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Sample records for propane oxidative dehydrogenation

  1. Kinetic isotopic effects in oxidative dehydrogenation of propane on vanadium oxide catalysts

    SciTech Connect

    Chen, K.; Iglesia, E.; Bell, A.T.

    2000-05-15

    Kinetic isotopic effects (KIEs) for oxidative dehydrogenation of propane were measured on 10 wt% V{sub 2}O{sub 5}/ZrO{sub 2}. Normal KIEs were obtained using CH{sub 3}CH{sub 2}CH{sub 3} and CD{sub 3}CD{sub 2}CD{sub 3} as reactants for primary dehydrogenation (2.8) and combustion (1.9) of propane and for secondary combustion of propene (2.6), suggesting that in all cases C-H bond dissociation is a kinetically relevant step. CH{sub 3}CH{sub 2}CH{sub 3} and CH{sub 3}CD{sub 2}CH{sub 3} reactants led to normal KIEs for dehydrogenation (2.7) and combustion (1.8) of propane, but to a very small KIE (1.1) for propene combustion. These results show that the methylene C-H bond is activated in the rate-determining steps for propane dehydrogenation and combustion reactions. The rate-determining step in secondary propene combustion involves the allylic C-H bond. In each reaction, the weakest C-H bond in the reactant is cleaved in the initial C-H bond activation step. The measured propane oxidative dehydrogenation KIEs are in agreement with theoretical estimates using a sequence of elementary steps, reaction rate expression, and transition state theory. The much smaller KIE for propane oxidative dehydrogenation (2.8) than the maximum KIE (6) expected for propane thermal dehydrogenation indicates the participation of lattice oxygen. The different KIE values for propane primary dehydrogenation and combustion suggest that these two reactions involve different lattice oxygen sites.

  2. Highly efficient VOx/SBA-15 mesoporous catalysts for oxidative dehydrogenation of propane.

    PubMed

    Liu, Yong-Mie; Cao, Yong; Zhu, Ka-Ke; Yan, Shi-Run; Dai, Wei-Lin; He, He-Yong; Fan, Kang-Nian

    2002-12-01

    Highly dispersed vanadia species on SBA-15 mesoporous silica have been found to exhibit a highly efficient catalytic performance for the oxidative dehydrogenation (ODH) of propane to light olefins (propene + ethylene). PMID:12478769

  3. Site-dependent catalytic activity of graphene oxides towards oxidative dehydrogenation of propane.

    PubMed

    Tang, Shaobin; Cao, Zexing

    2012-12-28

    Graphene oxides (GOs) may offer extraordinary potential in the design of novel catalytic systems due to the presence of various oxygen functional groups and their unique electronic and structural properties. Using first-principles calculations, we explore the plausible mechanisms for the oxidative dehydrogenation (ODH) of propane to propene by GOs and the diffusion of the surface oxygen-containing groups under an external electric field. The present results show that GOs with modified oxygen-containing groups may afford high catalytic activity for the ODH of propane to propene. The presence of hydroxyl groups around the active sites provided by epoxides can remarkably enhance the C-H bond activation of propane and the activity enhancement exhibits strong site dependence. The sites of oxygen functional groups on the GO surface can be easily tuned by the diffusion of these groups under an external electric field, which increases the reactivity of GOs towards ODH of propane. The chemically modified GOs are thus quite promising in the design of metal-free catalysis. PMID:22801590

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

    SciTech Connect

    Argyle, Morris D.; Chen, Kaidong; Bell, Alexis T.; Iglesia, Enrique

    2001-09-11

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

  5. Carbon nanofibers modified with heteroatoms as metal-free catalysts for the oxidative dehydrogenation of propane.

    PubMed

    Marco, Yanila; Roldán, Laura; Muñoz, Edgar; García-Bordejé, Enrique

    2014-09-01

    Carbon nanofibres (CNFs) were modified with B and P by an ex situ approach. In addition, CNFs doped with N were prepared in situ using ethylenediamine as the N and C source. After calcination, the doped CNFs were used as catalysts for the oxidative dehydrogenation of propane. For B-CNFs, the effects of boron loading and calcination temperature on B speciation and catalytic conversion were studied. For the same reaction temperatures and conversions, B- and P-doped CNFs exhibited higher selectivities to propene than pristine CNFs. The N-CNFs were the most active but the least selective of the catalysts tested here. Our results also show that the type of P precursor affects the selectivity to propene and that CNFs modified using triphenylphosphine as the precursor provided the highest selectivity at isoconversion. PMID:25138580

  6. Catalytic propane dehydrogenation over In₂O₃–Ga₂O₃ mixed oxides

    SciTech Connect

    Tan, Shuai; Gil, Laura Briones; Subramanian, Nachal; Sholl, David S.; Nair, Sankar; Jones, Christopher W.; Moore, Jason S.; Liu, Yujun; Dixit, Ravindra S.; Pendergast, John G.

    2015-08-26

    We have investigated the catalytic performance of novel In₂O₃–Ga₂O₃ mixed oxides synthesized by the alcoholic-coprecipitation method for propane dehydrogenation (PDH). Reactivity measurements reveal that the activities of In₂O₃–Ga₂O₃ catalysts are 1–3-fold (on an active metal basis) and 12–28-fold (on a surface area basis) higher than an In₂O₃–Al₂O₃ catalyst in terms of C₃H₈ conversion. The structure, composition, and surface properties of the In₂O₃–Ga₂O₃ catalysts are thoroughly characterized. NH₃-TPD shows that the binary oxide system generates more acid sites than the corresponding single-component catalysts. Raman spectroscopy suggests that catalysts that produce coke of a more graphitic nature suppress cracking reactions, leading to higher C₃H₆ selectivity. Lower reaction temperature also leads to higher C₃H₆ selectivity by slowing down the rate of side reactions. XRD, XPS, and XANES measurements, strongly suggest that metallic indium and In₂O₃ clusters are formed on the catalyst surface during the reaction. The agglomeration of In₂O₃ domains and formation of a metallic indium phase are found to be irreversible under O₂ or H₂ treatment conditions used here, and may be responsible for loss of activity with increasing time on stream.

  7. Anomalous reactivity of supported V2O5 nanoparticles for propane oxidative dehydrogenation: influence of the vanadium oxide precursor.

    PubMed

    Carrero, Carlos A; Keturakis, Christopher J; Orrego, Andres; Schomäcker, Reinhard; Wachs, Israel E

    2013-09-21

    The oxidative dehydrogenation (ODH) of propane to propylene by supported vanadia catalysts has received much attention in recent years, but different reactivity trends have been reported for this catalytic reaction system. In the present investigation, the origin of these differing trends are investigated with synthesis of supported V/SiO2, V/TiO2, and V/Al2O3 catalysts prepared with three different vanadium oxide precursors (2-propanol/vanadyl triisopropoxide [VO(O-Pri)3] (VTI), oxalic acid/ammonium metavanadate [NH4VO3] (AMV), and toluene/vanadyl acetylacetonate [VO(C5H7O2)2] (VAA)) in order to elucidate the influence of the precursor on supported vanadia phase and propane ODH activity. In situ Raman spectroscopy revealed that the choice of vanadium precursor does not affect the dispersion of the supported vanadium oxide phase below 4 V nm(-2) (0.5 monolayer coverage), where only isolated and oligomeric surface VO4 species are present, and only the AMV precursor favors crystalline V2O5 nanoparticle (NP) formation below monolayer coverage (8 V nm(-2)). The propane ODH specific reactivity trend demonstrated that there is no significant difference in TOF for the isolated and oligomeric surface VO4 sites. Surprisingly, V2O5 NPs in the ∼1-2 nm range exhibit anomalously high propane ODH TOF values for the supported vanadia catalysts. This was found for all supported vanadium oxide catalysts examined. This comparative study with different V-precursors and synthesis methods and oxide supports finally resolves the debate in the catalysis literature about the dependence of TOF on the surface vanadium density that is related to the unusually high reactivity of small V2O5 NPs. PMID:23652298

  8. Stability and catalytic performance of vanadia supported on nanostructured titania catalyst in oxidative dehydrogenation of propane

    NASA Astrophysics Data System (ADS)

    Kootenaei, A. H. Shahbazi; Towfighi, J.; Khodadadi, A.; Mortazavi, Y.

    2014-04-01

    Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V2O5 catalyst in oxidative dehydrogenation of propane (ODP). The structures of pristine nanotubes as well as the prepared catalysts were investigated by XRD, Raman, FTIR, HRTEM, SEM, EDS, BET, and XPS techniques. The characterization of the as-synthesized nanotubes showed the synthesis of hydrogen titanate nanotube. The incipient wetness impregnation method was utilized to prepare VTNT-x (x = 5, 10, and 15 wt.% vanadia supported on nanotube) together with VTi5 (5 wt.% vanadia supported on Degussa P25). The anatase phase was developed in VTNT-x catalysts upon calcination along with specific surface area loss. Higher vanadia loading resulted in the lowering of support capacity in maintaining vanadia in dispersed state such that eventually crystalline vanadia appeared. The measured catalyst activity demonstrates that in spite of major support surface area loss in VTNT-5 catalyst, the propylene yield is superior in comparison with VTi5 catalyst. The catalyst activity can be correlated with maximum reduction temperature. Deactivation of VTi5 and VTNT-5 as well as VTNT-15 were studied for 3,000 min time-on-stream. It was found that the activity of VTNT-5 catalyst remain unchanged while a decline in catalytic activity observed in VTi5 and VTNT-15 catalysts. The development of rutile was considered as being a major element in the deactivation of the investigated catalysts which is influenced by the presence of vanadium and reaction atmosphere.

  9. Study on the structure, acidic properties of V-Zr nanocrystal catalysts in oxidative dehydrogenation of propane

    NASA Astrophysics Data System (ADS)

    Chen, Shu; Ma, Fei; Xu, Aixin; Wang, Lina; Chen, Fang; Lu, Weimin

    2014-01-01

    A series of V-doped zirconia nanocrystal (the molar ratio of V/Zr varying from 0.001 to 0.15) were prepared via hydrothermal method and performed in oxidative dehydrogenation of propane. It was found that vanadium was highly dispersed on the surface and in the bulk of ZrO2. The distribution of the vanadium species, the valence states and the aggregation state of V species on the surface, as well as the acid properties of the catalysts including kinds, number and strength were detected by the various characteristic methods. The correlation between the V content and the surroundings of the different V species has been studied. The function of acid properties, especially Brønsted acid in the catalytic performance has been discussed. Oxidative dehydrogenation reactions were carried out in a continuous flow fixed bed reactor and ZrV0.01 catalyst showed good conversion and selectivity with a yield of propylene of 21.3%.

  10. Oxidative dehydrogenation of ethane and propane over Ca-Co-P catalysts

    NASA Astrophysics Data System (ADS)

    Aaddane, A.; Kacimi, M.; Ziyad, M.

    2005-03-01

    Different compositions of calcium-cobalt phosphate Ca{3-x}Cox(PO{4})2 (0≤ x≤ 3) were synthesized by the precipitation method. The X-ray diffraction patterns showed that in the range 0 ≤x≤0.3 the solid displays a whitlockite-type structure which belongs to rhombohedral symmetry with the space group R3c (Z = 6). U.V-visible investigations showed that Co2+ ions occupy the M(5) sites of the phosphate. The same technique revealed that all cobalt cations exist under the +II oxidation state. Pure tricalcium phosphate β -Ca{3}(PO{4})2 was found inactive in the ODH reactions of ethane and propane. An increase of Co2+ concentration in the catalysts improved the performances.

  11. Insertion of porous chromia in {gamma}-zirconium phosphate and its catalytic performance in the oxidative dehydrogenation of propane

    SciTech Connect

    Jimenez-Lopez, A.; Rodriguez-Castellon, E.; Santamaria-Gonzalez, J.; Braos-Garcia, P.; Felici, E.; Marmottini, F.

    2000-04-04

    An expanded phase of acetate-hydroxide of Cr(III) intercalated into {gamma}-zirconium phosphate has been isolated by refluxing a solution formed by chromium(III) acetate-hydroxide and {gamma}-zirconium phosphate, previously dispersed in 1:1 water-acetone solution at 353 K. By calcination of this phase at 623 K under vacuum, an intercalated compound with a basal spacing of 1.73 nm and a surface area of 147 m{sup 2} g{sup {minus}1} was obtained. A temperature-programmed reduction study reveals that this solid contains a little amount of chromium in high oxidation state. However, when the precursor is heated at 673 K, a collapsed structure with a low surface area was obtained. The inserted porous chromia in {gamma}-zirconium phosphate calcined at 623 K is active in the oxidative dehydrogenation of propane at 623 K with 58% conversion and 10% of selectivity to propene. When this material is calcined at 823 K in air, it is also active in this reaction but only at high temperature, 823 K being necessary to attain catalytic properties similar to those observed for the catalyst prepared at low temperature.

  12. Synthesis of Pt–Pd Core–Shell Nanostructures by Atomic Layer Deposition: Application in Propane Oxidative Dehydrogenation to Propylene

    SciTech Connect

    Lei, Yu; Liu, Bin; Lu, Junling; Lobo-Lapidus, Rodrigo J.; Wu, Tianpin; Feng, Hao; Xia, Xiaoxing; Mane, Anil U.; Libera, Joseph A.; Greeley, Jeffrey P.; Miller, Jeffrey T.; Elam, Jeffrey W.

    2012-08-20

    Atomic layer deposition (ALD) was employed to synthesize supported Pt–Pd bimetallic particles in the 1 to 2 nm range. The metal loading and composition of the supported Pt–Pd nanoparticles were controlled by varying the deposition temperature and by applying ALD metal oxide coatings to modify the support surface chemistry. High-resolution scanning transmission electron microscopy images showed monodispersed Pt–Pd nanoparticles on ALD Al2O3- and TiO2-modified SiO2 gel. X-ray absorption spectroscopy revealed that the bimetallic nanoparticles have a stable Pt-core, Pd-shell nanostructure. Density functional theory calculations revealed that the most stable surface configuration for the Pt–Pd alloys in an H2 environment has a Pt-core, Pd-shell nanostructure. Finally, in comparison to their monometallic counterparts, the small Pt–Pd bimetallic core–shell nanoparticles exhibited higher activity in propane oxidative dehydrogenation as compared to their physical mixture.

  13. A practical grinding-assisted dry synthesis of nanocrystalline NiMoO{sub 4} polymorphs for oxidative dehydrogenation of propane

    SciTech Connect

    Chen Miao; Wu Jialing; Liu Yongmei; Cao Yong; Guo Li; He Heyong; Fan Kangnian

    2011-12-15

    A practical two-stage reactive grinding-assisted pathway waste-free and cost-effective for the synthesis of NiMoO{sub 4} has been successfully developed. It was demonstrated that proper design in synthetic strategy for grinding plays a crucial role in determining the ultimate polymorph of NiMoO{sub 4}. Specifically, direct grinding (DG) of MoO{sub 3} and NiO rendered {alpha}-NiMoO{sub 4} after annealing, whereas sequential grinding (SG) of the two independently pre-ground oxides followed by annealing generated {beta}-NiMoO{sub 4} solid solution. Characterizations in terms of Raman and X-ray diffraction suggest the creation of {beta}-NiMoO{sub 4} precursor in the latter alternative is the key aspect for the formation of {beta}-NiMoO{sub 4}. The DG-derived {alpha}-NiMoO{sub 4} tested by oxidative dehydrogenation of propane exhibited superior activity in contrast to its analog synthesized via conventional coprecipitation. It is suggested that the favorable chemical composition facilely obtained via grinding in contrast to that by coprecipitation was essential for achieving a more selective production of propylene. - Graphical Abstract: Grinding-assisted synthesis of NiMoO{sub 4} offers higher and more reproducible activities in contrast to coprecipitation for oxidative dehydrogenation of propane, and both {alpha}- and {beta}-NiMoO{sub 4} can be synthesized. Highlights: Black-Right-Pointing-Pointer NiMoO{sub 4} was prepared through grinding-assisted pathway. Black-Right-Pointing-Pointer Direct/sequential grinding rendered {alpha}-, {beta}-NiMoO{sub 4}, respectively. Black-Right-Pointing-Pointer Grinding-derived {alpha}-NiMoO{sub 4} showed high and reproducible activity for oxidative dehydrogenation of propane.

  14. Oxidative dehydrogenation of propane over vanadia-based catalysts supported on high-surface-area mesoporous MgAl2O4

    SciTech Connect

    Evans, Owen R.; Bell, Alexis T.; Tilley, T. Don

    2004-06-01

    The oxidative dehydrogenation of propane to propene was investigated over a series of novel vanadia-based catalysts supported on high-surface-area magnesium spinel. A mesoporous MgAl2O4 support was synthesized via a low-temperature sol gel process involving the heterobimetallic alkoxide precursor, Mg[Al(O iPr)4]2. A high-purity catalyst support was obtained after calcination at 1173 K under O2 atmosphere and active vanadia catalysts were prepared from the thermolysis of OV(O tBu)3 after grafting onto the spinel support. MgAl2O4-supported catalysts prepared in this manner have BET surface areas of 234 245 m2/g. All of the catalysts were characterized by X-ray powder diffraction, and Raman, solid-state NMR, and diffuse-reflectance UV vis spectroscopy. At all vanadium loadings the vanadia supported on MgAl2O4 exist as a combination of isolated monovanadate and tetrahedral polyvanadate species. As the vanadium surface density increases for these catalysts the ratio of polyvanadate species to isolated monovanadate species increases. In addition, as the vanadium surface density increases for these catalysts, the initial rate of propane ODH per V atom increases and reaches a maximum value at 6 VOx/nm2. Increasing the vanadium surface density past this point results in a decrease in the rate of propane ODH owing to the formation of multilayer species in which subsurface vanadium atoms are essentially rendered catalytically inactive. The initial propene selectivity increases with increasing vanadium surface density and reaches a plateau of {approx}95 percent for the V/MgAl catalysts. Rate coefficients for propane ODH (k1), propane combustion (k2), and propene combustion (k3) were calculated for these catalysts. The value of k1 increases with increasing VOx surface density, reaching a maximum at about 5.5 VOx/nm2. On the other hand, the ratio (k2/k1) for V/MgAl decreases with increasing VOx surface density. The ratio (k3/k1) for both sets of catalysts shows no dependence on

  15. A hybrid sol–gel synthesis of mesostructured SiC with tunable porosity and its application as a support for propane oxidative dehydrogenation.

    PubMed

    Xu, Jie; Liu, Yong-Mei; Xue, Bing; Li, Yong-Xin; Cao, Yong; Fan, Kang-Nian

    2011-06-01

    Porous silicon carbide (SiC) is of great potential as catalyst support in several industrially important reactions because of its unique thermophysical characteristics. Previously porous SiC was mostly obtained by a simple sol–gel or reactive replica technique which can only produce a material with low or medium surface area (< 50 m2 g(−1)). Here we report a new hybrid sol–gel approach to synthesize mesostructured SiC with high surface area (151–345 m2 g(−1)) and tunable porosity. The synthesis route involves a facile co-condensation of TEOS and alkyloxysilane with different alkyl-chain lengths followed by carbothermal reduction of the as-prepared alkyloxysilane precursors at 1350 °C. The resulting materials were investigated by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. A mechanism for the tailored synthesis of mesostructured SiC was tentatively proposed. To demonstrate the catalytic application of these materials, vanadia were loaded on the mesostructured SiC supports, and their catalytic performance in oxidative dehydrogenation of propane was evaluated. Vanadia supported on the mesostructured silicon carbide exhibits higher selectivity to propylene than those on conventional supports such as Al2O3 and SiO2 at the same propane conversion levels, mainly owing to its outstanding thermal conductivity which makes contributions to dissipate the heat generated from reaction thus alleviating the hot spots effect and over-oxidation of propylene. PMID:21739681

  16. ZrO2 -Based Alternatives to Conventional Propane Dehydrogenation Catalysts: Active Sites, Design, and Performance.

    PubMed

    Otroshchenko, Tatyana; Sokolov, Sergey; Stoyanova, Mariana; Kondratenko, Vita A; Rodemerck, Uwe; Linke, David; Kondratenko, Evgenii V

    2015-12-21

    Non-oxidative dehydrogenation of propane to propene is an established large-scale process that, however, faces challenges, particularly in catalyst development; these are the toxicity of chromium compounds, high cost of platinum, and catalyst durability. Herein, we describe the design of unconventional catalysts based on bulk materials with a certain defect structure, for example, ZrO2 promoted with other metal oxides. Comprehensive characterization supports the hypothesis that coordinatively unsaturated Zr cations are the active sites for propane dehydrogenation. Their concentration can be adjusted by varying the kind of ZrO2 promoter and/or supporting tiny amounts of hydrogenation-active metal. Accordingly designed Cu(0.05 wt %)/ZrO2 -La2 O3 showed industrially relevant activity and durability over ca. 240 h on stream in a series of 60 dehydrogenation and oxidative regeneration cycles between 550 and 625 °C. PMID:26566072

  17. Ordered mesoporous carbon catalyst for dehydrogenation of propane to propylene.

    PubMed

    Liu, Lei; Deng, Qing-Fang; Agula, Bao; Zhao, Xu; Ren, Tie-Zhen; Yuan, Zhong-Yong

    2011-08-01

    Metal-free ordered mesoporous carbons were demonstrated to be robust catalysts for direct dehydrogenation of propane to propylene, in the absence of any auxiliary steam, exhibiting high activity and selectivity, as well as long catalytic stability, in comparison with nanostructured carbons. PMID:21687889

  18. In Silico Design of Highly Selective Mo-V-Te-Nb-O Mixed Metal Oxide Catalysts for Ammoxidation and Oxidative Dehydrogenation of Propane and Ethane.

    PubMed

    Cheng, Mu-Jeng; Goddard, William A

    2015-10-21

    We used density functional theory quantum mechanics with periodic boundary conditions to determine the atomistic mechanism underlying catalytic activation of propane by the M1 phase of Mo-V-Nb-Te-O mixed metal oxides. We find that propane is activated by Te═O through our recently established reduction-coupled oxo activation mechanism. More importantly, we find that the C-H activation activity of Te═O is controlled by the distribution of nearby V atoms, leading to a range of activation barriers from 34 to 23 kcal/mol. On the basis of the new insight into this mechanism, we propose a synthesis strategy that we expect to form a much more selective single-phase Mo-V-Nb-Te-O catalyst. PMID:26423704

  19. Dehydrogenation of propane over chromia-pillared zirconium phosphate catalysts

    SciTech Connect

    Perez-Reina, F.J.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.

    1999-11-23

    Two series of porous chromia-pillared {alpha}-zirconium phosphate materials, prepared using two different methods of colloidization of the initial phase and with variable chromium contents (CrZrP-Xa and CrZrP-Xb) have been tested in the oxidative and nonoxidative dehydrogenation of propane in a flow reactor at atmospheric pressure. All catalysts are highly selective to propene under nonoxidative conditions at 823 K. In both series of catalysts, the initial activity increases with the chromium content, but generally CrZrP-Xb catalysts are more active than those of series CrZrP-Xa, which is in good agreement with their higher chromium contents and greater dispersions. In all cases, deactivation was detected due to coke formed from undesired reactions. When the reactions were carried out under oxidative conditions at 673 K, the activities were enhanced and the observed deactivation was minimum. The activities found vary between 0.47 and 1.31 {micro}mol of propene g{sup {minus}1} s{sup {minus}1} and are maintained after 200 min of reaction. These activity values were also related to the chromium content, being slightly higher for CrZrP-Xb materials. A parallel study to evaluate the influence of acidity in the obtained results has been carried out. The activities found of these catalysts seem to be related to the presence of Cr(III) centers with vacancies in their coordination sphere. These vacancies, in nonoxidative conditions, can activate the reactive molecules originating propene and hydrogen. On the other hand, in an oxidative atmosphere, Cr(III) species can activate oxygen molecules, through an electronic transference process, yielding propene and water.

  20. Effects of Al2O3 phase and Cl component on dehydrogenation of propane

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Liu, Changcheng; Ma, Aizeng; Rong, Junfeng; Da, Zhijian; Zheng, Aiguo; Qin, Ling

    2016-04-01

    The effects of two Al2O3 phases, γ- and θ-Al2O3, and Cl component on the performances of Pt-Al2O3 catalysts in the dehydrogenation of propane were investigated in this work. The catalysts were systematically characterized by various techniques, such as scanning transmission electron microscopy (STEM), temperature-programmed desorption with ammonia as probe molecules (NH3-TPD) and temperature-programmed oxidation (TPO). The characterizations and catalytic results show that: (i) the pore structures and acid properties of the two Al2O3 phases can change the quantity, location and property of the carbon deposition, (ii) the existence of Cl plays a significant role on the agglomeration of Pt particles and carbon deposition, which further influence the catalytic performances of Pt-Al2O3 catalysts with different support phases for propane dehydrogenation.

  1. Isolated FeII on Silica As a Selective Propane Dehydrogenation Catalyst

    SciTech Connect

    Hu, Bo; Schweitzer, Neil M.; Zhang, Guanghui; Kraft, Steven J.; Childers, David J.; Lanci, Michael P.; Miller, Jeffrey T.; Hock, Adam S.

    2015-04-17

    ABSTRACT: We report a comparative study of isolated FeII, iron oxide particles, and metallic nanoparticles on silica for non-oxidative propane dehydrogenation. It was found that the most selective catalyst was an isolated FeII species on silica prepared by grafting the open cyclopentadienide iron complex, bis(2,4-dimethyl-1,3-pentadienide) iron(II) or Fe(oCp)2. The grafting and evolution of the surface species was elucidated by 1H NMR, diffuse reflectance infrared Fourier transform spectroscopy and X-ray absorption spectroscopies. The oxidation state and local structure of surface Fe were characterized by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure. The initial grafting of iron proceeds by one surface hydroxyl Si-OH reacting with Fe(oCp)2 to release one diene ligand (oCpH), generating a SiO2-bound FeII(oCp) species, 1-FeoCp. Subsequent treatment with H2 at 400 °C leads to loss of the remaining diene ligand and formation of nanosized iron oxide clusters, 1-C. Dispersion of these Fe oxide clusters occurs at 650 °C, forming an isolated, ligand-free FeII on silica, 1-FeII, which is catalytically active and highly selective (~99%) for propane dehydrogenation to propene. Under reaction conditions, there is no evidence of metallic Fe by in situ XANES. For comparison, metallic Fe nanoparticles, 2-NP-Fe0, were independently prepared by grafting Fe[N(SiMe3)2]2 onto silica, 2-FeN*, and reducing it at 650 °C in H2. The Fe NPs were highly active for propane conversion but showed poor selectivity (~14%) to propene. Independently prepared Fe oxide clusters on silica display a low activity. The sum of these results suggests that selective propane dehydrogenation occurs at isolated FeII sites.

  2. Preparation of platinum nanoparticle catalyst for propane dehydrogenation.

    PubMed

    Li, Jun; Wang, Jun; Ma, Zhanhua; Sun, Lanyi; Hu, Yangdong

    2014-09-01

    Supported Pt nanoparticle catalysts were prepared by combing a chemical reduction method with an ultrasonic sonication loading method. Several techniques including transmission electron microscopy (TEM), nitrogen sorption technique and pyridine adsorption Fourier-transform infrared (Py-IR) were applied to characterize the physicochemical properties of these catalysts. The catalytic performance of catalysts was evaluated in the dehydrogenation of propane. The influence of the preparation method of Pt nanoparticles, the ratio of Polyvinyl Pyrrolidone (PVP) to Pt, loading method and different supports on the catalytic performance was investigated. PVP is useful for controlling the size of Pt nanoparticles and a PVP/Pt ratio of 15 is favorable to achieve a good catalytic performance. NaBH4 reduction is better than ethanol refluxing in preparing Pt nanoparticles. The ultrasonic sonication is effective to load the Pt nanoparticles onto the support channels. The mesoporous alumina proved to be a good catalyst support due to its high surface area and unique pore structure. PMID:25924358

  3. In situ UV-vis-NIR diffuse reflectance and Raman spectroscopy and catalytic activity studies of propane oxidative dehydrogenation over supported CrO3/ZrO2 catalysts.

    PubMed

    Malleswara Rao, T V; Deo, Goutam; Jehng, Jih-Mirn; Wachs, Israel E

    2004-08-17

    The molecular structures, oxidation states, and reactivity of 3 and 6% CrO3/ZrO2 catalysts prepared by incipient wetness impregnation were examined under different conditions. The in situ Raman spectroscopic studies under dehydrated conditions reveal that the 3 and 6% CrO3/ZrO2 catalysts possess equal amounts of monochromate and polychromate species. Consequently, monolayer coverage on this ZrO2 support is about 3% CrO3. The 6% CrO3/ZrO2 possesses an additional Raman band due to Cr2O3 crystals corresponding to the remaining 3% CrO3. Furthermore, during reaction conditions the polychromate species is preferentially reduced, the monochromate species are slightly affected, and the Cr2O3 crystals are not affected. The in situ UV-vis-NIR diffuse reflectance spectroscopy results reveal that under steady-state reaction conditions the extent of reduction and edge energy position of surface Cr6+ cations increase with an increase in reduction environment for the 3 and 6% CrO3/ZrO2 samples. Propane oxidative dehydrogenation (ODH) studies reveal that the catalytic activity expressed in moles of propane converted per gram catalyst per second is similar for the two catalysts, which is consistent with equal amounts of molecularly dispersed chromia present. The turnover frequency for the 6% CrO3/ZrO2 catalyst is, however, smaller than that for the 3% CrO3/ZrO2 sample due to the presence of Cr2O3 crystals, which are relatively inactive for propane ODH. For this catalytic system and for the experimental conditions used, propene, CO, and CO2 are primary products. Furthermore, the 33-39% propene selectivity is not affected by the C3H8/O2 ratio for both catalysts. Structure-reactivity studies suggest that the molecularly dispersed species are present in equal amounts in the 3 and 6% CrO3/ZrO2 samples as Cr6+ monochromate and polychromate species are the most effective catalytic active sites taking part in the propane ODH reaction. PMID:15301500

  4. Novel Pt/Mg(In)(Al)O catalysts for ethane and propane dehydrogenation

    SciTech Connect

    Sun, Pingping; Siddiqi, Georges; Vining, William C.; Chi, Miaofang; Bell, Alexis T.

    2011-10-28

    Catalysts for the dehydrogenation of light alkanes were prepared by dispersing Pt on the surface of a calcined hydrotalcite-like support containing indium, Mg(In)(Al)O. Upon reduction in H{sub 2} at temperatures above 673 K, bimetallic particles of PtIn are observed by TEM, which have an average diameter of 1 nm. Analysis of Pt LIII-edge extended X-ray absorption fine structure (EXAFS) data shows that the In content of the bimetallic particles increases with increasing bulk In/Pt ratio and reduction temperature. Pt LIII-edge X-ray absorption near edge structure (XANES) indicates that an increasing donation of electronic charge from In to Pt occurs with increasing In content in the PtIn particles. The activity and selectivity of the Pt/Mg(In)(Al)O catalysts for ethane and propane dehydrogenation reactions are strongly dependent on the bulk In/Pt ratio. For both reactants, maximum activity was achieved for a bulk In/Pt ratio of 0.48, and at this In/Pt ratio, the selectivity to alkene was nearly 100%. Coke deposition was observed after catalyst use for either ethane or propane dehydrogenation, and it was observed that the alloying of Pt with In greatly reduced the amount of coke deposited. Characterization of the deposit by Raman spectroscopy indicates that the coke is present as highly disordered graphite particles <30 nm in diameter. While the amount of coke deposited during ethane and propane dehydrogenation are comparable, the effects on activity are dependent on reactant composition. Coke deposition had no effect on ethane dehydrogenation activity, but caused a loss in propane dehydrogenation activity. This difference is attributed to the greater ease with which coke produced on the surface of PtIn nanoparticles migrates to the support during ethane dehydrogenation versus propane dehydrogenation.

  5. Carbon dynamics on the molybdenum carbide surface during catalytic propane dehydrogenation.

    PubMed

    Frank, Benjamin; Cotter, Thomas P; Schuster, Manfred E; Schlögl, Robert; Trunschke, Annette

    2013-12-01

    The effect of the gas-phase chemical potential on surface chemistry and reactivity of molybdenum carbide has been investigated in catalytic reactions of propane in oxidizing and reducing reactant mixtures by adding H2, O2, H2O, and CO2 to a C3H8/N2 feed. The balance between surface oxidation state, phase stability, carbon deposition, and the complex reaction network involving dehydrogenation reactions, hydrogenolysis, metathesis, water-gas shift reaction, hydrogenation, and steam reforming is discussed. Raman spectroscopy and a surface-sensitive study by means of in situ X-ray photoelectron spectroscopy evidence that the dynamic formation of surface carbon species under a reducing atmosphere strongly shifts the product spectrum to the C3-alkene at the expense of hydrogenolysis products. A similar response of selectivity, which is accompanied by a boost of activity, is observed by tuning the oxidation state of Mo in the presence of mild oxidants, such as H2O and CO2, in the feed as well as by V doping. The results obtained allow us to draw a picture of the active catalyst surface and to propose a structure-activity correlation as a map for catalyst optimization. PMID:24248701

  6. Effect of ultrasonic irradiation on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation.

    PubMed

    Liu, Hui; Zhang, Shaobo; Zhou, Yuming; Zhang, Yiwei; Bai, Linyang; Huang, Li

    2011-01-01

    Effects of ultrasonic irradiation on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation were studied. XRD, TEM and TPDA were used to characterize the catalysts. From the results of XRD, the structure of ZSM-5 was not destroyed by the ultrasound. Ultrasound promoted the dispersion of Pt on the surface of the carrier during impregnation and decreased the size of Pt particles. Compared with the catalyst prepared by conventional impregnation, the supported catalyst prepared by ultrasonic irradiation showed better catalytic activity in propane dehydrogenation. PMID:20452811

  7. Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons

    DOEpatents

    Kung, Harold H.; Chaar, Mohamed A.

    1988-01-01

    Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons is carried out over metal vanadate catalysts under oxidizing conditions. The vanadate catalysts are represented by the formulas M.sub.3 (VO.sub.4).sub.2 and MV.sub.2 O.sub.6, M representing Mg, Zn, Ca, Pb, or Cd. The reaction is carried out in the presence of oxygen, but the formation of oxygenate by-products is suppressed.

  8. Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons

    DOEpatents

    Kung, H.H.; Chaar, M.A.

    1988-10-11

    Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons is carried out over metal vanadate catalysts under oxidizing conditions. The vanadate catalysts are represented by the formulas M[sub 3](VO[sub 4])[sub 2] and MV[sub 2]O[sub 6], M representing Mg, Zn, Ca, Pb, or Cd. The reaction is carried out in the presence of oxygen, but the formation of oxygenate by-products is suppressed.

  9. Selective glycerol oxidation by electrocatalytic dehydrogenation.

    PubMed

    Kim, Hyung Ju; Lee, Jechan; Green, Sara K; Huber, George W; Kim, Won Bae

    2014-04-01

    This study demonstrates that an electrochemical dehydrogenation process can be used to oxidize glycerol to glyceraldehyde and glyceric acid even without using stoichiometric chemical oxidants. A glyceric acid selectivity of 87.0 % at 91.8 % glycerol conversion was obtained in an electrocatalytic batch reactor. A continuous-flow electrocatalytic reactor had over an 80 % high glyceric acid selectivity at 10 % glycerol conversion, as well as greater reaction rates than either an electrocatalytic or a conventional catalytic batch reactor. PMID:24664518

  10. Microchannel apparatus and methods of conducting catalyzed oxidative dehydrogenation

    DOEpatents

    Tonkovich, Anna Lee; Yang, Bin; Perry, Steven T.; Mazanec, Terry; Arora, Ravi; Daly, Francis P.; Long, Richard; Yuschak, Thomas D.; Neagle, Paul W.; Glass, Amanda

    2011-08-16

    Methods of oxidative dehydrogenation are described. Surprisingly, Pd and Au alloys of Pt have been discovered to be superior for oxidative dehydrogenation in microchannels. Methods of forming these catalysts via an electroless plating methodology are also described. An apparatus design that minimizes heat transfer to the apparatus' exterior is also described.

  11. Ultra-dispersed Pt nanoparticles on SAPO-34/γ-Al2O3 support for efficient propane dehydrogenation.

    PubMed

    Chu, Yue; Zhang, Qiang; Wu, Tongwei; Nawaz, Zeeshan; Wang, Yao; Wei, Fei

    2014-09-01

    Ultra-dispersed precious metal nanoparticles with good thermal stability are highly required for heterogeneous catalysis. However, the efficient and effective strategy to disperse ultra-fine precious metal nanoparticles at high reaction temperature is still not fully understood yet. In this contribution, a family of catalysts with ultra-small Pt nanoparticles were prepared using impregnation method by adjusting the zeolite content in the SAPO-34 and γ-Al2O3 mixed support. The effect of Pt nanoparticle size on the catalytic activity, selectivity, and stability was investigated in the propane dehydrogenation reaction. Catalyst with smaller Pt particles exhibits better catalytic performance. Both the highest Pt dispersion and the best catalytic activity can be achieved by using SAPO-34 and γ-Al2O3 mixed support with 70 wt.% of SAPO-34. The size and structure of the Pt nanoparticles on the optimal catalyst were characterized by transmission electron microscopy. Pt nanoparticles with an average size of 1.32 nm were observed. There were stronger metal-support interactions between the oxidized tin species and Pt particles on SAPO-34 support compared to that on γ-Al2O3 catalyst. These lead to high Pt dispersion and consequently good catalytic performance. PMID:25924347

  12. Oxidant-free dehydrogenative coupling reactions via hydrogen evolution.

    PubMed

    He, Ke-Han; Li, Yang

    2014-10-01

    Oxidant-free dehydrogenative coupling reactions: Recently, coupling reactions have followed a novel strategy for the construction of C==C, C==N, C==P, and S==S bonds by dehydrogenation without using any extra oxidant, via H2 evolution. These breakthroughs inspire a new direction in the construction of chemical bonds, towards more sustainable, highly atom-economical, and environmentally benign synthetic methods. PMID:25139249

  13. Operando Raman spectroscopy study on the deactivation of Pt/Al2O3 and Pt-Sn/Al2O3 propane dehydrogenation catalysts.

    PubMed

    Sattler, Jesper J H B; Beale, Andrew M; Weckhuysen, Bert M

    2013-08-01

    The deactivation of 0.5 wt% Pt/Al2O3 and 0.5 wt% Pt-1.5 wt% Sn/Al2O3 catalysts has been studied by operando Raman spectroscopy during the dehydrogenation of propane and subsequent regeneration in air for 10 successive dehydrogenation-regeneration cycles. Furthermore, the reaction feed was altered by using different propane/propene/hydrogen ratios. It was found that the addition of hydrogen to the feed increases the catalyst performance and decreases the formation of coke deposits, as was revealed by thermogravimetrical analysis. The positive effect of hydrogen on the catalyst performance is comparable to the addition of Sn, a promoter element which increases both the propane conversion and propene selectivity. Operando Raman spectroscopy showed that hydrogen altered the nature of the coke deposits formed during propane dehydrogenation. Due to this approach it was possible to perform a systematic deconvolution procedure on the Raman spectra. By analysing the related intensity, band position and bandwidth of the different Raman features, it was determined that smaller graphite crystallites, which have less defects, are formed when the partial pressure of hydrogen in the feed was increased. PMID:23615824

  14. Oxidative Dehydrogenative Couplings of Pyrazol-5-amines Selectively Forming Azopyrroles

    PubMed Central

    2015-01-01

    New oxidative dehydrogenative couplings of pyrazol-5-amines for the selective synthesis of azopyrrole derivatives have been described. The former reaction simultaneously installs C–I and N–N bonds through iodination and oxidation, whereas the latter involved a copper-catalyzed oxidative coupling process. The resulting iodo-substituted azopyrroles were employed by treatment with various terminal alkynes through Sonogashira cross-coupling leading to new azo compounds. PMID:24731223

  15. Molybdenum Catalyzed Ammonia Borane Dehydrogenation: Oxidation State Specific Mechanisms

    PubMed Central

    2015-01-01

    Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal–arene interactions. Both a Mo0 N2 complex, 5, and a MoII bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.0 equiv of H2. The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (MoII(H)2, [MoII(H)]+, and [MoIV(H)3]+) relevant to AB chemistry were characterized. PMID:25034459

  16. Room temperature dehydrogenation of ethane, propane, linear alkanes C4-C8, and some cyclic alkanes by titanium-carbon multiple bonds.

    PubMed

    Crestani, Marco G; Hickey, Anne K; Gao, Xinfeng; Pinter, Balazs; Cavaliere, Vincent N; Ito, Jun-Ichi; Chen, Chun-Hsing; Mindiola, Daniel J

    2013-10-01

    The transient titanium neopentylidyne, [(PNP)Ti≡C(t)Bu] (A; PNP(-)≡N[2-P(i)Pr2-4-methylphenyl]2(-)), dehydrogenates ethane to ethylene at room temperature over 24 h, by sequential 1,2-CH bond addition and β-hydrogen abstraction to afford [(PNP)Ti(η(2)-H2C═CH2)(CH2(t)Bu)] (1). Intermediate A can also dehydrogenate propane to propene, albeit not cleanly, as well as linear and volatile alkanes C4-C6 to form isolable α-olefin complexes of the type, [(PNP)Ti(η(2)-H2C═CHR)(CH2(t)Bu)] (R = CH3 (2), CH2CH3 (3), (n)Pr (4), and (n)Bu (5)). Complexes 1-5 can be independently prepared from [(PNP)Ti═CH(t)Bu(OTf)] and the corresponding alkylating reagents, LiCH2CHR (R = H, CH3(unstable), CH2CH3, (n)Pr, and (n)Bu). Olefin complexes 1 and 3-5 have all been characterized by a diverse array of multinuclear NMR spectroscopic experiments including (1)H-(31)P HOESY, and in the case of the α-olefin adducts 2-5, formation of mixtures of two diastereomers (each with their corresponding pair of enantiomers) has been unequivocally established. The latter has been spectroscopically elucidated by NMR via C-H coupled and decoupled (1)H-(13)C multiplicity edited gHSQC, (1)H-(31)P HMBC, and dqfCOSY experiments. Heavier linear alkanes (C7 and C8) are also dehydrogenated by A to form [(PNP)Ti(η(2)-H2C═CH(n)Pentyl)(CH2(t)Bu)] (6) and [(PNP)Ti(η(2)-H2C═CH(n)Hexyl)(CH2(t)Bu)] (7), respectively, but these species are unstable but can exchange with ethylene (1 atm) to form 1 and the free α-olefin. Complex 1 exchanges with D2C═CD2 with concomitant release of H2C═CH2. In addition, deuterium incorporation is observed in the neopentyl ligand as a result of this process. Cyclohexane and methylcyclohexane can be also dehydrogenated by transient A, and in the case of cyclohexane, ethylene (1 atm) can trap the [(PNP)Ti(CH2(t)Bu)] fragment to form 1. Dehydrogenation of the alkane is not rate-determining since pentane and pentane-d12 can be dehydrogenated to 4 and 4-d12 with comparable

  17. Platinum-Promoted Ga/Al2O3 as Highly Active, Selective, and Stable Catalyst for the Dehydrogenation of Propane**

    PubMed Central

    Sattler, Jesper J H B; Gonzalez-Jimenez, Ines D; Luo, Lin; Stears, Brien A; Malek, Andrzej; Barton, David G; Kilos, Beata A; Kaminsky, Mark P; Verhoeven, Tiny W G M; Koers, Eline J; Baldus, Marc; Weckhuysen, Bert M

    2014-01-01

    A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt % Ga, and 0.25 wt % K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga3+ species are the active species and where Pt functions as a promoter. PMID:24989975

  18. Structure-property relationships of BaCeO perovskites for the oxidative dehydrogenation of alkanes

    SciTech Connect

    Nenoff, T.M.; Jackson, N.B.; Miller, J.E.; Sault, A.G.; Trudell, D.

    1997-12-01

    The oxidative dehydrogenation (ODH) reactions for the formation of two important organic feedstocks ethylene and propylene are of great interest because of the potential in capital and energy savings associated with these reactions. Theoretically, ODH can achieve high conversions of the starting materials (ethane and propane) at lower temperatures than conventional dehydrogenation reactions. The important focus in this study of ODH catalysts is the development of a structure-property relationship for catalyst with respect to selectivity, so as to avoid the more thermodynamically favorable combustion reaction. Catalysts for the ODH reaction generally consist of mixed metal oxides. Since for the most selective catalyst lattice oxygen is known to participate in the reaction, catalysts are sought with surface oxygen atoms that are labile enough to perform dehydrogenation, but not so plentiful or weakly bound as to promote complete combustion. Also, catalysts must be able to replenish surface oxygen by transport from the bulk. Perovskite materials are candidates to fulfill these requirements. The authors are studying BaCeO{sub 3} perovskites doped with elements such as Ca, Mg, and Sr. During the ODH of the alkanes at high temperatures, the perovskite structure is not retained and a mixture of carbonates and oxides is formed, as revealed by XRD. While the Ca doped materials showed enhanced total combustion activity below 600 C, they only showed enhanced alkene production at 700 C. Bulk structural and surface changes, as monitored by powder X-ray diffraction, and X-ray photoelectron spectroscopy are being correlated with activity in order to understand the factors affecting catalyst performance, and to modify catalyst formulations to improve conversion and selectivity.

  19. Pd-Ag Membrane Coupled to a Two-Zone Fluidized Bed Reactor (TZFBR) for Propane Dehydrogenation on a Pt-Sn/MgAl2O4 Catalyst.

    PubMed

    Medrano, José-Antonio; Julián, Ignacio; Herguido, Javier; Menéndez, Miguel

    2013-01-01

    Several reactor configurations have been tested for catalytic propane dehydrogenation employing Pt-Sn/MgAl2O4 as a catalyst. Pd-Ag alloy membranes coupled to the multifunctional Two-Zone Fluidized Bed Reactor (TZFBR) provide an improvement in propane conversion by hydrogen removal from the reaction bed through the inorganic membrane in addition to in situ catalyst regeneration. Twofold process intensification is thereby achieved when compared to the use of traditional fluidized bed reactors (FBR), where coke formation and thermodynamic equilibrium represent important process limitations. Experiments were carried out at 500-575 °C and with catalyst mass to molar flow of fed propane ratios between 15.1 and 35.2 g min mmol-1, employing three different reactor configurations: FBR, TZFBR and TZFBR + Membrane (TZFBR + MB). The results in the FBR showed catalyst deactivation, which was faster at high temperatures. In contrast, by employing the TZFBR with the optimum regenerative agent flow (diluted oxygen), the process activity was sustained throughout the time on stream. The TZFBR + MB showed promising results in catalytic propane dehydrogenation, displacing the reaction towards higher propylene production and giving the best results among the different reactor configurations studied. Furthermore, the results obtained in this study were better than those reported on conventional reactors. PMID:24958620

  20. Pd-Ag Membrane Coupled to a Two-Zone Fluidized Bed Reactor (TZFBR) for Propane Dehydrogenation on a Pt-Sn/MgAl2O4 Catalyst

    PubMed Central

    Medrano, José-Antonio; Julián, Ignacio; Herguido, Javier; Menéndez, Miguel

    2013-01-01

    Several reactor configurations have been tested for catalytic propane dehydrogenation employing Pt-Sn/MgAl2O4 as a catalyst. Pd-Ag alloy membranes coupled to the multifunctional Two-Zone Fluidized Bed Reactor (TZFBR) provide an improvement in propane conversion by hydrogen removal from the reaction bed through the inorganic membrane in addition to in situ catalyst regeneration. Twofold process intensification is thereby achieved when compared to the use of traditional fluidized bed reactors (FBR), where coke formation and thermodynamic equilibrium represent important process limitations. Experiments were carried out at 500–575 °C and with catalyst mass to molar flow of fed propane ratios between 15.1 and 35.2 g min mmol−1, employing three different reactor configurations: FBR, TZFBR and TZFBR + Membrane (TZFBR + MB). The results in the FBR showed catalyst deactivation, which was faster at high temperatures. In contrast, by employing the TZFBR with the optimum regenerative agent flow (diluted oxygen), the process activity was sustained throughout the time on stream. The TZFBR + MB showed promising results in catalytic propane dehydrogenation, displacing the reaction towards higher propylene production and giving the best results among the different reactor configurations studied. Furthermore, the results obtained in this study were better than those reported on conventional reactors. PMID:24958620

  1. Propane dehydrogenation over Pt-Cu bimetallic catalysts: the nature of coke deposition and the role of copper

    NASA Astrophysics Data System (ADS)

    Han, Zhiping; Li, Shuirong; Jiang, Feng; Wang, Tuo; Ma, Xinbin; Gong, Jinlong

    2014-08-01

    This paper describes an investigation of the promotional effect of Cu on the catalytic performance of Pt/Al2O3 catalysts for propane dehydrogenation. We have shown that Pt/Al2O3 catalysts possess higher propylene selectivity and lower deactivation rate as well as enhanced anti-coking ability upon Cu addition. The optimized loading content of Cu is 0.5 wt%, which increases the propylene selectivity to 90.8% with a propylene yield of 36.5%. The origin of the enhanced catalytic performance and anti-coking ability of the Pt-Cu/Al2O3 catalyst is ascribed to the intimate interaction between Pt and Cu, which is confirmed by the change of particle morphology and atomic electronic environment of the catalyst. The Pt-Cu interaction inhibits propylene adsorption and elevates the energy barrier of C-C bond rupture. The inhibited propylene adsorption diminishes the possibility of coke formation and suppresses the cracking reaction towards the formation of lighter hydrocarbons on Pt-Cu/Al2O3, while a higher energy barrier for C-C bond cleavage suppresses the methane formation.

  2. Propane dehydrogenation over Pt-Cu bimetallic catalysts: the nature of coke deposition and the role of copper.

    PubMed

    Han, Zhiping; Li, Shuirong; Jiang, Feng; Wang, Tuo; Ma, Xinbin; Gong, Jinlong

    2014-09-01

    This paper describes an investigation of the promotional effect of Cu on the catalytic performance of Pt/Al2O3 catalysts for propane dehydrogenation. We have shown that Pt/Al2O3 catalysts possess higher propylene selectivity and lower deactivation rate as well as enhanced anti-coking ability upon Cu addition. The optimized loading content of Cu is 0.5 wt%, which increases the propylene selectivity to 90.8% with a propylene yield of 36.5%. The origin of the enhanced catalytic performance and anti-coking ability of the Pt-Cu/Al2O3 catalyst is ascribed to the intimate interaction between Pt and Cu, which is confirmed by the change of particle morphology and atomic electronic environment of the catalyst. The Pt-Cu interaction inhibits propylene adsorption and elevates the energy barrier of C-C bond rupture. The inhibited propylene adsorption diminishes the possibility of coke formation and suppresses the cracking reaction towards the formation of lighter hydrocarbons on Pt-Cu/Al2O3, while a higher energy barrier for C-C bond cleavage suppresses the methane formation. PMID:24933477

  3. Radiolytic oxidation of propane. [Gamma radiation

    SciTech Connect

    Gupta, A.K.

    1983-01-01

    The Co-60 ..gamma.. radiolysis of gaseous propane was studied at 100 torr pressure and 25/sup 0/C, both pure and with 10% added oxygen. In the unscavenged system the major products and their G-values were hydrogen, 4.99; methane, 1.30; ethane, 1.95; iso-butane, 0.61; n-butane, 0.25; i-pentane, 0.42; n-pentane, 0.14; and hexanes, 0.89. Minor products were heptanes, 0.082; octanes, 0.067; nonanes, 0.088, and decanes, 0.033. Small yields of ethylene and propylene were also observed. Yields in the presence of 10% added oxygen were hydrogen, 1.87; methane, 0.83; and ethane, 1.22. Higher saturated hydrocarbons were eliminated. The reaction scheme for formation of major products was examined using computer modeling based on 24 reactions in the unscavenged system and 28 reactions in the propane-oxygen system. Yields could be brought into agreement with the data within experimental error in nearly all cases, but in the pure propane system it was necessary to assume that the molecular hydrogen yield was accompanied by the deposition of polymer on the vessel wall.

  4. Palladium-catalyzed synthesis of dibenzophosphole oxides via intramolecular dehydrogenative cyclization.

    PubMed

    Kuninobu, Yoichiro; Yoshida, Takuya; Takai, Kazuhiko

    2011-09-16

    Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine-hydrogen and carbon-hydrogen bond cleavage in the presence of a catalytic amount of palladium(II) acetate, Pd(OAc)(2). By using this reaction, a ladder-type dibenzophosphole oxide could also be synthesized by double intramolecular dehydrogenative cyclization. PMID:21819045

  5. Oxidative dehydrogenation of ethane on dynamically rearranging supported chloride catalysts.

    PubMed

    Gärtner, Christian A; van Veen, André C; Lercher, Johannes A

    2014-09-10

    Ethane is oxidatively dehydrogenated with a selectivity up to 95% on catalysts comprising a mixed molten alkali chloride supported on a mildly redox-active Dy2O3-doped MgO. The reactive oxyanionic OCl(-) species acting as active sites are catalytically formed by oxidation of Cl(-) at the MgO surface. Under reaction conditions this site is regenerated by O2, dissolving first in the alkali chloride melt, and in the second step dissociating and replenishing the oxygen vacancies on MgO. The oxyanion reactively dehydrogenates ethane at the melt-gas phase interface with nearly ideal selectivity. Thus, the reaction is concluded to proceed via two coupled steps following a Mars-van-Krevelen-mechanism at the solid-liquid and gas-liquid interface. The dissociation of O2 and/or the oxidation of Cl(-) at the melt-solid interface is concluded to have the lowest forward rate constants. The compositions of the oxide core and the molten chloride shell control the catalytic activity via the redox potential of the metal oxide and of the OCl(-). Traces of water may be present in the molten chloride under reaction conditions, but the specific impact of this water is not obvious at present. The spatial separation of oxygen and ethane activation sites and the dynamic rearrangement of the surface anions and cations, preventing the exposure of coordinatively unsaturated cations, are concluded to be the origin of the surprisingly high olefin selectivity. PMID:25118821

  6. Adsorption of propane, isopropyl, and hydrogen on cluster models of the M1 phase of Mo-V-Te-Nb-O mixed metal oxide catalyst

    SciTech Connect

    Govindasamy, Agalya; Muthukumar, Kaliappan; Yu, Junjun; Xu, Ye; Guliants, Vadim V.

    2010-01-01

    The Mo-V-Te-Nb-O mixed metal oxide catalyst possessing the M1 phase structure is uniquely capable of directly converting propane into acrylonitrile. However, the mechanism of this complex eight-electron transformation, which includes a series of oxidative H-abstraction and N-insertion steps, remains poorly understood. We have conducted a density functional theory study of cluster models of the proposed active and selective site for propane ammoxidation, including the adsorption of propane, isopropyl (CH{sub 3}CHCH{sub 3}), and H which are involved in the first step of this transformation, that is, the methylene C-H bond scission in propane, on these active site models. Among the surface oxygen species, the telluryl oxo (Te=O) is found to be the most nucleophilic. Whereas the adsorption of propane is weak regardless of the MO{sub x} species involved, isopropyl and H adsorption exhibits strong preference in the order of Te=O > V=O > bridging oxygens > empty Mo apical site, suggesting the importance of TeO{sub x} species for H abstraction. The adsorption energies of isopropyl and H and consequently the reaction energy of the initial dehydrogenation of propane are strongly dependent on the number of ab planes included in the cluster, which points to the need to employ multilayer cluster models to correctly capture the energetics of surface chemistry on this mixed metal oxide catalyst.

  7. Propane conversion on Ga-HZSM-5: Effect of aging on the dehydrogenating and acid functions using pyridine as an IR probe

    SciTech Connect

    Meriaudeau, P.; Naccache, C. ); Abdul Hamid, S.B. )

    1993-02-01

    Gallium-loaded zeolite (Ga-HZSM-5) catalysts have been extensively studied in the recent past, not only in respect of their interesting catalytic activity in the aromatization of C[sub 3]-C[sub 5] alkanes (Cyclar Process) but also in respect of theoretical considerations. There is clear evidence that in the reaction of alkanes these catalysts behave as bifunctional catalysts, the acid function being provided by the protons and the dehydrogenation function deriving from Ga[sub 2]O[sub 3] or Ga[sup n+] ions in ionic-exchange positions. Ga-HZSM-5 catalysts deactivate with time on-stream. The deactivation can result from poisoning of the acid centers and/or the dehydrogenating sites by coke deposition or from sintering or phase transformation of the dehydrogenating gallium species. The aim of the present study was to investigate the possible modifications of Ga centers and H[sup +] sites which may result from the propane reaction. The active centers were studied by infrared spectroscopy of adsorbed pyridine, pyridine adsorption being used to probe both H[sup +] and Al, Ga Lewis-acid centers. 11 refs., 2 figs., 1 tab.

  8. Moessbauer spectra of ferrite catalysts used in oxidative dehydrogenation

    NASA Technical Reports Server (NTRS)

    Cares, W. R.; Hightower, J. W.

    1971-01-01

    Room temperature Mossbauer spectroscopy was used to examine bulk changes which occur in low surface area CoFe2O4 and CuFe2O4 catalysts as a result of contact with various mixtures of trans-2-butene and O2 during oxidative dehydrogenation reactions at about 420 C. So long as there was at least some O2 in the gas phase, the CoFe2O4 spectrum was essentially unchanged. However, the spectrum changed from a random spinel in the oxidized state to an inverse spinel as it was reduced by oxide ion removal. The steady state catalyst lies very near the fully oxidized state. More dramatic solid state changes occurred as the CuFe2O4 underwent reduction. Under severe reduction, the ferrite was transformed into Cu and Fe3O4, but it could be reversibly recovered by oxidation. An intense doublet located near zero velocity persisted in all spectra of CuFe2O4 regardless of the state of reduction.

  9. Hybrid nanocarbon as a catalyst for direct dehydrogenation of propane: formation of an active and selective core-shell sp2/sp3 nanocomposite structure.

    PubMed

    Wang, Rui; Sun, Xiaoyan; Zhang, Bingsen; Sun, Xiaoying; Su, Dangsheng

    2014-05-19

    Hybrid nanocarbon, comprised of a diamond core and a graphitic shell with a variable sp(2)-/sp(3)-carbon ratio, is controllably obtained through sequential annealing treatment (550-1300 °C) of nanodiamond. The formation of sp(2) carbon increases with annealing temperature and the nanodiamond surface is reconstructed from amorphous into a well-ordered, onion-like carbon structure via an intermediate composite structure--a diamond core covered by a defective, curved graphene outer shell. Direct dehydrogenation of propane shows that the sp(2)-/sp(3)-nanocomposite exhibits superior catalytic performance to that of individual nanodiamond and graphitic nanocarbon. The optimum catalytic activity of the diamond/graphene composite depends on the maximum structural defectiveness and high chemical reactivity of the ketone groups. Ketone-type functional groups anchored on the defects/vacancies are active for propene formation; nevertheless, once the oxygen functional groups are desorbed, the defects/vacancies alone might be active sites responsible for the C-H bond activation of propane. PMID:24740731

  10. Catalytic dehydrogenation of propane by carbon dioxide: a medium-temperature thermochemical process for carbon dioxide utilisation.

    PubMed

    Du, X; Yao, B; Gonzalez-Cortes, S; Kuznetsov, V L; AlMegren, Hamid; Xiao, T; Edwards, P P

    2015-01-01

    The dehydrogenation of C3H8 in the presence of CO2 is an attractive catalytic route for C3H6 production. In studying the various possibilities to utilise CO2 to convert hydrocarbons using the sustainable energy source of solar thermal energy, thermodynamic calculations were carried out for the dehydrogenation of C3H8 using CO2for the process operating in the temperature range of 300-500 °C. Importantly, the results highlight the enhanced potential of C3H8 as compared to its lighter and heavier homologues (C2H6 and C4H10, respectively). To be utilised in this CO2 utilisation reaction the Gibbs free energy (ΔrGθm) of each reaction in the modelled, complete reacting system of the dehydrogenation of C3H8 in the presence of CO2 also indicate that further cracking of C3H6 will affect the ultimate yield and selectivity of the final products. In a parallel experimental study, catalytic tests of the dehydrogenation of C3H8 in the presence of CO2 over 5 wt%-Cr2O3/ZrO2 catalysts operating at 500 °C, atmospheric pressure, and for various C3H8 partial pressures and various overall GHSV (Gas Hourly Space Velocity) values. The results showed that an increase in the C3H8 partial pressure produced an inhibition of C3H8 conversion but, importantly, a promising enhancement of C3H6 selectivity. This phenomenon can be attributed to competitive adsorption on the catalyst between the generated C3H6 and inactivated C3H8, which inhibits any further cracking effect on C3H6 to produce by-products. As a comparison, the increase of the overall GHSV can also decrease the C3H8 conversion to a similar extent, but the further cracking of C3H6 cannot be limited. PMID:26392020

  11. Cobalt-promoted Iron Oxide Nanoparticles for the Selective Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Rutter, Matthew

    Recent work has shown that both cobalt and iron oxide nanoparticles are active for the oxidative dehydrogenation (ODH) of cyclohexane to benzene, the former more active than the latter. Further study has shown that the addition of gold species as a minority component into iron oxide nanocrystals increases the selectivity of the reaction to benzene. Since a primary motivation for this work is the addition of catalysts in jet fuels to facilitate the dehydrogenation and cracking reactions preceding their combustion, a low-cost, sacrificial catalyst is sought after. In this application, catalyst nanoparticles suspended in the fuel stream will dehydrogenate cyclic alkanes (cyclohexane) to their aromatic counterparts (benzene). Alkenes and aromatics have a much higher rate of combustion, which decreases the amount of uncombusted fuel in the exhaust, thereby increasing performance. As these catalysts are not recyclable, there is significant impetus to substitute cheaper base metals for expensive noble metals. In this work, iron oxide nanoparticles are doped with varying levels of cobalt to examine the effect of cobalt content and oxidation state on the selectivity and activity of the iron oxide for the oxidative dehydrogenation of cyclohexane, used as a model cyclic alkane in jet fuel. We have shown previously that small (˜5nm) cobalt oxide nanoparticles favor the production of benzene over the partial dehydrogenation products cyclohexene and cyclohexadiene, or the complete oxidation product carbon dioxide. It is the aim of this work to examine the surface of these cobalt-iron oxide nanoparticles to determine the conditions most favorable for this selective oxidative dehydrogenation. Cobalt-doped iron nanoparticles were prepared by a surfactant-free hydrothermal co-precipitation technique that enabled a high degree of composition control and size control. These samples were characterized via Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (XRD), X

  12. Synthesis and Evaluation of Nanostructured Gold-Iron Oxide Catalysts for the Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Wu, Peng

    Shape-controlled iron oxide and gold-iron oxide catalysts with a cubic inverse spinel structure were studied in this thesis for the oxidative dehydrogenation of cyclohexane. The structure of iron oxide and gold-iron oxide catalysts has no major impact on their oxidative dehydrogenation activity. However, the product selectivity is influenced. Both cyclohexene and benzene are formed on bare iron oxide nanoshapes, while benzene is the only dehydrogenation product in the presence of gold. The selectivity of benzene over CO2 depends strongly on the stability of the iron oxide support and the gold-support interaction. The highest benzene yield has been observed on gold-iron oxide octahedra. {111}-bound nanooctahedra are highly stable in reaction conditions at 300 °C, while {100}-bound nanocubes start to sinter above 250 °C. The highest benzene yield has been observed on gold-iron oxide nanooctahedra, which are likely to have gold atoms, and few-atom gold clusters strongly-bound on their surface. Cationic gold appears to be the active site for benzene formation. An all-organic method to prepare Au-FeOx nano-catalysts is needed due to the inconvenience of the half-organic, half-inorganic synthesis process discussed above. Several methods from the literature to prepare gold-iron oxide nanocomposites completely in organic solvents were reviewed and followed. FeOx Au synthesis procedures in literatures are initially designed for a Au content of over 70%. This approach was tried here to prepare composites with a much lower Au content (2-5 atom. %). Heat treatment is required to bond Au and FeOx NPs in the organic-phase syntheses. Au-FeOx-4 was obtained as a selective catalyst for the ODH of cyclohexane. A Audelta+ peak is observed in the UV-Vis spectrum of sample Au-FeOx-4. This different Au delta+ form may be cationic Au nano-clusters interacting with the FeOx support. It has been demonstrated that cationic gold is responsible for dehydrogenation behavior. Furthermore, the

  13. The chemical origin and catalytic activity of coinage metals: from oxidation to dehydrogenation.

    PubMed

    Syu, Cih-Ying; Yang, Hao-Wen; Hsu, Fu-Hsing; Wang, Jeng-Han

    2014-04-28

    The high oxidation activity of coinage metals (Cu, Ag and Au) has been widely applied in various important reactions, such as oxidation of carbon monoxide, alkenes or alcohols. The catalytic behavior of those inert metals has mostly been attributable to their size effect, the physical effect. In the present study, the chemical effects on their high oxidation activity have been investigated. We mechanistically examine the direct and oxidative dehydrogenation (partial oxidation) reactions of ethanol to acetaldehyde on a series of transition metals (groups 9, 10 and 11) with identical physical characteristics and varied chemical origins using density functional theory (DFT) calculations and electronic structure analyses at the GGA-PW91 level. The energetic results show that coinage metals have much lower activation energies and higher exothermicities for the oxidative dehydrogenation steps although they have higher energy for the direct dehydrogenation reaction. In the electronic structure analyses, coinage metals with saturated d bands can efficiently donate electrons to O* and OH*, or other electronegative adspecies, and better promote their p bands to higher energy levels. The negatively charged O* and OH* with high-lying p bands are responsible for lowering the energies in oxidative steps. The mechanistic understanding well explains the better oxidation activity of coinage metals and provides valuable information on their utilization in other useful applications, for example, the dehydrogenation process. PMID:24626959

  14. The effect of mixed HCl-KCl competitive adsorbate on Pt adsorption and catalytic properties of Pt-Sn/Al2O3 catalysts in propane dehydrogenation

    NASA Astrophysics Data System (ADS)

    Zangeneh, Farnaz Tahriri; Taeb, Abbas; Gholivand, Khodayar; Sahebdelfar, Saeed

    2015-12-01

    The effect of competitive adsorbate concentration and combination on the adsorption of H2PtCl6 onto γ-Al2O3 in the preparation and performance of PtSnK/γ-Al2O3 catalyst for propane dehydrogenation was investigated. The catalysts were prepared by sequential impregnation of Sn and Pt precursors. The effect of competitor concentration on Pt adsorption was studied by using hydrochloric acid (0.1-0.3 M) and the effect of pH was studied by using KCl/HCl mixtures at constant (0.1 M) total chloride ion concentration. The catalysts were characterized by nitrogen adsorption/desorption, XRD, XRF, SEM and CO chemisorption. The catalytic performance tests were carried out in a fixed-bed quartz reactor under kinetic controlled condition for proper catalyst screening. It was found that the corrosive competitor HCl could be partially substituted with KCl without appreciable impact on catalyst performance with the advantage of lower acid attack on the support and reduced leaching of the deposited tin. A model based on initial concentration and uptake of the adsorbates was developed to obtain the adsorption parameters. Values of 890 μmol/g and 600 lit/mol were obtained for adsorption site concentration of the tin-impregnated support and equilibrium constant for Pt adsorption, respectively, for HCl concentration range of 0.1-0.3 M.

  15. Study of the Low Temperature Oxidation of Propane

    PubMed Central

    Cord, Maximilien; Husson, Benoit; Huerta, Juan Carlos Lizardo; Herbinet, Olivier; Glaude, Pierre-Alexandre; Fournet, René; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Ruiz-Lopez, Manuel; Wang, Zhandong; Xie, Mingfeng; Cheng, Zhanjun; Qi, Fei

    2013-01-01

    The low-temperature oxidation of propane was investigated using a jet-stirred reactor at atmospheric pressure and two methods of analysis: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) with direct sampling through a molecular jet. The second method allowed the identification of products, such as molecules with hydroperoxy functions, which are not stable enough to be detected by gas chromatography. Mole fractions of the reactants and reaction products were measured as a function of the temperature (530-730 K), with a particular attention to reaction products involved in the low temperature oxidation, such as cyclic ethers, aldehydes, alcohols, ketones, and hydroperoxides. A new model has been obtained from an automatically generated one, which was used as a starting point, with a large number of re-estimated thermochemical and kinetic data. The kinetic data of the most sensitive reactions, i.e., isomerizations of alkylperoxy radicals and the subsequent decompositions, have been calculated at the CBS-QB3 level of theory. The model allows a satisfactory prediction of the experimental data. A flow rate analysis has allowed highlighting the important reaction channels. PMID:23181456

  16. Substituent-enabled oxidative dehydrogenative cross-coupling of 1,4-naphthoquinones with alkenes.

    PubMed

    Zhang, Chi; Wang, Meining; Fan, Zhoulong; Sun, Li-Ping; Zhang, Ao

    2014-08-15

    A Rh-catalyzed oxidative dehydrogenative cross-coupling of 1,4-naphthquinones with alkenes was achieved by using a substituent-enabled C(sp(2))-H functionalization (SEF) strategy. The method shows high functional group tolerance, broad substrate scope, and great potential for further functional transformations. PMID:25075553

  17. Parametric study of the partial oxidation of propane over nickel and platinum based catalysts

    NASA Astrophysics Data System (ADS)

    Mukka, Mayuri

    Hydrogen production though the partial oxidation of propane over 1%Pt/CeO 2 and 1%Ni/CeO2 catalysts was studied in a fixed-bed reactor. The purpose of the experiments was to study the pathways, priority and the sequence of reactions which occur over each catalyst system. A temperature of 600°C and O2/C3H8 ratio of 1.78 was used for all the runs. The space velocity was varied by varying the flowrates (100, 200, 300, 400 sccm), and also the catalyst loadings. Seven species were found at the outlet of the reactor (C3H8, O2, H2, CO, CO2, H2O and C3H 6). All the species except H2O were analyzed quantitatively by the gas chromatograph. The following reactions can occur during the process at 600°C: total oxidation, partial oxidation, steam reforming, dry reforming, water gas shift, dehydrogenation and water formation. Of these, a Gaussian elimination process yields four independent reactions. This results in ten sets of possible independent reactions. For each set, a material balance on the six outlet compositions allows the calculation of rates of each of the four reactions in the set. Sets containing negative rates for irreversible reactions are discarded. To confirm the validity of sets containing dry reforming, steam reforming and water gas shift, these reactions were carried out over the catalysts at the experimentally determined outlet conditions for the propane partial oxidation process. For the 1%Ni/CeO2 catalyst, both dry and steam reforming reactions were favorable, but the water gas shift reaction was not favorable. The activities of the 1%Pt/CeO2 catalyst for dry reforming and steam reforming were insignificant. The water gas shift reaction was not conducted over the 1%Pt/CeO2 catalyst as no feasible set contained this reaction. These results, coupled with the effect of weight hourly space velocity, allows us to evaluate the relative importance of each reaction in each allowable set as a function of contact time. The results indicate that the pathways

  18. Porous graphene-based material as an efficient metal free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene.

    PubMed

    Diao, Jiangyong; Liu, Hongyang; Wang, Jia; Feng, Zhenbao; Chen, Tong; Miao, Changxi; Yang, Weimin; Su, Dang Sheng

    2015-02-25

    Reduced porous graphene oxide as a metal free catalyst was selected for the oxidative dehydrogenation of ethylbenzene to styrene. It showed the best catalytic performance compared with other carbon materials (routinely reduced graphene oxide, graphite powder and oxidized carbon nanotubes) and commercial iron oxide. PMID:25625943

  19. Insights into the oxidative dehydrogenation of amines with nanoparticulate iridium oxide.

    PubMed

    Hammond, Ceri; Schümperli, Martin T; Hermans, Ive

    2013-09-23

    The aerobic oxidation of amines offers a promising route towards many versatile chemical compounds. Within this contribution, we extend our previous investigations of iridium oxide-catalyzed alcohol oxidation to amine substrates. In addition to demonstrating the versatility of this catalyst, particular attention is focused on the mechanisms of the reaction. Herein, we demonstrate that although amines are oxidized slower than the corresponding alcohols, the catalyst has a preference for amine substrates, and oxidizes various amines at turnover frequencies greater than other systems found in the open literature. Furthermore, the competition between double amine dehydrogenation, to yield the corresponding nitrile, and amine-imine coupling, to yield the corresponding coupled imine, has been found to arise from a competitive reaction pathway, and stems from an effect of substrate-to-metal ratio. Finally, the mechanism responsible for the formation of N-benzylidene-1-phenylmethanamine was examined, and attributed to the coupling of free benzyl amine substrate and benzaldehyde, formed in situ through hydrolysis of the primary reaction product, benzyl imine. PMID:23939827

  20. Heterogeneous Rhodium-Catalyzed Aerobic Oxidative Dehydrogenative Cross-Coupling: Nonsymmetrical Biaryl Amines.

    PubMed

    Matsumoto, Kenji; Yoshida, Masahiro; Shindo, Mitsuru

    2016-04-18

    The first heterogeneously catalyzed oxidative dehydrogenative cross-coupling of aryl amines is reported herein. 2-Naphthylamine analogues were reacted with various electron-rich arenes using a heterogeneous Rh/C catalyst under mild aerobic conditions, thus affording nonsymmetrical biaryl amines in excellent yields with high selectivities. This reaction provides a mild, operationally simple, and efficient approach for the synthesis of biaryls which are important to pharmaceutical and materials chemistry. PMID:26996772

  1. Visible-Light-Promoted Direct Amination of Phenols via Oxidative Cross-Dehydrogenative Coupling Reaction.

    PubMed

    Zhao, Yating; Huang, Binbin; Yang, Chao; Xia, Wujiong

    2016-07-15

    A transition-metal-free approach was disclosed for intermolecular aryl C-N bonds formation between phenols and cyclic anilines via cross-dehydrogenative coupling (CDC) amination that was mediated by visible light, wherein K2S2O8 served as an external oxidant. The salient features of this protocol include circumventing the requirement for prefunctionalized starting materials and achieving single regioselectivity of amination adducts at room temperature. PMID:27364730

  2. Oxidative dehydrogenation dimerization of propylene over bismuth oxide: kinetic and mechanistic studies

    SciTech Connect

    White, M.G.; Hightower, J.W.

    1983-07-01

    Classical kinetic experiments together with pulse microreactor studies involving deuterium and carbon-13-labeled isotopic tracers were used to investigate the oxidative dehydrogenation dimerization (OXDD) of propylene to 1,5-hexadiene and benzene over bismuth oxide between 748 and 898/sup 0/K. The kinetic data, which indicated that the OXDD reaction is of variable order with respect to oxygen and propylene concentrations, could be fit to rate equations based on either the Langmuir-Hinshelwood model or the Mars-van Krevelen model, although the former gave more linear Arrhenius plots. A significant kinetic isotope effect (k/sub H//k/sub D/ = 1.7 at 873/sup 0/K) shows that the rate-limiting step for the OXDD reaction involves C-H cleavage, and there is only a small amount of H/D scrambling among reactant and product molecules. Analysis of liquid products by infrared spectroscopy indicated that both 1,5-hexadiene and 1,3-cyclohexadiene are stable reaction intermediates; microreactor results involving unlabeled propylene, 1,5-hexadiene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene as reactants confirmed the infrared findings. Pulse microreactor experiments with /sup 13/C-labeled propylene clearly showed that deep oxidation (complete combustion) occurs via a consecutive-parallel network involving the partially oxidized intermediates as well as the starting propylene. Changes in the particle size do not alter the overall activity, although larger particles have lower selectivities for C/sub 6/ products than do smaller particles.

  3. Bulk binary ZrO2-based oxides as highly active alternative-type catalysts for non-oxidative isobutane dehydrogenation.

    PubMed

    Otroshchenko, Tatyana; Radnik, Jörg; Schneider, Matthias; Rodemerck, Uwe; Linke, David; Kondratenko, Evgenii V

    2016-06-21

    Bulk binary ZrO2-based oxides efficiently catalyse non-oxidative dehydrogenation of isobutane to isobutylene. Their activity strongly depends on the kind of second metal oxide. So designed CrZrOx showed superior activity to industrially relevant catalysts with supported Pt or CrOx species. It was also stable under alternating dehydrogenation and oxidative regeneration cycles over ca. 110 h under different reaction conditions between 550 and 600 °C. PMID:27277540

  4. Ethylbenzene oxidative dehydrogenation on MnO{sub x}/SiO{sub 2} catalysts

    SciTech Connect

    Craciun, R.; Dulamita, N.

    1999-04-01

    Supported MnO{sub x} on high surface area SiO{sub 2} (300 m{sup 2}/g) catalysts were successfully used in ethylbenzene oxidative dehydrogenation. X-ray diffraction and X-ray photoelectron spectroscopy were employed to characterize the structure of fresh and used MnO{sub x}/SiO{sub 2} catalysts. The MnO{sub x} catalysts were prepared using the pore volume impregnation method, with MnO{sub 2} loading varying from 0.7 wt % (Mn/Si = 0.005, atomic ratio) to 30 wt % (Mn/Si = 0.14). The changes in the crystalline structure and dispersion of supported MnO{sub x} were related to the precursor/support interaction and the conditions used during catalyst preparation. A possible mechanism for ethylbenzene conversion to styrene on MnO{sub x}/SiO{sub 2} catalysts is proposed, where lattice oxygen from crystalline MnO{sub 2} can be used in the oxidation or oxidative dehydrogenation processes. The high selectivity in styrene (at 723 K, 24% conversion with 76% selectivity in styrene) was related to the high concentration in the MnO{sub 2} phase from the MnO{sub x}/SiO{sub 2} catalysts. The formation of the Mn{sub 3}O{sub 4} phase, observed on the used catalysts, supports the proposed mechanism. These findings are of potential use for industrial applications, particularly in optimization of various oxidative dehydrogenation processes.

  5. Chemical kinetic modeling of propane oxidation behind shock waves

    NASA Technical Reports Server (NTRS)

    Mclain, A. G.; Jachimowski, C. J.

    1977-01-01

    The stoichiometric combustion of propane behind incident shock waves was studied experimentally and analytically over a temperature range from 1700 K to 2600 K and a pressure range from 1.2 to 1.9 atm. Measurements of the concentrations of carbon monoxide (CO) and carbon dioxide (CO2) and the product of the oxygen atom and carbon dioxide concentrations (O)(CO) were made after passage of the incident shock wave. A kinetic mechanism was developed which, when used in a computer program for a flowing, reacting gas behind an incident shock wave predicted experimentally measured results quite well. Ignition delay times from the literature were also predicted quite well. The kinetic mechanism consisted of 59 individual kinetic steps.

  6. Oxidative dehydrogenation of ethane at millisecond contact times: Effect of H{sub 2} addition

    SciTech Connect

    Bodke, A.S.; Henning, D.; Schmidt, L.D.; Bharadwaj, S.S.; Maj, J.J.; Siddall, J.

    2000-04-01

    The oxidative dehydrogenation of ethane using Pt/{alpha}-Al{sub 2}O{sub 3} and various bimetallic catalysts operating at {approximately}1,000 C and very short contact times is examined with H{sub 2} addition to the feed. When H{sub 2} is added with a Pt catalyst, the ethylene selectivity rises from 65 to 72% but ethane conversion drops from 70 to 52%. However, using a Pt-Sn/{alpha}-Al{sub 2}O{sub 3} catalyst, the C{sub 2}H{sub 4} selectivity increases from 70 to greater than 85%, while the conversion remains {approximately}70%. The process also produces approximately as much H{sub 2} as is added to the feed. Effects of other metal promoters, sphere bed and fibermat supports, preheat, pressure, nitrogen dilution, and flow rate are examined in an effort to further elucidate the mechanism. Deactivation of the Pt-Sn catalyst is examined, and a simple method of regenerating the activity on-line is demonstrated. Possible mechanisms to explain high selectivities to ethylene are discussed. Although the process can be regarded as a simple two-step reaction sequence with the exothermic oxidation of hydrogen or ethane driving the endothermic dehydrogenation of ethane to ethylene, the exact contributions of heterogeneous or gas-phase reactions and their spatial variations within the catalyst are yet to be determined.

  7. Phosphate-modified carbon nanotubes in the oxidative dehydrogenation of isopentanes.

    PubMed

    Huang, Rui; Liu, Hong Yang; Zhang, Bing Sen; Sun, Xiao Yan; Liang, Chang Hai; Su, Dang Sheng; Zong, Bao Ning; Rong, Jun Feng

    2014-12-01

    Ketonic/quinonic C=O groups on the surface of a carbon matrix are capable of abstracting hydrogen in C=H bonds from hydrocarbons and enable them to selectively convert into corresponding unsaturated hydrocarbons; this process is the oxidative dehydrogenation (ODH) reaction. However, a variety of inevitable defects or graphene edges and other oxygen-containing groups on the carbon matrix are detrimental to the selective production of alkenes due to their high activity towards overoxidation. Herein, we show that phosphate can not only impede the total oxidation but also cover the selective C=O groups, hence allowing its use as a modulator to defects and oxygen-containing functional groups on the multiwalled carbon nanotubes, regulating the distribution of active sites and related catalytic targets. PMID:25213438

  8. Synthesis of C60-Fused Tetrahydrocarbazole/Dibenzothiophene/Benzothiophene and Dibenzofuran Derivatives via Metal-Free Oxidative Dehydrogenative Carboannulation.

    PubMed

    Liu, Tong-Xin; Ma, Jinliang; Chao, Di; Zhang, Pengling; Ma, Nana; Liu, Qingfeng; Shi, Lei; Zhang, Zhiguo; Zhang, Guisheng

    2016-08-19

    A transition-metal-free oxidative dehydrogenative coupling reaction has been developed for the direct construction of novel C60-fused tetrahydrocarbazoles, dibenzothiophenes, benzothiophenes, and dibenzofurans. This new carboannulation reaction features high atom economy, operational simplicity, broad substrate scope, and excellent functional-group tolerance and provides a convenient access to a scarce class of fullerene derivatives. PMID:27487008

  9. Copper-catalyzed intermolecular dehydrogenative amidation/amination of quinoline N-oxides with lactams/cyclamines.

    PubMed

    Li, Gang; Jia, Chunqi; Sun, Kai

    2013-10-18

    C-H, N-H dehydrogenative coupling of quinoline N-oxides with lactams/cyclamines has been achieved in the presence of the Cu(OAc)2 catalyst to give good to excellent yields. This study provides a new strategy for the construction of a 2-aminoquinoline skeleton via direct functionalization of aryl C-H bonds. PMID:24093556

  10. Copper-catalyzed oxidative dehydrogenative carboxylation of unactivated alkanes to allylic esters via alkenes.

    PubMed

    Tran, Ba L; Driess, Matthias; Hartwig, John F

    2014-12-10

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV-vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C-H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C-H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper-carboxylate, copper-amidate, and copper-imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)-amidate > Cu(II)-imidate > Cu(II)-benzoate. Consistent with this trend, Cu(II)-amidates and Cu(II)-benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  11. Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

    PubMed Central

    2015-01-01

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate. Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  12. Oxidative Dehydrogenation on Nanocarbon: Intrinsic Catalytic Activity and Structure-Function Relationships.

    PubMed

    Qi, Wei; Liu, Wei; Guo, Xiaoling; Schlögl, Robert; Su, Dangsheng

    2015-11-01

    Physical and chemical insights into the nature and quantity of the active sites and the intrinsic catalytic activity of nanocarbon materials in alkane oxidative dehydrogenation (ODH) reactions are reported using a novel in situ chemical titration process. A study on the structure-function relationship reveals that the active sites are identical both in nature and function on various nanocarbon catalysts. Additionally, the quantity of the active sites could be used as a metric to normalize the reaction rates, and thus to evaluate the intrinsic activity of nanocarbon catalysts. The morphology of the nanocarbon catalysts at the microscopic scale exhibits a minor influence on their intrinsic ODH catalytic activity. The number of active sites calculated from the titration process indicates the number of catalytic centers that are active (that is, working) under the reaction conditions. PMID:26388451

  13. Gas-phase oxidation of propane in the presence of azaporphin compounds

    SciTech Connect

    Enikobpov, N.S.; Moshkina, R.I.; Nikisha, L.V.; Polyak, S.S.; Promyslova, V.V.

    1985-07-01

    The gas-phase oxidation of an equimolar mixture of propane with oxygen was studied in the presence of various polyphthalocyanins: metal-free PPC and mono- and bimetallic complexes PPC-Fe, PPC-Co, PPC-Cu-Fe, and PPC-Mg-Fe. The inhibition of oxidation increases in the series: PPC-Co < PPC-Fe approx. = PPC-Mg-Fe < PPC < PPC-Cu-Fe. The qualitative and quantitative composition of the products is virtually unchanged in comparison with the untreated reactor.

  14. Electrochemical promotion of propane oxidation on Pt deposited on a dense β"-Al2O3 ceramic Ag+ conductor

    NASA Astrophysics Data System (ADS)

    Tsampas, Michail; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini; Vernoux, Philippe

    2013-08-01

    A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β"-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation.

  15. The role of molecular oxygen in the iron(III)-promoted oxidative dehydrogenation of amines.

    PubMed

    Saucedo-Vázquez, Juan Pablo; Kroneck, Peter M H; Sosa-Torres, Martha Elena

    2015-03-28

    A mechanistic study is presented of the oxidative dehydrogenation of the iron(III) complex [Fe(III)L(3)](3+), 1, (L(3) = 1,9-bis(2'-pyridyl)-5-[(ethoxy-2''-pyridyl)methyl]-2,5,8-triazanonane) in ethanol in the presence of molecular oxygen. The product of the reaction was identified by NMR spectroscopy and X-ray crystallography as the identical monoimine complex [Fe(II)L(4)](2+), 2, (L(4) = 1,9-bis(2'-pyridyl)-5-[(ethoxy-2''-pyridyl)methyl]-2,5,8-triazanon-1-ene) also formed under an inert nitrogen atmosphere. Molecular oxygen is an active player in the oxidative dehydrogenation of iron(III) complex 1. Reduced oxygen species, e.g., superoxide, (O2˙(-)) and peroxide (O2(2-)), are formed and undergo single electron transfer reactions with ligand-based radical intermediates. The experimental rate law can be described by the third order rate equation, -d[(Fe(III)L(3))(3+)]/dt = kOD[(Fe(III)L(3))(3+)][EtO(-)][O2], with kOD = 3.80 ± 0.09 × 10(7) M(-2) s(-1) (60 °C, μ = 0.01 M). The reduction O2 → O2˙(-) represents the rate determining step, with superoxide becoming further reduced to peroxide as shown by a coupled heme catalase assay. In an independent study, with H2O2, replacing O2 as the oxidant, the experimental rate law depended on [H2O2]: -d[(Fe(III)L(3))(3+)]/dt = kH2O2[(Fe(III)L(3))(3+)][H2O2]), with kH2O2 = 6.25 ± 0.02 × 10(-3) M(-1) s(-1). In contrast to the reaction performed under N2, no kinetic isotope effect (KIE) or general base catalysis was found for the reaction of iron(III) complex 1 with O2. Under N2, two consecutive one-electron oxidation steps of the ligand coupled to proton removal produced the iron(II)-monoimine complex [Fe(II)L(4)](2+) and the iron(II)-amine complex [Fe(II)L(3)](2+) in a 1 : 1 ratio (disproportionation), with the amine deprotonation being the rate determining step. Notably, the reaction is almost one order of magnitude faster in the presence of O2, with kEtO(-) = 3.02 ± 0.09 × 10(5) M(-1) s(-1) (O2) compared to k

  16. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    NASA Astrophysics Data System (ADS)

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-10-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

  17. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    PubMed Central

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-01-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

  18. Iodine-Catalyzed Cross Dehydrogenative Coupling Reaction: A Regioselective Sulfenylation of Imidazoheterocycles Using Dimethyl Sulfoxide as an Oxidant.

    PubMed

    Siddaraju, Yogesh; Prabhu, Kandikere Ramaiah

    2016-09-01

    A regioselective formation of C-S bonds has been achieved using a cross dehydrogenative coupling (CDC) protocol using iodine as a catalyst and dimethyl sulfoxide as an oxidant under green chemistry conditions. This strategy employs the reaction of easily available heterocyclic thiols or thiones with imidazoheterocycles. This protocol provides an efficient, mild, and inexpensive method for sulfenylation of imidazoheterocycles with a diverse range of heterocyclic thiols and heterocyclic thiones. PMID:27490357

  19. Oxidative dehydrogenation of isobutane over vanadia catalysts supported by titania nanoshapes

    SciTech Connect

    Kraemer, Shannon K.; Rondinone, Adam Justin; Tsai, Yu-Tung; Schwartz, Viviane; Steven H. Overbury; Idrobo, Juan-Carlos; Wu, Zili

    2015-11-02

    Support plays a complex role in catalysis by supported metal oxides and the exact support effect still remains elusive. One of the approaches to gain fundamental insights into the support effect is to utilize model support systems. In this study, we employed for the first time titania nanoshapes as the model supports and investigated how the variation of surface structure of the support (titania, TiO2) impacts the catalysis of supported oxide (vanadia, VOx). TiO2 truncated rhombi, spheres and rods were synthesized via hydrothermal method and characterized with XRD and TEM. These TiO2 nanoshapes represent different mixtures of surface facets including [1 0 1], [0 1 0] and [0 0 1] and were used to support vanadia. The structure of supported VOx species was characterized in detail with in situ Raman spectroscopy as a function of loading on the three TiO2 nanoshapes. Oxidative dehydrogenation (ODH) of isobutane to isobutene was used as a model reaction to test how the support shape influences the activity, selectivity and activation energy of the surface VOx species. It was shown that the shape of TiO2 support does not pose evident effect on either the structure of surface VOx species or the catalytic performance of surface VOx species in isobutane ODH reaction. Finally, this insignificant support shape effect was ascribed to the small difference in the surface oxygen vacancy formation energy among the different TiO2 surfaces and the multi-faceting nature of the TiO2 nanoshapes.

  20. Oxidative dehydrogenation of isobutane over vanadia catalysts supported by titania nanoshapes

    DOE PAGESBeta

    Kraemer, Shannon K.; Rondinone, Adam Justin; Tsai, Yu-Tung; Schwartz, Viviane; Steven H. Overbury; Idrobo, Juan-Carlos; Wu, Zili

    2015-11-02

    Support plays a complex role in catalysis by supported metal oxides and the exact support effect still remains elusive. One of the approaches to gain fundamental insights into the support effect is to utilize model support systems. In this study, we employed for the first time titania nanoshapes as the model supports and investigated how the variation of surface structure of the support (titania, TiO2) impacts the catalysis of supported oxide (vanadia, VOx). TiO2 truncated rhombi, spheres and rods were synthesized via hydrothermal method and characterized with XRD and TEM. These TiO2 nanoshapes represent different mixtures of surface facets includingmore » [1 0 1], [0 1 0] and [0 0 1] and were used to support vanadia. The structure of supported VOx species was characterized in detail with in situ Raman spectroscopy as a function of loading on the three TiO2 nanoshapes. Oxidative dehydrogenation (ODH) of isobutane to isobutene was used as a model reaction to test how the support shape influences the activity, selectivity and activation energy of the surface VOx species. It was shown that the shape of TiO2 support does not pose evident effect on either the structure of surface VOx species or the catalytic performance of surface VOx species in isobutane ODH reaction. Finally, this insignificant support shape effect was ascribed to the small difference in the surface oxygen vacancy formation energy among the different TiO2 surfaces and the multi-faceting nature of the TiO2 nanoshapes.« less

  1. Copper catalyzed oxidative esterification of aldehydes with alkylbenzenes via cross dehydrogenative coupling.

    PubMed

    Rout, Saroj Kumar; Guin, Srimanta; Ghara, Krishna Kanta; Banerjee, Arghya; Patel, Bhisma K

    2012-08-01

    Copper(II) as the catalyst in a cross dehydrogenative coupling (CDC) reaction has been demonstrated for the synthesis of benzylic esters using aldehydes and alkylbenzenes as coupling partners. PMID:22817825

  2. Palladium-Catalyzed Aerobic Oxidative Dehydrogenation of Cyclohexenes to Substituted Arene Derivatives

    PubMed Central

    Iosub, Andrei V.; Stahl, Shannon S.

    2015-01-01

    A palladium(II) catalyst system has been identified for aerobic dehydrogenation of substituted cyclohexenes to the corresponding arene derivatives. Use of sodium anthraquinone-2-sulfonate (AMS) as a co-catalyst enhances the product yields. A wide range of functional groups are tolerated in the reactions, and the scope and limitations of the method are described. The catalytic dehydrogenation of cyclohexenes is showcased in an efficient route to a phthalimide-based TRPA1 activity modulator. PMID:25734414

  3. Operating envelope of a short contact time fuel reformer for propane catalytic partial oxidation

    NASA Astrophysics Data System (ADS)

    Waller, Michael G.; Walluk, Mark R.; Trabold, Thomas A.

    2015-01-01

    Fuel cell technology has yet to realize widespread deployment, in part because of the hydrogen fuel infrastructure required for proton exchange membrane systems. One option to overcome this barrier is to produce hydrogen by reforming propane, which has existing widespread infrastructure, is widely used by the general public, easily transported, and has a high energy density. The present work combines thermodynamic modeling of propane catalytic partial oxidation (cPOx) and experimental performance of a Precision Combustion Inc. (PCI) Microlith® reactor with real-time soot measurement. Much of the reforming research using Microlith-based reactors has focused on fuels such as natural gas, JP-8, diesel, and gasoline, but little research on propane reforming with Microlith-based catalysts can be found in literature. The aim of this study was to determine the optimal operating parameters for the reformer that maximizes efficiency and minimizes solid carbon formation. The primary parameters evaluated were reformate composition, carbon concentration in the effluent, and reforming efficiency as a function of catalyst temperature and O2/C ratio. Including the lower heating values for product hydrogen and carbon monoxide, efficiency of 84% was achieved at an O2/C ratio of 0.53 and a catalyst temperature of 940 °C, resulting in near equilibrium performance. Significant solid carbon formation was observed at much lower catalyst temperatures, and carbon concentration in the effluent was determined to have a negative linear relationship at T < 750 °C. The Microlith reactor displayed good stability during more than 80 experiments with temperature cycling from 360 to 1050 °C.

  4. Nature of vanadium sites in V/{alpha}-Ti phosphate catalysts for the oxidative dehydrogenation of ethane

    SciTech Connect

    Santamaria-Gonzalez, J.; Martinez-Lara, M.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Banares, M.S.; Martinez-Huerta, M.V.; Fierro, J.L.G.

    1999-01-25

    The selective conversion of ethane into ethylene is currently being studied because of the economic impact of using natural gas and LPG`s raw materials to produce chemicals and polymers. The available technology for the production of ethylene is the steam cracking of ethane, although it is a highly energy-intensive process. Several approaches to this problem have been considered, although oxidative dehydrogenation (ODH) remains prominent. The principal reason for this lies in the fact that dehydrogenation in the presence of oxygen is thermodynamically favored and coking side reactions are minimized. The present note reports preliminary results in the performance for the ODH reaction of ethane of a new family of vanadium-loaded {alpha}-Ti phosphate catalyst. Moreover, although these catalysts show modest activity with negligible production of CO{sub 2}, a second objective was to report data on the genesis of surface sites during on-stream operation.

  5. Non-Oxidative Dehydrogenation Pathways for the Conversion of C2 -C4 Alcohols to Carbonyl Compounds.

    PubMed

    Shylesh, Sankaranarayanapillai; Kim, Daeyoup; Ho, Christopher R; Johnson, Gregory R; Wu, Jason; Bell, Alexis T

    2015-12-01

    Gold nanoparticles (NPs) supported on hydrotalcite (Au/HT) are highly active and selective catalysts for the continuous, gas-phase, non-oxidative dehydrogenation of bioderived C2 -C4 alcohols. A sharp increase in turn over frequency (TOF) is noted when the size of Au NPs is less than 5 nm relating to the strong synergy between metallic Au NPs and the acid-base groups on the support surface. It is shown that catalytic activity depends critically on Au NP size, support composition, and support pretreatments. A reaction pathway elucidated from kinetic isotope effects suggests that the abstraction of β-H by Au NPs (C-H activation) is the rate-determining step in the dehydrogenation of bioderived C2 -C4 alcohols. PMID:26493770

  6. Main-group compounds selectively oxidize mixtures of methane, ethane, and propane to alcohol esters.

    PubMed

    Hashiguchi, Brian G; Konnick, Michael M; Bischof, Steven M; Gustafson, Samantha J; Devarajan, Deepa; Gunsalus, Niles; Ess, Daniel H; Periana, Roy A

    2014-03-14

    Much of the recent research on homogeneous alkane oxidation has focused on the use of transition metal catalysts. Here, we report that the electrophilic main-group cations thallium(III) and lead(IV) stoichiometrically oxidize methane, ethane, and propane, separately or as a one-pot mixture, to corresponding alcohol esters in trifluoroacetic acid solvent. Esters of methanol, ethanol, ethylene glycol, isopropanol, and propylene glycol are obtained with greater than 95% selectivity in concentrations up to 1.48 molar within 3 hours at 180°C. Experiment and theory support a mechanism involving electrophilic carbon-hydrogen bond activation to generate metal alkyl intermediates. We posit that the comparatively high reactivity of these d(10) main-group cations relative to transition metals stems from facile alkane coordination at vacant sites, enabled by the overall lability of the ligand sphere and the absence of ligand field stabilization energies in systems with filled d-orbitals. PMID:24626925

  7. Effect of size of catalytically active phases in the dehydrogenation of alcohols and the challenging selective oxidation of hydrocarbons.

    PubMed

    Zhang, Qinghong; Deng, Weiping; Wang, Ye

    2011-09-01

    The size of the active phase is one of the most important factors in determining the catalytic behaviour of a heterogeneous catalyst. This Feature Article focuses on the size effects in two types of reactions, i.e., the metal nanoparticle-catalysed dehydrogenation of alcohols and the metal oxide nanocluster-catalysed selective oxidation of hydrocarbons (including the selective oxidation of methane and ethane and the epoxidation of propylene). For Pd or Au nanoparticle-catalysed oxidative or non-oxidative dehydrogenation of alcohols, the size of metal nanoparticles mainly controls the catalytic activity by affecting the activation of reactants (either alcohol or O(2)). The size of oxidic molybdenum species loaded on SBA-15 determines not only the activity but also the selectivity of oxygenates in the selective oxidation of ethane; highly dispersed molybdenum species are suitable for acetaldehyde formation, while molybdenum oxide nanoparticles exhibit higher formaldehyde selectivity. Cu(II) and Fe(III) isolated on mesoporous silica are highly efficient for the selective oxidation of methane to formaldehyde, while the corresponding oxide clusters mainly catalyse the complete oxidation of methane. The lattice oxygen in iron or copper oxide clusters is responsible for the complete oxidation, while the isolated Cu(I) or Fe(II) generated during the reaction can activate molecular oxygen forming active oxygen species for the selective oxidation of methane. Highly dispersed Cu(I) and Fe(II) species also function for the epoxidation of propylene by O(2) and N(2)O, respectively. Alkali metal ions work as promoters for the epoxidation of propylene by enhancing the dispersion of copper or iron species and weakening the acidity. PMID:21629889

  8. Identification of Methane, Ethane, and Propane Oxidizing Bacteria at Marine Hydrocarbon Seeps by Stable Isotope Probing

    NASA Astrophysics Data System (ADS)

    Redmond, M.; Ding, H.; Friedrich, M. W.; Valentine, D. L.

    2008-12-01

    Hydrocarbon seeps emit substantial amounts of oil and natural gas into the marine environment, where they can be oxidized by microorganisms in the sediment and water column. Here, we used stable isotope probing of DNA and lipid biomarkers to identify the microorganisms actively consuming 13C-labeled natural gas compounds in seep sediment samples. Surface sediment was collected from the Coal Oil Point seep field (offshore Santa Barbara, California, USA) and incubated under aerobic conditions with 13C labeled methane, ethane, or propane for up to 37 days, with sediment sub-samples taken at 3-4 intermediate time points. DNA was extracted from sediment and separated by CsCl density gradient centrifugation. The microbial community in each fraction was profiled using T-RFLP, and bacterial 16S rRNA gene clone libraries were constructed from un-incubated hydrocarbon seep sediment and selected isotopically 'heavy' (13C) and 'light' (12C) gradient fractions from ethane incubations. All clone libraries were dominated by sequences from members of the family Rhodobacteraceae (>25% of sequences) and a diverse group of Gammaproteobacteria, including sequences related to those of methylotrophs and to those of bacteria known to consume the longer-chain alkanes present in crude oil. After 14 days of incubation, the relative abundance of Rhodobacteraceae was higher in 'heavy' fractions from the 13C-ethane incubation than in 'light' fractions, suggesting incorporation of 13C label. The Rhodobacteraceae are very diverse metabolically, but have often been observed in abundance in oil contaminated seawater. Several members of this group have been shown to oxidize longer chain alkanes (C10 or higher), but none have been previously linked to the consumption of the gaseous alkanes ethane, propane, and butane. For the final time point, 13C content of phospholipid fatty acids (PLFA) were also analyzed, showing substantial incorporation of 13C over 37 days. In the methane incubation

  9. Significance of β-dehydrogenation in ethanol electro-oxidation on platinum doped with Ru, Rh, Pd, Os and Ir.

    PubMed

    Sheng, Tian; Lin, Wen-Feng; Hardacre, Christopher; Hu, P

    2014-07-14

    In the exploration of highly efficient direct ethanol fuel cells (DEFCs), how to promote the CO2 selectivity is a key issue which remains to be solved. Some advances have been made, for example, using bimetallic electrocatalysts, Rh has been found to be an efficient additive to platinum to obtain high CO2 selectivity experimentally. In this work, the mechanism of ethanol electrooxidation is investigated using the first principles method. It is found that CH3CHOH* is the key intermediate during ethanol electrooxidation and the activity of β-dehydrogenation is the rate determining factor that affects the completeness of ethanol oxidation. In addition, a series of transition metals (Ru, Rh, Pd, Os and Ir) are alloyed on the top layer of Pt(111) in order to analyze their effects. The elementary steps, α-, β-C-H bond and C-C bond dissociations, are calculated on these bimetallic M/Pt(111) surfaces and the formation potential of OH* from water dissociation is also calculated. We find that the active metals increase the activity of β-dehydrogenation but lower the OH* formation potential resulting in the active site being blocked. By considering both β-dehydrogenation and OH* formation, Ru, Os and Ir are identified to be unsuitable for the promotion of CO2 selectivity and only Rh is able to increase the selectivity of CO2 in DEFCs. PMID:24869778

  10. Oxidative dehydrogenation of cyclohexene on size selected subnanometer cobalt clusters: improved catalytic performance via evolution of cluster-assembled nanostructures.

    PubMed

    Lee, Sungsik; Di Vece, Marcel; Lee, Byeongdu; Seifert, Sönke; Winans, Randall E; Vajda, Stefan

    2012-07-14

    The catalytic activity of oxide-supported metal nanoclusters strongly depends on their size and support. In this study, the origin of morphology transformation and chemical state changes during the oxidative dehydrogenation of cyclohexene was investigated in terms of metal-support interactions. Model catalyst systems were prepared by deposition of size selected subnanometer Co(27±4) clusters on various metal oxide supports (Al(2)O(3), ZnO and TiO(2) and MgO). The oxidation state and reactivity of the supported cobalt clusters were investigated by temperature programmed reaction (TPRx) and in situ grazing incidence X-ray absorption (GIXAS) during oxidative dehydrogenation of cyclohexene, while the sintering resistance monitored with grazing incidence small angle X-ray scattering (GISAXS). The activity and selectivity of cobalt clusters shows strong dependence on the support. GIXAS reveals that metal-support interaction plays a key role in the reaction. The most pronounced support effect is observed for MgO, where during the course of the reaction in its activity, composition and size dynamically evolving nanoassembly is formed from subnanometer cobalt clusters. PMID:22419008

  11. Acceptorless Dehydrogenative Oxidation of Secondary Alcohols Catalysed by Cp*Ir(III) -NHC Complexes.

    PubMed

    Gülcemal, Süleyman; Gülcemal, Derya; Whitehead, George F S; Xiao, Jianliang

    2016-07-18

    A series of new Ir(III) complexes with carbene ligands that contain a range of benzyl wingtip groups have been prepared and fully characterised by NMR spectroscopy, HRMS, elemental analysis and X-ray diffraction. All the complexes were active in the acceptorless dehydrogenation of alcohol substrates in 2,2,2-trifluoroethanol to give the corresponding carbonyl compounds. The most active complex bore an electron-rich carbene ligand; this complex was used to catalyse the highly efficient and chemoselective dehydrogenation of a wide range of secondary alcohols to their respective ketones, with turnover numbers up to 1660. Mechanistic studies suggested that the turnover of the dehydrogenation reaction is limited by the H2 -formation step. PMID:27321021

  12. Regiodivergent Cross-Dehydrogenative Coupling of Pyridines and Benzoxazoles: Discovery of Organic Halides as Regio-Switching Oxidants.

    PubMed

    Yamada, Shuya; Murakami, Kei; Itami, Kenichiro

    2016-05-20

    Cross-dehydrogenative coupling (CDC) of two unfunctionalized heteroarenes has been recognized as an ideal transformation to synthesize privileged heterobiaryl scaffolds. However, regioselective activation and transformation of a specific set of two heterocyclic C-H bonds among other bonds have been extremely challenging. Thus, discovering a new controlling element to achieve regio-controlled and regio-divergent heterocyclic CDCs is considered crucial. In this Letter, the unprecedented use of organic halides as an oxidant to achieve the CDC reaction of pyridines and benzoxazoles with palladium catalyst is described. Moreover, the regioselectivity of the pyridine functionalization site can be controlled by the choice of organic halides. PMID:27162109

  13. Methanol Oxidative Dehydrogenation on Oxide Catalysts: Molecular and Dissociative Routes and Hydrogen Addition Energies as Descriptors of Reactivity

    SciTech Connect

    Deshlahra, Prashant; Iglesia, Enrique

    2014-11-13

    The oxidative dehydrogenation (ODH) of alkanols on oxide catalysts is generally described as involving H-abstraction from alkoxy species formed via O–H dissociation. Kinetic and isotopic data cannot discern between such routes and those involving kinetically-relevant H-abstraction from undissociated alkanols. Here, we combine such experiments with theoretical estimates of activation energies and entropies to show that the latter molecular routes prevail over dissociative routes for methanol reactions on polyoxometalate (POM) clusters at all practical reaction temperatures. The stability of the late transition states that mediate H-abstraction depend predominantly on the stability of the O–H bond formed, making H-addition energies (HAE) accurate and single-valued descriptors of reactivity. Density functional theory-derived activation energies depend linearly on HAE values at each O-atom location on clusters with a range of composition (H3PMo12, H4SiMo12, H3PW12, H4PV1Mo11, and H4PV1W11); both barriers and HAE values reflect the lowest unoccupied molecular orbital energy of metal centers that accept the electron and the protonation energy of O-atoms that accept the proton involved in the H-atom transfer. Bridging O-atoms form O–H bonds that are stronger than those of terminal atoms and therefore exhibit more negative HAE values and higher ODH reactivity on all POM clusters. For each cluster composition, ODH turnover rates reflect the reactivity-averaged HAE of all accessible O-atoms, which can be evaluated for each cluster composition to provide a rigorous and accurate predictor of ODH reactivity for catalysts with known structure. These relations together with oxidation reactivity measurements can then be used to estimate HAE values and to infer plausible structures for catalysts with uncertain active site structures.

  14. Surface-inspired molecular vanadium oxide catalysts for the oxidative dehydrogenation of alcohols: evidence for metal cooperation and peroxide intermediates.

    PubMed

    Werncke, C Gunnar; Limberg, Christian; Knispel, Christina; Mebs, Stefan

    2011-10-17

    On the basis that thiacalix[4]arene (H(4)T4A) complex (PPh(4) )(2) [H(2)T4A(VO(2))](2) (Ia) was found to be an adequate functional model for surface species occurring on vanadium oxide based catalysts and itself catalyses the oxidative dehydrogenation (ODH) of alcohols, an analogue containing 2,2'-thiobis(2,4-di-tert-butylphenolate), (S)L(2-), as ligand, namely, (PPh(4))(2)[(S)LVO(2)](2) (II) was investigated in the same context. Despite the apparent similarity of Ia and II, studies on II revealed several novel insights, which are also valuable in connection with surfaces of vanadia catalysts: 1) For Ia and II similar turnover numbers (TONs) were found for the ODH of activated alcohols, which indicates that the additional OH units inherent to Ia do not contribute particularly to the activity of this complex, for instance, through prebinding of the alcohol. 2) On dissolution II enters into an equilibrium with a monomeric form, which is the predominant species in solution; nevertheless, ODH proceeds exclusively at the dimeric form, and this stresses the need for cooperation of two vanadium centres. 3) By omitting O(2) from the system during the oxidation of 9-fluorenol, the reduced form of the catalyst could be isolated and fully characterised (including single-crystal X-ray analysis). The corresponding intermediate had been elusive in case of thiacalixarene system Ia. 4) Reoxidation was found to proceed via a peroxide intermediate that also oxidises one alcohol equivalent. As the peroxide can also perform mono- and dioxygenation of the thioether group in II, after a number of turnovers the active catalyst contains a sulfone group. The reduced form of this ultimate catalyst was also isolated and structurally characterised. Possible implications of 1)-4) for the function of heterogeneous vanadia catalysts are discussed. PMID:21915928

  15. Potassium promotion of iron oxide dehydrogenation catalysts supported on magnesium oxide: 1. Preparation and characterization

    SciTech Connect

    Stobbe, D.E.; Buren, F.R. van ); Dillen, A.J. van; Geus, J.W. )

    1992-06-01

    Catalysts of iron oxide supported on magnesium oxide and promoted with potassium were prepared by incipient wetness impregnation of preshaped magnesium oxide support pellets with a solution of an iron complex, either ammonium iron (III) citrate or ammonium iron (III) EDTA and potassium carbonate. Iron and potassium were applied wither simultaneously or consecutively. As determined using X-ray diffraction, thermogravimetric analysis, and magnetic measurements, calcination above 923 K results in the formation of a mixed oxide of iron and potassium, viz., KFeO[sub 2]. After calcination at 973 K the average crystallite size of the KFeO[sub 2] phase is about 300 [angstrom]. The formation of KFeO[sub 2] appeared to have a strong retarding effect on the reduction of the iron oxide phase to metallic iron. It was found that the KFeO[sub 2] phase is unstable in atomspheric air due to reaction with carbon dioxide and moisture to form potassium (hydrogen) carbonate and (hydrated) iron oxide.

  16. Formation of M2+(O2)(C3H8) species in alkaline-earth-exchanged Y zeolite during propane selective oxidation.

    PubMed

    Xu, Jiang; Mojet, Barbara L; van Ommen, Jan G; Lefferts, Leon

    2005-10-01

    The adsorption of oxygen and d2-propane (CH3CD2CH3) on a series of alkaline-earth-exchanged Y zeolite at room temperature was studied with in situ infrared spectroscopy. Surprisingly at room temperature, oxygen adsorption led to the formation of supercage M2+(O2) species. Further, at low propane coverage, propane was found to adsorb linearly on Mg2+ cations, but a ring-adsorption structure was observed for propane adsorbing on Ca2+, Sr2+, and Ba2+ cations. It is demonstrated that O2 and propane can simultaneously attach to one active center (M2+) to form a M2+(O2)(C3H8) species, which is proposed to be the precursor in thermal propane selective oxidation. Selectivity to acetone in the propane oxidation reaction decreases with increasing temperature and cation size due to the formation of 2-propanol and carboxylate ions. An extended reaction scheme for the selective oxidation of propane over alkaline earth exchanged Y zeolites is proposed. PMID:16853364

  17. Multiscale Informatics for Low-Temperature Propane Oxidation: Further Complexities in Studies of Complex Reactions.

    PubMed

    Burke, Michael P; Goldsmith, C Franklin; Klippenstein, Stephen J; Welz, Oliver; Huang, Haifeng; Antonov, Ivan O; Savee, John D; Osborn, David L; Zádor, Judit; Taatjes, Craig A; Sheps, Leonid

    2015-07-16

    The present paper describes further development of the multiscale informatics approach to kinetic model formulation of Burke et al. (Burke, M. P.; Klippenstein, S. J.; Harding, L. B. Proc. Combust. Inst. 2013, 34, 547-555) that directly incorporates elementary kinetic theories as a means to provide reliable, physics-based extrapolation of kinetic models to unexplored conditions. Here, we extend and generalize the multiscale informatics strategy to treat systems of considerable complexity-involving multiwell reactions, potentially missing reactions, nonstatistical product branching ratios, and non-Boltzmann (i.e., nonthermal) reactant distributions. The methodology is demonstrated here for a subsystem of low-temperature propane oxidation, as a representative system for low-temperature fuel oxidation. A multiscale model is assembled and informed by a wide variety of targets that include ab initio calculations of molecular properties, rate constant measurements of isolated reactions, and complex systems measurements. Active model parameters are chosen to accommodate both "parametric" and "structural" uncertainties. Theoretical parameters (e.g., barrier heights) are included as active model parameters to account for parametric uncertainties in the theoretical treatment; experimental parameters (e.g., initial temperatures) are included to account for parametric uncertainties in the physical models of the experiments. RMG software is used to assess potential structural uncertainties due to missing reactions. Additionally, branching ratios among product channels are included as active model parameters to account for structural uncertainties related to difficulties in modeling sequences of multiple chemically activated steps. The approach is demonstrated here for interpreting time-resolved measurements of OH, HO2, n-propyl, i-propyl, propene, oxetane, and methyloxirane from photolysis-initiated low-temperature oxidation of propane at pressures from 4 to 60 Torr and

  18. Silylesterification of oxidized multi-wall carbon nanotubes by catalyzed dehydrogenative cross-coupling between carboxylic and hydrosilane functions

    NASA Astrophysics Data System (ADS)

    Seffer, J.-F.; Detriche, S.; Nagy, J. B.; Delhalle, J.; Mekhalif, Z.

    2014-06-01

    Surface modification of oxidized carbon nanotubes (O-CNTs) with silicon based anchoring groups (R-SiR3) is a relatively uncommon approach of the CNTs functionalization. Hydrosilane derivatives constitute an attractive subclass of compounds for silanization reactions on the CNTs surface. In this work, we report on the ZnCl2 catalytically controlled reaction (hydrosilane dehydrogenative cross-coupling, DHCC) of fluorinated hydrosilane probes with the carboxylic functions present on the surface of oxidized multi-wall carbon nanotubes. Carbon nanotubes functionalized with essentially alcohol groups are also used to compare the selectivity of zinc chloride toward carboxylic groups. To assess the efficiency of functionalization, X-ray Photoelectron Spectroscopy is used to determine the qualitative and quantitative composition of the different samples. Solubility tests on the oxidized and silanized MWNTs are also carried out in the framework of the Hansen Solubility Parameters (HSP) theory to apprehend at another scale the effect of DHCC.

  19. Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles for C1 to C3 Alcohol Oxidation and Dehydrogenation of Dimethylamine-borane (DMAB).

    PubMed

    Erken, Esma; Yildiz, Yunus; Kilbaş, Benan; Sen, Fatih

    2016-06-01

    Highly efficient nearly monodisperse Pt NPs catalyze C1 to C3 alcohol oxidation with very high electrochemical activities and provides one of the highest catalytic activities (TOF = 21.50 h(-1)) in the dehydrogenation of DMAB at room temperature. The exceptional stability towards agglomeration, leaching and CO poisoning for the prepared catalyst allow these particles to be recycled and reused in the catalysis of both DMAB dehydrogenation and C1 to C3 alcohol oxidation. After four subsequent reaction and recovery cycles, catalyst retained ≥ 80% activity towards the complete dehydrogenation of DMAB. The prepared catalyst structures were determined by the X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) respectively. PMID:27427655

  20. Propane Basics

    SciTech Connect

    NREL

    2010-03-01

    Propane powers about 190,000 vehicles in the U.S. and more than 14 million worldwide. Propane vehicles are a good choice for many fleet applications including school buses, shuttle buses, taxies and light-duty trucks.

  1. Phase transformations of the FePO4 catalyst in the oxidative dehydrogenation to form an alkyl methacrylate

    NASA Astrophysics Data System (ADS)

    Khan, F. B.; Bharuth-Ram, K.; Friedrich, H. B.

    2010-04-01

    A phase specific iron orthophosphate catalyst, FePO4, was synthesized and subjected to oxidative dehydrogenation reactions to form an alkyl methacrylate. The phases of the catalyst, before and after the reactions, were characterized by Mössbauer spectroscopy. The Mössbauer spectra show the change of the catalyst precursor FePO4, tridymite-like phase (tdm), to the reduced form, iron(II) pyrophosphate, Fe2P2O7, and thereafter the phase change is governed by the temperatures of oxidation. X-ray diffraction and Mössbauer measurements on the spent catalyst, after using organic and water co-feeds, show a transformation of the catalyst to a mixture of phases which are condition specific.

  2. Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

    PubMed Central

    Gómez-Pozos, Heberto; González-Vidal, José Luis; Torres, Gonzalo Alberto; Rodríguez-Baez, Jorge; Maldonado, Arturo; de la Luz Olvera, María; Acosta, Dwight Roberto; Avendaño-Alejo, Maximino; Castañeda, Luis

    2013-01-01

    Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C3H8) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well. PMID:23482091

  3. A rapid compression machine study of the oxidation of propane in the negative temperature coefficient regime

    SciTech Connect

    Gallagher, S.M.; Curran, H.J.; Metcalfe, W.K.; Healy, D.; Simmie, J.M.; Bourque, G.

    2008-04-15

    The oxidation of propane has been studied in the temperature range 680-970 K at compressed gas pressures of 21, 27, and 37 atm and at varying equivalence ratios of 0.5, 1.0, and 2.0. These data are consistent with other experiments presented in the literature for alkane fuels in that, when ignition delay times are plotted as a function of temperature, a characteristic negative coefficient behavior is observed. In addition, these data were simulated using a detailed chemical kinetic model. It was found that qualitatively the model correctly simulated the effect of change in equivalence ratio and pressure, predicting that fuel-rich, high-pressure mixtures ignite fastest, while fuel-lean, low-pressure mixtures ignite slowest. Moreover, reactivity as a function of temperature is well captured, with the model predicting negative temperature coefficient behavior similar to the experiments. Quantitatively the model is faster than experiment for all mixtures at the lowest temperatures (650-750 K) and is also faster than experiment throughout the entire temperature range for fuel-lean mixtures. (author)

  4. Chromium and ruthenium-doped zinc oxide thin films for propane sensing applications.

    PubMed

    Gómez-Pozos, Heberto; González-Vidal, José Luis; Torres, Gonzalo Alberto; Rodríguez-Baez, Jorge; Maldonado, Arturo; Olvera, María de la Luz; Acosta, Dwight Roberto; Avendaño-Alejo, Maximino; Castañeda, Luis

    2013-01-01

    Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C3H8) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well. PMID:23482091

  5. Propane Update.

    ERIC Educational Resources Information Center

    Brantner, Max

    1984-01-01

    Reports on a northern Illinois school bus fleet converted to propane fuel in 1981 and 1982. Includes tables showing, first, total annual fuel costs before and after conversion and, second, fuel efficiency for 16 buses using propane and three using gasoline. Notes precautions for propane use. (MCG)

  6. A versatile approach to flavones via a one-pot Pd(II)-catalyzed dehydrogenation/oxidative boron-Heck coupling sequence of chromanones.

    PubMed

    Lee, Jun; Yu, Jihyun; Son, Seung Hwan; Heo, Jinyuk; Kim, Taelim; An, Ji-Young; Inn, Kyung-Soo; Kim, Nam-Jung

    2016-01-14

    A variety of flavones were expediently synthesized from readily accessible chromanones via a one-pot sequence involving Pd(II)-catalyzed dehydrogenation and oxidative boron-Heck coupling with arylboronic acid pinacol esters. In particular, the use of arylboronic acid pinacol esters was found to significantly improve the yield of the reaction. PMID:26592753

  7. New insights into low-temperature oxidation of propane from synchrotron photoionization mass spectrometry and multi-scale informatics modeling

    DOE PAGESBeta

    Welz, Oliver; Burke, Michael P.; Antonov, Ivan O.; Goldsmith, C. Franklin; Savee, John David; Osborn, David L.; Taatjes, Craig A.; Klippenstein, Stephen J.; Sheps, Leonid

    2015-04-10

    We studied low-temperature propane oxidation at P = 4 Torr and T = 530, 600, and 670 K by time-resolved multiplexed photoionization mass spectrometry (MPIMS), which probes the reactants, intermediates, and products with isomeric selectivity using tunable synchrotron vacuum UV ionizing radiation. The oxidation is initiated by pulsed laser photolysis of oxalyl chloride, (COCl)2, at 248 nm, which rapidly generates a ~1:1 mixture of 1-propyl (n-propyl) and 2-propyl (i-propyl) radicals via the fast Cl + propane reaction. At all three temperatures, the major stable product species is propene, formed in the propyl + O2 reactions by direct HO2 elimination frommore » both n- and i-propyl peroxy radicals. The experimentally derived propene yields relative to the initial concentration of Cl atoms are (20 ± 4)% at 530 K, (55 ± 11)% at 600 K, and (86 ± 17)% at 670 K at a reaction time of 20 ms. The lower yield of propene at low temperature reflects substantial formation of propyl peroxy radicals, which do not completely decompose on the experimental time scale. In addition, C3H6O isomers methyloxirane, oxetane, acetone, and propanal are detected as minor products. Our measured yields of oxetane and methyloxirane, which are coproducts of OH radicals, suggest a revision of the OH formation pathways in models of low-temperature propane oxidation. The experimental results are modeled and interpreted using a multiscale informatics approach, presented in detail in a separate publication (Burke, M. P.; Goldsmith, C. F.; Klippenstein, S. J.; Welz, O.; Huang H.; Antonov I. O.; Savee J. D.; Osborn D. L.; Zádor, J.; Taatjes, C. A.; Sheps, L. Multiscale Informatics for Low-Temperature Propane Oxidation: Further Complexities in Studies of Complex Reactions. J. Phys. Chem A. 2015, DOI: 10.1021/acs.jpca.5b01003). Additionally, we found that the model predicts the time profiles and yields of the experimentally observed primary products well, and shows satisfactory agreement for products

  8. New insights into low-temperature oxidation of propane from synchrotron photoionization mass spectrometry and multi-scale informatics modeling

    SciTech Connect

    Welz, Oliver; Burke, Michael P.; Antonov, Ivan O.; Goldsmith, C. Franklin; Savee, John David; Osborn, David L.; Taatjes, Craig A.; Klippenstein, Stephen J.; Sheps, Leonid

    2015-04-10

    We studied low-temperature propane oxidation at P = 4 Torr and T = 530, 600, and 670 K by time-resolved multiplexed photoionization mass spectrometry (MPIMS), which probes the reactants, intermediates, and products with isomeric selectivity using tunable synchrotron vacuum UV ionizing radiation. The oxidation is initiated by pulsed laser photolysis of oxalyl chloride, (COCl)2, at 248 nm, which rapidly generates a ~1:1 mixture of 1-propyl (n-propyl) and 2-propyl (i-propyl) radicals via the fast Cl + propane reaction. At all three temperatures, the major stable product species is propene, formed in the propyl + O2 reactions by direct HO2 elimination from both n- and i-propyl peroxy radicals. The experimentally derived propene yields relative to the initial concentration of Cl atoms are (20 ± 4)% at 530 K, (55 ± 11)% at 600 K, and (86 ± 17)% at 670 K at a reaction time of 20 ms. The lower yield of propene at low temperature reflects substantial formation of propyl peroxy radicals, which do not completely decompose on the experimental time scale. In addition, C3H6O isomers methyloxirane, oxetane, acetone, and propanal are detected as minor products. Our measured yields of oxetane and methyloxirane, which are coproducts of OH radicals, suggest a revision of the OH formation pathways in models of low-temperature propane oxidation. The experimental results are modeled and interpreted using a multiscale informatics approach, presented in detail in a separate publication (Burke, M. P.; Goldsmith, C. F.; Klippenstein, S. J.; Welz, O.; Huang H.; Antonov I. O.; Savee J. D.; Osborn D. L.; Zádor, J.; Taatjes, C. A.; Sheps, L. Multiscale Informatics for Low-Temperature Propane Oxidation: Further Complexities in Studies of Complex Reactions. J. Phys. Chem A. 2015, DOI: 10.1021/acs.jpca.5b01003). Additionally, we found that the model predicts the time profiles and yields of the experimentally observed primary products well

  9. Electrochemical promotion of propane oxidation on Pt deposited on a dense β″-Al2O3 ceramic Ag+ conductor

    PubMed Central

    Tsampas, Mihalis N.; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini M.; Vernoux, Philippe

    2013-01-01

    A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β″-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that, upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation. PMID:24790942

  10. Propane fear

    SciTech Connect

    Begley, R.

    1992-02-12

    A minor feature of a Congressional energy bill is causing consternation for a number of propane-consuming chemical companies. The firms are fighting the bill`s inclusion of liquefied petroleum gas (LPG) on a list of alternative fuels that can be used to meet its urban fleet vehicles requirements. The firms fear that this added use would drive up the price of propane-an LPG-for homeowners, farmers, and themselves. Speaking for the Propane Consumers Coalition, a Dow Chemical spokesman says 7.7 million households use propane, as does agriculture, and current demand is such that December saw a 23-year low in US inventories. The US depends on imports of propane, he says, and about half the propane sold in the US is derived from the refining of oil, much of which is also imported. Adding demand for vehicle fuel would drive up imports and process, the spokesman says, thereby damaging all users, including the petrochemical industry.

  11. Effect of the conditions of preparing mixed oxide catalyst of Mo-V-Te-Nb-O composition on its activity in the oxidative dehydrogenation of ethane

    NASA Astrophysics Data System (ADS)

    Finashina, E. D.; Kucherov, A. V.; Kustov, L. M.

    2013-12-01

    It is shown that catalytic activity of mixed oxide catalyst of Mo-V-Te-Nb-O composition in oxidative dehydrogenation (OD) of ethane is determined to a substantial degree by the Nb-to-(C2O4)2- ratio in niobium-containing precursors. A pH value of 2.8 to 3.0 for a mixture is optimal when conducting the hydrothermal synthesis of a mixed oxide catalyst; this is achieved by using oxaloniobic acid as a niobium-containing precursor. It is determined that substituting antimony for tellurium results in a loss of catalyst activity during the OD of ethane. The optimum Te content in a catalyst is 0.17 mol %.

  12. Surface Termination of M1 Phase and Rational Design of Propane Ammoxidation Catalysts

    SciTech Connect

    Guliants, Vadim

    2015-02-16

    This final report describes major accomplishments in this research project which has demonstrated that the M1 phase is the only crystalline phase required for propane ammoxidation to acrylonitrile and that a surface monolayer terminating the ab planes of the M1 phase is responsible for their activity and selectivity in this reaction. Fundamental studies of the topmost surface chemistry and mechanism of propane ammoxidation over the Mo-V-(Te,Sb)-(Nb,Ta)-O M1 and M2 phases resulted in the development of quantitative understanding of the surface molecular structure – reactivity relationships for this unique catalytic system. These oxides possess unique catalytic properties among mixed metal oxides, because they selectively catalyze three alkane transformation reactions, namely propane ammoxidation to acrylonitrile, propane oxidation to acrylic acid and ethane oxidative dehydrogenation, all of considerable economic significance. Therefore, the larger goal of this research was to expand this catalysis to other alkanes of commercial interest, and more broadly, demonstrate successful approaches to rational design of improved catalysts that can be applied to other selective (amm)oxidation processes.

  13. Reversible catalytic dehydrogenation of alcohols for energy storage

    PubMed Central

    Bonitatibus, Peter J.; Chakraborty, Sumit; Doherty, Mark D.; Siclovan, Oltea; Jones, William D.; Soloveichik, Grigorii L.

    2015-01-01

    Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis. In this report, reversible acceptorless dehydrogenation of secondary alcohols and diols on iron pincer complexes and reversible oxidative dehydrogenation of primary alcohols/reduction of aldehydes with separate transfer of protons and electrons on iridium complexes are shown. This reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation (dehydrogenation) of hydroxyl-containing fuels. PMID:25588879

  14. 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.

  15. Effects of CeO2 Support Facets on VOx/CeO2 Catalysts in Oxidative Dehydrogenation of Methanol

    SciTech Connect

    Li, Yan; Wei, Zhehao; Gao, Feng; Kovarik, Libor; Peden, Charles HF; Wang, Yong

    2014-05-13

    CeO2 supports with dominating facets, i.e., low index (100), (110) and (111) facets, are prepared. The facet effects on the structure and catalytic performance of supported vanadium oxide catalysts are investigated using oxidative dehydrogenation of methanol as a model reaction. In the presence of mixed facets, Infrared and Raman characterizations demonstrate that surface vanadia species preferentially deposit on CeO2 (100) facets, presumably because of its higher surface energy. At the same surface vanadium densities, VOx species on (100) facets show better dispersion, followed by (110) and (111) facets. The VOx species on CeO2 nanorods with (110) and (100) facets display higher activity and lower apparent activation energies compared to that on CeO2 nanopolyhedras with dominating (111) facets and CeO2 nanocubes with dominating (100) facets. The higher activity for VOx/CeO2(110) might be related to the more abundant oxygen vacancies present on the (110) facets, evidenced from Raman spectroscopic measurements.

  16. Identifying different types of catalysts for CO2 reduction by ethane through dry reforming and oxidative dehydrogenation

    DOE PAGESBeta

    Marc D. Porosoff; Chen, Jingguang G.; Myint, Myat Noe Zin; Kattel, Shyam; Xie, Zhenhua; Gomez, Elaine; Liu, Ping

    2015-11-10

    In this study, the recent shale gas boom combined with the requirement to reduce atmospheric CO2 have created an opportunity for using both raw materials (shale gas and CO2) in a single process. Shale gas is primarily made up of methane, but ethane comprises about 10 % and reserves are underutilized. Two routes have been investigated by combining ethane decomposition with CO2 reduction to produce products of higher value. The first reaction is ethane dry reforming which produces synthesis gas (CO+H2). The second route is oxidative dehydrogenation which produces ethylene using CO2 as a soft oxidant. The results of thismore » study indicate that the Pt/CeO2 catalyst shows promise for the production of synthesis gas, while Mo2C-based materials preserve the C—C bond of ethane to produce ethylene. These findings are supported by density functional theory (DFT) calculations and X-ray absorption near-edge spectroscopy (XANES) characterization of the catalysts under in situ reaction conditions.« less

  17. Identifying different types of catalysts for CO2 reduction by ethane through dry reforming and oxidative dehydrogenation

    SciTech Connect

    Marc D. Porosoff; Chen, Jingguang G.; Myint, Myat Noe Zin; Kattel, Shyam; Xie, Zhenhua; Gomez, Elaine; Liu, Ping

    2015-11-10

    In this study, the recent shale gas boom combined with the requirement to reduce atmospheric CO2 have created an opportunity for using both raw materials (shale gas and CO2) in a single process. Shale gas is primarily made up of methane, but ethane comprises about 10 % and reserves are underutilized. Two routes have been investigated by combining ethane decomposition with CO2 reduction to produce products of higher value. The first reaction is ethane dry reforming which produces synthesis gas (CO+H2). The second route is oxidative dehydrogenation which produces ethylene using CO2 as a soft oxidant. The results of this study indicate that the Pt/CeO2 catalyst shows promise for the production of synthesis gas, while Mo2C-based materials preserve the C—C bond of ethane to produce ethylene. These findings are supported by density functional theory (DFT) calculations and X-ray absorption near-edge spectroscopy (XANES) characterization of the catalysts under in situ reaction conditions.

  18. Identifying Different Types of Catalysts for CO2 Reduction by Ethane through Dry Reforming and Oxidative Dehydrogenation.

    PubMed

    Porosoff, Marc D; Myint, Myat Noe Zin; Kattel, Shyam; Xie, Zhenhua; Gomez, Elaine; Liu, Ping; Chen, Jingguang G

    2015-12-14

    The recent shale gas boom combined with the requirement to reduce atmospheric CO2 have created an opportunity for using both raw materials (shale gas and CO2 ) in a single process. Shale gas is primarily made up of methane, but ethane comprises about 10 % and reserves are underutilized. Two routes have been investigated by combining ethane decomposition with CO2 reduction to produce products of higher value. The first reaction is ethane dry reforming which produces synthesis gas (CO+H2 ). The second route is oxidative dehydrogenation which produces ethylene using CO2 as a soft oxidant. The results of this study indicate that the Pt/CeO2 catalyst shows promise for the production of synthesis gas, while Mo2 C-based materials preserve the CC bond of ethane to produce ethylene. These findings are supported by density functional theory (DFT) calculations and X-ray absorption near-edge spectroscopy (XANES) characterization of the catalysts under in situ reaction conditions. PMID:26554872

  19. An approach to benzophosphole oxides through silver- or manganese-mediated dehydrogenative annulation involving C-C and C-P bond formation.

    PubMed

    Unoh, Yuto; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2013-12-01

    Benzophosphole construction was achieved through the Ag(I) -mediated dehydrogenative annulation of phenylphosphine oxides with internal alkynes in a process involving CC and CP bond formation. A wide range of asymmetrical phenylacetylenes could be employed and the reactions proceeded with perfect regioselectivity. Moreover, the annulation could be conducted even at room temperature when a Mn(III) promoter was used in place of Ag(I) . PMID:24127410

  20. Kinetics of Hydrogen Oxidation Downstream of Lean Propane and Hydrogen Flames

    NASA Technical Reports Server (NTRS)

    Fine, Burton

    1961-01-01

    The decay of hydrogen was measured downstream of lean, flat, premixed hydrogen and propane-air flames seated on cooled porous burners. Experimental variables included temperature, pressure, initial equivalence ratio and diluent. Sampling of burned gas was done through uncooled quartz orifice probes, and the analysis was based on gas chromatography. An approximate treatment of the data in which diffusion was neglected led to the following rate expression for the zone downstream of hydrogen flames d[H (sub 2)] divided by (d times t) equals 1.7 times 10 (sup 10) [H (sub 2)] (sup 3) divided by (sub 2) [O (sub 2)]e (sup (-8100 divided by RT)) moles per liters per second. On the basis of a rate expression of this form, the specific rate constant for the reaction downstream of hydrogen flames was about three times as great as that determined downstream of propane flames. This result was explained on the basis of the existence of a steady state between hydrogen and carbon monoxide in the burned gas downstream of propane flames.

  1. Biodegradation of the gasoline oxygenates methyl tert-butyl ether, ethyl tert-butyl ether, and tert-amyl methyl ether by propane-oxidizing bacteria.

    PubMed Central

    Steffan, R J; McClay, K; Vainberg, S; Condee, C W; Zhang, D

    1997-01-01

    Several propane-oxidizing bacteria were tested for their ability to degrade gasoline oxygenates, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). Both a laboratory strain and natural isolates were able to degrade each compound after growth on propane. When propane-grown strain ENV425 was incubated with 20 mg of uniformly labeled [14C]MTBE per liter, the strain converted > 60% of the added MTBE to 14CO2 in < 30 h. The initial oxidation of MTBE and ETBE resulted in the production of nearly stoichiometric amounts of tert-butyl alcohol (TBA), while the initial oxidation of TAME resulted in the production of tert-amyl alcohol. The methoxy methyl group of MTBE was oxidized to formaldehyde and ultimately to CO2. TBA was further oxidized to 2-methyl-2-hydroxy-1-propanol and then 2-hydroxy isobutyric acid; however, neither of these degradation products was an effective growth substrate for the propane oxidizers. Analysis of cell extracts of ENV425 and experiments with enzyme inhibitors implicated a soluble P-450 enzyme in the oxidation of both MTBE and TBA. MTBE was oxidized to TBA by camphor-grown Pseudomonas putida CAM, which produces the well-characterized P-450cam, but not by Rhodococcus rhodochrous 116, which produces two P-450 enzymes. Rates of MTBE degradation by propane-oxidizing strains ranged from 3.9 to 9.2 nmol/min/mg of cell protein at 28 degrees C, whereas TBA was oxidized at a rate of only 1.8 to 2.4 nmol/min/mg of cell protein at the same temperature. PMID:9361407

  2. Radical-radical interactions among oxidized guanine bases including guanine radical cation and dehydrogenated guanine radicals.

    PubMed

    Zhao, Jing; Wang, Mei; Yang, Hongfang; Zhang, Meng; Liu, Ping; Bu, Yuxiang

    2013-09-19

    We present here a theoretical investigation of the structural and electronic properties of di-ionized GG base pairs (G(•+)G(•+),G(-H1)(•)G(•+), and G(-H1)(•)G(-H1)(•)) consisting of the guanine cation radical (G(•+)) and/or dehydrogenated guanine radical (G(-H1)(•)) using density functional theory calculations. Different coupling modes (Watson-Crick/WC, Hoogsteen/Hoog, and minor groove/min hydrogen bonding, and π-π stacking modes) are considered. We infer that a series of G(•+)G(•+) complexes can be formed by the high-energy radiation. On the basis of density functional theory and complete active space self-consistent (CASSCF) calculations, we reveal that in the H-bonded and N-N cross-linked modes, (G(•+)G(•+))WC, (G(-H1)(•)G(-H1)(•))WC, (G(-H1)(•)G(-H1)(•))minI, and (G(-H1)(•)G(-H1)(•))minIII have the triplet ground states; (G(•+)G(•+))HoogI, (G(-H1)(•)G(•+))WC, (G(-H1)(•)G(•+))HoogI, (G(-H1)(•)G(•+))minI, (G(-H1)(•)G(•+))minII, and (G(-H1)(•)G(-H1)(•))minII possess open-shell broken-symmetry diradical-characterized singlet ground states; and (G(•+)G(•+))HoogII, (G(•+)G(•+))minI, (G(•+)G(•+))minII, (G(•+)G(•+))minIII, (G(•+)G(•+))HoHo, (G(-H1)(•)G(•+))minIII, (G(-H1)(•)G(•+))HoHo, and (G(-H1)(•)G(-H1)(•))HoHo are the closed-shell systems. For these H-bonded diradical complexes, the magnetic interactions are weak, especially in the diradical G(•+)G(•+) series and G(-H1)(•)G(-H1)(•) series. The magnetic coupling interactions of the diradical systems are controlled by intermolecular interactions (H-bond, electrostatic repulsion, and radical coupling). The radical-radical interaction in the π-π stacked di-ionized GG base pairs ((G(•+)G(•+))ππ, (G(-H1)(•)G(•+))ππ, and (G(-H1)(•)G(-H1)(•))ππ) are also considered, and the magnetic coupling interactions in these π-π stacked base pairs are large. This is the first theoretical prediction that some di

  3. Detailed modeling of low-temperature propane oxidation: 1. The role of the propyl + O(2) reaction.

    PubMed

    Huynh, Lam K; Carstensen, Hans-Heinrich; Dean, Anthony M

    2010-06-24

    Accurate description of reactions between propyl radicals and molecular oxygen is an essential prerequisite for modeling of low-temperature propane oxidation because their multiple reaction pathways either accelerate the oxidation process via chain branching or inhibit it by forming relatively stable products. The CBS-QB3 level of theory was used to construct potential energy surfaces for n-C(3)H(7) + O(2) and i-C(3)H(7) + O(2). High-pressure rate constants were calculated using transition state theory with corrections for tunneling and hindered rotations. These results were used to derive pressure- and temperature-dependent rate constants for the various channels of these reactions under the framework of the Quantum Rice-Ramsperger-Kassel (QRRK) and the modified strong collision (MSC) theories. This procedure resulted in a thermodynamically consistent C(3)H(7) + O(2) submechanism, which was either used directly or as part of a larger extended detailed kinetic mechanism to predict the loss of propyl and the product yields of propylene and HO(2) over a wide range of temperatures, pressures, and residence times. The overall good agreement between predicted and experimental data suggests that this reaction subset is reliable and should be able to properly account for the reactions of propyl radicals with O(2) in propane oxidation. It is also demonstrated that for most conditions of practical interest only a small subset of reactions (e.g., isomerization, concerted elimination of HO(2), and stabilization) controls the oxidation kinetics, which makes it possible to considerably simplify the mechanism. Moreover, we observed strong similarities in the rate coefficients within each reaction class, suggesting the potential for development of relatively simple rate constant estimation rules that could be applied to analogous reactions involving hydrocarbon radicals that are too large to allow accurate detailed electronic structure calculations. PMID:20509639

  4. Effect of Sodium on the Catalytic Properties of VOx/CeO2 Catalysts for Oxidative Dehydrogenation of Methanol

    SciTech Connect

    Li, Yan; Wei, Zhehao; Sun, Junming; Gao, Feng; Peden, Charles HF; Wang, Yong

    2013-03-21

    A series of VOx/CeO2 catalysts with various sodium loadings (Na/V ratio from 0 to 1) has been studied for oxidative dehydrogenation (ODH) of methanol. The effect of sodium on the surface structure, redox properties, and surface acidity/basicity of VOx/CeO2 was investigated using hydrogen temperature-programmed reduction (H2-TPR), Raman spectroscopy, and Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT). The experimental results indicate that the effect of sodium on VOx/CeO2 is highly dependent on the Na/V ratio. At a low Na/V ratio (Na/V<0.25), sodium addition only slightly decreases the redox properties of VOx/CeO2 and has little effect on its activity and selectivity to formaldehyde, even though the Brönsted acidity is almost completely eliminated at a Na/V ratio of 0.25. At a high Na/V ratio (Na/V>0.25), sodium addition greatly alters the nature of the active sites by V-O-Ce bond cleavage and V-O-Na bond formation, leading to significantly reduced activity of the VOx/CeO2 catalysts. At Na/V>0.25, the selectivity to formaldehyde also decreases with increasing Na/V ratio due to: (1) the suppressed reducibility of VOx, and (2) increased basicity leading to increased CO2.

  5. Development of an oxidative dehydrogenation-based fluorescent probe for Cu2+ and its biological imaging in living cells.

    PubMed

    Fan, Jiangli; Liu, Xiaojian; Hu, Mingming; Zhu, Hao; Song, Fengling; Peng, Xiaojun

    2012-07-20

    Based on a boron dipyrromethene (BODIPY) derivative containing an N, O and S tridentate ligand, a Cu(2+) fluorescent probe BTCu was developed. The detection mechanism was verified as Cu(2+)-promoted oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu(+)-Schiff base complex. Free BTCu exhibited a maximum absorption wavelength at 496 nm, and a very weak maximum emission at 511 nm. Upon addition of various metals ions, it showed large fluorescence enhancement toward Cu(2+) (417-fold in MeCN and 103-fold in MeCN/HEPES solution, respectively) with high selectivity. The detection limits are as low as 1.74×10(-8) M and 4.96×10(-8) M in the two different solutions, respectively. And BTCu could work in a wide pH range with an extraordinary low pK(a) of 1.21±0.06. Using fluorescence microscopy, the probe was shown to be capable of penetrating into living cells and imaging intracellular Cu(2+) changes. PMID:22713923

  6. A La-doped Mg-Al mixed metal oxide supported copper catalyst with enhanced catalytic performance in transfer dehydrogenation of 1-decanol.

    PubMed

    Zhang, Ming; Zhao, Yajie; Liu, Qian; Yang, Lan; Fan, Guoli; Li, Feng

    2016-01-21

    In the present work, a La-doped Mg-Al mixed metal oxide supported copper catalyst (Cu/La-MgAlO) was synthesized through a layered double hydroxide precursor route. The materials were characterized by powder X-ray diffraction, transmission electron microscopy, CO2-temperature programmed desorption, Fourier transform infrared spectra of CO2 absorption, and X-ray photoelectron spectroscopy. The results revealed that the introduction of a trace amount of La could significantly improve the surface basicity of the Cu/La-MgAlO catalyst, especially strong Lewis basicity. Compared with the undoped supported Cu catalyst, Cu/La-MgAlO exhibited much higher activity and selectivity in the liquid-phase transfer dehydrogenation of 1-decanol with a 1-decanal yield up to 89%. The excellent catalytic efficiency was mainly ascribed to the surface cooperation between the Lewis basic sites and the adjacent Cu(0)/Cu(+) species. That is, basic sites, especially strong-strength basic sites, held the key to the abstraction of protons from the hydroxyl group in 1-decanol, while the adjacent Cu(0) and Cu(+) species were responsible for the hydrogen transfer and the adsorption of styrene in the transfer dehydrogenation and hydrogenation reactions, respectively. This study provides a new method for designing cost-effective supported copper-based catalysts highly efficient for the transfer dehydrogenation of primary aliphatic alcohols by modifying the surface basicity of metal oxide supports. PMID:26659760

  7. Deactivation of a mixed oxide catalyst of Mo-V-Te-Nb-O composition in the reaction of oxidative ethane dehydrogenation

    NASA Astrophysics Data System (ADS)

    Mishanin, I. I.; Kalenchuk, A. N.; Maslakov, K. I.; Lunin, V. V.; Koklin, A. E.; Finashina, E. D.; Bogdan, V. I.

    2016-06-01

    The operational stability of a mixed oxide catalyst of Mo-V-Te-Nb-O composition in the oxidative dehydrogenation of ethane (ratio of C2H6: O2 = 3: 1) is studied in a flow reactor at temperatures of 340-400°C, a pressure of 1 atm, and a WHSV of the feed mixture of 800 h-1. It is found that the selectivity toward ethylene is 98% at 340°C, but the conversion of ethane at this temperature is only 6%; when the temperature is raised to 400°C, the conversion of ethane is increased to 37%, while the selectivity toward ethylene is reduced to 85%. Using physical and chemical means (XPS, SEM), it is found that the lack of oxidant in the reaction mixture leads to irreversible changes in the catalyst, i.e., reduced selectivity and activity. Raising the reaction temperature to 400°C allows the reduction of tellurium by ethane, from the +6 oxidation state to the zerovalent state, with its subsequent sublimation and the destruction of the catalytically active and selective phase; in its characteristics, the catalyst becomes similar to the Mo-V-Nb-O system containing no tellurium.

  8. Oxidative dehydrogenation of cyclohexene on size selected subnanometer cobalt clusters: improved catalytic performance via structural fluxionality of cluster-assembled nanostructures.

    SciTech Connect

    Lee, S.; Di Vece, M.; Lee, B.; Seifert, S.; Winans, R. E.; Vajda, S.

    2012-01-01

    The catalytic activity of oxide-supported metal nanoclusters strongly depends on their size and support. In this study, the origin of morphology transformation and chemical state changes during the oxidative dehydrogenation of cyclohexene was investigated in terms of metal-support interactions. Model catalyst systems were prepared by deposition of size selected subnanometer Co{sub 27{+-}4} clusters on various metal oxide supports (Al{sub 2}O{sub 3}, ZnO and TiO{sub 2} and MgO). The oxidation state and reactivity of the supported cobalt clusters were investigated by temperature programmed reaction (TPRx) and in situ grazing incidence X-ray absorption (GIXAS) during oxidative dehydrogenation of cyclohexene, while the sintering resistance monitored with grazing incidence small angle X-ray scattering (GISAXS). The activity and selectivity of cobalt clusters shows strong dependence on the support. GIXAS reveals that metal-support interaction plays a key role in the reaction. The most pronounced support effect is observed for MgO, where during the course of the reaction in its activity, composition and size dynamically evolving nanoassembly is formed from subnanometer cobalt clusters.

  9. Chiral Brønsted Acid Catalyzed Enantioselective Phosphonylation of Allylamine via Oxidative Dehydrogenation Coupling.

    PubMed

    Cheng, Ming-Xing; Ma, Ran-Song; Yang, Qiang; Yang, Shang-Dong

    2016-07-01

    A new strategy for the synthesis of chiral α-amino phosphonates by enantioselective C-H phosphonylation of allylamine with phosphite in the presence of a chiral Brønsted acid catalyst has been developed. This protocol successfully integrates direct C-H oxidation with asymmetric phosphonylation and exhibits high enantioselectivity. PMID:27331612

  10. Niobium phosphates as new highly selective catalysts for the oxidative dehydrogenation of ethane.

    PubMed

    Weng, Weihao; Davies, Mathew; Whiting, Gareth; Solsona, Benjamin; Kiely, Christopher J; Carley, Albert F; Taylor, Stuart H

    2011-10-14

    Several niobium phosphate phases have been prepared, fully characterized and tested as catalysts for the selective oxidation of ethane to ethylene. Three distinct niobium phosphate catalysts were prepared, and each was comprised predominantly of a different bulk phase, namely Nb(2)P(4)O(15), NbOPO(4) and Nb(1.91)P(2.82)O(12). All of the niobium phosphate catalysts showed high selectivity towards ethylene, but the best catalyst was Nb(1.91)P(2.82)O(12), which was produced from the reduction of niobium oxide phosphate (NbOPO(4)) by hydrogen. It was particularly selective for ethylene, giving ca. 95% selectivity at 5% conversion, decreasing to ca. 90% at 15% conversion, and only produced low levels of carbon oxides. It was also determined that the only primary product from ethane oxidation over this catalyst was ethylene. Catalyst activity also increased with time-on-line, and this behaviour was ascribed to an increase of the concentration of the Nb(1.91)P(2.82)O(12) phase, as partially transformed NbOPO(4), formed during preparation, was converted to Nb(1.91)P(2.82)O(12) during use. Catalysts with predominant phases of Nb(2)P(4)O(15) and NbOPO(4) also showed appreciable activity and selectivities to ethylene with values around 75% and 85% respectively at 5% ethane conversion. The presence of phosphorous is required to achieve high ethylene selectivity, as orthorhombic and monoclinic Nb(2)O(5) catalysts showed similar activity, but displayed selectivities to ethylene that were <20% under the same reaction conditions. To the best of our knowledge, this is the first time that niobium phosphates have been shown to be highly selective catalysts for the oxidation of ethane to ethylene, and demonstrates that they are worthy candidates for further study. PMID:21881631

  11. A biomimetic pathway for vanadium-catalyzed aerobic oxidation of alcohols: evidence for a base-assisted dehydrogenation mechanism.

    PubMed

    Wigington, Bethany N; Drummond, Michael L; Cundari, Thomas R; Thorn, David L; Hanson, Susan K; Scott, Susannah L

    2012-11-19

    The first step in the catalytic oxidation of alcohols by molecular O(2), mediated by homogeneous vanadium(V) complexes [LV(V)(O)(OR)], is ligand exchange. The unusual mechanism of the subsequent intramolecular oxidation of benzyl alcoholate ligands in the 8-hydroxyquinolinato (HQ) complexes [(HQ)(2)V(V)(O)(OCH(2)C(6)H(4)-p-X)] involves intermolecular deprotonation. In the presence of triethylamine, complex 3 (X = H) reacts within an hour at room temperature to generate, quantitatively, [(HQ)(2)V(IV)(O)], benzaldehyde (0.5 equivalents), and benzyl alcohol (0.5 equivalents). The base plays a key role in the reaction: in its absence, less than 12% conversion was observed after 72 hours. The reaction is first order in both 3 and NEt(3), with activation parameters ΔH(≠)=(28±4) kJ mol(-1) and ΔS(≠)=(-169±4) J K(-1)  mol(-1). A large kinetic isotope effect, 10.2±0.6, was observed when the benzylic hydrogen atoms were replaced by deuterium atoms. The effect of the para substituent of the benzyl alcoholate ligand on the reaction rate was investigated using a Hammett plot, which was constructed using σ(p). From the slope of the Hammett plot, ρ=+(1.34±0.18), a significant buildup of negative charge on the benzylic carbon atom in the transition state is inferred. These experimental findings, in combination with computational studies, support an unusual bimolecular pathway for the intramolecular redox reaction, in which the rate-limiting step is deprotonation at the benzylic position. This mechanism, that is, base-assisted dehydrogenation (BAD), represents a biomimetic pathway for transition-metal-mediated alcohol oxidations, differing from the previously identified hydride-transfer and radical pathways. It suggests a new way to enhance the activity and selectivity of vanadium catalysts in a wide range of redox reactions, through control of the outer coordination sphere. PMID:23080554

  12. The role of CO2 as a soft oxidant for dehydrogenation of ethylbenzene to styrene over a high-surface-area ceria catalyst

    SciTech Connect

    Zhang, Li; Wu, Zili; Nelson, Nicholas; Sadow, Aaron D.; Slowing, Igor I.; Overbury, Steven H.

    2015-09-22

    Catalytic performance and the nature of surface adsorbates were investigated for high-surface-area ceria during ethylbenzene oxidative dehydrogenation (ODH) reaction using CO2 as a soft oxidant. A template assisted method was used to synthesize the high-surface-area ceria. The interactions between ethylbenzene, styrene and CO2 on the surface of ceria and the role of CO2 for the ethylbenzene ODH reaction have been investigated in detail by using activity test, in situ Diffuse Reflectance Infrared and Raman spectroscopy. Not only did CO2 as an oxidant favor the higher yield of styrene, but it also inhibited the deposition of coke during the ethylbenzene ODH reaction. Ethylbenzene ODH reaction over ceria followed a two-step pathway: Ethylbenzene is first dehydrogenated to styrene with H2 formed simultaneously, and then CO2 reacts with H2 via the reverse water gas shift. The styrene produced can easily polymerize to form polystyrene, a key intermediate for coke formation. In the absence of CO2, the polystyrene transforms into graphite-like coke at temperatures above 500 °C, which leads to catalyst deactivation. While in the presence of CO2, the coke deposition can be effectively removed via oxidation with CO2.

  13. The role of CO2 as a soft oxidant for dehydrogenation of ethylbenzene to styrene over a high-surface-area ceria catalyst

    DOE PAGESBeta

    Zhang, Li; Wu, Zili; Nelson, Nicholas; Sadow, Aaron D.; Slowing, Igor I.; Overbury, Steven H.

    2015-09-22

    Catalytic performance and the nature of surface adsorbates were investigated for high-surface-area ceria during ethylbenzene oxidative dehydrogenation (ODH) reaction using CO2 as a soft oxidant. A template assisted method was used to synthesize the high-surface-area ceria. The interactions between ethylbenzene, styrene and CO2 on the surface of ceria and the role of CO2 for the ethylbenzene ODH reaction have been investigated in detail by using activity test, in situ Diffuse Reflectance Infrared and Raman spectroscopy. Not only did CO2 as an oxidant favor the higher yield of styrene, but it also inhibited the deposition of coke during the ethylbenzene ODHmore » reaction. Ethylbenzene ODH reaction over ceria followed a two-step pathway: Ethylbenzene is first dehydrogenated to styrene with H2 formed simultaneously, and then CO2 reacts with H2 via the reverse water gas shift. The styrene produced can easily polymerize to form polystyrene, a key intermediate for coke formation. In the absence of CO2, the polystyrene transforms into graphite-like coke at temperatures above 500 °C, which leads to catalyst deactivation. While in the presence of CO2, the coke deposition can be effectively removed via oxidation with CO2.« less

  14. Nitrous Oxide as a Hydrogen Acceptor for the Dehydrogenative Coupling of Alcohols.

    PubMed

    Gianetti, Thomas L; Annen, Samuel P; Santiso-Quinones, Gustavo; Reiher, Markus; Driess, Matthias; Grützmacher, Hansjörg

    2016-01-26

    The oxidation of alcohols with N2O as the hydrogen acceptor was achieved with low catalyst loadings of a rhodium complex that features a cooperative bis(olefin)amido ligand under mild conditions. Two different methods enable the formation of either the corresponding carboxylic acid or the ester. N2 and water are the only by-products. Mechanistic studies supported by DFT calculations suggest that the oxygen atom of N2O is transferred to the metal center by insertion into the Rh-H bond of a rhodium amino hydride species, generating a rhodium hydroxy complex as a key intermediate. PMID:26693955

  15. The first example of a centro-symmetrical bis(imido)-bridged dinuclear cobalt(III) complex: synthesis via oxidative dehydrogenation and phenoxazinone synthase activity.

    PubMed

    Panja, Anangamohan; Guionneau, Philippe

    2013-04-14

    A bis(imido)-bridged dinuclear cobalt(III) complex, [Co2(amp)2(μ-imp)2Cl2]Cl2·2H2O () [amp = 2-aminomethylpyridine; imp = 2-iminomethylpyridine anion], was synthesized by the reaction of cobalt(II) chloride with 2-aminomethylpyridine in the presence of alkaline hydrogen peroxide at room temperature. X-ray crystallography reveals that both the metal centres in the molecule are related to each other through an inversion centre, and the geometry of each of the Co(III) ions is a distorted octahedral structure having a CoN5Cl coordination environment. The most important feature of the structure is the modification of half of the coordinated amines by the oxidative dehydrogenation process which involves double bridging in the complex cation. To the best of our knowledge, this is the first example of a bis(imido)-bridged dinuclear cobalt(III) complex derived from metal-assisted oxidative dehydrogenation of the coordinated primary amine ligand. Complex was found to be an excellent functional model for the phenoxazinone synthase, catalyzing the oxidative coupling of 2-aminophenol to the corresponding 2-aminophenoxazinone chromophore in dioxygen saturated methanol. The detailed kinetic investigations reveal that the phenoxazinone chromophore is produced via a potential complex-substrate intermediate. PMID:23396321

  16. Efficient combination of promoter and catalyst for chromic acid oxidation of propan-2-ol to acetone in aqueous acid media at room temperature.

    PubMed

    Mukherjee, Kakali; Saha, Rumpa; Ghosh, Aniruddha; Ghosh, Sumanta K; Saha, Bidyut

    2013-01-15

    Oxidation of propan-2-ol to acetone was carried out in aqueous media at room temperature. The effect of promoter (PA, bpy, phen), micellar catalyst (SDS, CPC, TX-100) and their combination has been studied. The reactions were performed under the condition [Propan-2-ol]T≫[Cr(VI)]T at 30°C. Then kobs and half life of all the reaction were determined to identify which promoter and which combination are the most effective for this oxidation. Among the promoters phen accelerates the reaction most in aqueous media. In absence of promoters anionic surfactant SDS increases the rate more effectively than neutral surfactant TX-100. CPC retards the rate in comparison to aqueous media. The rate of the oxidation is highest in presence of the combination of bpy and SDS. PMID:23123236

  17. Mg3(VO4)2-MgO-ZrO2 nano-catalysts for oxidative dehydrogenation of n-butane.

    PubMed

    Lee, Jong Kwon; Seo, Hyun; Hong, Ung Gi; Yoo, Yeonshick; Cho, Young-Jin; Lee, Jinsuk; Park, Gle; Chang, Hosik; Song, In Kyu

    2014-11-01

    A series of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts with different vanadium content (X = 3.3, 5.3, 7.0, 10.2, and 13.4) were prepared by a single-step citric acid-derived sol-gel method for use in the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The effect of vanadium content of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts on their physicochemical properties and catalytic activities in the oxidative dehydrogenation of n-butane was investigated. Successful formation of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts was confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The catalytic performance of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts strongly depended on vanadium content. All the X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts showed a stable catalytic performance without catalyst deactivation during the reaction. Among the catalysts tested, 7.0-Mg3(VO4)2-MgO-ZrO2 nano-catalyst showed the best catalytic performance in terms of yield for total dehydrogenation products (TDP, n-butene and 1,3-butadiene). TPRO (temperature-programmed reoxidation) experiments were carried out to measure the oxygen capacity of the catalyst. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing oxygen capacity of the catalyst. PMID:25958621

  18. Oxidative dehydrogenation of n-butane over magnesium vanadate nano-catalysts supported on magnesia-zirconia: effect of vanadium content.

    PubMed

    Lee, Jong Kwon; Hong, Ung Gi; Yoo, Yeonshick; Cho, Young-Jin; Lee, Jinsuk; Chang, Hosik; Song, In Kyu

    2013-12-01

    Magnesia-zirconia (MgO-ZrO2) support was prepared by a sol-gel method, and magnesium vanadate nano-catalysts supported on magnesia-zirconia (X-Mg3(VO4)2/MgO-ZrO2) were then prepared by a wet impregnation method with a variation of vanadium content (X = 6.6, 9.9, 12.8, 15.2, and 19.1 wt%). X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts were applied to the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The formation of X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts was well confirmed by XRD, XPS, and ICP-AES analyses. 15.2-Mg3(VO4)2/MgO-ZrO2 and 19.1-Mg3(VO4)2/MgO-ZrO2 catalysts experienced a catalyst deactivation, while the other Mg3(VO4)2/MgO-ZrO2 catalysts showed a stable catalytic performance during the whole reaction time. The effect of oxygen property of X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts on the catalytic performance in the oxidative dehydrogenation of n-butane was investigated. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance, while oxygen mobility of the catalyst played an important role in the catalyst stability. Among the catalysts tested, 12.8-Mg3(VO4)2/MgO-ZrO2 catalyst showed the best catalytic performance in terms of yield for TDP (total dehydrogenation products). PMID:24266201

  19. Over-Oxidation as the Key Step in the Mechanism of the MoCl5-Mediated Dehydrogenative Coupling of Arenes.

    PubMed

    Schubert, Moritz; Franzmann, Peter; Wünsche von Leupoldt, Anica; Koszinowski, Konrad; Heinze, Katja; Waldvogel, Siegfried R

    2016-01-18

    Molybdenum pentachloride is an unusually powerful reagent for the dehydrogenative coupling of arenes. Owing to the high reaction rate using MoCl5, several labile moieties are tolerated in this transformation. The mechanistic course of the reaction was controversially discussed although indications for a single electron transfer as the initial step were found recently. Herein, based on a combined study including synthetic investigations, electrochemical measurements, EPR spectroscopy, DFT calculations, and mass spectrometry, we deduct a highly consistent mechanistic scenario: MoCl5 acts as a one-electron oxidant in the absence of TiCl4 and as two-electron oxidant in the presence of TiCl4, but leads to an over-oxidized intermediate in both cases, which protects it from side reactions. In the course of aqueous work-up the reagent waste (Mo(III/IV) species) acts as reducing agent generating the desired organic C-C coupling product. PMID:26473303

  20. An operando Raman study of molecular structure and reactivity of molybdenum(VI) oxide supported on anatase for the oxidative dehydrogenation of ethane.

    PubMed

    Tsilomelekis, George; Boghosian, Soghomon

    2012-02-21

    Supported molybdenum oxide catalysts on TiO(2) (anatase) with surface densities in the range of 1.8-17.0 Mo per nm(2) were studied at temperatures of 410-480 °C for unraveling the configuration and molecular structure of the deposited (MoO(x))(n) species and examining their behavior for the ethane oxidative dehydrogenation (ODH). In situ Raman and in situ FTIR spectra under oxidizing conditions combined with (18)O/(16)O isotope exchange studies provide the first sound evidence for mono-oxo configuration for the deposited (MoO(x))(n) species on anatase. Isolated O=Mo(-O-)(3) tetra-coordinated species in C(3v)-like symmetry prevail at all surface coverages with a low presence of associated (polymeric) species (probably penta-coordinated) evidenced at high coverages, below the approximate monolayer of 6 Mo per nm(2). A mechanistic scenario for (18)O/(16)O isotope exchange and next-nearest-neighbor vibrational isotope effect is proposed at the molecular level to account for the pertinent spectral observations. Catalytic measurements for ethane ODH with simultaneous monitoring of operando Raman spectra were performed. The selectivity to ethylene increases with increasing surface density up to the monolayer coverage, where primary steps of ethane activation follow selective reaction pathways leading to ∼100% C(2)H(4) selectivity. The operando Raman spectra and a quantitative exploitation of the relative normalized Mo=O band intensities for surface densities of 1.8-5.9 Mo per nm(2) and various residence times show that the terminal Mo=O sites are involved in non-selective reaction turnovers. Reaction routes follow primarily non-selective pathways at low coverage and selective pathways at high coverage. Trends in the initial rates of ethane consumption (apparent reactivity per Mo) as a function of Mo surface density are discussed on the basis of several factors. PMID:22143865

  1. Effects of Alloyed Metal on the Catalysis Activity of Pt for Ethanol Partial Oxidation: Adsorption and Dehydrogenation on Pt3M (M=Pt, Ru, Sn, Re, Rh, and Pd)

    PubMed Central

    Xu, Zhen-Feng; Wang, Yixuan

    2011-01-01

    The adsorption and dehydrogenation reactions of ethanol over bimetallic clusters, Pt3M (M = Pt, Ru, Sn, Re, Rh, and Pd), have been extensively investigated with density functional theory. Both the α-hydrogen and hydroxyl adsorptions on Pt as well as on the alloyed transition metal M sites of PtM were considered as initial reaction steps. The adsorptions of ethanol on Pt and M sites of some PtM via the α-hydrogen were well established. Although the α-hydrogen adsorption on Pt site is weaker than the hydroxyl, the potential energy profiles show that the dehydrogenation via the α-hydrogen path has much lower energy barrier than that via the hydroxyl path. Generally for the α-hydrogen path the adsorption is a rate-determining-step because of rather low dehydrogenation barrier for the α-hydrogen adsorption complex (thermodynamic control), while the hydroxyl path is determined by its dehydrogenation step (kinetic control). The effects of alloyed metal on the catalysis activity of Pt for ethanol partial oxidation, including adsorption energy, energy barrier, electronic structure, and eventually rate constant were discussed. Among all of the alloyed metals only Sn enhances the rate constant of the dehydrogenation via the α-hydrogen path on the Pt site of Pt3Sn as compared with Pt alone, which interprets why the PtSn is the most active to the oxidation of ethanol. PMID:22102920

  2. Effects of Alloyed Metal on the Catalysis Activity of Pt for Ethanol Partial Oxidation: Adsorption and Dehydrogenation on Pt(3)M (M=Pt, Ru, Sn, Re, Rh, and Pd).

    PubMed

    Xu, Zhen-Feng; Wang, Yixuan

    2011-10-27

    The adsorption and dehydrogenation reactions of ethanol over bimetallic clusters, Pt(3)M (M = Pt, Ru, Sn, Re, Rh, and Pd), have been extensively investigated with density functional theory. Both the α-hydrogen and hydroxyl adsorptions on Pt as well as on the alloyed transition metal M sites of PtM were considered as initial reaction steps. The adsorptions of ethanol on Pt and M sites of some PtM via the α-hydrogen were well established. Although the α-hydrogen adsorption on Pt site is weaker than the hydroxyl, the potential energy profiles show that the dehydrogenation via the α-hydrogen path has much lower energy barrier than that via the hydroxyl path. Generally for the α-hydrogen path the adsorption is a rate-determining-step because of rather low dehydrogenation barrier for the α-hydrogen adsorption complex (thermodynamic control), while the hydroxyl path is determined by its dehydrogenation step (kinetic control). The effects of alloyed metal on the catalysis activity of Pt for ethanol partial oxidation, including adsorption energy, energy barrier, electronic structure, and eventually rate constant were discussed. Among all of the alloyed metals only Sn enhances the rate constant of the dehydrogenation via the α-hydrogen path on the Pt site of Pt(3)Sn as compared with Pt alone, which interprets why the PtSn is the most active to the oxidation of ethanol. PMID:22102920

  3. Mesoporous xEr2O3·CoTiO3 composite oxide catalysts for low temperature dehydrogenation of ethylbenzene to styrene using CO2 as a soft oxidant

    DOE PAGESBeta

    Yue, Yanfeng; Zhang, Li; Chen, Jihua; Hensley, Dale K.; Dai, Sheng; Overbury, Steven H.

    2016-03-29

    A series of mesoporous xEr2O3·CoTiO3 composite oxide catalysts have been prepared using template method and tested as a new type of catalyst for the oxidative dehydrogenation of ethylbenzene to styrene by using CO2 as a soft oxidant. Among the catalysts tested, the 0.25Er2O3 CoTiO3 sample with a ratio of 1:4:4 content and calcined at 600 oC exhibited the highest ethylbenzene conversion (58%) and remarkable styrene selectivity (95%) at low temperature (450 °C).

  4. Atomic-Scale Determination of Active Facets on the MoVTeNb Oxide M1 Phase and Their Intrinsic Catalytic Activity for Ethane Oxidative Dehydrogenation.

    PubMed

    Melzer, Daniel; Xu, Pinghong; Hartmann, Daniela; Zhu, Yuanyuan; Browning, Nigel D; Sanchez-Sanchez, Maricruz; Lercher, Johannes A

    2016-07-25

    Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) has been used to image the basal {001} plane of the catalytically relevant M1 phase in MoVTeNb complex oxides. Facets {010}, {120}, and {210} are identified as the most frequent lateral termination planes of the crystals. Combination of STEM with He ion microscopy (HIM) images, Rietveld analysis, and kinetic tests reveals that the activation of ethane is correlated to the availability of facets {001}, {120}, and {210} at the surface of M1 crystals. The lateral facets {120} and {210} expose crystalline positions related to the typical active centers described for propane oxidation. Conversely, the low activity of the facet {010} is attributed to its configuration, consisting of only stable M6 O21 units connected by a single octahedron. Thus, we quantitatively demonstrated that differences in catalytic activity among M1 samples of equal chemical composition depend primarily on the morphology of the particles, which determines the predominant terminating facets. PMID:26990594

  5. Catalytic oxidative dehydrogenation process

    DOEpatents

    Schmidt, Lanny D.; Huff, Marylin

    2002-01-01

    A process for the production of a mono-olefin from a gaseous paraffinic hydrocarbon having at least two carbon atoms or mixtures thereof comprising reacting said hydrocarbons and molecular oxygen in the presence of a platinum catalyst. The catalyst consist essentially of platinum supported on alumina or zirconia monolith, preferably zirconia and more preferably in the absence of palladium, rhodium and gold.

  6. A study of the effect of cesium loading on the phase transformation of iron in iron phosphate over the oxidative dehydrogenation reactions

    NASA Astrophysics Data System (ADS)

    Khan, Faiza B.; Dasireddy, Venkata D. B. C.; Bharuth-Ram, K.; Masenda, H.; Friedrich, H. B.

    2015-04-01

    A phase specific iron orthophosphate catalyst, FePO4, was synthesized and promoted with cesium. This catalyst was subjected to oxidative dehydrogenation reactions to form an alkyl methacrylate. The phases of the catalyst, before and after the reactions, were studied as a function of different cesium loading. Mössbauer spectra of the catalysts show the change of the catalyst precursor FePO4, to i) the tridymite-like phase, ii) the reduced form, iron(II) pyrophosphate and Fe2 P 2 O 7, and iii) the α-phase of iron phosphate which is governed by the temperatures of oxidation. X-ray diffraction and Mössbauer measurements on the spent catalyst show a transformation of the catalyst to a mixture of phases.

  7. Periodic Density Functional Theory Study of the Oxidative Dehydrogenation of n-butane on the (001) Surface of V2O5

    NASA Astrophysics Data System (ADS)

    Hà, Nguyën Ngoc; Hue, Trán Thành; Tho, Nguyen Minh

    2009-03-01

    The oxidative dehydrogenation (ODH) of light alkanes is an attractive alternative for the production of more valuable alkenes. Considerable research efforts have been made towards the development of catalysts active at low temperature and selective in the formation of alkenes. Most catalysts described in the literature are based on Vanadium oxide as the main component and many studies concerning the reaction mechanism during the ODH of short alkanes have been performed but debates still today exist. The objective of this work is to study in detail theoretically the kinetics of n-butane ODH on the (001) surface of V2O5. The density functional theory using a plane-waves basis set and pseudopotential has been used for this purpose.

  8. Silane-propane ignitor/burner

    DOEpatents

    Hill, Richard W.; Skinner, Dewey F.; Thorsness, Charles B.

    1985-01-01

    A silane propane burner for an underground coal gasification process which is used to ignite the coal and to controllably retract the injection point by cutting the injection pipe. A narrow tube with a burner tip is positioned in the injection pipe through which an oxidant (oxygen or air) is flowed. A charge of silane followed by a supply of fuel, such as propane, is flowed through the tube. The silane spontaneously ignites on contact with oxygen and burns the propane fuel.

  9. Silane-propane ignitor/burner

    DOEpatents

    Hill, R.W.; Skinner, D.F. Jr.; Thorsness, C.B.

    1983-05-26

    A silane propane burner for an underground coal gasification process which is used to ignite the coal and to controllably retract the injection point by cutting the injection pipe. A narrow tube with a burner tip is positioned in the injection pipe through which an oxidant (oxygen or air) is flowed. A charge of silane followed by a supply of fuel, such as propane, is flowed through the tube. The silane spontaneously ignites on contact with oxygen and burns the propane fuel.

  10. Process for para-ethyltoluene dehydrogenation

    SciTech Connect

    Chu, C.C.

    1986-06-03

    A process is described of dehydrogenating para-ethyltoluene to selectively form para-methylstyrene comprising contacting to para-ethyltoluene under dehydrogenation reaction conditions with a catalyst composition comprising: (a) from about 30% to 60% by weight of iron oxide, calculated as ferric oxide; (b) from about 13% to 48% by weight of a potassium compound, calculated as potassium oxide; and (c) from about 0% to 5% by weight of a chromium compound, calculated as chromic oxide. The improvement is described comprising dehydrogenating the para-ethyltoluene with a catalyst composition comprising, in addition to the components (a), (b) and (c), a modifying component (d) capable of rendering the para-methylstyrene-containing dehydrogenation reaction effluent especially resistant to the subsequent formation of popcorn polymers when the dehydrogenation of para-ethyltoluene is conducted over the modified catalyst, the modifying component (d) being a bismuth compound present to the extent of from about 1% to 20% by weight of the catalyst composition, calculated as bismuth trioxide.

  11. Low Temperature Propane Oxidation over Co3O4 based Nano-array Catalysts. Ni Dopant Effect, Reaction Mechanism and Structural Stability

    DOE PAGESBeta

    Ren, Zheng; Wu, Zili; Gao, Puxian; Song, Wenqiao; Xiao, Wen; Guo, Yanbing; Ding, Jun; Suib, Steven L.; Gao, Pu-Xian

    2015-06-09

    Low temperature propane oxidation has been achieved by Co3O4-based nano-array catalysts featuring low catalytic materials loading. The Ni doping into the Co3O4 lattice has led to enhanced reaction kinetics at low temperature by promoting the surface lattice oxygen activity. In situ DRIFTS investigation in tandem with isotopic oxygen exchange reveals that the propane oxidation proceeds via Mars-van Krevelen mechanism where surface lattice oxygen acts as the active site whereas O2 in the reaction feed does not directly participate in CO2 formation. The Ni doping promotes the formation of less stable carbonates on the surface to facilitate the CO2 desorption. Themore » thermal stability of Ni doped Co3O4 decreases with increased Ni concentration while catalytic activity increases. A balance between enhanced activity and compromised thermal stability shall be considered in the Ni doped Co3O4 nano-array catalysts for low temperature hydrocarbon oxidation. This study provides useful and timely guidance for rational catalyst design toward low temperature catalytic oxidation.« less

  12. Low Temperature Propane Oxidation over Co3O4 based Nano-array Catalysts. Ni Dopant Effect, Reaction Mechanism and Structural Stability

    SciTech Connect

    Ren, Zheng; Wu, Zili; Gao, Puxian; Song, Wenqiao; Xiao, Wen; Guo, Yanbing; Ding, Jun; Suib, Steven L.; Gao, Pu-Xian

    2015-06-09

    Low temperature propane oxidation has been achieved by Co3O4-based nano-array catalysts featuring low catalytic materials loading. The Ni doping into the Co3O4 lattice has led to enhanced reaction kinetics at low temperature by promoting the surface lattice oxygen activity. In situ DRIFTS investigation in tandem with isotopic oxygen exchange reveals that the propane oxidation proceeds via Mars-van Krevelen mechanism where surface lattice oxygen acts as the active site whereas O2 in the reaction feed does not directly participate in CO2 formation. The Ni doping promotes the formation of less stable carbonates on the surface to facilitate the CO2 desorption. The thermal stability of Ni doped Co3O4 decreases with increased Ni concentration while catalytic activity increases. A balance between enhanced activity and compromised thermal stability shall be considered in the Ni doped Co3O4 nano-array catalysts for low temperature hydrocarbon oxidation. This study provides useful and timely guidance for rational catalyst design toward low temperature catalytic oxidation.

  13. Synergy between hexavalent chromium ions and TiO2 nanoparticles inside TUD-1 in the photocatalytic oxidation of propane, a spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hamdy, Mohamed S.

    2016-02-01

    Siliceous TUD-1 mesoporous material was bi-functionalized by titanium dioxide nanoparticles and hexavalent chromium ions. The synthesis was carried out by one-pot procedure based on sol-gel technique. The photocatalytic performance of the prepared material was evaluated in the oxidation of propane under the illumination of ultraviolet light (wavelength = 360 nm) and monitored by in situ Fourier transform infrared spectroscopy. The photocatalytic activity of the prepared material exhibited an extra-ordinary activity than the reference samples that contain either hexavalent chromium ions or titanium dioxide nanoparticles only, confirming the true synergy between hexavalent chromium and tetravalent titanium ions of titanium dioxide nanoparticles.

  14. Zinc(II), iron(II/III) and ruthenium(II) complexes of o-phenylenediamine derivatives: oxidative dehydrogenation and photoluminescence.

    PubMed

    Chaudhuri, Satyabrata; Patra, Sarat Chandra; Saha, Pinaki; Saha Roy, Amit; Maity, Suvendu; Bera, Sachinath; Saha Sardar, Pinki; Ghosh, Sanjib; Weyhermüller, Thomas; Ghosh, Prasanta

    2013-11-14

    Reactions of benzoyl pyridine, o-phenylenediamine and anhydrous ZnX2 in methanol afford imine complexes [Zn(L1)X2] (X = Cl, 1; X = Br, 2) in good yields (L1 = (E)-N(1)-(phenyl(pyridin-2-yl)methylene)benzene-1,2-diamine). The reduction of 1 with NaBH4 affords (E)-N(1)-(phenyl(pyridine-2-yl)methylene)benzene-1,2-diamine (L2H). The reaction of L2H with [Ru(II)(PPh3)3Cl2] results in the oxidative dehydrogenation to L1 generating cis-[Ru(II)(L1)(PPh3)Cl2] (3). The reaction of L2H with salicylaldehyde affords (E)-2-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)imino)methyl)phenol (L3H2). The reaction of L3H2 with anhydrous FeCl3 in CH3OH affords cis-[Fe(III)(L3H(-))Cl2] (4). Reaction of L3H2 with [Ru(II)(PPh3)3Cl2] results in the oxidative dehydrogenation to diimine, L4H, affording trans-[Ru(II)(L4(-))(PPh3)2](+), which is isolated as trans-[Ru(II)(L4(-))(PPh3)2]PF6 (5(+)PF6(-)) (L4H = 2-((E)-(2-((E)-phenyl(pyridin-2-yl)methyleneamino)phenylimino)methyl)phenol). The reduction of L3H2 with NaBH4 produces 2-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)amino)methyl)phenol (L5H3). With iron(III) L5H3 undergoes oxidative dehydrogenation to L3H2 affording 4, while with [Ru(II)(PPh3)3Cl2], L5H3 undergoes 4e + 4H(+) transfer giving 5(+). A fluid solution of L3H2 at 298 K exhibits an emission band at 470 nm (λ(ex) = 330 nm, τ1 = 3.70 ns) and a weaker band at 525 nm (λ(ex) = 330, 390 nm, τ1 = 1.1 ns) at higher concentrations due to molecular aggregation, which are temperature dependent. 4 is brightly emissive (λ(ex) = 330 nm, λ(em) = 450 nm, Φ = 0.586, τ1 = 3.70 ns). Time resolved emission spectra (TRES) and lifetime measurements confirm that the lower energy absorption band of L3H2 at 390 nm, which is absent in complex 4, has a larger non-radiative rate constant (k(nr)). The redox innocent Al(III) adduct of L3H2 is fluorescent (λ(ex) = 330 nm, λ(em) = 450 nm, τ1 = 3.70 ns). On the contrary, the cis-[Fe(II)(L3H(-))Cl2](-) and cis-[Co(L3H(-))Cl2](-) analogues are non

  15. Reactions of dioxygen complexes. Oxidative dehydrogenation of 1,6-bis(2-pyridyl)-2,5-diazahexane through cobalt dioxygen complex formation

    SciTech Connect

    Basak, A.K.; Martell, A.E.

    1988-06-01

    The formation constants and oxygenation constants of the cobalt(II) complexes of 1,6-bis(2-pyridyl)-2,5-diazahexane (PYEN) have been determined by potentiometric equilibrium measurements under nitrogen and oxygen. The kinetics of the oxidative degradation of the coordinated ligand in the cobalt dioxygen complex have been measured spectrophotometrically, and the rate constants of two parallel degradation reactions have been determined. Both reactions were found to be second order, first order with respect to the concentration of the dioxygen complex and first order with respect to the hydroxide ion concentration. Kinetics and product analysis reveal that one of the terminal aminomethyl residues of the ligand PYEN undergoes two-electron oxidation to form the corresponding imine, which under the reaction conditions employed is converted to pyridine-2-carboxyaldehyde, identified semiquantitatively as the (2,6-dinitrophenyl)hydrazone. Comparisons of these results with those of systems investigated previously, and the large kinetic deuterium isotope effect for the dehydrogenation reaction, are employed as the basis of a proposed reaction mechanism, which involves deprotonation of an aliphatic amino group in a preequilibrium step. Reaction mechanisms are suggested. 30 references, 10 figures, 3 tables.

  16. Effect of varying the combustion parameters on the emissions of carbon monoxide and nitrogen oxides in the exhaust gases from propane-fueled vehicles.

    PubMed

    Roberge, B

    2000-05-01

    Propane-fueled forklifts are one source of carbon monoxide (CO) contamination of workplace air. The previous study carried out by the Quebec Occupational Health and Safety Research Institute dealt with worker exposure to CO during forklift use in buildings. It recommends that exhaust gas emissions be kept below a 1 percent concentration. However, this control has not produced a significant reduction in worker exposure to CO, when factors (ventilation, type of work tasks, and management of vehicle fleet) specific to companies are taken into account. Consequently, a reduction in CO emissions below the threshold of 0.3 percent should be considered. The experience acquired with propane-fueled ice resurfacers can be used to determine the effect of combustion parameters on exhaust gas emissions. It is known that a reduction in CO emissions from ice resurfacers resulted in the appearance of nitrogen oxides (NOx) and eventually in nitrogen dioxide (NO2) poisoning. Few publications present NOx results in relation to the CO measured in the exhaust gases of propane-fueled vehicles. The objective of this study is to define the level to which CO emissions can be reduced without increasing NOx concentrations. This real-situation study quantified the CO, NO, and NOx in the exhaust gases of a fleet of propane-fueled forklifts in relation to the mixture ratio. The results show the impact of the motor speed and mixture ratio on the CO, NO, and NO2 concentrations. They confirm an increase in NOx concentrations when CO concentrations are reduced. They also show that proper maintenance of forklifts combined with optimal adjustments can reduce CO and NOx emissions. The study proposes a compromise between CO and NOx emissions by taking into account worker health and safety as well as vehicle performance. Monitoring must be done to control air quality in work areas and worker exposure to CO and NO2. A forklift preventive maintenance program and general building ventilation are the favored

  17. Oxidative dehydrogenation of n-butane over vanadium magnesium oxide catalysts supported on nano-structured MgO and ZrO2: effect of oxygen capacity of the catalyst.

    PubMed

    Lee, Howon; Lee, Jong Kwon; Hong, Ung Gi; Song, In Kyu; Yoo, Yeonshick; Cho, Young-Jin; Lee, Jinsuk; Chang, Hosik; Jung, Ji Chul

    2012-07-01

    Vanadium-magnesium oxide catalysts supported on nano-structured MgO and ZrO2 (Mg3(VO4)2/MgO/ZrO2) were prepared by a wet impregnation method with a variation of Mg:Zr ratio (8:1, 4:1, 2:1, and 1:1). For comparison, Mg3(VO4)2/MgO and Mg3(VO4)2/ZrO2 catalysts were also prepared by a wet impregnation method. The prepared catalysts were applied to the oxidative dehydrogenation of n-butane in a continuous flow fixed-bed reactor. Mg3(VO4)2/MgO/ZrO2 (Mg:Zr = 4:1, 2:1, and 1:1) and Mg3(VO4)2/ZrO2 catalysts showed a stable catalytic activity during the whole reaction time, while Mg3(VO4)2/MgO/ZrO2 (8:1) and Mg3(VO4)2/MgO catalysts experienced a severe catalyst deactivation. Deactivation of Mg3(VO4)2/MgO/ZrO2 (8:1) and Mg3(VO4)2/MgO catalysts was due to their low oxygen mobility. Effect of oxygen capacity (the amount of oxygen in the catalyst involved in the reaction) of the supported Mg3(V04)2 catalysts on the catalytic performance in the oxidative dehydrogenation of n-butane was investigated. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic activity in the oxidative dehydrogenation of n-butane. A large oxygen capacity of the catalyst was favorable for obtaining a high catalytic activity in this reaction. Among the catalysts tested, Mg3(VO4)2/MgO/ZrO2 (4:1) catalyst with the largest oxygen capacity showed the best catalytic performance. PMID:22966706

  18. Dehydrogenative Coupling Reactions with Oxidized Guanidino-Functionalized Aromatic Compounds: Novel Options for σ-Bond Activation.

    PubMed

    Wild, Ute; Federle, Stefanie; Wagner, Arne; Kaifer, Elisabeth; Himmel, Hans-Jörg

    2016-08-16

    We present a new option for metal-free σ-bond activation, making use of oxidized, guanidino-functionalized aromatic compounds (GFAs). We demonstrate this new option by the homocoupling reactions of thiols and phosphines. The kinetics and the reaction pathway were studied by a number of experiments (including heterocoupling of thiols and phosphines), supported by quantum-chemical computations. Reaction of the oxidized GFA with p-dihydrobenzoquinone to give p-benzoquinone shows that typical proton-coupled electron-transfer reactions are also possible. PMID:27430589

  19. Highly regioselective hydride transfer, oxidative dehydrogenation, and hydrogen-atom abstraction in the thermal gas-phase chemistry of [Zn(OH)](+)/C3H8.

    PubMed

    Wu, Xiao-Nan; Zhao, Hai-Tao; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2014-12-28

    The thermal reactions of [Zn(OH)](+) with C3H8 have been studied by means of gas-phase experiments and computational investigation. Two types of C-H bond activation are observed in the experiment, and pertinent mechanistic features include inter alia: (i) the metal center of [Zn(OH)](+) serves as active site in the hydride transfer to generate [i-C3H7](+) as major product, (ii) generally, a high regioselectivity is accompanied by remarkable chemoselectivity: for example, the activation of a methyl C-H bond results mainly in the formation of water and [Zn(C3,H7)](+). According to computational work, this ionic product corresponds to [HZn(CH3CH=CH2)](+). Attack of the zinc center at a secondary C-H bond leads preferentially to hydride transfer, thus giving rise to the generation of [i-C3H7](+); (iii) upon oxidative dehydrogenation (ODH), liberation of CH3CH2=CH2 occurs to produce [HZn(H2O)](+). Both, ODH as well as H2O loss proceed through the same intermediate which is characterized by the fact that a methylene hydrogen atom from the substrate is transferred to the zinc and one hydrogen atom from the methyl group to the OH group of [Zn(OH)](+). The combined experimental/computational gas-phase study of C-H bond activation by zinc hydroxide provides mechanistic insight into related zinc-catalyzed large-scale processes and identifies the crucial role that the Lewis-acid character of zinc plays. PMID:25230924

  20. Hydrogen transport membranes for dehydrogenation reactions

    DOEpatents

    Balachandran; Uthamalingam

    2008-02-12

    A method of converting C.sub.2 and/or higher alkanes to olefins by contacting a feedstock containing C.sub.2 and/or higher alkanes with a first surface of a metal composite membrane of a sintered homogenous mixture of an Al oxide or stabilized or partially stabilized Zr oxide ceramic powder and a metal powder of one or more of Pd, Nb, V, Zr, Ta and/or alloys or mixtures thereof. The alkanes dehydrogenate to olefins by contact with the first surface with substantially only atomic hydrogen from the dehydrogenation of the alkanes passing through the metal composite membrane. Apparatus for effecting the conversion and separation is also disclosed.

  1. Efficiency gain of solid oxide fuel cell systems by using anode offgas recycle - Results for a small scale propane driven unit

    NASA Astrophysics Data System (ADS)

    Dietrich, Ralph-Uwe; Oelze, Jana; Lindermeir, Andreas; Spitta, Christian; Steffen, Michael; Küster, Torben; Chen, Shaofei; Schlitzberger, Christian; Leithner, Reinhard

    The transfer of high electrical efficiencies of solid oxide fuel cells (SOFC) into praxis requires appropriate system concepts. One option is the anode-offgas recycling (AOGR) approach, which is based on the integration of waste heat using the principle of a chemical heat pump. The AOGR concept allows a combined steam- and dry-reforming of hydrocarbon fuel using the fuel cell products steam and carbon dioxide. SOFC fuel gas of higher quantity and quality results. In combination with internal reuse of waste heat the system efficiency increases compared to the usual path of partial oxidation (POX). The demonstration of the AOGR concept with a 300 Wel-SOFC stack running on propane required: a combined reformer/burner-reactor operating in POX (start-up) and AOGR modus; a hotgas-injector for anode-offgas recycling to the reformer; a dynamic process model; a multi-variable process controller; full system operation for experimental proof of the efficiency gain. Experimental results proof an efficiency gain of 18 percentage points (η·POX = 23%, η·AOGR = 41%) under idealized lab conditions. Nevertheless, further improvements of injector performance, stack fuel utilization and additional reduction of reformer reformer O/C ratio and system pressure drop are required to bring this approach into self-sustaining operation.

  2. Effect of Oxygen Defects on the Catalytic Performance of VOx/CeO2 Catalysts for Oxidative Dehydrogenation of Methanol

    SciTech Connect

    Li, Yan; Wei, Zhehao; Gao, Feng; Kovarik, Libor; Baylon, Rebecca A.; Peden, Charles HF; Wang, Yong

    2015-05-01

    In this work, CeO2 nanocubes with controlled particle size and dominating (100) facets are synthesized as supports for VOx catalysts. Combined TEM, SEM, XRD, and Raman study reveals that the oxygen vacancy density of CeO2 supports can be tuned by tailoring the particle sizes without altering the dominating facets, where smaller particle sizes result in larger oxygen vacancy densities. At the same vanadium coverage, the VOx catalysts supported on small-sized CeO2 supports with higher oxygen defect densities exhibit promoted redox property and lower activation energy for methoxyl group decomposition, as evidenced by H2-TPR and methanol TPD study. These results further confirm that the presence of oxygen vacancies plays an important role in promoting the activity of VOx species in methanol oxidation. We gratefully acknowledge financial support from the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Part of this work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for the DOE by Battelle.

  3. Recent Progress in Dehydro(genative) Diels-Alder Reaction.

    PubMed

    Li, Wenbo; Zhou, Liejin; Zhang, Junliang

    2016-01-26

    In recent years, remarkable progress has been made in dehydro or dehydrogenative Diels-Alder (D-A) reactions. This Minireview gives an overview of the major two strategies for dehydro(genative) Diels-Alder reactions, which differ in dehydrogenation and D-A cyclization sequence. Reactions in which D-A cycloaddition is followed by dehydrogenation are useful methods for the synthesis of various aromatic compounds, whereas advancements in dehydro genative procedures with oxidants or catalysts prior to D-A cycloaddition offer yet further new routes to functionalized cycloadducts. Recent leading findings are highlighted and the current state of the art, scope, and limitations of these processes are discussed in this Minireview. PMID:26786814

  4. Aromatization of hydrocarbons by oxidative dehydrogenation catalyzed by the mixed addenda heteropoly acid H sub 5 PMo sub 10 V sub 2 O sub 40

    SciTech Connect

    Neumann, R. ); Lissle, M. )

    1989-09-15

    The mixed addenda heteropoly acid H{sub 5}PMo{sub 10}V{sub 2}O{sub 40} dissolved in 1,2-dichloroethane with tetraglyme, forming the (tetraglyme){sub 3}-H{sub 5}PMo{sub 10}V{sub 2}O{sub 40} complex, catalyzes the aromatization of cyclic dienes at moderate temperatures in the presence of molecular oxygen. Dehydrogenations of exocyclic dienes such as limonene show that dehydrogenation is preceded by isomerization to their endocyclic isomers. Aromatization takes place by successive one-electron transfers and proton abstractions from the organic substrate to the heteropoly acid the latter being reoxidized by dioxygen coupled with the formation of water.

  5. O2 -mediated dehydrogenative amination of phenols.

    PubMed

    Louillat-Habermeyer, Marie-Laure; Jin, Rongwei; Patureau, Frederic W

    2015-03-23

    A method was developed for the direct dehydrogenative construction of CN bonds between unprotected phenols and a series of cyclic anilines without resorting to any kind of metal activation of either substrate and without the use of halides. The resulting process relies on the exclusively organic activation of molecular oxygen and the subsequent oxidation of the aniline substrate. This allows the coupling of ubiquitous phenols, thus furnishing aminophenols through an atom-economical and most sustainable dehydrogenative amination method. This new reactivity, which relies on the intrinsic organic reactivity of cumene in what can be seen as a modified Hock activation process of oxygen, is expected to have a large impact on the formation of CN bonds in organic synthesis. PMID:25655504

  6. Dehydrogenative Diels-Alder reaction.

    PubMed

    Ozawa, Takuya; Kurahashi, Takuya; Matsubara, Seijiro

    2011-10-01

    The dehydrogenative cycloaddition of dieneynes, which possess a diene in the form of a styrene moiety and a dienophile in the form of an alkyne moiety, produces naphthalene derivatives when heated. It was found that a key requirement of this process is the presence of a silyl group attached to the alkyne moiety, which forces a dehydrogenation reaction to occur. PMID:21905638

  7. Selective Alkane Oxidation by Manganese Oxide: Site Isolation of MnOx Chains at the Surface of MnWO4 Nanorods.

    PubMed

    Li, Xuan; Lunkenbein, Thomas; Pfeifer, Verena; Jastak, Mateusz; Nielsen, Pia Kjaer; Girgsdies, Frank; Knop-Gericke, Axel; Rosowski, Frank; Schlögl, Robert; Trunschke, Annette

    2016-03-14

    The electronic and structural properties of vanadium-containing phases govern the formation of isolated active sites at the surface of these catalysts for selective alkane oxidation. This concept is not restricted to vanadium oxide. The deliberate use of hydrothermal techniques can turn the typical combustion catalyst manganese oxide into a selective catalyst for oxidative propane dehydrogenation. Nanostructured, crystalline MnWO4 serves as the support that stabilizes a defect-rich MnOx surface phase. Oxygen defects can be reversibly replenished and depleted at the reaction temperature. Terminating MnOx zigzag chains on the (010) crystal planes are suspected to bear structurally site-isolated oxygen defects that account for the unexpectedly good performance of the catalyst in propane activation. PMID:26913704

  8. Propane Vehicle Demonstration Grant Program

    SciTech Connect

    Jack Mallinger

    2004-08-27

    Project Description: Propane Vehicle Demonstration Grants The Propane Vehicle Demonstration Grants was established to demonstrate the benefits of new propane equipment. The US Department of Energy, the Propane Education & Research Council (PERC) and the Propane Vehicle Council (PVC) partnered in this program. The project impacted ten different states, 179 vehicles, and 15 new propane fueling facilities. Based on estimates provided, this project generated a minimum of 1,441,000 new gallons of propane sold for the vehicle market annually. Additionally, two new off-road engines were brought to the market. Projects originally funded under this project were the City of Portland, Colorado, Kansas City, Impco Technologies, Jasper Engines, Maricopa County, New Jersey State, Port of Houston, Salt Lake City Newspaper, Suburban Propane, Mutual Liquid Propane and Ted Johnson.

  9. Dual Nanoparticle/Substrate Control of Catalytic Dehydrogenation

    SciTech Connect

    Borisevich, Albina Y; Wang, Sanwu; Rashkeev, Sergey; Glazoff, Michael V; Pennycook, Stephen J; Pantelides, Sokrates T

    2007-01-01

    Saturated hydrocarbons, or alkanes (C{sub n}H{sub 2n+2}), are abundant in petroleum and can be converted to alkenes (C{sub n}H{sub 2n}) by dehydrogenation. Alkenes, also known as unsaturated hydrocarbons, are easy to polymerize and are the primary feedstock of the petrochemical industry, especially ethene (n=2) and propene (n = 3). Efficient catalytic dehydrogenation is therefore a major industrial objective. It has been found that oxidative catalytic dehydrogenation, that is, a process assisted by both a solid catalyst and a flow of oxygen gas, is most practical because of higher system longevity. Chromia/alumina catalytic systems have been widely adopted by industry. They have also been the subject of scientific studies seeking understanding that may help optimization of the process.

  10. Decarbonylation and dehydrogenation of carbohydrates

    DOEpatents

    Andrews, Mark A.; Klaeren, Stephen A.

    1991-01-01

    Carbohydrates, especially aldose or ketose sugars, including those whose carbonyl group is masked by hemi-acetal or hemi-ketal formation, are decarbonylated by heating the feed carbohydrate together with a transition metal complex in a suitable solvent. Also, primary alcohols, including sugar alditols are simultaneously dehydrogenated and decarbonylated by heating a mixture of rhodium and ruthenium complexes and the alcohol and optionally a hydrogen acceptor in an acceptable solvent. Such defarbonylation and/or dehydrogenation of sugars provides a convenient procedure for the synthesis of certain carbohydrates and may provide a means for the conversion of biomass into useful products.

  11. Study by electrical conductivity measurements of semiconductive and redox properties of M-doped NiO (M = Li, Mg, Al, Ga, Ti, Nb) catalysts for the oxidative dehydrogenation of ethane.

    PubMed

    Popescu, Ionel; Heracleous, Eleni; Skoufa, Zinovia; Lemonidou, Angeliki; Marcu, Ioan-Cezar

    2014-03-14

    Pure and M-doped nickel oxides with M = Li, Mg, Al, Ga, Ti, Nb, catalysts for the oxidative dehydrogenation of ethane into ethylene, were characterized by in situ electrical conductivity measurements. Their electrical conductivity was studied as a function of temperature and oxygen partial pressure and was followed with time during sequential exposures to air, an ethane-air mixture (reaction mixture) and pure ethane under conditions similar to those of catalysis. All the materials appeared to be p-type semiconductors under air with positive holes as the main charge carriers and their electrical conductivity decreased in the following order: Li-NiO > NiO > Mg-NiO > Nb-NiO > Ga-NiO > Al-NiO > Ti-NiO. All the catalysts remained p-type semiconductors in the reaction mixture at 400 °C. Correlations between the p-type semiconductivity and the catalytic properties have been evidenced. The reaction mechanism involves surface lattice O(-) species and can be assimilated to a Mars and van Krevelen mechanism. PMID:24477867

  12. Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on adsorbate diffusion and dehydrogenation at vanadium oxide substrate

    NASA Astrophysics Data System (ADS)

    Gruber, M.; Hermann, K.

    2013-05-01

    We discuss the details of important steps of the selective catalytic reduction (SCR) of NOx at model V2O5(010) substrate. First, diffusion processes at the substrate surface are considered where hydrogen and ammonium, NH4, are used as examples. Hydrogen diffusion, a prerequisite for water formation involving substrate oxygen, is described by diffusion paths between adjacent surface oxygen sites. Corresponding energy barriers are determined mainly by the flexibility and the amount of distortion of the oxygen atoms which participate in the O-H-O bridge formation at the transition state. Further, diffusion of sub-surface oxygen to fill surface oxygen vacancies of the V2O5(010) substrate has been considered and results in reactive surface sites which have not been discussed so far. NH4 diffusion at the V2O5(010) surface can be described as a combined tumbling and rotation process characterized by quite low diffusion barriers which make the adsorbate rather mobile. Finally, hydrogenation and dehydrogenation of different NHx species at the V2O5(010) substrate surface are studied where special emphasis is given to the influence of surface reduction simulated locally by oxygen vacancies. The results confirm experimental findings of the presence of both NH2 and NH4 species after ammonia adsorption at the V2O5(010) surface.

  13. Water co-catalyzed selective dehydrogenation of methanol to formaldehyde and hydrogen

    NASA Astrophysics Data System (ADS)

    Shan, Junjun; Lucci, Felicia R.; Liu, Jilei; El-Soda, Mostafa; Marcinkowski, Matthew D.; Allard, Lawrence F.; Sykes, E. Charles H.; Flytzani-Stephanopoulos, Maria

    2016-08-01

    The non-oxidative dehydrogenation of methanol to formaldehyde is considered a promising method to produce formaldehyde and clean hydrogen gas. Although Cu-based catalysts have an excellent catalytic activity in the oxidative dehydrogenation of methanol, metallic Cu is commonly believed to be unreactive for the dehydrogenation of methanol in the absence of oxygen adatoms or oxidized copper. Herein we show that metallic Cu can catalyze the dehydrogenation of methanol in the absence of oxygen adatoms by using water as a co-catalyst both under realistic reaction conditions using silica-supported PtCu nanoparticles in a flow reactor system at temperatures below 250 °C, and in ultra-high vacuum using model PtCu(111) catalysts. Adding small amounts of isolated Pt atoms into the Cu surface to form PtCu single atom alloys (SAAs) greatly enhances the dehydrogenation activity of Cu. Under the same reaction conditions, the yields of formaldehyde from PtCu SAA nanoparticles are more than one order of magnitude higher than on the Cu nanoparticles, indicating a significant promotional effect of individual, isolated Pt atoms. Moreover, this study also shows the unexpected role of water in the activation of methanol. Water, a catalyst for methanol dehydrogenation at low temperatures, becomes a reactant in the methanol steam reforming reactions only at higher temperatures over the same metal catalyst.

  14. Propane-d6 Heterogeneously Hyperpolarized by Parahydrogen

    PubMed Central

    2015-01-01

    Long-lived spin states of hyperpolarized propane-d6 gas were demonstrated following pairwise addition of parahydrogen gas to propene-d6 using heterogeneous parahydrogen-induced polarization (HET-PHIP). Hyperpolarized molecules were synthesized using Rh/TiO2 solid catalyst with 1.6 nm Rh nanoparticles. Hyperpolarized (PH ∼ 1%) propane-d6 was detected at high magnetic field (9.4 T) spectroscopically and by high-resolution 3D gradient-echo MRI (4.7 T) as the gas flowed through the radiofrequency coil with a spatial and temporal resolution of 0.5 × 0.5 × 0.5 mm3 and 17.7 s, respectively. Stopped-flow hyperpolarized propane-d6 gas was also detected at 0.0475 T with an observed nuclear spin polarization of PH ∼ 0.1% and a relatively long lifetime with T1,eff = 6.0 ± 0.3 s. Importantly, it was shown that the hyperpolarized protons of the deuterated product obtained via pairwise parahydrogen addition could be detected directly at low magnetic field. Importantly, the relatively long low-field T1,eff of HP propane-d6 gas is not susceptible to paramagnetic impurities as tested by exposure to ∼0.2 atm oxygen. This long lifetime and nontoxic nature of propane gas could be useful for bioimaging applications including potentially pulmonary low-field MRI. The feasibility of high-resolution low-field 2D gradient-echo MRI was demonstrated with 0.88 × 0.88 mm2 spatial and ∼0.7 s temporal resolution, respectively, at 0.0475 T. PMID:25506406

  15. Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling

    NASA Astrophysics Data System (ADS)

    Bučko, Tomáš; Benco, Lubomir; Dubay, Orest; Dellago, Christoph; Hafner, Jürgen

    2009-12-01

    The dehydrogenation of propane over acidic chabazite has been studied using ab initio density-functional simulations in combination with static transition-state searches and dynamic transition path sampling (TPS) methods at elevated temperatures. The acidic zeolite has been modeled both using a small cluster and a large periodic model consisting of two unit cells, the TPS simulations allow to account for the effect of temperature and entropy. In agreement with experimental observations we find propene as the dominant reaction product and that the barrier for the dehydrogenation of a methyl group is higher than that for a methylene group. However, whereas all studies based on small cluster models (including the present one) conclude that the reaction proceeds via the formation of an alkoxy intermediate, our TPS studies based on a large periodic model lead to the conclusion that propene formation occurs via the formation of various forms of propyl cations stabilized by entropy, while the formation of an alkoxy species is a relatively rare event. It was observed only in 15% of the reactive trajectories for methyl dehydrogenation and even in only 8% of the methylene dehydrogenation reactions. Our studies demonstrate the importance of entropic effects and the need to account for the structure and flexibility of the zeolitic framework by using large periodic models.

  16. Selective and Stable Ethylbenzene Dehydrogenation to Styrene over Nanodiamonds under Oxygen-lean Conditions.

    PubMed

    Diao, Jiangyong; Feng, Zhenbao; Huang, Rui; Liu, Hongyang; Hamid, Sharifah Bee Abd; Su, Dang Sheng

    2016-04-01

    For the first time, significant improvement of the catalytic performance of nanodiamonds was achieved for the dehydrogenation of ethylbenzene to styrene under oxygen-lean conditions. We demonstrated that the combination of direct dehydrogenation and oxidative dehydrogenation indeed occurred on the nanodiamond surface throughout the reaction system. It was found that the active sp(2)-sp(3) hybridized nanostructure was well maintained after the long-term test and the active ketonic carbonyl groups could be generated in situ. A high reactivity with 40% ethylbenzene conversion and 92% styrene selectivity was obtained over the nanodiamond catalyst under oxygen-lean conditions even after a 240 h test, demonstrating the potential of this procedure for application as a promising industrial process for the ethylbenzene dehydrogenation to styrene without steam protection. PMID:26871428

  17. Catalysts for Dehydrogenation of ammonia boranes

    SciTech Connect

    Heinekey, Dennis M.

    2014-12-19

    Several effective homogeneous catalysts for the dehydrogenation of amine boranes have been developed. The best catalyst uses an iridium complex, and is capable of dehydrogenating H3NBH3 (AB) and CH3NH2BH3 (MeAB) at comparable rates. Thermodynamic measurements using this catalyst demonstrate that the dehydrogenation of AB and MeAB is substantially exothermic, which has important implications for regeneration.

  18. Beneficial effect of propane sultone and tris(trimethylsilyl) borate as electrolyte additives on the cycling stability of the lithium rich nickel manganese cobalt (NMC) oxide

    NASA Astrophysics Data System (ADS)

    Birrozzi, Agnese; Laszczynski, Nina; Hekmatfar, Maral; von Zamory, Jan; Giffin, Guinevere A.; Passerini, Stefano

    2016-09-01

    This study reports the investigation of several compounds as electrolyte additives for Li[Li0.2Mn0.56 Ni0.16 Co0.08]O2 (a.k.a lithium rich NMC) cathode material. Among the compounds investigated via electrochemical and ex-situ analytical techniques, i.e. XRD, XPS and RAMAN spectroscopy, only 1,3-propane sultone and tris(trimethylsilyl) borate show a beneficial effect on the capacity retention and coulombic efficiency of the layered cathode. The results suggest that the improved capacity retention of the cells containing the two above-mentioned additives mainly originates from their participation in the formation of the cathode passive layer, which prevents the dissolution of the metals from the cathode material. Additionally, the borate additive reduces the lithium consumption upon the passive layer formation thus leaving a higher amount of lithium available in the electrolyte. Graphite/Li[Li0.2Mn0.56 Ni0.16 Co0.08]O2 cells containing the borate additive in the electrolyte showed 85% capacity retention after 485 cycles, confirming the feasibility of its employment for practical applications.

  19. Position-specific and clumped stable isotope studies: comparison of the Urey and path-integral approaches for carbon dioxide, nitrous oxide, methane, and propane.

    PubMed

    Webb, Michael A; Miller, Thomas F

    2014-01-16

    We combine path-integral Monte Carlo methods with high-quality potential energy surfaces to compute equilibrium isotope effects in a variety of systems relevant to 'clumped' isotope analysis and isotope geochemistry, including CO2, N2O, methane, and propane. Through a systematic study of heavy-atom isotope-exchange reactions, we quantify and analyze errors that arise in the widely used Urey model for predicting equilibrium constants of isotope-exchange reactions using reduced partition function ratios. These results illustrate that the Urey model relies on a nontrivial cancellation of errors that can shift the apparent equilibrium temperature by as much as 35 K for a given distribution of isotopologues. The calculations reported here provide the same level of precision as the best existing analytical instrumentation, resolving the relative enrichment of certain isotopologues to as little as 0.01‰. These findings demonstrate path-integral methods to be a rigorous and viable alternative to more approximate methods for heavy-atom geochemical applications. PMID:24372450

  20. Dehydrogenation of benzene on Pt(111) surface

    NASA Astrophysics Data System (ADS)

    Gao, W.; Zheng, W. T.; Jiang, Q.

    2008-10-01

    The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

  1. Dehydration, Dehydrogenation, and Condensation of Alcohols on Supported Oxide Catalysts Based on Cyclic (WO3)3 and (MoO3)3 Clusters

    SciTech Connect

    Rousseau, Roger J.; Dixon, David A.; Kay, Bruce D.; Dohnalek, Zdenek

    2014-01-01

    Supported early transition metal oxides have important applications in numerous catalytic reactions. In this article we review preparation and activity of well-defined model WO3 and MoO3 catalysts prepared via deposition of cyclic gas-phase (WO3)3 and (MoO3)3 clusters generated by sublimation of WO3 and MoO3 powders. Conversion of small aliphatic alcohols to alkenes, aldehydes/ketons, and ethers is employed to probe the structure-activity relationships on model WO3 and MoO3 catalysts ranging from unsupported (WO3)3 and (MoO3)3 clusters embedded in alcohol matrices, to (WO3)3 clusters supported on surfaces of other oxides, and epitaxial and nanoporous WO3 films. Detailed theoretical calculations reveal the underlying reaction mechanisms and provide insight into the origin of the differences in the WO3 and MoO3 reactivity. For the range of interrogated (WO3)3 they further shed light into the role structure and binding of (WO3)3 clusters with the support play in determining their catalytic activity.

  2. Recent advances in copper-catalyzed dehydrogenative functionalization via a single electron transfer (SET) process.

    PubMed

    Zhang, Chun; Tang, Conghui; Jiao, Ning

    2012-05-01

    Copper salts have been developed as versatile catalysts for oxidative coupling reactions in organic synthesis. During these processes, Cu-catalysts are often proposed to serve as a one-electron oxidant to promote the single-electron transfer process. Recently, the transition-metal catalyzed direct dehydrogenative transformation has attracted considerable attention. This tutorial review summarizes the recent advances in the copper-catalyzed dehydrogenative functionalization via a single electron transfer (SET) process achieving C-C, C-N, C-O, C-halogen atoms, C-P, and N-N bond formation. PMID:22349590

  3. CO2 emission free co-generation of energy and ethylene in hydrocarbon SOFC reactors with a dehydrogenation anode.

    PubMed

    Fu, Xian-Zhu; Lin, Jie-Yuan; Xu, Shihong; Luo, Jing-Li; Chuang, Karl T; Sanger, Alan R; Krzywicki, Andrzej

    2011-11-21

    A dehydrogenation anode is reported for hydrocarbon proton conducting solid oxide fuel cells (SOFCs). A Cu-Cr(2)O(3) nanocomposite is obtained from CuCrO(2) nanoparticles as an inexpensive, efficient, carbon deposition and sintering tolerant anode catalyst. A SOFC reactor is fabricated using a Cu-Cr(2)O(3) composite as a dehydrogenation anode and a doped barium cerate as a proton conducting electrolyte. The protonic membrane SOFC reactor can selectively convert ethane to valuable ethylene, and electricity is simultaneously generated in the electrochemical oxidative dehydrogenation process. While there are no CO(2) emissions, traces of CO are present in the anode exhaust when the SOFC reactor is operated at over 700 °C. A mechanism is proposed for ethane electro-catalytic dehydrogenation over the Cu-Cr(2)O(3) catalyst. The SOFC reactor also has good stability for co-generation of electricity and ethylene at 700 °C. PMID:21984357

  4. Nanoscale platinum and iron-cobalt catalysts deposited in microchannel microreactors for use in hydrogenation and dehydrogenation of cyclohexene, selective oxidation of carbon monoxide and Fischer-Tropsch process to higher alkanes

    NASA Astrophysics Data System (ADS)

    Zhao, Shihuai

    reactions of enormous commercial potential: Fischer-Tropsch (F-T) synthesis, and preferential oxidation of CO in fuel cell. An over 50% conversion of CO and 78% selectivity to propane in F-T synthesis has been achieved. Meanwhile, a 70% conversion of CO and 80% selectivity to CO2 in preferential oxidation is reached in the fuel cell feed gas reaction. Statistical modeling studies were done using a Central Composite Design (CCD) to achieve the optimal condition (temperature 158°C, CO: O2 ratio 1.77 and total flow rate 0.207 sccm) for preferential oxidation of CO in fuel cells.

  5. Photocatalytic oxidation of methane over silver decorated zinc oxide nanocatalysts.

    PubMed

    Chen, Xuxing; Li, Yunpeng; Pan, Xiaoyang; Cortie, David; Huang, Xintang; Yi, Zhiguo

    2016-01-01

    The search for active catalysts that efficiently oxidize methane under ambient conditions remains a challenging task for both C1 utilization and atmospheric cleansing. Here, we show that when the particle size of zinc oxide is reduced down to the nanoscale, it exhibits high activity for methane oxidation under simulated sunlight illumination, and nano silver decoration further enhances the photo-activity via the surface plasmon resonance. The high quantum yield of 8% at wavelengths <400 nm and over 0.1% at wavelengths ∼470 nm achieved on the silver decorated zinc oxide nanostructures shows great promise for atmospheric methane oxidation. Moreover, the nano-particulate composites can efficiently photo-oxidize other small molecular hydrocarbons such as ethane, propane and ethylene, and in particular, can dehydrogenize methane to generate ethane, ethylene and so on. On the basis of the experimental results, a two-step photocatalytic reaction process is suggested to account for the methane photo-oxidation. PMID:27435112

  6. Photocatalytic oxidation of methane over silver decorated zinc oxide nanocatalysts

    PubMed Central

    Chen, Xuxing; Li, Yunpeng; Pan, Xiaoyang; Cortie, David; Huang, Xintang; Yi, Zhiguo

    2016-01-01

    The search for active catalysts that efficiently oxidize methane under ambient conditions remains a challenging task for both C1 utilization and atmospheric cleansing. Here, we show that when the particle size of zinc oxide is reduced down to the nanoscale, it exhibits high activity for methane oxidation under simulated sunlight illumination, and nano silver decoration further enhances the photo-activity via the surface plasmon resonance. The high quantum yield of 8% at wavelengths <400 nm and over 0.1% at wavelengths ∼470 nm achieved on the silver decorated zinc oxide nanostructures shows great promise for atmospheric methane oxidation. Moreover, the nano-particulate composites can efficiently photo-oxidize other small molecular hydrocarbons such as ethane, propane and ethylene, and in particular, can dehydrogenize methane to generate ethane, ethylene and so on. On the basis of the experimental results, a two-step photocatalytic reaction process is suggested to account for the methane photo-oxidation. PMID:27435112

  7. Costs Associated With Propane Vehicle Fueling Infrastructure

    SciTech Connect

    Smith, M.; Gonzales, J.

    2014-08-01

    This document is designed to help fleets understand the cost factors associated with propane vehicle fueling infrastructure. It provides an overview of the equipment and processes necessary to develop a propane fueling station and offers estimated cost ranges.

  8. Costs Associated With Propane Vehicle Fueling Infrastructure

    SciTech Connect

    Smith, M.; Gonzales, J.

    2014-08-05

    This document is designed to help fleets understand the cost factors associated with propane vehicle fueling infrastructure. It provides an overview of the equipment and processes necessary to develop a propane fueling station and offers estimated cost ranges.

  9. 75 FR 14131 - Effect on Propane Consumers of the Propane Education and Research Council's Operations, Market...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-24

    ... comment on whether the operation of the Propane Education and Research Council (PERC), in conjunction with... International Trade Administration Effect on Propane Consumers of the Propane Education and Research Council's... information to fulfill requirements under the Propane Education and Research Act of 1996 that established...

  10. Supported organoiridium catalysts for alkane dehydrogenation

    DOEpatents

    Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

    2013-09-03

    Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

  11. Dehydrogenation of Formic Acid by Heterogeneous Catalysts.

    PubMed

    Li, Jun; Zhu, Qi-Long; Xu, Qiang

    2015-01-01

    Formic acid has recently been considered as one of the most promising hydrogen storage materials. The basic concept is briefly discussed and the research progress is detailledly reviewed on the dehydrogenation of aqueous formic acid by heterogeneous catalysts. PMID:26507481

  12. Subnanometer-sized Pt/Sn alloy cluster catalysts for the dehydrogenation of linear alkanes.

    PubMed

    Hauser, Andreas W; Gomes, Joseph; Bajdich, Michal; Head-Gordon, Martin; Bell, Alexis T

    2013-12-21

    The reaction pathways for the dehydrogenation of ethane, propane, and butane, over Pt are analyzed using density functional theory (DFT). Pt nanoparticles are represented by a tetrahedral Pt4 cluster. The objectives of this work were to establish which step is rate limiting and which one controls the selectivity for forming alkenes as opposed to causing further dehydrogenation of adsorbed alkenes to produce precursors responsible for catalyst deactivation due to coking. Further objectives of this work are to identify the role of adsorbed hydrogen, derived from H2 fed together with the alkane, on the reaction pathway, and the role of replacing one of the four Pt atoms by a Sn atom. A comparison of Gibbs free energies shows that in all cases the rate-determining step is cleavage of a C-H bond upon alkane adsorption. The selectivity to alkene formation versus precursors to coking is dictated by the relative magnitudes of the activation energies for alkene desorption and dehydrogenation of the adsorbed alkene. The presence of an adsorbed H atom on the cluster facilitates alkene desorption relative to dehydrogenation of the adsorbed alkene. Substitution of a Sn atom in the cluster to produce a Pt3Sn cluster leads to a downward shift of the potential energy surface for the reaction and causes an increase of the activity of the catalyst as suggested by recent experiments due to the lower net activation barrier for the rate limiting step. However, the introduction of Sn does not alter the relative activation barriers for gas-phase alkene formation versus loss of hydrogen from the adsorbed alkene, the process leading to the formation of coke precursors. PMID:24196250

  13. Dehydrogenative α-oxygenation of ethers with an iron catalyst.

    PubMed

    Gonzalez-de-Castro, Angela; Robertson, Craig M; Xiao, Jianliang

    2014-06-11

    Selective α-oxidation of ethers under aerobic conditions is a long-pursued transformation; however, a green and efficient catalytic version of this reaction remains challenging. Herein, we report a new family of iron catalysts capable of promoting chemoselective α-oxidation of a range of ethers with excellent mass balance and high turnover numbers under 1 atm of O2 with no need for any additives. Unlike metalloenzymes and related biomimetics, the catalyst produces H2 as the only byproduct. Mechanistic investigations provide evidence for an unexpected two-step reaction pathway, which involves dehydrogenative incorporation of O2 into the ether to give a peroxobisether intermediate followed by cleavage of the peroxy bond to form two ester molecules, releasing stoichiometric H2 gas in each step. The operational simplicity and environmental friendliness of this methodology affords a useful alternative for performing oxidation, while the unique ability of the catalyst in oxygenating a substrate via dehydrogenation points to a new direction for understanding metalloenzymes and designing new biomimetic catalysts. PMID:24835531

  14. Effect of hydrogen injection stability and emissions of an experimental premixed prevaporized propane burner

    NASA Technical Reports Server (NTRS)

    Anderson, D. N.

    1975-01-01

    Hydrogen in quantities up to 5 percent by weight of the total fuel flow was injected into a premixed propane burner. The hydrogen was either premixed with the propane and air upstream of the burner or introduced as a torch at the flameholder. Emissions of total nitrogen oxides, carbon monoxide, and unburned hydrocarbon are reported as are combustion efficiencies and lean blowout limits. To maintain at least 99 percent combustion efficiency at a 700 K inlet mixture temperature with no hydrogen added, it was necessary to burn with a propane equivalence ratio of 0.525. When 4 percent hydrogen was premixed with the propane and air, a combustion efficiency greater than 99 percent was recorded at a propane equivalence ratio of 0.425. The total nitrogen oxides (NOx) emissions corresponding to these two conditions were 0.8 g NO2/kg equivalent propane and 0.44 g NO2/kg equivalent propane, respectively. The hydrogen torch did not reduce NOx emissions.

  15. In situ Raman spectroscopy study of metal-enhanced hydrogenation and dehydrogenation of VO2.

    PubMed

    Wu, Hao; Fu, Qiang; Bao, Xinhe

    2016-11-01

    Vanadium dioxide (VO2) has a phase transition from insulator to metal at 340 K, and this transition can be strongly modified by hydrogenation. In this work, two dimensional (2D) VO2 sheets have been grown on Si(1 1 1) surfaces through chemical vapor deposition, and metal (Au, Pt) thin films were deposited on VO2 surfaces by sputtering. The hydrogenation and dehydrogenation of VO2 and metal-decorated VO2 structures in H2 and in air were in situ studied by Raman. We found that hydrogenation and dehydrogenation temperatures have been significantly decreased with the VO2 surface decorated by Au and Pt. The enhanced hydrogenation and dehydrogenation reactions can be attributed to catalytic dissociation of H2 and O2 molecules on metal surfaces and subsequent spillover of dissociated H and O atoms to the oxide surfaces. PMID:27603090

  16. Propane Market Model documentation report

    SciTech Connect

    Not Available

    1993-12-01

    The purpose of this report is to define the objectives of the Propane Market Model (PMM), describe its basic approach, and to provide details on model functions. This report is intended as a reference document for model analysts, users, and the general public. Documentation of the model is in accordance with EIA`s legal obligation to provide adequate documentation in support of its models. The PMM performs a short-term (6- to 9-months) forecast of demand and price for consumer-grad propane in the national US market; it also calculates the end-of-month stock level during the term of the forecast. Another part of the model allows for short-term demand forecasts for certain individual Petroleum Administration for Defense (PAD) districts. The model is used to analyze market behavior assumptions or shocks and to determine the effect on market price, demand, and stock level.

  17. Marine microbes rapidly adapt to consume ethane, propane, and butane within the dissolved hydrocarbon plume of a natural seep

    NASA Astrophysics Data System (ADS)

    Mendes, Stephanie D.; Redmond, Molly C.; Voigritter, Karl; Perez, Christian; Scarlett, Rachel; Valentine, David L.

    2015-03-01

    Simple hydrocarbon gases containing two to four carbons (ethane, propane, and butane) are among the most abundant compounds present in petroleum reservoirs, and are introduced into the ocean through natural seepage and industrial discharge. Yet little is known about the bacterial consumption of these compounds in ocean waters. To assess the timing by which microbes metabolize these gases, we conducted a three-phase study that tested and applied a radiotracer-based method to quantify the oxidation rates of ethane, propane, and butane in fresh seawater samples. Phase 1 involved the synthesis of tritiated ethane, propane, and butane using Grignard reagents and tritiated water. Phase 2 was a systematic assessment of experimental conditions, wherein the indigenous microbial community was found to rapidly oxidize ethane, propane, and butane. Phase 3 was the application of this tritium method near the Coal Oil Point seeps, offshore California. Spatial and temporal patterns of ethane, propane, and butane oxidation down current from the hydrocarbon seeps demonstrated that >99% of these gases are metabolized within 1.3 days following initial exposure. The oxidation of ethane outpaced oxidation of propane and butane with patterns indicating the microbial community responded to these gases by rapid adaptation or growth. Methane oxidation responded the slowest in plume waters. Estimates based on the observed metabolic rates and carbon mass balance suggest that ethane, propane, and butane-consuming microorganisms may transiently account for a majority of the total microbial community in these impacted waters.

  18. Dehydrogenation of liquid fuel in microchannel catalytic reactor

    DOEpatents

    Toseland, Bernard Allen; Pez, Guido Peter; Puri, Pushpinder Singh

    2009-02-03

    The present invention is an improved process for the storage and delivery of hydrogen by the reversible hydrogenation/dehydrogenation of an organic compound wherein the organic compound is initially in its hydrogenated state. The improvement in the route to generating hydrogen is in the dehydrogenation step and recovery of the dehydrogenated organic compound resides in the following steps: introducing a hydrogenated organic compound to a microchannel reactor incorporating a dehydrogenation catalyst; effecting dehydrogenation of said hydrogenated organic compound under conditions whereby said hydrogenated organic compound is present as a liquid phase; generating a reaction product comprised of a liquid phase dehydrogenated organic compound and gaseous hydrogen; separating the liquid phase dehydrogenated organic compound from gaseous hydrogen; and, recovering the hydrogen and liquid phase dehydrogenated organic compound.

  19. Dehydrogenation of liquid fuel in microchannel catalytic reactor

    SciTech Connect

    Toseland, Bernard Allen; Pez, Guido Peter; Puri, Pushpinder Singh

    2010-08-03

    The present invention is an improved process for the storage and delivery of hydrogen by the reversible hydrogenation/dehydrogenation of an organic compound wherein the organic compound is initially in its hydrogenated state. The improvement in the route to generating hydrogen is in the dehydrogenation step and recovery of the dehydrogenated organic compound resides in the following steps: introducing a hydrogenated organic compound to a microchannel reactor incorporating a dehydrogenation catalyst; effecting dehydrogenation of said hydrogenated organic compound under conditions whereby said hydrogenated organic compound is present as a liquid phase; generating a reaction product comprised of a liquid phase dehydrogenated organic compound and gaseous hydrogen; separating the liquid phase dehydrogenated organic compound from gaseous hydrogen; and, recovering the hydrogen and liquid phase dehydrogenated organic compound.

  20. Better Catalysts through Microscopy: Mesoscale M1/M2 Intergrowth in Molybdenum–Vanadium Based Complex Oxide Catalysts for Propane Ammoxidation

    DOE PAGESBeta

    He, Qian; Woo, Jungwon; Belianinov, Alexei; Guliants, Vadim V.; Borisevich, Albina Y.

    2015-03-06

    Catalysis research has transformed from the predominantly empirical field to one where it is possible to control the catalytic properties via characterization and modification of the atomic-scale active centers. Many phenomena in catalysis, such as synergistic effect, however, transcend the atomic scale and also require the knowledge and control of the mesoscale structure of the specimen to harness. Our paper, we use our discovery of atomic-scale epitaxial interfaces in molybdenum vanadium based complex oxide catalysts systems (i.e., MoVMO, M = Ta, Te, Sb, Nb, etc.) to achieve control of the mesoscale structure of this complex mixture of very different activemore » phases. We can now achieve true epitaxial intergrowth between the catalytically critical M1 and M2 phases in the system that are hypothesized to have synergistic interactions, and demonstrate that the resulting catalyst has improved selectivity in the initial studies. Finally, we highlight the crucial role atomic scale characterization and mesoscale structure control play in uncovering the complex underpinnings of the synergistic effect in catalysis.« less

  1. Better Catalysts through Microscopy: Mesoscale M1/M2 Intergrowth in Molybdenum–Vanadium Based Complex Oxide Catalysts for Propane Ammoxidation

    SciTech Connect

    He, Qian; Woo, Jungwon; Belianinov, Alexei; Guliants, Vadim V.; Borisevich, Albina Y.

    2015-03-06

    Catalysis research has transformed from the predominantly empirical field to one where it is possible to control the catalytic properties via characterization and modification of the atomic-scale active centers. Many phenomena in catalysis, such as synergistic effect, however, transcend the atomic scale and also require the knowledge and control of the mesoscale structure of the specimen to harness. Our paper, we use our discovery of atomic-scale epitaxial interfaces in molybdenum vanadium based complex oxide catalysts systems (i.e., MoVMO, M = Ta, Te, Sb, Nb, etc.) to achieve control of the mesoscale structure of this complex mixture of very different active phases. We can now achieve true epitaxial intergrowth between the catalytically critical M1 and M2 phases in the system that are hypothesized to have synergistic interactions, and demonstrate that the resulting catalyst has improved selectivity in the initial studies. Finally, we highlight the crucial role atomic scale characterization and mesoscale structure control play in uncovering the complex underpinnings of the synergistic effect in catalysis.

  2. Influence of Ionic Liquids on an Iron(III) Catalyzed Three-Component Coupling/Hydroarylation/Dehydrogenation Tandem Reaction.

    PubMed

    Muntzeck, Maren; Wilhelm, René

    2016-01-01

    A three-component oxidative dehydrogenation tandem reaction via the coupling and hydroarylation of benzaldehyde, aniline and phenylacetylene to a quinoline derivate was catalyzed by an iron-containing ionic liquid. The reaction was air mediated and could be performed under neat conditions. The iron(III) of the ionic liquid was the oxidizing species. PMID:27258264

  3. Influence of Ionic Liquids on an Iron(III) Catalyzed Three-Component Coupling/Hydroarylation/Dehydrogenation Tandem Reaction

    PubMed Central

    Muntzeck, Maren; Wilhelm, René

    2016-01-01

    A three-component oxidative dehydrogenation tandem reaction via the coupling and hydroarylation of benzaldehyde, aniline and phenylacetylene to a quinoline derivate was catalyzed by an iron-containing ionic liquid. The reaction was air mediated and could be performed under neat conditions. The iron(III) of the ionic liquid was the oxidizing species. PMID:27258264

  4. Oxidative conversion of C1-C3 alkanes by vanadium oxide catalysts. DFT results and their accuracy

    NASA Astrophysics Data System (ADS)

    Rozanska, Xavier; Sauer, Joachim

    Elementary steps in the oxidative conversion of methane, ethane, and propane by supported vanadium oxide species are studied by density functional theory, specifically B3LYP. Two models are adopted, namely O dbond V(OH)3 and O dbond VSi7O12H7, which yield similar energy profiles. The initial and rate-determining step is hydrogen abstraction. Within the C1-C3 series, energy barriers and reaction energies follow the same trend as the C bond H bond strength in the different alkanes. For methane, only methanol formation is possible whereas for ethane and propane, oxidative dehydrogenation yields the corresponding alkenes. Single point CCSD(T)/TZVP calculations are used to assess the B3LYP error. For the barrier of the initial hydrogen abstraction the B3LYP error is larger than usual, -40 to -60 kJ/mol. With the non-hybrid BP86 and PBE functionals even larger errors occur and the potential energy surface is qualitatively different.

  5. Elucidating the mechanism and active site of the cyclohexanol dehydrogenation on copper-based catalysts: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Wang, Ziyun; Liu, Xinyi; Rooney, D. W.; Hu, P.

    2015-10-01

    The dehydrogenation of cyclohexanol to cyclohexanone is very important in the manufacture of nylon. Copper-based catalysts are the most popular catalysts for this reaction, and on these catalysts the reaction mechanism and active site are in debate. In order to elucidate the mechanism and active site of the cyclohexanol dehydrogenation on copper-based catalysts, density functional theory with dispersion corrections were performed on up to six facets of copper in two different oxidation states: monovalent copper and metallic copper. By calculating the surface energies of these facets, Cu(111) and Cu2O(111) were found to be the most stable facets for metallic copper and for monovalent copper, respectively. On these two facets, all the possible elementary steps in the dehydrogenation pathway of cyclohexanol were calculated, including the adsorption, dehydrogenation, hydrogen coupling and desorption. Two different reaction pathways for dehydrogenation were considered on both surfaces. It was revealed that the dehydrogenation mechanisms are different on these two surfaces: on Cu(111) the hydrogen belonging to the hydroxyl is removed first, then the hydrogen belonging to the carbon is subtracted, while on Cu2O(111) the hydrogen belonging to the carbon is removed followed by the subtraction of the hydrogen in the hydroxyl group. Furthermore, by comparing the energy profiles of these two surfaces, Cu2O(111) was found to be more active for cyclohexanol dehydrogenation than Cu(111). In addition, we found that the coordinatively unsaturated copper sites on Cu2O(111) are the reaction sites for all the steps. Therefore, the coordinatively unsaturated copper site on Cu2O(111) is likely to be the active site for cyclohexanol dehydrogenation on the copper-based catalysts.

  6. Molecular Complexity via C–H Activation: A Dehydrogenative Diels-Alder Reaction

    PubMed Central

    Stang, Erik M.; White, M. Christina

    2011-01-01

    Traditionally, C–H oxidation reactions install oxidized functionality onto a preformed molecular skeleton, resulting in a local molecular change. The use of C–H activation chemistry to construct complex molecular scaffolds is a new area with tremendous potential in synthesis. We report a Pd(II)/bis-sulfoxide catalyzed dehydrogenative Diels-Alder reaction that converts simple terminal olefins into complex cycloadducts in a single operation. PMID:21842902

  7. Base metal dehydrogenation of amine-boranes

    DOEpatents

    Blacquiere, Johanna Marie; Keaton, Richard Jeffrey; Baker, Ralph Thomas

    2009-06-09

    A method of dehydrogenating an amine-borane having the formula R.sup.1H.sub.2N--BH.sub.2R.sup.2 using base metal catalyst. The method generates hydrogen and produces at least one of a [R.sup.1HN--BHR.sup.2].sub.m oligomer and a [R.sup.1N--BR.sup.2].sub.n oligomer. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources, such as, but not limited to, fuel cells.

  8. Partial oxidation catalyst

    DOEpatents

    Krumpelt, Michael; Ahmed, Shabbir; Kumar, Romesh; Doshi, Rajiv

    2000-01-01

    A two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion. The dehydrogenation portion is a group VIII metal and the oxide-ion conducting portion is selected from a ceramic oxide crystallizing in the fluorite or perovskite structure. There is also disclosed a method of forming a hydrogen rich gas from a source of hydrocarbon fuel in which the hydrocarbon fuel contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion at a temperature not less than about 400.degree. C. for a time sufficient to generate the hydrogen rich gas while maintaining CO content less than about 5 volume percent. There is also disclosed a method of forming partially oxidized hydrocarbons from ethanes in which ethane gas contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion for a time and at a temperature sufficient to form an oxide.

  9. Acceptorless dehydrogenation of small molecules through cooperative base metal catalysis

    PubMed Central

    West, Julian G.; Huang, David; Sorensen, Erik J.

    2015-01-01

    The dehydrogenation of unactivated alkanes is an important transformation both in industrial and biological systems. Recent efforts towards this reaction have revolved around high temperature, organometallic C–H activation by noble metal catalysts that produce alkenes and hydrogen gas as the sole products. Conversely, natural desaturase systems proceed through stepwise hydrogen atom transfer at physiological temperature; however, these transformations require a terminal oxidant. Here we show combining tetra-n-butylammonium decatungstate (TBADT) and cobaloxime pyridine chloride (COPC) can catalytically dehydrogenate unactivated alkanes and alcohols under near-UV irradiation at room temperature with hydrogen as the sole by-product. This noble metal-free process follows a nature-inspired pathway of high- and low-energy hydrogen atom abstractions. The hydrogen evolution ability of cobaloximes is leveraged to render the system catalytic, with cooperative turnover numbers up to 48 and yields up to 83%. Our results demonstrate how cooperative base metal catalysis can achieve transformations previously restricted to precious metal catalysts. PMID:26656087

  10. Acceptorless dehydrogenation of small molecules through cooperative base metal catalysis.

    PubMed

    West, Julian G; Huang, David; Sorensen, Erik J

    2015-01-01

    The dehydrogenation of unactivated alkanes is an important transformation both in industrial and biological systems. Recent efforts towards this reaction have revolved around high temperature, organometallic C-H activation by noble metal catalysts that produce alkenes and hydrogen gas as the sole products. Conversely, natural desaturase systems proceed through stepwise hydrogen atom transfer at physiological temperature; however, these transformations require a terminal oxidant. Here we show combining tetra-n-butylammonium decatungstate (TBADT) and cobaloxime pyridine chloride (COPC) can catalytically dehydrogenate unactivated alkanes and alcohols under near-UV irradiation at room temperature with hydrogen as the sole by-product. This noble metal-free process follows a nature-inspired pathway of high- and low-energy hydrogen atom abstractions. The hydrogen evolution ability of cobaloximes is leveraged to render the system catalytic, with cooperative turnover numbers up to 48 and yields up to 83%. Our results demonstrate how cooperative base metal catalysis can achieve transformations previously restricted to precious metal catalysts. PMID:26656087

  11. Effect of Porphyrin Ligands on the Regioselective Dehydrogenation versus Epoxidation of Olefins by Oxoiron(IV) Mimics of Cytochrome P450

    NASA Astrophysics Data System (ADS)

    Kumar, Devesh; Tahsini, Laleh; Visser, Sam P. De; Kang, Hye Yeon; Kim, Soo Jeong; Nam, Wonwoo

    2009-08-01

    The cytochromes P450 are versatile enzymes involved in various catalytic oxidation reactions, such as hydroxylation, epoxidation and dehydrogenation. In this work, we present combined experimental and theoretical studies on the change of regioselectivity in cyclohexadiene oxidation (i.e., epoxidation vs dehydrogenation) by oxoiron(IV) porphyrin complexes bearing different porphyrin ligands. Our experimental results show that meso-substitution of the porphyrin ring with electron-withdrawing substituents leads to a regioselectivity switch from dehydrogenation to epoxidation, affording the formation of epoxide as a major product. In contrast, electron-rich iron porphyrins are shown to produce benzene resulting from the dehydrogenation of cyclohexadiene. Density functional theory (DFT) calculations on the regioselectivity switch of epoxidation vs dehydrogenation have been performed using three oxoiron(IV) porphyrin oxidants with hydrogen atoms, phenyl groups, and pentachlorophenyl (ArCl5) groups on the meso-position. The DFT studies show that the epoxidation reaction by the latter catalyst is stabilized because of favorable interactions of the substrate with halogen atoms of the meso-ligand as well as with pyrrole nitrogen atoms of the porphyrin macrocycle. Hydrogen abstraction transition states, in contrast, have a substrate-binding orientation further away from the porphyrin pyrrole nitrogens, and they are much less stabilized. Finally, the regioselectivity of dehydrogenation versus hydroxylation is rationalized using thermodynamic cycles.

  12. Thermodynamic properties and ideal-gas enthalpies of formation for 2-aminoisobutyric acid (2-methylalanine), acetic acid, (Z)-5-ethylidene-2-norbornene, mesityl oxide (4-methyl-3-penten-2-one), 4-methylpent-1-ene, 2,2{prime}-bis(phenylthio)propane, and glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane)

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Cowell, A.B.; Knipmeyer, S.E.; Nguyen, A.

    1997-11-01

    The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Ideal-gas enthalpies of formation of acetic acid, (Z)-5-ethylidene-2-norbornene, mesityl oxide (4-methyl-3-penten-2-one), 4-methylpent-1-ene, glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane), and 2,2{prime}-bis(phenylthio)propane are reported. An enthalpy of formation of 2-aminoisobutyric acid (2-methylalanine) in the crystalline phase was determined. Using a literature value for the enthalpy of sublimation of 2-aminoisobutyric acid, a value for the ideal-gas enthalpy of formation was derived. An enthalpy of fusion was determined for 2,2{prime}-bis(phenylthio)propane. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for all the compounds except acetic acid. For mesityl oxide and 4-methylpent-1-ene, critical temperatures and critical densities were determined from the DSC results and corresponding critical pressures derived from the fitting procedures. Group-additivity parameters and ring strain energies useful in the application of group-contribution correlations were derived.

  13. Copper(II)-catalyzed indolizines formation followed by dehydrogenative functionalization cascade to synthesize 1-bromoindolizines.

    PubMed

    Wang, Fuyao; Shen, Yongmiao; Hu, Huayou; Wang, Xiangshan; Wu, Hui; Liu, Yun

    2014-10-17

    A one-pot, three-component cascade reaction between pyridine, α-acylmethylbromide, and maleic anhydride leading to direct access of 1-bromoindolizines in high yields has been developed. This protocol is accomplished via a reaction sequence of 1,3-dipolar cycloaddition of the pyridinium ylide with maleic anhydride, oxidative decarboxylation of the primary cycloadduct, and dehydrogenative bromination of the resulting 1-unsubstituted indolizine. Copper chloride was used as a catalyst and oxygen as the terminal oxidant. This reaction represents the first example of transition-metal-catalyzed direct dehydrogenative bromination of indolizine at the C-1 position. Moreover, the obtained 1-bromoindolizines can be transformed to other 1-substituted indolizines such as 1-arylindolizines via a simple reaction process. PMID:25233481

  14. Propane vehicles : status, challenges, and opportunities.

    SciTech Connect

    Rood Werpy, M.; Burnham, A.; Bertram, K.; Energy Systems

    2010-06-17

    Propane as an auto fuel has a high octane value and has key properties required for spark-ignited internal combustion engines. To operate a vehicle on propane as either a dedicated fuel or bi-fuel (i.e., switching between gasoline and propane) vehicle, only a few modifications must be made to the engine. Until recently propane vehicles have commonly used a vapor pressure system that was somewhat similar to a carburetion system, wherein the propane would be vaporized and mixed with combustion air in the intake plenum of the engine. This leads to lower efficiency as more air, rather than fuel, is inducted into the cylinder for combustion (Myers 2009). A newer liquid injection system has become available that injects propane directly into the cylinder, resulting in no mixing penalty because air is not diluted with the gaseous fuel in the intake manifold. Use of a direct propane injection system will improve engine efficiency (Gupta 2009). Other systems include the sequential multi-port fuel injection system and a bi-fuel 'hybrid' sequential propane injection system. Carbureted systems remain in use but mostly for non-road applications. In the United States a closed-loop system is used in after-market conversions. This system incorporates an electronic sensor that provides constant feedback to the fuel controller to allow it to measure precisely the proper air/fuel ratio. A complete conversion system includes a fuel controller, pressure regulator valves, fuel injectors, electronics, fuel tank, and software. A slight power loss is expected in conversion to a vapor pressure system, but power can still be optimized with vehicle modifications of such items as the air/fuel mixture and compression ratios. Cold start issues are eliminated for vapor pressure systems since the air/fuel mixture is gaseous. In light-duty propane vehicles, the fuel tank is typically mounted in the trunk; for medium- and heavy-duty vans and trucks, the tank is located under the body of the vehicle

  15. Modular o-quinone catalyst system for dehydrogenation of tetrahydroquinolines under ambient conditions.

    PubMed

    Wendlandt, Alison E; Stahl, Shannon S

    2014-08-27

    Quinolines are common pharmacophores present in numerous FDA-approved pharmaceuticals and other bioactive compounds. Here, we report the design and development of new o-quinone-based catalysts for the oxidative dehydrogenation of tetrahydroquinolines to afford quinolines. Use of a Co(salophen) cocatalyst allows the reaction to proceed efficiently with ambient air at room temperature. The utility of the catalytic method is demonstrated in the preparation of a number of medicinally relevant quinolines. PMID:25109345

  16. Palladium-catalyzed cross-dehydrogenative functionalization of C(sp(2))-H Bonds.

    PubMed

    Wu, Yinuo; Wang, Jun; Mao, Fei; Kwong, Fuk Yee

    2014-01-01

    The catalytic cross-dehydrogenative coupling (CDC) reaction has received intense attention in recent years. The attractive feature of this coupling process is the formation of a C-C bond from two C-H moieties under oxidative conditions. In this Focus Review, recent advances in the palladium-catalyzed CDC reactions of C(sp(2) )-H bond are summarized, with a focus on the period from 2011 to early 2013. PMID:24123795

  17. Synthesis of cyclic enones via direct palladium-catalyzed aerobic dehydrogenation of ketones.

    PubMed

    Diao, Tianning; Stahl, Shannon S

    2011-09-21

    α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. Here, we report the discovery and application of Pd(DMSO)(2)(TFA)(2) as a catalyst for direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O(2) as the oxidant. The substrate scope includes heterocyclic ketones and several natural-product precursors. PMID:21851123

  18. Synthesis of Cyclic Enones via Direct Palladium-Catalyzed Aerobic Dehydrogenation of Ketones

    PubMed Central

    Diao, Tianning

    2011-01-01

    α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. Here, we report the discovery and application of Pd(DMSO)2(TFA)2 as a catalyst for direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O2 as the oxidant. The substrate scope includes heterocyclic ketones and several natural-product precursors. PMID:21851123

  19. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    SciTech Connect

    Svane, K. L. Hammer, B.

    2014-11-07

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations.

  20. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    NASA Astrophysics Data System (ADS)

    Svane, K. L.; Hammer, B.

    2014-11-01

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations.

  1. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces.

    PubMed

    Svane, K L; Hammer, B

    2014-11-01

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations. PMID:25381535

  2. Synthesis of Borohydride and Catalytic Dehydrogenation by Hydrogel Based Catalyst

    NASA Astrophysics Data System (ADS)

    Boynuegri, Tugba Akkas; Karabulut, Ahmet F.; Guru, Metin

    2016-08-01

    This paper deals with the synthesis of calcium borohydride (Ca(BH4)2) as hydrogen storage material. Calcium chloride salt (CaCl2), magnesium hydride (MgH2), and boron oxide (B2O3) were used as reactants in the mechanochemical synthesis of Ca(BH4)2. The mechanochemical reaction was carried out by means of Spex type ball milling without applying high pressure and temperature. Parametric studies have been established at different reaction times and for different amounts of reactants at a constant ball to powder ratio (BPR) 4:1. The best combination was determined by Fourier Transform Infrared (FT-IR) analysis. According to the FT-IR analysis, reaction time, the first reaction parameter, was found as 1600 min. After the reaction time was fixed at 1600 min, the difference of the B-H peak areas was dependent on the amount of reactant MgH2 that was investigated. The amount of the reactant (MgH2), the second reaction parameter, was measured to be 2.85 times more than the stoichiometric amount of MgH2. According to our previous studies, BPR was selected as 4:1 for all experiments. Samples were prepared in a glove box under argon atmosphere but the time that elapsed for FT-IR analysis highly affected B-H bonds. B-H peak areas clearly decreased with time because of negative effect of ambient atmosphere. A catalyst was prepared by absorbing cobalt fluoride (CoF2) in poly (acrylamide-co-acrylic acid) hydrogel matrices type and its catalytic dehydrogenation performance that has been characterized by the catalytic reaction of sodium borohydride's known hydrogen capacity in an alkaline medium. The metal amount of hydrogel catalyst was determined as 135.82 mg Co by Atomic Absorption Spectroscopy (AAS). The specific dehydrogenation capacity of the Co active compound in the catalyst thanks to catalytic dehydrogenation of commercial sodium borohydride was measured as 1.66 mL H2/mg Co.

  3. Synthesis of Borohydride and Catalytic Dehydrogenation by Hydrogel Based Catalyst

    NASA Astrophysics Data System (ADS)

    Boynuegri, Tugba Akkas; Karabulut, Ahmet F.; Guru, Metin

    2016-06-01

    This paper deals with the synthesis of calcium borohydride (Ca(BH4)2) as hydrogen storage material. Calcium chloride salt (CaCl2), magnesium hydride (MgH2), and boron oxide (B2O3) were used as reactants in the mechanochemical synthesis of Ca(BH4)2. The mechanochemical reaction was carried out by means of Spex type ball milling without applying high pressure and temperature. Parametric studies have been established at different reaction times and for different amounts of reactants at a constant ball to powder ratio (BPR) 4:1. The best combination was determined by Fourier Transform Infrared (FT-IR) analysis. According to the FT-IR analysis, reaction time, the first reaction parameter, was found as 1600 min. After the reaction time was fixed at 1600 min, the difference of the B-H peak areas was dependent on the amount of reactant MgH2 that was investigated. The amount of the reactant (MgH2), the second reaction parameter, was measured to be 2.85 times more than the stoichiometric amount of MgH2. According to our previous studies, BPR was selected as 4:1 for all experiments. Samples were prepared in a glove box under argon atmosphere but the time that elapsed for FT-IR analysis highly affected B-H bonds. B-H peak areas clearly decreased with time because of negative effect of ambient atmosphere. A catalyst was prepared by absorbing cobalt fluoride (CoF2) in poly (acrylamide-co-acrylic acid) hydrogel matrices type and its catalytic dehydrogenation performance that has been characterized by the catalytic reaction of sodium borohydride's known hydrogen capacity in an alkaline medium. The metal amount of hydrogel catalyst was determined as 135.82 mg Co by Atomic Absorption Spectroscopy (AAS). The specific dehydrogenation capacity of the Co active compound in the catalyst thanks to catalytic dehydrogenation of commercial sodium borohydride was measured as 1.66 mL H2/mg Co.

  4. An unnatural death by propan-1-ol and propan-2-ol.

    PubMed

    Skopp, Gisela; Gutmann, Isabelle; Schwarz, Clara-Sophie; Schmitt, Georg

    2016-07-01

    A fatality of an inpatient ingesting a disinfectant containing ethanol, propan-1-ol, and propan-2-ol is reported. The alleged survival time was about 1 h. Major findings at autopsy were an extended hemorrhagic lung edema, an edematous brain, and shock kidneys. Concentrations of alcohols and acetone, a major metabolite of propan-2-ol, were determined from body fluids (blood from the heart and the femoral vein, urine, gastric contents) and tissues (brain, muscle, liver, kidneys, lungs) by headspace/gas chromatography using 2-methylpropan-2-ol as the internal standard. All samples investigated were positive for propan-1-ol, propan-2-ol, ethanol, and acetone except stomach contents, where acetone was not detectable. The low concentration of acetone compared to propan-2-ol likely supports the short survival time. The concentration ratios estimated from the results are in accordance with the physico-chemical properties of the particular alcohols, their different affinities towards alcohol dehydrogenase as well as their interdependence during biotransformation. Autopsy did not reveal the cause of death. According to the few published data, blood concentrations of 1.44 and 1.70 mg/g of propan-2-ol and propan-1-ol, respectively, are considered sufficient to have caused the death. This case also points to the need to restrict access to antiseptic solutions containing alcohols in wards with patients at risk. PMID:26712504

  5. A Three-Stage Mechanistic Model for Ammonia Borane Dehydrogenation by Shvo's Catalyst.

    PubMed

    Lu, Zhiyao; Conley, Brian L; Williams, Travis J

    2012-10-01

    We propose a mechanistic model for three-stage dehydrogenation of ammonia borane (AB) catalyzed by Shvo's cyclopentadienone-ligated ruthenium complex. We provide evidence for a plausible mechanism for catalyst deactivation, the transition from fast catalysis to slow catalysis, and relate those findings to the invention of a second-generation catalyst that does not suffer from the same deactivation chemistry.The primary mechanism of catalyst deactivation is borazine-mediated hydroboration of the ruthenium species that is the active oxidant in the fast catalysis case. This transition is characterized by a change in the rate law for the reaction and changes in the apparent resting state of the catalyst. Also, in this slow catalysis situation, we see an additional intermediate in the sequence of boron, nitrogen species, aminodiborane. This occurs with concurrent generation of NH(3), which itself does not strongly affect the rate of AB dehydrogenation. PMID:23335832

  6. A Three-Stage Mechanistic Model for Ammonia Borane Dehydrogenation by Shvo’s Catalyst

    PubMed Central

    Lu, Zhiyao; Conley, Brian L.; Williams, Travis J.

    2012-01-01

    We propose a mechanistic model for three-stage dehydrogenation of ammonia borane (AB) catalyzed by Shvo’s cyclopentadienone-ligated ruthenium complex. We provide evidence for a plausible mechanism for catalyst deactivation, the transition from fast catalysis to slow catalysis, and relate those findings to the invention of a second-generation catalyst that does not suffer from the same deactivation chemistry. The primary mechanism of catalyst deactivation is borazine-mediated hydroboration of the ruthenium species that is the active oxidant in the fast catalysis case. This transition is characterized by a change in the rate law for the reaction and changes in the apparent resting state of the catalyst. Also, in this slow catalysis situation, we see an additional intermediate in the sequence of boron, nitrogen species, aminodiborane. This occurs with concurrent generation of NH3, which itself does not strongly affect the rate of AB dehydrogenation. PMID:23335832

  7. Dehydrogenation of ammonia borane through the third equivalent of hydrogen.

    PubMed

    Zhang, Xingyue; Kam, Lisa; Williams, Travis J

    2016-05-01

    Ammonia borane (AB) has high hydrogen density (19.6 wt%), and can, in principle, release up to 3 equivalents of H2 under mild catalytic conditions. A limited number of catalysts are capable of non-hydrolytic dehydrogenation of AB beyond 2 equivalents of H2 under mild conditions, but none of these is shown directly to derivatise borazine, the product formed after 2 equivalents of H2 are released. We present here a high productivity ruthenium-based catalyst for non-hydrolytic AB dehydrogenation that is capable of borazine dehydrogenation, and thus exhibits among the highest H2 productivity reported to date for anhydrous AB dehydrogenation. At 1 mol% loading, (phen)Ru(OAc)2(CO)2 () effects AB dehydrogenation through 2.7 equivalents of H2 at 70 °C, is robust through multiple charges of AB, and is water and air stable. We further demonstrate that catalyst has the ability both to dehydrogenate borazine in isolation and dehydrogenate AB itself. This is important, both because borazine derivatisation is productivity-limiting in AB dehydrogenation and because borazine is a fuel cell poison that is commonly released in H2 production from this medium. PMID:27052687

  8. Acid-catalyzed dehydrogenation of amine-boranes

    DOEpatents

    Stephens, Frances Helen; Baker, Ralph Thomas

    2010-01-12

    A method of dehydrogenating an amine-borane using an acid-catalyzed reaction. The method generates hydrogen and produces a solid polymeric [R.sup.1R.sup.2B--NR.sup.3R.sup.4].sub.n product. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources.

  9. Acceptorless Photocatalytic Dehydrogenation for Alcohol Decarbonylation and Imine Synthesis

    SciTech Connect

    Ho, Hung-An; Manna, Kuntal; Sadow, Aaron D.

    2012-07-29

    It has come to light: Renewed interest in conversions of highly oxygenated materials has motivated studies of the organometallic-catalyzed photocatalytic dehydrogenative decarbonylation of primary alcohols into alkanes, CO, and H2 (see scheme). Methanol, ethanol, benzyl alcohol, and cyclohexanemethanol are readily decarbonylated. The photocatalysts are also active for amine dehydrogenation to give N-alkyl aldimines and H2.

  10. Acceptorless photocatalytic dehydrogenation for alcohol decarbonylation and imine synthesis.

    PubMed

    Ho, Hung-An; Manna, Kuntal; Sadow, Aaron D

    2012-08-20

    It has come to light: Renewed interest in conversions of highly oxygenated materials has motivated studies of the organometallic-catalyzed photocatalytic dehydrogenative decarbonylation of primary alcohols into alkanes, CO, and H(2). Methanol, ethanol, benzyl alcohol, and cyclohexanemethanol are readily decarbonylated. The photocatalysts are also active for amine dehydrogenation to give N-alkyl aldimines and H(2). PMID:22847764

  11. CELLULAR LIPIDS OF A NOCARDIA GROWN ON PROPANE AND N-BUTANE.

    PubMed

    DAVIS, J B

    1964-07-01

    Lipid fractions of propane- and n-butane-grown nocardial cells each contain a chloroform-soluble, ether-insoluble polymer not observed previously in liquid n-alkane-grown cells. The polymer in propane-grown cells is poly-beta-hydroxybutyrate. The polymer in n-butane-grown cells apparently contains unsaturation in the molecule, and is identified tentatively as a co-polymer of beta-hydroxybutyric and beta-hydroxybutenoic (specifically 3-hydroxy 2-butenoic) acids. The other major component of the lipid fraction consists of triglycerides containing principally palmitic and stearic acids. There seems to be little qualitative distinction in the glycerides of propane- or n-butane-grown cells. Oxidative assimilation of n-butane is described. PMID:14199017

  12. Auto-ignition and upper explosion limit of rich propane-air mixtures at elevated pressures.

    PubMed

    Norman, F; Van den Schoor, F; Verplaetsen, F

    2006-09-21

    The auto-ignition limits of propane-air mixtures at elevated pressures up to 15 bar and for concentrations from 10 mol% up to 70 mol% are investigated. The experiments are performed in a closed spherical vessel with a volume of 8 dm3. The auto-ignition temperatures decrease from 300 degrees C to 250 degrees C when increasing the pressure from 1 bar to 14.5 bar. It is shown that the fuel concentration most sensitive to auto-ignition depends on initial pressure. A second series of experiments investigates the upper flammability limit of propane-air mixtures at initial temperatures up to 250 degrees C and pressures up to 30 bar near the auto-ignition area. Finally the propane auto-oxidation is modelled using several detailed kinetic reaction mechanisms and these numerical calculations are compared with the experimental results. PMID:16716499

  13. No. 2 heating oil/propane program

    SciTech Connect

    McBrien, J.

    1991-06-01

    During the 1990/91 heating season, the Massachusetts Division of Energy Resources (DOER) participated in a joint data collection program between several state energy offices and the federal Department of Energy's (DOE) Energy Information Administration (EIA). The purpose of the program was to collect and monitor retail and wholesale heating oil and propane prices and inventories from October 1990 through March 1991. This final report begins with an overview of the unique events which had an impact on the reporting period. Next, the report summarizes the results from the residential heating oil and propane price surveys conducted by DOER over the 1990/91 heating season. The report also incorporates the wholesale heating oil and propane prices and inventories collected by the EIA and distributed to the states.

  14. Propane Clathrate Hydrate Formation Accelerated by Methanol.

    PubMed

    Amtawong, Jaruwan; Guo, Jin; Hale, Jared S; Sengupta, Suvrajit; Fleischer, Everly B; Martin, Rachel W; Janda, Kenneth C

    2016-07-01

    The role of methanol as both an inhibitor and a catalyst for the formation of clathrate hydrates (CHs) has been a topic of intense study. We report a new quantitative study of the kinetics of propane CH formation at 253 K from the reaction of propane gas with <75 μm ice particles that have been doped with varying amounts of methanol. We find that methanol significantly accelerates the formation reaction with quite small doping quantities. Even for only 1 methanol molecule per 10 000 water molecules, the maximum uptake rate of propane into CHs is enhanced and the initiation pressure is reduced. These results enable more efficient production of CHs for gas storage. This remarkable acceleration of the CH formation reaction by small quantities of methanol may place constraints on the mechanism of the inhibition effect observed under other conditions, usually employing much larger quantities of methanol. PMID:27275862

  15. A reusable unsupported rhenium nanocrystalline catalyst for acceptorless dehydrogenation of alcohols through γ-C-H activation.

    PubMed

    Yi, Jing; Miller, Jeffrey T; Zemlyanov, Dmitry Y; Zhang, Ruihong; Dietrich, Paul J; Ribeiro, Fabio H; Suslov, Sergey; Abu-Omar, Mahdi M

    2014-01-13

    Rhenium nanocrystalline particles (Re NPs), of 2 nm size, were prepared from NH4ReO4 under mild conditions in neat alcohol. The unsupported Re NPs convert secondary and benzylic alcohols to ketones and aldehydes, respectively, through catalytic acceptorless dehydrogenation (AD). The oxidant- and acceptor-free neat dehydrogenation of alcohols to obtain dihydrogen gas is a green and atom-economical process for making carbonyl compounds. Secondary aliphatic alcohols give quantitative conversion and yield. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Re K-edge X-ray absorption near-edge structure (XANES), and X-ray absorption fine structure (EXAFS) data confirmed the characterization of the Re NPs as metallic rhenium with surface oxidation to rhenium(IV) oxide (ReO2). Isotope labeling experiments revealed a novel γ-CH activation mechanism for AD of alcohols. PMID:24282107

  16. An experimental survey of additives for improving dehydrogenation properties of magnesium hydride

    NASA Astrophysics Data System (ADS)

    Zhou, Chengshang; Fang, Zhigang Zak; Sun, Pei

    2015-03-01

    The use of a wide range of additives has been known as an important method for improving hydrogen storage properties of MgH2. There is a lack of a standard methodology, however, that can be used to select or compare the effectiveness of different additives. A systematic experimental survey was carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. MgH2 with various additives were prepared by using a high-energy-high-pressure planetary ball milling method and characterized by using thermogravimetric analysis (TGA) techniques. The results showed that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Additives such as Al, In, Sn, Si showed minor effects on the kinetics of the dehydrogenation of MgH2, while exhibiting moderate thermodynamic destabilizing effects. In combination, MgH2 with both kinetic and thermodynamic additives, such as the MgH2-In-TiMn2 system, exhibited a drastically decreased dehydrogenation temperature.

  17. Cross-dehydrogenative coupling for the intermolecular C-O bond formation.

    PubMed

    Krylov, Igor B; Vil', Vera A; Terent'ev, Alexander O

    2015-01-01

    The present review summarizes primary publications on the cross-dehydrogenative C-O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C-O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C-O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C-H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C-O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH- and OH-reagents, closely related C-H activation processes involving intermolecular C-O bond formation are discussed: acyloxylation reactions with ArI(O2CR)2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.). PMID:25670997

  18. Dehydrogenation of dodecahydro-N-ethylcarbazole on Pd/Al2O3 model catalysts.

    PubMed

    Sobota, Marek; Nikiforidis, Ioannis; Amende, Max; Sanmartín Zanón, Beatriz; Staudt, Thorsten; Höfert, Oliver; Lykhach, Yaroslava; Papp, Christian; Hieringer, Wolfgang; Laurin, Mathias; Assenbaum, Daniel; Wasserscheid, Peter; Steinrück, Hans-Peter; Görling, Andreas; Libuda, Jörg

    2011-10-01

    To elucidate the dehydrogenation mechanism of dodecahydro-N-ethylcarbazole (H(12)-NEC) on supported Pd catalysts, we have performed a model study under ultra high vacuum (UHV) conditions. H(12)-NEC and its final dehydrogenation product, N-ethylcarbazole (NEC), were deposited by physical vapor deposition (PVD) at temperatures between 120 K and 520 K onto a supported model catalyst, which consisted of Pd nanoparticles grown on a well-ordered alumina film on NiAl(110). Adsorption and thermally induced surface reactions were followed by infrared reflection absorption spectroscopy (IRAS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) in combination with density functional theory (DFT) calculations. It was shown that, at 120 K, H(12)-NEC adsorbs molecularly both on the Al(2)O(3)/NiAl(110) support and on the Pd particles. Initial activation of the molecule occurs through C-H bond scission at the 8a- and 9a-positions of the carbazole skeleton at temperatures above 170 K. Dehydrogenation successively proceeds with increasing temperature. Around 350 K, breakage of one C-N bond occurs accompanied by further dehydrogenation of the carbon skeleton. The decomposition intermediates reside on the surface up to 500 K. At higher temperatures, further decay to small fragments and atomic species is observed. These species block most of the absorption sites on the Pd particles, but can be oxidatively removed by heating in oxygen at 600 K, fully restoring the original adsorption properties of the model catalyst. PMID:21953930

  19. Cross-dehydrogenative coupling for the intermolecular C–O bond formation

    PubMed Central

    Krylov, Igor B; Vil’, Vera A

    2015-01-01

    Summary The present review summarizes primary publications on the cross-dehydrogenative C–O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C–O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C–O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C–H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C–O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH- and OH-reagents, closely related C–H activation processes involving intermolecular C–O bond formation are discussed: acyloxylation reactions with ArI(O2CR)2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.). PMID:25670997

  20. . . . While Others Conserve Cash by Converting from Gasoline to Propane.

    ERIC Educational Resources Information Center

    Rasmussen, Scott A.

    1988-01-01

    Since 1983, when the David Douglas Public Schools (Portland, Oregon) converted 30 buses to propane fuel, the district has saved $75,000 in fuel and maintenance costs. Propane is priced consistently lower than gasoline and burns cleaner. Since propane engines do not require a carburetor, there are fewer maintenance problems. (MLH)

  1. Methanol dehydrogenation by iridium N-heterocyclic carbene complexes.

    PubMed

    Campos, Jesús; Sharninghausen, Liam S; Manas, Michael G; Crabtree, Robert H

    2015-06-01

    A series of homogeneous iridium bis(N-heterocyclic carbene) catalysts are active for three transformations involving dehydrogenative methanol activation: acceptorless dehydrogenation, transfer hydrogenation, and amine monoalkylation. The acceptorless dehydrogenation reaction requires base, yielding formate and carbonate, as well as 2-3 equivalents of H2. Of the few homogeneous systems known for this reaction, our catalysts tolerate air and employ simple ligands. Transfer hydrogenation of ketones and imines from methanol is also possible. Finally, N-monomethylation of anilines occurs through a "borrowing hydrogen" reaction. Notably, this reaction is highly selective for the monomethylated product. PMID:25615426

  2. 21 CFR 582.1655 - Propane.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Propane. 582.1655 Section 582.1655 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives §...

  3. 21 CFR 582.1655 - Propane.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Propane. 582.1655 Section 582.1655 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives §...

  4. 21 CFR 184.1655 - Propane.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... in the liquid state. Propane is obtained from natural gas by fractionation following absorption in... also known as dimethylmethane or propyl hydrid. It is a colorless, odorless, flammable gas at normal... manufacturing practice conditions of use: (1) The ingredient is used as a propellant, aerating agent, and gas...

  5. 21 CFR 184.1655 - Propane.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... in the liquid state. Propane is obtained from natural gas by fractionation following absorption in... also known as dimethylmethane or propyl hydrid. It is a colorless, odorless, flammable gas at normal... manufacturing practice conditions of use: (1) The ingredient is used as a propellant, aerating agent, and gas...

  6. 21 CFR 184.1655 - Propane.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... state. Propane is obtained from natural gas by fractionation following absorption in oil, adsorption to... dimethylmethane or propyl hydrid. It is a colorless, odorless, flammable gas at normal temperatures and pressures... practice conditions of use: (1) The ingredient is used as a propellant, aerating agent, and gas as...

  7. 21 CFR 184.1655 - Propane.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... in the liquid state. Propane is obtained from natural gas by fractionation following absorption in... also known as dimethylmethane or propyl hydrid. It is a colorless, odorless, flammable gas at normal... manufacturing practice conditions of use: (1) The ingredient is used as a propellant, aerating agent, and gas...

  8. Case Study - Propane School Bus Fleets

    SciTech Connect

    Laughlin, M; Burnham, A.

    2014-08-31

    As part of the U.S. Department of Energy’s (DOE’s) effort to deploy transportation technologies that reduce U.S. dependence on imported petroleum, this study examines five school districts, one in Virginia and four in Texas, successful use of propane school buses. These school districts used school buses equipped with the newly developed liquid propane injection system that improves vehicle performance. Some of the school districts in this study saved nearly 50% on a cost per mile basis for fuel and maintenance relative to diesel. Using Argonne National Laboratory’s Alternative Fuel Life-Cycle Environmental and Economic Transportation (AFLEET) Tool developed for the DOE’s Clean Cities program to help Clean Cities stakeholders estimate petroleum use, greenhouse gas (GHG) emissions, air pollutant emissions and cost of ownership of light-duty and heavy-duty vehicles, the results showed payback period ranges from 3—8 years, recouping the incremental cost of the vehicles and infrastructure. Overall, fuel economy for these propane vehicles is close to that of displaced diesel vehicles, on an energy-equivalent basis. In addition, the 110 propane buses examined demonstrated petroleum displacement, 212,000 diesel gallon equivalents per year, and GHG benefits of 770 tons per year.

  9. Alkane metathesis by tandem alkane-dehydrogenation-olefin-metathesis catalysis and related chemistry.

    PubMed

    Haibach, Michael C; Kundu, Sabuj; Brookhart, Maurice; Goldman, Alan S

    2012-06-19

    stable solid metal oxides as the olefin-metathesis catalysts. Both the pincer complexes and the alkylidene complexes have been supported on alumina via adsorption through basic para-substituents. This process does not significantly affect catalyst activity, and in some cases it increases both the catalyst lifetime and the compatibility of the co-catalysts. These molecular catalysts are the first systems that effect alkane metathesis with molecular-weight selectivity, particularly for the conversion of C(n)n-alkanes to C(2n-2)n-alkanes plus ethane. This molecular-weight selectivity offers a critical advantage over the few previously reported alkane metathesis systems. We have studied the factors that determine molecular-weight selectivity in depth, including the isomerization of the olefinic intermediates and the regioselectivity of the pincer-iridium catalyst for dehydrogenation at the terminal position of the n-alkane. Our continuing work centers on the development of co-catalysts with improved interoperability, particularly olefin-metathesis catalysts that are more robust at high temperature and dehydrogenation catalysts that are more active at low temperature. We are also designing dehydrogenation catalysts based on metals other than iridium. Our ongoing mechanistic studies are focused on the apparently complex combination of factors that determine molecular-weight selectivity. PMID:22584036

  10. Adsorption and dehydrogenation of tetrahydroxybenzene on Cu(111).

    PubMed

    Bebensee, Fabian; Svane, Katrine; Bombis, Christian; Masini, Federico; Klyatskaya, Svetlana; Besenbacher, Flemming; Ruben, Mario; Hammer, Bjørk; Linderoth, Trolle

    2013-10-18

    Adsorption of tetrahydroxybenzene (THB) on Cu(111) and Au(111) surfaces is studied using a combination of STM, XPS, and DFT. THB is deposited intact, but on Cu(111) it undergoes gradual dehydrogenation of the hydroxyl groups as a function of substrate temperature, yielding a pure dihydroxy-benzoquinone phase at 370 K. Subtle changes to the adsorption structure upon dehydrogenation are explained from differences in molecule-surface bonding. PMID:23999460

  11. Four-electron oxidative dehydrogenation induced by proton-coupled electron transfer in ruthenium(III) complex with 2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolate.

    PubMed

    Mitsuhashi, Ryoji; Suzuki, Takayoshi; Sunatsuki, Yukinari

    2013-09-01

    New ruthenium(II or III) complexes with general formula [Ru(O-N)(bpy)2](n+) (O-N = unsymmetrical bidentate phenolate ligand; bpy = 2,2'-bipyridine) were synthesized, and their crystal structures and electrochemical properties were characterized. Ru(II) complexes with 2-(2-imidazolinyl)phenolate (Himn(-)) or 2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolate (Hthp(-)) could be deprotonated by addition of excess KO(t)Bu, although the deprotonated species were easily reprotonated by exposure to air. Unlike these Ru(II) complexes, their Ru(III) analogs showed interesting ligand oxidation reactions upon addition of bases. With [Ru(III)(Himn)(bpy)2](2+), two-electron oxidation of Himn(-) and reduction of the Ru(III) center resulted in conversion of the 2-imidazolinyl group to a 2-imidazolyl group. On the other hand, the corresponding Hthp(-) complex exhibited four-electron oxidation of the ligand to form 2-(2-pyrimidyl)phenolate (pym(-)). These aromatization reactions of imidazolinyl and 1,4,5,6-tetrahydropyrimidyl groups were also achieved by the electrochemically generated Ru(III) complexes. PMID:23967872

  12. Aerobic palladium(II)-catalyzed dehydrogenation of cyclohexene-1-carbonyl indole amides: an indole-directed aromatization.

    PubMed

    Kandukuri, Sandeep R; Oestreich, Martin

    2012-10-01

    A palladium(II)-catalyzed oxidative dehydrogenation of cyclohexene-1-carbonyl indole amides yielding the corresponding benzoylindoles is reported. The new aromatization is also applied to functionalized indoles such as tryptamine and tryptophan. The tethered indole is likely acting as a directing group for allylic C-H bond activation, and there is evidence for a mechanism proceeding through 1,3-diene formation followed by aromatization. PMID:22950832

  13. Pincer-Type Complexes for Catalytic (De)Hydrogenation and Transfer (De)Hydrogenation Reactions: Recent Progress.

    PubMed

    Werkmeister, Svenja; Neumann, Jacob; Junge, Kathrin; Beller, Matthias

    2015-08-24

    Pincer complexes are becoming increasingly important for organometallic chemistry and organic synthesis. Since numerous applications for such catalysts have been developed in recent decades, this Minireview covers progress in their use as catalysts for (de)hydrogenation and transfer (de)hydrogenation reactions during the last four years. Aside from noble-metal-based pincer complexes, the corresponding base metal complexes are also highlighted and their applications summarized. PMID:26179375

  14. A comparative theoretical study for the methanol dehydrogenation to CO over Pt3 and PtAu2 clusters.

    PubMed

    Zhong, Wenhui; Liu, Yuxia; Zhang, Dongju

    2012-07-01

    The density functional theory (DFT) calculations are carried out to study the mechanism details and the ensemble effect of methanol dehydrogenation over Pt(3) and PtAu(2) clusters, which present the smallest models of pure Pt clusters and bimetallic PtAu clusters. The energy diagrams are drawn out along both the initial O-H and C-H bond scission pathways via the four sequential dehydrogenation processes, respectively, i.e., CH(3)OH → CH(2)OH → CH(2)O → CHO → CO and CH(3)OH → CH(3)O → CH(2)O → CHO → CO, respectively. It is revealed that the reaction kinetics over PtAu(2) is significantly different from that over Pt(3). For the Pt(3)-mediated reaction, the C-H bond scission pathway, where an ensemble composed of two Pt atoms is required to complete methanol dehydrogenation, is energetically more favorable than the O-H bond scission pathway, and the maximum barrier along this pathway is calculated to be 12.99 kcal mol(-1). In contrast, PtAu(2) cluster facilitates the reaction starting from the O-H bond scission, where the Pt atom acts as the active center throughout each elementary step of methanol dehydrogenation, and the initial O-H bond scission with a barrier of 21.42 kcal mol(-1) is the bottom-neck step of methanol decomposition. Importantly, it is shown that the complete dehydrogenation product of methanol, CO, can more easily dissociate from PtAu(2) cluster than from Pt(3) cluster. The calculated results over the model clusters provide assistance to some extent for understanding the improved catalytic activity of bimetal PtAu catalysts toward methanol oxidation in comparison with pure Pt catalysts. PMID:22160734

  15. How strain affects the reactivity of surface metal oxide catalysts.

    PubMed

    Amakawa, Kazuhiko; Sun, Lili; Guo, Chunsheng; Hävecker, Michael; Kube, Pierre; Wachs, Israel E; Lwin, Soe; Frenkel, Anatoly I; Patlolla, Anitha; Hermann, Klaus; Schlögl, Robert; Trunschke, Annette

    2013-12-16

    Highly dispersed molybdenum oxide supported on mesoporous silica SBA-15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2-2.5 Mo atoms nm(-2) ). X-ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature-programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O-K-edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity. PMID:24259425

  16. Visible light driven benzyl alcohol dehydrogenation in a dye-sensitized photoelectrosynthesis cell.

    PubMed

    Song, Wenjing; Vannucci, Aaron K; Farnum, Byron H; Lapides, Alexander M; Brennaman, M Kyle; Kalanyan, Berç; Alibabaei, Leila; Concepcion, Javier J; Losego, Mark D; Parsons, Gregory N; Meyer, Thomas J

    2014-07-01

    Light-driven dehydrogenation of benzyl alcohol (BnOH) to benzaldehyde and hydrogen has been shown to occur in a dye-sensitized photoelectrosynthesis cell (DSPEC). In the DSPEC, the photoanode consists of mesoporous films of TiO2 nanoparticles or of core/shell nanoparticles with tin-doped In2O3 nanoparticle (nanoITO) cores and thin layers of TiO2 deposited by atomic layer deposition (nanoITO/TiO2). Metal oxide surfaces were coderivatized with both a ruthenium polypyridyl chromophore in excess and an oxidation catalyst. Chromophore excitation and electron injection were followed by cross-surface electron-transfer activation of the catalyst to -Ru(IV)═O(2+), which then oxidizes benzyl alcohol to benzaldehyde. The injected electrons are transferred to a Pt electrode for H2 production. The nanoITO/TiO2 core/shell structure causes a decrease of up to 2 orders of magnitude in back electron-transfer rate compared to TiO2. At the optimized shell thickness, sustained absorbed photon to current efficiency of 3.7% was achieved for BnOH dehydrogenation, an enhancement of ~10 compared to TiO2. PMID:24933178

  17. Adsorptive separation of propylene-propane mixtures

    SciTech Connect

    Jaervelin, H.; Fair, J.R. )

    1993-10-01

    The separation of propylene-propane mixtures is of great commercial importance and is carried out by fractional distillation. It is claimed to be the most energy-intensive distillation practiced in the United States. The purpose of this paper is to describe experimental work that suggests a practical alternative to distillation for separating the C[sub 3] hydrocarbons: adsorption. As studied, the process involves three adsorptive steps: initial separation with molecular sieves with heavy dilution with an inert gas; separation of propylene and propane separately from the inert gas, using activated carbon; and drying of the product streams with any of several available desiccants. The research information presented here deals with the initial step and includes both equilibrium and kinetic data. Isotherms are provided for propylene and propane adsorbed on three zeolites, activated alumina, silica gel, and coconut-based activated carbon. Breakthrough data are provided for both adsorption and regeneration steps for the zeolites, which were found to be superior to the other adsorbents for breakthrough separations. A flow diagram for the complete proposed process is included.

  18. Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures

    SciTech Connect

    Ojeda, Manuel; Iglesia, Enrique

    2008-11-24

    Formic acid (HCOOH) is a convenient hydrogen carrier in fuel cells designed for portable use. Recent studies have shown that HCOOH decomposition is catalyzed with Ru-based complexes in the aqueous phase at near-ambient temperatures. HCOOH decomposition reactions are used frequently to probe the effects of alloying and cluster size and of geometric and electronic factors in catalysis. These studies have concluded that Pt is the most active metal for HCOOH decomposition, at least as large crystallites and extended surfaces. The identity and oxidation state of surface metal atoms influence the relative rates of dehydrogenation (HCOOH {yields} H{sub 2} + CO{sub 2}) and dehydration (HCOOH {yields} H{sub 2}O + CO) routes, a selectivity requirement for the synthesis of CO-free H{sub 2} streams for low-temperature fuel cells. Group Ib and Group VIII noble metals catalyze dehydrogenation selectively, while base metals and metal oxides catalyze both routes, either directly or indirectly via subsequent water-gas shift (WGS) reactions.

  19. Oxidant-free conversion of primary amines to nitriles.

    PubMed

    Tseng, Kuei-Nin T; Rizzi, Andrew M; Szymczak, Nathaniel K

    2013-11-01

    An amide-derived NNN-Ru(II) hydride complex catalyzes oxidant-free, acceptorless, and chemoselective dehydrogenation of primary and secondary amines to the corresponding nitriles and imines with liberation of dihydrogen. The catalyst system tolerates oxidizable functionality and is selective for the dehydrogenation of primary amines (-CH2NH2) in the presence of amines without α-CH hydrogens. PMID:24144014

  20. "Black-colored olivines" in peridotites: dehydrogenation from hydrous olivines

    NASA Astrophysics Data System (ADS)

    Arai, Shoji; Hoshikawa, Chihiro; Miura, Makoto

    2015-04-01

    Fresh olivines that are black to the naked eye are found in some dunites. Peridotites are easily converted to be black in color, when serpentinized, due to production of secondary fine magnetite particles. The dunites that contain fresh but black-colored olivines are usually coarse-grained. These coarse olivine grains are sometimes very heterogeneous in color; the blackish part grades to whitish parts in single grains. The black color is due to homegeneous distribution of minute (< 10 microns) black particles in olivine. They are rod-like or plate-like in shape in thin section, sometimes being aligned under crystallographic control of the host olivine. Olivines are clear and free of these inclusions around primary chromian spinel inclusions or chromian spinel lamellae (Arai, 1978). Raman spectroscopy indicates the minute black particles are magnetite always associated with diopside. It is interesting to note that olivine in mantle peridotites accompanied by the black-colored dunites is totally free of the black inclusions, giving the ordinary colors (pale yellow to whitish) of Mg-rich olivine. It is not likely that the magnetite inclusions formed through secondary oxidation of olivine by invasion of oxygen, which is possible along cracks or grain boundaries. They most probably formed due to dehydrogenation from primary OH-bearing olivines upon cooling. Hydrogen was quickly diffused out from the olivines to leave magnetite and excess silica. The excess silica was possibly combined with a monticellite component to form diopside. The OH-bearing (hydrous) olivines can be precipitated from hydrous magmas, and the hydrous nature of the magma can promote an increase in grain size due to faster diffusion of elements. The minute inclusions of magnetite + diopside is thus an indicator of primary hydrous character of host olivine.

  1. Equivalence of pure propane and propane TE gases for microdosimetric measurements.

    PubMed

    Chiriotti, S; Moro, D; Colautti, P; Conte, V; Grosswendt, B

    2015-09-01

    A tissue-equivalent proportional counter (TEPC) simulates micrometric volumes of tissue if the energy deposited in the counter cavity is the same as that in the tissue volume. Nevertheless, a TEPC measures only the ionisations created in the gas, which are later converted into imparted energy. Therefore, the equivalence of the simulated diameter (Dρ) in two gases should be based on the equality of the mean number of ions pairs in the gas rather than on the imparted energy. Propane-based tissue-equivalent gas is the most commonly used gas mixture at present, but it has the drawback that its composition may change with time. From this point of view, the use of pure propane offers practical advantages: higher gas gain and longer stability. In this work, microdosimetric measurements performed with pure propane, at site sizes 0.05 mg cm(-2) ≤ Dρ ≤ 0.3 mg cm(-2), demonstrate that the response of a propane-filled detector in gamma and in neutron fields is almost the same if an appropriate gas density is used. PMID:25944956

  2. 77 FR 2293 - AmeriGas Propane, L.P., AmeriGas Propane, Inc., Energy Transfer Partners, L.P., and Energy...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... AmeriGas Propane, L.P., AmeriGas Propane, Inc., Energy Transfer Partners, L.P., and Energy Transfer...'') with AmeriGas Propane, L.P. (``AmeriGas''), AmeriGas Propane, Inc., Energy Transfer Partners, L.P. (``ETP''), and Energy Transfer Partners GP, L.P. (``ETP GP''), which is designed to guard...

  3. Fe-Catalyzed Cross-Dehydrogenative Coupling Reactions.

    PubMed

    Lv, Leiyang; Li, Zhiping

    2016-08-01

    Cross-dehydrogenative coupling (CDC), which enables the formation of carbon-carbon (C-C) and C-heteroatom bonds from the direct coupling of two C-H bonds or C-H/X-H bonds, represents a new state of the art in the field of organic chemistry. Iron, a prominent metal, has already shown its versatile application in chemical synthesis. This review attempts to provide a comprehensive understanding of the evolution of cross-dehydrogenative coupling via iron catalysis, as well as its application in synthetic chemistry. PMID:27573390

  4. Design, synthesis, structure, and dehydrogenation reactivity of a water-soluble o-iodoxybenzoic acid derivative bearing a trimethylammonium group.

    PubMed

    Cui, Li-Qian; Dong, Zhi-Lei; Liu, Kai; Zhang, Chi

    2011-12-16

    5-Trimethylammonio-1,3-dioxo-1,3-dihydro-1λ(5)-benzo[d][1,2]iodoxol-1-ol anion (AIBX 1a), an o-iodoxybenzoic acid (IBX) derivative having the trimethylammonium moiety on its phenyl ring, possesses very good solubility in water and distinct oxidative properties from IBX, which is demonstrated in the oxidation of various β-keto esters to the corresponding dehydrogenated products using water as cosolvent. The regeneration of AIBX 1a can be easily realized from the reaction mixture due to its good water solubility. PMID:22082110

  5. Thermocatalytic Destruction of Gas-Phase Perchloroethylene Using Propane as a Hydrogen Source

    PubMed Central

    Willinger, Marty; Rupp, Erik; Barbaris, Brian; Gao, Song; Arnolda, Robert; Betterton, Eric; Sáez, A. Eduardo

    2009-01-01

    The use of propane in combination with oxygen to promote the destruction of perchloroethylene (PCE) over a platinum (Pt)/rhodium (Rh) catalyst on a cerium/zirconium oxide washcoat supported on an alumina monolith was explored. Conversions of PCE were measured in a continuous flow reactor with residence times less than 0.5 s and temperatures ranging from 200 to 600°C. The presence of propane was shown to increase significantly the conversion of PCE over oxygen-only conditions. Conversions close to 100% were observed at temperatures lower than 450°C with 20% oxygen and 2% propane in the feed, which makes this process attractive from a practical standpoint. In the absence of oxygen, PCE conversion is even higher, but the catalyst suffers significant deactivation in less than an hour. Even though results show that oxygen competes with reactants for active sites on the catalyst, the long-term stability that oxygen confers to the catalyst makes the process an efficient alternative to PCE oxidation. A Langmuir-Hinshelwood competitive adsorption model is proposed to quantify PCE conversion. PMID:19217713

  6. Catalytic propane reforming mechanism over Mn-Doped CeO2 (111)

    NASA Astrophysics Data System (ADS)

    Krcha, Matthew D.; Janik, Michael J.

    2015-10-01

    MnOx/CeOx mixed oxide systems exhibit encouraging hydrocarbon oxidation activity, without the inclusion of a noble metal. Using density functional theory (DFT) methods, we examined the oxidative reforming path of propane over the Mn-doped CeO2 (1 1 1) surface. A plausible set of elementary reaction steps are identified for conversion of propane to CO/CO2 and H2/H2O over the oxide surface. The rate-limiting reaction process may vary with redox conditions, with C-H dissociation limiting under more oxidizing conditions and more complex reaction sequences, including surface re-oxidation, limiting under highly reducing conditions. The possibility of intermediate desorption from the surface during the reforming process is low, with desorption energies of the intermediates being much less favorable than further surface reactions until CO/CO2 products are formed. The reforming paths over Mn-doped ceria are similar to those previously identified over Zr-doped ceria. The extent of surface reduction and the electronic structure of the surface intermediates are examined.

  7. Isolation and Characterization of Ethane, Propane, and Butane Consuming Bacteria from Marine Hydrocarbon Seeps

    NASA Astrophysics Data System (ADS)

    Redmond, M. C.; Valentine, D. L.

    2005-12-01

    Three strains of ethane, propane, or butane consuming bacteria were isolated from marine hydrocarbon seep sediments at Coal Oil Point, off shore Santa Barbara, CA. These three isolates (MR1, MR2 and MR3) were capable of growth at natural environmental temperatures and salinity. Isolate MR2 was capable of growth on ethane or propane as the sole carbon source, isolate MR4 on propane or butane, and isolate MR3 on ethane, propane, or butane. All three isolates were also able to grow on other carbon-containing molecules, including ethanol, 1-propanol, 2-propanol, acetate, butyrate, sucrose, and dextrose, and isolates MR3 and MR4 were able to grow on 1-butanol and 2-butanol. None showed significant growth with methane, methanol, or formate as the sole carbon source. 16S rDNA sequencing indicated that isolate MR2 was most closely related to the gamma-Proteobacterium Pseudomonas stutzeri, while isolates MR3 and MR4 were both Gram-positive and most similar to Rhodococcus wratislaviensis and Rhodococcus opacus, respectively. Compared to methanotrophs, relatively little is known about the organisms that consume the C2-C4 alkanes, but both our isolates and the previously described species appear to be capable of metabolizing a wide variety of carbon compounds, including several common pollutants. The growth of these hydrocarbon-oxidizing bacteria on other organic compounds raises the possibility that the abundance and distribution of organic matter might be expected to impact the oxidation of C2-C4 hydrocarbons. Additional studies will further characterize the range of metabolism, and will investigate the importance of these organisms in natural hydrocarbon seep environments.

  8. [Adaptive reactions of dehydrogenation processes in root voles during additional impacts of the physical nature].

    PubMed

    Kudiasheva, A G; Taskaev, A I

    2011-01-01

    Variations of the dehydrogenation enzyme activity (succinate dehydrogenase, pyruvate dehydrogenase, lactate dehydrogenase) in the heart muscle, liver and brain of root voles (Microtus oeconomus Pall.) and their progeny associated with additional stress effects (chronic low-level gamma-irradiation, short-term exposure to cold) have been studied. Root voles (parents) were caught in the areas with a normal and high-level natural radioactivity in the Republic of Komi. It has been revealed that the direction of shifts of the dehydrogenation enzyme activity in response to the factors of the physical nature is determined by the initial level of the oxidation process in tissues of root voles and their progeny that haven't been subjected to these actions. The reaction of root voles and their progeny (1-3 generations) from the radium zone has lower reserve functional possibilities in relation to the additional exposure as compared with the animals from the control zone. In some cases, chronic low-level irradiation and short-term cooling lead to leveling of differences between groups of animals which initially varied from each other in biochemical indexes. PMID:22279768

  9. Dehydrogenation processes via C-H activation within alkylphosphines.

    PubMed

    Grellier, Mary; Sabo-Etienne, Sylviane

    2012-01-01

    Phosphines are commonly used in organometallic chemistry and are present in a wide variety of catalytic systems. This feature article highlights the advances made in dehydrogenation processes occurring within alkylphosphines, with the aim of further developing catalytic processes involving C-H activation together with potential applications in the field of hydrogen storage. PMID:21956347

  10. Thermochemistry for the Dehydrogenation of Methyl Substituted Ammonia Borane Compounds

    SciTech Connect

    Grant, Daniel J.; Matus, Myrna H.; Anderson, Kevin; Camaioni, Donald M.; Neufeldt, Sharon; Lane, Clinton F.; Dixon, David A.

    2009-05-28

    Atomization energies at 0 K and heats of formation at 0 K and 298 K are predicted for (CH3)H2N-BH3, (CH3)HN=BH2, (BH3)HN=CH2, (CH3)H2B-NH3, (CH3)HB=NH2, and (NH3)HB=CH2, as well as various molecules involved in the different bond breaking processes, from coupled cluster theory (CCSD(T)) calculations. In order to achieve near chemical accuracy (±1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core CCSD(T) energies: corrections for core-valence, scalar relativistic, and first order atomic spin-orbit effects. Scaled vibrational zero point energies were computed with the MP2 method. The heats of formation were predicted for the respective dimethyl- and trimethyl- substituted ammonia boranes, their dehydrogenated derivatives, and the various molecules involved in the different bond breaking processes, based on isodesmic reaction schemes calculated at the G3(MP2) level. Thermodynamics for dehydrogenation pathways in the monomethyl substituted molecules were predicted. Dehydrogenation across the B-N bond is more favorable as opposed to dehydrogenation across the B-C and N-C bonds. Methylation at N reduces the exothermocity of the dehydrogenation reaction and makes the reaction more thermoneutral while methylation at B moves it away from thermoneutral. This work was supported by the US Department of Energy Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  11. Direct Dehydrogenation of n-Butane Over Pt/Sn/Zn-K/Al2O3 Catalyst: Effect of Hydrogen in the Feed.

    PubMed

    Lee, Jong Kwon; Seo, Hyun; Kim, Jeong Kwon; Seo, Hanuk; Cho, Hye-Ran; Lee, Jinsuk; Chang, Hosik; Song, In Kyu

    2016-05-01

    Al2O3 was prepared by a sol-gel method for use as a support. Pt/Sn/Zn-K/Al2O3 catalyst was then prepared by a sequential impregnation method, and it was applied to the direct dehydrogenation of n-butane to n-butenes and 1,3-butadiene. Physicochemical properties of Pt/Sn/Zn-K/Al2O3 catalyst were examined by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, inductively coupled plasma atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), CO chemisorption, and temperature-programmed oxidation (TPO) measurements. In order to improve the catalyst stability, the effect of hydrogen in the feed on the catalytic performance in the direct dehydrogenation of n-butane was studied. The catalyst stability and reusability in the direct dehydrogenation of n-butane was also investigated. Experimental results revealed that the addition of hydrogen in the feed decreased conversion of n-butane and yield for total dehydrogenation products but improved the stability of the catalyst. The catalytic activity and stability of regenerated Pt/Sn/Zn-K/Al2O3 catalyst in the presence of hydrogen slightly decreased compared to those of fresh Pt/Sn/Zn-K/Al2O3 catalyst due to the slight sintering of platinum particles. PMID:27483794

  12. Study on propane-butane gas storage by hydrate technology

    NASA Astrophysics Data System (ADS)

    Hamidi, Nurkholis; Wijayanti, Widya; Widhiyanuriyawan, Denny

    2016-03-01

    Different technology has been applied to store and transport gas fuel. In this work the storage of gas mixture of propane-butane by hydrate technology was studied. The investigation was done on the effect of crystallizer rotation speed on the formation of propane-butane hydrate. The hydrates were formed using crystallizer with rotation speed of 100, 200, and 300 rpm. The formation of gas hydrates was done at initial pressure of 3 bar and temperature of 274K. The results indicated that the higher rotation speed was found to increase the formation rate of propane-butane hydrate and improve the hydrates stability.

  13. Air stability of low-temperature dehydrogenation of Pd-decorated Mg blades.

    PubMed

    Liu, Yu; Wang, Gwo-Ching

    2012-01-20

    We demonstrated that Pd-decorated Mg blades are air-stable for hydrogen storage with a low desorption temperature of 373 K. Pd-catalyst-decorated Mg blades were prepared by 64° oblique incident angle thermal deposition on a rotatable substrate with the rotation axis perpendicular to the substrate. The hydrogen desorption from Pd-decorated Mg blades was performed and recorded by temperature-programmed desorption (TPD) for repeated hydrogenation–dehydrogenation cycles. The near-surface structural and compositional changes were characterized in situ by reflection high energy electron diffraction (RHEED). The Mg blades were intentionally exposed to air at elevated temperatures (333 or 358 K) between certain cycles. It was found that the degradation of the storage capacity was affected weakly by the air exposure at moderate temperatures. The kinetics of the hydrogen desorption was sensitive to air exposure but recoverable through a replenishment of fresh catalyst Pd on the surface of the oxidized Mg blades. PMID:22166731

  14. Reductive deprotonation and dehydrogenation of phenylhydrazine at a nickel center to give a nickel diazenido complex.

    PubMed

    Köthe, Claudia; Metzinger, Ramona; Herwig, Christian; Limberg, Christian

    2012-09-17

    The reaction of [L(tBu)Ni(OEt(2))] (where L(tBu) = [HC(C(t)BuNC(6)H(3)((i)Pr)(2))(2)](-)) with phenylhydrazine leads to the phenylhydrazido(1-) complex [L(tBu)Ni(η(2)-NPhNH(2))] (1) with concomitant formation of H(2). Treatment of 1 with potassium graphite in the presence of crown ether again leads to H(2) evolution and affords the heterobimetallic complex [L(tBu)Ni(μ-η(2):η(2)-NPhNH)]K(18-crown-6) containing the doubly deprotonated phenylhydrazido(2-) ligand. 1 can be converted into a phenyldiazenido complex [L(tBu)Ni(η(1)-NNPh)] in the course of a dehydrogenation reaction employing 1,2-diisopropylazo dicarboxylate (DIAD) as the oxidant. PMID:22950815

  15. Dehydrogenation of methanol to formaldehyde catalyzed by pristine and defective ceria surfaces.

    PubMed

    Beste, Ariana; Overbury, Steven H

    2016-04-21

    We have explored the dehydrogenation of methoxy on pristine and defective (111), (100), and (110) ceria surfaces with density functional methods. Methanol conversion is used as a probe reaction to understand structure sensitivity of the oxide catalysis. Differences in reaction selectivity have been observed experimentally as a function of crystallographically exposed faces and degree of reduction. We find that the barrier for carbon-hydrogen cleavage in methoxy is similar for the pristine and defective (111), (100), and (110) surfaces. However, there are large differences in the stability of the surface intermediates on the different surfaces. The variations in experimentally observed product selectivities are a consequence of the interplay between barrier controlled bond cleavage and desorption processes. Subtle differences in activation energies for carbon-hydrogen cleavage on the different crystallographic faces of ceria could not be correlated with structural or electronic descriptors. PMID:27005883

  16. Dehydrogenation of methanol to formaldehyde catalyzed by pristine and defective ceria surfaces

    DOE PAGESBeta

    Beste, Ariana; Overbury, Steven H.

    2016-03-09

    We have explored the dehydrogenation of methoxy on pristine and defective (111), (100), and (110) ceria surfaces with density functional methods. Methanol conversion is used as a probe reaction to understand structure sensitivity of the oxide catalysis. Differences in reaction selectivity have been observed experimentally as a function of crystallographically exposed faces and degree of reduction. We find that the barrier for carbon-hydrogen cleavage in methoxy is similar for the pristine and defective (111), (100), and (110) surfaces. However, there are large differences in the stability of the surface intermediates on the different surfaces. The variations in experimentally observed productmore » selectivities are a consequence of the interplay between barrier controlled bond cleavage and desorption processes. Ultimately, subtle differences in activation energies for carbon-hydrogen cleavage on the different crystallographic faces of ceria could not be correlated with structural or electronic descriptors.« less

  17. Subcritical extraction of flaxseed oil with n-propane: Composition and purity.

    PubMed

    Zanqui, Ana Beatriz; de Morais, Damila Rodrigues; da Silva, Claudia Marques; Santos, Jandyson Machado; Gomes, Sandra Terezinha Marques; Visentainer, Jesuí Vergílio; Eberlin, Marcos Nogueira; Cardozo-Filho, Lúcio; Matsushita, Makoto

    2015-12-01

    Flaxseed (Linum usitatissimum L.) oil was obtained via subcritical n-propane fluid extraction (SubFE) under different temperatures and pressures with an average yield of 28% and its composition, purity and oxidative stability were compared to oils obtained via conventional solvent extraction methods (SEMs). When the oxidative stability was measured by differential scanning calorimetry, the oil was found to be up to 5 times more resistant to lipid oxidation as compared to the SEM oils. Direct infusion electrospray ionization mass spectrometry (ESI-MS) analysis showed characteristic and similar TAG profiles for SubFE and SEMs oils but higher purity for the SubFE oil. The flaxseed oil content of β-tocopherol, campesterol, stigmasterol and sitosterol were quantified via GC-MS. SubFE showed to be a promising alternative to conventional SEM since SubFE provides an oil with higher purity and higher oxidation stability and with comparable levels of biologically active components. PMID:26041217

  18. Recoverable Pd/C catalyst mediated dehydrogenation of sterols and an improved synthesis of 1α-hydroxydehydroepiandrosterone.

    PubMed

    Yin, Yi-Zhen; Liu, Chao; Tang, Long-Qian; Liu, Zhao-Peng

    2012-11-01

    A novel recyclable Pd/C catalyst mediated dehydrogenation of sterols is developed. The conversion of sterols to 1,4,6-trien-3-ones is best achieved with Pd/C as a catalyst (10%) in the presence of six equivalents of allyl diethyl phosphate (ADP) and excess amount of sodium carbonate in DMF under vigorous reflux conditions. This transformation gives 17,17-ethylenedioxyandrost-1,4,6-trien-3-one in better yield than that of DDQ oxidation and thus provides an improved synthesis of 1α-hydroxydehydroepiandrosterone from DHEA. PMID:23000152

  19. In situ XPS investigation of Pt(Sn)/Mg(Al)O catalysts during ethane dehydrogenation experiments

    NASA Astrophysics Data System (ADS)

    Virnovskaia, Anastasia; Jørgensen, Sissel; Hafizovic, Jasmina; Prytz, Øystein; Kleimenov, Evgueni; Hävecker, Michael; Bluhm, Hendrik; Knop-Gericke, Axel; Schlögl, Robert; Olsbye, Unni

    2007-01-01

    Calcined hydrotalcite with or without added metal (Mg(Al)O, Pt/Mg(Al)O and Pt,Sn/Mg(Al)O) have been investigated with in situ X-ray photoelectron spectroscopy (XPS) during ethane dehydrogenation experiments. The temperature in the analysis chamber was 450 °C and the gas pressure was in the range 0.3-1 mbar. Depth profiling of calcined hydrotalcite and platinum catalysts under reaction, oxidation and in hydrogen-water mixture was performed by varying the photon energy, covering an analysis depth of 10-21 Å. It was observed that the Mg/Al ratio in the Mg(Al)O crystallites does not vary significantly in the analysis depth range studied. This result indicates that Mg and Al are homogeneously distributed in the Mg(Al)O crystallites. Catalytic tests have shown that the initial activity of a Pt,Sn/Mg(Al)O catalyst increases during an activation period consisting of several cycles of reduction-dehydrogenation-oxidation. The Sn/Mg ratio in a Pt,Sn/Mg(Al)O catalyst was followed during several such cycles, and was found to increase during the activation period, probably due to a process where tin spreads over the carrier material and covers an increasing fraction of the Mg(Al)O surface. The results further indicate that spreading of tin occurs under reduction conditions. A PtSn 2 alloy was studied separately. The surface of the alloy was enriched in Sn during reduction and reaction conditions at 450 °C. Binding energies were determined and indicated that Sn on the particle surface is predominantly in an oxidised state under reaction conditions, while Pt and a fraction of Sn is present as a reduced Pt-Sn alloy.

  20. Temperature-dependent high resolution absorption cross sections of propane

    NASA Astrophysics Data System (ADS)

    Beale, Christopher A.; Hargreaves, Robert J.; Bernath, Peter F.

    2016-10-01

    High resolution (0.005 cm-1) absorption cross sections have been measured for pure propane (C3H8). These cross sections cover the 2550-3500 cm-1 region at five temperatures (from 296 to 700 K) and were measured using a Fourier transform spectrometer and a quartz cell heated by a tube furnace. Calibrations were made by comparison to the integrated cross sections of propane from the Pacific Northwest National Laboratory. These are the first high resolution absorption cross sections of propane for the 3 μm region at elevated temperatures. The cross sections provided may be used to monitor propane in combustion environments and in astronomical sources such as the auroral regions of Jupiter, brown dwarfs and exoplanets.

  1. PREDICTIONS OF AZEOTROPES FORMED FROM FLUORINATED ETHERS, ETHANES, AND PROPANES

    EPA Science Inventory

    The paper discusses an evaluation of the potential for azeotrope formation and performance for fluorinated ethers, ethanes, and propanes. (NOTE: The synthesis of new non-chlorinated refrigerants expands the base of alternatives for replacing ozone-depleting chlorofluorocarbons (O...

  2. Paramagnetic titanium(III) and zirconium(III) metallocene complexes as precatalysts for the dehydrocoupling/dehydrogenation of amine-boranes.

    PubMed

    Helten, Holger; Dutta, Barnali; Vance, James R; Sloan, Matthew E; Haddow, Mairi F; Sproules, Stephen; Collison, David; Whittell, George R; Lloyd-Jones, Guy C; Manners, Ian

    2013-01-01

    Complexes of Group 4 metallocenes in the +3 oxidation state and amidoborane or phosphidoborane function as efficient precatalysts for the dehydrocoupling/dehydrogenation of amine-boranes, such as Me(2) NH⋅BH(3). Such Ti(III) -amidoborane complexes are generated in [Cp(2)Ti]-catalyzed amine-borane dehydrocoupling reactions, for which diamagnetic M(II) and M(IV) species have been previously postulated as precatalysts and intermediates. PMID:23197391

  3. Oxygenative and Dehydrogenative [3 + 3] Benzannulation Reactions of α,β-Unsaturated Aldehydes and γ-Phosphonyl Crotonates Mediated by Air: Regioselective Synthesis of 4-Hydroxybiaryl-2-carboxylates.

    PubMed

    Joshi, Prabhakar Ramchandra; Nanubolu, Jagadeesh Babu; Menon, Rajeev S

    2016-02-19

    Regioselective synthesis of 4-hydroxybiphenyl-2-carboxylates via the base-mediated oxygenative [3 + 3] benzannulation reaction of α,β-unsaturated aldehydes and γ-phosphonyl crotonates is reported. A hydroxyl group is installed in the final product on the originally phosphorus-bound carbon via a novel oxygenative and dehydrogenative transformation. The reaction proceeds rapidly in an open flask, uses atmospheric oxygen as an oxidant, and affords good yields of substituted biaryl phenols. PMID:26859060

  4. An economical synthesis of substituted quinoline-2-carboxylates through the potassium persulfate-mediated cross-dehydrogenative coupling of N-aryl glycine derivatives with olefins.

    PubMed

    Liu, Guoliang; Qian, Jiarui; Hua, Jing; Cai, Feng; Li, Xia; Liu, Lei

    2016-01-21

    A practical and economical K2S2O8-mediated oxidative cross-dehydrogenative coupling of N-aryl glycine derivatives with olefins has been established, affording structurally diverse quinoline-2-carboxylates in good to high efficiency. The low cost, negligible toxicity, and ease of handling of K2S2O8 combined with the absence of hazardous byproducts and the easy workup consisting of simple filtration are attractive based on economic and environmental factors. PMID:26645648

  5. Thermochemical Energy Storage through De/Hydrogenation of Organic Liquids: Reactions of Organic Liquids on Metal Hydrides.

    PubMed

    Ulmer, Ulrich; Cholewa, Martin; Diemant, Thomas; Bonatto Minella, Christian; Dittmeyer, Roland; Behm, R Jürgen; Fichtner, Maximilian

    2016-06-01

    A study of the reactions of liquid acetone and toluene on transition metal hydrides, which can be used in thermal energy or hydrogen storage applications, is presented. Hydrogen is confined in TiFe, Ti0.95Zr0.05Mn1.49V0.45Fe0.06 ("Hydralloy C5"), and V40Fe8Ti26Cr26 after contact with acetone. Toluene passivates V40Fe8Ti26Cr26 completely for hydrogen desorption while TiFe is only mildly deactivated and desorption is not blocked at all in the case of Hydralloy C5. LaNi5 is inert toward both organic liquids. Gas chromatography (GC) investigations reveal that CO, propane, and propene are formed during hydrogen desorption from V40Fe8Ti26Cr26 in liquid acetone, and methylcyclohexane is formed in the case of liquid toluene. These reactions do not occur if dehydrogenated samples are used, which indicates an enhanced surface reactivity during hydrogen desorption. Significant amounts of carbon-containing species are detected at the surface and subsurface of acetone- and toluene-treated V40Fe8Ti26Cr26 by X-ray photoelectron spectroscopy (XPS). The modification of the surface and subsurface chemistry and the resulting blocking of catalytic sites is believed to be responsible for the containment of hydrogen in the bulk. The surface passivation reactions occur only during hydrogen desorption of the samples. PMID:27183004

  6. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    PubMed Central

    Christensen, Rasmus Bjerregaard; Lü, Jing-Tao; Hedegård, Per

    2016-01-01

    Summary We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces. PMID:26925354

  7. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons.

    PubMed

    Christensen, Rasmus Bjerregaard; Lü, Jing-Tao; Hedegård, Per; Brandbyge, Mads

    2016-01-01

    We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces. PMID:26925354

  8. Synthesis, structure and the dehydrogenation mechanism of calcium amidoborane hydrazinates.

    PubMed

    Li, Zhao; He, Teng; Wu, Guotao; Chen, Weidong; Chua, Yong Shen; Guo, Jianping; Xie, Dong; Ju, Xiaohua; Chen, Ping

    2016-01-01

    The calcium amidoborane hydrazinates, Ca(NH2BH3)2·nN2H4, were firstly synthesized by reacting different molar ratios of Ca(NH2BH3)2 and N2H4. In particular, Ca(NH2BH3)2 and N2H4 with a molar ratio of 1 : 2 crystallizes into the orthorhombic symmetry P212121 space group with the lattice parameters of a = 6.6239(4) Å, b = 13.7932(6) Å, c = 4.7909(2) Å. The dehydrogenations of calcium amidoborane hydrazinates are two-step reactions, exhibiting superior dehydrogenation properties compared with those of pristine Ca(NH2BH3)2. For Ca(NH2BH3)2-1/2N2H4, approximately 4.6 equiv. hydrogen (or 7.9 wt% hydrogen) can be released at 150 °C. Kinetic analysis shows that the activation energies for the two steps of hydrogen desorption from Ca(NH2BH3)2·2N2H4 are much lower than those of pristine Ca(NH2BH3)2, suggesting an improvement in the dehydrogenation kinetics of Ca(NH2BH3)2 after coordinating with N2H4. Isotopic labeling results show that the driving force for the dehydrogenation of calcium amidoborane hydrazinates is the combination mechanism of protonic hydrogen and hydridic hydrogen (H(δ+) and H(δ-)). In addition, initial H2 release from calcium amidoborane hydrazinates originates from the interaction of [-BH3] and N2H4, rather than [-BH3] and [-NH2] (in [-NH2BH3]). PMID:26608171

  9. Emission measurements for a lean premixed propane/air system at pressures up to 30 atmospheres

    NASA Technical Reports Server (NTRS)

    Roffe, G.; Venkataramani, K. S.

    1978-01-01

    The emissions of a lean premixed system of propane/air were measured in a flametube apparatus. Tests were conducted at inlet temperatures of 600K and 800K and pressures of 10 atm and 30 atm over a range of equivalence ratios. The data obtained were combined with previous data taken in the same apparatus to correlate nitrogen oxide emissions with operating conditions. Sampling probe design was found to have a pronounced effect on measured CO levels but did not influence measurements. The most effective probe tested was one which combined thermal and pressure quenching of the gas sample.

  10. Donor-acceptor complexation and dehydrogenation chemistry of aminoboranes.

    PubMed

    Malcolm, Adam C; Sabourin, Kyle J; McDonald, Robert; Ferguson, Michael J; Rivard, Eric

    2012-12-01

    A series of formal donor-acceptor adducts of aminoborane (H(2)BNH(2)) and its N-substituted analogues (H(2)BNRR') were prepared: LB-H(2)BNRR'(2)-BH(3) (LB = DMAP, IPr, IPrCH(2) and PCy(3); R and R' = H, Me or tBu; IPr = [(HCNDipp)(2)C:] and Dipp = 2,6-iPr(2)C(6)H(3)). To potentially access complexes of molecular boron nitride, LB-BN-LA (LA = Lewis acid), preliminary dehydrogenation chemistry involving the parent aminoborane adducts LB-H(2)BNH(2)-BH(3) was investigated using [Rh(COD)Cl](2), CuBr, and NiBr(2) as dehydrogenation catalysts. In place of isolating the intended dehydrogenated BN donor-acceptor complexes, the formation of borazine was noted as a major product. Attempts to prepare the fluoroarylborane-capped aminoborane complexes, LB-H(2)BNH(2)-B(C(6)F(5))(3), are also described. PMID:23153209

  11. Structure and molecular interactions in {ethanol + (propan-1-ol/propan-2-ol)} mixtures at 303.15 K

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Puyad, A. L.

    2014-06-01

    In view of industrial importance of binary {ethyl alcohol + (propan-1-ol/propan-2-ol)} mixtures, the densities (ρ) and refractive indices ( n D ) of these alkanols mixtures were measured for different compositions at 303.15 K. Molar volumes ( V m) and excess molar volumes ( V E) of these binary mixtures were calculated from experimental density data of pure solvents and solvents mixtures. The measured refractive index and density data was used to calculate specific refractions ( R D ), molar refractions ( R M) and apparent molar refractions ( R φ, i ) of binary mixtures. From mole fraction dependence of apparent molar refractions, the limiting apparent molar refractions ( R {φ,/i ○}) of propan-1-ol and propan-2-ol have been determined. The graphical values of R {φ,/i ○} for propan-1-ol and propan-2-ol were found to be 9.5664 and 7.405 cm3 mol-1 respectively. Structural changes, geometrical fittings and molecular interactions in binary mixtures of these alkanols have been discussed.

  12. Evaluation of various models of propane-powered mosquito traps.

    PubMed

    Kline, Daniel L

    2002-06-01

    Large cage and field studies were conducted to determine the efficacy of various models of propane-powered mosquito traps. These traps utilized counterflow technology in conjunction with catalytic combustion to produce attractants (carbon dioxide, water vapor, and heat) and a thermoelectric generator that converted excess heat into electricity for stand-alone operation. The cage studies showed that large numbers of Aedes aegypti and Ochlerotatus taeniorhynchus were captured and that each progressive model resulted in increased trapping efficiency. In several field studies against natural populations of mosquitoes two different propane traps were compared against two other trap systems, the professional (PRO) and counterflow geometry (CFG) traps. In these studies the propane traps consistently caught more mosquitoes than the PRO trap and significantly fewer mosquitoes than the CFG traps. The difference in collection size between the CFG and propane traps was due mostly to Anopheles crucians. In spring 1997 the CFG trap captured 3.6X more An. crucians than the Portable Propane (PP) model and in spring 1998 it captured 6.3X more An. crucians than the Mosquito Magnet Beta-1 (MMB-1) trap. Both the PP and MMB-1 captured slightly more Culex spp. than the CFG trap. PMID:12125861

  13. Buckyball-, carbon nanotube-, graphite-, and graphene-enhanced dehydrogenation of lithium aluminum hydride.

    PubMed

    Hsu, Chih-Ping; Jiang, De-hao; Lee, Sheng-Long; Horng, Jain-Long; Ger, Ming-Der; Chang, Jeng-Kuei

    2013-10-01

    Compared to C60, carbon nanotubes, and graphite, graphene more effectively lowers the dehydrogenation temperature and improves the dehydrogenation kinetics of LiAlH4. With 15 wt% graphene incorporation, the initial hydrogen release temperature is ~80 °C (60 °C lower than that of pristine LiAlH4). PMID:23958824

  14. Pressure-enhanced dehydrogenation reaction of the LiBH4-YH3 composite.

    PubMed

    Kim, Kee-Bum; Shim, Jae-Hyeok; Cho, Young Whan; Oh, Kyu Hwan

    2011-09-21

    The increase in hydrogen back pressure unexpectedly enhances the overall dehydrogenation reaction rate of the 4LiBH(4) + YH(3) composite significantly. Also, argon back pressure has a similar influence on the composite. Gas back pressure seems to enhance the dehydrogenation reaction by kinetically suppressing the formation of the diborane by-product. PMID:21811726

  15. An engineered pathway for the biosynthesis of renewable propane

    PubMed Central

    Kallio, Pauli; Pásztor, András; Thiel, Kati; Akhtar, M. Kalim; Jones, Patrik R.

    2014-01-01

    The deployment of next-generation renewable biofuels can be enhanced by improving their compatibility with the current infrastructure for transportation, storage and utilization. Propane, the bulk component of liquid petroleum gas, is an appealing target as it already has a global market. In addition, it is a gas under standard conditions, but can easily be liquefied. This allows the fuel to immediately separate from the biocatalytic process after synthesis, yet does not preclude energy-dense storage as a liquid. Here we report, for the first time, a synthetic metabolic pathway for producing renewable propane. The pathway is based on a thioesterase specific for butyryl-acyl carrier protein (ACP), which allows native fatty acid biosynthesis of the Escherichia coli host to be redirected towards a synthetic alkane pathway. Propane biosynthesis is markedly stimulated by the introduction of an electron-donating module, optimizing the balance of O2 supply and removal of native aldehyde reductases. PMID:25181600

  16. An engineered pathway for the biosynthesis of renewable propane.

    PubMed

    Kallio, Pauli; Pásztor, András; Thiel, Kati; Akhtar, M Kalim; Jones, Patrik R

    2014-01-01

    The deployment of next-generation renewable biofuels can be enhanced by improving their compatibility with the current infrastructure for transportation, storage and utilization. Propane, the bulk component of liquid petroleum gas, is an appealing target as it already has a global market. In addition, it is a gas under standard conditions, but can easily be liquefied. This allows the fuel to immediately separate from the biocatalytic process after synthesis, yet does not preclude energy-dense storage as a liquid. Here we report, for the first time, a synthetic metabolic pathway for producing renewable propane. The pathway is based on a thioesterase specific for butyryl-acyl carrier protein (ACP), which allows native fatty acid biosynthesis of the Escherichia coli host to be redirected towards a synthetic alkane pathway. Propane biosynthesis is markedly stimulated by the introduction of an electron-donating module, optimizing the balance of O2 supply and removal of native aldehyde reductases. PMID:25181600

  17. Photocatalytic acceptorless alkane dehydrogenation: scope, mechanism, and conquering deactivation with carbon dioxide.

    PubMed

    Chowdhury, Abhishek Dutta; Julis, Jennifer; Grabow, Kathleen; Hannebauer, Bernd; Bentrup, Ursula; Adam, Martin; Franke, Robert; Jackstell, Ralf; Beller, Matthias

    2015-01-01

    Alkane dehydrogenation is of special interest for basic science but also offers interesting opportunities for industry. The existing dehydrogenation methodologies make use of heterogeneous catalysts, which suffer from harsh reaction conditions and a lack of selectivity, whereas homogeneous methodologies rely mostly on unsolicited waste generation from hydrogen acceptors. Conversely, acceptorless photochemical alkane dehydrogenation in the presence of trans-Rh(PMe3 )2 (CO)Cl can be regarded as a more benign and atom efficient alternative. However, this methodology suffers from catalyst deactivation over time. Herein, we provide a detailed investigation of the trans-Rh(PMe3 )2 (CO)Cl-photocatalyzed alkane dehydrogenation using spectroscopic and theoretical investigations. These studies inspired us to utilize CO2 to prevent catalyst deactivation, which leads eventually to improved catalyst turnover numbers in the dehydrogenation of alkanes that include liquid organic hydrogen carriers. PMID:25346450

  18. Interest in propane futures appears to be growing

    SciTech Connect

    Not Available

    1992-12-01

    The last couple of decades have seen significant and sometimes abrupt change sin world energy markets and prices. In addition to regional politics, war, and changing economic patterns, the energy industry has undergone structural changes that have increased price and supply stability. This paper reports that these changes have filtered through the energy industry to the LPG market giving many in the industry a reason to use the propane futures market. The current operative market is run by the New York Mercantile Exchange (NYMEX). Started up in 1987, this propane futures market is much more successful than its predecessors.

  19. [Frostbite injuries causing compromised airway after inhalation of propane].

    PubMed

    Straarup, Therese Simonsen; Fink, Anders Olsen; Larsen, Jens Kjærgaard Rolighed

    2015-01-01

    We describe a case report of a 23-year-old man with acute pharyngeal injuries due to frostbite subsequent to inhalation of propane. He was fiber-optically intubated on admission to hospital since his airways were considered acutely compromised. He was subsequently kept intubated for 11 days due to persistent pharyngeal oedema and frostbite injuries. The latter is caused by low temperature of propane upon release from a pressurized container. Injuries caused by frostbite often gradually progress and thus caution should be exerted in regards to airway management. PMID:25557449

  20. Emissions measurements for a lean premixed propane/air system at pressures up to 30 atmospheres

    NASA Technical Reports Server (NTRS)

    Roffe, G.

    1979-01-01

    A series of experiments was conducted in which the emissions of a lean premixed system of propane and air were measured at pressures of 5, 10, 20 and 30 atm in a flametube apparatus. Measurements were made for inlet temperatures between 600K and 1000K and combustor residence times from 1.0 to 3.0 msec. A schematic of the test rig is presented along with graphs showing emissions measurements for nitric oxide, carbon monoxide, and UHC as functions of bustor residence time for various equivalence ratios, entrance temperatures and pressures; typical behavior of emissions as a function of equivalence ratio for a fixed residence time. Correlations of nitric oxide emission index with adiabatic flame temperature for a fixed residence time of 2 msec and pressures from 5 to 30 atm; and adiabatic flame temperature corresponding to CO breakpoint conditions for 2 msec residence time as a function of inlet temperature.

  1. Long-lived excited states of zwitterionic copper(I) complexes for photoinduced cross-dehydrogenative coupling reactions.

    PubMed

    Wang, Bin; Shelar, Deepak Prakash; Han, Xian-Zhu; Li, Ting-Ting; Guan, Xiangguo; Lu, Wei; Liu, Kun; Chen, Yong; Fu, Wen-Fu; Che, Chi-Ming

    2015-01-12

    Four heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido-carborane-diphosphine ligands have been prepared and structurally characterized by various spectroscopic techniques and X-ray diffraction. These complexes exhibit intense absorptions in the visible range and excited-state lifetimes on the microsecond scale. Their application in visible-light-induced cross-dehydrogenative coupling reactions was investigated. Preliminary studies showed that one of the four copper(I) complexes is an efficient catalyst for photoinduced oxidative C-H functionalization using oxygen as oxidant. Furthermore, α-functionalized tertiary amines were obtained in good-to-excellent yields by light irradiation (λ>420 nm) of a mixture of our Cu(I) complex, tertiary amines, and a variety of nucleophiles (nitroalkane, acetone, or indoles) under aerobic conditions. Electron paramagnetic resonance measurements provided evidence for the formation of superoxide radical anions (O2(-⋅)) rather than singlet oxygen ((1)O2) during these photocatalytic reactions. PMID:25413572

  2. Active site density and reactivity for the photocatalytic dehydrogenation of 2-propanol on TiO 2 (110)

    NASA Astrophysics Data System (ADS)

    Brinkley, David; Engel, Thomas

    1998-10-01

    By combining molecular beam experiments at 350 K with low temperature experiments on an immobile adlayer, we determine the fraction of surface sites active for the photocatalytic dehydrogenation of 2-propanol to acetone to be 0.08 on a fully oxidized surface. We also find that the reaction probability at these sites is essentially unity. The presence of oxygen vacancies (≈0.1 monolayer) increases the fraction of active sites to 0.15 without changing the reaction probability, reaction kinetics, or product distribution. From this, we conclude that only sites which can bind O 2 strongly are active for the reaction. Candidates for such sites include steps and kinks on fully oxidized surfaces and oxygen lattice vacancies on reduced surfaces.

  3. Synthesis, thermal behavior, and dehydrogenation kinetics study of lithiated ethylenediamine.

    PubMed

    Chen, Juner; Wu, Guotao; Xiong, Zhitao; Wu, Hui; Chua, Yong Shen; Zhou, Wei; Liu, Bin; Ju, Xiaohua; Chen, Ping

    2014-10-13

    The lithiation of ethylenediamine by LiH is a stepwise process to form the partially lithiated intermediates LiN(H)CH2 CH2 NH2 and [LiN(H)CH2 CH2 NH2 ][LiN(H)CH2 CH2 N(H)Li]2 prior to the formation of dilithiated ethylenediamine LiN(H)CH2 CH2 N(H)Li. A reversible phase transformation between the partial and dilithiated species was observed. One dimensional {Lin Nn } ladders and three-dimensional network structures were found in the crystal structures of LiN(H)CH2 CH2 NH2 and LiN(H)CH2 CH2 N(H)Li, respectively. LiN(H)CH2 CH2 N(H)Li undergoes dehydrogenation with an activation energy of 181±8 kJ mol(-1) , whereas the partially lithiated ethylenediamine compounds were polymerized and released ammonia at elevated temperatures. The dynamical dehydrogenation mechanism of the dilithiated ethylenediamine compounds was investigated by using the Johnson-Mehl-Avrami equation. PMID:25164593

  4. Promoted dehydrogenation in ammine lithium borohydride supported by carbon nanotubes.

    PubMed

    Chen, Xinyi; Li, Shaofeng; Guo, Yanhui; Yu, Xuebin

    2011-10-14

    In this paper, ammine lithium borohydride (LiBH(4)·NH(3)) was successfully impregnated into multi-walled carbon nanotubes (CNTs) through a melting technique. X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller, and density measurements were employed to confirm the formation of the nanostructured LiBH(4)·NH(3)/CNTs composites. As a consequence, it was found that the dehydrogenation of the loaded LiBH(4)·NH(3) was remarkably enhanced, showing an onset dehydrogenation at temperatures below 100 °C, together with a prominent desorption of pure hydrogen at around 280 °C, with a capacity as high as 6.7 wt.%, while only a trace of H(2) liberation was present for the pristine LiBH(4)·NH(3) in the same temperature range. Structural examination indicated that the significant modification of the thermal decomposition route of LiBH(4)·NH(3) achieved in the present study is due to the CNT-assisted formation of B-N-based hydride composite, starting at a temperature below 100 °C. It is demonstrated that the formation of this B-N-based hydride covalently stabilized the [NH] groups that were weakly coordinated on Li cations in the pristine LiBH(4)·NH(3)via strong B-N bonds, and furthermore, accounted for the substantial hydrogen desorption at higher temperatures. PMID:21850349

  5. Pincer and diamine Ru and Os diphosphane complexes as efficient catalysts for the dehydrogenation of alcohols to ketones.

    PubMed

    Baratta, Walter; Bossi, Gianluca; Putignano, Elisabetta; Rigo, Pierluigi

    2011-03-14

    The ruthenium and osmium complexes [MCl(2)(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4-bis-(diphenylphosphino)butane), containing the N−H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans-[MCl(2)(dppf)(en)] (M=Ru 7, Os 13; dppf=1,1'-bisdiphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8-0.04 mol % of catalyst. The effect of the base and the comparison of the catalytic activity of the Ru versus Os complexes are reported. The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13, which displays better activity in the dehydrogenation of 5-en-3β-hydroxy steroids. The synthesis of new Ru and Os complexes [MCl(2)(PP)(L)] (PP=dppb, dppf; L=(±)-trans-1,2-diaminocyclohexane,2-(aminomethyl)pyridine, and 2-aminoethanol) of trans and cis configuration is also reported. PMID:21341330

  6. Aqueous solution synthesis of Pt-M (M = Fe, Co, Ni) bimetallic nanoparticles and their catalysis for the hydrolytic dehydrogenation of ammonia borane.

    PubMed

    Wang, Shuai; Zhang, Duo; Ma, Yanyun; Zhang, Hui; Gao, Jing; Nie, Yuting; Sun, Xuhui

    2014-08-13

    Platinum-based bimetallic nanocatalysts have attracted much attention due to their high-efficiency catalytic performance in energy-related applications such as fuel cell and hydrogen storage, for example, the hydrolytic dehydrogenation of ammonia borane (AB). In this work, a simple and green method has been demonstrated to successfully prepare Pt-M (M = Fe, Co, Ni) NPs with tunable composition (nominal Pt/M atomic ratios of 4:1, 1:1, and 1:4) in aqueous solution under mild conditions. All Pt-M NPs with a small size of 3-5 nm show a Pt fcc structure, suggesting the bimetallic formation (alloy and/or partial core-shell), examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analysis. The catalytic activities of Pt-M NPs in the hydrolytic dehydrogenation of AB reveal that Pt-Ni NPs with a ratio of 4:1 show the best catalytic activity and even better than that of pure Pt NPs when normalized to Pt molar amount. The Ni oxidation state in Pt-Ni NPs has been suggested to be responsible for the corresponding catalytic activity for hydrolytic dehydrogenation of AB by XAFS study. This strategy for the synthesis of Pt-M NPs is simple and environmentally benign in aqueous solution with the potential for scale-up preparation and the in situ catalytic reaction. PMID:25058566

  7. Diffusion of 2-iodo-propane (1); helium (2)

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 2-iodo-propane; (2) helium

  8. Diffusion of 1-iodo-propane (1); air (2)

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 1-iodo-propane; (2) air

  9. Diffusion of 2-iodo-propane (1); air (2)

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 2-iodo-propane; (2) air

  10. Diffusion of 1-iodo-propane (1); helium (2)

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 1-iodo-propane; (2) helium

  11. Zeolitic imidazolate frameworks for kinetic separation of propane and propene

    DOEpatents

    Li, Jing; Li, Kunhao; Olson, David H.

    2014-08-05

    Zeolitic Imidazolate Frameworks (ZIFs) characterized by organic ligands consisting of imidazole ligands that are either essentially all 2-chloroimidazole ligands or essentially all 2-bromoimidazole ligands are disclosed. Methods for separating propane and propene with the ZIFs of the present invention, as well as other ZIFs, are also disclosed.

  12. Dehydrogenation and dehalogenation of amines in MALDI-TOF MS investigated by isotopic labeling.

    PubMed

    Kang, Chuanqing; Zhou, Yihan; Du, Zhijun; Bian, Zheng; Wang, Jianwei; Qiu, Xuepeng; Gao, Lianxun; Sun, Yuequan

    2013-12-01

    Secondary and tertiary amines have been reported to form [M-H](+) that correspond to dehydrogenation in matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). In this investigation, we studied the dehydrogenation of amines in MALDI-TOF MS by isotopic labeling. Aliphatic amines were labeled with deuterium on the methylene of an N-benzyl group, which resulted in the formation of [M-D](+) and [M-H](+) ions by dedeuteration and dehydrogenation, respectively. This method revealed the proton that was removed. The spectra of most tertiary amines with an N-benzyl group showed high-intensity [M-D](+) and [M-H](+) ion peaks, whereas those of secondary amines showed low-intensity ion peaks. Ratios between the peak intensities of [M-D](+) and [M-H](+) greater than 1 suggested chemoselective dehydrogenation at the N-benzyl groups. The presence of an electron donor group on the N-benzyl groups enhanced the selectivity. The dehalogenation of amines with an N-(4-halobenzyl) group was also observed alongside dehydrogenation. The amino ions from dehalogenation can undergo second dehydrogenation. These results provide the first direct evidence about the position at which dehydrogenation of an amine occurs and the first example of dehalogenation of haloaromatic compounds in MALDI-TOF MS. These results should be helpful in the structural identification and elucidation of synthetic and natural molecules. PMID:24338887

  13. Microstructural analysis of dehydrogenation products of the Ca(BH₄)₂-MgH₂ composite.

    PubMed

    Kim, Jong-Min; Kim, Yoonyoung; Shim, Jae-Hyeok; Lee, Young-Su; Suh, Jin-Yoo; Ahn, Jae-Pyoung; Kim, Gyeung-Ho; Cho, Young Whan

    2013-08-01

    The microstructural analysis of the dehydrogenation products of the Ca(BH₄)₂-MgH₂ composite was performed using transmission electron microscopy. It was found that nanocrystalline CaB₆ crystallites formed as a dehydrogenation product throughout the areas where the signals of Ca and Mg were simultaneously detected, in addition to relatively coarse Mg crystallites. The uniform distribution of the nanocrystalline CaB₆ crystallites appears to play a key role in the rehydrogenation of the dehydrogenation products, which implies that microstructure is a crucial factor determining the reversibility of reactive hydride composites. PMID:23920195

  14. The hydrogenation and dehydrogenation of C{sub 2}-C{sub 4} hydrocarbons on Pt(111) monitored in situ over 13 orders of magnitude in pressure with infrared-visible sum frequency generation

    SciTech Connect

    Cremer, P.S.

    1996-05-01

    The hydrogenation and dehydrogenation of ethylene, propylene, and isobutene were monitored in situ during heterogeneous catalysis over Pt(111) between 10{sup -10} Torr and 1000 Torr with infrared-visible sum frequency generation (SFG). SFG is a surface specific vibrational spectroscopy capable of achieving submonolayer sensitivity under reaction conditions in the presence of hundreds of Toff of reactants and products. Olefin dehydrogenation experiments were carried out with SFG under ultra high vacuum (UHV) conditions on the (111) crystal face of platinum Ethylene chemisorbed on Pt(111) below 230 K in the di-{sigma} bonded conformation (Pt-CH{sub 2}CH{sub 2}-Pt). Upon annealing the system to form the dehydrogenation product, ethylidyne (M=CCH{sub 3}), evidence was found for an ethylidene intermediate (M=CHCH{sub 3}) from its characteristic v{sub as}(CH{sub 3}) near 2960 cm{sup -1}. Hydrogenation of ethylene was carried out between 1 Toff and 700 Torr of H{sub 2} while the vibrational spectrum of surface species was monitored with SFG. Simultaneously, gas chromatography was used to obtain the turnover rate for the catalytic reaction, which could be correlated with the adsorbed intermediate concentration to determine the reaction rate per surface intermediate. Di-{sigma} bonded ethylene, {pi}-bonded ethylene, ethyl groups and ethylidyne resided on the surface during reaction. The mechanistic pathway for ethylene hydrogenation involved the stepwise hydrogenation of {pi}-bonded ethylene through an ethyl intermediate to ethane. The hydrogenation of propylene was carried out under the same conditions as ethylene. It was found that propylene hydrogenates from {pi}-bonded propylene through a 2-propyl intermediate to propane on Pt(111). The rate of reaction was approximately 50% slower than that of ethylene hydrogenation. Isobutene, however, was found to hydrogenate almost two order of magnitude slower than propylene on Pt(111).

  15. Drosophila melanogaster alcohol dehydrogenase: mechanism of aldehyde oxidation and dismutation.

    PubMed

    Winberg, J O; McKinley-McKee, J S

    1998-02-01

    Drosophila alcohol dehydrogenase (Adh) catalyses the oxidation of both alcohols and aldehydes. In the latter case, the oxidation is followed by a reduction of the aldehyde, i.e. a dismutation reaction. At high pH, dismutation is accompanied by a small release of NADH, which is not observed at neutral pH. Previously it has been emphasized that kinetic coefficients obtained by measuring the increase in A340, i.e. the release of NADH at high pH is not a direct measure of the aldehyde oxidation reaction and these values cannot be compared with those for alcohol dehydrogenation. In this article we demonstrate that this is not entirely true, and that the coefficients phiB and phiAB, where B is the aldehyde and A is NAD+, are the same for a dismutation reaction and a simple aldehyde dehydrogenase reaction. Thus the substrate specificity of the aldehyde oxidation reaction can be determined by simply measuring the NADH release. The coefficients for oxidation and dehydrogenation reactions (phi0d and phiAd respectively) are complex and involve the constants for the dismutation reaction. However, dead-end inhibitors can be used to determine the quantitative contribution of the kinetic constants for the aldehyde oxidation and reduction pathways to the phi0d and phiAd coefficients. The combination of dead-end and product inhibitors can be used to determine the reaction mechanism for the aldehyde oxidation pathway. Previously, we showed that with Drosophila Adh, the interconversion between alcohols and aldehydes followed a strictly compulsory ordered pathway, although aldehydes and ketones formed binary complexes with the enzyme. This raised the question regarding the reaction mechanism for the oxidation of aldehydes, i.e. whether a random ordered pathway was followed. In the present work, the mechanism for the oxidation of different aldehydes and the accompanying dismutation reaction with the slow alleloenzyme (AdhS) from Drosophila melanogaster has been studied. To obtain

  16. Drosophila melanogaster alcohol dehydrogenase: mechanism of aldehyde oxidation and dismutation.

    PubMed Central

    Winberg, J O; McKinley-McKee, J S

    1998-01-01

    Drosophila alcohol dehydrogenase (Adh) catalyses the oxidation of both alcohols and aldehydes. In the latter case, the oxidation is followed by a reduction of the aldehyde, i.e. a dismutation reaction. At high pH, dismutation is accompanied by a small release of NADH, which is not observed at neutral pH. Previously it has been emphasized that kinetic coefficients obtained by measuring the increase in A340, i.e. the release of NADH at high pH is not a direct measure of the aldehyde oxidation reaction and these values cannot be compared with those for alcohol dehydrogenation. In this article we demonstrate that this is not entirely true, and that the coefficients phiB and phiAB, where B is the aldehyde and A is NAD+, are the same for a dismutation reaction and a simple aldehyde dehydrogenase reaction. Thus the substrate specificity of the aldehyde oxidation reaction can be determined by simply measuring the NADH release. The coefficients for oxidation and dehydrogenation reactions (phi0d and phiAd respectively) are complex and involve the constants for the dismutation reaction. However, dead-end inhibitors can be used to determine the quantitative contribution of the kinetic constants for the aldehyde oxidation and reduction pathways to the phi0d and phiAd coefficients. The combination of dead-end and product inhibitors can be used to determine the reaction mechanism for the aldehyde oxidation pathway. Previously, we showed that with Drosophila Adh, the interconversion between alcohols and aldehydes followed a strictly compulsory ordered pathway, although aldehydes and ketones formed binary complexes with the enzyme. This raised the question regarding the reaction mechanism for the oxidation of aldehydes, i.e. whether a random ordered pathway was followed. In the present work, the mechanism for the oxidation of different aldehydes and the accompanying dismutation reaction with the slow alleloenzyme (AdhS) from Drosophila melanogaster has been studied. To obtain

  17. A prolific catalyst for dehydrogenation of neat formic acid.

    PubMed

    Celaje, Jeff Joseph A; Lu, Zhiyao; Kedzie, Elyse A; Terrile, Nicholas J; Lo, Jonathan N; Williams, Travis J

    2016-01-01

    Formic acid is a promising energy carrier for on-demand hydrogen generation. Because the reverse reaction is also feasible, formic acid is a form of stored hydrogen. Here we present a robust, reusable iridium catalyst that enables hydrogen gas release from neat formic acid. This catalysis works under mild conditions in the presence of air, is highly selective and affords millions of turnovers. While many catalysts exist for both formic acid dehydrogenation and carbon dioxide reduction, solutions to date on hydrogen gas release rely on volatile components that reduce the weight content of stored hydrogen and/or introduce fuel cell poisons. These are avoided here. The catalyst utilizes an interesting chemical mechanism, which is described on the basis of kinetic and synthetic experiments. PMID:27076111

  18. A prolific catalyst for dehydrogenation of neat formic acid

    PubMed Central

    Celaje, Jeff Joseph A.; Lu, Zhiyao; Kedzie, Elyse A.; Terrile, Nicholas J.; Lo, Jonathan N.; Williams, Travis J.

    2016-01-01

    Formic acid is a promising energy carrier for on-demand hydrogen generation. Because the reverse reaction is also feasible, formic acid is a form of stored hydrogen. Here we present a robust, reusable iridium catalyst that enables hydrogen gas release from neat formic acid. This catalysis works under mild conditions in the presence of air, is highly selective and affords millions of turnovers. While many catalysts exist for both formic acid dehydrogenation and carbon dioxide reduction, solutions to date on hydrogen gas release rely on volatile components that reduce the weight content of stored hydrogen and/or introduce fuel cell poisons. These are avoided here. The catalyst utilizes an interesting chemical mechanism, which is described on the basis of kinetic and synthetic experiments. PMID:27076111

  19. Surface-assisted dehydrogenative homocoupling of porphine molecules.

    PubMed

    Wiengarten, Alissa; Seufert, Knud; Auwärter, Willi; Ecija, David; Diller, Katharina; Allegretti, Francesco; Bischoff, Felix; Fischer, Sybille; Duncan, David A; Papageorgiou, Anthoula C; Klappenberger, Florian; Acres, Robert G; Ngo, Thien H; Barth, Johannes V

    2014-07-01

    The templated synthesis of porphyrin dimers, oligomers, and tapes has recently attracted considerable interest. Here, we introduce a clean, temperature-induced covalent dehydrogenative coupling mechanism between unsubstituted free-base porphine units yielding dimers, trimers, and larger oligomers directly on a Ag(111) support under ultrahigh-vacuum conditions. Our multitechnique approach, including scanning tunneling microscopy, near-edge X-ray absorption fine structure and photoelectron spectroscopy complemented by theoretical modeling, allows a comprehensive characterization of the resulting nanostructures and sheds light on the coupling mechanism. We identify distinct coupling motifs and report a decrease of the electronic gap and a modification of the frontier orbitals directly associated with the formation of triply fused dimeric species. This new on-surface homocoupling protocol yields covalent porphyrin nanostructures addressable with submolecular resolution and provides prospective model systems towards the exploration of extended oligomers with tailored chemical and physical properties. PMID:24955656

  20. Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.

    SciTech Connect

    Dietrich, Brandon L.; Goldberg, Karen I.; Heinekey, D. M.; Autrey, Thomas; Linehan, John C.

    2008-10-06

    Dehydrogenation of ammonia borane (AB) and methylamine-borane (MeAB) is catalyzed efficiently by the iridium pincer complex (η3-1,3-(OPtBu2)2C6H3)Ir(H)2 (1). With MeAB and with MeAB/AB mixtures, rapid release of one equivalent of H2 is observed to yield soluble oligomeric products at rates similar to those previously reported for the dehydrogenation of AB catalyzed by 1. The rapid dehydrogenation reaction has allowed the experimental determination of the reaction enthalpy (ΔH) for the dehydrogenation of AB, MeAB, and AB/MeAB mixtures by calorimetry. The reactions are significantly more exothermic than suggested by some computational studies. This work was supported by the U.S. Department of Energy (DOE) as part of the Center of Excellence for Chemical Hydrogen Storage. PNNL is operated by Battelle for DOE.

  1. A DFT investigation of the potential of porous cages for the catalysis of ammonia borane dehydrogenation.

    PubMed

    Pal, Amrita; Vanka, Kumar

    2011-11-01

    Full DFT based quantum mechanical studies reveal that zero dimensional porous structures, especially the newly proposed phosphorus incorporated organic cages, can be excellent catalysts for the dehydrogenation of ammonia borane. PMID:21901195

  2. Density functional periodic study of the dehydrogenation of methane on Pd (1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Li, Lu; Xu, Jie; Fang, Tao

    2013-12-01

    The adsorption and dehydrogenation mechanism of CH4 on Pd (1 1 1) surface was studied using density functional theory (DFT) together with periodic slab models. According to the optimized structural and energetic properties, it was found that CH3 prefers to adsorb on the top sites of the Pd metal surface. Whereas CH2, CH, and H prefer to adsorb on the fcc sites, and C prefers to adsorb on the hcp sites. In addition, this work identified the optimum configurations for the stable co-adsorption configurations of CHx and H. Finally, four transition states were found for analyzing the mechanism of dehydrogenation of CH4. The results show that the dehydrogenation of CH moiety is relatively difficult and the dehydrogenation of CH3 is the rate-determining step in the overall reaction.

  3. Interaction of methanol and its dehydrogenation species with Pt-alloy surfaces

    NASA Astrophysics Data System (ADS)

    Cahyanto, Wahyu Tri; Widanarto, Wahyu; Effendi, Mukhtar; Hamdi, Muhammad Raihan; Kasai, Hideaki

    2016-02-01

    Adsorption of sequential single methanol dehydrogenation intermediate species on Pt-, PtRu-, and PtRuMo-surfaces is investigated by using density functional theory (DFT). This work is a part of our efforts in understanding the methanol oxidation reaction (MOR) on Pt-alloy surfaces for further possible prediction of decomposition processes. Particularly, effects of Ru and Mo impurity to the pure Pt surface to form PtRu and PtRuMo surfaces as possible candidates for promising catalysts of direct methanol fuel cells (DMFCs) are given. However, the study is limited to the scientific point of view, i.e., fundamental interactions between adsorbates and surfaces, in correspondence with adsorption mechanism using charge transfer analysis. The trend in the increase of adsorption energy and charge transfer by alloying Ru and Mo to the Pt surface is observed. Moreover, the increase of the d-orbital vacancy caused by alloying Ru and Mo possessing lesser filled d-orbital is suggested to responsible for the increase of surface-adsorbate interaction strength.

  4. Spectroscopic Characterization of Lanthanum-Mediated Dehydrogenation and C-C Bond Coupling of Ethylene.

    PubMed

    Kumari, Sudesh; Cao, Wenjin; Zhang, Yuchen; Roudjane, Mourad; Yang, Dong-Sheng

    2016-07-01

    La(C2H2) and La(C4H6) are observed from the reaction of laser-vaporized La atoms with ethylene molecules by photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization spectroscopy. La(C2H2) is identified as a metallacyclopropene and La(C4H6) as a metallacyclopentene. The three-membered ring is formed by concerted H2 elimination and the five-membered cycle by dehydrogenation and C-C bond coupling. Both metallacycles prefer a doublet ground state with a La 6s-based unpaired electron. Ionization of the neutral doublet state of either complex produces a singlet ion state by removing the La-based electron. The ionization allows accurate measurements of the adiabatic ionization energy of the neutral doublet state and metal-ligand and ligand-based vibrational frequencies of the neutral and ionic states. Although the La atom is in a formal oxidation state of +2, the ionization energies of these metal-hydrocarbon cycles are lower than that of the neutral La atom. Deuteration has a small effect on the ionization energies of the two cyclic radicals but distinctive effects on their vibrational frequencies. PMID:27322131

  5. Intermediates and products of synthetic lignin (dehydrogenative polymerizate) degradation by Phlebia tremellosa.

    PubMed Central

    Reid, I D

    1991-01-01

    Agitated, nitrogen-limited cultures of Phlebia tremellosa caused substantial changes in the distribution of 14C-labelled synthetic lignin (dehydrogenative polymerizate [DHP]) between water-soluble, dioxane-soluble, alkali-soluble, and insoluble fractions before much lignin carbon was metabolized to CO2. First, the insoluble form increased at the expense of the dioxane-soluble form. Later, the amounts of alkali-soluble and water-soluble 14C increased, and release of 14CO2 began. The molecular weight distribution of the dioxane-soluble lignin remained constant during degradation, but that of the water-soluble fraction changed to higher molecular weights. Culture agitation accelerated the attachment of suspended DHP to the mycelia and stimulated production of water-soluble 14C and 14CO2. The nonionic detergent Tween 80 also hastened release of 14CO2 and increased the early conversion of dioxane-soluble DHP to the alkali-soluble and insoluble forms. Oxidative polymerization is suggested as the first step in degradation of DHP by P. tremellosa. PMID:1746943

  6. One site is enough: a theoretical investigation of iron-catalyzed dehydrogenation of formic Acid.

    PubMed

    Sánchez-de-Armas, Rocío; Xue, Liqin; Ahlquist, Mårten S G

    2013-09-01

    Dehydrogenation of HCO2H: The reaction mechanism for the dehydrogenation of formic acid catalyzed by a highly active and selective iron complex has been studied by DFT. The most favorable pathway shows the hydride in Fe-H complexes acting as a spectator ligand throughout the catalytic cycle. This result opens up the Fe complex for modification in order to achieve more efficient and selective catalysts. PMID:23907850

  7. A Robust, Air-Stable, Reusable Ruthenium Catalyst for Dehydrogenation of Ammonia Borane

    PubMed Central

    Conley, Brian L.; Guess, Denver; Williams, Travis J.

    2011-01-01

    We describe an efficient homogeneous ruthenium catalyst for the dehydrogenation of ammonia borane (AB). This catalyst liberates greater than 2 equivalents of H2 and up to 4.6 system wt% H2 from concentrated AB suspensions under air. Importantly, this catalyst is robust, delivering several cycles of dehydrogenation at high [AB] without loss of catalytic activity, even with exposure to air and water. PMID:21827173

  8. A robust, air-stable, reusable ruthenium catalyst for dehydrogenation of ammonia borane.

    PubMed

    Conley, Brian L; Guess, Denver; Williams, Travis J

    2011-09-14

    We describe an efficient homogeneous ruthenium catalyst for the dehydrogenation of ammonia borane (AB). This catalyst liberates more than 2 equiv of H(2) and up to 4.6 system wt % H(2) from concentrated AB suspensions under air. Importantly, this catalyst is robust, delivering several cycles of dehydrogenation at high [AB] without loss of catalytic activity, even with exposure to air and water. PMID:21827173

  9. Rechargeable Hydrogen Storage System Based on the Dehydrogenative Coupling of Ethylenediamine with Ethanol.

    PubMed

    Hu, Peng; Ben-David, Yehoshoa; Milstein, David

    2016-01-18

    A novel and simple hydrogen storage system was developed, based on the dehydrogenative coupling of inexpensive ethylenediamine with ethanol to form diacetylethylenediamine. The system is rechargeable and utilizes the same ruthenium pincer catalyst for both hydrogen loading and unloading procedures. It is efficient and uses a low catalyst loading. Repetitive reversal reactions without addition of new catalyst result in excellent conversions in both the dehydrogenation and hydrogenation procedures in three cycles. PMID:26211515

  10. On-Surface Domino Reactions: Glaser Coupling and Dehydrogenative Coupling of a Biscarboxylic Acid To Form Polymeric Bisacylperoxides.

    PubMed

    Held, Philipp Alexander; Gao, Hong-Ying; Liu, Lacheng; Mück-Lichtenfeld, Christian; Timmer, Alexander; Mönig, Harry; Barton, Dennis; Neugebauer, Johannes; Fuchs, Harald; Studer, Armido

    2016-08-01

    Herein we report the on-surface oxidative homocoupling of 6,6'-(1,4-buta-1,3-diynyl)bis(2-naphthoic acid) (BDNA) via bisacylperoxide formation on different Au substrates. By using this unprecedented dehydrogenative polymerization of a biscarboxylic acid, linear poly-BDNA with a chain length of over 100 nm was prepared. It is shown that the monomer BDNA can be prepared in situ at the surface via on-surface Glaser coupling of 6-ethynyl-2-naphthoic acid (ENA). Under the Glaser coupling conditions, BDNA directly undergoes polymerization to give the polymeric peroxide (poly-BDNA) representing a first example of an on-surface domino reaction. It is shown that the reaction outcome varies as a function of surface topography (Au(111) or Au(100)) and also of the surface coverage, to give branched polymers, linear polymers, or 2D metal-organic networks. PMID:27410485

  11. Copper-Mediated Cross-Dehydrogenative Coupling of 2-Methylpyridine and 8-Methylquinoline with Methyl Ketones and Benzamides.

    PubMed

    Kumar, Gadde Sathish; Boyle, Joshua William; Tejo, Ciputra; Chan, Philip Wai Hong

    2016-02-01

    A synthetic method to prepare (E)-(pyridin-2-yl)enones and (E)-(quinolin-8-yl)enones that relies on the respective copper(I)-catalyzed formal cross-dehydrogenative coupling (CDC) reaction of 2-methylpyridine and 8-methylquinoline with methyl ketones has been discovered. The mechanism was delineated to follow a pathway involving oxidation of the N-heterocycle to its corresponding aldehyde adduct prior to reaction with the methyl ketone. The versatility and substrate dependent divergence in the reactivity of the copper-mediated CDC strategy was exemplified by its application to the synthesis of N-(quinolin-8-ylmethyl)amide and N-(quinolin-8-ylmethyl)aniline adducts on switching the cross-coupling partner to benzamides or an aniline derivative. PMID:26586026

  12. Two cases of acute propane/butane poisoning in prison.

    PubMed

    Rossi, Riccardo; Suadoni, Fabio; Pieroni, Ludovica; De-Giorgio, Fabio; Lancia, Massimo

    2012-05-01

    Hydrocarbon inhalation is seldom chosen as a means to commit suicide. This practice is exclusively a prerogative of the prison population; it is, however, only exceptionally found in this environment. The two cases of lethal inhalation of propane/butane gas observed by us over a very short time occurred in this context. Toxicologic analyses were performed by means of gas chromatography (head space) and revealed a propane/butane mixture in all specimens (heart blood, bile, and urine) except vitreous humor. Although fatal arrhythmia posthydrocarbon gas abuse is well known, the concentrations of the two hydrocarbons were sufficient to induce death by asphyxiation and were distributed (fairly) homogeneously in all biological fluids and organs examined, a parameter permitting one to assume that death occurred within a relatively short period of time. The absence of finding in vitreous humor and the trace amount in urine suggests that both men died very quickly. PMID:22150071

  13. THERMODYNAMIC EVALUATION OF PREDICTED FLUORINATED ETHER, ETHANE, AND PROPANE AZEOTROPES

    EPA Science Inventory

    The paper gives results of thermodynamic analyses, using basic thermophysical property data, to evaluate seven predicted fluorinated ether, ethane, and propane azeotropes: E125/RC270, E125/R134a, E143a/R134, R134a/E143a, E143a/ R152a, R134/R245cb, and R245cb/R227ea. he performanc...

  14. 3-Oxo-3-(piperidin-1-yl)propane­nitrile

    PubMed Central

    Fun, Hoong-Kun; Quah, Ching Kheng; Abdel-Aziz, Hatem A.; Ghabbour, Hazem A.

    2012-01-01

    In the title compound, C8H12N2O, the piperidine ring exhibits a chair conformation and its least-squares plane (all atoms) makes a dihedral angle of 32.88 (12)° with the propane­nitrile unit (r.m.s. deviation = 0.001 Å). In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [001]. PMID:22969610

  15. Gel-assisted crystallization of [Ir4(IMe)7(CO)H10](2+) and [Ir4(IMe)8H9](3+) clusters derived from catalytic glycerol dehydrogenation.

    PubMed

    Sharninghausen, Liam S; Mercado, Brandon Q; Crabtree, Robert H; Balcells, David; Campos, Jesús

    2015-11-14

    The two title clusters were formed during iridium-catalyzed glycerol dehydrogenation and display a remarkably high NHC content. They were crystallized in either agarose or polyethylene oxide gel matrices, while more conventional crystallization techniques proved unsuccessful. Cluster [Ir4(IMe)8H9](3+), with a net charge of +3, was only crystallizable with a polyoxometalate Keggin trianion. The crystal packing of this intercluster compound is discussed. Computational studies position the iridium hydrides and provide insights into the bonding. PMID:26435314

  16. ZnO modified ZSM-5 and Y zeolites fabricated by atomic layer deposition for propane conversion.

    PubMed

    Gong, Ting; Qin, Lijun; Lu, Jian; Feng, Hao

    2016-01-01

    ZnO modified ZSM-5 and Y zeolites are synthesized by performing atomic layer deposition (ALD) of ZnO to HZSM-5 and HY using diethyl zinc and water as the precursors. The surface area and pore volume of ZSM-5 and Y zeolites are progressively reduced with the increasing number of ZnO ALD cycles. XRD and SEM characterization methods show that highly dispersed ZnO species are deposited on the internal and external surfaces of both zeolites. The ZnO species deposited on ZSM-5 are in an amorphous form while nano-crystallites of ZnO are present on Y zeolites after performing ≥2 cycles of ZnO ALD. XPS and TPR characterization methods reveal that isolated Zn(OH)(+) species are predominantly formed on both zeolites after the first cycle of ZnO ALD and the ZnO clusters gradually grow larger with the increasing number of ALD cycles. The type and strength of acid sites on the parent and the ALD ZnO modified zeolites are studied by FTIR spectra of adsorbed pyridine. Incorporation of ZnO into Y zeolite by ALD completely eliminates the Brønsted acid sites and increases the number of strong Lewis acid sites. Similar effects are obtained on ALD ZnO modified ZSM-5 except that the Brønsted acid sites are only partially removed. Catalytic properties of the ALD ZnO modified zeolites are evaluated in propane conversion. Introduction of ZnO species significantly improves the activities of both zeolites. Propylene is the major reaction product on ALD ZnO modified Y zeolite while high selectivities to aromatics are achieved on ALD ZnO modified ZSM-5. These results suggest that ZnO species merely promote the dehydrogenation reaction while the subsequent oligomerization and cyclization reactions require Brønsted acid sites. For both zeolites the catalyst fabricated by only 1 or 2 cycles of ZnO ALD performs better than those fabricated by multiple cycles of ALD, indicating that isolated Zn(OH)(+) species are more effective for the conversion of propane to propylene and aromatics. PMID

  17. Gas Phase UTE MRI of Propane and Propene

    PubMed Central

    Kovtunov, Kirill V.; Romanov, Alexey S.; Salnikov, Oleg G.; Barskiy, Danila A.; Chekmenev, Eduard Y.; Koptyug, Igor V.

    2016-01-01

    1H MRI of gases can potentially enable functional lung imaging to probe gas ventilation and other functions. In this work, 1H MR images of hyperpolarized and thermally polarized propane gas were obtained using UTE (ultrashort echo time) pulse sequence. A 2D image of thermally polarized propane gas with ~0.9×0.9 mm2 spatial resolution was obtained in less than 2 seconds, demonstrating that even non-hyperpolarized hydrocarbon gases can be successfully utilized for conventional proton MRI. The experiments were also performed with hyperpolarized propane gas and demonstrated acquisition of high-resolution multi-slice FLASH 2D images in ca. 510 s and non slice-selective 2D UTE MRI images in ca. 2 s. The UTE approach adopted in this study can be potentially used for medical lung imaging. Furthermore, the possibility to combine UTE with selective suppression of 1H signals from one of the two gases in a mixture is demonstrated in this MRI study. The latter can be useful for visualizing industrially important processes where several gases may be present, e.g., gas-solid catalytic reactions. PMID:27478870

  18. The viscosity of gaseous propane and its initial density dependence

    NASA Astrophysics Data System (ADS)

    Vogel, E.

    1995-11-01

    Results of five series of high-precision viscosity measurements on gaseous propane, each differing in density, are reported. The measurements were performed in a quartz oscillating-disk viscometer with small gaps from room temperature up to about 625 K and for densities between 0.01 and 0.05 mol · L-1. The experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficients deduced from the zero-density and initial-density viscosity coefficients for propane and for further n-alkanes are in close agreement with the theoretical representation of the Rainwater-Friend theory for the potential parameter ratios by Bich and Vogel. A new representation of the viscosity of propane in the limit of zero density is provided using the new experimental data and some data sets from literature. The universal correlation based on the extended principle of corresponding states extends over the temperature range 293 to 625 K with an uncertainty of ±0.5 % and deviates from earlier representations by about 1 % at the upper temperature limit.

  19. The viscosity of gaseous propane and its initial density dependence

    SciTech Connect

    Vogel, E.

    1995-11-01

    Results of five series of high-precision viscosity measurements on gaseous propane, each differing in density, are reported. The measurements were performed in a quartz oscillating-disk viscometer with small gaps from room temperature up to about 625 K and for densities between 0.01 and 0.05 mol {center_dot} L{sup -1}. The experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficients deduced from the zero-density and initial-density viscosity coefficients for propane and for further n-alkanes are in close agreement with the theoretical representation of the Rainwater-Friend theory for the potential parameter ratios by Bich and Vogel. A new representation of the viscosity of propane in the limit of zero density is provided using the new experimental data and some data sets from literature. The universal correlation based on the extended principle of corresponding states extends over the temperature range 293 to 625 K with an uncertainty of {plus_minus}0.5% and deviates from earlier representations by about 1% at the upper temperature limit.

  20. Theoretical study of interactions between 2,2-Bis (ethylferrocenyl) propane and ammonium perchlorate at low temperature

    NASA Astrophysics Data System (ADS)

    Zhou, Junhong; Zhang, Wei; Yang, Jun; Jiang, Benzheng; Chen, Weiming

    2016-05-01

    In order to explore the interaction mechanism between 2,2-Bis (ethylferrocenyl) propane (GFP) and ammonium perchlorate (AP) at low temperature (below 250 °C), all the possible intermolecular interactions between GFP and AP were calculated. The calculations were performed in single molecule, cluster and slab models. The calculation results show that the interactions between GFP and AP at low temperature mainly come from GFP-H+ and GFP-NH4+ pair interactions. We speculate that the interaction mechanism between GFP and AP at low temperature is that GFP/H+ or GFP/NH4+ interactions cause GFP to be protonated, and then protonated GFP is to further oxidized.

  1. Propane σ-Complexes on PdO(101): Spectroscopic Evidence of the Selective Coordination and Activation of Primary C-H Bonds.

    PubMed

    Zhang, Feng; Pan, Li; Choi, Juhee; Mehar, Vikram; Diulus, John T; Asthagiri, Aravind; Weaver, Jason F

    2015-11-16

    Achieving selective C-H bond cleavage is critical for developing catalytic processes that transform small alkanes to value-added products. The present study clarifies the molecular-level origin for an exceptionally strong preference for propane to dissociate on the crystalline PdO(101) surface via primary C-H bond cleavage. Using reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations, we show that adsorbed propane σ-complexes preferentially adopt geometries on PdO(101) in which only primary C-H bonds datively interact with the surface Pd atoms at low propane coverages and are thus activated under typical catalytic reaction conditions. We show that a propane molecule achieves maximum stability on PdO(101) by adopting a bidentate geometry in which a H-Pd dative bond forms at each CH3 group. These results demonstrate that structural registry between the molecule and surface can strongly influence the selectivity of a metal oxide surface in activating alkane C-H bonds. PMID:26420576

  2. Experimental study on transmission of an overdriven detonation wave from propane/oxygen to propane/air

    SciTech Connect

    Li, J.; Lai, W.H.; Chung, K.; Lu, F.K.

    2008-08-15

    Two sets of experiments were performed to achieve a strong overdriven state in a weaker mixture by propagating an overdriven detonation wave via a deflagration-to-detonation transition (DDT) process. First, preliminary experiments with a propane/oxygen mixture were used to evaluate the attenuation of the overdriven detonation wave in the DDT process. Next, experiments were performed wherein a propane/oxygen mixture was separated from a propane/air mixture by a thin diaphragm to observe the transmission of an overdriven detonation wave. Based on the characteristic relations, a simple wave intersection model was used to calculate the state of the transmitted detonation wave. The results showed that a rarefaction effect must be included to ensure that there is no overestimate of the post-transmission wave properties when the incident detonation wave is overdriven. The strength of the incident overdriven detonation wave plays an important role in the wave transmission process. The experimental results showed that a transmitted overdriven detonation wave occurs instantaneously with a strong incident overdriven detonation wave. The near-CJ state of the incident wave leads to a transmitted shock wave, and then the transition to the overdriven detonation wave occurs downstream. The attenuation process for the overdriven detonation wave decaying to a near-CJ state occurs in all tests. After the attenuation process, an unstable detonation wave was observed in most tests. This may be attributed to the increase in the cell width in the attenuation process that exceeds the detonability cell width limit. (author)

  3. Process for alkane group dehydrogenation with organometallic catalyst

    DOEpatents

    Kaska, W.C.; Jensen, C.M.

    1998-07-14

    An improved process is described for the catalytic dehydrogenation of organic molecules having a ##STR1## group to produce a ##STR2## group. The organic molecules are: ##STR3## wherein: A.sup.1, A.sup.2, A.sup.3, and A.sup.4 are each independently P, As or N: E.sup.2 is independently C or N; E.sup.3 is independently C, Si or Ge; E.sup.4 is independently C, Si, or Ge; and E.sup.5 is independently C, Si or Ge; M.sup.1, M.sup.2, M.sup.3, and M.sup.4 each is a metal atom independently selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum; Q.sup.1, Q.sup.2, Q.sup.3, and Q.sup.4 are each independently a direct bond, --CH.sub.2 --, --CH.sub.2 CH.sub.2 --, or CH.dbd.CH--; in structure I, structure II or structure IV, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently selected from alkyl, alkenyl, cycloalkyl, and aryl, or R.sup.1 and R.sup.2 together and R.sup.3 and R.sup.4 together form a ring structure having from 4 to 10 carbon atoms, or in structure III, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 are each independently selected from alkyl, alkenyl, cycloalkyl, and aryl, or R.sup.5 and R.sup.6 together and R.sup.7 and R.sup.8 together form a ring structure having from 4 to 10 carbon atoms, at a temperature of between about 100.degree. and 250.degree. C. for between about 1 hr and 300 days in the absence of N.sub.2. The surprisingly stable catalyst is a complex of an organic ligand comprising H, C, Si, N, P atoms, and a platinum group metal. The dehydrogenation is performed between about 100 to 200.degree. C., and has increased turnover.

  4. Process for alkane group dehydrogenation with organometallic catalyst

    DOEpatents

    Kaska, William C.; Jensen, Craig M.

    1998-01-01

    An improved process is described for the catalytic dehydrogenation of organic molecules having a ##STR1## group to produce a ##STR2## group. The organic molecules are: ##STR3## wherein: A.sup.1, A.sup.2, A.sup.3, and A.sup.4 are each independently P, As or N: E.sup.2 is independently C or N; E.sup.3 is independently C, Si or Ge; E.sup.4 is independently C, Si, or Ge; and E.sup.5 is independently C, Si or Ge; M.sup.1, M.sup.2, M.sup.3, and M.sup.4 each is a metal atom independently selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum; Q.sup.1, Q.sup.2, Q.sup.3, and Q.sup.4 are each independently a direct bond, --CH.sub.2 --, --CH.sub.2 CH.sub.2 --, or CH.dbd.CH--; in structure I, structure II or structure IV, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently selected from alkyl, alkenyl, cycloalkyl, and aryl, or R.sup.1 and R.sup.2 together and R.sup.3 and R.sup.4 together form a ring structure having from 4 to 10 carbon atoms, or in structure III, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 are each independently selected from alkyl, alkenyl, cycloalkyl, and aryl, or R.sup.5 and R.sup.6 together and R.sup.7 and R.sup.8 together form a ring structure having from 4 to 10 carbon atoms, at a temperature of between about 100.degree. and 250.degree. C. for between about 1 hr and 300 days in the absence of N.sub.2. The surprisingly stable catalyst is a complex of an organic ligand comprising H, C, Si, N, P atoms, and a platinum group metal. The dehydrogenation is performed between about 100 to 200.degree. C., and has increased turnover.

  5. Regeneration of LOHC dehydrogenation catalysts: In-situ IR spectroscopy on single crystals, model catalysts, and real catalysts from UHV to near ambient pressure

    NASA Astrophysics Data System (ADS)

    Amende, Max; Kaftan, Andre; Bachmann, Philipp; Brehmer, Richard; Preuster, Patrick; Koch, Marcus; Wasserscheid, Peter; Libuda, Jörg

    2016-01-01

    The Liquid Organic Hydrogen Carrier (LOHC) concept offers an efficient route to store hydrogen using organic compounds that are reversibly hydrogenated and dehydrogenated. One important challenge towards application of the LOHC technology at a larger scale is to minimize degradation of Pt-based dehydrogenation catalysts during long-term operation. Herein, we investigate the regeneration of Pt/alumina catalysts poisoned by LOHC degradation. We combine ultrahigh vacuum (UHV) studies on Pt(111), investigations on well-defined Pt/Al2O3 model catalysts, and near-ambient pressure (NAP) measurements on real core-shell Pt/Al2O3 catalyst pellets. The catalysts were purposely poisoned by reaction with the LOHC perhydro-dibenzyltoluene (H18-MSH) and with dicyclohexylmethane (DCHM) as a simpler model compound. We focus on oxidative regeneration under conditions that may be applied in real dehydrogenation reactors. The degree of poisoning and regeneration under oxidative reaction conditions was quantified using CO as a probe molecule and measured by infrared reflection-absorption spectroscopy (IRAS) and diffuse reflectance Fourier transform IR spectroscopy (DRIFTS) for planar model systems and real catalysts, respectively. We find that regeneration strongly depends on the composition of the catalyst surface. While the clean surface of a poisoned Pt(111) single crystal is fully restored upon thermal treatment in oxygen up to 700 K, contaminated Pt/Al2O3 model catalyst and core-shell pellet were only partially restored under the applied reaction conditions. Whereas partial regeneration on facet-like sites on supported catalysts is more facile than on Pt(111), carbonaceous deposits adsorbed at low-coordinated defect sites impede full regeneration of the Pt/Al2O3 catalysts.

  6. Mechanistic studies on the gas-phase dehydrogenation of alkanes at cyclometalated platinum complexes.

    PubMed

    Butschke, Burkhard; Schwarz, Helmut

    2012-10-29

    In the ion/molecule reactions of the cyclometalated platinum complexes [Pt(L-H)](+) (L=2,2'-bipyridine (bipy), 2-phenylpyridine (phpy), and 7,8-benzoquinoline (bq)) with linear and branched alkanes C(n)H(2n+2) (n=2-4), the main reaction channels correspond to the eliminations of dihydrogen and the respective alkenes in varying ratios. For all three couples [Pt(L-H)](+)/C(2)H(6), loss of C(2)H(4) dominates clearly over H(2) elimination; however, the mechanisms significantly differs for the reactions of the "rollover"-cyclometalated bipy complex and the classically cyclometalated phpy and bq complexes. While double hydrogen-atom transfer from C(2)H(6) to [Pt(bipy-H)](+), followed by ring rotation, gives rise to the formation of [Pt(H)(bipy)](+), for the phpy and bq complexes [Pt(L-H)](+), the cyclometalated motif is conserved; rather, according to DFT calculations, formation of [Pt(L-H)(H(2))](+) as the ionic product accounts for C(2)H(4) liberation. In the latter process, [Pt(L-H)(H(2))(C(2)H(4))](+) (that carries H(2) trans to the nitrogen atom of the heterocyclic ligand) serves, according to DFT calculation, as a precursor from which, due to the electronic peculiarities of the cyclometalated ligand, C(2)H(4) rather than H(2) is ejected. For both product-ion types, [Pt(H)(bipy)](+) and [Pt(L-H)(H(2))](+) (L=phpy, bq), H(2) loss to close a catalytic dehydrogenation cycle is feasible. In the reactions of [Pt(bipy-H)](+) with the higher alkanes C(n)H(2n+2) (n=3, 4), H(2) elimination dominates over alkene formation; most probably, this observation is a consequence of the generation of allyl complexes, such as [Pt(C(3)H(5))(bipy)](+). In the reactions of [Pt(L-H)](+) (L=phpy, bq) with propane and n-butane, the losses of the alkenes and dihydrogen are of comparable intensities. While in the reactions of "rollover"-cyclometalated [Pt(bipy-H)](+) with C(n)H(2n+2) (n=2-4) less than 15 % of the generated product ions are formed by C-C bond-cleavage processes, this value is

  7. Amlodipine metabolism in human liver microsomes and roles of CYP3A4/5 in the dihydropyridine dehydrogenation.

    PubMed

    Zhu, Yanlin; Wang, Fen; Li, Quan; Zhu, Mingshe; Du, Alicia; Tang, Wei; Chen, Weiqing

    2014-02-01

    Amlodipine is a commonly prescribed calcium channel blocker for the treatment of hypertension and ischemic heart disease. The drug is slowly cleared in humans primarily via dehydrogenation of its dihydropyridine moiety to a pyridine derivative (M9). Results from clinical drug-drug interaction studies suggest that CYP3A4/5 mediate metabolism of amlodipine. However, attempts to identify a role of CYP3A5 in amlodipine metabolism in humans based on its pharmacokinetic differences between CYP3A5 expressers and nonexpressers failed. Objectives of this study were to determine the metabolite profile of amlodipine (a racemic mixture and S-isomer) in human liver microsomes (HLM), and to identify the cytochrome P450 (P450) enzyme(s) involved in the M9 formation. Liquid chromatography/mass spectrometry analysis showed that amlodipine was mainly converted to M9 in HLM incubation. M9 underwent further O-demethylation, O-dealkylation, and oxidative deamination to various pyridine derivatives. This observation is consistent with amlodipine metabolism in humans. Incubations of amlodipine with HLM in the presence of selective P450 inhibitors showed that both ketoconazole (an inhibitor of CYP3A4/5) and CYP3cide (an inhibitor of CYP3A4) completely blocked the M9 formation, whereas chemical inhibitors of other P450 enzymes had little effect. Furthermore, metabolism of amlodipine in expressed human P450 enzymes showed that only CYP3A4 had significant activity in amlodipine dehydrogenation. Metabolite profiles and P450 reaction phenotyping data of a racemic mixture and S-isomer of amlodipine were very similar. The results from this study suggest that CYP3A4, rather than CYP3A5, plays a key role in metabolic clearance of amlodipine in humans. PMID:24301608

  8. Computational modeling of a direct propane fuel cell

    NASA Astrophysics Data System (ADS)

    Khakdaman, H.; Bourgault, Y.; Ternan, M.

    2011-03-01

    The first two dimensional mathematical model of a complete direct propane fuel cell (DPFC) is described. The governing equations were solved using FreeFem software that uses finite element methods. Robin boundary conditions were used to couple the anode, membrane, and cathode sub-domains successfully. The model showed that a polytetrafluoroethylene membrane having its pores filled with zirconium phosphate (ZrP-PTFE), in a DPFC at 150 °C performed much the same as other electrolytes; Nafion, aqueous H3PO4, and H2SO4 doped polybenzimidazole, when they were used in DPFCs. One advantage of a ZrP-PTFE at 150 °C is that it operates without liquid phase water. As a result corrosion will be much less severe and it may be possible for non-precious metal catalysts to be used. Computational results showed that the thickness of the catalyst layer could be increased sufficiently so that the pressure drop between the reactant and product channels of the interdigitated flow fields is small. By increasing the width of the land and therefore the reactant's contact time with the catalyst it was possible to approach 100% propane conversion. Therefore fuel cell operation with a minimum concentration of propane in the product stream should be possible. Finally computations of the electrical potential in the ZrP phase, the electron flux in the Pt/C phase, and the overpotential in both the anode and cathode catalyst layers showed that serious errors in the model occurred because proton diffusion, caused by the proton concentration gradient, was neglected in the equation for the conservation of protons.

  9. Ruthenium(II)-PNN pincer complex catalyzed dehydrogenation of benzyl alcohol to ester: A DFT study

    NASA Astrophysics Data System (ADS)

    Tao, Jingcong; Wen, Li; Lv, Xiaobo; Qi, Yong; Yin, Hailiang

    2016-04-01

    The molecular mechanism of the dehydrogenation of primary alcohol to ester catalyzed by the ruthenium(II)-PNN pincer complex Ru(H)(η2-BH4)(PNN), [PNN: (2-(di-tert-butylphosphinomethyl)-6-(diethlaminomethyl)-pyridine)] has been investigated using density functional theory calculations. The catalytic cycle includes three stages: (stage I) alcohol dehydrogenation to form aldehyde, (stage II) coupling of aldehyde with alcohol to give hemiacetal or ester, and (stage III) hemiacetal dehydrogenation to form ester. Two dehydrogenation reactions occur via the β-H elimination mechanism rather than the bifunctional double hydrogen transfer mechanism, which could be rationalized as the fluxional behavior of the BH4- ligand. At the second stage, the coupling reaction requires alcohol or the ruthenium catalyst as mediator. The formation of hemiacetal through the alcohol-mediated pathway is kinetically favorable than the ruthenium catalyst-mediated one, which may be attributed to the smaller steric hindrance when the aldehyde approaches the alcohol moiety in the reaction system. Our results would be helpful for experimental chemists to design more effective transition metal catalysts for dehydrogenation of alcohols.

  10. 1,3-Bis[(4-methylbenzylidene)amino-oxy]propane.

    PubMed

    Wu, Jian-Chao; Gao, Su-Xia; Dong, Wen-Kui; Tong, Jun-Feng; Li, Li

    2009-01-01

    The title bis-oxime compound, C(19)H(22)N(2)O(2), synthesized by the reaction of 4-methyl-2-hydroxy-benzaldehyde with 1,3-bis-(amino-oxy)propane in ethanol, adopts a V-shaped conformation. The dihedral angle between the rings is 84.59 (3)°. The mol-ecule is disposed about a crystallographic twofold rotation axis, with one C atom lying on the axis. In the crystal, mol-ecules are packed by C-H⋯π(Ph) inter-actions, forming chains. PMID:21578377

  11. Novel adsorption distillation hybrid scheme for propane/propylene separation

    SciTech Connect

    Kumar, R.; Golden, T.C.; White, T.R.; Rokicki, A. )

    1992-12-01

    A novel adsorption-distillation hybrid scheme is proposed for propane/propylene separation. The suggested scheme has potential for saving up to [approximately]50% energy and [approximately]15-30% in capital costs as compared with current technology. The key concept of the proposed scheme is to separate olefins from alkanes by adsorption and then separate individual olefins and alkanes by simple distillation, thereby eliminating energy intensive and expensive olefin-alkane distillation. A conceptual flow schematic for the proposed hybrid scheme and potential savings are outlined.s

  12. Supercritical convection, critical heat flux, and coking characteristics of propane

    NASA Technical Reports Server (NTRS)

    Rousar, D. C.; Gross, R. S.; Boyd, W. C.

    1984-01-01

    The heat transfer characteristics of propane at subcritical and supercritical pressure were experimentally evaluated using electrically heated Monel K-500 tubes. A design correlation for supercritical heat transfer coefficient was established using the approach previously applied to supercritical oxygen. Flow oscillations were observed and the onset of these oscillations at supercritical pressures was correlated with wall-to-bulk temperature ratio and velocity. The critical heat flux measured at subcritical pressure was correlated with the product of velocity and subcooling. Long duration tests at fixed heat flux conditions were conducted to evaluate coking on the coolant side tube wall and coking rates comparable to RP-1 were observed.

  13. Mineral-catalyzed dehydrogenation of C6 cyclic hydrocarbons: results from experimental studies under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Venturi, S.; Tassi, F.; Gould, I.; Shock, E.; Lorance, E. D.; Bockisch, C.; Fecteau, K.

    2015-12-01

    Volatile organic compounds (VOCs) are ubiquitously present in volcanic and hydrothermal gases. Their relative abundances have been demonstrated to be sensitive to physical and chemical parameters, suggesting VOCs as potential tools for evaluating deep reservoir conditions. Nevertheless, reaction pathways for VOC production at hydrothermal conditions are still poorly understood. Reversible catalytic reforming may be responsible for the high abundance of benzene observed in hydrothermal gases relative to saturated hydrocarbons. The dehydrogenation of n-hexane to benzene could proceed with C6 cyclic hydrocarbons as intermediates, as suggested by the relative enrichment in cyclic hydrocarbons observed in gases originating at T <150 °C. In this study, laboratory experiments were carried out to investigate the production of benzene from cyclic hydrocarbons at 300°C and 85 bar. At these conditions in pure water, negligible benzene is produced from cyclohexane after 10 days. The presence of a mineral phase, especially sphalerite, favored the formation of both benzene and cyclohexene. The efficiency of dehydroaromatization reaction increased at increasing mineral/cyclohexane ratio, pointing to a surface catalyzed reaction. The catalytic action of sphalerite on the C-H bonds was confirmed by the large abundance of deuterated cyclohexane resulted in D2O experiments. The same experiment carried out using cyclohexene in pure water mainly produced methyl-cyclopentenes (via isomerization) and cyclohexanol (via oxygenation). In presence of sphalerite, the production of significant amounts of benzene confirmed the critical role of this mineral for the aromatization of cyclic compounds under hydrothermal conditions. Contrarily, products from cyclohexene solution phase oxidation using Cu(II) mainly consisted of oxygenated VOCs.

  14. Recyclable functionalization of silica with alcohols via dehydrogenative addition on hydrogen silsesquioxane.

    PubMed

    Moitra, Nirmalya; Kamei, Toshiyuki; Kanamori, Kazuyoshi; Nakanishi, Kazuki; Takeda, Kazuyuki; Shimada, Toyoshi

    2013-10-01

    Synthesis of class II hybrid silica materials requires the formation of covalent linkage between organic moieties and inorganic frameworks. The requirement that organosilylating agents be present to provide the organic part limits the synthesis of functional inorganic oxides, however, due to the water sensitivity and challenges concerning purification of the silylating agents. Synthesis of hybrid materials with stable molecules such as simple alcohols, rather than with these difficult silylating agents, may therefore provide a path to unprecedented functionality. Herein, we report the novel functionalization of silica with organic alcohols for the first time. Instead of using hydrolyzable organosilylating agents, we used stable organic alcohols with a Zn(II) catalyst to modify the surface of a recently discovered highly reactive macro-mesoporous hydrogen silsesquioxane (HSQ, HSiO1.5) monolith, which was then treated with water with the catalyst to form surface-functionalized silica. These materials were comprehensively characterized with FT-IR, Raman, solid-state NMR, fluorescence spectroscopy, thermal analysis, elemental analysis, scanning electron microscopy, and nitrogen adsorption-desorption measurements. The results obtained from these measurements reveal facile immobilization of organic moieties by dehydrogenative addition onto surface silane (Si-H) at room temperature with high loading and good tolerance of functional groups. The organic moieties can also be retrieved from the monoliths for recycling and reuse, which enables cost-effective and ecological use of the introduced catalytic/reactive surface functionality. Preservation of the reactivity of as-immobilized organic alcohols has been confirmed, moreover, by successfully performing copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reactions on the immobilized silica surfaces. PMID:23977900

  15. Phenyl substituted indenylphosphine ruthenium complexes as catalysts for dehydrogenation of alcohols.

    PubMed

    Yuan, Jia; Sun, Yue; Yu, Guang-Ao; Zhao, Cui; She, Neng-Fang; Mao, Shu-Lan; Huang, Peng-Shou; Han, Zhi-Jun; Yin, Jun; Liu, Sheng-Hua

    2012-09-14

    Thermal treatment of (1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (1) and (3-mesityl-1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (3) with tBuONa followed by [(η(6)-cymene)RuCl(2))](2) in methanol gave the adduct {(η(6)-cymene)RuCl(2)[(1H-inden-3-yl)PCy(2)]} (6) and {(η(6)-cymene)RuCl(2)[(3-mesityl-1H-inden-3-yl)PCy(2)]} (7), respectively. Thermal treatment of (2-phenyl-1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (4) with tBuONa followed by [(η(6)-cymene)RuCl(2))](2) or RuCl(3)·3H(2)O in methanol gave {Ru[κ(P):(η(6)-2-phenyl-1H-inden-3-yl)PCy(2)]Cl(2)} (8). Whereas (2-mesityl-1H-inden-3-yl)dicyclohexylphosphine (5) reacted with [(η(6)-cymene)RuCl(2))](2) (in toluene) or RuCl(3)·3H(2)O (in ethanol) to afford {Ru[κ(P):(η(6)-2-mesityl-1H-inden-3-yl)PCy(2)]Cl(2)} (9). The molecular structures of complexes 6, 8 and 9 have been determined by single-crystal X-ray diffraction analysis. In addition, complexes 8 and 9 have been found to catalyze the acceptorless dehydrogenation of alcohols in toluene. 9 displayed high activity and different substrates, including cyclic and linear alcohols, were efficiently oxidized to ketones by using 2.0 mol% of catalyst. PMID:22806176

  16. Iron-catalyzed dehydrocoupling/dehydrogenation of amine-boranes.

    PubMed

    Vance, James R; Schäfer, André; Robertson, Alasdair P M; Lee, Kajin; Turner, Joshua; Whittell, George R; Manners, Ian

    2014-02-26

    The readily available iron carbonyl complexes, [CpFe(CO)2]2 (1) and CpFe(CO)2I (2) (Cp = η-C5H5), were found to be efficient precatalysts for the dehydrocoupling/dehydrogenation of the amine-borane Me2NH·BH3 (3) to afford the cyclodiborazane [Me2N-BH2]2 (4), upon UV photoirradiation at ambient temperature. In situ analysis of the reaction mixtures by (11)B NMR spectroscopy indicated that different two-step mechanisms operate in each case. Thus, precatalyst 1 dehydrocoupled 3 via the aminoborane Me2N═BH2 (5) which then cyclodimerized to give 4 via an off-metal process. In contrast, the reaction with precatalyst 2 proceeded via Me2NH-BH2-NMe2-BH3 (6) as the key intermediate, affording 4 as the final product after a second metal-mediated step. The related complex Cp2Fe2(CO)3(MeCN) (7), formed by photoirradiation of 1 in MeCN, was found to be a substantially more active dehydrocoupling catalyst and not to require photoactivation, but otherwise operated via a two-step mechanism analogous to that for 1. Significantly, detailed mechanistic studies indicated that the active catalyst generated from precatalyst 7 was heterogeneous in nature and consisted of small iron nanoparticles (≤10 nm). Although more difficult to study, a similar process is highly likely to operate for precatalyst 1 under photoirradiation conditions. In contrast to the cases of 7 and 1, analogous experimental studies for the case of photoactivated Fe precatalyst 2 suggested that the active catalyst formed in this case was homogeneous. Experimental and computational DFT studies were used to explore the catalytic cycle which appears to involve amine-borane ligated [CpFe(CO)](+) as a key intermediate. PMID:24527706

  17. Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Kislitsyn, Dmitry A.; Mills, Jon M.; Kocevski, Vancho; Chiu, Sheng-Kuei; DeBenedetti, William J. I.; Gervasi, Christian F.; Taber, Benjamen N.; Rosenfield, Ariel E.; Eriksson, Olle; Rusz, Ján; Goforth, Andrea M.; Nazin, George V.

    2016-06-01

    We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces.

  18. Fabrication of Pt-loaded NiCo nanochains with superior catalytic dehydrogenation activity.

    PubMed

    Wen, Ming; Wu, Qingnan; Peng, Jin; Wu, Qingsheng; Wang, Chenxiang

    2014-02-15

    A new magnetic Pt-loaded NiCo nanochain, with the diameter from 80 nm to 120 nm, has been prepared through microwave-induced assembly process followed by the galvanic displacement performance. Pt nanoparticles are distributed on the surface of NiCo nanochains. The products are investigated as hydrolytic dehydrogenation catalyst for potential hydrogen energy applications. Compared with NiCo nanochains, the Pt-loaded NiCo nanochains present exceedingly high catalytic activity toward the hydrolytic dehydrogenation of ammonia borane aqueous under ambient atmosphere at room temperature, where the Ni16Co80/Pt4 nanochains exhibit high catalytic activity with a lower activation energy of 45.72 kJ mol(-1) and a superior dehydrogenation rate of 1.17 × 10(4) mL min(-1) g(-1), suggesting the potential application in hydrogen fuel and chemical industry. PMID:24370425

  19. Effect of dehydrogenation/hydrogenation on the linear and nonlinear optical properties of Li@porphyrins.

    PubMed

    Wu, Heng-Qing; Sun, Shi-Ling; Zhong, Rong-Lin; Xu, Hong-Liang; Su, Zhong-Min

    2012-11-01

    In the present work, Li@porphyrins and their derivatives were designed in order to explore the effect of dehydrogenation/hydrogenation on linear and nonlinear optical properties. Their stable structures were obtained by the M06-2X method. Moreover, the M06-2X method showed that dehydrogenation/hydrogenation has greatly influences polarizabilities (α₀ values) and hyperpolarizabilities (β(tot) and γ(tot) values): α₀ values ranged from 331 to 389 au, β(tot) values from 0 to 2465 au, and γ(tot) values from -21.2 × 10⁴ to 21.4 × 10⁴ au. This new knowledge of the effect of dehydrogenation/hydrogenation on nonlinear optical properties may prove beneficial to the design and development of high-performance porphyrin materials. PMID:22722697

  20. Synthesis of high molecular weight polyesters via in vacuo dehydrogenation polymerization of diols.

    PubMed

    Hunsicker, David M; Dauphinais, Brian C; Mc Ilrath, Sean P; Robertson, Nicholas J

    2012-02-13

    The Milstein catalyst has proven to be highly effective for the conversion of alcohols to esters, as well as alcohols and amines to amides and polyamides. We have recently found that the catalyst's range can be extended to very efficient in vacuo dehydrogenation polymerization of α,ω-diols to generate polyesters. The gaseous hydrogen byproduct that is produced is easily removed to drive the equilibrium toward product, which leads to the formation of high molecular weight polymer (M(n) up to 145,000 g mol(-1)). This optimized methodology works well to polymerize diols with a spacer of six carbons or more. Diols with fewer carbons are cyclized to lactone; the dividing point is the dehydrogenation of 1,5-pentanediol, which leads to a mixture of polyester and lactone. Reported herein is the synthesis and characterization of five aliphatic polyesters prepared via this novel dehydrogenation polymerization approach. PMID:22173989

  1. Effect of Milling Parameters on the Dehydrogenation Properties of the Mg-Ti-H system

    SciTech Connect

    Choi, Young Joon; Lu, Jun; Sohn, Hong Yong; Fang, Zhigang Zak; Ronnebro, Ewa

    2009-11-05

    Magnesium-based alloys are promising candidates as potential hydrogen storage materials due to their inherent high hydrogen contents. Small particle size which can be achieved by milling, and small amounts of transition-metal compounds as catalysts result in increased hydrogen release/uptake kinetics. In this work, we examined the effects of various milling parameters and TiH2 content on the dehydrogenation properties of the Mg-Ti-H system. The samples were prepared with different amounts of TiH2 using various milling methods and conditions. The activation energy and the enthalpy change of dehydrogenation of the milled samples were determined by Thermogravimetric Analysis (TGA) and Differential Thermal Analyzer (DTA). The results indicated that the activation energy and enthalpy change of MgH2 dehydrogenation were significantly reduced when 9.1 mol % of TiH2 was added to it and the mixture was milled in a dual planet

  2. Documentation for propane fleet conversion cost-effectiveness model

    NASA Astrophysics Data System (ADS)

    Taylor, D.; Euritt, M.; Mahmassani, H.

    1992-10-01

    Increased emphasis on energy efficiency and air quality has resulted in a number of state and federal initiatives examining the use of alternative fuels for motor vehicles. Texas instituted an alternative fuels program for public fleet operations beginning in the 1991-92 fiscal year. Life-cycle cost/benefit models for evaluating the economic implications of the action have been developed at the University of Texas at Austin Center for Transportation Research for both compressed natural gas (CNG) and propane. The report documents the various input data, calculations, and assumptions of the Propane Net Present Value (NPV) model. A similar report (number 983-1) documents the same for the CNG model. Input data with constant values across different fleets and locations are discussed first and include basic parameters for on-board storage capacity, vehicle conversion costs, equipment salvage values, etc. Variable input data, reflecting a given fleet size, composition, and location, include the number and types of vehicles, fuel consumption, etc. The next section presents the formulas for the internal model calculations. The final section discusses the basic assumptions underlying the model.

  3. Direct 2-acetoxylation of quinoline N-oxides via copper catalyzed C-H bond activation.

    PubMed

    Chen, Xuan; Zhu, Chongwei; Cui, Xiuling; Wu, Yangjie

    2013-08-01

    An efficient and direct 2-acetoxylation of quinoline N-oxides via copper(I) catalyzed C-H bond activation has been developed. This transformation was achieved using TBHP as an oxidant in the cross-dehydrogenative coupling (CDC) reaction of quinoline N-oxides with aldehydes, and provided a practical pathway to 2-acyloxyl quinolines. PMID:23793162

  4. Reduction, aggregation and physicochemical properties of silver nanoparticles in propan-2-ol:cyclohexane mixtures induced by a high energy electron beam

    SciTech Connect

    Rele, Medha; Kapoor, Sudhir; Mukherjee, Tulsi

    2002-11-20

    Radiolytic reduction of silver and gold ions and subsequent formation of their aggregates have been studied in propan-2-ol:cyclohexane mixture using pulse radiolysis technique. The silver sol, produced on irradiation of Ag{sup +} solution with a train of electron pulses, has been characterized using XRD and TEM. The size of the particles has been found to be in the range of 30-50 nm. The silver sol emit light with a maximum at 340 nm on irradiation with a high energy electron beam. The intensity of emission has been found to decrease with decrease in concentration of Ag particles. Formation of colloidal gold has also been observed on irradiation of NAuCl{sub 4} solution in propan-2-ol:cyclohexane by train of electron pulses. The particles so formed are oxidized on exposure to air. No light emission has been observed from Au sol.

  5. Effect of primary-zone water injection on pollutants from a combustor burning liquid ASTM A-1 and vaporized propane fuels

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.; Norgren, C. T.

    1973-01-01

    A combustor segment 0.457 meter (18 in.) long with a maximum cross section of 0.153 by 0.305 meter (6 by 12 in.) was operated at inlet-air temperatures of 590 and 700 K, inlet-air pressures of 4 and 10 atmospheres, and fuel-air ratios of 0.014 and 0.018 to determine the effect of primary-zone water injection on pollutants from burning either propane or ASTM A-1 fuel. At a simulated takeoff condition of 10 atmospheres and 700 K, multiple-orifice nozzles used to inject water at 1 percent of the airflow rate reduced nitrogen oxides 75 percent with propane and 65 percent with ASTM A-1 fuel. Although carbon monoxide and unburned hydrocarbons increased with water injection, they remained relatively low; and smoke numbers were well below the visibility limit.

  6. 40 CFR 1065.341 - CVS and batch sampler verification (propane check).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false CVS and batch sampler verification... Measurements § 1065.341 CVS and batch sampler verification (propane check). (a) A propane check serves as a CVS... system that extracts a sample from a CVS, as described in paragraph (g) of this section. Using...

  7. 40 CFR 721.533 - Propane, 1,1,1,3,3-pentachloro-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.533 Propane, 1,1,1,3,3-pentachloro-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as propane, 1,1,1,3,3-pentachloro- (PMN...

  8. 40 CFR 721.533 - Propane, 1,1,1,3,3-pentachloro-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.533 Propane, 1,1,1,3,3-pentachloro-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as propane, 1,1,1,3,3-pentachloro- (PMN...

  9. Aromatization of Propane over Element-Alumosilicate Catalysts with ZSM-5 Structure

    NASA Astrophysics Data System (ADS)

    Vosmerikova, L. N.; Volynkina, A. N.; Vosmerikov, A. V.

    2014-08-01

    A method of hydrothermal crystallization of alkaline alumosilicagels is used to manufacture element-alumosilicates with ZSM-5 structure. Their physicochemical and acid properties are investigated and their catalytic activity in the course of propane conversion to aromatic hydrocarbons is determined. The Ga-alumosilicate is found to be the most efficient zeolite catalyst for propane aromatization.

  10. PROGRAM TO DETERMINE PERFORMANCE OF FLUORINATED ETHERS AND FLUORINATED PROPANES IN A COMPRESSOR CALORIMETER

    EPA Science Inventory

    The paper discusses a program to determine the performance of fluorinated ethers and fluorinated propanes in a compressor calorimeter. These chlorine free ethers and propanes are being considered as potential long-term replacements for CFC-11, -12, -114, and -115. A standard comp...

  11. Critical evaluation of Jet-A spray combustion using propane chemical kinetics in gas turbine combustion simulated by KIVA-2

    NASA Astrophysics Data System (ADS)

    Nguyen, H. L.; Ying, S.-J.

    1990-07-01

    Jet-A spray combustion has been evaluated in gas turbine combustion with the use of propane chemical kinetics as the first approximation for the chemical reactions. Here, the numerical solutions are obtained by using the KIVA-2 computer code. The KIVA-2 code is the most developed of the available multidimensional combustion computer programs for application of the in-cylinder combustion dynamics of internal combustion engines. The released version of KIVA-2 assumes that 12 chemical species are present; the code uses an Arrhenius kinetic-controlled combustion model governed by a four-step global chemical reaction and six equilibrium reactions. Researchers efforts involve the addition of Jet-A thermophysical properties and the implementation of detailed reaction mechanisms for propane oxidation. Three different detailed reaction mechanism models are considered. The first model consists of 131 reactions and 45 species. This is considered as the full mechanism which is developed through the study of chemical kinetics of propane combustion in an enclosed chamber. The full mechanism is evaluated by comparing calculated ignition delay times with available shock tube data. However, these detailed reactions occupy too much computer memory and CPU time for the computation. Therefore, it only serves as a benchmark case by which to evaluate other simplified models. Two possible simplified models were tested in the existing computer code KIVA-2 for the same conditions as used with the full mechanism. One model is obtained through a sensitivity analysis using LSENS, the general kinetics and sensitivity analysis program code of D. A. Bittker and K. Radhakrishnan. This model consists of 45 chemical reactions and 27 species. The other model is based on the work published by C. K. Westbrook and F. L. Dryer.

  12. Critical evaluation of Jet-A spray combustion using propane chemical kinetics in gas turbine combustion simulated by KIVA-2

    NASA Technical Reports Server (NTRS)

    Nguyen, H. L.; Ying, S.-J.

    1990-01-01

    Jet-A spray combustion has been evaluated in gas turbine combustion with the use of propane chemical kinetics as the first approximation for the chemical reactions. Here, the numerical solutions are obtained by using the KIVA-2 computer code. The KIVA-2 code is the most developed of the available multidimensional combustion computer programs for application of the in-cylinder combustion dynamics of internal combustion engines. The released version of KIVA-2 assumes that 12 chemical species are present; the code uses an Arrhenius kinetic-controlled combustion model governed by a four-step global chemical reaction and six equilibrium reactions. Researchers efforts involve the addition of Jet-A thermophysical properties and the implementation of detailed reaction mechanisms for propane oxidation. Three different detailed reaction mechanism models are considered. The first model consists of 131 reactions and 45 species. This is considered as the full mechanism which is developed through the study of chemical kinetics of propane combustion in an enclosed chamber. The full mechanism is evaluated by comparing calculated ignition delay times with available shock tube data. However, these detailed reactions occupy too much computer memory and CPU time for the computation. Therefore, it only serves as a benchmark case by which to evaluate other simplified models. Two possible simplified models were tested in the existing computer code KIVA-2 for the same conditions as used with the full mechanism. One model is obtained through a sensitivity analysis using LSENS, the general kinetics and sensitivity analysis program code of D. A. Bittker and K. Radhakrishnan. This model consists of 45 chemical reactions and 27 species. The other model is based on the work published by C. K. Westbrook and F. L. Dryer.

  13. Anionic starch-induced Cu-based composite with flake-like mesostructure for gas-phase propanal efficient removal.

    PubMed

    He, Chi; Liu, Xiaohe; Shi, Jianwen; Ma, Chunyan; Pan, Hua; Li, Guilin

    2015-09-15

    Highly crystalline flake-like CuCeO2-δ composites (strCCx) with large specific surface area and developed mesoporosity were prepared using an economic and effective bio-template route. Modified starch with abundant surface carboxyl groups was adopted as the chelating agent and template for metal cations immobilization via electrostatic attraction predominately based on the process of -COO(-)⋯Cu(2+) and -COO(-)⋯Ce(3+). Physicochemical properties of prepared materials were systematically explored by FT-IR, XRD, TG, N2 adsorption/desorption, FE-SEM, TEM, H2-TPR, O2-TPD, XPS, DRUV-Vis, and XAFS techniques. Propanal as a typical oxygen-contained VOC was adopted as the probe pollutant to evaluate the catalytic performance of synthesized materials. Characterization results reveal that plenty of copper ions in composite oxides are incorporated into CeO2 lattice, which produces oxygen vacancies and enhances metal reducibility. Both specific surface area and pore volume of strCCx samples decreased with the increasing of Cu loading. The flake-like CuCeO2-δ sample (Cu/(Cu+Ce)=0.15) with highest specific surface area (108.2m(2)/g) and surface oxygen concentration is indentified as the most active catalyst with propanal totally destructed at 230°C. The introduction of H2O has a negative effect on propanal removal, and the synthesized catalyst has high tolerance to moisture. In conclusion, the specific surface area and surface oxygen density are two vital factors governing the catalytic activity of composite catalysts. PMID:26037271

  14. Exoemission accompanying the decomposition of methanol on zinc oxide

    NASA Astrophysics Data System (ADS)

    Krylova, I. V.

    2008-09-01

    The electronic phenomena accompanying the adsorption and dehydrogenation of methanol on zinc oxide were studied using the method of exoemission of negative charges. Postemission excited from ZnO by an electron beam was found to be suppressed by the adsorption of methanol vapor, which exhibited electron acceptor properties. Subsequent heating to temperatures close to the temperature of the beginning of methanol decomposition increased the intensity of exoemission, which was evidence of the participation of emission centers (Oδ-) in dehydrogenation. A possible mechanism of methanol decomposition with the participation of surface V s hole centers (Oδ-) of zinc oxide was suggested.

  15. Catalytic dehydrogenation of cycloalkanes to arenes by a dihydrido iridium P-C-P pincer complex

    SciTech Connect

    Gupta, M.; Hagen, C.; Cramer, R.E.; Jensen, C.M.; Kaska, W.C.

    1997-01-29

    We recently found that the iridium P-C-P pincer complex IrH{sub 2}[C{sub 6}H{sub 3}-2,6-(CH{sub 2}-PBu{sup T}{sub 2}){sub 2}] (1) is a highly active, homogeneous catalyst for the transfer dehydrogenation of cyclooctane with unusual long-term stability at temperatures as high as 200 {degree}C. This reactivity has now been extended to the catalytic transfer dehydrogenation of cycloalkanes to arenes. We report this novel catalytic activity as well as the results of an X-ray structure determination of 1. 15 refs., 1 fig., 1 tab.

  16. Hydrogenation and dehydrogenation reactions of C2Hx moieties on the Ru(001) surface

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Waluyo, Iradwikanari; Beale, Evan; Trenary, Michael

    2016-08-01

    Reflection absorption infrared spectroscopy (RAIRS) was used to identify and characterize the surface intermediates formed in the thermal decomposition of ethylene (C2H4) on Ru(001). Ethylene is found to adsorb on the surface in a di-σ bonded complex at 95 K and to dehydrogenate to form ethylidyne (CCH3) at or above 150 K. Upon further annealing to above 320 K, ethylidyne dehydrogenates to ethynyl (CCH). Annealing to higher than 450 K causes ethynyl to decompose to methylidyne (CH). The characterization of surface intermediates formed from the adsorption and decomposition of ethylene provides new insights into the surface chemistry of CxHy species on Ru surfaces.

  17. Zinc-Catalyzed Dehydrogenative Cross-Coupling of Terminal Alkynes with Aldehydes: Access to Ynones.

    PubMed

    Tang, Shan; Zeng, Li; Liu, Yichang; Lei, Aiwen

    2015-12-21

    Because of the lack of redox ability, zinc has seldom been used as a catalyst in dehydrogenative cross-coupling reactions. Herein, a novel zinc-catalyzed dehydrogenative C(sp(2) )H/C(sp)H cross-coupling of terminal alkynes with aldehydes was developed, and provides a simple way to access ynones from readily available materials under mild reaction conditions. Good reaction selectivity can be achieved with a 1:1 ratio of terminal alkyne and aldehyde. Various terminal alkynes and aldehydes are suitable in this transformation. PMID:26564779

  18. Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts

    PubMed Central

    2016-01-01

    Alumina-supported Pt is one of the major industrial catalysts for light alkane dehydrogenation. This catalyst loses activity during reaction, with coke formation often considered as the reason for deactivation. As we show in this study, the amount and nature of carbon deposits do not directly correlate with the loss of activity. Rather, it is the transformation of subnanometer Pt species into larger Pt nanoparticles that appears to be responsible for the loss of catalytic activity. Surprisingly, a portion of the Sn remains atomically dispersed on the alumina surface in the spent catalyst and helps in the redispersion of the Pt. In the absence of Sn on the alumina support, the larger Pt nanoparticles formed during reaction are not redispersed during oxidative regeneration. It is known that Sn is added as a promoter in the industrial catalyst to help in achieving high propene selectivity and to minimize coke formation. This work shows that an important role of Sn is to help in the regeneration of Pt, by providing nucleation sites on the alumina surface. Aberration-corrected scanning transmission electron microscopy helps to provide unique insights into the operating characteristics of an industrially important catalyst by demonstrating the role of promoter elements, such as Sn, in the oxidative regeneration of Pt on γ-Al2O3. PMID:27076991

  19. Revisitation of the βCl-elimination reaction of D-amino acid oxidase: new interpretation of the reaction that sparked flavoprotein dehydrogenation mechanisms.

    PubMed

    Ghisla, Sandro; Pollegioni, Loredano; Molla, Gianluca

    2011-11-25

    D-amino acid oxidase (DAAO) from pig has been reported to catalyze the β-elimination of Cl(-) from βCl-D-alanine via abstraction of the substrate α-H as H(+) ("carbanion mechanism") (Walsh, C. T., Schonbrunn, A., and Abeles, R. H. (1971) J. Biol. Chem. 246, 6855-6866). In view of the fundamental mechanistic importance of this reaction and of the recent reinterpretation of the DAAO dehydrogenation step as occurring via a hydride mechanism, we reinvestigated the elimination reaction using yeast DAAO. That enzyme catalyzes the same reactions as the pig enzyme but with a much higher efficiency and a substantially different kinetic behavior. The reaction is initiated by a very rapid and fully reversible dehydrogenation step. This leads to an equilibrium (k(on) ≈ k(reverse)) between the complexes of oxidized enzyme-βCl-D-alanine and reduced enzyme-βCl-iminopyruvate. In the presence of O(2) the latter complex can partition between an oxidative half-reaction and elimination of Cl(-), which proceeds at a rate of ≈50 s(-1). This step forms a complex between oxidized enzyme and enamine that is characterized by a charge transfer absorption (which describes its rates of formation and decay). A minimal scheme that lists relevant steps of the reductive and oxidative half-reactions and elimination pathways along with the estimate of the corresponding rate constants is presented. β-Elimination of Cl(-) is proposed to originate at the locus of the enzyme-βCl-iminopyruvate complex. A chemical mechanism that can account for elimination is discussed in detail. PMID:21949129

  20. A first-principles study of the tuning effect of a Fe2O3 cluster on the dehydrogenation properties of a LiBH4 (001) surface.

    PubMed

    Liu, Chuan; Huang, Shiping

    2016-07-01

    First-principles calculations were performed to investigate the effects of a Fe2O3 cluster on the structural, electronic and dehydrogenation properties of a LiBH4 (001) surface. O atoms interact with Li atoms to form Li-O bonds, corresponding to an experimentally found ternary Li-Fe oxide. The DOS results show that the coupling effect of the spin-unrestricted Fe d orbitals, especially the spin-up state of Fe d orbitals, plays a crucial role in the hybridizations of H s, B p, and Fe d orbitals. The Fe2O3 cluster will serve as the nucleation site of surface activation at the surface of LiBH4 to improve the dehydrogenation kinetics of LiBH4. The doping of the Fe2O3 cluster is advantageous to facilitate the release of a H2 molecule from not only the surface layer but also the inner layer of the LiBH4 (001) surface. PMID:27302658

  1. Development of an eight-step kinetics mechanism for propane and its application in a transient, thin gap, engine model

    SciTech Connect

    Kiehne, T.M.

    1985-01-01

    An accurate eight-step kinetics mechanism for the oxidation of propane, based on previous research, was developed in ignition delay studies and investigations of freely propagating and quenching flames. Results from a detailed kinetics model and available experimental data were used for comparison and verification. One-dimensional transient calculations were performed at pressures ranging from one to 40 atmospheres, unburned gas temperatures from 400 to 500 K, and near stoichiometric equivalence ratios. The detailed kinetics results confirm the existence of extensive post-quench burnup of propane after the time of flame-arrival at the wall. However, the range of calculations at engine-like conditions using a higher molecular weight fuel than used in previous studies indicates that hydrocarbons other than the fuel contribute significantly to the total of all unburned hydrocarbons in the wall quench layer. Based on the detailed kinetics results, an eight-step kinetics model developed from experiment is shown to be deficient in certain key areas. Therefore, it is modified to improve representation of the induction region, flame speed, postflame region, wall quench behavior, and unburned hydrocarbon evolution. Correlations that extend the model to a wider pressure range and fuel-rich equivalence ratios are developed.

  2. An analysis of US propane markets, winter 1996-1997

    SciTech Connect

    1997-06-01

    In late summer 1996, in response to relatively low inventory levels and tight world oil markets, prices for crude oil, natural gas, and products derived from both began to increase rapidly ahead of the winter heating season. Various government and private sector forecasts indicated the potential for supply shortfalls and sharp price increases, especially in the event of unusually severe winter weather. Following a rapid runup in gasoline prices in the spring of 1996, public concerns were mounting about a possibly similar situation in heating fuels, with potentially more serious consequences. In response to these concerns, the Energy Information Administration (EIA) participated in numerous briefings and meetings with Executive Branch officials, Congressional committee members and staff, State Energy Offices, and consumers. EIA instituted a coordinated series of actions to closely monitor the situation and inform the public. This study constitutes one of those actions: an examination of propane supply, demand, and price developments and trends.

  3. Exhaust gas measurements in a propane fueled swirl stabilized combustor

    NASA Technical Reports Server (NTRS)

    Aanad, M. S.

    1982-01-01

    Exhaust gas temperature, velocity, and composition are measured and combustor efficiencies are calculated in a lean premixed swirl stabilized laboratory combustor. The radial profiles of the data between the co- and the counter swirl cases show significant differences. Co-swirl cases show evidence of poor turbulent mixing across the combustor in comparison to the counter-swirl cases. NO sub x levels are low in the combustor but substantial amounts of CO are present. Combustion efficiencies are low and surprisingly constant with varying outer swirl in contradiction to previous results under a slightly different inner swirl condition. This difference in the efficiency trends is expected to be a result of the high sensitivity of the combustor to changes in the inner swirl. Combustor operation is found to be the same for propane and methane fuels. A mechanism is proposed to explain the combustor operation and a few important characteristics determining combustor efficiency are identified.

  4. Propane spectral resolution enhancement by the maximum entropy method

    NASA Technical Reports Server (NTRS)

    Bonavito, N. L.; Stewart, K. P.; Hurley, E. J.; Yeh, K. C.; Inguva, R.

    1990-01-01

    The Burg algorithm for maximum entropy power spectral density estimation is applied to a time series of data obtained from a Michelson interferometer and compared with a standard FFT estimate for resolution capability. The propane transmittance spectrum was estimated by use of the FFT with a 2 to the 18th data sample interferogram, giving a maximum unapodized resolution of 0.06/cm. This estimate was then interpolated by zero filling an additional 2 to the 18th points, and the final resolution was taken to be 0.06/cm. Comparison of the maximum entropy method (MEM) estimate with the FFT was made over a 45/cm region of the spectrum for several increasing record lengths of interferogram data beginning at 2 to the 10th. It is found that over this region the MEM estimate with 2 to the 16th data samples is in close agreement with the FFT estimate using 2 to the 18th samples.

  5. Chemical kinetic reaction mechanism for the combustion of propane

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1984-01-01

    A detailed chemical kinetic reaction mechanism for the combustion of propane is presented and discussed. The mechanism consists of 27 chemical species and 83 elementary chemical reactions. Ignition and combustion data as determined in shock tube studies were used to evaluate the mechanism. Numerical simulation of the shock tube experiments showed that the kinetic behavior predicted by the mechanism for stoichiometric mixtures is in good agrement with the experimental results over the entire temperature range examined (1150-2600K). Sensitivity and theoretical studies carried out using the mechanism revealed that hydrocarbon reactions which are involved in the formation of the HO2 radical and the H2O2 molecule are very important in the mechanism and that the observed nonlinear behavior of ignition delay time with decreasing temperature can be interpreted in terms of the increased importance of the HO2 and H2O2 reactions at the lower temperatures.

  6. Amide α,β-Dehydrogenation Using Allyl-Palladium Catalysis and a Hindered Monodentate Anilide.

    PubMed

    Chen, Yifeng; Turlik, Aneta; Newhouse, Timothy R

    2016-02-01

    A practical and direct method for the α,β-dehydrogenation of amides is reported using allyl-palladium catalysis. Critical to the success of this process was the synthesis and application of a novel lithium N-cyclohexyl anilide (LiCyan). The reaction conditions tolerate a wide variety of substrates, including those with acidic heteroatom nucleophiles. PMID:26790471

  7. Kinetics and mechanism of dehydrogenation of 1-tetralone on an alumina-nickel catalyst

    SciTech Connect

    Kheifets, M.V.; Sibarov, D.A.; Sobolev, V.V.; Petrova, N.A.

    1986-10-20

    The first-order reaction of the dehydrogenation of 1-teralone on alumina-nickel catalysts was ascertained. A reaction mechanism was proposed which takes into account the need for formation of the enol form of 1-tetralone as an intermediate product.

  8. Versatile dehydrogenative alcohol silylation catalyzed by Cu(I)-phosphine complex.

    PubMed

    Ito, Hajime; Watanabe, Akiko; Sawamura, Masaya

    2005-04-28

    [reaction: see text] Cu(I) complexes of xanthane-based diphosphines were versatile catalysts for dehydrogenative alcohol silylation, exhibiting high activity and broad substrate scope. Highly selective silylation of 1-decanol over 2-decanol is possible even with a silylating reagent of small steric demand such as HSiMe(2)Ph or HSiEt(3). PMID:15844927

  9. Microstructural characterization of dehydrogenated products of the LiBH4-YH3 composite.

    PubMed

    Kim, Ji Woo; Kim, Kee-Bum; Shim, Jae-Hyeok; Cho, Young Whan; Oh, Kyu Hwan

    2014-12-01

    The dehydrogenated microstructure of the lithium borohydride-yttrium hydride (LiBH4-YH3) composite obtained at 350°C under 0.3 MPa of hydrogen and static vacuum was investigated by transmission electron microscopy combined with a focused ion beam technique. The dehydrogenation reaction between LiBH4 and YH3 into LiH and YB4 takes place under 0.3 MPa of hydrogen, which produces YB4 nano-crystallites that are uniformly distributed in the LiH matrix. This microstructural feature seems to be beneficial for rehydrogenation of the dehydrogenation products. On the other hand, the dehydrogenation process is incomplete under static vacuum, leading to the unreacted microstructure, where YH3 and YH2 crystallites are embedded in LiBH4 matrix. High resolution imaging confirmed the presence of crystalline B resulting from the self-decomposition of LiBH4. However, Li2B12H12, which is assumed to be present in the LiBH4 matrix, was not clearly observed. PMID:25347999

  10. Convenient metal embedment into mesoporous silica channels for high catalytic performance in AB dehydrogenation.

    PubMed

    Park, Jin-Hyung; Kim, Sung-Kwan; Kim, Han Sung; Cho, Yong Jae; Park, Jeunghee; Lee, Kyung Eun; Yoon, Chang Won; Nam, Suk Woo; Kang, Sang Ook

    2013-11-28

    The infiltration of palladium nanoparticles (PdNPs) into the channels of SBA-15 was conveniently achieved via an incipient wetness procedure employing a tetraglyme solution. Electron tomography demonstrated that PdNPs were outgrown preferentially from the channels. The resultant Pd/SBA-15 showed high performance in the dehydrogenation kinetics of ammonia borane. PMID:24121869

  11. Binding mechanism of sulfur and dehydrogenated polyacrylonitrile in sulfur/polymer composite cathode

    NASA Astrophysics Data System (ADS)

    Doan, The Nam Long; Ghaznavi, Mahmoudreza; Zhao, Yan; Zhang, Yongguang; Konarov, Aishuak; Sadhu, Mikhail; Tangirala, Ravichandra; Chen, P.

    2013-11-01

    A composite consisting of sulfur/dehydrogenated polyacrylonitrile is one of the most promising cathode materials for use in rechargeable lithium-sulfur batteries. However, the reported sulfur contents have been low, less than 50 wt%, which compromise the intrinsic high specific capacity and energy of elemental sulfur and hence decrease significantly the specific energy of the composite. To identify the potential to further increase the sulfur content, we elucidate the binding mechanism of sulfur and polyacrylonitrile in their composite. The heat treatment experiments at varying timespans with excess sulfur showed a constancy of sulfur content after a critical length of timespan, indicating the saturation of sulfur in the structure of dehydrogenated polyacrylonitrile. Based on molecular structure and size consideration, it is proposed that the binding involves the formation of an 8 membered ring of sulfur embedded between 4 heterocyclic rings of dehydrogenated polyacrylonitrile. From this model and experimental results, we show that there exists an upper limit of sulfur content in the sulfur/dehydrogenated polyacrylonitrile composite at 56 wt%.

  12. CHARACTERIZING THE INFRARED SPECTRA OF SMALL, NEUTRAL, FULLY DEHYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS

    SciTech Connect

    Mackie, C. J.; Peeters, E.; Cami, J.; Bauschlicher, C. W. Jr.

    2015-02-01

    We present the results of a computational study to investigate the infrared spectroscopic properties of a large number of polycyclic aromatic hydrocarbon (PAH) molecules and their fully dehydrogenated counterparts. We constructed a database of fully optimized geometries for PAHs that is complete for eight or fewer fused benzene rings, thus containing 1550 PAHs and 805 fully dehydrogenated aromatics. A large fraction of the species in our database have clearly non-planar or curved geometries. For each species, we determined the frequencies and intensities of their normal modes using density functional theory calculations. Whereas most PAH spectra are fairly similar, the spectra of fully dehydrogenated aromatics are much more diverse. Nevertheless, these fully dehydrogenated species show characteristic emission features at 5.2 μm, 5.5 μm, and 10.6 μm; at longer wavelengths, there is a forest of emission features in the 16-30 μm range that appears as a structured continuum, but with a clear peak centered around 19 μm. We searched for these features in Spitzer-IRS spectra of various positions in the reflection nebula NGC 7023. We find a weak emission feature at 10.68 μm in all positions except that closest to the central star. We also find evidence for a weak 19 μm feature at all positions that is not likely due to C{sub 60}. We interpret these features as tentative evidence for the presence of a small population of fully dehydrogenated PAHs, and discuss our results in the framework of PAH photolysis and the formation of fullerenes.

  13. Hydrogen generation from hydrolytic dehydrogenation of hydrazine borane by poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Tunç, Nihat; Abay, Bayram; Rakap, Murat

    2015-12-01

    Poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles (3.5 ± 1.0 nm) are efficient catalysts in the hydrolytic dehydrogenation of hydrazine borane to give hydrogen gas. The catalyst, prepared by reduction of palladium metal ion in ethanol/water mixture by an alcohol reduction method, is durable and efficient catalysts for hydrogen generation from the hydrolytic dehydrogenation of hydrazine borane even at very low concentrations and temperature, providing an average turnover frequency of 42.9 min-1 with an activation energy of 54.5 ± 2 kJ mol-1 for the hydrolytic dehydrogenation of hydrazine borane.

  14. Effect of temperature and pressure on the dynamics of nanoconfined propane

    SciTech Connect

    Gautam, Siddharth Liu, Tingting Welch, Susan; Cole, David; Rother, Gernot; Jalarvo, Niina; Mamontov, Eugene

    2014-04-24

    We report the effect of temperature and pressure on the dynamical properties of propane confined in nanoporous silica aerogel studied using quasielastic neutron scattering (QENS). Our results demonstrate that the effect of a change in the pressure dominates over the effect of temperature variation on the dynamics of propane nano-confined in silica aerogel. At low pressures, most of the propane molecules are strongly bound to the pore walls, only a small fraction is mobile. As the pressure is increased, the fraction of mobile molecules increases. A change in the mechanism of motion, from continuous diffusion at low pressures to jump diffusion at higher pressures has also been observed.

  15. Cool Flames in Propane-Oxygen Premixtures at Low and Intermediate Temperatures at Reduced-Gravity

    NASA Technical Reports Server (NTRS)

    Pearlman, Howard; Foster, Michael; Karabacak, Devrez

    2003-01-01

    The Cool Flame Experiment aims to address the role of diffusive transport on the structure and the stability of gas-phase, non-isothermal, hydrocarbon oxidation reactions, cool flames and auto-ignition fronts in an unstirred, static reactor. These reactions cannot be studied on Earth where natural convection due to self-heating during the course of slow reaction dominates diffusive transport and produces spatio-temporal variations in the thermal and thus species concentration profiles. On Earth, reactions with associated Rayleigh numbers (Ra) less than the critical Ra for onset of convection (Ra(sub cr) approx. 600) cannot be achieved in laboratory-scale vessels for conditions representative of nearly all low-temperature reactions. In fact, the Ra at 1g ranges from 10(exp 4) - 10(exp 5) (or larger), while at reduced-gravity, these values can be reduced two to six orders of magnitude (below Ra(sub cr)), depending on the reduced-gravity test facility. Currently, laboratory (1g) and NASA s KC-135 reduced-gravity (g) aircraft studies are being conducted in parallel with the development of a detailed chemical kinetic model that includes thermal and species diffusion. Select experiments have also been conducted at partial gravity (Martian, 0.3gearth) aboard the KC-135 aircraft. This paper discusses these preliminary results for propane-oxygen premixtures in the low to intermediate temperature range (310- 350 C) at reduced-gravity.

  16. Soot formation and temperature field structure in laminar propane-air diffusion flames at elevated pressures

    SciTech Connect

    Bento, Decio S.; Guelder, OEmer L.; Thomson, Kevin A.

    2006-06-15

    The effect of pressure on soot formation and the structure of the temperature field was studied in coflow propane-air laminar diffusion flames over the pressure range of 0.1 to 0.73 MPa in a high-pressure combustion chamber. The fuel flow rate was selected so that the soot was completely oxidized within the visible flame and the flame was stable at all pressures. Spectral soot emission was used to measure radially resolved soot volume fraction and soot temperature as a function of pressure. Additional soot volume fraction measurements were made at selected heights using line-of-sight light attenuation. Soot concentration values from these two techniques agreed to within 30% and both methods exhibited similar trends in the spatial distribution of soot concentration. Maximum line-of-sight soot concentration along the flame centerline scaled with pressure; the pressure exponent was about 1.4 for pressures between 0.2 and 0.73 MPa. Peak carbon conversion to soot, defined as the percentage of fuel carbon content converted to soot, also followed a power-law dependence on pressure, where the pressure exponent was near to unity for pressures between 0.2 and 0.73 MPa. Soot temperature measurements indicated that the overall temperatures decreased with increasing pressure; however, the temperature gradients increased with increasing pressure. (author)

  17. State heating oil and propane program: Final report. Survey of No.2 heating oil and propane prices at the retail level, October 1997 through March 1998

    SciTech Connect

    1998-11-01

    The Energy Efficiency Division of the Vermont Department of Public Service (DPS) monitored the price and inventory of residential heating oil and propane during the 1997--98 heating season under a grant from the US Department of Energy`s Energy Information Administration (EIA). DPS staff collected data biweekly between October 5, 1997 and March 16, 1998 on the retail price of {number_sign}2 home heating oil and propane by telephone survey. Propane price quoted was based on the rate for a residential home heating customer using 1,000+ per year. The survey included a sample of fuel dealers selected by the EIA, plus additional dealers and fuels selected by the DPS. The EIA weighted, analyzed, and reported the data collected from their sample.

  18. PHYSICAL PROPERTIES OF FLUORINATED PROPANE AND BUTANE DERIVATIVES AS ALTERNATIVE REFRIGERANTS

    EPA Science Inventory

    Physical property measurements are presented for 24 fluorinated propane and butane derivatives and one fluorinated ether. These measurements include melting point, boiling point, vapor pressure below the boiling point, heat of vaporization at the boiling point, critical propertie...

  19. Effect of preprocessing and compressed propane extraction on quality of cilantro (Coriandrum sativum L.).

    PubMed

    Sekhon, Jasreen K; Maness, Niels O; Jones, Carol L

    2015-05-15

    Dehydration leads to quality defects in cilantro such as loss in structure, color, aroma and flavor. Solvent extraction with compressed propane may improve the dehydrated quality. In the present study, effect of drying temperature, particle size, and propane extraction on color, volatile composition, and fatty acid composition of cilantro was evaluated. Cilantro was dehydrated (40°C or 60°C), size reduced and separated into three particles sizes, and extracted with compressed propane at 21-27°C. Major volatile compounds found in dried cilantro were E-2-tetradecenal, dodecanal, E-2-dodecenal, and tetradecanal. Major fatty acids were linoleic acid and α-linolenic acid. Drying at 60°C compared to 40°C resulted in better preservation of color (decrease in browning index values) and volatile compounds. Propane extraction led to a positive change in color values and a decrease in volatile composition, oil content, and fatty acid composition. PMID:25577087

  20. Short-Term Energy Outlook Model Documentation: Regional Residential Propane Price Model

    EIA Publications

    2009-01-01

    The regional residential propane price module of the Short-Term Energy Outlook (STEO) model is designed to provide residential retail price forecasts for the 4 Census regions: Northeast, South, Midwest, and West.

  1. THERMODYNAMIC EVALUATION OF FLUORINATED ETHERS, ETHANES, AND PROPANES AS ALTERNATIVE REFRIGERANTS

    EPA Science Inventory

    The visuals, part of a thermodynamic evaluation of fluorinated ethers, ethanes, and propanes as alternative refrigerants, are a useful tool in comparing new chemicals to existing refrigerants in vapor compression cycles. hey present the required suction superheat and the performa...

  2. School Districts Move to the Head of the Class with Propane

    SciTech Connect

    2016-01-01

    Propane has been a proven fuel for buses for decades. For the first time in 2007, Blue Bird rolled out a propane school bus using direct liquid injection, which was later followed by Thomas Built Buses and Navistar. Because this new technology is much more reliable than previous designs, it is essentially reintroducing propane buses to many school districts. During this same time period, vehicle emissions standards have tightened. To meet them, diesel engine manufacturers have added diesel particulate filters (DPF) and, more recently, selective catalytic reduction (SCR) systems. As an alternative to diesel buses with these systems, many school districts have looked to other affordable, clean alternatives, and they've found that propane fits the bill.

  3. Deposit formation in hydrocarbon rocket fuels with an evaluation of a propane heat transfer correlation

    NASA Technical Reports Server (NTRS)

    Masters, P. A.; Aukerman, C. A.

    1982-01-01

    A high pressure fuel coking testing apparatus was designed and developed and was used to evaluate thermal decomposition limits and carbon decomposition rates in heated copper tubes for hydrocarbon fuels. A commercial propane (90% grade) and chemically pure (CP) propane were tested. Heat transfer to supercritical propane was evaluated at 136 atm, bulk fluid velocities of 6 to 30 m/s, and tube wall temperatures in the range of 422 to 811 K. A forced convection heat transfer correlation developed in a previous test effort verified a prediction of most of the experimental data within a + or - 30% range, with good agreement for the CP propane data. No significant differences were apparent in the predictions derived from the correlation when the carbon resistance was included with the film resistance. A post-test scanning electron microprobe analysis indicated occurrences of migration and interdiffusion of copper into the carbon deposit.

  4. Tailored formation of N-doped nanoarchitectures by diffusion-controlled on-surface (cyclo)dehydrogenation of heteroaromatics.

    PubMed

    Pinardi, Anna Lisa; Otero-Irurueta, Gonzalo; Palacio, Irene; Martinez, Jose Ignacio; Sanchez-Sanchez, Carlos; Tello, Marta; Rogero, Celia; Cossaro, Albano; Preobrajenski, Alexei; Gómez-Lor, Berta; Jancarik, Andrej; Stará, Irena G; Starý, Ivo; Lopez, M Francisca; Méndez, Javier; Martin-Gago, Jose Angel

    2013-04-23

    Surface-assisted cyclodehydrogenation and dehydrogenative polymerization of polycyclic (hetero)aromatic hydrocarbons (PAH) are among the most important strategies for bottom-up assembly of new nanostructures from their molecular building blocks. Although diverse compounds have been formed in recent years using this methodology, a limited knowledge on the molecular machinery operating at the nanoscale has prevented a rational control of the reaction outcome. We show that the strength of the PAH-substrate interaction rules the competitive reaction pathways (cyclodehydrogenation versus dehydrogenative polymerization). By controlling the diffusion of N-heteroaromatic precursors, the on-surface dehydrogenation can lead to monomolecular triazafullerenes and diazahexabenzocoronenes (N-doped nanographene), to N-doped oligomeric or polymeric networks, or to carbonaceous monolayers. Governing the on-surface dehydrogenation process is a step forward toward the tailored fabrication of molecular 2D nanoarchitectures distinct from graphene and exhibiting new properties of fundamental and technological interest. PMID:23506342

  5. Tandem ammonia borane dehydrogenation/alkene hydrogenation mediated by [Pd(NHC)(PR3)] (NHC = N-heterocyclic carbene) catalysts.

    PubMed

    Hartmann, Caroline E; Jurčík, Václav; Songis, Olivier; Cazin, Catherine S J

    2013-02-01

    [Pd(NHC)(PR(3))] complexes were shown to be active catalysts in the dehydrogenation of ammonia borane and the subsequent hydrogenation of unsaturated compounds at very low catalyst loadings (0.05 mol% for some substrates). PMID:23254388

  6. Improvement of dehydrogenation kinetics of LiBH4 dispersed on modified multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Agresti, Filippo; Khandelwal, Ashish; Capurso, Giovanni; Lo Russo, Sergio; Maddalena, Amedeo; Principi, Giovanni

    2010-02-01

    The dehydrogenation kinetics of LiBH4 dispersed on multi-walled carbon nanotubes (MWCNTs) by the solvent infiltration technique has been studied. Commercial MWCNTs were ball-milled for different milling times in order to increase the specific surface area (SSA) as measured by the BET technique. Thermal programmed desorption measurements have been performed using a Sievert's apparatus on samples with different SSA of MWCNTs and different LiBH4 to MWCNT ratio. Pressure composition isotherms (PCI) have been obtained at different temperatures in order to estimate the ΔH and ΔS of dehydrogenation. It has been observed that the dispersion of LiBH4 on MWCNTs leads to a lower dehydrogenation temperature compared to pure LiBH4. Moreover, the dehydrogenation temperature further decreases with increasing MWCNT surface area. An interpretation of the kinetic effect is proposed.

  7. Pd(OAc)2-catalyzed dehydrogenative C–H activation: An expedient synthesis of uracil-annulated β-carbolinones

    PubMed Central

    Mondal, Biplab; Hazra, Somjit; Panda, Tarun K

    2015-01-01

    Summary An intramolecular dehydrogenative C–H activation enabled an efficient synthesis of an uracil-annulated β-carbolinone ring system. The reaction is simple, efficient and high yielding (85–92%). PMID:26425190

  8. Dehydrogenation of ethylbenzene to styrene using Pt, Mo, and Pt-Mo catalysts supported on clay nanocomposites.

    PubMed

    Morán, Cesar; González, Eduardo; Sánchez, Jorge; Solano, Roger; Carruyo, Gabriela; Moronta, Alexander

    2007-11-01

    A synthetic clay (TS-1) was modified with a nonionic surfactant (IGEPAL CO-720) and magnesium oxide. The resulting solid was used as a support of Pt, Mo, and Pt-Mo catalysts. The catalysts were prepared by wet impregnation with aqueous solutions of H(2)PtCl(6)6H(2)O and (NH(4))(6)-Mo(7)O(24)4H(2)O. In both monometallic and bimetallic catalysts, the molybdenum content was 3 wt% and the platinum content was 0.5 or 1 wt%. The surface area of the starting material was 454 m(2)/g and after the modification treatment with IGEPAL it increased up to 649 m(2)/g, while platinum and molybdenum catalysts showed surface areas between 495 and 550 m(2)/g. The reduction profiles showed different Pt and Mo species and the existence of metal-support interactions. The reduced catalysts were more active than those in the unreduced form. The most active catalysts for the ethylbenzene dehydrogenation were those of monometallic Pt (0.5 and 1 wt%) with a maximum styrene conversion around 50%. The presence of Mo species masked Pt atoms and reduced the activity. PMID:17603070

  9. Mutagenic activity of halogenated propanes and propenes: effect of bromine and chlorine positioning.

    PubMed

    Låg, M; Omichinski, J G; Dybing, E; Nelson, S D; Søderlund, E J

    1994-10-01

    A series of halogenated propanes and propenes were studied for mutagenic effects in Salmonella typhimurium TA100 in the absence or presence of NADPH plus liver microsomes from phenobarbital-induced rats as an exogenous metabolism system. The cytotoxic and mutagenic effects of the halogenated propane 1,2-dibromo-3-chloropropane (DBCP) has previously been studied in our laboratories. These studies showed that metabolic activation of DBCP was required to exert its detrimental effects. All of the trihalogenated propane analogues were mutagenic when the microsomal activation system was included. The highest mutagenic activity was obtained with 1,2,3-tribromopropane, with approximately 50-fold higher activity than the least mutagenic trihalogenated propane, 1,2,3-trichloropropane. The order of mutagenicity was as follows: 1,2,3-tribromopropane > or = 1,2-dibromo- 3-chloropropane > 1,3-dibromo-2-chloropropane > or = 1,3-dichloro-2-bromopropane > 1-bromo-2,3-dichloropropane > 1,2,3-trichloropropane. Compared to DBCP, the dihalogenated propanes were substantially less mutagenic. Only 1,2-dibromopropane was mutagenic and its mutagenic potential was approximately 1/30 of that of DBCP. In contrast to DBCP, 1,2-dibromopropane showed similar mutagenic activity with and without the addition of an activation system. The halogenated propenes 2,3-dibromopropene and 2-bromo-3-chloropropene were mutagenic to the bacteria both in the absence and presence of the activation system, whereas 2,3-dichloropropene did not show any mutagenic effect. The large differences in mutagenic potential between the various halogenated propanes and propenes are proposed to be due to the formation of different possible proximate and ultimate mutagenic metabolites resulting from the microsomal metabolism of the various halogenated propanes and propenes, and to differences in the rate of formation of the metabolites. Pathways are proposed for the formation of genotoxic metabolites of di- and trihalogenated

  10. 40 CFR 1065.341 - CVS and batch sampler verification (propane check).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... reference mass or a reference flow rate of C3H8 as a tracer gas in a CVS. Note that if you use a reference... gas assumptions in § 1065.640 and § 1065.642. The propane check compares the calculated mass of... for the propane check as follows: (1) If you use a reference mass of C3H8 instead of a reference...

  11. Production of high-octane, unleaded motor fuel by alkylation of isobutane with isoamylenes obtained by dehydrogenation of isopentane

    SciTech Connect

    Hutson, T. Jr.; Hann, P.D.

    1981-01-31

    A process combination, with inter-cooperation, for producing high-octane alkylates comprising (a) dehydrogenating isopentane to isopentenes (amylenes), (b) introducing the mixture of said amylenes and unconverted isopentane into an HF alkylation unit for reaction with fresh or recycled isobutane, (c) separating the alkylation products into high octane alkylates, isopentane (for recycling to the dehydrogenation reactor) and isobutane (for recycling to the alkylation reactor).

  12. Measurement of position-specific 13C isotopic composition of propane at the nanomole level

    NASA Astrophysics Data System (ADS)

    Gilbert, Alexis; Yamada, Keita; Suda, Konomi; Ueno, Yuichiro; Yoshida, Naohiro

    2016-03-01

    We have developed a novel method for analyzing intramolecular carbon isotopic distribution of propane as a potential new tracer of its origin. The method is based on on-line pyrolysis of propane followed by analysis of carbon isotope ratios of the pyrolytic products methane, ethylene and ethane. Using propane samples spiked with 13C at the terminal methyl carbon, we characterize the origin of the pyrolytic fragments. We show that the exchange between C-atoms during the pyrolytic process is negligible, and thus that relative intramolecular isotope composition can be calculated. Preliminary data from 3 samples show that site-preference (SP) values, defined as the difference of δ13C values between terminal and sub-terminal C-atom positions of propane, range from -1.8‰ to -12.9‰. In addition, SP value obtained using our method for a thermogenic natural gas sample is consistent with that expected from theoretical models of thermal cracking, suggesting that the isotope fractionation associated with propane pyrolysis is negligible. The method will provide novel insights into the characterization of the origin of propane and will help better understand the biogeochemistry of natural gas deposits.

  13. Visible-light induced oxidant-free oxidative cross-coupling for constructing allylic sulfones from olefins and sulfinic acids.

    PubMed

    Zhang, Guoting; Zhang, Lingling; Yi, Hong; Luo, Yi; Qi, Xiaotian; Tung, Chen-Ho; Wu, Li-Zhu; Lei, Aiwen

    2016-08-16

    An oxidant-free dehydrogenative sulfonylation of α-methyl-styrene derivatives was developed for the construction of allylic sulfones by using eosin Y as a photosensitizer in conjunction with a cobaloxime catalyst. The process features a low-cost metal catalyst and atom economy, which provides an appealing strategy for future synthetic chemistry. PMID:27481529

  14. Dehydrogenative Cross-Coupling Reaction between N-Aryl α-Amino Acid Esters and Phenols or Phenol Derivative for Synthesis of α-Aryl α-Amino Acid Esters.

    PubMed

    Salman, Muhammad; Zhu, Zhi-Qiang; Huang, Zhi-Zhen

    2016-04-01

    A novel dehydrogenative cross-coupling (DCC) reaction between N-arylglycine esters and phenols or 1,3,5-trimethoxybenzene was developed by copper catalysis using di-tert-butyl peroxide (DTBP) as an oxidant. Under optimized conditions, a range of N-arylglycine esters 1 underwent the DCC reaction smoothly with various phenols 2 or 1,3,5-trimethoxybenzene 4 to give desired α-aryl α -amino acid esters 3 or 5, respectively, with high ortho regioselectivities in a moderate to excellent yield. A possible mechanism involving aromatic electrophilic substitution is proposed. PMID:26984111

  15. The ozone formation potential of 1-bromo-propane.

    PubMed

    Whitten, Gary Z; Cohen, Jonathan P; Myers, Thomas C; Carter, William P L

    2003-03-01

    1-Bromo-propane (1-BP) is a replacement for high-end chlorofluorocarbon (HCFC) solvents. Its reaction rate constant with the OH radical is, on a weight basis, significantly less than that of ethane. However, the overall smog formation chemistry of 1-BP appears to be very unusual compared with typical volatile organic compounds (VOCs) and relatively complex because of the presence of bromine. In smog chamber experiments, 1-BP initially shows a faster ozone build-up than what would be expected from ethane, but the secondary products containing bromine tend to destroy ozone such that 1-BP can have a net overall negative reactivity. Alternative sets of reactions are offered to explain this unusual behavior. Follow-up studies are suggested to resolve the chemistry. Using one set of bromine-related reactions in a photochemical grid model shows that 1-BP would be less reactive toward peak ozone formation than ethane with a trend toward even lower ozone impacts in the future. PMID:12661686

  16. Autothermal reforming of propane over Ni-based hydrotalcite catalysts.

    PubMed

    Park, Sun-Young; Kim, Jong-Ho; Moon, Dong-Ju; Park, Nam-Cook; Kim, Young-Chul

    2010-05-01

    Ni-based hydrotalcite catalysts were investigated for ATR of propane in a fixed-bed flow reactor. The reactions were carried out with a H2O/C/O2 stream ratio of 3/1/0.73 at temperatures ranging from 300 to 700 degrees C. The solvents used in the manufacture of Ni-based catalysts noble metal/Ni/MgAl catalysts or substituted active material were changed in order to decrease the level of catalyst deactivation. The use of a mixture of ethanol and water during the formation of the Pd-Ni/MgAl catalyst produced a higher hydrogen yield than that using water only. In addition, the use of acetone in the synthesis of Ru-Ni/MgAl catalyst produced a higher hydrogen yield than using water only. This shows that the solvents used for the noble metals affect the degree of dispersion and particle size of the nickel and prevented carbon deposition resulting in the enhanced hydrogen selectivity and catalyst activity. Active metals were substituted during the preparation of hydrotalcite catalysts. Among the catalysts prepared with various ratio (Ni:Fe) tested at high temperature, the ratio, Ni:Fe = 75:25, showed best performance. There was less sintering of Ni particles due to substitution of the active metal at the optimal ratio. PMID:20358916

  17. Hydrogen and Nitrogen Broadened Ethane and Propane Absorption Cross Sections

    NASA Astrophysics Data System (ADS)

    Hargreaves, Robert J.; Appadoo, Dominique; Billinghurst, Brant E.; Bernath, Peter F.

    2015-06-01

    High-resolution infrared absorption cross sections are presented for the ν9 band of ethane (C2H6) at 823 cm-1. These cross sections make use of spectra recorded at the Australian Synchrotron using a Fourier transform infrared spectrometer with maximum resolution of 0.00096 cm-1. The spectra have been recorded at 150, 120 and 90 K for hydrogen and nitrogen broadened C2H6. They cover appropriate temperatures, pressures and broadening gases associated with the atmospheres of the Outer Planets and Titan, and will improve atmospheric retrievals. The THz/Far-IR beamline at the Australian Synchrotron is unique in combining a high-resolution Fourier transform spectrometer with an 'enclosive flow cooling' (EFC) cell designed to study molecules at low temperatures. The EFC cell is advantageous at temperatures for which the vapor pressure is very low, such as C2H6 at 90 K. Hydrogen broadened absorption cross sections of propane between 700 and 1200 cm-1 will also be presented based on spectra obtained at the Canadian Light Source.

  18. Reversible Dehydrogenation of Magnesium Borohydride to Magnesium Triborane in the Solid State Under Moderate Conditions

    SciTech Connect

    Chong, Marina; Karkamkar, Abhijeet J.; Autrey, Thomas; Orimo, Shin-ichi; Jalisatgi, Satish; Jensen, Craig M.

    2011-02-17

    Thermal decomposition of magnesium borohydride, Mg(BH4)2, in the solid state was studied by a combination of PCT, TGA/MS and NMR spectroscopy. Dehydrogenation of Mg(BH4)2 at 200 °C, results in the highly selective formation of magnesium triborane, Mg(B3H8)2. This process is reversible at 250 °C under 120 atm H2. Dehydrogenation at higher temperature, > 300 °C, produces a complex mixture of polyborane species. Solution phase 11B NMR spectra of the hydrolyzed decomposition products reveals the formation of the B3H8 anion, boric acid from hydrolysis of the unstable polyboranes (BnHx) (n = 3-11, x >8), and the closoborane B12H12 dianion as a minor product. A BH condensation mechanism involving metal hydride formation is proposed to explain the limited reversible hydrogen storage in magnesium borohydride.

  19. Cobalt-catalysed site-selective intra- and intermolecular dehydrogenative amination of unactivated sp3 carbons

    PubMed Central

    Wu, Xuesong; Yang, Ke; Zhao, Yan; Sun, Hao; Li, Guigen; Ge, Haibo

    2015-01-01

    Cobalt-catalysed sp2 C–H bond functionalization has attracted considerable attention in recent years because of the low cost of cobalt complexes and interesting modes of action in the process. In comparison, much less efforts have been devoted to the sp3 carbons. Here we report the cobalt-catalysed site-selective dehydrogenative cyclization of aliphatic amides via a C–H bond functionalization process on unactivated sp3 carbons with the assistance of a bidentate directing group. This method provides a straightforward synthesis of monocyclic and spiro β- or γ-lactams with good to excellent stereoselectivity and functional group tolerance. In addition, a new procedure has been developed to selectively remove the directing group, which enables the synthesis of free β- or γ-lactam compounds. Furthermore, the first cobalt-catalysed intermolecular dehydrogenative amination of unactivated sp3 carbons is also realized. PMID:25753366

  20. A dehydrogenation mechanism of metal hydrides based on interactions between Hdelta+ and H-.

    PubMed

    Lu, Jun; Fang, Zhigang Zak; Sohn, Hong Yong

    2006-10-16

    This paper describes a reaction mechanism that explains the dehydrogenation reactions of alkali and alkaline-earth metal hydrides. These light metal hydrides, e.g., lithium-based compounds such as LiH, LiAlH4, and LiNH2, are the focus of intense research recently as the most promising candidate materials for on-board hydrogen storage applications. Although several interesting and promising reactions and materials have been reported, most of these reported reactions and materials have been discovered by empirical means because of a general lack of understanding of any underlying principles. This paper describes an understanding of the dehydrogenation reactions on the basis of the interaction between negatively charged hydrogen (H-, electron donor) and positively charged hydrogen (Hdelta+, electron acceptor) and experimental evidence that captures and explains many observations that have been reported to date. This reaction mechanism can be used as a guidance for screening new material systems for hydrogen storage. PMID:17029387

  1. Effects of catalyst surface and hydrogen bond on ethanol dehydrogenation to ethoxy on Cu catalysts

    NASA Astrophysics Data System (ADS)

    Sun, Kang; Zhang, Minhua; Wang, Lichang

    2013-10-01

    Ethanol and ethanol dimer dehydrogenation to ethoxy on Cu surfaces were studied using DFT calculations with the PBE/DNP method. The dehydrogenation barrier decreases from 1.15 eV on Cu(1 1 1) to 0.72 eV on Cu(1 1 0) and further to 0.67 eV on Cu(1 0 0). The presence of hydrogen bond decreases the barrier to 1.02 eV on Cu(1 1 1) and 0.67 eV on Cu(1 1 0), but increases the barrier to 0.75 eV on Cu(1 0 0). Thus, the most effective catalyst surface is the clean Cu(1 0 0) and the ethanol adsorbed Cu(1 1 0). These results were analyzed based on the d-band center theory and the structural information of the adsorbed molecules.

  2. Imaging sequential dehydrogenation of methanol on Cu(110) with a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Kitaguchi, Y.; Shiotari, A.; Okuyama, H.; Hatta, S.; Aruga, T.

    2011-05-01

    Adsorption of methanol and its dehydrogenation on Cu(110) were studied by using a scanning tunneling microscope (STM). Upon adsorption at 12 K, methanol preferentially forms clusters on the surface. The STM could induce dehydrogenation of methanol sequentially to methoxy and formaldehyde. This enabled us to study the binding structures of these products in a single-molecule limit. Methoxy was imaged as a pair of protrusion and depression along the [001] direction. This feature is fully consistent with the previous result that it adsorbs on the short-bridge site with the C-O axis tilted along the [001] direction. The axis was induced to flip back and forth by vibrational excitations with the STM. Two configurations were observed for formaldehyde, whose structures were proposed based on their characteristic images and motions.

  3. Dehydrogenation of N2HX (X=2-4) by nitrogen atoms: thermochemical and kinetics.

    PubMed

    Spada, Rene Felipe Keidel; Ferrão, Luiz Fernando de Araujo; Roberto-Neto, Orlando; Machado, Francisco Bolivar Correto

    2013-11-21

    Thermochemical and kinetics of sequential hydrogen abstraction reactions from hydrazine by nitrogen atoms were studied. The dehydrogenation was divided in three steps, N2H4 + N, N2H3 + N, and N2H2 + N. The thermal rate constants were calculated within the framework of canonical variational theory, with zero and small curvature multidimensional tunnelling corrections. The reaction paths were computed with the BB1K/aug-cc-pVTZ method and the thermochemical properties were improved with the CCSD(T)/CBS//BB1K/aug-cc-pVTZ approach. The first dehydrogenation step presents the lowest rate constants, equal to 1.22 × 10(-20) cm(3) molecule(-1) s(-1) at 298 K. PMID:24320320

  4. Incorporation of catalytic dehydrogenation into fischer-tropsch synthesis to significantly reduce carbon dioxide emissions

    DOEpatents

    Huffman, Gerald P.

    2012-11-13

    A new method of producing liquid transportation fuels from coal and other hydrocarbons that significantly reduces carbon dioxide emissions by combining Fischer-Tropsch synthesis with catalytic dehydrogenation is claimed. Catalytic dehydrogenation (CDH) of the gaseous products (C1-C4) of Fischer-Tropsch synthesis (FTS) can produce large quantities of hydrogen while converting the carbon to multi-walled carbon nanotubes (MWCNT). Incorporation of CDH into a FTS-CDH plant converting coal to liquid fuels can eliminate all or most of the CO.sub.2 emissions from the water-gas shift (WGS) reaction that is currently used to elevate the H.sub.2 level of coal-derived syngas for FTS. Additionally, the FTS-CDH process saves large amounts of water used by the WGS reaction and produces a valuable by-product, MWCNT.

  5. Direct synthesis of dicarbonyl PCP-iron hydride complexes and catalytic dehydrogenative borylation of styrene.

    PubMed

    Jiang, Shi; Quintero-Duque, Samuel; Roisnel, Thierry; Dorcet, Vincent; Grellier, Mary; Sabo-Etienne, Sylviane; Darcel, Christophe; Sortais, Jean-Baptiste

    2016-07-01

    A new and efficient method based on the simple metalating reagent Fe(CO)5 has been developed for the straightforward synthesis of well defined cyclometalled PCP iron carbonyl pincer complexes. The reaction proceeds cleanly under mild conditions at 30 °C and UV irradiation. Four hydride pincer complexes are synthesized and fully characterized as well as an intermediate dinuclear species. The new iron complexes are active and selective catalytic precursors for the dehydrogenative borylation of styrene with HBpin. PMID:27327604

  6. Cu(I)-catalyzed sequential diamination and dehydrogenation of terminal olefins: a facile approach to imidazolinones.

    PubMed

    Zhu, Yingguang; Shi, Yian

    2014-10-20

    Diamination of olefins presents a powerful strategy to access vicinal diamines. During the last decade, metal-catalyzed diamination of olefins has received considerable attention. This study describes an efficient sequential diamination and dehydrogenation process of terminal olefins with CuBr as catalyst and di-tert-butyldiaziridinone as nitrogen source, providing a facile and viable approach to a variety of imidazolin-2-ones, which are important structural motifs present in various biologically active molecules. PMID:25213994

  7. Iridium complexes of new NCP pincer ligands: catalytic alkane dehydrogenation and alkene isomerization.

    PubMed

    Jia, Xiangqing; Zhang, Lei; Qin, Chuan; Leng, Xuebing; Huang, Zheng

    2014-09-28

    Iridium complexes of novel NCP pincer ligands containing pyridine and phosphinite arms have been synthesized. One Ir complex shows good catalytic activity for alkane dehydrogenation, and all complexes are highly active for olefin isomerization. A combination of the Ir complex and a (PNN)Fe pincer complex catalyzes the formation of linear alkylboronates selectively from internal olefins via sequential olefin isomerization-hydroboration. PMID:25101950

  8. Excellent catalytic effects of highly crumpled graphene nanosheets on hydrogenation/dehydrogenation of magnesium hydride.

    PubMed

    Liu, Guang; Wang, Yijing; Xu, Changchang; Qiu, Fangyuan; An, Cuihua; Li, Li; Jiao, Lifang; Yuan, Huatang

    2013-02-01

    Highly crumpled graphene nanosheets (GNS) with a BET surface area as high as 1159 m(2) g(-1) was fabricated by a thermal exfoliation method. A systematic investigation was performed on the hydrogen sorption properties of MgH(2)-5 wt% GNS nanocomposites acquired by ball-milling. It was found that the as-synthesized GNS exhibited a superior catalytic effect on hydrogenation/dehydrogenation of MgH(2). Differential Scanning Calorimetry (DSC) and isothermal hydrogenation/dehydrogenation measurements indicated that both hydrogen sorption capacity and dehydrogenation/hydrogenation kinetics of the composites improved with increasing milling time. The composites MgH(2)-GNS milled for 20 h can absorb 6.6 wt% H(2) within 1 min at 300 °C and 6.3 wt% within 40 min at 200 °C, even at 150 °C, it can also absorb 6.0 wt% H(2) within 180 min. It was also demonstrated that MgH(2)-GNS-20 h could release 6.1 wt% H(2) at 300 °C within 40 min. In addition, microstructure measurements based on XRD, SEM, TEM as well as Raman spectra revealed that the grain size of thus-prepared MgH(2)-GNS nanocomposites decreased with increasing milling time, moreover, the graphene layers were broken into smaller graphene nanosheets in a disordered and irregular manner during milling. It was confirmed that these smaller graphene nanosheets on the composite surface, providing more edge sites and hydrogen diffusion channels, prevented the nanograins from sintering and agglomerating, thus, leading to promotion of the hydrogenation/dehydrogenation kinetics of MgH(2). PMID:23254449

  9. Dehydrogenative polymerization of silanes to polysilanes by zirconocene and hafnocene catalysts. A new polymerization mechanism

    SciTech Connect

    Woo, Heegweon; Tilley, T.D. )

    1989-11-27

    Polysilanes, (-SiRR{prime}-){sub n} represent a class of inorganic polymers that have unusual chemical properties and a number of potential applications. Prospects for development of a coordination polymerization route to these polymers have improved dramatically with the recent discovery by Harrod and co-workers that titanocene and zirconocene alkyl derivatives are active catalysts for the dehydrogenative coupling of primary silanes RSiH{sub 3} to linear polysilanes with ca. 10-20 Si atoms (eq 1, Cp = {eta}{sup 5}-C{sub 5}H{sub 5}, M = Ti, Zr){sup 2}. We have found that a number of zirconium and hafnium silyl complexes of the type Cp{prime}{sub 2}M(SiR{sub 3})R{prime} (Cp{prime} = Cp, Cp* ({eta}{sup 5}-C{sub 5}Me{sub 5}); M = Zr, Hf; R = Me, Ph, SiMe{sub 3}; R{prime} = Cl, alkyl, silyl) are catalyst precursors for this dehydrogenative coupling reaction and that polymer molecular weights can vary as a function of reaction conditions and catalyst. This report describes observations that suggest a mechanism for dehydrogenative silane polymerization by zirconocene and hafnocene catalysts.

  10. Dehydrogenation of anhydrous methanol at room temperature by o-aminophenol-based photocatalysts

    PubMed Central

    Wakizaka, Masanori; Matsumoto, Takeshi; Tanaka, Ryota; Chang, Ho-Chol

    2016-01-01

    Dehydrogenation of anhydrous methanol is of great importance, given its ubiquity as an intermediate for the production of a large number of industrial chemicals. Since dehydrogenation of methanol is an endothermic reaction, heterogeneous or homogeneous precious-metal-based catalysts and high temperatures are usually required for this reaction to proceed. Here we report the photochemical dehydrogenation of anhydrous methanol at room temperature catalysed by o-aminophenol (apH2), o-aminophenolate (apH−) and the non-precious metal complex trans-[FeII(apH)2(MeOH)2]. Under excitation at 289±10 nm and in the absence of additional photosensitizers, these photocatalysts generate hydrogen and formaldehyde from anhydrous methanol with external quantum yields of 2.9±0.15%, 3.7±0.19% and 4.8±0.24%, respectively, which are the highest values reported so far to the best of our knowledge. Mechanistic investigations reveal that the photo-induced formation of hydrogen radicals triggers the reaction. PMID:27457731

  11. An in situ photoemission study of the dehydrogenation reaction of methanol on Ni( 1 0 0 )

    NASA Astrophysics Data System (ADS)

    Neubauer, R.; Whelan, C. M.; Denecke, R.; Steinrück, H.-P.

    2002-06-01

    Making use of the high intensity and resolution of synchrotron radiation at MAX-II (Sweden) we studied the dehydrogenation reaction of methanol on Ni(1 0 0) as a function of temperature by core level photoelectron spectroscopy. The temperature was increased linearly from 105 to 425 K with a heating rate of 0.06 K s -1. Measurement times of 60 s per C 1s spectrum allowed the dehydrogenation reaction to be monitored in situ. The different binding energies of the core level characteristic of different adsorbed species are reported. After exposure at 105 K, the C 1s spectra exhibit two peaks, representing methanol in multilayer and monolayer states. Above 160 K the multilayer is completely desorbed and methanol from the monolayer starts to dehydrogenate to form a methoxy species which decomposes above 240 K to carbon monoxide adsorbed in the bridge site. The onset of the on-top site occupation is observed at 270 K. The data suggests conversion from bridge to on-top site CO around 290 K. Our results show good agreement with literature values from temperature programmed desorption and Fourier transform infra-red experiments and provide new information in the form of quantitative data on the decomposition pathway of methanol adsorbed on Ni(1 0 0).

  12. Dehydrogenation of ammonia borane catalyzed by pristine and defective h-BN sheets

    NASA Astrophysics Data System (ADS)

    Kuang, Anlong; Zhou, Tingwei; Wang, Guangzhao; Li, Yang; Wu, Gang; Yuan, Hongkuan; Chen, Hong; Yang, Xiaolan

    2016-01-01

    The dehydrogenation of pristine and defective h-BN sheets-supported ammonia borane (AB) systems is investigated by the first-principles method. The results show that nitrogen or boron atoms at the edges of vacancies are used as hydrogen acceptors which plays a crucial role in the process of dehydrogenation between the defective h-BN sheets and AB. The energy barriers to the transfer of hydrogen from AB to the defective h-BN sheets are low and the processes are significantly exothermic, indicating that these reactions are thermodynamically favorable. The hydrogenated defective h-BN sheets (protonic and hydridic hydrogens transfer from AB to the defective h-BN sheets) further react with AB to release H2 with low reaction barriers. Our theoretical study demonstrates that the defective h-BN sheets can be the effective metal-free catalysts. Furthermore, the potential advantage of such dehydrogenation process is the fact that no other elements are being introduced into the system.

  13. Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane.

    PubMed

    Lee, Jong Kwon; Seo, Hyun; Hong, Ung Gi; Park, Gle; Yoo, Yeonshick; Lee, Jinsuk; Chang, Hosik; Song, In Kyu

    2015-10-01

    Al2O3 supports were prepared by a precipitation method using various basic solutions (NaOH, KOH, NH4OH, and Na2CO3) as precipitation agents, and Pt/Sn/Al2O3 nano-catalysts were then prepared by a sequential impregnation method. The prepared catalysts were applied to the direct dehydrogenation of n-butane to n-butenes and 1,3-butadiene. The effect of precipitation agents on the physicochemical properties and catalytic activities of Pt/Sn/Al2O3 nano-catalysts in the direct dehydrogenation of n-butane was investigated. Catalytic performance of Pt/Sn/Al2O3 nano-catalysts decreased in order of Pt/Sn/Al2O3 (NaOH) > Pt/Sn/Al2O3 (KOH) > Pt/Sn/Al2O3 (NH4OH) > Pt/Sn/Al2O3 (Na2CO3). Among the catalysts tested, Pt/Sn/Al2O3 (NaOH) nano-catalyst showed the best catalytic performance in terms of yield for total dehydrogenation products (TDP, n-butenes and 1,3-butadiene). Hydrogen chemisorption experiments revealed that platinum surface area of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing platinum surface area of the catalyst. PMID:26726508

  14. Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals.

    PubMed

    Kislitsyn, Dmitry A; Mills, Jon M; Kocevski, Vancho; Chiu, Sheng-Kuei; DeBenedetti, William J I; Gervasi, Christian F; Taber, Benjamen N; Rosenfield, Ariel E; Eriksson, Olle; Rusz, Ján; Goforth, Andrea M; Nazin, George V

    2016-06-28

    We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces. PMID:27369490

  15. Dehydrogenation of anhydrous methanol at room temperature by o-aminophenol-based photocatalysts.

    PubMed

    Wakizaka, Masanori; Matsumoto, Takeshi; Tanaka, Ryota; Chang, Ho-Chol

    2016-01-01

    Dehydrogenation of anhydrous methanol is of great importance, given its ubiquity as an intermediate for the production of a large number of industrial chemicals. Since dehydrogenation of methanol is an endothermic reaction, heterogeneous or homogeneous precious-metal-based catalysts and high temperatures are usually required for this reaction to proceed. Here we report the photochemical dehydrogenation of anhydrous methanol at room temperature catalysed by o-aminophenol (apH2), o-aminophenolate (apH(-)) and the non-precious metal complex trans-[Fe(II)(apH)2(MeOH)2]. Under excitation at 289±10 nm and in the absence of additional photosensitizers, these photocatalysts generate hydrogen and formaldehyde from anhydrous methanol with external quantum yields of 2.9±0.15%, 3.7±0.19% and 4.8±0.24%, respectively, which are the highest values reported so far to the best of our knowledge. Mechanistic investigations reveal that the photo-induced formation of hydrogen radicals triggers the reaction. PMID:27457731

  16. Dehydrogenation of 3-phenoxybenzyl alcohol in isolated perfused rabbit skin, skin homogenate and purified dehydrogenases.

    PubMed

    Bast, G E; Kampffmeyer, H G

    1998-01-01

    The formation of 3-phenoxybenzoic acid from 3-phenoxybenzyl alcohol was determined in (a) rabbit ears, single-pass perfused with a protein-free buffer, pH 7.4; (b) the microsomal fraction and its supernatant from homogenized rabbit skin; and (c) purified alcohol dehydrogenase from horse liver and baker's yeast. The inhibition of product formation in (a) was about 60% by various 4-methylpyrazole concentrations, but metyrapone had no effect. Following ultracentrifugation, only the supernatant of homogenized skin showed product formation (apparent Vmay: 32 pmol/min per cm2 skin; apparent Km: 64 microM). 3-Phenoxybenzyl alcohol and ethanol dehydrogenation was similar by alcohol dehydrogenase from horse liver (apparent Km: 0.7 vs. 0.4 mM; apparent Vmax: 0.3 vs. 0.2 U/ microg protein). In baker's yeast, the apparent Km of 3-phenoxybenzoic acid formation was several times larger than that for ethanol dehydrogenation. The KI of 4-methylpyrazole for alcohol dehydrogenase from horse liver was 0.6 (3-phenoxybenzyl alcohol) vs. 0.04 microM (ethanol). The KI for ethanol in baker's yeast was 470 microM. In conclusion dehydrogenation is an important metabolic pathway in the skin for xenobiotics with an aliphatic alcohol at a side chain. PMID:9885409

  17. Nanoporous PtRu Alloys with Unique Catalytic Activity toward Hydrolytic Dehydrogenation of Ammonia Borane.

    PubMed

    Zhou, Qiuxia; Xu, Caixia

    2016-03-01

    Nanoporous (NP) PtRu alloys with three different bimetallic components were straightforwardly fabricated by dealloying PtRuAl ternary alloys in hydrochloric acid. Selective etching of aluminum from source alloys generates bicontinuous network nanostructures with uniform size and structure. The as-made NP-PtRu alloys exhibit superior catalytic activity toward the hydrolytic dehydrogenation of ammonia borane (AB) than pure NP-Pt and NP-Ru owing to alloying platinum with ruthenium. The NP-Pt70 Ru30 alloy exhibits much higher specific activity toward hydrolytic dehydrogenation of AB than NP-Pt30 Ru70 and NP-Pt50 Ru50 . The hydrolysis activation energy of NP-Pt70 Ru30 was estimated to be about 38.9 kJ mol(-1) , which was lower than most of the reported activation energy values in the literature. In addition, recycling tests show that the NP-Pt70 Ru30 is still highly active in the hydrolysis of AB even after five runs, which indicates that NP-PtRu alloy accompanied by the network nanoarchitecture is beneficial to improve structural stability toward the dehydrogenation of AB. PMID:26573746

  18. Dehydration and Dehydrogenation of Ethylene Glycol on Rutile TiO2(110)

    SciTech Connect

    Li, Zhenjun; Kay, Bruce D.; Dohnalek, Zdenek

    2013-08-07

    The interactions of ethylene glycol (EG) with partially reduced rutile TiO2(110) surface have been studied using temperature programmed desorption (TPD). The saturation coverage on the surface Ti rows is determined to be 0.43 monolayer (ML), slightly less than one EG per two Ti sites. Most of the adsorbed ethanol (~80%) undergoes further reactions to other products. Two major channels are observed, dehydration yielding ethylene and water and dehydrogenation yielding acetaldehyde and hydrogen. Hydrogen formation is rather surprising as it has not been observed previously on TiO2(110) from simple organic molecules. The coverage dependent yields of ethylene and acetaldehyde correlate well with that of water and hydrogen, respectively. Dehydration dominates at lower EG coverages (< 0.2 ML) and plateaus as the coverage is increased to saturation. Dehydrogenation is observed primarily at higher EG coverages (>0.2 ML). Our results suggest that the observed dehydration and dehydrogenation reactions proceed via different surface intermediates.

  19. First-principles Study of Methane Dehydrogenation on a Bimetallic Cu/Ni(111) Surface

    SciTech Connect

    An, Wei; Zeng, Xiao Cheng; Turner, C. H.

    2009-11-02

    We present density-functional theory calculations of the dehydrogenation of methane and CHx (x =1–3) on a Cu/Ni(111) surface, where Cu atoms are substituted on the Ni surface at a coverage of 1/4 monolayer. As compared to the results on other metal surfaces, including Ni(111), a similar activation mechanism with different energetics is found for the successive dehydrogenation of CH4 on the Cu/Ni(111) surface. In particular, the activation energy barrier (Eact) for CH→C+H is found to be 1.8 times larger than that on Ni(111), while Eact for CH4→CH3+H is 1.3 times larger. Considering the proven beneficial effect of Cu observed in the experimental systems, our findings reveal that the relative Eact in the successive dehydrogenation of CH4 plays a key role in impeding carbon formation during the industrial steam reforming of methane. Our calculations also indicate that previous scaling relationships of the adsorption energy (Eads) for CHx (x=1–3) and carbon on pure metals also hold for several Ni(111)-based alloy systems.

  20. First-principles study of methane dehydrogenation on a bimetallic Cu/Ni(111) surface

    NASA Astrophysics Data System (ADS)

    An, Wei; Zeng, X. C.; Turner, C. Heath

    2009-11-01

    We present density-functional theory calculations of the dehydrogenation of methane and CHx (x=1-3) on a Cu/Ni(111) surface, where Cu atoms are substituted on the Ni surface at a coverage of 1/4 monolayer. As compared to the results on other metal surfaces, including Ni(111), a similar activation mechanism with different energetics is found for the successive dehydrogenation of CH4 on the Cu/Ni(111) surface. In particular, the activation energy barrier (Eact) for CH→C+H is found to be 1.8 times larger than that on Ni(111), while Eact for CH4→CH3+H is 1.3 times larger. Considering the proven beneficial effect of Cu observed in the experimental systems, our findings reveal that the relative Eact in the successive dehydrogenation of CH4 plays a key role in impeding carbon formation during the industrial steam reforming of methane. Our calculations also indicate that previous scaling relationships of the adsorption energy (Eads) for CHx (x=1-3) and carbon on pure metals also hold for several Ni(111)-based alloy systems.

  1. A theoretical study on the complete dehydrogenation of methanol on Pd (100) surface

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Wang, Bin; Fang, Tao

    2016-02-01

    Density functional theory (DFT) method was employed to investigate the adsorption and decomposition mechanisms of CH3OH on Pd (100) surface. Different kinds of possible adsorption modes of relevant intermediates on the surface were identified. It was found that CH3OH and CH2OH prefers to adsorb on the top site, CH3O, CHOH and CO occupy preferentially on the bridge site, while CH2O, CHO, COH and H species adsorb on the hollow site. The adsorption energies of all species exhibit the following trend: CH3OH < CH2O < CH3O < CO < CH2OH < H < CHO < CHOH < COH. Subsequently, four possible dissociation pathways of CH3OH via initial Osbnd H and Csbnd H bond scissions were proposed and studied systematically. The transition states, energy barriers and reaction energies were calculated to explore the dehydrogenation mechanisms of CH3OH on Pd (100) surface. It was indicated that the scission of Csbnd H bond is more favorable for CH3OH and CH2OH and the Hsbnd O bond cleavage is easier for CHOH. The path 2 (CH3OHsbnd CH2OHsbnd CHOHsbnd CHOsbnd CO) is the most possible dehydrogenation pathway, where the highest energy barrier of CH3OH dissociation makes it to be the rate-determining step of the whole dehydrogenation reaction.

  2. Assessment of the risk of transporting propane by truck and train

    SciTech Connect

    Geffen, C.A.

    1980-03-01

    The risk of shipping propane is discussed and the risk assessment methodology is summarized. The risk assessment model has been constructed as a series of separate analysis steps to allow the risk to be readily reevaluated as additional data becomes available or as postulated system characteristics change. The transportation system and accident environment, the responses of the shipping system to forces in transportation accidents, and release sequences are evaluated to determine both the likelihood and possible consequences of a release. Supportive data and analyses are given in the appendices. The risk assessment results are related to the year 1985 to allow a comparison with other reports in this series. Based on the information presented, accidents involving tank truck shipments of propane will be expected to occur at a rate of 320 every year; accidents involving bobtails would be expected at a rate of 250 every year. Train accidents involving propane shipments would be expected to occur at a rate of about 60 every year. A release of any amount of material from propane trucks, under both normal transportation and transport accident conditions, is to be expected at a rate of about 110 per year. Releases from propane rail tank cars would occur about 40 times a year. However, only those releases that occur during a transportation accident or involve a major tank defect will include sufficient propane to present the potential for danger to the public. These significant releases can be expected at the lower rate of about fourteen events per year for truck transport and about one event every two years for rail tank car transport. The estimated number of public fatalities resulting from these significant releases in 1985 is fifteen. About eleven fatalities per year result from tank truck operation, and approximately half a death per year stems from the movement of propane in rail tank cars.

  3. Synthesis and the thermal and catalytic dehydrogenation reactions of amine-thioboranes.

    PubMed

    Robertson, Alasdair P M; Haddow, Mairi F; Manners, Ian

    2012-08-01

    A series of trimethylamine-thioborane adducts, Me(3)N·BH(2)SR (R = tBu [2a], nBu [2b], iPr [2c], Ph [2d], C(6)F(5) [2e]) have been prepared and characterized. Attempts to access secondary and primary amine adducts of thioboranes via amine-exchange reactions involving these species proved unsuccessful, with the thiolate moiety shown to be vulnerable to displacement by free amine. However, treatment of the arylthioboranes, [BH(2)-SPh](3) (9) and C(6)F(5)SBH(2)·SMe(2) (10) with Me(2)NH and iPr(2)NH successfully yielded the adducts Me(2)NH·BH(2)SR (R = Ph [11a], C(6)F(5) [12a]) and iPr(2)NH·BH(2)SR (R = Ph [11b], C(6)F(5) [12b]) in high yield. These adducts were also shown to be accessible via thermally induced hydrothiolation of the aminoboranes Me(2)N═BH(2), derived from the cyclic dimer [Me(2)N-BH(2)](2) (13), and iPr(2)N═BH(2) (14), respectively. Attempts to prepare the aliphatic thiolate substituted adducts R(2)NH·BH(2)SR' (R = Me, iPr; R' = tBu, nBu, iPr) via this method, however, proved unsuccessful, with the temperatures required to facilitate hydrothiolation also inducing thermal dehydrogenation of the amine-thioborane products to form aminothioboranes, R(2)N═BH(SR'). Thermal and catalytic dehydrogenation of the targeted amine-thioboranes, 11a/11b and 12a/12b were also investigated. Adducts 11b and 12b were cleanly dehydrogenated to yield iPr(2)N═BH(SPh) (22) and iPr(2)N═BH(SC(6)F(5)) (23), respectively, at 100 °C (18 h, toluene), with dehydrogenation also possible at 20 °C (42 h, toluene) with a 2 mol % loading of [Rh(μ-Cl)cod](2) in the case of the former species. Similar studies with adduct 11a evidenced a competitive elimination of H(2) and HSPh upon thermolysis, and other complex reactivity under catalytic conditions, whereas the fluorinated analogue 12a was found to be resistant to dehydrogenation. PMID:22800118

  4. Understanding complete oxidation of methane on spinel oxides at a molecular level

    DOE PAGESBeta

    Tao, Franklin Feng; Shan, Jun-jun; Nguyen, Luan; Wang, Ziyun; Zhang, Shiran; Zhang, Li; Wu, Zili; Huang, Weixin; Zeng, Shibi; Hu, P.

    2015-08-04

    It is crucial to develop a catalyst made of earth-abundant elements highly active for a complete oxidation of methane at a relatively low temperature. NiCo2O4 consisting of earth-abundant elements which can completely oxidize methane in the temperature range of 350-550 °C. Being a cost-effective catalyst, NiCo2O4 exhibits activity higher than precious-metal-based catalysts. Here we report that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale. Finally, in situ studies of complete oxidation of methane on NiCo2O4 and theoretical simulations show thatmore » methane dissociates to methyl on nickel cations and then couple with surface lattice oxygen atoms to form -CH3O with a following dehydrogenation to -CH2O; a following oxidative dehydrogenation forms CHO; CHO is transformed to product molecules through two different sub-pathways including dehydrogenation of OCHO and CO oxidation.« less

  5. Understanding complete oxidation of methane on spinel oxides at a molecular level

    SciTech Connect

    Tao, Franklin Feng; Shan, Jun-jun; Nguyen, Luan; Wang, Ziyun; Zhang, Shiran; Zhang, Li; Wu, Zili; Huang, Weixin; Zeng, Shibi; Hu, P.

    2015-08-04

    It is crucial to develop a catalyst made of earth-abundant elements highly active for a complete oxidation of methane at a relatively low temperature. NiCo2O4 consisting of earth-abundant elements which can completely oxidize methane in the temperature range of 350-550 °C. Being a cost-effective catalyst, NiCo2O4 exhibits activity higher than precious-metal-based catalysts. Here we report that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale. Finally, in situ studies of complete oxidation of methane on NiCo2O4 and theoretical simulations show that methane dissociates to methyl on nickel cations and then couple with surface lattice oxygen atoms to form -CH3O with a following dehydrogenation to -CH2O; a following oxidative dehydrogenation forms CHO; CHO is transformed to product molecules through two different sub-pathways including dehydrogenation of OCHO and CO oxidation.

  6. Heteroepitaxially grown zeolitic imidazolate framework membranes with unprecedented propylene/propane separation performances.

    PubMed

    Kwon, Hyuk Taek; Jeong, Hae-Kwon; Lee, Albert S; An, He Seong; Lee, Jong Suk

    2015-09-30

    Propylene/propane separation is one of the most challenging separations, currently achieved by energy-intensive cryogenic distillation. Despite the great potential for energy-efficient membrane-based separations, no commercial membranes are currently available due to the limitations of current polymeric materials. Zeolitic imidazolate framework, ZIF-8, with the effective aperture size of ∼4.0 Å, has been shown to be very promising for propylene/propane separation. Despite the extensive research on ZIF-8 membranes, only a few reported ZIF-8 membranes have displayed good propylene/propane separation performances presumably due to the challenges of controlling the microstructures of polycrystalline membranes. Here we report the first well-intergrown membranes of ZIF-67 (Co-substituted ZIF-8) by heteroepitaxially growing ZIF-67 on ZIF-8 seed layers. The ZIF-67 membranes exhibited impressively high propylene/propane separation capabilities. Furthermore, when a tertiary growth of ZIF-8 layers was applied to heteroepitaxially grown ZIF-67 membranes, the membranes exhibited unprecedentedly high propylene/propane separation factors of ∼200 possibly due to enhanced grain boundary structure. PMID:26364888

  7. No. 2 heating oil/propane program 1994--1995. Final report

    SciTech Connect

    McBrien, J.

    1995-05-01

    During the 1994--95 heating season, the Massachusetts Division of Energy Resources (DOER) participated in a joint data collection program between several state energy offices and the federal Department of Energy`s (DOE) Energy Information Administration (EIA). The purpose of the program was to collect and monitor retail and wholesale heating oil and propane prices and inventories from October 1994 through March 1995. This program augmented the existing Massachusetts data collection system and served several important functions. The information helped the federal and state governments respond to consumer, congressional and media inquiries regarding No. 2 oil and propane. The information also provided policy decision-makers with timely, accurate and consistent data to monitor current heating oil and propane markets and develop appropriate state responses when necessary. In addition, the communication network between states and the DOE was strengthened through this program. This final report begins with an overview of the unique events that had an impact on the petroleum markets prior to and during the reporting period. Next, the report summarizes the results from residential heating oil and propane price surveys conducted by DOER over the 1994--95 heating season. The report also incorporates the wholesale heating oil and propane prices and inventories collected by EIA and distributed to the states. Finally, the report outlines DOER`s use of the data.

  8. State Heating Oil & Propane Program. Final report 1997/98 heating season

    SciTech Connect

    Hunton, G.

    1998-06-01

    The following is a summary report of the New Hampshire Governor`s Office of Energy and Community Services (ECS) participation in the State Heating Oil and Propane Program (SHOPP) for the 1997/98 heating season. SHOPP is a cooperative effort, linking energy offices in East Coast and Midwest states, with the Department of Energy (DOE), Energy Information Administration (EIA) for the purpose of collecting retail price data for heating oil and propane. The program is funded by the participating state with a matching grant from DOE. SHOPP was initiated in response to congressional inquires into supply difficulties and price spikes of heating oil and propane associated with the winter of 1989/90. This is important to New Hampshire because heating oil controls over 55% of the residential heating market statewide. Propane controls 10% of the heating market statewide and is widely used for water heating and cooking in areas of the state where natural gas is not available. Lower installation cost, convenience, lower operating costs compared to electricity, and its perception as a clean heating fuel have all worked to increase the popularity of propane in New Hampshire and should continue to do so in the future. Any disruption in supply of these heating fuels to New Hampshire could cause prices to skyrocket and leave many residents in the cold.

  9. Transition Metal-Catalyzed Aerobic Dehydrogenation of Heterocycles and Development, Implementation, and Evaluation of a Student-Generated ChemWiki and its Impact on Student Performance

    NASA Astrophysics Data System (ADS)

    Brown, Jaclyn R.

    Section I describes progress towards the dehydrogenation of heterocycles, specifically tetrahydroquinolines and imidazolines. Chapter 1 details the development of an aerobic Pd catalyst system capable of aromatizing substituted tetrahydroquinolines in moderate to good yields. This catalyst system generally works well for substituted tetrahydroquinolines, although elimination of heteroatom substituents remains problematic. Chapter 2 describes the development of a copper-based catalyst system for the dehydrogenation of substituted imidazolines to imidazoles. This catalyst system is based upon the CuI/bpy/TEMPO/NMI system developed by the Stahl group, which has shown excellent reactivity towards alcohol oxidation. Efforts to adapt this system to imidazolines are described herein. Section II details the development, implementation, and evaluation of a student-generated chemistry wiki in large general chemistry courses. Chapter 3 describes a theoretical framework based in constructivist epistemology for the use of wikis in chemical education and presents previous examples and limitations of wiki usage in chemistry and non-chemistry environments. Chapter 4 details the process of designing the ChemWiki experiment and the ChemWiki website itself. A detailed description of the assessments used to evaluate student performance is also presented. Chapter 5 describes two surveys designed to assess the qualitative aspects of the second generation wiki design. Additionally, an overview of participants' perception of the chemistry wiki and its utility as well as data tracking logs of participants' interactions with the ChemWiki are presented. Chapter 6 presents a quantitative analysis of the efficacy of the chemistry wiki on student posttest scores. Chapter 7 summarizes the findings of this thesis and includes recommended future directions for the use of ChemWikis in chemical education environments.

  10. New pathways of betanidin and betanin enzymatic oxidation.

    PubMed

    Wybraniec, Sławomir; Michałowski, Tadeusz

    2011-09-14

    Betanidin is a basic betacyanin with a 5,6-dihydroxyl moiety which causes its high antioxidant activity. For the purpose of structural study, the enzymatic oxidation of betanidin and betanin (5-O-glucosylated betanidin), followed by chromatographic separation of the oxidation products with spectrophotometric and mass spectrometric detection (LC-DAD-MS/MS) was performed. Within the pH 4-8 range, two main oxidation peaks of betanidin were observed, betanidin quinonoid (possibly betanidin o-quinone) and 2-decarboxy-2,3-dehydrobetanidin, whereas at pH 3 only dehydrogenated and decarboxylated derivatives were detected, suggesting different stabilities of the products at different pH values. The presence of two prominent oxidation products, 2-decarboxy-2,3-dehydrobetanidin and 2,17-bidecarboxy-2,3-dehydrobetanidin, at pH 3 indicates their generation via two possible reaction routes with two different quinonoid intermediates: dopachrome derivative and quinone methide. Both reaction paths lead to the decarboxylative dehydrogenation of betanidin. Subsequent oxidation and rearrangement of the conjugated chromophoric system results in the formation of 14,15-dehydrogenated derivatives. Betanin is oxidized with generation of a quinone methide intermediate, which rearranges to 2,3-dehydro- or neoderivatives. The products of enzymatic oxidation of betacyanins thus formed are derivatives of 5,6-dihydroxyindole and related structures known as the key intermediates in melanogenesis. PMID:21806060

  11. Resonance Raman Spectroscopy of 0-A12O3- Supported Vanadium Oxide Catalysts for Butane Dehydrogenation

    SciTech Connect

    Wu, Zili; Kim, Hack-Sung; Stair, Peter

    2008-01-01

    This chapter contains sections titled: Introduction; Structure of Al{sub 2}O{sub 3}-Supported Vanadia Catalysts; Quantification of Surface VOx Species on Supported Vanadia Catalysts; Conclusion; Acknowledgements; and References.

  12. Palladium-catalyzed dehydrogenation/oxidative cross-coupling sequence of β-heteroatom-substituted ketones.

    PubMed

    Moon, Youngtaek; Kwon, Daeil; Hong, Sungwoo

    2012-11-01

    Concise and selective: the title one-pot sequence allows formation of the enone functionality and subsequent cross-coupling. The process provides access to highly functionalized cyclic enolones and enaminones from readily accessible β-heteroatom-substituted cyclic ketones. PMID:23038616

  13. Influence of Particle Size on Reaction Selectivity in Cyclohexene Hydrogenation and Dehydrogenation over Silica-Supported Monodisperse Pt Particles

    SciTech Connect

    Rioux, R. M.; Hsu, B. B.; Grass, M. E.; Song, H.; Somorjai, Gabor A.

    2008-07-11

    The role of particle size during the hydrogenation/dehydrogenation of cyclohexene (10 Torr C{sub 6}H{sub 10}, 200-600 Torr H{sub 2}, and 273-650 K) was studied over a series of monodisperse Pt/SBA-15 catalysts. The conversion of cyclohexene in the presence of excess H{sub 2} (H{sub 2}:C{sub 6}H{sub 10} ratio = 20-60) is characterized by three regimes: hydrogenation of cyclohexene to cyclohexane at low temperature (< 423 K), an intermediate temperature range in which both hydrogenation and dehydrogenation occur; and a high temperature regime in which the dehydrogenation of cyclohexene dominates (> 573 K). The rate of both reactions demonstrated maxima with temperature, regardless of Pt particle size. For the hydrogenation of cyclohexene, a non-Arrhenius temperature dependence (apparent negative activation energy) was observed. Hydrogenation is structure insensitive at low temperatures, and apparently structure sensitive in the non-Arrhenius regime; the origin of the particle-size dependent reactivity with temperature is attributed to a change in the coverage of reactive hydrogen. Small particles were more active for dehydrogenation and had lower apparent activation energies than large particles. The selectivity can be controlled by changing the particle size, which is attributed to the structure sensitivity of both reactions in the temperature regime where hydrogenation and dehydrogenation are catalyzed simultaneously.

  14. No. 2 heating oil/propane program. Final report, 1990/91

    SciTech Connect

    McBrien, J.

    1991-06-01

    During the 1990/91 heating season, the Massachusetts Division of Energy Resources (DOER) participated in a joint data collection program between several state energy offices and the federal Department of Energy`s (DOE) Energy Information Administration (EIA). The purpose of the program was to collect and monitor retail and wholesale heating oil and propane prices and inventories from October 1990 through March 1991. This final report begins with an overview of the unique events which had an impact on the reporting period. Next, the report summarizes the results from the residential heating oil and propane price surveys conducted by DOER over the 1990/91 heating season. The report also incorporates the wholesale heating oil and propane prices and inventories collected by the EIA and distributed to the states.

  15. No. 2 heating oil/propane program. Final report, 1992/93

    SciTech Connect

    McBrien, J.

    1993-05-01

    During the 1992--93 heating season, the Massachusetts Division Energy Resources (DOER) participated in a joint data collection program between several state energy offices and the federal Department of Energy`s (DOE) Energy Information Administration (EIA). The purpose of the program was to collect and monitor retail and wholesale heating oil and propane prices and inventories from October, 1992 through March, 1993. This final report begins with an overview of the unique events which had an impact on the petroleum markets prior to and during the reporting period. Next, the report summarizes the results from residential heating oil and propane price surveys conducted by DOER over the 1992--93 heating season. The report also incorporates the wholesale heating oil and propane prices and inventories collected by the EIA and distributed to the states. Finally, the report outlines DOER`s use of the data.

  16. Number 2 heating oil/propane program. Final report, 1991/92

    SciTech Connect

    McBrien, J.

    1992-06-01

    During the 1991--92 heating season, the Massachusetts Division of Energy Resources (DOER) participated in a joint data collection program between several state energy offices and the federal Department of Energy`s (DOE) Energy Information Administration (EIA). The purpose of the program was to collect and monitor retail and wholesale heating oil and propane prices and inventories from October, 1991 through March, 1992. This final report begins with an overview of the unique events which had an impact on the reporting period. Next, the report summarizes the results from the residential heating oil and propane price surveys conducted by DOER over the 1991--1992 heating season. The report also incorporates the wholesale heating oil and propane prices and inventories collected by the EIA and distributed to the states. Finally, the report outlines DOER`s use of the data and responses to the events which unfolded during the 1991--1992 heating season.

  17. Explosive-driven shock wave and vortex ring interaction with a propane flame

    NASA Astrophysics Data System (ADS)

    Giannuzzi, P. M.; Hargather, M. J.; Doig, G. C.

    2016-02-01

    Experiments were performed to analyze the interaction of an explosively driven shock wave and a propane flame. A 30 g explosive charge was detonated at one end of a 3-m-long, 0.6-m-diameter shock tube to produce a shock wave which propagated into the atmosphere. A propane flame source was positioned at various locations outside of the shock tube to investigate the effect of different strength shock waves. High-speed retroreflective shadowgraph imaging visualized the shock wave motion and flame response, while a synchronized color camera imaged the flame directly. The explosively driven shock tube was shown to produce a repeatable shock wave and vortex ring. Digital streak images show the shock wave and vortex ring propagation and expansion. The shadowgrams show that the shock wave extinguishes the propane flame by pushing it off of the fuel source. Even a weak shock wave was found to be capable of extinguishing the flame.

  18. Toxicological investigation of liquid petroleum gas explosion: human model for propane/ethyl mercaptan exposures.

    PubMed

    Lowry, W T; Gamse, B; Armstrong, A T; Corn, J M; Juarez, L; McDowell, J L; Owens, R

    1991-03-01

    Four individuals died as the result of a propane explosion. As with many propane explosions, the question was raised as to the adequacy of the product's odorization after the autopsy studies had been conducted. In most cases, this question leads to litigation. Ethyl mercaptan is a widely used odorant for propane and was used in this instance. Three of the four victims had blood available at autopsy for study. Quantitative analyses of the victims' blood, obtained during autopsy, were performed using gas chromatography/mass spectrometry, without subjecting the samples to hydrolysis. These analyses determined the relative amounts of propane and ethyl mercaptan in the blood to be 90, 63, and 175 mL/m3 headspace, and 0.36, 0.34, and 0.77 microgram/L blood, respectively. Since mercaptans have been reported in human blood as products of metabolism, modeling studies were conducted to establish the validity of the autopsy data and to develop an autopsy toxicology protocol for investigating explosion deaths. When subjects were not exposed to an atmosphere containing ethyl mercaptan, dimethylsulfide was the only mercaptan detectable in their blood without severe hydrolysis prior to analysis. Metabolic ethyl mercaptan is sufficiently bound to be undetectable by the methods used without hydrolysis. Human subjects were exposed to a flammable mixture of air and propane odorized with ethyl mercaptan. The analyses of the blood from these subjects produced results which were comparable with those for the explosion victims, establishing that the question of odorant adequacy can be addressed at the autopsy of propane explosion victims. It is extremely important that the pathologist and toxicologist investigating gas explosion deaths recognize the valuable evidence existing in the victim's blood. PMID:2066720

  19. Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

    PubMed

    Deng, Weiping; Chen, Jiashu; Kang, Jincan; Zhang, Qinghong; Wang, Ye

    2016-05-21

    Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs. PMID:27125360

  20. Foreign-gas pressure broadening parameters of propane near 748/cm

    NASA Technical Reports Server (NTRS)

    Nadler, Schachar; Jennings, D. E.

    1989-01-01

    The pressure-broadening coefficients of the nu sub 19 band of propane near 748/cm due to H2, N2, and He are determined using a tunable diode laser spectrometer at room temperature. The coefficients obtained were 0.183(5)/cm/atm for C3H8-H2, 0.119(2) for C3H8-N2, and 0.105(2) for C3H8-He. The possible implications of the results for propane on Titan, the earth, and Saturn are noted.

  1. 4,4′-(Propane-1,3-di­yl)dipiperidinium sulfate monohydrate

    PubMed Central

    Yang, E; Song, Xu-Chun; Zhuang, Rong-Qiang

    2008-01-01

    In the title compound, C13H28N2 2+·SO4 2−·H2O, extensive hydrogen-bonding inter­actions between the protonated 4,4′-(propane-1,3-di­yl)dipiperidinium ions, the sulfate anions and the water mol­ecules lead to a three-dimensional pillared and layered structure with the 4,4′-(propane-1,3-di­yl)­dipiperidinium ions acting as the pillars. PMID:21201745

  2. The synergistic effect of Rh-Ni catalysts on the highly-efficient dehydrogenation of aqueous hydrazine borane for chemical hydrogen storage.

    PubMed

    Zhong, Di-Chang; Aranishi, Kengo; Singh, Ashish Kumar; Demirci, Umit B; Xu, Qiang

    2012-12-21

    An Rh(4)Ni alloy nanocatalyst exhibits highly-efficient performance in dehydrogenation of aqueous hydrazine borane. The hydrogen selectivity reaches almost 100%. More interestingly, catalyzed by the Rh(4)Ni nanocatalyst, the dehydrogenation of aqueous hydrazine borane is not simply divided into two steps. PMID:23064157

  3. Vacuum Surface Science Meets Heterogeneous Catalysis: Dehydrogenation of a Liquid Organic Hydrogen Carrier in the Liquid State.

    PubMed

    Matsuda, Takashi; Taccardi, Nicola; Schwegler, Johannes; Wasserscheid, Peter; Steinrück, Hans-Peter; Maier, Florian

    2015-06-22

    Ultrahigh vacuum (UHV) surface science techniques are used to study the heterogeneous catalytic dehydrogenation of a liquid organic hydrogen carrier in its liquid state close to the conditions of real catalysis. For this purpose, perhydrocarbazole (PH), otherwise volatile under UHV, is covalently linked as functional group to an imidazolium cation, forming a non-volatile ionic liquid (IL). The catalysed dehydrogenation of the PH unit as a function of temperature is investigated for a Pt foil covered by a macroscopically thick PH-IL film and for Pd particles suspended in the PH-IL film, and for PH-IL on Au as inert support. X-ray photoelectron spectroscopy and thermal desorption spectroscopy allows us to follow in situ the catalysed transition of perhydrocarbazole to carbazole at technical reaction temperatures. The data demonstrate the crucial role of the Pt and Pd catalysts in order to shift the dehydrogenation temperature below the critical temperature of thermal decomposition. PMID:25891821

  4. Ultrasound promoted catalytic liquid-phase dehydrogenation of isopropanol for Isopropanol-Acetone-Hydrogen chemical heat pump.

    PubMed

    Xu, Min; Xin, Fang; Li, Xunfeng; Huai, Xiulan; Liu, Hui

    2015-03-01

    The apparent kinetic of the ultrasound assisted liquid-phase dehydrogenation of isopropanol over Raney nickel catalyst was determined in the temperature range of 346-353 K. Comparison of the effects of ultrasound and mechanical agitation on the isopropanol dehydrogenation was investigated. The ultrasound assisted dehydrogenation rate was significantly improved when relatively high power density was used. Moreover, the Isopropanol-Acetone-Hydrogen chemical heat pump (IAH-CHP) with ultrasound irradiation, in which the endothermic reaction is exposure to ultrasound, was proposed. A mathematical model was established to evaluate its energy performance in term of the coefficient of performance (COP) and the exergy efficiency, into which the apparent kinetic obtained in this work was incorporated. The operating performances between IAH-CHP with ultrasound and mechanical agitation were compared. The results indicated that the superiority of the IAH-CHP system with ultrasound was present even if more than 50% of the power of the ultrasound equipment was lost. PMID:25246094

  5. Computational investigation of NH3 adsorption and dehydrogenation on a W-modified Fe(111) surface.

    PubMed

    Hsiao, Ming-Kai; Su, Chia-Hao; Liu, Ching-Yang; Chen, Hui-Lung

    2015-11-11

    Hydrogen gas will play an important role in the future since it could be a replacement for gasoline, heating oil, natural gas, and other fuels. In previous reports ammonia (NH3), which has a high hydrogen content, provides a promising mode for the transferring and storing of hydrogen for its on-site generation. Therefore, the dehydrogenation of NH3 on a metal surface has been studied widely in the last few decades. In our study, we employed monolayer tungsten metal to modify the Fe(111) surface, denoted as W@Fe(111), and calculated the adsorption and dehydrogenation behaviors of NH3 on W@Fe(111) surface via first-principles calculations based on density functional theory (DFT). The three adsorption sites of the surface, top (T), 3-fold-shallow (S), and 3-fold-deep (D) were considered. The most stable structure of the NHx (x = 0-3) species on the surface of W@Fe(111) have been predicted. The calculated activation energies for NHx (x = 1-3) dehydrogenations are 19.29 kcal mol(-1) (for H2N-H bond activation), 29.17 kcal mol(-1) (for HN-H bond activation) and 27.94 kcal mol(-1) (for N-H bond activation), and the entire process is exothermic by 33.05 kcal mol(-1). To gain detailed knowledge of the catalytic processes of the NH3 molecule on the W@Fe(111) surface, the physical insights between the adsorbate/substrate interaction and interface morphology were subjected to a detailed electronic analysis. PMID:26524324

  6. Universal transition state scaling relations for (de)hydrogenation over transition metals.

    PubMed

    Wang, S; Petzold, V; Tripkovic, V; Kleis, J; Howalt, J G; Skúlason, E; Fernández, E M; Hvolbæk, B; Jones, G; Toftelund, A; Falsig, H; Björketun, M; Studt, F; Abild-Pedersen, F; Rossmeisl, J; Nørskov, J K; Bligaard, T

    2011-12-14

    We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters. PMID:21996683

  7. Intramolecular Dehydrogenative Coupling of 2,3-Diaryl Acrylic Compounds: Access to Substituted Phenanthrenes.

    PubMed

    Gupta, Vijay; Rao, V U Bhaskara; Das, Tamal; Vanka, Kumar; Singh, Ravi P

    2016-07-01

    A simple, facile, and environmentally benign intramolecular dehydrogenative coupling of various 1,2-diarylethylenes for the synthesis of phenanthrenes in excellent yield has been described. This new methodology uses ceric ammonium nitrate (CAN) as a promoter at room temperature and has been extended to intermolecular synthesis of biaryl compounds. The electron transfer from methoxyarene to cerium leads to cationic radical formation, which further proceeds to intramolecular coupling. Preliminary mechanistic investigation by EPR spectroscopy and density functional theory calculation suggested a similar view. PMID:27232691

  8. Copper nanoparticles supported on doped graphenes as catalyst for the dehydrogenative coupling of silanes and alcohols.

    PubMed

    Blandez, Juan F; Primo, Ana; Asiri, Abdullah M; Álvaro, Mercedes; García, Hermenegildo

    2014-11-10

    Copper nanoparticles (NPs) supported on a series of undoped and doped graphene materials (Gs) have been obtained by pyrolysis of alginate or chitosan biopolymers, modified or not with boric acid, containing Cu(2+) ions at 900 °C under inert atmosphere. The resulting Cu-G materials containing about 17 wt % Cu NPs (from 10 to 200 nm) exhibit high catalytic activity for the dehydrogenative coupling of silanes with alcohols. The optimal material consisting on Cu-(B)G is more efficient than Cu NPs on other carbon supports. PMID:25196304

  9. NHC-catalyzed dehydrogenative self-coupling of diphenylsilane: A facile synthesis of octaphenylcyclotetra(siloxane)

    PubMed Central

    Albright, Abigail; Gawley, Robert E.

    2011-01-01

    A unique application of the CuIPr N-heterocyclic carbene (NHC) to the dehydrogenative self-coupling of diphenylsilane has been discovered. This transformation is carried out open to air at room temperature, yielding octaphenylcyclotetra(siloxane) quantitatively in one hour. This preparation constitutes a significant improvement over existing methods for the preparation of this compound and demonstrates a novel mode of reactivity for CuIPr. The diphenylsilanone tetramer is the precursor to a number of industrially significant polymers. PMID:22058577

  10. Unprecedented Borane, Diborane(3), Diborene, and Borylene Ligands via Pt-Mediated Borane Dehydrogenation.

    PubMed

    Arnold, Nicole; Braunschweig, Holger; Dewhurst, Rian D; Ewing, William C

    2016-01-13

    Reactions of an aryldihydroborane with a Pt(0) complex lead to a range of novel products, including complexes with bridging diborene and diborane(3) ligands and a complex with both borylene and borane (M → B) ligands. The products imply varying degrees of dehydrogenation of the boron centers with concomitant formation of boron-boron bonds, which in one case is later broken. These reactions show that although the dehydrocoupling of dihydroboranes is not a straightforward process in this case, the reactions are capable of connecting boron atoms in unusual ways, leading to unprecedented bonding motifs. PMID:26667300

  11. Boryl-mediated reversible H2 activation at cobalt: catalytic hydrogenation, dehydrogenation, and transfer hydrogenation.

    PubMed

    Lin, Tzu-Pin; Peters, Jonas C

    2013-10-16

    We describe the synthesis of a cobalt(I)-N2 complex (2) supported by a meridional bis-phosphino-boryl (PBP) ligand. Complex 2 undergoes a clean reaction with 2 equiv of dihydrogen to afford a dihydridoboratocobalt dihydride (3). The ability of boron to switch between a boryl and a dihydridoborate conformation makes possible the reversible conversion of 2 and 3. Complex 3 reacts with HMe2N-BH3 to give a hydridoborane cobalt tetrahydridoborate complex. We explore this boryl-cobalt system in the context of catalytic olefin hydrogenation as well as amine-borane dehydrogenation/transfer hydrogenation. PMID:24079337

  12. Formic acid dehydrogenation catalysed by ruthenium complexes bearing the tripodal ligands triphos and NP3.

    PubMed

    Mellone, Irene; Peruzzini, Maurizio; Rosi, Luca; Mellmann, Dörthe; Junge, Henrik; Beller, Matthias; Gonsalvi, Luca

    2013-02-21

    The selective formic acid dehydrogenation to a mixture of CO(2) and H(2) was achieved with moderate to good productivities in the presence of homogeneous Ru catalysts bearing the polydentate tripodal ligands 1,1,1-tris-(diphenylphosphinomethyl)ethane (triphos) and tris-[2-(diphenylphosphino)ethyl]amine (NP(3)), either made in situ from suitable Ru(III) precursors or as molecular complexes. Preliminary mechanistic studies highlighting subtle differences due to ligand effects in the corresponding systems under study are also presented. PMID:23212285

  13. Ammonia-Borane and Amine-Borane Dehydrogenation Mediated by Complex Metal Hydrides.

    PubMed

    Rossin, Andrea; Peruzzini, Maurizio

    2016-08-10

    This review is a comprehensive survey of the last 10 years of research on ammonia-borane and amine-borane dehydrogenation mediated by complex metal hydrides (CMHs), within the broader context of chemical hydrogen storage. The review also collects those cases where CMHs are the catalyst spent form or its resting state. Highlights on the reaction mechanism (strictly dependent on the CMH of choice) and the catalysts efficiency (in terms of equivalents of H2 produced and relative reaction rates) are provided throughout the discussion. PMID:27075435

  14. Size-controllable APTS stabilized ruthenium(0) nanoparticles catalyst for the dehydrogenation of dimethylamine-borane at room temperature.

    PubMed

    Zahmakıran, Mehmet; Philippot, Karine; Özkar, Saim; Chaudret, Bruno

    2012-01-14

    Dimethylamine-borane, (CH(3))(2)NHBH(3), has been considered as one of the attractive materials for the efficient storage of hydrogen, which is still one of the key issues in the "Hydrogen Economy". In a recent communication we have reported the synthesis and characterization of 3-aminopropyltriethoxysilane stabilized ruthenium(0) nanoparticles with the preliminary results for their catalytic performance in the dehydrogenation of dimethylamine-borane at room temperature. Herein, we report a complete work including (i) effect of initial [APTS]/[Ru] molar ratio on both the size and the catalytic activity of ruthenium(0) nanoparticles, (ii) collection of extensive kinetic data under non-MTL conditions depending on the substrate and catalyst concentrations to define the rate law of Ru(0)/APTS-catalyzed dehydrogenation of dimethylamine-borane at room temperature, (iii) determination of activation parameters (E(a), ΔH(#) and ΔS(#)) for Ru(0)/APTS-catalyzed dehydrogenation of dimethylamine-borane; (iv) demonstration of the catalytic lifetime of Ru(0)/APTS nanoparticles in the dehydrogenation of dimethylamine-borane at room temperature, (v) testing the bottlability and reusability of Ru(0)/APTS nanocatalyst in the room-temperature dehydrogenation of dimethylamine-borane, (vi) quantitative carbon disulfide (CS(2)) poisoning experiments to find a corrected TTO and TOF values on a per-active-ruthenium-atom basis, (vii) a summary of extensive literature review for the catalysts tested in the catalytic dehydrogenation of dimethylamine-borane as part of the results and discussions. PMID:22052298

  15. Millisecond Oxidation of Alkanes

    SciTech Connect

    Scott Han

    2011-09-30

    This project was undertaken in response to the Department of Energy's call to research and develop technologies 'that will reduce energy consumption, enhance economic competitiveness, and reduce environmental impacts of the domestic chemical industry.' The current technology at the time for producing 140 billion pounds per year of propylene from naphtha and Liquified Petroleum Gas (LPG) relied on energy- and capital-intensive steam crackers and Fluidized Catalytic Cracking (FCC) units. The propylene is isolated from the product stream in a costly separation step and subsequently converted to acrylic acid and other derivatives in separate production facilities. This project proposed a Short Contact Time Reactor (SCTR)-based catalytic oxydehydrogenation process that could convert propane to propylene and acrylic acid in a cost-effective and energy-efficient fashion. Full implementation of this technology could lead to sizeable energy, economic and environmental benefits for the U. S. chemical industry by providing up to 45 trillion BTUs/year, cost savings of $1.8 billion/year and a combined 35 million pounds/year reduction in environmental pollutants such as COx, NOx, and SOx. Midway through the project term, the program directive changed, which approval from the DOE and its review panel, from direct propane oxidation to acrylic acid at millisecond contact times to a two-step process for making acrylic acid from propane. The first step was the primary focus, namely the conversion of propane to propylene in high yields assisted by the presence of CO2. The product stream from step one was then to be fed directly into a commercially practiced propylene-to-acrylic acid tandem reactor system.

  16. A DFT study on the Cu (1 1 1) surface for ethyl acetate synthesis from ethanol dehydrogenation

    NASA Astrophysics Data System (ADS)

    Li, Ruzhen; Zhang, Minhua; Yu, Yingzhe

    2012-07-01

    Copper-based catalysts have shown excellent catalytic performances. Despite extensive studies in the field, the microscopic mechanism of ethanol dehydrogenation to ethyl acetate (EA) on Cu-based catalysts remains controversial. Aiming to provide insight into the catalytic roles of Cu, density functional theory (DFT) calculations have been performed to study the elementary reactions involved in ethanol dehydrogenation to EA on Cu surfaces. In this work, the adsorption properties of ethanol, ethoxy, acetaldehyde, acetyl and EA on the Cu (1 1 1) catalyst surface were investigated. Based on two pathways, many transition states involved are located. The results show that the route proposed by Colley is more likely to happen.

  17. RETENTION OF HALOCARBONS ON A HEXAFLUOROPROPYLENE EPOXIDE-MODIFIED GRAPHITIZED CARBON BLACK - IV. PROPANE- BASED COMPOUNDS

    EPA Science Inventory

    The retention characteristics of 25 propane-based bromofluorocarbon, chlorocarbon, chlorofluorocarbon, and fluorocarbon fluids have been studied as a function of temperature on a stationary phase consisting of a 5% (m/m) coating of a low-molecular-mass polymer of hexafluoropropyl...

  18. 16 CFR Figure 7 to Part 1633 - Elements of Propane Flow Control for Each Burner

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Elements of Propane Flow Control for Each Burner 7 Figure 7 to Part 1633 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS Pt.1633, Fig. 7 Figure...

  19. 16 CFR Figure 7 to Part 1633 - Elements of Propane Flow Control for Each Burner

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Elements of Propane Flow Control for Each Burner 7 Figure 7 to Part 1633 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS Pt.1633, Fig. 7 Figure...

  20. 16 CFR Figure 7 to Part 1633 - Elements of Propane Flow Control for Each Burner

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Elements of Propane Flow Control for Each Burner 7 Figure 7 to Part 1633 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS Pt. 1633, Fig. 7 Figure...

  1. 16 CFR Figure 7 to Part 1633 - Elements of Propane Flow Control for Each Burner

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Elements of Propane Flow Control for Each Burner 7 Figure 7 to Part 1633 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS Pt.1633, Fig. 7 Figure...

  2. 16 CFR Figure 7 to Part 1633 - Elements of Propane Flow Control for Each Burner

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Elements of Propane Flow Control for Each Burner 7 Figure 7 to Part 1633 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS Pt. 1633, Fig. 7 Figure...

  3. Evaluation of propane combustion traps for collection of Phlebotomus papatasi (Scopoli) in southern Israel.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Traps used for mosquitoes can possibly used to capture phlebotomine sand flies as well, but little testing has been done. Traps powered by propane could be extremely useful because most produce their own carbon dioxide (CO2), which can increase the number of sand flies captured. Scientists at the US...

  4. Analysis of U.S. Propane Markets Winter 1996-97, An

    EIA Publications

    1997-01-01

    This study constitutes an examination of propane supply, demand, and price developments and trends. The Energy Information Administration's approach focused on identifying the underlying reasons for the tight supply/demand balance in the fall of 1996, and on examining the potential for a recurrence of these events next year.

  5. THE HEAT CAPACITY OF FLUORINATED PROPANE AND BUTANE DERIVATIVES BY DIFFERENTIAL SCANNING CALORIMETRY

    EPA Science Inventory

    The paper gives results of the measurement (to 3% accuracy) of the constant-pressure liquid-phase heat capacities of 21 hydrogen-containing fluorinated propane and butane derivatives and one fluorinated ether (CF3OCF2H) with boiling points ranging from -34.6 to 76.7 C, using diff...

  6. EXTINCTION STUDIES OF PROPANE/AIR COUNTERFLOW DIFFUSION FLAMES: THE EFFECTIVENESS OF AEROSOLS

    EPA Science Inventory

    The fire suppression effectiveness of solid aerosols as suitable halon replacements has examined. Experiments were performed in a counterflow diffusion burner, consisting of two 1 cm i.d. tubes separated by 1 cm. Aerosols were delivered to propane/air flames in the air flow. Both...

  7. HOMOGENEOUS HYDROLYSIS RATE CONSTANTS FOR SELECTED CHLORINATED METHANES, ETHANES, ETHENES, AND PROPANES

    EPA Science Inventory

    Hydrolysis rate constants of 18 chlorinated methanes, ethanes, ethenes, and propanes have been measured in dilute aqueous solutions within the temperature range of 0 to 180 oC and at pH values of 3 to l4. rrhenius parapmeters were determined for both neutral and alkaline hydrolys...

  8. 40 CFR 721.10360 - 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene glycol mono...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-(triethoxysilyl)-, reaction products with polyethylene glycol mono-(branched tridecyl) ether (generic). 721.10360... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10360 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene...

  9. 40 CFR 721.10360 - 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene glycol mono...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-(triethoxysilyl)-, reaction products with polyethylene glycol mono-(branched tridecyl) ether (generic). 721.10360... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10360 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene...

  10. 40 CFR 721.10360 - 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene glycol mono...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-(triethoxysilyl)-, reaction products with polyethylene glycol mono-(branched tridecyl) ether (generic). 721.10360... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10360 1-Substituted propane, 3-(triethoxysilyl)-, reaction products with polyethylene...

  11. Performance and emissions of a catalytic reactor with propane, diesel, and Jet A fuels

    NASA Technical Reports Server (NTRS)

    Anderson, D. N.

    1977-01-01

    Tests were made to determine the performance and emissions of a catalytic reactor operated with propane, No. 2 diesel, and Jet A fuels. A 12-cm diameter and 16-cm long catalytic reactor using a proprietary noble metal catalyst was operated at an inlet temperature of 800 K, a pressure of 300,000 Pa and reference velocities of 10 to 15 m/s. No significant differences between the performance of the three fuels were observed when 98.5 percent purity propane was used. The combustion efficiency for 99.8-percent purity propane tested later was significantly lower, however. The diesel fuel contained 135 ppm of bound nitrogen and consequently produced the highest NOx emissions of the three fuels. As much as 85 percent of the bound nitrogen was converted to NOx. Steady-state emissions goals based on half the most stringent proposed automotive standards were met when the reactor was operated at an adiabatic combustion temperature higher than 1350 K with all fuels except the 99.8-percent purity propane. With that fuel, a minimum temperature of 1480 K was required.

  12. Developing synthesis techniques for zeolitic-imidazolate framework membranes for high resolution propylene/propane separation

    NASA Astrophysics Data System (ADS)

    Kwon, Hyuk Taek

    Propylene/propane separation is one of the most challenging separations, currently achieved by energy-intensive cryogenic distillation. Despite the great potentials for energy-efficient membrane-based propylene/propane separation processes, no commercial membranes are available due to the limitations (i.e., low selectivity) of current polymeric materials. Zeolitic imidazolate frameworks (ZIFs) are promising membrane materials primarily due to their well-defined ultra-micropores with controllable surface chemistry along with their relatively high thermal/chemical stabilities. In particular, ZIF-8 with the effective aperture size of ~ 4.0 A has been shown very promising for propylene/propane separation. Despite the extensive research on ZIF-8 membranes, only a few of ZIF-8 membranes have displayed good propylene/propane separation performances presumably due to the challenges of controlling the microstructures of polycrystalline membranes. Since the membrane microstructures are greatly influenced by processing techniques, it is critically important to develop new techniques. In this dissertation, three state-of-the-art ZIF membrane synthesis techniques are developed. The first is a one-step in-situ synthesis technique based on the concept of counter diffusion. The technique enabled us to obtain highly propylene selective ZIF-8 membranes in less than a couple of hours with exceptional mechanical strength. Most importantly, due to the nature of the counter-diffusion concept, the new method offered unique opportunities such as healing defective membranes (i.e., poorly-intergrown) as well as significantly reducing the consumption of costly ligands and organic solvents. The second is a microwave-assisted seeding technique. Using this new seeding technique, we were able to prepare seeded supports with a high packing density in a couple of minutes, which subsequently grown into highly propylene-selective ZIF-8 membranes with an average propylene/propane selectivity of ~40

  13. Catalytic dehydrogenation of propanol-2 on Na-Zr phosphates containing Cu, Co, and Ni

    NASA Astrophysics Data System (ADS)

    Povarova, E. I.; Pylinina, A. I.; Mikhalenko, I. I.

    2012-06-01

    The dehydrogenation of propanol-2 on sodium-zirconium phosphates (NZP) with the composition Na1 - 2 x M x Zr2(PO4)3 ( x = 0.125 and 0.25) in which Na+ ions were replaced by M2+ = Co2+, Ni2+, and Cu2+ ions was studied. The experimental reaction activation energy E a decreased while transition through the T* = 310-340°C temperature; above this temperature, the electrophysical and crystallographic properties of the material changed. These changes were explained by the reversible transfer of Me2+ ions from position M1 to M2 in the NZP lattice. Me2+ centers with different alcohol adsorption forms at T < T* (one-point) and T > T* (two-point) participated in the dehydrogenation reaction. For the first form, E a and the logarithm of the preexponential factor linearly correlated with the ionic radius of M2+. The activity of M-NZP catalysts altered in repeated experiments and in cases when the direction of temperature variations changed.

  14. Engineering Escherichia coli for selective geraniol production with minimized endogenous dehydrogenation.

    PubMed

    Zhou, Jia; Wang, Chonglong; Yoon, Sang-Hwal; Jang, Hui-Jeong; Choi, Eui-Sung; Kim, Seon-Won

    2014-01-01

    Geraniol, a monoterpene alcohol, has versatile applications in the fragrance industry, pharmacy and agrochemistry. Moreover, geraniol could be an ideal gasoline alternative. In this study, recombinant overexpression of geranyl diphosphate synthase and the bottom portion of a foreign mevalonate pathway in Escherichia coli MG1655 produced 13.3mg/L of geraniol. Introduction of Ocimum basilicum geraniol synthase increased geraniol production to 105.2mg/L. However, geraniol production encountered a loss from its endogenous dehydrogenization and isomerization into other geranoids (nerol, neral and geranial). Three E. coli enzymes (YjgB, YahK and YddN) were identified with high sequence identity to plant geraniol dehydrogenases. YjgB was demonstrated to be the major one responsible for geraniol dehydrogenization. Deletion of yjgB increased geraniol production to 129.7mg/L. Introduction of the whole mevalonate pathway for enhanced building block synthesis from endogenously synthesized mevalonate improved geraniol production up to 182.5mg/L in the yjgB mutant after 48h of culture, which was a double of that obtained in the wild type control (96.5mg/L). Our strategy for improving geraniol production in engineered E. coli should be generalizable for addressing similar problems during metabolic engineering. PMID:24269531

  15. Iridium-catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of syngas.

    PubMed

    Olsen, Esben P K; Madsen, Robert

    2012-12-01

    A new iridium-catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)(2)Cl](2) (coe = cyclooctene) and racemic 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (rac-BINAP) in a mesitylene solution saturated with water. A catalytic amount of lithium chloride was also added to improve the catalyst turnover. The reaction has been applied to a variety of primary alcohols and gives rise to products in good to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)-BINAP species. First, dehydrogenation of the primary alcohol to the corresponding aldehyde takes place, which is then followed by decarbonylation to the product with one less carbon atom. PMID:23108889

  16. Radical-mediated dehydrogenation of bile acids by means of hydrogen atom transfer to triplet carbonyls.

    PubMed

    Miro, P; Marin, M L; Miranda, M A

    2016-03-01

    The aim of the present paper is to explore the potential of radical-mediated dehydrogenation of bile salts (BSs), which is reminiscent of the enzymatic action of hydroxysteroid dehydrogenase enzymes (HSDH). The concept has been demonstrated using triplet carbonyls that can be efficiently generated upon selective UVA-excitation. Hydrogen atom transfer (HAT) from BSs to triplet benzophenone (BP) derivatives gave rise to radicals, ultimately leading to reduction of the BP chromophore with concomitant formation of the oxo-analogs of the corresponding BSs. The direct reactivity of triplet BP with BSs in the initial step was evaluated by determining the kinetic rate constants using laser flash photolysis (LFP). The BP triplet decay was monitored (λmax = 520 nm) upon addition of increasing BS concentrations, and the obtained rate constant values indicated a reactivity of the methine hydrogen atoms in the order of C-3 < C-12 < C-7. The steady-state kinetics of the overall process, monitored through the disappearance of the typical BP absorption band at 260 nm, was much faster under N2 than under O2, also supporting the role of the oxygen-quenchable triplet in the dehydrogenation process. Furthermore, irradiation of deaerated aqueous solutions of sodium cholate in the presence of KPMe provided the oxo-analogs, 3[O],7[O]-CA, 3[O]-CA and 7[O]-CA, arising from the HAT process. PMID:26833240

  17. Chemical and hydrogen isotope evidence for in situ dehydrogenation of biotite in silicic magma chambers

    NASA Astrophysics Data System (ADS)

    Feeley, T. C.; Sharp, Z. D.

    1996-11-01

    To examine the potential for volatile fluxing of magma chambers by in situ degassing of hydrous minerals, we obtained complete chemical analyses for biotite separates from silicic lavas. The separates exhibit unusually low H2O contents that inversely correlate with host lava temperatures, high Fe3+/Fe2+ ratios that inversely correlate with host lava oxygen fugacities, and the highest δ D values yet reported for biotite from any silicic igneous rock (up to -19‰). These results are direct evidence for selective loss of protium (1H) from biotite during dehydrogenation in magma chambers heated from below by intrusion of mafic magma. The maximum PΔV energy generated from dehydrogenation alone can approach 2 × 103 joules per kilogram of magma. This finding provides support for the concept that injection of mafic magma coupled with sudden degassing of hydrous minerals in a volatile-rich magma chamber can increase pressure, and thus enhance the possibility of initiating a volcanic eruption.

  18. ENHANCEMENT OF EQUILIBRIUMSHIFT IN DEHYDROGENATION REACTIONS USING A NOVEL MEMBRANE REACTOR

    SciTech Connect

    Shamsuddin Ilias, Ph.d., P.E.; Franklin G. King, D.Sc.

    2001-02-13

    With the advances in new inorganic materials and processing techniques, there has been renewed interest in exploiting the benefits of membranes in many industrial applications. Inorganic and composite membranes are being considered as potential candidates for use in membrane-reactor configuration for effectively increasing reaction rate, selectivity and yield of equilibrium limited reactions. To investigate the usefulness of a palladium-ceramic composite membrane in a membrane reactor-separator configuration, we investigated the dehydrogenation of cyclohexane by equilibrium shift. A two-dimensional pseudo-homogeneous reactor model was developed to study the dehydrogenation of cyclohexane by equilibrium shift in a tubular membrane reactor. Radial diffusion was considered to account for the concentration gradient in the radial direction due to permeation through the membrane. For a dehydrogenation reaction, the feed stream to the reaction side contained cyclohexane and argon, while the separation side used argon as the sweep gas. Equilibrium conversion for dehydrogenation of cyclohexane is 18.7%. The present study showed that 100% conversion could be achieved by equilibrium shift using Pd-ceramic membrane reactor. For a feed containing cyclohexane and argon of 1.64 x 10{sup -6} and 1.0 x 10{sup -3} mol/s, over 98% conversion could be readily achieved. The dehydrogenation of cyclohexane was also experimentally investigated in a palladium-ceramic membrane reactor. The Pd-ceramic membrane was fabricated by electroless deposition of palladium on ceramic substrate. The performance of Pd-ceramic membrane was compared with a commercially available hydrogen-selective ceramic membrane. From limited experimental data it was observed that by appropriate choice of feed flow rate and sweep gas rate, the conversion of cyclohexane to benzene and hydrogen can increased to 56% at atmospheric pressure and 200 C in a Pd-ceramic membrane reactor. In the commercial ceramic membrane

  19. Surface-initiated dehydrogenative polymerization of monolignols: a quartz crystal microbalance with dissipation monitoring and atomic force microscopy study.

    PubMed

    Wang, Chao; Qian, Chen; Roman, Maren; Glasser, Wolfgang G; Esker, Alan R

    2013-11-11

    This work highlights a real-time and label-free method to monitor the dehydrogenative polymerization of monolignols initiated by horseradish peroxidase (HRP) physically immobilized on surfaces using a quartz crystal microbalance with dissipation monitoring (QCM-D). The dehydrogenative polymer (DHP) films are expected to provide good model substrates for studying ligninolytic enzymes. The HRP was adsorbed onto gold or silica surfaces or onto and within porous desulfated nanocrystalline cellulose films from an aqueous solution. Surface-immobilized HRP retained its activity and selectivity for monolignols as coniferyl and p-coumaryl alcohol underwent dehydrogenative polymerization in the presence of hydrogen peroxide, whereas sinapyl alcohol polymerization required the addition of a nucleophile. The morphologies of the DHP layers on the surfaces were investigated via atomic force microscopy (AFM). Data from QCM-D and AFM showed that the surface-immobilized HRP-initiated dehydrogenative polymerization of monolignols was greatly affected by the support surface, monolignol concentration, hydrogen peroxide concentration, and temperature. PMID:24032374

  20. Facile preparation of β-/γ-MgH₂ nanocomposites under mild conditions and pathways to rapid dehydrogenation.

    PubMed

    Xiao, Xuezhang; Liu, Zhe; Saremi-Yarahmadi, Sina; Gregory, Duncan H

    2016-04-21

    A magnesium hydride composite with enhanced hydrogen desorption kinetics can be synthesized via a simple wet chemical route by ball milling MgH2 with LiCl as an additive at room temperature followed by tetrahydrofuran (THF) treatment under an Ar atmosphere. The as-synthesized composite comprises ca. 18 mass% orthorhombic γ-MgH2 and 80 mass% tetragonal β-MgH2 as submicron-sized particles. The β-/γ-MgH2 nanocomposite exhibits a dehydrogenation capacity of 6.6 wt% and starts to release hydrogen at ∼260 °C; ca. 140 °C lower than that of commercial MgH2. The apparent activation energy for dehydrogenation is 115 ± 3 kJ mol(-1), which is ca. 46% lower than that of commercial MgH2. Analysis suggests that the meta-stable γ-MgH2 component either directly dehydrogenates exothermically or first transforms into stable β-MgH2 very close to the dehydrogenation onset. The improved hydrogen release performance can be attributed both to the existence of the MgH2 nanostructure and to the presence of γ-MgH2. PMID:27030171