-chemical evidence for and against a zinc-hydroxide mechanism is discussed. PMID:4200327

  4. Catalytic extraction processing of contaminated scrap metal

    SciTech Connect

    Griffin, T.P.; Johnston, J.E.; Payea, B.M.

    1995-10-01

    The U.S. Department of Energy issued a Planned Research and Development Announcement (PRDA) in 1993, with the objective of identifying unique technologies which could be applied to the most hazardous waste streams at DOE sites. The combination of radioactive contamination with additional contamination by hazardous constituents such as those identified by the Resource Conservation and Recovery Act (RCRA) pose an especially challenging problem. Traditional remediation technologies are increasingly becoming less acceptable to stakeholders and regulators because of the risks they pose to public health and safety. Desirable recycling technologies were described by the DOE as: (1) easily installed, operated, and maintained; (2) exhibiting superior environmental performance; (3) protective of worker and public health and safety; (4) readily acceptable to a wide spectrum of evaluators; and (5) economically feasible. Molten Metal Technology, Inc. (MMT) was awarded a contract as a result of the PRDA initiative to demonstrate the applicability of Catalytic Extraction Processing (CEP), MMT`s proprietary elemental recycling technology, to DOE`s inventory of low level mixed waste. This includes DOE`s inventory of radioactively- and RCRA-contaminated scrap metal and other waste forms expected to be generated by the decontamination and decommissioning (D&D) of DOE sites.

  5. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Nagarkar, Amit A.; Kilbinger, Andreas F. M.

    2015-09-01

    In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst.

  6. Microchannel Reactor System for Catalytic Hydrogenation

    SciTech Connect

    Adeniyi Lawal; Woo Lee; Ron Besser; Donald Kientzler; Luke Achenie

    2010-12-22

    We successfully demonstrated a novel process intensification concept enabled by the development of microchannel reactors, for energy efficient catalytic hydrogenation reactions at moderate temperature, and pressure, and low solvent levels. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for hydrogenation of onitroanisole and a proprietary BMS molecule. In the second phase of the program, as a prelude to full-scale commercialization, we designed and developed a fully-automated skid-mounted multichannel microreactor pilot plant system for multiphase reactions. The system is capable of processing 1 – 10 kg/h of liquid substrate, and an industrially relevant immiscible liquid-liquid was successfully demonstrated on the system. Our microreactor-based pilot plant is one-of-akind. We anticipate that this process intensification concept, if successfully demonstrated, will provide a paradigm-changing basis for replacing existing energy inefficient, cost ineffective, environmentally detrimental slurry semi-batch reactor-based manufacturing practiced in the pharmaceutical and fine chemicals industries.

  7. Catalytic glycerol steam reforming for hydrogen production

    NASA Astrophysics Data System (ADS)

    Dan, Monica; Mihet, Maria; Lazar, Mihaela D.

    2015-12-01

    Hydrogen production from glycerol by steam reforming combine two major advantages: (i) using glycerol as raw material add value to this by product of bio-diesel production which is obtained in large quantities around the world and have a very limited utilization now, and (ii) by implication of water molecules in the reaction the efficiency of hydrogen generation is increased as each mol of glycerol produces 7 mol of H2. In this work we present the results obtained in the process of steam reforming of glycerol on Ni/Al2O3. The catalyst was prepared by wet impregnation method and characterized through different methods: N2 adsorption-desorption, XRD, TPR. The catalytic study was performed in a stainless steel tubular reactor at atmospheric pressure by varying the reaction conditions: steam/carbon ratio (1-9), gas flow (35 ml/min -133 ml/min), temperature (450-650°C). The gaseous fraction of the reaction products contain: H2, CH4, CO, CO2. The optimum reaction conditions as resulted from this study are: temperature 550°C, Gly:H2O ratio 9:1 and Ar flow 133 ml/min. In these conditions the glycerol conversion to gaseous products was 43% and the hydrogen yield was 30%.

  8. Catalytic glycerol steam reforming for hydrogen production

    SciTech Connect

    Dan, Monica Mihet, Maria Lazar, Mihaela D.

    2015-12-23

    Hydrogen production from glycerol by steam reforming combine two major advantages: (i) using glycerol as raw material add value to this by product of bio-diesel production which is obtained in large quantities around the world and have a very limited utilization now, and (ii) by implication of water molecules in the reaction the efficiency of hydrogen generation is increased as each mol of glycerol produces 7 mol of H{sub 2}. In this work we present the results obtained in the process of steam reforming of glycerol on Ni/Al{sub 2}O{sub 3}. The catalyst was prepared by wet impregnation method and characterized through different methods: N{sub 2} adsorption-desorption, XRD, TPR. The catalytic study was performed in a stainless steel tubular reactor at atmospheric pressure by varying the reaction conditions: steam/carbon ratio (1-9), gas flow (35 ml/min -133 ml/min), temperature (450-650°C). The gaseous fraction of the reaction products contain: H{sub 2}, CH{sub 4}, CO, CO{sub 2}. The optimum reaction conditions as resulted from this study are: temperature 550°C, Gly:H{sub 2}O ratio 9:1 and Ar flow 133 ml/min. In these conditions the glycerol conversion to gaseous products was 43% and the hydrogen yield was 30%.

  9. Catalytic pyrolysis using UZM-39 aluminosilicate zeolite

    SciTech Connect

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-10-07

    A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and shown to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub.1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  10. Catalytic pyrolysis using UZM-39 aluminosilicate zeolite

    SciTech Connect

    Nicholas, Christpher P; Boldingh, Edwin P

    2013-12-17

    A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and show to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hyrdocarbons into hydrocarbons removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  11. Durability of ceramic catalytic converters for motorcycles

    SciTech Connect

    Reddy, K.P.; Scott, P.L.; Hwang, H.S.; Mooney, J.J.

    1995-12-31

    Motorcycle exhaust emission standards throughout the world are becoming more stringent. Emission control systems utilizing the catalytic converter are already in production in Taiwan for 2-stroke engine motorcycles. Catalysts designed for 2-stroke engines encounter a more severe exhaust environment than do those designed for 4-stroke engines. The two aspects of increased severity are the higher temperatures and higher stresses due to engine vibrations. Precious metal catalysts have been designed to operate in the thermal environment of 2-stroke engines and such catalysts have been successfully applied to both metal and ceramic substrates. However, until now, only the metal substrate catalysts have been utilized in motorcycle application. Ceramic based catalysts have not been considered because the mounting material that holds the catalyst substrate in place did not have enough durability to withstand the thermal/vibrational forces encountered in 2-stroke engine exhaust. Ceramic substrates have many advantages such as superior high temperature strength, which is especially important for the 2-stroke engine application, flexibility in cell shape and density, and lower cost. To realize these benefits, efforts were made in this study to develop better mounting systems. The results of this effort indicate that the durability requirements of 2-stroke engine can be met with the ceramic catalyst substrates if the improved mounting designs reported in the present study are employed.

  12. Catalytic combustion of volatile organic compounds.

    PubMed

    Everaert, K; Baeyens, J

    2004-06-18

    Despite the success of adsorption and thermal incineration of (C)VOC emissions, there is still a need for research on techniques which are both economically more favorable and actually destroy the pollutants rather than merely remove them for recycling elsewhere in the biosphere. The catalytic destruction of (C)VOC to CO2, H2O and HCl/Cl2 appears very promising in this context and is the subject of the present paper. The experiments mainly investigate the catalytic combustion of eight target compounds, all of which are commonly encountered in (C)VOC emissions and/or act as precursors for the formation of PCDD/F. Available literature on the different catalysts active in the oxidation of (C)VOC is reviewed and the transition metal oxide complex V2O5-WO3/TiO2 appears most suitable for the current application. Different reactor geometries (e.g. fixed pellet beds, honeycombs, etc.) are also described. In this research a novel catalyst type is introduced, consisting of a V2O5-WO3/TiO2 coated metal fiber fleece. The conversion of (C)VOC by thermo-catalytic reactions is governed by both reaction kinetics and reaction equilibrium. Full conversion of all investigated VOC to CO2, Cl2, HCl and H2O is thermodynamically feasible within the range of experimental conditions used in this work (260-340 degrees C, feed concentrations 30-60 ppm). A first-order rate equation is proposed for the (C)VOC oxidation reactions. The apparent rate constant is a combination of reaction kinetics and mass transfer effects. The oxidation efficiencies were measured with various (C)VOC in the temperature range of 260-340 degrees C. Literature data for oxidation reactions in fixed beds and honeycomb reactors are included in the assessment. Mass transfer resistances are calculated and are generally negligible for fleece reactors and fixed pellet beds, but can be of importance for honeycomb monoliths. The experimental investigations demonstrate: (i) that the conversion of the hydrocarbons is

  13. Catalytic Preparation of Pyrrolidones from Renewable Resources

    SciTech Connect

    Frye, John G.; Zacher, Alan H.; Werpy, Todd A.; Wang, Yong

    2005-12-01

    Use of renewable resources for production of valuable chemical commodities is becoming a topic of great national interest and importance. This objective fits well with the USDOE’s objective of promoting the industrial bio-refinery concept in which a wide array of valuable chemical, fuel, food, nutraceuticals and animal feed products all result from the integrated processing of grains, oil seeds and other bio-mass materials. The bio-refinery thus serves to enhance the overall utility and profitability of the agriculture industry as well as helping to reduce the dependence on petroleum. Pyrrolidones fit well with the bio-refinery concept since they may be produced in a scheme beginning with the fermentation of a portion of the bio-refinery’s sugar product into succinate. Pyrrolidones are a class of industrially important chemicals with a variety of uses including as polymer intermediates, cleaners, and “green solvents” which can replace hazardous chlorinated compounds. Battelle has developed an efficient process for the thermo – catalytic conversion of succinate into pyrrolidones, especially n-methylpyrrolidone. The process uses both novel Rh based catalysts and novel aqueous process conditions and results in high selectivities and yields of pyrrolidone compounds. The process also includes novel methodology for enhancing yields by recycling and converting non-useful side products of the catalysis into additional pyrrolidone. The process has been demonstrated in both batch and continuous reactors. Additionally, stability of the unique Rh-based catalyst has been demonstrated.

  14. Catalytic oxidation of very fuel rich mixtures

    NASA Technical Reports Server (NTRS)

    Brabbs, T. A.

    1983-01-01

    The objective of this research is to demonstrate the feasibility of using a catalytic reactor as a tool to study soot formation from the fuel rich side of the soot limit (null set = 3 - 6). The experimental approach to be taken in the first phase of the research is to document that a hydrocarbon fuel can be burnt at very rich equivalence ratios without forming soot. A simple mono-component fuel, iso-octane, will be used as the test fuel. To insure that combustion is uniform across the catalyst bed, measurements will be made of the fuel-air equivalence ratio profile across the inlet and the temperature and product distribution across the outlet. Phase Two will be to use this environment as a testing ground for determining the effect the structure of a hydrocarbon fuel has on its tendency to form soot. Various amounts of organic compounds such as benzene will be added to the iso-octane and the reaction products studied. Other compounds to be tested will xylene, toluene, and naphthalene.

  15. Catalytic Reactor For Oxidizing Mercury Vapor

    DOEpatents

    Helfritch, Dennis J.

    1998-07-28

    A catalytic reactor (10) for oxidizing elemental mercury contained in flue gas is provided. The catalyst reactor (10) comprises within a flue gas conduit a perforated corona discharge plate (30a, b) having a plurality of through openings (33) and a plurality of projecting corona discharge electrodes (31); a perforated electrode plate (40a, b, c) having a plurality of through openings (43) axially aligned with the through openings (33) of the perforated corona discharge plate (30a, b) displaced from and opposing the tips of the corona discharge electrodes (31); and a catalyst member (60a, b, c, d) overlaying that face of the perforated electrode plate (40a, b, c) opposing the tips of the corona discharge electrodes (31). A uniformly distributed corona discharge plasma (1000) is intermittently generated between the plurality of corona discharge electrode tips (31) and the catalyst member (60a, b, c, d) when a stream of flue gas is passed through the conduit. During those periods when corona discharge (1000) is not being generated, the catalyst molecules of the catalyst member (60a, b, c, d) adsorb mercury vapor contained in the passing flue gas. During those periods when corona discharge (1000) is being generated, ions and active radicals contained in the generated corona discharge plasma (1000) desorb the mercury from the catalyst molecules of the catalyst member (60a, b, c, d), oxidizing the mercury in virtually simultaneous manner. The desorption process regenerates and activates the catalyst member molecules.

  16. Catalytic partial oxidation of pyrolysis oils

    NASA Astrophysics Data System (ADS)

    Rennard, David Carl

    2009-12-01

    This thesis explores the catalytic partial oxidation (CPO) of pyrolysis oils to syngas and chemicals. First, an exploration of model compounds and their chemistries under CPO conditions is considered. Then CPO experiments of raw pyrolysis oils are detailed. Finally, plans for future development in this field are discussed. In Chapter 2, organic acids such as propionic acid and lactic acid are oxidized to syngas over Pt catalysts. Equilibrium production of syngas can be achieved over Rh-Ce catalysts; alternatively mechanistic evidence is derived using Pt catalysts in a fuel rich mixture. These experiments show that organic acids, present in pyrolysis oils up to 25%, can undergo CPO to syngas or for the production of chemicals. As the fossil fuels industry also provides organic chemicals such as monomers for plastics, the possibility of deriving such species from pyrolysis oils allows for a greater application of the CPO of biomass. However, chemical production is highly dependent on the originating molecular species. As bio oil comprises up to 400 chemicals, it is essential to understand how difficult it would be to develop a pure product stream. Chapter 3 continues the experimentation from Chapter 2, exploring the CPO of another organic functionality: the ester group. These experiments demonstrate that equilibrium syngas production is possible for esters as well as acids in autothermal operation with contact times as low as tau = 10 ms over Rh-based catalysts. Conversion for these experiments and those with organic acids is >98%, demonstrating the high reactivity of oxygenated compounds on noble metal catalysts. Under CPO conditions, esters decompose in a predictable manner: over Pt and with high fuel to oxygen, non-equilibrium products show a similarity to those from related acids. A mechanism is proposed in which ethyl esters thermally decompose to ethylene and an acid, which decarbonylates homogeneously, driven by heat produced at the catalyst surface. Chapter 4

  17. Catalytic, stereospecific syn-dichlorination of alkenes

    NASA Astrophysics Data System (ADS)

    Cresswell, Alexander J.; Eey, Stanley T.-C.; Denmark, Scott E.

    2015-02-01

    As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Although the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. Here, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (selenium). With diphenyl diselenide (PhSeSePh) (5 mol%) as the pre-catalyst, benzyltriethylammonium chloride (BnEt3NCl) as the chloride source and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids.

  18. Catalytic, Stereospecific Syn-Dichlorination of Alkenes

    PubMed Central

    Cresswell, Alexander J.; Eey, Stanley T.-C.; Denmark, Scott E.

    2015-01-01

    As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Whilst the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. In this Article, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (i.e., selenium). Thus, with diphenyl diselenide (PhSeSePh) (5 mol %) as the pre-catalyst, benzyltriethylammonium chloride (BnEt3NCl) as the chloride source, and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids. PMID:25615668

  19. Development of high temperature catalytic membrane reactors

    SciTech Connect

    Not Available

    1992-02-01

    Significant progress was made in 1991 on the development of ceramic membranes as catalytic reactors. Efforts were focused on the design, construction and startup of a reactor system capable of duplicating relevant commercial operating conditions. With this system, yield enhancement was demonstrated for the dehydrogenation of ethylbenzene to styrene in a membrane reactor compared to the standard packed bed configuration. This enhancement came with no loss in styrene selectivity. During operation, coke deposition on the membrane was observed, but this deposition was mitigated by the presence of steam in the reaction mixture and a steady state permeability was achieved for run times in excess of 200 hours. Work began on optimizing the membrane reactor by exploring several parameters including the effect of N{sub 2} diluent in the reaction feed and the effect of a N{sub 2} purge on the permeate side of the membrane. This report details the experimental progress made in 1991. Interactions with the University of Wisconsin on this project are also summarized. Finally, current status of the project and next steps are outlined.

  20. Catalytic determination of vanadium in water

    USGS Publications Warehouse

    Fishman, M. J.; Skougstad, M.W.

    1964-01-01

    A rapid, accurate, and sensitive spectrophotometric method for the quantitative determination of trace amounts of vanadium in water is based on the catalytic effect of vanadium on the rate of oxidation of gallic acid by persulfate in acid solution. Under given conditions of concentrations of reactants, temperature, and reaction time, the extent of oxidation of gallic acid is proportional to the concentration of vanadium present. Vanadium is determined by measuring the absorbance of the sample at 415 m?? and comparison with standard solutions treated in an identical manner. Concentrations in the range of from 0.1 to 8.0 ??g. per liter may be determined with a standard deviation of 0.2 or less. By reducing the reaction time, the method may be extended to cover the range from 1 to 100 ??g. with a standard deviation of 0.8 or less. Several substances interfere, including chloride above 100 p.p.m., and bromide and iodide in much lower concentrations. Interference from the halides is eliminated or minimized by the addition of mercuric nitrate solution. Most other substances do not interfere at the concentration levels at which they commonly occur in natural waters.

  1. Atomic ordering periodicity and catalytic properties of nanoparticles

    NASA Astrophysics Data System (ADS)

    Petkov, Valeri

    2008-03-01

    Often nanosized particles of crystals are catalytically very active while the corresponding crystals are not. A typical example is gold. The enhanced catalytic performance of nanosized particles, however, does not come merely from their greatly enhanced surface-to-volume ratio. We would like to draw attention to the often overlooked fact that nanosized particles of crystals do not necessarily possess the periodic 3D structure of their bulk counterparts, and this too may impact their catalytic properties substantially. In particular, nanoparticles that do not have a periodic 3D structure may not come in a well-defined, faceted shape, i.e. may not be terminated by well-defined (usually high energy) atomic planes, as crystalline objects of the same size would be. Hence, nanoparticles may be catalytically more (or less) active than ``nanosized'' crystals. Results from recent structure studies (synchrotron XRD and computer simulations) on 1 -- 5 nm Ru, Au and Pt particles will be presented as evidence.

  2. Determination of Catalytic Coefficient for a First-Order Reaction

    ERIC Educational Resources Information Center

    Fraga, E. R.; And Others

    1975-01-01

    Describes an undergraduate physical chemistry experiment in which the acid catalyzed hydrolysis of sucrose is used to determine the catalytic coefficient of the hydronium ion, the catalyst in this reaction. (MLH)

  3. Catalytic combustion of heavy partially-vaporized fuels

    NASA Technical Reports Server (NTRS)

    Rosfjord, T. J.

    1980-01-01

    An experimental program to demonstrate efficient catalytic combustion of fuel-lean and fuel-rich mixtures of residual fuel and air, and to assess the influence of incomplete fuel vaporization on the performance of a catalytic reactor is being conducted. A 7.5-cm diameter catalytic reactor was designed and will be tested over a matrix of conditions representative of a gas turbine combustor inlet. For each of three test phases, two series of tests with a uniform but poorly vaporized (less than 50 percent) mixture of No. 6 fuel oil and air will be performed. In the first series, the non-vaporized fuel will be contained in a spray of droplets with a Sauter Mean Diameter (SMD) less than 30 microns. In the second series, the non-vaporized fuel will be characterized by a spray SMD approximately equal to 100 microns. The designs of the fuel injection system and the catalytic reactor are described in this paper.

  4. Development of Vapor-Phase Catalytic Ammonia Removal System

    NASA Technical Reports Server (NTRS)

    Flynn, Michael; Fisher, John; Kiss, Mark; Borchers, Bruce; Tleimat, Badawi; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale; Genovese, Joseph

    2007-01-01

    A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars.

  5. HOMOGENEOUS CATALYTIC OXIDATION OF HYDROCARBONS IN ALTERNATIVE SOLVENTS

    EPA Science Inventory

    Homogeneous Catalytic Oxidations of Hydrocarbons in Alternative Solvent Systems

    Michael A. Gonzalez* and Thomas M. Becker, Sustainable Technology Division, Office of Research and Development; United States Environmental Protection Agency, 26 West Martin Luther King Drive, ...

  6. Catalytic hydroxylation of benzoic acid by hydrogen peroxide

    SciTech Connect

    Pulippurasseril, C.R.; Filippova, T.Yu.; Dedov, A.G.

    1992-12-31

    An effective catalytic system based on Fe(III) and surfactants is proposed for the hydroxylation of benozic acid by hydrogen peroxide in an aqueous medium at a temperature of 30-80{degrees}C. 8 refs., 1 tab.

  7. Catalytic Asymmetric 1,4-Addition Reactions of Simple Alkylnitriles.

    PubMed

    Yamashita, Yasuhiro; Sato, Io; Suzuki, Hirotsugu; Kobayashi, Shū

    2015-10-01

    The development of catalytic asymmetric carbon-carbon bond-forming reactions of alkylnitriles that do not have an activating group at the α-position, under proton-transfer conditions, is a challenging research topic. Here, we report catalytic asymmetric direct-type 1,4-addition reactions of alkylnitriles with α,β-unsaturated amides by using a catalytic amount of potassium hexamethyldisilazide (KHMDS) with a chiral macro crown ether. The desired reactions proceeded in high yields with good diastereo- and enantioselectivities. To our knowledge, this is the first example of catalytic asymmetric direct-type 1,4-addition reaction of alkylnitriles without any activating group at the α-position.

  8. Development of a catalytic infrared cooking gas burner

    SciTech Connect

    Tonon, T.

    1987-09-22

    The catalytic oxidation of natural gas was investigated for application to an infrared stove-top burner. Project goals were to demonstrate stable catalytic combustion of natural gas in a burner, suitable for use in a stove top, that would have a thermal cooking efficiency of 70%, produce less than 10 ppm NOx and 50 ppm CO concentrations in the flue gas, and have a turndown ratio of five. Calculations were performed to estimate the length of the catalytic coating and burner dimensions; the fluid dynamics of flow through the burner was analyzed in order to size the venturi, and a test rig with two prototypes was constructed. The second prototype exhibited stable catalytic combustion, achieved a peak thermal efficiency of 59%, and satisfied the project goals for NOx and CO emissions.

  9. The role of surface generated radicals in catalytic combustion

    NASA Technical Reports Server (NTRS)

    Santavicca, D. A.; Stein, Y.; Royce, B. S. H.

    1985-01-01

    Experiments were conducted to better understand the role of catalytic surface reactions in determining the ignition characteristics of practical catalytic combustors. Hydrocarbon concentrations, carbon monoxide and carbon dioxide concentrations, hydroxyl radical concentrations, and gas temperature were measured at the exit of a platinum coated, stacked plate, catalytic combustor during the ignition of lean propane-air mixtures. The substrate temperature profile was also measured during the ignition transient. Ignition was initiated by suddenly turning on the fuel and the time to reach steady state was of the order of 10 minutes. The gas phase reaction, showed no pronounced effect due to the catalytic surface reactions, except the absence of a hydroxyl radical overshoot. It is found that the transient ignition measurements are valuable in understanding the steady state performance characteristics.

  10. Superior CO catalytic oxidation on novel Pt/clay nanocomposites.

    PubMed

    Varade, Dharmesh; Abe, Hideki; Yamauchi, Yusuke; Haraguchi, Kazutoshi

    2013-11-27

    Nanostructured novel Pt/Clay nanocomposites consisting of well-defined Pt nanoparticles prepared by clay-mediated in situ reduction displays very high thermal stability, large BET surface area and superior catalytic activity for CO oxidation as compared to a model reference Pt/SiO2 catalysts. CO oxidation has attracted renewed attention because of its technological importance in the area of pollution control. The Pt/Clay system consisting of Pt nanoparticles strongly immobilized between the atomic layers of clay inhibits nanoparticle sintering and loss of catalytic activity even after prolonged heating at high temperatures. At elevated temperatures (300 °C), the Pt/Clay system demonstrates significant enhancement of catalytic activity, with almost 100% CO conversion in less than 5 min. Emphasis is given to the role played by the clay supporting material which is chemically and thermally stable under the catalytic conditions of exhaust purification.

  11. Enzyme catalytic membrane based on a hybrid mesoporous membrane.

    PubMed

    Fu, Wensheng; Yamaguchi, Akira; Kaneda, Hideaki; Teramae, Norio

    2008-02-21

    Immobilization of glucose oxidase (GOD) within a hybrid mesoporous membrane with 12 nm pore diameter was successfully achieved, resulting in catalytically high efficiency during flow of a glucose solution across the membrane. PMID:18253526

  12. Facet-dependent catalytic activity of Cu2O nanocrystals in the one-pot synthesis of 1,2,3-triazoles by multicomponent click reactions.

    PubMed

    Chanda, Kaushik; Rej, Sourav; Huang, Michael H

    2013-11-18

    We report the highly facet-dependent catalytic activity of Cu2O nanocubes, octahedra, and rhombic dodecahedra for the multicomponent direct synthesis of 1,2,3-triazoles from the reaction of alkynes, organic halides, and NaN3. The catalytic activities of clean surfactant-removed Cu2O nanocrystals with the same total surface area were compared. Rhombic dodecahedral Cu2O nanocrystals bounded by {110} facets were much more catalytically active than Cu2O octahedra exposing {111} facets, whereas Cu2O nanocubes displayed the slowest catalytic activity. The superior catalytic activity of Cu2O rhombic dodecahedra is attributed to the fully exposed surface Cu atoms on the {110} facet. A large series of 1,4-disubstituted 1,2,3-triazoles have been synthesized in excellent yields with high regioselectivity under green conditions by using these rhombic dodecahedral Cu2O catalysts, including the synthesis of rufinamide, an antiepileptic drug, demonstrating the potential of these nanocrystals as promising heterogeneous catalysts for other important coupling reactions. PMID:24127396

  13. Catalytic Upgrading of Sugars to Hydrocarbons Technology Pathway

    SciTech Connect

    Biddy, M.; Jones, S.

    2013-03-01

    This technology pathway case investigates the catalytic conversion of solubilized carbohydrate streams to hydrocarbon biofuels, utilizing data from recent efforts within the National Advanced Biofuels Consortium (NABC) in collaboration with Virent, Inc. Technical barriers and key research needs that should be pursued for the catalytic conversion of sugars pathway to be competitive with petroleum-derived gasoline-, diesel-, and jet-range hydrocarbon blendstocks have been identified.

  14. Water recovery by catalytic treatment of urine vapor

    NASA Technical Reports Server (NTRS)

    Budininkas, P.; Quattrone, P. D.; Leban, M. I.

    1980-01-01

    The objective of this investigation was to demonstrate the feasibility of water recovery on a man-rated scale by the catalytic processing of untreated urine vapor. For this purpose, two catalytic systems, one capable of processing an air stream containing low urine vapor concentrations and another to process streams with high urine vapor concentrations, were designed, constructed, and tested to establish the quality of the recovered water.

  15. EXAFS studies on gold nanoparticles over novel catalytic materials

    NASA Astrophysics Data System (ADS)

    Akolekar, Deepak B.; Bhargava, Suresh K.; Foran, Garry

    2006-11-01

    Novel nanogold catalytic systems made up of gold nanoparticles (˜2-6 nm) supported on niobium, ytterbium, lanthanum and cerium oxide materials were synthesized. XAS is uniquely suited for studying catalytic systems with low metal and high metal dispersion. Au L 3 edge X-ray absorption spectroscopic measurements were carried out over a series of supported gold nanoparticles. The interesting results obtained from EXAFS and XANES confirms the typical characteristics and structure of gold nanoparticles in these materials.

  16. Kinetics and mechanism of olefin catalytic hydroalumination by organoaluminum compounds

    NASA Astrophysics Data System (ADS)

    Koledina, K. F.; Gubaidullin, I. M.

    2016-05-01

    The complex reaction mechanism of α-olefin catalytic hydroalumination by alkylalanes is investigated via mathematical modeling that involves plotting the kinetic models for the individual reactions that make up a complex system and a separate study of their principles. Kinetic parameters of olefin catalytic hydroalumination are estimated. Activation energies of the possible steps of the schemes of complex reaction mechanisms are compared and possible reaction pathways are determined.

  17. Northwestern University Facility for Clean Catalytic Process Research

    SciTech Connect

    Marks, Tobin Jay

    2013-05-08

    Northwestern University with DOE support created a Facility for Clean Catalytic Process Research. This facility is designed to further strengthen our already strong catalysis research capabilities and thus to address these National challenges. Thus, state-of-the art instrumentation and experimentation facility was commissioned to add far greater breadth, depth, and throughput to our ability to invent, test, and understand catalysts and catalytic processes, hence to improve them via knowledge-based design and evaluation approaches.

  18. Non-catalytic surfaces for metallic heat shields

    NASA Technical Reports Server (NTRS)

    Swann, R. T.; Wood, G. M.; Brown, R. D.; Upchurch, B. T.; Allen, G. J.

    1984-01-01

    The magnitude of the atom recombination coefficients needed for metal heat shield surfaces on Shuttle-type vehicles is analyzed and discussed. Prior work which identifies surfaces having low catalytic activity is reviewed. Arc tunnel tests to evaluate catalytic activity are described and the difficulties of such tests are discussed. Results are presented which show major differences between atom recombination and atom exchange from molecules. Results of surface analysis show that bulk and surface composition of a coating are different.

  19. [Study on catalytic oxidation of benzene by microwave heating].

    PubMed

    Zhang, Yu-cai; Bo, Long-li; Wang, Xiao-hui; Liu, Hai-nan; Zhang, Hao

    2012-08-01

    The performance in catalytic oxidation of benzene was investigated in two different heating modes, microwave heating and conventional electric furnace heating. The effects of copper (Cu)-manganese (Mn) mass ratio, doping dose of cerium (Ce) and calcination temperature on the catalytic activity of Cu-Mn-Ce/molecular sieve catalyst were also checked in catalytic oxidation of benzene with microwave heating, and the catalysts were subsequently characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the catalyst had better catalytic activity for the oxidation of benzene under microwave heating than electric furnace heating, and high oxidation efficiency for benzene was reached due to the "local hot spots" and dipole polarization effect of microwave and stable bed reaction temperature. Under the conditions of Cu, Mn and Ce mass ratio 1:1:0.33 and calcination temperature 500 degrees C, the catalyst had the optimal catalytic activity for benzene oxidation, and its light-off temperature and complete combustion temperature were 165 degrees C and 230 degrees C, respectively. It was indicated by characteristics of XRD and SEM that the presence of copper and manganese oxides and Cu1.5Mn1.5O4 with spinel crystal improved the catalytic activity of the catalyst, and the doping of Ce promoted the dispersion and regularization of active components. High calcination temperature led to the sintering of the catalyst surface and agglomeration of active components, which decreased the catalytic activity of the catalyst in the catalytic oxidation PMID:23213902

  20. Response reactions: equilibrium coupling.

    PubMed

    Hoffmann, Eufrozina A; Nagypal, Istvan

    2006-06-01

    It is pointed out and illustrated in the present paper that if a homogeneous multiple equilibrium system containing k components and q species is composed of the reactants actually taken and their reactions contain only k + 1 species, then we have a unique representation with (q - k) stoichiometrically independent reactions (SIRs). We define these as coupling reactions. All the other possible combinations with k + 1 species are the coupled reactions that are in equilibrium when the (q - k) SIRs are in equilibrium. The response of the equilibrium state for perturbation is determined by the coupling and coupled equilibria. Depending on the circumstances and the actual thermodynamic data, the effect of coupled equilibria may overtake the effect of the coupling ones, leading to phenomena that are in apparent contradiction with Le Chatelier's principle. PMID:16722770

  1. Three tooth kinematic coupling

    SciTech Connect

    Hale, L.C.

    2000-05-23

    A three tooth kinematic coupling is disclosed based on having three theoretical line contacts formed by mating teeth rather than six theoretical point contacts. The geometry requires one coupling half to have curved teeth and the other coupling half to have flat teeth. Each coupling half has a relieved center portion which does not effect the kinematics, but in the limit as the face width approaches zero, three line contacts become six point contacts. As a result of having line contact, a three tooth coupling has greater load capacity and stiffness. The kinematic coupling has application for use in precision fixturing for tools or workpieces, and as a registration device for a work or tool changer or for optics in various products.

  2. Three tooth kinematic coupling

    SciTech Connect

    Hale, Layton C.

    2000-01-01

    A three tooth kinematic coupling based on having three theoretical line contacts formed by mating teeth rather than six theoretical point contacts. The geometry requires one coupling half to have curved teeth and the other coupling half to have flat teeth. Each coupling half has a relieved center portion which does not effect the kinematics, but in the limit as the face width approaches zero, three line contacts become six point contacts. As a result of having line contact, a three tooth coupling has greater load capacity and stiffness. The kinematic coupling has application for use in precision fixturing for tools or workpieces, and as a registration device for a work or tool changer or for optics in various products.

  3. 40 CFR Table 22 to Subpart Uuu of... - Inorganic HAP Emission Limits for Catalytic Reforming Units

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Pt. 63, Subpt. UUU, Table 22 Table 22 to Subpart UUU of Part 63—Inorganic HAP Emission Limits for Catalytic Reforming Units... Catalytic Reforming Units 22 Table 22 to Subpart UUU of Part 63 Protection of Environment...

  4. 40 CFR Table 22 to Subpart Uuu of... - Inorganic HAP Emission Limits for Catalytic Reforming Units

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Pt. 63, Subpt. UUU, Table 22 Table 22 to Subpart UUU of Part 63—Inorganic HAP Emission Limits for Catalytic Reforming Units... Catalytic Reforming Units 22 Table 22 to Subpart UUU of Part 63 Protection of Environment...

  5. Catalytic and thermal depolymerization of low value post-consumer high density polyethylene plastic

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The feasibility of catalytic and non-catalytic pyrolytic conversion of low value post-consumer high density polyethylene (HDPE) plastic into crude oil and subsequent distillation was explored. Translation of optimized conditions for catalytic and non-catalytic pyrolysis from TGA to a bench-scale sys...

  6. The N-terminal end of the catalytic domain of SRC kinase Hck is a conformational switch implicated in long-range allosteric regulation.

    PubMed

    Banavali, Nilesh K; Roux, Benoît

    2005-11-01

    Signal transduction in cell growth and proliferation involves regulation of kinases through long-range allostery between remote protein regions. Molecular dynamics free energy calculations are used to clarify the coupling between the catalytic domain of Src kinase Hck and its N-terminal end connecting to the regulatory SH2 and SH3 modules. The N-terminal end is stable in the orientation required for the regulatory modules to remain properly bound only in the inactive catalytic domain. In the active catalytic domain, the N-terminal end prefers a different conformation consistent with dissociation of the regulatory modules. The free energy surface shows that the N-terminal end acts as a reversible two-state conformational switch coupling the catalytic domain to the regulatory modules. Structural analogy with insulin receptor kinase and c-Src suggests that such reversible conformational switching in a critical hinge region could be a common mechanism in long-range allosteric regulation of protein kinase activity.

  7. Catalytic activities of zeolite compounds for decomposing aqueous ozone.

    PubMed

    Kusuda, Ai; Kitayama, Mikito; Ohta, Yoshio

    2013-12-01

    The advanced oxidation process (AOP), chemical oxidation using aqueous ozone in the presence of appropriate catalysts to generate highly reactive oxygen species, offers an attractive option for removing poorly biodegradable pollutants. Using the commercial zeolite powders with various Si/Al ratios and crystal structures, their catalytic activities for decomposing aqueous ozone were evaluated by continuously flowing ozone to water containing the zeolite powders. The hydrophilic zeolites (low Si/Al ratio) with alkali cations in the crystal structures were found to possess high catalytic activity for decomposing aqueous ozone. The hydrophobic zeolite compounds (high Si/Al ratio) were found to absorb ozone very well, but to have no catalytic activity for decomposing aqueous ozone. Their catalytic activities were also evaluated by using the fixed bed column method. When alkali cations were removed by acid rinsing or substituted by alkali-earth cations, the catalytic activities was significantly deteriorated. These results suggest that the metal cations on the crystal surface of the hydrophilic zeolite would play a key role for catalytic activity for decomposing aqueous ozone.

  8. Rapid Catalytic Template Searching as an Enzyme Function Prediction Procedure

    PubMed Central

    Nilmeier, Jerome P.; Kirshner, Daniel A.; Wong, Sergio E.; Lightstone, Felice C.

    2013-01-01

    We present an enzyme protein function identification algorithm, Catalytic Site Identification (CatSId), based on identification of catalytic residues. The method is optimized for highly accurate template identification across a diverse template library and is also very efficient in regards to time and scalability of comparisons. The algorithm matches three-dimensional residue arrangements in a query protein to a library of manually annotated, catalytic residues – The Catalytic Site Atlas (CSA). Two main processes are involved. The first process is a rapid protein-to-template matching algorithm that scales quadratically with target protein size and linearly with template size. The second process incorporates a number of physical descriptors, including binding site predictions, in a logistic scoring procedure to re-score matches found in Process 1. This approach shows very good performance overall, with a Receiver-Operator-Characteristic Area Under Curve (AUC) of 0.971 for the training set evaluated. The procedure is able to process cofactors, ions, nonstandard residues, and point substitutions for residues and ions in a robust and integrated fashion. Sites with only two critical (catalytic) residues are challenging cases, resulting in AUCs of 0.9411 and 0.5413 for the training and test sets, respectively. The remaining sites show excellent performance with AUCs greater than 0.90 for both the training and test data on templates of size greater than two critical (catalytic) residues. The procedure has considerable promise for larger scale searches. PMID:23675414

  9. Molecular self-assembly strategy for generating catalytic hybrid polypeptides

    DOE PAGES

    Maeda, Yoshiaki; Fang, Justin; Ikezoe, Yasuhiro; Pike, Douglas H.; Nanda, Vikas; Matsui, Hiroshi

    2016-04-26

    Recently, catalytic peptides were introduced that mimicked protease activities and showed promising selectivity of products even in organic solvents where protease cannot perform well. However, their catalytic efficiency was extremely low compared to natural enzyme counterparts presumably due to the lack of stable tertiary fold. We hypothesized that assembling these peptides along with simple hydrophobic pockets, mimicking enzyme active sites, could enhance the catalytic activity. Here we fused the sequence of catalytic peptide CP4, capable of protease and esterase-like activities, into a short amyloidogenic peptide fragment of Aβ. When the fused CP4-Aβ construct assembled into antiparallel β- sheets and amyloidmore » fibrils, a 4.0-fold increase in the hydrolysis rate of p-nitrophenyl acetate (p-NPA) compared to neat CP4 peptide was observed. Furthermore, the enhanced catalytic activity of CP4-Aβ assembly could be explained both by pre-organization of a catalytically competent Ser-His-acid triad and hydrophobic stabilization of a bound substrate between the triad and p-NPA, indicating that a design strategy for self-assembled peptides is important to accomplish the desired functionality.« less

  10. Catalytic activities of zeolite compounds for decomposing aqueous ozone.

    PubMed

    Kusuda, Ai; Kitayama, Mikito; Ohta, Yoshio

    2013-12-01

    The advanced oxidation process (AOP), chemical oxidation using aqueous ozone in the presence of appropriate catalysts to generate highly reactive oxygen species, offers an attractive option for removing poorly biodegradable pollutants. Using the commercial zeolite powders with various Si/Al ratios and crystal structures, their catalytic activities for decomposing aqueous ozone were evaluated by continuously flowing ozone to water containing the zeolite powders. The hydrophilic zeolites (low Si/Al ratio) with alkali cations in the crystal structures were found to possess high catalytic activity for decomposing aqueous ozone. The hydrophobic zeolite compounds (high Si/Al ratio) were found to absorb ozone very well, but to have no catalytic activity for decomposing aqueous ozone. Their catalytic activities were also evaluated by using the fixed bed column method. When alkali cations were removed by acid rinsing or substituted by alkali-earth cations, the catalytic activities was significantly deteriorated. These results suggest that the metal cations on the crystal surface of the hydrophilic zeolite would play a key role for catalytic activity for decomposing aqueous ozone. PMID:25078817

  11. Gas phase oxidation downstream of a catalytic combustor

    NASA Technical Reports Server (NTRS)

    Tien, J. S.; Anderson, D. N.

    1979-01-01

    Effect of the length available for gas-phase reactions downstream of the catalytic reactor on the emission of CO and unburned hydrocarbons was investigated. A premixed, prevaporized propane/air feed to a 12/cm/diameter catalytic/reactor test section was used. The catalytic reactor was made of four 2.5 cm long monolithic catalyst elements. Four water cooled gas sampling probes were located at positions between 0 and 22 cm downstream of the catalytic reactor. Measurements of unburned hydrocarbon, CO, and CO2 were made. Tests were performed with an inlet air temperature of 800 K, a reference velocity of 10 m/s, pressures of 3 and 600,000 Pa, and fuel air equivalence ratios of 0.14 to 0.24. For very lean mixtures, hydrocarbon emissions were high and CO continued to be formed downstream of the catalytic reactor. At the highest equivalence ratios tested, hydrocarbon levels were much lower and CO was oxidized to CO2 in the gas phase downstream. To achieve acceptable emissions, a downstream region several times longer than the catalytic reactor could be required.

  12. Molecular Self-Assembly Strategy for Generating Catalytic Hybrid Polypeptides

    PubMed Central

    Ikezoe, Yasuhiro; Pike, Douglas H.; Nanda, Vikas; Matsui, Hiroshi

    2016-01-01

    Recently, catalytic peptides were introduced that mimicked protease activities and showed promising selectivity of products even in organic solvents where protease cannot perform well. However, their catalytic efficiency was extremely low compared to natural enzyme counterparts presumably due to the lack of stable tertiary fold. We hypothesized that assembling these peptides along with simple hydrophobic pockets, mimicking enzyme active sites, could enhance the catalytic activity. Here we fused the sequence of catalytic peptide CP4, capable of protease and esterase-like activities, into a short amyloidogenic peptide fragment of Aβ. When the fused CP4-Aβ construct assembled into antiparallel β-sheets and amyloid fibrils, a 4.0-fold increase in the hydrolysis rate of p-nitrophenyl acetate (p-NPA) compared to neat CP4 peptide was observed. The enhanced catalytic activity of CP4-Aβ assembly could be explained both by pre-organization of a catalytically competent Ser-His-acid triad and hydrophobic stabilization of a bound substrate between the triad and p-NPA, indicating that a design strategy for self-assembled peptides is important to accomplish the desired functionality. PMID:27116246

  13. Catalytic pyrolysis of waste rice husk over mesoporous materials

    PubMed Central

    2012-01-01

    Catalytic fast pyrolysis of waste rice husk was carried out using pyrolysis-gas chromatography/mass spectrometry [Py-GC/MS]. Meso-MFI zeolite [Meso-MFI] was used as the catalyst. In addition, a 0.5-wt.% platinum [Pt] was ion-exchanged into Meso-MFI to examine the effect of Pt addition. Using a catalytic upgrading method, the activities of the catalysts were evaluated in terms of product composition and deoxygenation. The structure and acid site characteristics of the catalysts were analyzed by Brunauer-Emmett-Teller surface area measurement and NH3 temperature-programmed desorption analysis. Catalytic upgrading reduced the amount of oxygenates in the product vapor due to the cracking reaction of the catalysts. Levoglucosan, a polymeric oxygenate species, was completely decomposed without being detected. While the amount of heavy phenols was reduced by catalytic upgrading, the amount of light phenols was increased because of the catalytic cracking of heavy phenols into light phenols and aromatics. The amount of aromatics increased remarkably as a result of catalytic upgrading, which is attributed to the strong Brönsted acid sites and the shape selectivity of the Meso-MFI catalyst. The addition of Pt made the Meso-MFI catalyst even more active in deoxygenation and in the production of aromatics. PMID:22221540

  14. Catalytic antibodies to HIV: Physiological role and potential clinical utility

    PubMed Central

    Planque, Stephanie; Nishiyama, Yasuhiro; Taguchi, Hiroaki; Salas, Maria; Hanson, Carl; Paul, Sudhir

    2008-01-01

    Immunoglobulins (Igs) in uninfected humans recognize residues 421–433 located in the B cell superantigenic site (SAg) of the HIV envelope protein gp120 and catalyze its hydrolysis by a serine protease-like mechanism. The catalytic activity is encoded by germline Ig variable (V) region genes, and is expressed at robust levels by IgMs and IgAs but poorly by IgGs. Mucosal IgAs are highly catalytic and neutralize HIV, suggesting that they constitute a first line of defense against HIV. Lupus patients produce the Igs at enhanced levels. Homology of the 421–433 region with an endogenous retroviral sequence and a bacterial protein may provide clues about the antigen driving anti-SAg synthesis in lupus patients and uninfected subjects. The potency and breadth of HIV neutralization revives hopes of clinical application of catalytic anti-421–433 Igs as immunotherapeutic and topical microbicide reagents. Adaptive improvement of anti-SAg catalytic Igs in HIV infected subjects is not customary. Further study of the properties of the naturally occurring anti-SAg catalytic Igs should provide valuable guidance in designing a prophylactic vaccine that amplifies protective catalytic immunity to HIV. PMID:18558365

  15. Rapid catalytic template searching as an enzyme function prediction procedure.

    PubMed

    Nilmeier, Jerome P; Kirshner, Daniel A; Wong, Sergio E; Lightstone, Felice C

    2013-01-01

    We present an enzyme protein function identification algorithm, Catalytic Site Identification (CatSId), based on identification of catalytic residues. The method is optimized for highly accurate template identification across a diverse template library and is also very efficient in regards to time and scalability of comparisons. The algorithm matches three-dimensional residue arrangements in a query protein to a library of manually annotated, catalytic residues--The Catalytic Site Atlas (CSA). Two main processes are involved. The first process is a rapid protein-to-template matching algorithm that scales quadratically with target protein size and linearly with template size. The second process incorporates a number of physical descriptors, including binding site predictions, in a logistic scoring procedure to re-score matches found in Process 1. This approach shows very good performance overall, with a Receiver-Operator-Characteristic Area Under Curve (AUC) of 0.971 for the training set evaluated. The procedure is able to process cofactors, ions, nonstandard residues, and point substitutions for residues and ions in a robust and integrated fashion. Sites with only two critical (catalytic) residues are challenging cases, resulting in AUCs of 0.9411 and 0.5413 for the training and test sets, respectively. The remaining sites show excellent performance with AUCs greater than 0.90 for both the training and test data on templates of size greater than two critical (catalytic) residues. The procedure has considerable promise for larger scale searches.

  16. Catalytic pyrolysis of car tire waste using expanded perlite.

    PubMed

    Kar, Y

    2011-08-01

    In this study, the non-catalytic and catalytic pyrolysis experiments were conducted on the sample of tire waste using expanded perlite as an additive material to determine especially the effect of temperature and catalyst-to-tire ratio on the products yields and the compositions and qualities of pyrolytic oils (NCPO and CPO). Non-catalytic studies, which were carried out under the certain conditions (a nitrogen flow of 100mL/min and a heating rate of 10°C/min), showed that the highest yield of pyrolytic oil (NCPO) was 60.02wt.% at 425°C. Then, the catalytic pyrolysis studies were carried out at catalyst-to-tire ratio range of 0.05-0.25 and the highest catalytic pyrolytic oil (CPO) yield was 65.11wt.% at the ratio of 0.10 with the yield increase of 8.48wt.% compared with the non-catalytic pyrolysis. Lastly, the pyrolytic oils were characterized with applying a various techniques such as elemental analyses and various chromatographic and spectroscopic techniques (GC-MS, (1)H NMR, FT-IR, etc.). The characterization results revealed that the pyrolytic oils which were complex mixtures of C(5)-C(15) organic compounds (predominantly aromatic compounds) and also the CPO compared to the NCPO was more similar to conventional fuels in view of the certain fuel properties.

  17. Form Follows Function: Structural and Catalytic Variation in the Class A Flavoprotein Monooxygenases

    PubMed Central

    Crozier-Reabe, Karen; Moran, Graham R.

    2012-01-01

    Flavoprotein monooxygenases (FPMOs) exhibit an array of mechanistic solutions to a common chemical objective; the monooxygenation of a target substrate. Each FPMO efficiently couples reduction of a flavin cofactor by NAD(P)H to oxygenation of the target substrate via a (hydro)peroxyflavin intermediate. This purpose of this review is to describe in detail the Class A flavoprotein hydroxylases (FPMO) in the context of the other FPMO classes (B–F). Both one and two component FPMOs are found in nature. Two-component enzymes require, in addition to the monooxygenase, the involvement of a reductase that first catalyzes the reduction of the flavin by NAD(P)H. The Class A and B FPMOs are single-component and manage to orchestrate the same net reaction within a single peptide. The Class A enzymes have, by some considerable margin, the most complete research record. These enzymes use choreographed movements of the flavin ring that facilitate access of the organic substrates to the active site, provide a means for interaction of NADPH with the flavin, offer a mechanism to sequester the dioxygen reduction chemistry from solvent and a means to release the product. The majority of the discrete catalytic events of the catalytic cycle can be observed directly in exquisite detail using spectrophotometric kinetic methods and many of the key mechanistic conclusions are further supported by structural data. This review attempts to compile each of the key observations made for both paradigm and newly discovered examples of Class A FPMOs into a complete catalytic description of one enzymatic turnover. PMID:23443084

  18. Catalytic Hydroxylation of Benzene to Phenol by Dioxygen with an NADH Analogue.

    PubMed

    Hirose, Kensaku; Ohkubo, Kei; Fukuzumi, Shunichi

    2016-08-26

    Hydroxylation of benzene by molecular oxygen (O2 ) occurs efficiently with 10-methyl-9,10-dihydroacridine (AcrH2 ) as an NADH analogue in the presence of a catalytic amount of Fe(ClO4 )3 or Fe(ClO4 )2 with excess trifluoroacetic acid in a solvent mixture of benzene and acetonitrile (1:1 v/v) to produce phenol, 10-methylacridinium ion and hydrogen peroxide (H2 O2 ) at 298 K. The catalytic oxidation of benzene by O2 with AcrH2 in the presence of a catalytic amount of Fe(ClO4 )3 is started by the formation of H2 O2 from AcrH2 , O2 , and H(+) . Hydroperoxyl radical (HO2 (.) ) is produced from H2 O2 with the redox pair of Fe(3+) /Fe(2+) by a Fenton type reaction. The rate-determining step in the initiation is the proton-coupled electron transfer from Fe(2+) to H2 O2 to produce HO(.) and H2 O. HO(.) abstracts hydrogen rapidly from H2 O2 to produce HO2 (.) and H2 O. The Fe(3+) produced was reduced back to Fe(2+) by H2 O2 . HO2 (.) reacts with benzene to produce the radical adduct, which abstracts hydrogen from AcrH2 to give the corresponding hydroperoxide, accompanied by generation of acridinyl radical (AcrH(.) ) to constitute the radical chain reaction. Hydroperoxyl radical (HO2 (.) ), which was detected by using the spin trap method with EPR analysis, acts as a chain carrier for the two radical chain pathways: one is the benzene hydroxylation with O2 and the second is oxidation of an NADH analogue with O2 to produce H2 O2 . PMID:27465104

  19. Dynamics of the active site architecture in plant-type ferredoxin-NADP(+) reductases catalytic complexes.

    PubMed

    Sánchez-Azqueta, Ana; Catalano-Dupuy, Daniela L; López-Rivero, Arleth; Tondo, María Laura; Orellano, Elena G; Ceccarelli, Eduardo A; Medina, Milagros

    2014-10-01

    Kinetic isotope effects in reactions involving hydride transfer and their temperature dependence are powerful tools to explore dynamics of enzyme catalytic sites. In plant-type ferredoxin-NADP(+) reductases the FAD cofactor exchanges a hydride with the NADP(H) coenzyme. Rates for these processes are considerably faster for the plastidic members (FNR) of the family than for those belonging to the bacterial class (FPR). Hydride transfer (HT) and deuteride transfer (DT) rates for the NADP(+) coenzyme reduction of four plant-type FNRs (two representatives of the plastidic type FNRs and the other two from the bacterial class), and their temperature dependences are here examined applying a full tunnelling model with coupled environmental fluctuations. Parameters for the two plastidic FNRs confirm a tunnelling reaction with active dynamics contributions, but isotope effects on Arrhenius factors indicate a larger contribution for donor-acceptor distance (DAD) dynamics in the Pisum sativum FNR reaction than in the Anabaena FNR reaction. On the other hand, parameters for bacterial FPRs are consistent with passive environmental reorganisation movements dominating the HT coordinate and no contribution of DAD sampling or gating fluctuations. This indicates that active sites of FPRs are more organised and rigid than those of FNRs. These differences must be due to adaptation of the active sites and catalytic mechanisms to fulfil their particular metabolic roles, establishing a compromise between protein flexibility and functional optimisation. Analysis of site-directed mutants in plastidic enzymes additionally indicates the requirement of a minimal optimal architecture in the catalytic complex to provide a favourable gating contribution. PMID:24953402

  20. Human P-glycoprotein exhibits reduced affinity for substrates during a catalytic transition state.

    PubMed

    Ramachandra, M; Ambudkar, S V; Chen, D; Hrycyna, C A; Dey, S; Gottesman, M M; Pastan, I

    1998-04-01

    Human P-glycoprotein (Pgp), a plasma membrane protein that confers multidrug resistance, functions as an ATP-dependent drug efflux pump. Pgp contains two ATP binding/utilization sites and exhibits ATPase activity that is stimulated in the presence of substrates and modulating agents. The mechanism of coupling of ATP hydrolysis to drug transport is not known. To understand the role of ATP hydrolysis in drug binding, it is necessary to develop methods for purifying and reconstituting Pgp that retains properties including stimulation of ATPase activity by known substrates to an extent similar to that in the native membrane. In this study, (His)6-tagged Pgp was expressed in Trichoplusia ni (High Five) cells using the recombinant baculovirus system and purified by metal affinity chromatography. Upon reconstitution into phospholipid vesicles, purified Pgp exhibited specific binding to analogues of substrates and ATP in affinity labeling experiments and displayed a high level of drug-stimulated ATPase activity (specific activity ranging from 4.5 to 6.5 micromol min-1 mg-1). The ATPase activity was inhibited by ADP in a competitive manner, and by vanadate and N-ethylmaleimide at low concentrations. Vanadate which is known to inhibit ATPase activity by trapping MgADP at the catalytic site inhibited photoaffinity labeling of Pgp with substrate analogues, [125I]iodoarylazidoprazosin and [3H]azidopine, only under ATP hydrolysis conditions. Because vanadate-trapped Pgp is known to resemble the ADP and phosphate-bound catalytic transition state, our findings indicate that ATP hydrolysis results in a conformation with reduced affinity for substrates. A catalytic transition conformation with reduced affinity would essentially result in substrate dissociation and supports a model for drug transport in which an ATP hydrolysis-induced conformational change leads to drug release toward the extracellular medium.

  1. SWI/SNF mutant cancers depend upon catalytic and non–catalytic activity of EZH2

    PubMed Central

    Kim, Kimberly H.; Kim, Woojin; Howard, Thomas P.; Vazquez, Francisca; Tsherniak, Aviad; Wu, Jennifer N.; Wang, Weishan; Haswell, Jeffrey R.; Walensky, Loren D.; Hahn, William C.; Orkin, Stuart H.; Roberts, Charles W. M.

    2016-01-01

    Human cancer genome sequencing has recently revealed that genes encoding subunits of SWI/SNF chromatin remodeling complexes are frequently mutated across a wide variety of cancers, and several subunits of the complex have been shown to have bona fide tumor suppressor activity1. However, whether mutations in SWI/SNF subunits result in shared dependencies is unknown. Here we show that EZH2, a catalytic subunit of the Polycomb repressive complex 2 (PRC2), is essential in all tested cancer cell lines and xenografts harboring mutations of the SWI/SNF subunits ARID1A, PBRM1, and SMARCA4, which are several of the most frequently mutated SWI/SNF subunits in human cancer but that co–occurrence of a Ras pathway mutation correlates with abrogation of this dependence. Surprisingly, we demonstrate that SWI/SNF mutant cancer cells are primarily dependent upon a non–catalytic role of EZH2 in stabilization of the PRC2 complex, and only partially dependent on EZH2 histone methyltransferase activity. These results not only reveal a shared dependency of cancers with genetic alterations in SWI/SNF subunits, but also suggest that EZH2 enzymatic inhibitors now in clinical development may not fully suppress the oncogenic activity of EZH2. PMID:26552009

  2. SWI/SNF-mutant cancers depend on catalytic and non-catalytic activity of EZH2.

    PubMed

    Kim, Kimberly H; Kim, Woojin; Howard, Thomas P; Vazquez, Francisca; Tsherniak, Aviad; Wu, Jennifer N; Wang, Weishan; Haswell, Jeffrey R; Walensky, Loren D; Hahn, William C; Orkin, Stuart H; Roberts, Charles W M

    2015-12-01

    Human cancer genome sequencing has recently revealed that genes that encode subunits of SWI/SNF chromatin remodeling complexes are frequently mutated across a wide variety of cancers, and several subunits of the complex have been shown to have bona fide tumor suppressor activity. However, whether mutations in SWI/SNF subunits result in shared dependencies is unknown. Here we show that EZH2, a catalytic subunit of the polycomb repressive complex 2 (PRC2), is essential in all tested cancer cell lines and xenografts harboring mutations of the SWI/SNF subunits ARID1A, PBRM1, and SMARCA4, which are several of the most frequently mutated SWI/SNF subunits in human cancer, but that co-occurrence of a Ras pathway mutation is correlated with abrogation of this dependence. Notably, we demonstrate that SWI/SNF-mutant cancer cells are primarily dependent on a non-catalytic role of EZH2 in the stabilization of the PRC2 complex, and that they are only partially dependent on EZH2 histone methyltransferase activity. These results not only reveal a shared dependency of cancers with genetic alterations in SWI/SNF subunits, but also suggest that EZH2 enzymatic inhibitors now in clinical development may not fully suppress the oncogenic activity of EZH2.

  3. Plasma-assisted catalytic storage reduction system

    DOEpatents

    Penetrante, Bernardino M.; Vogtlin, George E.; Merritt, Bernard T.; Brusasco, Raymond M.

    2002-01-01

    A two-stage method for NO.sub.x reduction in an oxygen-rich engine exhaust comprises a plasma oxidative stage and a storage reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons. The second stage employs a lean NO.sub.x trap to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage with a plasma, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber in which a non-thermal plasma converts NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons, such as propene. A flow of such hydrocarbons (C.sub.x H.sub.y) is input from usually a second pipe into at least a portion of the first chamber. The NO.sub.2 from the plasma treatment proceeds to a storage reduction catalyst (lean NO.sub.x trap) that converts NO.sub.2 to N.sub.2, CO.sub.2, and H.sub.2 O, and includes a nitrate-forming catalytic site. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the lean-NO.sub.x trap catalyst. The method allows for enhanced NO.sub.x reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.

  4. Plasma-assisted catalytic storage reduction system

    DOEpatents

    Penetrante, Bernardino M.; Vogtlin, George E.; Merritt, Bernard T.; Brusasco, Raymond M.

    2000-01-01

    A two-stage method for NO.sub.x reduction in an oxygen-rich engine exhaust comprises a plasma oxidative stage and a storage reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons. The second stage employs a lean NO.sub.x trap to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage with a plasma, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber in which a non-thermal plasma converts NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons, such as propene. A flow of such hydrocarbons (C.sub.x H.sub.y) is input from usually a second pipe into at least a portion of the first chamber. The NO.sub.2 from the plasma treatment proceeds to a storage reduction catalyst (lean NO.sub.x trap) that converts NO.sub.2 to N.sub.2, CO.sub.2, and H.sub.2 O, and includes a nitrate-forming catalytic site. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the lean-NO.sub.x trap catalyst. The method allows for enhanced NO.sub.x reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.

  5. Catalytic Preparation of Pyrrolidones from Renewable Resources

    SciTech Connect

    Frye, John G.; Zacher, Alan H.; Werpy, Todd A.; Wang, Yong

    2005-06-01

    Abstract Use of renewable resources for production of valuable chemical commodities is becoming a topic of great national interest and importance. This objective fits well with the U.S. DOE’s objective of promoting the industrial bio-refinery concept in which a wide array of valuable chemical, fuel, food, nutraceuticals, and animal feed products all result from the integrated processing of grains, oil seeds, and other bio-mass materials. The bio-refinery thus serves to enhance the overall utility and profitability of the agriculture industry as well as helping to reduce the USA’s dependence on petroleum. Pyrrolidones fit well into the bio-refinery concept since they may be produced in a scheme beginning with the fermentation of a portion of the bio-refinery’s sugar product into succinate. Pyrrolidones are a class of industrially important chemicals with a variety of uses including polymer intermediates, cleaners, and “green solvents” which can replace hazardous chlorinated compounds. Battelle has developed an efficient process for the thermo-catalytic conversion of succinate into pyrrolidones, especially n-methyl-2-pyrrolidone. The process uses both novel Rh based catalysts and novel aqueous process conditions and results in high selectivities and yields of pyrrolidone compounds. The process also includes novel methodology for enhancing yields by recycling and converting non-useful side products of the catalysis into additional pyrrolidone. The process has been demonstrated in both batch and continuous reactors. Additionally, stability of the unique Rh-based catalyst has been demonstrated.

  6. Aconitase: its source of catalytic protons.

    PubMed

    Kuo, D J; Rose, I A

    1987-12-01

    An ordinary isotope partition experiment was performed to determine the rate of dissociation of the proton from the donor site for the hydration of cis-aconitate. Aconitase in [3H]water was efficiently diluted into well-mixed solutions of cis-aconitate. Citrate and isocitrate that were formed within 2 s were more heavily labeled than could be explained by consideration of an isotope effect in the processing of one proton per enzyme equivalent. Control experiments indicate that mixing was much more rapid than catalytic turnover, ruling out incompletely diluted [3H]water as a significant isotope source. Therefore, it appears that significantly more than one enzyme-bound tritium atom (protons) must have been used in the course of the multiple turnover of the enzyme after the dilution was complete. Isotope incorporation reached values in excess of four proton equivalents as a limit with simple Michaelis dependence on cis-aconitate. From the half-saturation concentration value for trapping, 0.15 mM, the t 1/2 for exchange of each of these protons with solvent appears to be approximately 0.1 s at 0 degrees C. The large number of protons trapped seems to suggest the existence of a structurally stabilized pool of protons, or water, that communicates between the active site base and the medium in the hydration of cis-aconitate. The proton abstracted in the dehydration of [3H]citrate is transferred directly to undissociated cis-aconitate to form isocitrate without dilution, or cis-aconitate having dissociated, the tritium passes to the medium, presumably through the pool of bound protons indicated above. All of the citrate-derived protons can be found in isocitrate if cis-aconitate is added in sufficient concentration.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2827757

  7. Separation of electron-transfer and coupled chemical reaction components of biocatalytic processes using Fourier transform ac voltammetry.

    PubMed

    Fleming, Barry D; Zhang, Jie; Bond, Alan M; Bell, Stephen G; Wong, Luet-Lok

    2005-06-01

    The underlying electron-transfer and coupled chemical processes associated with biologically important catalytic reactions can be resolved using a combination of Fourier transform ac voltammetry with an analysis of the separated dc and ac components. This outcome can be achieved because the response associated with generation of the catalytic current is essentially confined to the steady-state dc component, whereas the electron-transfer step is dominant in the fundamental and higher harmonics. For the mediated oxidation of glucose with glucose oxidase, it was found that the underlying reversible redox chemistry of the mediator, ferrocenemonocarboxylic acid, as detected in the third and higher harmonics, was totally unaffected by introduction of the catalytic process. In contrast, for the catalytic reduction of molecular oxygen by cytochrome P450, slight changes in the P450 redox process were detected when the catalytic reaction was present. Simulations of a simple catalytic reaction scheme support the fidelity of this novel FT ac voltammetric approach for examining mechanistic nuances of catalytic forms of electrochemical reaction schemes.

  8. Unraveling Surface Plasmon Decay in Core-Shell Nanostructures toward Broadband Light-Driven Catalytic Organic Synthesis.

    PubMed

    Huang, Hao; Zhang, Lei; Lv, Zhiheng; Long, Ran; Zhang, Chao; Lin, Yue; Wei, Kecheng; Wang, Chengming; Chen, Lu; Li, Zhi-Yuan; Zhang, Qun; Luo, Yi; Xiong, Yujie

    2016-06-01

    Harnessing surface plasmon of metal nanostructures to promote catalytic organic synthesis holds great promise in solar-to-chemical energy conversion. High conversion efficiency relies not only on broadening the absorption spectrum but on coupling the harvested energy into chemical reactions. Such coupling undergoes hot-electron transfer and photothermal conversion during the decay of surface plasmon; however, the two plasmonic effects are unfortunately entangled, making their individual roles still under debate. Here, we report that in a model system of bimetallic Au-Pd core-shell nanostructures the two effects can be disentangled through tailoring the shell thickness at atomic-level precision. As demonstrated by our ultrafast absorption spectroscopy characterizations, the achieved tunability of the two effects in a model reaction of Pd-catalyzed organic hydrogenation offers a knob for enhancing energy coupling. In addition, the two intrinsic plasmonic modes at 400-700 and 700-1000 nm in the bar-shaped nanostructures allow for utilizing photons to a large extent in full solar spectrum. This work establishes a paradigmatic guidance toward designing plasmonic-catalytic nanomaterials for enhanced solar-to-chemical energy conversion.

  9. Treatment of waste metalworking fluid by a hybrid ozone-biological process.

    PubMed

    Jagadevan, Sheeja; Graham, Nigel J; Thompson, Ian P

    2013-01-15

    In metal machining processes, the regulation of heat generation and lubrication at the contact point are achieved by application of a fluid referred to as metalworking fluid (MWF). MWFs inevitably become operationally exhausted with age and intensive use, which leads to compromised properties, thereby necessitating their safe disposal. Disposal of this waste through a biological route is an increasingly attractive option, since it is effective with relatively low energy demands. However, successful biological treatment is challenging since MWFs are chemically complex, and include biocides specifically to retard microbial deterioration whilst the fluids are operational. In this study remediation of the recalcitrant component of a semi-synthetic MWF by a novel hybrid ozone-bacteriological treatment, was investigated. The hybrid treatment proved to be effective and reduced the chemical oxygen demand by 72% (26.9% and 44.9% reduction after ozonation and biological oxidation respectively). Furthermore, a near-complete degradation of three non-biodegradable compounds (viz. benzotriazole, monoethanolamine, triethanolamine), commonly added as biocides and corrosion inhibitors in MWF formulations, under ozonation was observed. PMID:23274939

  10. [Treatment of petrochemical secondary effluent by ozone-biological aerated filter].

    PubMed

    Liu, Ming-Guo; Wu, Chang-Yong; Zhou, Yue-Xi; Gao, Zhen; Wang, Pei-Chao; Yang, Qi; Dong, De

    2014-02-01

    The advanced treatment of petrochemical secondary wastewater by ozone- aerated biological filter was carried out in this study. The effect of pH on ozonation and the removal of COD and UV254 by the ozone-aerated biological filter combined process were investigated. In addition, the variation of relative molecular mass distribution of organics and the characteristics of three-dimensional fluorescence spectra of the wastewater were also investigated. The results showed that the suitable operating conditions of the ozonation unit were: ozone dosage 10 mg x L(-1), contact time 4 min and slightly alkaline pH. Ozonation can transfer macromolecular organics into small molecular organics, resulting in a 15% increase in the percentage of the organics with small relative molecular mass (less than 1 000). The biodegradability of the petrochemical secondary effluent was significantly improved by ozonation, making it more suitable for the treatment by aerated biological filter. The removal efficiency of COD and UV254 were 40.8% and 45.8% when the hydraulic retention time was 3 hours and the gas to water ratio was 3:1 for BAF. The average COD of the petrochemical wastewater was 86.5 mg x L(-1) while the average COD of the effluent of the combined process was 49.4 mg x L(-1) when it was operated under optimal conditions.

  11. Synthesis, spectral characterization and catalytic activity of Co(II) complexes of drugs: Crystal structure of Co(II)-trimethoprim complex

    NASA Astrophysics Data System (ADS)

    Madhupriya, Selvaraj; Elango, Kuppanagounder P.

    2014-01-01

    New Co(II) complexes with drugs such as trimethoprim (TMP), cimetidine (CTD), niacinamide (NAM) and ofloxacin (OFL) as ligands were synthesized. The complexes were characterized by analytical analysis, various spectral techniques such as FT-IR, UV-Vis, magnetic measurements and molar conductivity. The magnetic susceptibility results coupled with the electronic spectra suggested a tetrahedral geometry for the complexes. The coordination mode of trimethoprim ligand and geometry of the complex were confirmed by single crystal X-ray studies. In this complex the metal ion possesses a tetrahedral geometry with two nitrogen atom from two TMP ligands and two chloride ions coordinated to it. The catalytic activity of the complexes in aryl-aryl coupling reaction was screened and the results indicated that among the four complexes [Co(OFL)Cl(H2O)] exhibited excellent catalytic activity.

  12. Cyclopentadienyl nickel(ii) N,C-chelating benzothiazolyl NHC complexes: synthesis, characterization and application in catalytic C-C bond formation reactions.

    PubMed

    Teo, Wei Jie; Wang, Zhe; Xue, Fei; Andy Hor, T S; Zhao, Jin

    2016-04-25

    Cyclopentadienyl (Cp) Ni(ii) complexes [CpNiL][PF6] containing hybrid N,C chelating benzothiazolyl NHC ligands (L1 = 1-(2-benzothiazolyl)-3-methylimidazol-2-ylidene, ; L2 = 1-(2-benzothiazolyl)-3-allylimidazol-2-ylidene, ; L3 = 1-(2-benzothiazolyl)-3-benzylimidazol-2-ylidene, ) have been synthesized and fully characterized. The catalytic activity of in some C-C bond formation reactions has been examined. They are efficient catalysts for the homo-coupling of benzyl bromide in the presence of MeMgCl at r.t. with good functional group tolerance. Complex is active in the catalytic oxidative homo-coupling of Grignard reagents with 1,2-dichloroethane as an oxidant at r.t. PMID:27011227

  13. Control of combustion-generated nitrogen oxides by selective non-catalytic reduction.

    PubMed

    Javed, M Tayyeb; Irfan, Naseem; Gibbs, B M

    2007-05-01

    Controlling nitrogen oxides (NO(x)) emissions is becoming a daunting technical challenge as increasingly strict emission limits are being imposed. The stringent regulations have prompted the innovation and characterization of NO(x) control technologies suitable for various applications. This paper presents a review on NO(x) removal techniques with particular reference to selective non-catalytic reduction (SNCR) technology. This includes initially how SNCR emerged as a technology along with a comparison with other relevant technologies. A review of various features related to selective non-catalytic gas phase injection of ammonia and ammonium salts (as reducing agent) is presented. The use of urea solution as a reducing agent and its performance in laboratory and pilot scale tests as well as large-scale applications is also discussed. Use of cyanuric acid as a potential reducing agent is also presented. The underlying reaction mechanisms have been reviewed for ammonia, urea and cyanuric acid for the explanation of various observations. Computational fluid dynamics (CFD) modeling as applied to SNCR is also presented. Subsequently the use of SNCR coupled with other in-combustion and post-combustion NO(x) control techniques is elaborated. Additionally, a two-stage NO(x) removal strategy to control un-reacted ammonia slip and to improve overall efficiency is discussed. At the end a summary is given which highlights various areas needing further research.

  14. Synthesis of Au-SiO2 Composite Nanospheres and Their Catalytic Activity.

    PubMed

    Dexuan, Wang; Guian, Li; Qingyan, Han; Ziqiang, Wang; Liping, Pan; Zhonayue, Zhang; Hairong, Zhenq

    2016-04-01

    We report a simple and environmentally friendly approach to the synthesis of Au-SiC2 composite nanospheres. Our method presents a route for the decoration of preformed amine functionalized SiO2 nanospheres by in situ formation of Au nanoparticles at three different concentrations of Au precursor (HAuCl4). Herein, the silane coupling agent (KH-550) is used as an intermediary to connect the Au nanoparticles to the surfaces of the SiO2 nanospheres, which helps avoid the aggregation of Au nanoparticles. The crystal structure, chemical elements, morphology and catalytic properties of the Au-SiO2 composite nanospheres were analyzed by transmission electron microscopy (TEM), X-Ray powder diffraction (XRD), UV-vis-spectrophotometer (UV-vis) and X-ray photoelectron spectroscopy (XPS). The analytical results demonstrate that the Au nanoparticles (4-9 nm) were homogeneously distributed on the surface of the SiO2 nanospheres, which had a good FCC crystal structure. Moreover, the Au-SiO2 composite nanospheres exhibited good catalytic properties, measured by their ability to reduce organic dyes. The Au-SiO2 composite nanospheres are promising candidates for applications in catalysis and wastewater treatment. PMID:27451717

  15. Structural Characterization of the Catalytic Sites of Mononuclear Nonheme Fe Hydroxylases Using ²H-ESEEM.

    PubMed

    McCracken, John

    2015-01-01

    Aromatic amino acid hydroxylases are members of a larger group of enzymes that use a mononuclear nonheme Fe center to catalyze a variety of thermodynamically challenging reactions in which O2 is used in the oxidative transformation of substrates. The hydroxylase enzymes are catalytically active in the ferrous oxidation state and are high-spin. To render the catalytic site EPR-active, we have used nitric oxide (NO) as a surrogate for substrate O2 to form an S=3/2 paramagnetic center. While the continuous-wave (cw)-EPR spectra of NO-enzyme adducts are rather generic, they provide electron spin echo envelope modulation (ESEEM) data that are rich with structural information derived from ligand hyperfine couplings. This chapter will focus on (2)H-ESEEM spectroscopy, an approach that we have taken for assigning these spectra and harvesting the unique information on Fe(II) coordination chemistry that they provide. While these spectroscopic measurements are routine, an emphasis will be placed on the analysis of cw-EPR and (2)H-ESEEM data using an unconstrained nonlinear optimization approach. These analysis methods are based on simple custom "scripts" that run in the MATLAB environment and that use EasySpin, a public-domain EPR simulation package, as their calculation engine. The examples provided here use a strategy that can be adapted for the treatment of most EPR measurements.

  16. Preparation and photo-catalytic activities of FeOOH/ZnO/MMT composite

    NASA Astrophysics Data System (ADS)

    Zhou, Yao; Liu, Fusheng; Yu, Shitao

    2015-11-01

    Montmorillonite (MMT) was used as the carrier for synthesis of FeOOH and FeOOH/ZnO nano-material. FeOOH and FeOOH/ZnO were synthesized by the aqueous solutions of Fe(NO3)3-HNO3 and Zn(NO3)2-NaOH/Fe(NO3)3-HNO3 with the carrier of montmorillonite respectively. Transmission electron-microscopy (TEM) and X-ray diffraction (XRD) were used to study the morphology form and structure of the nano-materials. TEM was also used to demonstrate that FeOOH/ZnO can be formed with the appropriate interface. According to UV-vis absorption spectra, FeOOH/ZnO has a better response to visible light than FeOOH and ZnO, which indicates there is some coupling effect between FeOOH and ZnO. Pentachlorophenol (PCP) was used as a representative organic pollutant to evaluate the photo-catalytic efficiency of the FeOOH/ZnO and FeOOH catalysts in visible light (λ > 400 nm). The photo-catalytic efficiency of FeOOH/ZnO/MMT is better than FeOOH/MMT. According to FTIR, changes of pH and TOC, the degradation mechanism was also discussed. PCP was degraded to aromatic ketone and chloro-hydrocarbon compounds and then to H2O, CO2 and HCl.

  17. A multisyringe flow-based system for kinetic-catalytic determination of cobalt(II).

    PubMed

    Chaparro, Laura; Ferrer, Laura; Leal, Luz; Cerdà, Víctor

    2015-02-01

    A kinetic-catalytic method for cobalt determination based on the catalytic effect of cobalt(II) on the oxidative coupling of 1,2-dihydroxyanthraquinone (alizarin) was automated exploiting multisyringe flow injection analysis (MSFIA). The proposed method was performed at pH 9.2, resulting in a discoloration process in the presence of hydrogen peroxide. The fixed-time approach was employed for analytical signal measurement. The spectrophotometric detection was used exploiting a liquid waveguide capillary cell (LWCC), of 1m optical length at 465 nm. The optimization was carried out by a multivariate approach, reaching critical values of 124 µmol L(-1) and 0.22 mol L(-1) for alizarin and hydrogen peroxide, respectively, and 67°C of reagent temperature. A sample volume of 150 µL was used allowing a sampling rate of 30h(-1). Under optimal conditions, calibration curve was linear in the range of 1-200 µg L(-1) Co, achieving a DL of 0.3 µg L(-1) Co. The repeatability, expressed as relative standard deviation (RSD) was lower than 1%. The proposed analytical procedure was applied to the determination of cobalt in cobalt gluconate and different forms of vitamin B12, cyanocobalamin and hydroxicobalamin with successful results showing recoveries around 95%.

  18. Structural Characterization of the Catalytic Sites of Mononuclear Nonheme Fe Hydroxylases Using ²H-ESEEM.

    PubMed

    McCracken, John

    2015-01-01

    Aromatic amino acid hydroxylases are members of a larger group of enzymes that use a mononuclear nonheme Fe center to catalyze a variety of thermodynamically challenging reactions in which O2 is used in the oxidative transformation of substrates. The hydroxylase enzymes are catalytically active in the ferrous oxidation state and are high-spin. To render the catalytic site EPR-active, we have used nitric oxide (NO) as a surrogate for substrate O2 to form an S=3/2 paramagnetic center. While the continuous-wave (cw)-EPR spectra of NO-enzyme adducts are rather generic, they provide electron spin echo envelope modulation (ESEEM) data that are rich with structural information derived from ligand hyperfine couplings. This chapter will focus on (2)H-ESEEM spectroscopy, an approach that we have taken for assigning these spectra and harvesting the unique information on Fe(II) coordination chemistry that they provide. While these spectroscopic measurements are routine, an emphasis will be placed on the analysis of cw-EPR and (2)H-ESEEM data using an unconstrained nonlinear optimization approach. These analysis methods are based on simple custom "scripts" that run in the MATLAB environment and that use EasySpin, a public-domain EPR simulation package, as their calculation engine. The examples provided here use a strategy that can be adapted for the treatment of most EPR measurements. PMID:26478489

  19. A hybrid process combining homogeneous catalytic ozonation and membrane distillation for wastewater treatment.

    PubMed

    Zhang, Yong; Zhao, Peng; Li, Jie; Hou, Deyin; Wang, Jun; Liu, Huijuan

    2016-10-01

    A novel catalytic ozonation membrane reactor (COMR) coupling homogeneous catalytic ozonation and direct contact membrane distillation (DCMD) was developed for refractory saline organic pollutant treatment from wastewater. An ozonation process took place in the reactor to degrade organic pollutants, whilst the DCMD process was used to recover ionic catalysts and produce clean water. It was found that 98.6% total organic carbon (TOC) and almost 100% salt were removed and almost 100% metal ion catalyst was recovered. TOC in the permeate water was less than 16 mg/L after 5 h operation, which was considered satisfactory as the TOC in the potassium hydrogen phthalate (KHP) feed water was as high as 1000 mg/L. Meanwhile, the membrane distillation flux in the COMR process was 49.8% higher than that in DCMD process alone after 60 h operation. Further, scanning electron microscope images showed less amount and smaller size of contaminants on the membrane surface, which indicated the mitigation of membrane fouling. The tensile strength and FT-IR spectra tests did not reveal obvious changes for the polyvinylidene fluoride membrane after 60 h operation, which indicated the good durability. This novel COMR hybrid process exhibited promising application prospects for saline organic wastewater treatment. PMID:27372262

  20. [Nitric Oxide Removal with a Fe-TiO₂/PSF Hybrid Catalytic Membrane Bioreactor].

    PubMed

    Li, Bao-ren; Chen, Zhou-yang; Wang, Jian-bin; Zhang, Zai-li; Fan, Qing-juan; Wei, Zai-shan

    2016-03-15

    The Fe-doped titanium dioxide (Fe-TiO₂) was prepared by the sol-gel method and was loaded on polysulfone (PSF) hollow fiber membrane. A novel Fe-TiO₂/PSF hybrid catalytic membrane biofilm reactor (HCMBfR) was investigated for nitric oxide removal, to further improve the elimination capacity. HCMBfR exhibited a good stability in the 180-day operation period, the NO removal efficiency was up to 93.2% and the maximum elimination capacity reached 167.1 g · (m³ · h)⁻1. The additional use of the biofilm to wet Fe-TiO₂/PSF membrane catalysis reactor led to the enhancement of NO removal efficiency from 59. 5% to 66% . The NO removal efficiency in the intimate coupling of Fe-TiO₂/PSF hybrid catalytic membrane and biofilm reactor ( HCMBfR) increased from 1.4% to 13% as compared to that of the membrane biofilm reactor (MBfR) only. The optimal illumination intensity, gas residence time, pH and nC/nN were 670 lx, 9 a, 6.8-7.2 and 3.7, respectively. PMID:27337874