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Sample records for acyl-coa dehydrogenation deficiency

  1. Specific glutaryl-CoA dehydrogenating activity is deficient in cultured fibroblasts from glutaric aciduria patients

    Patients with glutaric aciduria (GA) have greatly increased urinary excretion of glutarate. Their leukocyte and fibroblast sonicates have deficient ability to produce 14CO2 from [1,5-14C]glutaryl-CoA, an enzymatic process with two sequential reaction steps, dehydrogenation and decarboxylation. In normal individuals, it is not known whether these two reaction steps require one or two enzymes, and currently it is assumed that a single enzyme, glutaryl-CoA dehydrogenase (GDH), carries out these two reactions. Since GA patients also excrete increased amounts of 3-hydroxyglutarate and glutaconate in urine, it was thought that glutaryl-CoA in these patients may be dehydrogenated but not decarboxylated. We developed a new assay specific for glutaryl-CoA dehydrogenation which measures enzyme-catalyzed tritium release from [2,3,4-3H]glutaryl-CoA, and we studied the glutaryl-CoA dehydrogenating activity in cultured normal human fibroblasts and those from patients with GA. The Michaelis constant (Km) of normal human fibroblast GDH for [2,3,4-3H]glutaryl-CoA was 5.9 microM, and activity was severely inhibited by (methylenecyclopropyl)acetyl-CoA at low concentrations. Sonicates from all five GA fibroblast lines examined showed 2-9% of control glutaryl-CoA dehydrogenating activity, corresponding to the deficient 14CO2 releasing activity. These results indicate either that the conversion of glutaryl-CoA to crotonyl-CoA is accomplished by two enzymes, and patients with GA are deficient in the activity of the first component, or alternatively, that this process is carried out by a single enzyme which is deficient in these patients. It is unlikely that urinary glutaconate and 3-hydroxyglutarate in GA patients are produced via GDH

  2. Clear relationship between ETF/ETFDH genotype and phenotype in patients with multiple acyl-CoA dehydrogenation deficiency

    Olsen, Rikke K J; Andresen, Brage S; Christensen, Ernst;

    2003-01-01

    Mutations in electron transfer flavoprotein (ETF) and its dehydrogenase (ETFDH) are the molecular basis of multiple acyl-CoA dehydrogenation deficiency (MADD), an autosomal recessively inherited and clinically heterogeneous disease that has been divided into three clinical forms: a neonatal...

  3. DNA-based prenatal diagnosis for severe and variant forms of multiple acyl-CoA dehydrogenation deficiency

    Olsen, Rikke K J; Andresen, Brage S; Christensen, Ernst;

    2005-01-01

    OBJECTIVES: Multiple acyl-CoA dehydrogenation deficiency (MADD) is a clinically heterogeneous disorder of mitochondrial fatty acid, amino acid, and choline oxidation due to mutations in the genes encoding electron transfer flavoprotein (ETF) or ETF ubiquinone oxidoreductase (ETFQO). So far...

  4. ETFDH mutations as a major cause of riboflavin-responsive multiple acyl-CoA dehydrogenation deficiency

    Olsen, Rikke K J; Olpin, Simon E; Andresen, Brage S;

    2007-01-01

    Multiple acyl-CoA dehydrogenation deficiency (MADD) is a disorder of fatty acid, amino acid and choline metabolism that can result from defects in two flavoproteins, electron transfer flavoprotein (ETF) or ETF: ubiquinone oxidoreductase (ETF:QO). Some patients respond to pharmacological doses of...

  5. The ETFDH c.158A>G Variation Disrupts the Balanced Binding of ESE and ESS Proteins Causing Missplicing and Multiple acyl-CoA Dehydrogenation Deficiency

    Olsen, Rikke K J; Brøner, Sabrina; Sabaratnam, Rugivan;

    2013-01-01

    Multiple acyl-CoA dehydrogenation deficiency is a disorder of fatty acid and amino acid oxidation caused by defects of electron transfer flavoprotein (ETF) or its dehydrogenase (ETFDH). A clear relationship between genotype and phenotype makes genotyping of patients important not only diagnostica......Multiple acyl-CoA dehydrogenation deficiency is a disorder of fatty acid and amino acid oxidation caused by defects of electron transfer flavoprotein (ETF) or its dehydrogenase (ETFDH). A clear relationship between genotype and phenotype makes genotyping of patients important not only...

  6. Lipid-storage myopathy and respiratory insufficiency due to ETFQO mutations in a patient with late-onset multiple acyl-CoA dehydrogenation deficiency

    Olsen, Rikke Katrine Jentoft; Pourfarzam, M; Morris, A A M;

    2004-01-01

    We report a patient with lipid-storage myopathy due to multiple acyl-CoA dehydrogenation deficiency (MADD). Molecular genetic analysis showed that she was compound heterozygous for mutations in the gene for electron transfer flavoprotein:ubiquinone oxidoreductase (ETFQO). Despite a good initial...

  7. Transient multiple acyl-CoA dehydrogenation deficiency in a newborn female caused by maternal riboflavin deficiency

    Chiong, M A; Sim, K G; Carpenter, K;

    2007-01-01

    A newborn female presented on the first day of life with clinical and biochemical findings consistent with multiple acyl-CoA dehydrogenase deficiency (MADD). Riboflavin supplementation corrected the biochemical abnormalities 24 h after commencing the vitamin. In vitro acylcarnitine profiling in i...

  8. Deficiencies

    U.S. Department of Health & Human Services — A list of all deficiencies currently listed on Nursing Home Compare, including the nursing home that received the deficiency, the associated inspection date,...

  9. Catalytic dehydrogenations of ethylbenzene to styrene

    Nederlof, C.

    2012-01-01

    This research work on the catalytic dehydrogenation of ethylbenzene (EB) to styrene (ST) had a primary goal of developing improved catalysts for dehydrogenation processes both in CO2 as well as with O2 that can compete with the conventional dehydrogenation process in steam. In order to achieve this

  10. Liver fatty acid binding protein (LFABP) transfers fatty acids and fatty acyl coas to membranes

    De Gerónimo, Eduardo; Hagan, Robert M; Wilton, David C.; Córsico, Betina

    2010-01-01

    The objective of this work was to analyze LFABP´s capacity to transfer acyl CoAs to artificial membranes and compare it to LCFA transfer employing natural ligands, in order to better understand the specific physiological role of LFABP in the cell.

  11. Catalysts for Dehydrogenation of ammonia boranes

    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.

  12. Alkane dehydrogenation over supported chromium oxide catalysts

    Weckhuysen, B.M.; Schoonheydt, R.A.

    1999-01-01

    The dehydrogenation of alkanes over supported chromium oxide catalysts in the absence of oxygen is of high interest for the industrial production of propene and isobutene. In this review, a critical overview is given of the current knowledge nowadays available about chromium-based dehydrogenation ca

  13. Shale gas opportunities. Dehydrogenation of light alkanes

    Patcas, F.C.; Dieterle, M.; Rezai, A.; Asprion, N. [BASF SE, Ludwigshafen (Germany)

    2013-11-01

    The discovery and use of shale gas in North America has become a game changer for the chemical industry by access to a cheaper feedstock compared to conventional oil. Increased number of ethane crackers spurred increasing interest in light alkanes dehydrogenation. Several companies have announced their interest in new propane dehydrogenation units in North America. BASF is developing light alkanes dehydrogenation technologies for two decades now. BASF developed jointly with Linde the isothermal C3 dehydrogenation process. The latest dehydrogenation catalyst development at BASF focused on a supported and steam resistant Pt-Sn catalyst which yielded excellent selectivity and activity. Intense research work both internally as well as in cooperation with universities contributed to the understanding of the relationship between the surface structure and catalyst performances like activity, selectivity and coking resistance. Using such type of catalysts BASF developed an autothermal propane dehydrogenation as well as a butane dehydrogenation process. The most recent catalyst development was a dehydrogenation catalyst coated on a honeycomb monolith to improve catalyst usage and pressure drop. This will probably be the first industrial usage of catalytic monoliths in a chemical synthesis process. (orig.) (Published in summary form only)

  14. Dehydrogenation of benzene on Pt(111) surface

    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.

  15. Supported organoiridium catalysts for alkane dehydrogenation

    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.

  16. Catalytic Conversion of Methanol by Oxidative Dehydrogenation

    2007-01-01

    This study investigates the effects of addition of oxygen on the oxidative dehydrogenation (ODH) of methanol when a fluorotetrasilicic mica ion-exchanged with palladium (Pd2+-TSM) was used as the catalyst. The reaction proceeded at a very low temperature in the presence of oxygen, and HCOOCH3 was obtained at high selectivity. By calculating the equilibrium conversion, it has been shown that substantial ODH took place for HCOOCH3 production. Consequently, this reaction would make dehydrogenation the dominant reaction at equilibrium. Not all the H dissociated from CH3OH was converted to H2O by oxidation. It has been shown that the H2O was not produced from oxidative dehydrogenation by the direct reaction of CH3OH and O2 when an attempt was made to carry out oxidative dehydrogenation using an isotope oxygen trace method in the gas phase. Therefore, when CH3OH was converted to CO2 and dehydrogenated to HCOOCH3, the C-O bonds were not dissociated.

  17. Oxidative dehydrogenation of light alkanes

    Meiswinkel, A.; Thaller, C.; Bock, M.; Alvarado, L. [Linde AG, Pullach (Germany); Hartmann, D.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen (Germany)

    2012-07-01

    The demand of light olefins increases steadily and the current steam cracking production is highly energy demanding. This motivates the development of alternative production processes like the oxidative dehydrogenation (ODH) of light alkanes operating at comparably low temperatures. Multi-component oxides are reported to show excellent catalytic performance in the ODH. Especially, MoVTeNbO oxides present high activity and selectivity in ODH of ethane. Synthesis of MoVTeNb oxides was done by a hydrothermal method. Qualitative and quantitative phase analysis were performed by X-ray diffraction and Rietveld refinement. Surface compositions were determined by Low energy ion scattering (LEIS). Catalytic tests were carried out in a fixed bed plug flow reactor using ethane and oxygen diluted in helium, as gaseous feed. Based on laboratory investigations a first upscale to a bench-top-pilot unit was performed in order to evaluate the large scale and long term feasibility of the process under technically relevant conditions. MoVTeNb oxides show high activity combined with excellent selectivity in the ODH of ethane to ethylene (S > 95% at X < 40%). Phase analysis reveals the presence of M1, M2 and amorphous phases. Literature reports the crystalline M1 phase as essential for the performance. Indeed, the crystalline M1 phase impacts on the activity via exposing V on the surface being apparently vital to achieve an active material. A correlation of the apparent activation energy with the surface vanadium composition of the catalysts is noticed, however, surprisingly with no major impact on the ethene selectivity. As this material was identified as most promising for a technical application a scale up from less than 1g to 50g of catalyst was performed in a bench-top-pilot unit. The reaction has a significant adiabatic temperature rise and the handling of the reaction heat is a major challenge for process engineering. Furthermore different diluent media such as Helium, Nitrogen

  18. Positronium formation in dehydrogenated FeTi

    Very efficient positronium formation is observed in hydrogenated/dehydrogenated FeTi after annealing. The effects observed can be interpreted on the basis of defect annealing and mechanisms involved in the self-cleaning of the surface layer of hydrogen sponges. (Auth.)

  19. Dehydrogenation of light alkanes over zeolites

    Narbeshuber, Thomas F.; Brait, Axel; Seshan, Kulathuiyer; Lercher, Johannes A.

    1997-01-01

    The conversion of light paraffins to olefins and the secondary reactions of the unsaturated compounds were investigated on H-ZSM5 and H-Y zeolites between 733 and 823 K. Steady state- and transient response-isotope tracing studies revealed that two mechanisms of dehydrogenation are operative. The ma

  20. Dehydrogenated polycyclic aromatic hydrocarbons and UV bump

    Malloci, G; Cecchi-Pestellini, C; Joblin, C

    2008-01-01

    Recent calculations have shown that the UV bump at about 217.5 nm in the extinction curve can be explained by a complex mixture of PAHs in several charge states. Other studies proposed that the carriers are a restricted population made of neutral and singly-ionised dehydrogenated coronene molecules (C24Hn, n less than 3), in line with models of the hydrogenation state of interstellar PAHs predicting that medium-sized species are highly dehydrogenated. To assess the observational consequences of the latter hypothesis we have undertaken a systematic study of the electronic spectra of dehydrogenated PAHs. We use our first results to see whether such spectra show strong general trends upon dehydrogenation. We used state-of-the-art techniques in the framework of the density functional theory (DFT) to obtain the electronic ground-state geometries, and of the time- dependent DFT to evaluate the electronic excited-state properties. We computed the absorption cross-section of the species C24Hn (n=12,10,8,6,4,2,0) in t...

  1. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    Svane, K. L., E-mail: ksvane@inano.au.dk; Hammer, B., E-mail: hammer@phys.au.dk [Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University (Denmark)

    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.

  2. Disruption of the acyl-coa binding protein gene delays hepatic adaptation to metabolic changes at weaning

    Neess, Ditte; Bloksgaard, Maria; Sørensen, Signe Bek; Marcher, Ann-Britt; Elle, Ida C; Helledie, Torben; Due, Marianne; Pagmantidis, Vasileios; Finsen, Bente; Wilbertz, Johannes; Kruhoeffer, Mogens; Faergeman, Nils; Mandrup, Susanne

    2011-01-01

    , little is known about the in vivo function in mammalian cells. We have generated mice with targeted disruption of ACBP (ACBP-/-). These mice are viable and fertile and develop normally. However, around weaning the ACBP-/- mice go through a crisis with overall weakness, and a slightly decreased growth...... rate. Using microarray analysis we show that the liver of ACBP-/- mice display a significantly delayed adaptation to weaning with late induction of target genes of the sterol regulatory element binding protein (SREBP) family. As a result, hepatic de novo cholesterogenesis is decreased at weaning. The...... delayed induction of SREBP target genes around weaning is caused by a compromised processing and decreased expression of SREBP precursors leading to reduced binding of SREBP to target sites in chromatin. In conclusion, lack of ACBP interferes with the normal metabolic adaptation to weaning and leads to...

  3. Active coke: Carbonaceous materials as catalysts for alkane dehydrogenation

    McGregor, J.; Huang, Z; Parrott, E.; Zeitler, J.; Nguyen, K.; Rawson, J.; Carley, A; Hansen, T.; Tessonnier, J.; Su, D.; Teschner, D; Vass, E.; Knop-Gericke, A.; Schlögl, R.; Gladden, L.

    2010-01-01

    The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes are of significant industrial importance. In this work both carbonaceous materials deposited on VOx/Al2O3 catalysts during reaction and unsupported carbon nanofibres (CNFs) are shown to be active for the dehydrogenation of butane in the absence of gas-phase oxygen. Their activity in these reactions is shown to be dependent upon their structure, with different reaction temperatures yielding structurally dif...

  4. Acceptorless Photocatalytic Dehydrogenation for Alcohol Decarbonylation and Imine Synthesis

    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.

  5. Microchannel apparatus and methods of conducting catalyzed oxidative dehydrogenation

    Tonkovich, Anna Lee (Dublin, OH); Yang, Bin (Columbus, OH); Perry, Steven T. (Galloway, OH); Mazanec, Terry (Solon, OH); Arora, Ravi (New Albany, OH); Daly, Francis P. (Delaware, OH); Long, Richard (New Albany, OH); Yuschak, Thomas D. (Lewis Center, OH); Neagle, Paul W. (Westerville, OH); Glass, Amanda (Galloway, OH)

    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.

  6. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per;

    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...

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

    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. Production of pure hydrogen by ethanol dehydrogenation

    Santacesaria, Elio; Carotenuto, Giuseppina; Tesser, Riccardo; Di Serio, Martino [Naples Univ. (Italy). Dipt. di Chimica

    2011-06-15

    Hydrogen production from bio-ethanol is one of the most promising renewable processes to generate electricity using fuel cells. In this work, we have studied the production of pure hydrogen as a by-product of the ethanol dehydrogenation reaction. This reaction is promoted by copper based catalysts and according to the catalyst used and the operating conditions gives place to acetaldehyde or ethyl acetate as main products. We studied in particular the performance of a commercial copper/copper chromite catalyst, supported on alumina and containing barium chromate as a promoter, which gave the best results. By operating at low pressure and temperature with short residence times, acetaldehyde is more selectively produced, while, by increasing the pressure (10-30 bars), the temperature (200-260 C) and the residence time (about 100 grams hour/mol of ethanol contact time) the selectivity is shifted to the production of ethyl acetate. However, in both cases pure hydrogen is obtained, as a by-product, which can easily be separated. Hydrogen obtained in this way is free of CO and can be directly fed to fuel cells without any inconvenience. In this work, runs performed under different operating conditions have been reported with the scope to select the best conditions. A carrier of H2 6% in N{sub 2} has been used. The studied catalyst has also shown a good thermal stability with respect to sintering phenomena, which generally occur during the dehydrogenation over other copper catalysts. Hydrogen productivities of 8-39 g{sub H2} (Kgcat){sup -1} (h){sup -1} were obtained for the explored temperature range of 200-260 C. Finally the most accredited reaction mechanism is reported and discussed on the basis of the obtained results. (orig.)

  9. Tailored ceria nanoparticles for CO2 mediated ethylbenzene dehydrogenation

    Kovacevic, Marijana

    2016-01-01

    Styrene production via ethylbenzene dehydrogenation (EBDH) is one of the ten most important petrochemical processes. Possessing highly reactive double bond which facilitates self-polymerization and polymerization with other monomers, styrene is the fourth utmost essential bulk monomer at present. Current commercial ethylbenzene dehydrogenation is highly endothermic reaction, thus highly energy demanding. Several alternatives to steam, conventionally used to supply heat have been widely invest...

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

    Bebensee, Fabian; Svane, K.; Bombis, Christian;

    2013-01-01

    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....

  11. Enhanced dehydrogenation of hydrazine bisborane for hydrogen storage

    Li, Leigang [Department of Materials Science, Fudan University, Shanghai 200433 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Tan, Yingbin; Tang, Ziwei; Xia, Guanglin; Yuan, Feng [Department of Materials Science, Fudan University, Shanghai 200433 (China); Li, Qian, E-mail: shuliqian@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Yu, Xuebin, E-mail: yuxuebin@fudan.edu.cn [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2014-02-14

    NiCl{sub 2} and CoCl{sub 2} were adopted to enhance the dehydrogenation of hydrazine bisborane (HBB), respectively, of which NiCl{sub 2} showed better performance. By adding 2.0 mol. % NiCl{sub 2}, the dehydrogenation property of HBB was significantly improved, for example, the impurity of NH{sub 3} during the dehydrogenation of HBB was totally suppressed with more than 13.0 wt. % of pure hydrogen evolved. By Kissinger method, the apparent activation energies of the first step for HBB and Ni-doped HBB were calculated to be 143.2 and 60.7 kJ mol{sup −1}, respectively. DSC result showed that the addition of NiCl{sub 2} did not change the enthalpy change of HBB dehydrogenation. Based on theoretical analysis and literature review, the improved dehydrogenation property of HBB was potentially ascribed to the solid state interaction of Ni{sup 2+} with the electronegative N in the NH{sub 2} group of HBB. - Highlights: • NiCl{sub 2} enhanced dehydrogenation of hydrazine bisborane (HBB) was reported. • By adding NiCl{sub 2}, the desorption rate and the hydrogen purity were improved. • A possible explanation was proposed to understand NiCl{sub 2} enhanced desorption of HBB.

  12. The role of adsorbed hydrogen species in the dehydrogenation and hydrocracking of saturated hydrocarbons on supported metal catalysts

    Babenkova, L. V.; Naidina, I. N.

    1994-07-01

    The role of certain hydrogen absorption complexes in the dehydrogenation and hydrocracking of hydrocarbons on low-percentage one-component, (Pt, Pd/Al2O3) and bimetallic (Pd-Co, Pd-Ce, Pt-Co, Pt-Sn/Al2O3) catalysts is discussed. It is shown that the combination of metals in reduced forms and forms oxidised to different extents on the catalyst surfaces is responsible for their high capacity for the chemisorption of hydrogen, the wide range of its energetic inhomogeneity, and the high activity of the catalysts in the conversion of saturated hydrocarbons. Catalysts containing on the surface mainly sites for the type Hδ- chemisorption are the most active in the dehydrogenation of hydrocarbons, whereas specimens chemisorbing hydrogen mainly in the Hδ+ form are the most active in the hydrockracking of hydrocarbons. It is concluded that the strongly bound atomic hydrogen Hδ+ plays a dual role, since it not only participates directly in the dehydrogenation reaction but also promotes the reduction of the electron-deficient surface centres, which optimises the number of centres for the activation of C-H bonds. The bibliography includes 75 references.

  13. Effect of alloying on carbon formation during ethane dehydrogenation

    Rovik, Anne; Kegnæs, Søren; Dahl, Søren;

    2009-01-01

    The structure sensitivity of different transition metals in the hydrogenolysis, dehydrogenation, and coking reactions during ethane conversion has been investigated. The investigated metals, Ni, Ru, Rh, and Pd, are co-impregnated with Ag onto an inactive MgAl2O4 spinel support and tested in the...... coke during the initial period where after dehydrogenation of ethane is observed. It has previously been predicted in surface science studies that Ag covers the steps of certain transition metals. Here it is documented that the hydrogenolysis and coking reactions are significantly suppressed by co......-Pd/spinel due to an alloy formation of Ag and Pd at these conditions. From our results it can therefore be concluded that hydrogenolysis mainly takes place on the steps and kinks of the transition metal particles, dehydrogenation reactions mainly takes place on the terraces, and coking is significantly reduced...

  14. Oxidative dehydrogenation of isobutane over a titanium pyrophosphate catalyst

    IOAN-CEZAR MARCU

    2005-06-01

    Full Text Available The catalytic properties of titanium pyrophosphate in the oxidative dehydrogenation of isobutane to isobutylene were investigated in the 400 – 550 ºC temperature range. Asignificant change of the product distribution and of the apparent activation energy of the reactionwas observed at about 490 ºC. This phenomenon, already observed in the oxidative dehydrogenation of n-butane, has been interpreted by the existence of two reaction mechanisms depending upon the reaction temperature. Comparison with the n-butane reaction allowed different activation pathways for the activation of alkanes to be proposed. The catalytic properties of TiP2O7 in the oxidative dehydrogenation of isobutane was also compared to those obtained previously with several other pyrophosphates and TiP2O7 was found to be less active and selective for this reaction.

  15. Fe-Catalyzed Cross-Dehydrogenative Coupling Reactions.

    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

  16. Shaking table test study on seismic performance of dehydrogenation fan for nuclear power plants

    Seismic performance of the dehydrogenation fan for nuclear power plants was evaluated based on the shaking table test of earthquake simulation. Dynamic characteristics including the orthogonal tri-axial fundamental frequencies and equivalent damping ratios were measured by the white noise scanning method. Artificial seismic waves were generated corresponding to the floor acceleration response spectra for nuclear power plants. Furthermore, five OBE and one SSE shaking table tests for dehydrogenation fan were performed by using the artificial seismic waves as the seismic inputs along the orthogonal axis simultaneity. Operating function of dehydrogenation fan was monitored and observed during all seismic tests, and performance indexes of dehydrogenation fan were compared before and after seismic tests. The results show that the structural integrity and operating function of the dehydrogenation fan are perfect during all seismic tests; and the performance indexes of the dehydrogenation fan can remain consistent before and after seismic tests; the seismic performance of the dehydrogenation fan can satisfy relevant technical requirements. (authors)

  17. Transfer Methane to Fragrant Hydrocarbon by Direct Catalyzed Dehydrogenation

    2006-01-01

    @@ Sponsored by NSFC,a research project -"Transfer methane to fragrant hydrocarbon by direct catalyzed dehydrogenation",directed by Prof.Xin Bao from Dalian Institute of Chemical Physics of CAS,honored the 2nd class National Science & Technology Award in 2005.

  18. Combustion kinetics of the coke on deactivated dehydrogenation catalysts

    Luo, Sha; He, Songbo; Li, XianRu; Li, Jingqiu; Bi, Wenjun; Sun, Chenglin

    2015-01-01

    The coke combustion kinetics on the deactivated catalysts for long chain paraffin dehydrogenation was studied by the thermogravimetry and differential thermogravimetry (TG–DTG) technique. The amount and H/C mole ratio of the coke were determined by the TG and elemental analysis. And the comprehensiv

  19. Characterizing the infrared spectra of small, neutral, fully dehydrogenated PAHs

    Mackie, C J; Bauschlicher, C W; Cami, J

    2014-01-01

    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$\\mu$m, 5.5$\\mu$m and 10.6$\\mu$m; at longer wavelengths, there is a forest of emission features in the 16--30$\\mu$m range that appears as a structured continuum, but with a clear peak cent...

  20. Propane Dehydrogenation on Metal and Metal Oxide Catalysts

    Sattler, Jesper

    2014-01-01

    In this PhD thesis, the catalytic performance and deactivation of various propane dehydrogenation catalysts is studied. First of all, a literature study is performed, where the three most commonly used formulations, namely Pt-, CrOx- and GaOx-based catalysts are compared in terms of yield relative t

  1. Kinetic modeling of ethylbenzene dehydrogenation over hydrotalcite catalysts

    Atanda, Luqman

    2011-07-01

    Kinetics of ethylbenzene dehydrogenation to styrene was investigated over a series of quaternary mixed oxides of Mg3Fe0.25Me0.25Al0.5 (Me=Co, Mn and Ni) catalysts prepared by calcination of hydrotalcite-like compounds and compared with commercial catalyst. The study was carried out in the absence of steam using a riser simulator at 400, 450, 500 and 550°C for reaction times of 5, 10, 15 and 20s. Mg3Fe0.25Mn0.25Al0.5 afforded the highest ethylbenzene conversion of 19.7% at 550°C. Kinetic parameters for the dehydrogenation process were determined using the catalyst deactivation function based on reactant conversion model. The apparent activation energies for styrene production were found to decrease as follows: E1-Ni>E1-Co>E1-Mn. © 2011 Elsevier B.V.

  2. Carbon mediated catalysis:A review on oxidative dehydrogenation

    De Chen; Anders Holmen; Zhijun Sui; Xinggui Zhou

    2014-01-01

    Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properties of active sites of catalysts through manipulating structures, function-alities and properties of carbon surfaces. The present review focuses on progresses in carbon medi-ated oxidative dehydrogenation reactions of ethylbenzene, propane, and butane. The state-of-the-art of the developments of carbon mediated catalysis is discussed in terms of fundamental studies on adsorption of oxygen and hydrocarbons, reaction mechanism as well as effects of carbon nano-material structures and surface functional groups on the catalytic performance. We highlight the importance and challenges in tuning of the electron density of carbon and oxygen on carbon surfac-es for improving selectivity in oxidative dehydrogenation reactions.

  3. Chromium oxide catalysts in the dehydrogenation of alkanes

    Airaksinen, Sanna

    2005-01-01

    Light alkenes, such as propene and butenes, are important intermediates in the manufacture of fuel components and chemicals. The direct catalytic dehydrogenation of the corresponding alkanes is a selective way to produce these alkenes and is frequently carried out using chromia/alumina catalysts. The aim of this work was to obtain structure–activity information, which could be utilised in the optimisation of this catalytic system. The properties of chromia/alumina catalysts were investigated ...

  4. Membrane catalysis in the dehydrogenation and hydrogen production processes

    Data on the applications of membrane catalysis in the dehydrogenation of organic compounds and hydrogen production are analyzed and generalized. It is shown that the integration of membrane reactors into existing plants is necessary for production of hydrogen of high purity. The steam reforming and oxidative reforming of methane and steam reforming of light alcohols seem to be the most promising processes for hydrogen production in membrane reactors. The bibliography includes 165 references.

  5. Study of the niobium dehydrogenation process by transmission electron microscopy

    The evolution of the micro-structure of Nb-H, during the dehydrogenation process through thermal treatment, has been studied by Transmission Electron Microscopy. The results are used in order to interpret the variation of the line resolution of Electron Channeling Pattern (ECP) of Nb-H as a function of isochronous annealing temperature. It is concluded that the improvement of the ECP line resolution is enhanced of β hydrate in Nb. (Author)

  6. DISTINCT TRANSCRIPTIONAL REGULATION OF LONG-CHAIN ACYL-COA SYNTHETASE ISOFORMS AND CYTOSOLIC THIOESTERASE 1 IN THE RODENT HEART BY FATTY ACIDS AND INSULIN

    The molecular mechanism(s) responsible for channeling long-chain fatty acids (LCFAs) into oxidative versus nonoxidative pathways is (are) poorly understood in the heart. Intracellular LCFAs are converted to long-chain fatty acyl-CoAs (LCFA-CoAs) by a family of long-chain acyl-CoA synthetases (ACSLs)...

  7. Increased long chain acyl-Coa synthetase activity and fatty acid import is linked to membrane synthesis for development of picornavirus replication organelles.

    Jules A Nchoutmboube

    Full Text Available All positive strand (+RNA viruses of eukaryotes replicate their genomes in association with membranes. The mechanisms of membrane remodeling in infected cells represent attractive targets for designing future therapeutics, but our understanding of this process is very limited. Elements of autophagy and/or the secretory pathway were proposed to be hijacked for building of picornavirus replication organelles. However, even closely related viruses differ significantly in their requirements for components of these pathways. We demonstrate here that infection with diverse picornaviruses rapidly activates import of long chain fatty acids. While in non-infected cells the imported fatty acids are channeled to lipid droplets, in infected cells the synthesis of neutral lipids is shut down and the fatty acids are utilized in highly up-regulated phosphatidylcholine synthesis. Thus the replication organelles are likely built from de novo synthesized membrane material, rather than from the remodeled pre-existing membranes. We show that activation of fatty acid import is linked to the up-regulation of cellular long chain acyl-CoA synthetase activity and identify the long chain acyl-CoA syntheatse3 (Acsl3 as a novel host factor required for polio replication. Poliovirus protein 2A is required to trigger the activation of import of fatty acids independent of its protease activity. Shift in fatty acid import preferences by infected cells results in synthesis of phosphatidylcholines different from those in uninfected cells, arguing that the viral replication organelles possess unique properties compared to the pre-existing membranes. Our data show how poliovirus can change the overall cellular membrane homeostasis by targeting one critical process. They explain earlier observations of increased phospholipid synthesis in infected cells and suggest a simple model of the structural development of the membranous scaffold of replication complexes of picorna-like viruses, that may be relevant for other (+RNA viruses as well.

  8. Effect of hydrogen combustion reaction on the dehydrogenation of ethane in a fixed-bed catalytic membrane reactor

    Masoud Hasany; Mohammad Malakootikhah; Vahid Rahmanian; Soheila Yaghmaei

    2015-01-01

    A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction, removal of produced hydrogen by the membrane shifts the thermodynamic equilibrium to ethylene production. For further displacement of the dehydrogenation reaction, oxidative dehydrogenation method has been used. Since ethane dehydrogenation is an endothermic reaction, the energy produced by the oxidative dehydrogena-tion method is consumed by the dehydrogenation reaction. The results show that the oxidative dehydrogenation method generated a substantial improvement in the reactor performance in terms of high conversions and significant energy saving. It was also established that the sweep gas velocity in the shell side of the reactor is one of the most important factors in the effectiveness of the reactor.

  9. Dehydrogenation of Methylcyclohexane: Parametric Sensitivity of the Power Law Kinetics

    Arthur A. Garforth; David L. Cresswell; Usman, Muhammad R.

    2013-01-01

    For heterogeneous catalytic reactions, the empirical power law model is a valuable tool that explains variation in the kinetic behavior with changes in operating conditions, and therefore aids in the development of an appropriate and robust kinetic model. In the present work, experiments are performed on 1.0 wt% Pt/Al2O3 catalyst over a wide range of experimental conditions and parametric sensitivity of the power law model to the kinetics of the dehydrogenation of methylcyclohexane is studied...

  10. Rhodium-technetium catalysts in dehydrogenation of cyclohexane

    Catalytic properties of Rh-Tc/support (γ-Al2O3, SiO2 or MgO) system in dehydrogenation of cyclohexane were studied. A nonadditive increase in catalytic activity of bimetallic catalysts in comparison with monometallic catalysts has been established. Diffuse reflectance spectra have shown the presence of ionic forms of the metals in bimetallic catalysts. From the comparison of catalytic and optical properties a conclusion was drawn about the nature of synergism observed, which was accounted for by the formation of RhxTcy clusters. 6 refs.; 5 figs.; 1 tab

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

    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

  12. Influence of precursor a-Si:H dehydrogenation on the aluminum induced crystallization process

    Duan, Weiyuan, E-mail: weiyuan.duan0924@mail.sim.ac.cn [New Energy Technology Center, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 235 Chengbei Road, Jiading, Shanghai 200050 (China); University of the Chinese Academy of Sciences, Beijing 100039 (China); Qiu, Yu, E-mail: yuqiu@mail.sim.ac.cn [New Energy Technology Center, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 235 Chengbei Road, Jiading, Shanghai 200050 (China); Zhang, Liping; Yu, Jian; Bian, Jiantao; Liu, Zhengxin [New Energy Technology Center, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 235 Chengbei Road, Jiading, Shanghai 200050 (China)

    2014-07-01

    Polycrystalline silicon (poly-Si) thin film grown on low cost substrates such as glass at low temperature is an attractive material for cost-effective solar cells. This work studied the influence of dehydrogenation of a-Si:H precursor on the crystallization behavior by aluminum induced crystallization (AIC) process below the eutectic temperature of 577 °C. The a-Si:H films were deposited by PECVD and aluminum was evaporated in a vacuum evaporation equipment, respectively. Some of the a-Si:H thin films were dehydrogenated in nitrogen atmosphere before aluminum evaporation. It was found that hydrogen content in a-Si:H drops to a stable value after annealing at 480 °C for 1 h. Micro-Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy measurements were used to investigate the structural characteristics of the a-Si:H and the prepared poly-Si thin films. Our results show that although the dehydrogenation increases AIC temperature and reduces AIC rate, it can improve microstructural quality of poly-Si thin films, leading to less tensile stress, higher crystallinity, smoother and more conformal surface morphology. - Highlights: • The influence of a-Si:H precursor dehydrogenation on AIC process was studied. • Dehydrogenation can improve microstructural quality of poly-Si thin films. • Smoother surface morphology can be observed on dehydrogenation samples after AIC. • The dehydrogenation process is necessary for fabricating high quality solar cells.

  13. Dehydrogenation process of AlH{sub 3} observed by TEM

    Nakagawa, Yuki, E-mail: y-nakagawa@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-8278 (Japan); Isobe, Shigehito [Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-8278 (Japan); Creative Research Institution, Hokkaido University, N-21, W-10, Sapporo 001-0021 (Japan); Wang, Yongming; Hashimoto, Naoyuki; Ohnuki, Somei [Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-8278 (Japan); Zeng, Liang; Liu, Shusheng; Ichikawa, Takayuki; Kojima, Yoshitsugu [Institute for Advanced Materials Research, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)

    2013-12-15

    Highlights: ► The initial shape of α-AlH{sub 3} particle is cubic and that of γ-AlH{sub 3} is rod-shaped. ► Dehydrogenation kinetics does not depend on Al{sub 2}O{sub 3} thickness in the 4.6–7.8 nm range. ► Milling effect on dehydrogenation kinetics will be larger than doping effect. -- Abstract: Dehydrogenation processes of α- and γ-AlH{sub 3} were investigated by in situ transmission electron microscopy observations. The relationship between Al{sub 2}O{sub 3} thickness and dehydrogenation kinetics was also clarified. The initial shape of α-AlH{sub 3} particle was cubic and that of γ-AlH{sub 3} particle was rod-shaped. The process of γ-AlH{sub 3} was quite similar with α-AlH{sub 3}. The precipitation and growth of Al was observed in both processes. The dehydrogenation kinetics did not depend on Al{sub 2}O{sub 3} thickness. It was found that milling effect on the dehydrogenation kinetics was larger than doping effect. The dehydrogenation process was discussed in terms of both microscopic and kinetic studies.

  14. Propane Dehydrogenation over a Commercial Pt-Sn/Al2O3 Catalyst for Isobutane Dehydrogenation: Optimization of Reaction Conditions

    Farnaz Tahriri Zangeneh; Saeed Sahebdelfar; Mohsen Bahmani

    2013-01-01

    The applicability of a commercial Pt-Sn/Al2O3 isobutane dehydrogenation catalyst in dehydrogenation of propane was studied.Catalyst performance tests were carried out in a fixed-bed quartz reactor under different operating conditions.Generally,as the factors improving propane conversion decrease the propylene selectivity,the optimal operating condition to maximize propylene yield is expected.The optimal condition was obtained by the experimental design method.The investigated parameters were temperature,hydrogen/hydrocarbon (H2/HC) ratio and space velocity,being changed in three levels.Constrains such as the susceptibility of the catalyst components to sintering or phase transformation were also taken into account.Activity,selectivity and stability of the catalyst were considered as the measured response factors,while the space-time-yield (STY) was considered as the variable to be optimized due to its commercial interest.A STY of 16 mol·kg-1·h-1 was achieved under the optimal conditions of T=620 ℃,H2/HC =0.6 and,weight hourly space velocity (WHSV) =2.2 h-1.Single carbon-carbon bond rupture was found to be the main route for the formation of lower hydrocarbon byproducts.

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

    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.

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

    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

  17. Kinetics with deactivation of methylcyclohexane dehydrogenation for hydrogen energy storage

    Maria, G.; Marin, A.; Wyss, C.; Mueller, S.; Newson, E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The methylcyclohexane dehydrogenation step to recycle toluene and release hydrogen is being studied as part of a hydrogen energy storage project. The reaction is performed catalytically in a fixed bed reactor, and the efficiency of this step significantly determines overall system economics. The fresh catalyst kinetics and the deactivation of the catalyst by coke play an important role in the process analysis. The main reaction kinetics were determined from isothermal experiments using a parameter sensitivity analysis for model discrimination. An activation energy for the main reaction of 220{+-}11 kJ/mol was obtained from a two-parameter model. From non-isothermal deactivation in PC-controlled integral reactors, an activation energy for deactivation of 160 kJ/mol was estimated. A model for catalyst coke content of 3-17 weight% was compared with experimental data. (author) 3 figs., 6 refs.

  18. Thin Film Models of Magnesium Orthovanadate Catalysts for Oxidative Dehydrogenation

    SAULT,ALLEN G.; MUDD,JASON E.; MILLER,JAMES E.; RUFFNER,JUDITH A.; RODRIGUEZ,MARK A.; TISSOT JR.,RALPH G.

    2001-03-01

    Magnesium vanadates are potentially important catalytic materials for the conversion of alkanes to alkenes via oxidative dehydrogenation. However, little is known about the active sites at which the catalytic reactions take place. It may be possible to obtain a significant increase in the catalytic efficiency if the effects of certain material properties on the surface reactions could be quantified and optimized through the use of appropriate preparation techniques. Given that surface reactivity is often dependent upon surface structure and that the atomic level structure of the active sites in these catalysts is virtually unknown, we desire thin film samples consisting of a single magnesium vanadate phase and a well defined crystallographic orientation in order to reduce complexity and simplify the study of active sites. This report describes the use of reactive RF sputter deposition to fabricate very highly oriented, stoichiometric Mg{sub 3}(VO{sub 4}){sub 2} thin films, and subsequent studies of the reactivity of these films under reaction conditions typically found during oxidative dehydrogenation. We demonstrate that the synthesis methods employed do in fact result in stoichiometric films with the desired crystallographic orientation, and that the chemical behavior of the films closely approximates that of bulk, high surface area Mg{sub 3}(VO{sub 4}){sub 2} powders. We further use these films to demonstrate the effects of oxygen vacancies on chemical behavior, demonstrate that surface composition can vary significantly under reaction conditions, and obtain the first evidence for structure sensitivity in Mg{sub 3}(VO{sub 4}){sub 2} catalysts.

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

    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

  20. In situ spectroscopic investigation of oxidative dehydrogenation and disproportionation of benzyl alcohol

    Nowicka, E.; HOFMANN, J.P.; Parker, S. F.; Sankar, M.; Lari, G.M.; Kondrat, S.A.; Knight, D. W.; Bethell, D; Weckhuysen, B.M.; G. J. Hutchings

    2013-01-01

    In the solvent free oxidation of benzyl alcohol, using supported gold–palladium nanoalloys, toluene is often one of major by-products and it is formed by the disproportionation of benzyl alcohol. Gold–palladium catalysts on acidic supports promote both the disproportionation of benzyl alcohol and oxidative dehydrogenation to form benzaldehyde. Basic supports completely switch off disproportionation and the gold–palladium nanoparticles catalyse the oxidative dehydrogenation reaction exclusivel...

  1. Characterization and Dehydrogenation Activity of SBA-15 and HMS Supported Chromia Catalysts

    YUE,Hong-Yong(乐洪咏); ZHENG,Bo(郑波); YUE,Ying-Hong(乐英红); ZHANG,Xue-Zheng(张雪峥); HUA,Wei-Ming(华伟明); GAO,Zi(高滋)

    2002-01-01

    SBA-15 and HMS supported chromia catalysts were prepared and characterized. Chromia is highly dispersed on the mesoporous supports when its loading is ≤7 wt%. The supported catalysts display high activity, selectivity and stability for dehydrogenation of ethyibenzene and propane. ESR measurement of the catalysts before and after reaction shows that the active species for dehydrogenation reaction might be Cr3 + species on the catalyst surface, and the activity of the catalyst is probably correlated with the dispersion of Cr3+ species.

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

    Sun, Pingping; Siddiqi, Georges; Vining, William C.; Chi, Miaofang; Bell, Alexis T. (UCB); (ORNL)

    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.

  3. Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

    Roura Grabulosa, Pere; Farjas Silva, Jordi; Rath, Chandana; Serra-Miralles, J.; Bertrán Serra, Enric; Roca I Cabarrocas, Pere

    2006-01-01

    Differential scanning calorimetry (DSC) was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis (EGA) has led to the identification of four dehydrogenation processes arising from polymeric chains (A), SiH groups at the surfaces of internal voids (A'), SiH groups at interfaces (B), and in the b...

  4. Surface-Modified Carbon Nanotubes Catalyze Oxidative Dehydrogenation of n-Butane

    J. Zhang; Liu, X; Blume, R.; Zhang, A; Schlögl, R.; Su, D.

    2008-01-01

    Butenes and butadiene, which are useful intermediates for the synthesis of polymers and other compounds, are synthesized traditionally by oxidative dehydrogenation (ODH) of n-butane over complex metal oxides. Such catalysts require high O2/butane ratios to maintain the activity, which leads to unwanted product oxidation. We show that carbon nanotubes with modified surface functionality efficiently catalyze the oxidative dehydrogenation of n-butane to butenes, especially butadiene. For low O2/...

  5. Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air

    Poreddy, Raju; Engelbrekt, Christian; Riisager, Anders

    2015-01-01

    The oxidative dehydrogenation of alcohols to carbonyl compounds was studied using CuO nanoparticle catalysts prepared by solution synthesis in buffered media. CuO nanoparticles synthesized in N-cyclohexyl- 3-aminopropanesulfonic acid buffer showed high catalytic activity for the oxidation of...... dehydrogenation of benzyl alcohols to be proposed. The use of CuO as an inexpensive and efficient heterogeneous catalyst under aerobic conditions provides a new noble metal-free and green reaction protocol for carbonyl compound synthesis....

  6. Dehydrogenation mechanism of LiBH{sub 4} by Poly(methyl methacrylate)

    Huang, Jianmei [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Yan, Yurong [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); Ouyang, Liuzhang, E-mail: meouyang@scut.edu.cn [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Key Laboratory for Fuel Cell Technology in Guangdong Province, South China University of Technology, Guangzhou 510641 (China); Wang, Hui [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Zhu, Min, E-mail: memzhu@scut.edu.cn [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China)

    2015-10-05

    Highlights: • LiBH{sub 4} is amorphous after modified with PMMA. • Dehydrogenation temperature of LiBH{sub 4} decreases by 120 °C after modifying with PMMA. • The LiBH{sub 4}@PMMA composite releases 10 wt.% hydrogen at 360 °C within 1 h. • C=O group of PMMA weakens the B−H bonds to lower dehydrogenation temperature. - Abstract: We investigated the dehydrogenation properties and mechanism of Poly(methyl methacrylate) (PMMA) confined LiBH{sub 4}. Thermal stability of LiBH{sub 4} was reduced by PMMA, with a decrease in dehydrogenation temperature by 120 °C. At 360 °C, the composite showed fast dehydrogenation kinetics with 10 wt.% of hydrogen released within 1 h. The improved dehydrogenation performance was mainly attributed to the reaction between LiBH{sub 4} and PMMA forming Li{sub 3}BO{sub 3} as a final product. Furthermore, the presence of electrostatic interaction between B atom of LiBH{sub 4} and O atom in the carbonyl group of PMMA may weaken the B−H bonding of [BH{sub 4}]{sup −} and lower the hydrogen desorption temperature.

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

    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.

  8. Dehydrogenation mechanism of LiBH4 by Poly(methyl methacrylate)

    Highlights: • LiBH4 is amorphous after modified with PMMA. • Dehydrogenation temperature of LiBH4 decreases by 120 °C after modifying with PMMA. • The LiBH4@PMMA composite releases 10 wt.% hydrogen at 360 °C within 1 h. • C=O group of PMMA weakens the B−H bonds to lower dehydrogenation temperature. - Abstract: We investigated the dehydrogenation properties and mechanism of Poly(methyl methacrylate) (PMMA) confined LiBH4. Thermal stability of LiBH4 was reduced by PMMA, with a decrease in dehydrogenation temperature by 120 °C. At 360 °C, the composite showed fast dehydrogenation kinetics with 10 wt.% of hydrogen released within 1 h. The improved dehydrogenation performance was mainly attributed to the reaction between LiBH4 and PMMA forming Li3BO3 as a final product. Furthermore, the presence of electrostatic interaction between B atom of LiBH4 and O atom in the carbonyl group of PMMA may weaken the B−H bonding of [BH4]− and lower the hydrogen desorption temperature

  9. Iron deficiency

    Schou, Morten; Bosselmann, Helle; Gaborit, Freja;

    2015-01-01

    BACKGROUND: Both iron deficiency (ID) and cardiovascular biomarkers are associated with a poor outcome in heart failure (HF). The relationship between different cardiovascular biomarkers and ID is unknown, and the true prevalence of ID in an outpatient HF clinic is probably overlooked. OBJECTIVES...... understand iron metabolism in elderly HF patients....

  10. VLCAD deficiency

    Boneh, A; Andresen, B S; Gregersen, N; Ibrahim, M; Tzanakos, N; Peters, H; Yaplito-Lee, J; Pitt, J J

    2006-01-01

    We diagnosed six newborn babies with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) through newborn screening in three years in Victoria (prevalence rate: 1:31,500). We identified seven known and two new mutations in our patients (2/6 homozygotes; 4/6 compound heterozygotes). Blood sa...

  11. Aerobic Dehydrogenation of Cyclohexanone to Cyclohexenone Catalyzed by Pd(DMSO)2(TFA)2: Evidence for Ligand-Controlled Chemoselectivity

    Diao, Tianning; Pun, Doris; Stahl, Shannon S.

    2013-01-01

    The dehydrogenation of cyclohexanones affords cyclohexenones or phenols via removal of one or two equivalents of H2, respectively. We recently reported several PdII catalyst systems that effect aerobic dehydrogenation of cyclohexanones with different product selectivities. Pd(DMSO)2(TFA)2 is unique in its high chemoselectivity for the conversion of cyclohexanones to cyclohexenones, without promoting subsequent dehydrogenation of cyclohexenones to phenols. Kinetic and mechanistic studies of th...

  12. Process for alkane group dehydrogenation with organometallic catalyst

    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.

  13. Ruthenium(II)-PNN pincer complex catalyzed dehydrogenation of benzyl alcohol to ester: A DFT study

    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.

  14. A New Homogeneous Catalyst for the Dehydrogenation of Dimethylamine Borane Starting with Ruthenium(III Acetylacetonate

    Ebru Ünel Barın

    2015-06-01

    Full Text Available The catalytic activity of ruthenium(III acetylacetonate was investigated for the first time in the dehydrogenation of dimethylamine borane. During catalytic reaction, a new ruthenium(II species is formed in situ from the reduction of ruthenium(III and characterized using UV-Visible, Fourier transform infrared (FTIR, 1H NMR, and mass spectroscopy. The most likely structure suggested for the ruthenium(II species is mer-[Ru(N2Me43(acacH]. Mercury poisoning experiment indicates that the catalytic dehydrogenation of dimethylamine-borane is homogeneous catalysis. The kinetics of the catalytic dehydrogenation of dimethylamine borane starting with Ru(acac3 were studied depending on the catalyst concentration, substrate concentration and temperature. The hydrogen generation was found to be first-order with respect to catalyst concentration and zero-order regarding the substrate concentration. Evaluation of the kinetic data provides the activation parameters for the dehydrogenation reaction: the activation energy Ea = 85 ± 2 kJ·mol−1, the enthalpy of activation ∆H# = 82 ± 2 kJ·mol−1 and the entropy of activation; ∆S# = −85 ± 5 J·mol−1·K−1. The ruthenium(II catalyst formed from the reduction of ruthenium(III acetylacetonate provides 1700 turnovers over 100 hours in hydrogen generation from the dehydrogenation of dimethylamine borane before deactivation at 60 °C.

  15. Oxidative dehydrogenation of ethane to ethylene using vanadia based catalysts

    Qiao, Ailing; Kalevaru, V.N. [Univ. Rostock e.V., Rostock (Germany). Leibniz-Inst. fuer Katalyse; Humar, A.S.; Lingaiah, N.; Sai Prasad, P.S.; Martin, A. [Indian Institute of Chemical Technology, Hyderabad (India). Inorganic and Physical Chemistry Div.

    2011-07-01

    In this work, we describe the application of V{sub 2}O{sub 5}/Nb{sub 2}O{sub 5} catalysts for the oxidative dehydrogenation (ODH) of ethane to ethylene. A series of Nb{sub 2}O{sub 5} supported V{sub 2}O{sub 5} catalysts were prepared by impregnation technique. NH{sub 4}VO{sub 3} was used as a precursor for V{sub 2}O{sub 5}. The content of V{sub 2}O{sub 5} is varied in the range from 5 to 20 wt%. Catalytic tests were carried out in a fixed bed quartz reactor in the temperature range from 500 to 600 C. The conversion of ethane has been increased from ca. 20 to 35 % with increase in temperature from 500 to 600 C, while the yield of ethylene is increased from about 5 to 12 % only. CO and CO{sub 2} are the only major by-products of the reaction. The activity tests were performed at low O{sub 2} concentration in the feed and hence low conversions were achieved. Furthermore, the conversion of ethane is found to increase continuously with increase in V{sub 2}O{sub 5} loading while the yield of C{sub 2}H{sub 4} increased only up to 10wt% V{sub 2}O{sub 5} and then decreased. Results revealed that the catalytic activity and selectivity is found to depend on the V{sub 2}O{sub 5} loading. Among all, 10wt% V{sub 2}O{sub 5}/Nb{sub 2}O{sub 5} catalyst has displayed the superior performance. (orig.)

  16. Highly Ordered Mesoporous Metal Oxides as Catalysts for Dehydrogenation of Cyclohexanol

    Cyclohexanone is important intermediate for the manufacture of caprolactam which is monomer of nylron. Cyclohexanone is generally produced by dehydrogenation reaction of cyclohexanol. In this study, highly mesoporous metal oxides such as meso-WO3, meso-TiO2, meso-Fe2O3, meso-CuO, meso-SnO2 and meso-NiO were synthesized using mesoporous silica KIT-6 as a hard template via nano-replication method for dehydrogenation of cyclohexanol. The overall conversion of cyclohexanol followed a general order: meso-WO3 >> meso-Fe2O3 > meso-SnO2 > meso-TiO2 > meso-NiO > meso-CuO. In particular, meso-WO3 significantly showed higher activity than the other mesoporous metal oxides. Therefore, the meso-WO3 has wide range of application possibilities for dehydrogenation of cyclohexanol

  17. Dehydrogenation of light alkanes over rhenium catalysts on conventional and mesoporous MFI supports

    Rovik, Anne Krogh; Hagen, Anke; Schmidt, I.;

    2006-01-01

    Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing amounts of ethene were produced with time on...... stream due to deactivation of the catalyst. We show that by use of rhenium impregnated MFI supports with very few or no acidic sites (Si/Al > 500), highly selective ethane dehydrogenation catalysts are obtained with ethene selectivities of 98%. By use of mesoporous MFI supports (Si/Al > 500) the lifetime...... of the catalyst appears to be slightly improved compared to conventional MFI crystals. The beneficial effect of a mesoporous MFI support is convincingly demonstrated in propane dehydrogenation, where both conversion and selectivities on the mesoporous MFI (Si/Al > 500) impregnated with Re are...

  18. Theoretical investigation of the mechanism of tritiated methane dehydrogenation reaction using nickel-based catalysts

    Dong, Liang; Li, Jiamao; Deng, Bing; Yang, Yong; Wang, Heyi [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Weiyi [School of Physics and Chemistry, Xihua University, Chengdu 610065 (China); Li, Shuo, E-mail: lishuo@cqut.edu.cn [School of Chemical Engineering, Chongqing University of Technology, Chongqing 400054 (China); Tan, Zhaoyi, E-mail: tanzhaoyi@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2015-06-15

    Graphical abstract: - Highlights: • Four-step dehydrogenation of CT{sub 4} catalyzed by Ni to form Ni–C by releasing T{sub 2}. • The process of Ni + CT{sub 4} → NiCT{sub 2} + T{sub 2} is more achievable than that of NiCT{sub 2} → NiC + T{sub 2}. • TNiCT → T{sub 2}NiC step is the RDS with the rate constant of k = 2.8 × 10{sup 13} exp(−313,136/RT). • The hydrogen isotope effect value of k{sub H}/k{sub T} is 2.94, and k{sub D}/k{sub T} is 1.39. • CH{sub 4} and CD{sub 4} dehydrogenations are likely to occur, accompanied by the CT{sub 4} cracking. - Abstract: The mechanism of tritiated methane dehydrogenation reaction catalyzed by nickel-based catalyst was investigated in detail by density functional theory (DFT) at the B3LYP/[6-311++G(d, p), SDD] level. The computational results indicated that the dehydrogenation of tritiated methane is endothermic. The decomposition of tritiated methane catalyzed by Ni to form Ni-based carbon (Ni–C) after a four-step dehydrogenation companied with releasing tritium. After the first and second dehydrogenation steps, Ni + CT{sub 4} formed NiCT{sub 2}. After the third and fourth dehydrogenation steps, NiCT{sub 2} formed NiC. The first and second steps of dehydrogenation occurred on both the singlet and triplet states, and the lowest energy route is Ni + CT{sub 4} → {sup 1}COM → {sup 1}TS1 → {sup 3}IM1 → {sup 3}TS2 → {sup 3}IM2. The third and fourth steps of dehydrogenation occurred on both the singlet and quintet states, and the minimum energy reaction pathway appeared to be IM3 → {sup 1}TS4 → {sup 5}IM4 → {sup 5}TS5 → {sup 5}IM5 → {sup 5}pro + T{sub 2}. The fourth step of dehydrogenation TNiCT → T{sub 2}NiC was the rate-determining step of the entire reaction with the rate constant of k{sub 2} = 2.8 × 10{sup 13} exp(−313,136/RT) (in cm{sup 3} mol{sup −1} s{sup −1}), and its activation energy barrier was calculated to be 51.8 kcal/mol. The Ni-catalyzed CH{sub 4} and CD{sub 4} cracking

  19. Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

    Olsen, Esben Paul Krogh; Singh, Thishana; Harris, Pernille;

    2015-01-01

    The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving...... dehydrogenation of the alcohol and decarbonylation of the resulting aldehyde. The square planar complex IrCl(CO)(rac-BINAP) was isolated from the reaction between [Ir(cod)Cl](2), rac-BINAP, and benzyl alcohol. The complex was catalytically active and applied in the study of the individual steps in the catalytic...... cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction, and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH2Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment...

  20. Iridium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

    Olsen, Esben Paul Krogh; Madsen, Robert

    2012-01-01

    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)2Cl]2 (coe=cyclooct......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)2Cl]2 (coe......, 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....

  1. Hydrogenation/Dehydrogenation Performances of the MgH2-WS2 Composites

    WANG Jiasheng; ZHANG Wei; CHENG Ying; KE Dandan; HAN Shumin

    2015-01-01

    The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH2-WS2 composites were investigated. The TPD (Temperature-Programmed-Desorption) curves showed that the onset dehydrogenation temperature of the MgH2 + 20wt% WS2 composite was 615 K, 58 K lower than that of the pristine MgH2. The kinetic measurements showed that within 21 min, the MgH2 + 20wt% WS2 composite could absorb 2.818wt% at 423 K, and release 4.244 wt% of hydrogen at 623 K, while the hydriding/dehydriding capacity of MgH2 reached only 0.979wt% and 2.319wt% respectively under identical conditions. The improvement of hydrogenation/dehydrogenation performances for the composite was attributed to the co-catalytic effect between the new phases W and MgS which formed during the ball-milling process.

  2. Manipulation of the electronic structure by reversible dehydrogenation of tetra(p-hydroxyphenyl)porphyrin molecules

    Smykalla, Lars; Mende, Carola; Rüffer, Tobias; Lang, Heinrich; Hietschold, Michael

    2014-01-01

    The controlled and reversible interconversion between the free-base and the doubly dehydrogenated form of a 5,10,15,20-tetra(p-hydroxyphenyl)porphyrin molecule in an ordered array is demonstrated. This is achieved through voltage pulses by hydrogen transfer between the center of the porphyrin and the tip of a scanning tunneling microscope (STM). The local dehydrogenation leads to significant shifts in the energetic positions of the molecular orbitals. Density functional theory (DFT) calculations corroborate our conclusions and allow to gain more insight into the different energy level alignment before and after dehydrogenation. Due to the different conductance at a given voltage a clear distinction of both molecular species is possible, which also enables the application as a single-molecular switch.

  3. Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals

    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.

  4. Study on the dehydrogenation kinetics and thermodynamics of Ca(BH4)2

    Ca(BH4)2 is a promising hydrogen storage material due to its high gravimetric hydrogen density of 11.5 wt%. In this work, the dehydrogenation kinetics and thermodynamics of Ca(BH4)2 were systematically investigated by differential thermal analysis (DTA), thermal analysis mass spectrometry (TA/MS), temperature-programmed desorption (TPD), X-ray diffraction (XRD) and pressure, composition, and temperature (PCT) measurements. DTA, TA/MS, TPD and XRD results indicate that the dehydrogenation process of Ca(BH4)2 is a two-step reaction. The dehydriding reaction of Ca(BH4)2 starts at approximately 320 oC, and about 9.6% of hydrogen is desorbed through the two-step reaction. The apparent activation energy (Ea) of about 225.37 and 280.51 kJ/mol for the first-step and second-step dehydrogenation, respectively, were determined by Kissinger's method. The activation energy for the first-step dehydrogenation was further confirmed by the Arrhenius equation. As a result of in-depth kinetic investigations, a geometrical contraction-controlled kinetic mechanism has been identified for the first-step dehydrogenation by analyzing isothermal hydrogen desorption curves with a linear plot method. Finally, the thermodynamic parameters for the dehydrogenation are estimated based on the results of the PCT measurements: enthalpy of reaction ΔH = 87 kJ/mol-H2, and entropy of reaction ΔS = 158 J/K mol-H2. The relatively high activation energy and change in enthalpy indicate that a kinetic and thermodynamic barrier needs to be overcome for Ca(BH4)2 to be suitable as a hydrogen storage material for mobile applications.

  5. Mechanistic insights into the oxidative dehydrogenation of amines to nitriles in continuous flow

    Corker, Emily C.; Ruiz-Martínez, Javier; Riisager, Anders;

    2015-01-01

    The oxidative dehydrogenation of various aliphatic amines to their corresponding nitrile compounds using RuO2/Al2O3 catalysts in air was successfully applied to a continuous flow reaction. Conversions of amines (up to >99%) and yields of nitriles (up to 77%) varied depending on reaction conditions...... and the amine utilised. The presence of water was found to be important for the activity and stability of the RuO2/Al2O3 catalyst. The Hammett relationship and in situ infrared spectroscopy were applied to divulge details about the catalytic mechanism of the oxidative dehydrogenation of amines over Ru...

  6. Dehydrogenative Aromatization of Saturated Aromatic Compounds by Graphite Oxide and Molecular Sieves

    张轩; 徐亮; 王希涛; 马宁; 孙菲菲

    2012-01-01

    Graphite oxide (GO) has attracted much attention of material and catalysis chemists recently. Here we describe a combination of GO and molecular sieves for the dehydrogenative aromatization. GO prepared through improved Hummers method showed high oxidative activity in this reaction. Partially or fully saturated aromatic compounds were converted to their corresponding dehydrogenated aromatic products with fair to excellent conversions and selectivities. As both GO and molecular sieves are easily available, cheap, lowly toxic and have good tolerance to various functional groups, this reaction provides a facile approach toward aromatic compounds from their saturated precursors

  7. Genetics Home Reference: isolated growth hormone deficiency

    ... deficiency dwarfism, pituitary growth hormone deficiency dwarfism isolated GH deficiency isolated HGH deficiency isolated human growth hormone deficiency isolated somatotropin deficiency isolated somatotropin deficiency disorder ...

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

    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.

  9. Study of vanadium based mesoporous silicas for oxidative dehydrogenation of propane and n-butane

    Bulánek, R.; Kalužová, A.; Setnička, M.; Zukal, Arnošt; Čičmanec, P.; Mayerová, Jana

    2012-01-01

    Roč. 179, č. 1 (2012), s. 149-158. ISSN 0920-5861 R&D Projects: GA ČR GAP106/10/0196 Institutional research plan: CEZ:AV0Z40400503 Keywords : vanadium * oxidative dehydrogenation * mesoporous silicas Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.980, year: 2012

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

    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

  11. Synthesis and characterization of conventional and mesoporous Ga-MFI for ethane dehydrogenation

    Leth, Karen Thrane; Rovik, Anne Krogh; Holm, Martin Spangsberg;

    2008-01-01

    difference being the morphology of the crystals. The catalytic properties of the samples were tested in ethane dehydrogenation at 823 K and at atmospheric pressure. The two Ga-MFI samples differ greatly in conversion of ethane, as a result of their difference in porosity, and it is found that the conversion...

  12. Structure of alumina supported vanadia catalysts for oxidative dehydrogenation of propane prepared by flame spray pyrolysis

    Høj, Martin; Jensen, Anker Degn; Grunwaldt, Jan-Dierk

    2013-01-01

    A series of five vanadia on alumina catalysts for oxidative dehydrogenation of propane to propene were synthesized by flame spray pyrolysis (FSP) using vanadium(III)acetylacetonate and aluminium(III)acetylacetonate dissolved in toluene as precursors. The vanadium loading was 2, 3, 5, 7.5 and 10wt...

  13. Simultaneous dehydrogenation of organic compounds and hydrogen removal by hydride forming alloys

    Appelman, W.J.T.M.; Kuczynski, M.; Versteeg, G.F.

    1992-01-01

    The applicability of hydrogen-absorbing metals in dehydrogenation reactions was investigated. Based on thermodynamic considerations, operating ranges were defined within which an increase of the reactant conversion can he achieved owing to an in situ hydrogen removal by the alloy. Low plateau pressu

  14. Amino olefin nickel(I) and nickel(0) complexes as dehydrogenation catalysts for amine boranes

    M. Vogt; B. de Bruin; H. Berke; M. Trincado; H. Grützmacher

    2011-01-01

    A rare paramagnetic organometallic nickel(I) olefin complex can be isolated using the ligand bis(5H-dibenzo[a,d]cyclohepten-5-yl)amine. This complex and related nickel(0) hydride complexes show very high catalytic activity in the dehydrogenation of dimethylamino borane with release of one equivalent

  15. Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

    2006-01-01

    Dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift (RWGS), was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process.The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3.Coke deposition and deep reduction of active components are the major causes of catalyst deactivation.CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

  16. Oxidative dehydrogenation of ethylbenzene to styrene over alumina : effect of calcination

    Nederlof, Christian; Zarubina, Valeriya; Melian-Cabrera, Ignacio; Heeres, Hero Jan (Eric); Kapteijn, Freek; Makkee, Michiel

    2013-01-01

    Commercially available gamma-Al2O3 was calcined at temperatures between 500 and 1200 degrees C and tested for its performance in the oxidative ethylbenzene dehydrogenation (ODH) over a wide range of industrially-relevant conditions. The original gamma-Al2O3, as well as Z- and alpha-Al2O3, were teste

  17. Development of packed bed membrane reactor for the oxidative dehydrogenation of propane

    Kotanjac, Zeljko

    2009-01-01

    In this research, a reactor concept for the oxidative dehydrogenation of propane was studied. First a literature survey was performed, to investigate which are the best catalyst systems and best operating conditions that result in the largest propylene yield. In the kinetic study of ODHP over a Ga2O

  18. Non-Precious Bimetallic Catalysts for Selective Dehydrogenation of an Organic Chemical Hydride System

    Shaikh Ali, Anaam

    2015-07-06

    Methylcyclohexane (MCH)-Toluene (TOL) chemical hydride cycles as a hydrogen carrier system is successful with the selective dehydrogenation reaction of MCH to TOL, which has been achieved only using precious Pt-based catalysts. Herein, we report improved selectivity using non-precious metal nickel-based bimetallic catalysts, where the second metal occupies the unselective step sites.

  19. Versatile dehydrogenative alcohol silylation catalyzed by Cu(I)-phosphine complex.

    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

  20. Iron-Deficiency Anemia

    Full Text Available ... Deficiency Anemia Explore Iron-Deficiency Anemia What Is... CAUSES WHO IS AT RISK SIGNS & SYMPTOMS DIAGNOSIS TREATMENTS ... less hemoglobin than normal. Iron-deficiency anemia can cause fatigue (tiredness), shortness of breath, chest pain, and ...

  1. Spontaneous dehydrogenation of methanol over defect-free MgO(100) thin film deposited on molybdenum

    Song, Zhenjun

    2016-01-01

    The dehydrogenation reaction of methanol on metal supported MgO(100) films has been studied by employing periodic density functional calculations. As far as we know, the dehydrogenation of single methanol molecule over inert oxide insulators such as MgO has never been realized before without the introduction of defects and low coordinated atoms. By depositing the very thin oxide films on Mo substrate we have successfully obtained the dissociative state of methanol. The dehydrogenation reaction is energetically exothermic and nearly barrierless. The metal supported thin oxide films studied here provide a versatile approach to enhance the activity and properties of oxides.

  2. Theoretical Studies on Dehydrogenation Reactions in Mg2(BH4)2(NH2)2 Compounds

    Zheng Chen; Zhe-ning Chen; An-an Wu; Guo-tao Wu; Zhi-tao Xiong; Ping Chen; Xin Xu

    2012-01-01

    Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage.It is,therefore,important to understand the underlying dehydrogenation mechanisms for further development of these materials.We present a systematic theoretical investigation on the dehydrogenation mechanisms of the Mg2(BH4)2(NH2)2 compounds.We found that dehydrogenation takes place most likely via the intermolecular process,which is favorable both kinetically and thermodynamically in comparison with that of the intramolecular process.The dehydrogenation of Mg2(BH4)2(NH2)2 initially takes place via the direct combination of the hydridic H in BH4-and the protic H in NH2-,followed by the formation of Mg-H and subsequent ionic recombination of Mg-Hδ-… Hδ+-N.

  3. Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system

    Highlights: → Structural change in several dehydrogenation stages of p-c isotherm at 523 K. → Mg(NH2)2 and Li3Mg3(NH2)(NH)4 coexist in the plateau region. → Continuous change from Li3Mg3(NH2)(NH)4 to Li2Mg(NH)2 in the sloping region. → The crystal structure Li3+3yMg3(NH2)1-y(NH)4+2y was determined. → The dehydrogenation by the diffusion of Li+ and Mg2+ without N atom diffusion. - Abstract: The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg3N2 + 4Li3N + 12H2 ↔ 3Mg(NH2)2 + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH2)2 and Li3Mg3(NH2)(NH)4 coexist. In the sloping region, the intermediate phase Li3+3yMg3(NH2)1-y(NH)4+2y changes continuously from Li3Mg3(NH2)(NH)4 to Li2Mg(NH)2. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li3+3yMg3(NH2)1-y(NH)4+2y (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF2-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li+ to cation sites of Mg(NH2)2. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li+ and Mg2+ without N atom diffusion.

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

    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.

  5. Carnitine Deficiency and Pregnancy

    Anouk de Bruyn; Yves Jacquemyn; Kristof Kinget; François Eyskens

    2015-01-01

    We present two cases of carnitine deficiency in pregnancy. In our first case, systematic screening revealed L-carnitine deficiency in the first born of an asymptomatic mother. In the course of her second pregnancy, maternal carnitine levels showed a deficiency as well. In a second case, a mother known with carnitine deficiency under supplementation was followed throughout her pregnancy. Both pregnancies had an uneventful outcome. Because carnitine deficiency can have serious complications, su...

  6. Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

    Gontad, F., E-mail: fran_gontad@yahoo.es [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Conde, J.C. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Filonovich, S.; Cerqueira, M.F.; Alpuim, P. [Department of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Chiussi, S. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain)

    2013-06-01

    We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p{sup +}-nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm{sup 2} is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm{sup 2} promote partial crystallization of the amorphous structures.

  7. Experimental Study of Interfacial Friction in NaBH{sub 4} Solution in Microchannel Dehydrogenation Reactor

    Choi, Seok Hyun; Hwang, Sueng Sik; Lee, Hee Joon [Kookmin Univ., Seoul (Korea, Republic of)

    2014-02-15

    Sodium borohydride (NaBH{sub 4}) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous NaBH{sub 4} solution in a microchannel with a hydraulic diameter of 461 μm is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of NaBH{sub 4} in the presence of a ruthenium catalyst, two different flow phases (aqueous NaBH{sub 4} solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time.

  8. Kinetics of Oxidative Dehydrogenation of Propance over a VMgO Catalyst

    L.Late; E.A.Blekkan

    2002-01-01

    The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃ over a VMgO catalyst,Vanadium-magnesium-oxides are among the moste selective and active catalysts for the dehydrogenation of propance to propylene Selectivity to propylene up to about 60% was obtained at 10% conversion ,but the selectivity decreased with increasing conversion.No oxygenates were detected,the only by-products were CO and CO2 ,The reaction rate of propane was found to be first order in propane and close to zero order in oxygen ,which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate detemining step.The activation energy,of the conversion of propane was found to be 122±6 kJ/mol.

  9. Oxidative Dehydrogenation of Butane to Butadiene and Butene Using a Novel Inert Membrane Reactor

    2000-01-01

    The oxidative dehydrogenation of butane to butadiene and butene was studied using a conventional fixed-bed ractor (FBR), inert membrane reactor (IMR) and mixed inert membrane reactor (MIMR). When IMR and MIMR were employed, a ceramic membrane modified by partially coating with glaze was used to distribute oxygen to a fixed-bed of 24-V-Mg-O catalyst. The oxygen partial pressure in the catalyst bed could be decreased. The effect of feeding modes and operation conditions were investigated. The selectivity of C4 dehydrogenation products (butene and butadiene) was found to be higher in IMR than in FBR. The feeding mode with 20% of air mixing with butane in MIMR was found to be more efficient than the feeding mode with all air permeating through ceramic membrane. The MIMR gave the most smooth temperature profile along the bed.

  10. Dehydrogenation of n-butane over vanadia catalysts supported on silica gel

    Yuebing Xu; Jiangyin Lu; Mei Zhong; Jide Wang

    2009-01-01

    VOx/SiO2 catalysts prepared by impregnation method were used for catalytic dehydrogenation of n-butane to butenes and characterized by X-ray diffraction,FT-IR,UV-vis,Raman,and BET measurements.The effects of VOx loading and the reaction temperature on the VOx/SiO2 catalysts and their catalytic performances for the dehydrogenation of n-butane were studied.When the VOx loading was 12% g/gcat and reaction temperature was between 590 ℃ and 600 ℃,n-butane conversion and butenes yields reached the highest value under H2 flux of 10 ml/min and n-butane flux of 10 ml/min.Product distribution,such as the ratio of 2-butene to 1-butene and the ratio of cis-2-butene to trans-2-butene,was mainly influenced by the reaction temperature.

  11. Kinetics of the Oxidative Dehydrogenation of Propane over a VMgO Catalyst

    L. L(a)te; E.A. Blekkan

    2002-01-01

    The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts forthe dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, theonly by-products were CO and CO2. The reaction rate of propane was found to be first order in propaneand close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with theactivation of the hydrocarbon as the rate determining step. The activation energy of the conversion ofpropane was found to be 122±6 kJ/mol.

  12. Incorporation of catalytic dehydrogenation into fischer-tropsch synthesis to significantly reduce carbon dioxide emissions

    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.

  13. A dehydrogenation mechanism of metal hydrides based on interactions between Hdelta+ and H-.

    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

  14. Experimental Study of Interfacial Friction in NaBH4 Solution in Microchannel Dehydrogenation Reactor

    Sodium borohydride (NaBH4) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous NaBH4 solution in a microchannel with a hydraulic diameter of 461 μm is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of NaBH4 in the presence of a ruthenium catalyst, two different flow phases (aqueous NaBH4 solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time

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

    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.

  16. Genotypic and phenotypic spectrum of pyridoxine-dependent epilepsy (ALDH7A1 deficiency)

    Mills, Philippa B; Footitt, Emma J; Mills, Kevin A;

    2010-01-01

    Pyridoxine-dependent epilepsy was recently shown to be due to mutations in the ALDH7A1 gene, which encodes antiquitin, an enzyme that catalyses the nicotinamide adenine dinucleotide-dependent dehydrogenation of l-alpha-aminoadipic semialdehyde/L-Delta1-piperideine 6-carboxylate. However, whilst...... normal range, DNA sequencing of the ALDH7A1 gene was performed. Clinicians were asked to complete questionnaires on clinical, biochemical, magnetic resonance imaging and electroencephalography features of patients. The clinical spectrum of antiquitin deficiency extended from ventriculomegaly detected on...

  17. Alcohol Dehydrogenation with a Dual Site Ruthenium, Boron Catalyst Occurs at Ruthenium

    Denver Guess; Williams, Travis J.; Conley, Brian L.; Brock Malinoski; Zhiyao Lu; Ana V. Flores

    2012-01-01

    The complex [(κ3-(N,N,O-py2B(Me)OH)Ru(NCMe)3]+ TfO− (1) is a catalyst for transfer dehydrogenation of alcohols, which was designed to function through a cooperative transition state in which reactivity was split between boron and ruthenium. We show here both stoichiometric and catalytic evidence to support that in the case of alcohol oxidation, the mechanism most likely involves reactivity only at the ruthenium center.

  18. Dehydrogenation in lithium borohydride/conventional metal hydride composite based on a mutual catalysis

    Yu, X.B.; Shi, Qing; Vegge, Tejs;

    2009-01-01

    The dehydrogenation of LiBH4 ball-milled with hydrogenated 40Ti–15Mn–15Cr–30V alloy was investigated. It was found that there is a mutual catalysis between the two hydrides, lowering the temperature of hydrogen release from both hydrides. In the case of 1h milled LiBH4/40Ti–15Mn–15Cr–30V with a...

  19. First-principles calculation of dehydrogenating properties of MgH2-V systems

    ZHOU; Dianwu; PENG; Ping; LIU; Jinshui

    2006-01-01

    Based on experimental results in which VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at%V nanocomposite, a VH/MgH2 interface is designed and constituted in this work. A first-principles plane-wave pseudopotential method based on Density Functional Theory (DFT) has been used to investigate the vanadium alloying effects on the dehydrogenating properties of magnesium hydride, i.e., MgH2. A low absolute value of the negative heat of formation of VH/MgH2 interface compared with that of MgH2 indicates that vanadium hydrides befit to improve the dehydrogenating properties of MgH2. Based on the analysis of the density of states (DOS) and the total valence electron density distribution of MgH2 before and after V alloying, it was found that the improvement of the dehydrogenating properties of MgH2 caused by V alloying originates from the increasing of the valence electrons at Fermi level (EF) and the decreasing of the HOMO-LUMO gap (△EH-L) after V alloying. The catalysis effect of V on dehydrogenating kinetics of MgH2 may attribute to a stronger bonding between V and H atoms than that between Mg and H atoms, which leads to nucleation of the α-Mg at the VH/MgH2 interface in the MgH2-V systems easier than that in pure MgH2 phase.

  20. Control led sequential dehydrogenation of single molecules by scanning tunneling microscopy

    Sanvito, Stefano

    2010-01-01

    Scanning tunneling microscopy STM is today the most powerful and versatile tool available for imaging and manipulating single molecules on surfaces. Here, we explore its ultimate limit by demonstrating the possibility of controlling sequential di-dehydrogenation of single Co-Salen molecules sublimated on Cu. In particular, we are able to explore the final products of the H 2 dissociation as well as the intermediate state, in which only one H atom is separated from the ...

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

    Igor B. Krylov

    2015-01-01

    Full Text Available 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(O2CR2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc..

  2. Alcohol Dehydrogenation with a Dual Site Ruthenium, Boron Catalyst Occurs at Ruthenium

    Denver Guess

    2012-10-01

    Full Text Available The complex [(κ3-(N,N,O-py2B(MeOHRu(NCMe3]+ TfO− (1 is a catalyst for transfer dehydrogenation of alcohols, which was designed to function through a cooperative transition state in which reactivity was split between boron and ruthenium. We show here both stoichiometric and catalytic evidence to support that in the case of alcohol oxidation, the mechanism most likely involves reactivity only at the ruthenium center.

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

    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

  4. Heterogeneous Partial (amm) Oxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

    Védrine, Jacques C.

    2016-01-01

    This paper presents an overview of heterogeneous partial (amm)oxidation and oxidative dehydrogenation (ODH) of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the " seven pillars " , and playing a determining role in catalytic properties, are considered to be, namely: isolation of acti...

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

    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

  6. Investigations of VOx/SBA-15 catalytic performance in propane dehydrogenation with CO2

    Ze?czak, Kamila; Michorczyk, Piotr; Ogonowski, Jan

    2011-01-01

    The catalytic activity of V-containing SBA-15 materials wereprepared by incipient wetness method and tested in propane dehydrogenation with carbon dioxide. It has been found that vanadium catalysts show relatively high catalytic activity and selectivity to propene. The highest activity exhibits the sample containing 5 wt. % of V. At temperature 823 K, propane conversion and propene selectivity were 26,7%, while 70 %, respectively.

  7. Experimental Study and Kinetic Modeling of Decoking of Pacol Process Dehydrogenation Catalyst

    M. Toghyani

    2015-07-01

    Full Text Available The Pt/γ-Al2O3 catalyst life time was limited by the formation of coke on the external and internal surfaces of catalyst in dehydrogenation reactors. The kinetics of decoking of dehydrogenation catalyst was studied in a pilot scale fixed bed reactor experimentally. The effects of temperature, oxygen concentration and other operating conditions on decoking process were investigated. A kinetic model was deve-loped to describe the decoking of mentioned catalyst. An objective function was defined as the sum of squares of the deviations among the calculated and plant data. Accordingly the appropriate values were found in order to minimize this function. It was concluded that there was a good agreement between simulation results and experimental data.  © 2015 BCREC UNDIP. All rights reservedReceived: 18th September 2014; Revised: 28th February 2015; Accepted: 9th March 2015How to Cite: Toghyani, M., Rahimi, A., Mamanpoush, M., Kazemian, R., Harandizadeh, A.H. (2015. Experimental Study and Kinetic Modeling of Decoking of Pacol Process Dehydrogenation Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (2: 155-161. (doi:10.9767/bcrec.10.2.7357.155-161 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.7357.155-161  

  8. Dehydration and Dehydrogenation of Ethylene Glycol on Rutile TiO2(110)

    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.

  9. Highly Ordered Mesoporous Metal Oxides as Catalysts for Dehydrogenation of Cyclohexanol

    Lee, Eunok; Jin, Mingshi; Kim, Ji Man [Sungkyunkwan University, Suwon (Korea, Republic of)

    2013-08-15

    Cyclohexanone is important intermediate for the manufacture of caprolactam which is monomer of nylron. Cyclohexanone is generally produced by dehydrogenation reaction of cyclohexanol. In this study, highly mesoporous metal oxides such as meso-WO{sub 3}, meso-TiO{sub 2}, meso-Fe{sub 2}O{sub 3}, meso-CuO, meso-SnO{sub 2} and meso-NiO were synthesized using mesoporous silica KIT-6 as a hard template via nano-replication method for dehydrogenation of cyclohexanol. The overall conversion of cyclohexanol followed a general order: meso-WO{sub 3} >> meso-Fe{sub 2}O{sub 3} > meso-SnO{sub 2} > meso-TiO{sub 2} > meso-NiO > meso-CuO. In particular, meso-WO{sub 3} significantly showed higher activity than the other mesoporous metal oxides. Therefore, the meso-WO{sub 3} has wide range of application possibilities for dehydrogenation of cyclohexanol.

  10. Chemically Modified Activated Carbons as Catalysts of Oxidative Dehydrogenation of n-Butane

    Commercial availability and low price of light alkanes make them very attractive in many branches of industry. Potentially interesting is their use in the process of oxidative dehydrogenation leading to production of olefins. This study was undertaken to characterise the oxidative dehydrogenation of n-butane to 1,3-butadiene (important substrate in production of synthetic rubber and polyamides) taking place over the modified carbon catalysts obtained from peach stones precursor. The catalytic tests were performed in the temperature range 250-450oC at oxygen/n-butane ratio of 1:1. For the majority of the activated carbon samples studied at the lowest temperature the only product was CO2. At 300oC the products of dehydrogenation of n-butane and side products appeared. With increasing temperature the amount of compounds generated increased and in the group of C4 hydrocarbons the dominant were 1-butene and 1,3-butadiene. The most effective catalyst was the sample oxidised with air, the least effective was the sample modified with ammonium peroxydisulphate. (authors)

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

    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.

  12. In situ synchrotron X-ray diffraction study on the dehydrogenation behavior of LiAlH{sub 4}–MgH{sub 2} composites

    Hsu, Wei-Che; Yang, Cheng-Hsien; Tan, Chia-Yen [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tsai, Wen-Ta, E-mail: wttsai@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan (China)

    2014-06-25

    Highlights: • The dehydrogenation behavior of LiAlH{sub 4}–MgH{sub 2} composites was investigated. • LiAlH{sub 4} and MgH{sub 2} exhibited mutual catalytic effects in their dehydrogenation reaction. • Composition dependent dehydrogenation behavior was observed. • Dehydrogenation reaction steps and products were identified. - Abstract: Dehydrogenation behavior of LiAlH{sub 4}–MgH{sub 2} composites was investigated by using thermal gravimetric analysis (TGA) and in situ synchrotron X-ray diffraction (XRD) technique. The experimental results showed that MgH{sub 2} could play a catalytic role in lowing the initial dehydrogenation temperature of LiAlH{sub 4}. Besides, MgH{sub 2} could be destabilized by the dehydrogenation reaction products of LiAlH{sub 4}. The initial dehydrogenation temperature of LiAlH{sub 4}–MgH{sub 2} composites was as low as 145 °C and MgH{sub 2} could decompose below 300 °C. The compounds such as LiMgAlH{sub 6}, Al{sub 3}Mg{sub 2}, Al{sub 12}Mg{sub 17} and Li{sub 0.92}Mg{sub 4.08} formed during dehydrogenation process suggested some mutual reactions proceeded between LiAlH{sub 4} and MgH{sub 2}.

  13. In situ synchrotron X-ray diffraction study on the dehydrogenation behavior of LiAlH4–MgH2 composites

    Highlights: • The dehydrogenation behavior of LiAlH4–MgH2 composites was investigated. • LiAlH4 and MgH2 exhibited mutual catalytic effects in their dehydrogenation reaction. • Composition dependent dehydrogenation behavior was observed. • Dehydrogenation reaction steps and products were identified. - Abstract: Dehydrogenation behavior of LiAlH4–MgH2 composites was investigated by using thermal gravimetric analysis (TGA) and in situ synchrotron X-ray diffraction (XRD) technique. The experimental results showed that MgH2 could play a catalytic role in lowing the initial dehydrogenation temperature of LiAlH4. Besides, MgH2 could be destabilized by the dehydrogenation reaction products of LiAlH4. The initial dehydrogenation temperature of LiAlH4–MgH2 composites was as low as 145 °C and MgH2 could decompose below 300 °C. The compounds such as LiMgAlH6, Al3Mg2, Al12Mg17 and Li0.92Mg4.08 formed during dehydrogenation process suggested some mutual reactions proceeded between LiAlH4 and MgH2

  14. Factor VII deficiency

    ... page: //medlineplus.gov/ency/article/000548.htm Factor VII deficiency To use the sharing features on this page, please enable JavaScript. Factor VII (seven) deficiency is a disorder caused by a ...

  15. Folate-deficiency anemia

    ... medlineplus.gov/ency/article/000551.htm Folate-deficiency anemia To use the sharing features on this page, please enable JavaScript. Folate-deficiency anemia is a decrease in red blood cells (anemia) ...

  16. Leukocyte Adhesion Deficiency (LAD)

    ... Content Marketing Share this: Main Content Area Leukocyte Adhesion Deficiency (LAD) LAD is an immune deficiency in ... are slow to heal also may have LAD. Treatment and Research Doctors prescribe antibiotics to prevent and ...

  17. Iron-Deficiency Anemia

    Full Text Available ... Deficiency Anemia What Is... CAUSES WHO IS AT RISK SIGNS & SYMPTOMS DIAGNOSIS TREATMENTS PREVENTION LIVING WITH CLINICAL ... and women are the two groups at highest risk for iron-deficiency anemia. Outlook Doctors usually can ...

  18. Factor V deficiency

    Factor V deficiency is a condition that is passed down through families, which affects the ability of the blood ... These proteins are called blood coagulation factors. Factor V deficiency is caused by a lack of Factor ...

  19. Iron-Deficiency Anemia

    Full Text Available ... and women are the two groups at highest risk for iron-deficiency anemia. Outlook Doctors usually can successfully ... With and Managing Iron-Deficiency Anemia 05/18/2011 This video— ...

  20. Iron-Deficiency Anemia

    Full Text Available ... This Content: NEXT >> Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video— ... treatment. For more information about living with and managing iron-deficiency anemia, go to the Health Topics ...

  1. Familial lipoprotein lipase deficiency

    ... medlineplus.gov/ency/article/000408.htm Familial lipoprotein lipase deficiency To use the sharing features on this page, please enable JavaScript. Familial lipoprotein lipase deficiency is a group of rare genetic disorders ...

  2. Iron deficiency and cognition

    Hulthén, Lena

    2003-01-01

    Iron deficiency is the most prevalent nutritional disorder in the world. One of the most worrying consequences of iron deficiency in children is the alteration of behaviour and cognitive performance. In iron-deficient children, striking behavioural changes are observed, such as reduced attention span, reduced emotional responsiveness and low scores on tests of intelligence. Animal studies on nutritional iron deficiency show effects on learning ability that parallel the human studies. Despite ...

  3. Iron-Deficiency Anemia

    Full Text Available ... the NHLBI on Twitter. What Is Iron-Deficiency Anemia? Español Iron-deficiency anemia is a common, easily ... Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video—presented by the ...

  4. Iron-Deficiency Anemia

    ... the NHLBI on Twitter. What Is Iron-Deficiency Anemia? Español Iron-deficiency anemia is a common, easily ... Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video—presented by the ...

  5. Iron-Deficiency Anemia

    Full Text Available ... page from the NHLBI on Twitter. What Is Iron-Deficiency Anemia? Español Iron-deficiency anemia is a ... Content: NEXT >> Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video—presented ...

  6. Thermal dehydrogenation of amorphous silicon deposited on c-Si: Effect of the substrate temperature during deposition

    De Calheiros Velozo, A. [Dept. de Fisica, Instituto Superior Tecnico (UTL), Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Lavareda, G. [Dept. de Ciencia dos Materiais, Faculdade de Ciencias e Tecnologia (UNL), 2825-114 Caparica (Portugal); Centro de Tecnologias e Sistemas, Faculdade de Ciencias e Tecnologia (UNL), 2825-114 Caparica (Portugal); Nunes de Carvalho, C. [Dept. de Ciencia dos Materiais, Faculdade de Ciencias e Tecnologia (UNL), 2825-114 Caparica (Portugal); Inst. Ciencia e Eng. de Materiais e Superficies, Instituto Superior Tecnico (UTL), Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Amaral, A. [Dept. de Fisica, Instituto Superior Tecnico (UTL), Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Inst. Ciencia e Eng. de Materiais e Superficies, Instituto Superior Tecnico (UTL), Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

    2012-10-15

    Samples of doped and undoped a-Si:H were deposited at temperatures ranging from 100 C to 350 C and then submitted to different dehydrogenation temperatures (from 350 C to 550 C) and times (from 1 h to 4 h). a-Si:H films were characterised after deposition through the measurements of specific material parameters such as: the optical gap, the conductivity at 25 C, the thermal activation energy of conductivity and its hydrogen content. Hydrogen content was measured after each thermal treatment. Substrate dopant contamination from phosphorus-doped a-Si thin films was evaluated by SIMS after complete dehydrogenation and a junction depth of 0.1 mm was obtained. Dehydrogenation results show a strong dependence of the hydrogen content of the as-deposited film on the deposition temperature. Nevertheless, the dehydrogenation temperature seems to determine the final H content in a way almost independent from the initial content in the sample. H richer films dehydrogenate faster than films with lower hydrogen concentration (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system

    Noritake, T., E-mail: e0553@mosk.tytlabs.co.jp [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Aoki, M.; Matsumoto, M.; Miwa, K.; Towata, S. [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Li, H.-W.; Orimo, S. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2011-07-14

    Highlights: > Structural change in several dehydrogenation stages of p-c isotherm at 523 K. > Mg(NH{sub 2}){sub 2} and Li{sub 3}Mg{sub 3}(NH{sub 2})(NH){sub 4} coexist in the plateau region. > Continuous change from Li{sub 3}Mg{sub 3}(NH{sub 2})(NH){sub 4} to Li{sub 2}Mg(NH){sub 2} in the sloping region. > The crystal structure Li{sub 3+3y}Mg{sub 3}(NH{sub 2}){sub 1-y}(NH){sub 4+2y} was determined. > The dehydrogenation by the diffusion of Li{sup +} and Mg{sup 2+} without N atom diffusion. - Abstract: The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg{sub 3}N{sub 2} + 4Li{sub 3}N + 12H{sub 2} {r_reversible} 3Mg(NH{sub 2}){sub 2} + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH{sub 2}){sub 2} and Li{sub 3}Mg{sub 3}(NH{sub 2})(NH){sub 4} coexist. In the sloping region, the intermediate phase Li{sub 3+3y}Mg{sub 3}(NH{sub 2}){sub 1-y}(NH){sub 4+2y} changes continuously from Li{sub 3}Mg{sub 3}(NH{sub 2})(NH){sub 4} to Li{sub 2}Mg(NH){sub 2}. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li{sub 3+3y}Mg{sub 3}(NH{sub 2}){sub 1-y}(NH){sub 4+2y} (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF{sub 2}-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li{sup +} to cation sites of Mg(NH{sub 2}){sub 2}. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li{sup +} and Mg{sup 2+} without N atom diffusion.

  8. Dehydrogenation of propane in the presence of carbon dioxide over chromium and gallium oxides catalysts

    Lapidus, A.L.; Agafonov, Yu.A.; Gaidai, N.A.; Nekrasov, N.V.; Menshova, M.V.; Kunusova, R.M. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

    2011-07-01

    Effective chromium and gallium oxides supported catalysts were prepared and tested in longduration experiments for propane dehydrogenation in the presence of CO{sub 2}. The optimal concentrations of active metals were found. It was shown that the activity, selectivity and stability of chromium oxides catalysts were higher than these parameters for gallium ones. Mechanism of propane oxidative dehydrogenation was studied over both catalysts using unstationary and spectroscopic methods. The employment of these methods allowed to establish the differences in process mechanism. It was shown that surface hydroxides took participation in propene formation over Cr-catalysts and hydrides - over Ga-ones. Propane and carbon dioxide participated in the reaction from the adsorbed state over both catalysts but they were differed by the adsorption capacity of the reaction components: CO2 was tied more firmly than C{sub 3}H{sub 6} over both catalysts, CO{sub 2} and C{sub 3}H{sub 6} were tied more strongly with Cr-catalysts than with Ga-ones. It was shown that CO{sub 2} took active participation in reverse watergas shift reaction and in oxidation of catalyst surface over chromium oxides catalysts. The main role of CO{sub 2} in propane dehydrogenation over gallium catalysts consisted in a decrease of coke formation. Step-schemes of propene and cracking products formation were proposed on the basis of literature and obtained data: via the redox mechanism over Cr-catalysts and through a heterolytic dissociation reaction pathway over Ga-ones. (orig.)

  9. Heterogeneous catalytic oxidative dehydrogenation of ethylbenzene to styrene with carbon dioxide

    Badstube, T.; Papp, H. [Leipzig Univ. (Germany). Inst. fuer Technische Chemie; Kustrowski, P.; Dziembaj, R. [Jagiellonian Univ., Crakow (Poland). Faculty of Chemistry

    1998-12-31

    Alkaline promoted active carbon supported iron catalysts are very active in the oxidative dehydrogenation of ethylbenzene to styrene in the presence of carbon dioxide. The best results were obtained at 550 C for a Li-promoted catalyst with a conversion of ethylbenzene of 75% and a selectivity towards styrene of nearly 95%. These results are better than those obtained with industrial catalysts which perform the dehydrogenation process with an excess of water. The main product of the dehydrogenation reaction with CO{sub 2} was styrene, but the following by-products were detected - benzene and toluene. The selectivity towards toluene was always higher than towards benzene. We observed also the formation of carbon monoxide and water, which were produced with a constant molar ratio of about 0.8. The weight of the catalysts increased up to 20% during the reaction due to deposition of carbon. Using a too large excess of CO{sub 2} (CO{sub 2}/EB>10) was harmful for the styrene yield. The most favorable molar ratio of CO{sub 2} to EB was 10:1. No correlation between the molar ratios of reactants and the amount of deposited coke on the surface of catalysts was observed. The highest catalytic activity showed iron loaded D-90 catalysts which were promoted with alkali metals in a molar ratio of 1:10. Iron, nickel and cobalt loaded carbonized PPAN, PC, inorganic supports like Al{sub 2}O{sub 3}, SiO{sub 2}/ZrO{sub 2} or TiO{sub 2} respectively and commercial iron catalysts applied for styrene production did not show comparable catalytic activity in similar conditions. (orig.)

  10. Dehydrogenation properties and crystal structure analysis of Mg(BH4)(NH2)

    Highlights: •The thermal properties of Mg(BH4)(NH2) was clarified. •Mg(BH4)(NH2) is crystallized at 453 K and then is stable at 300 K. •The crystal structure of Mg(BH4)(NH2) at 300 K was determined. -- Abstract: Dehydrogenation properties and crystal structure of the double anion complex hydride Mg(BH4)(NH2) were studied by thermal analyses and synchrotron X-ray diffraction. The stoichiometric mixture of Mg(BH4)2 and Mg(NH2)2 were ball-milled and then heated to 453 K to form Mg(BH4)(NH2) crystal. The dehydrogenation of Mg(BH4)(NH2) occurs in two-stage at 513 K and 688 K. The following reaction sequence is suggested by the results of thermal analyses; Mg(BH4)(NH2) → MgH2 + BN + 2H2 (7.3 mass% weight loss) → Mg + BN + 3H2 (11.0 mass% weight loss in total). The dehydrogenation temperature of Mg(BH4)(NH2) is approximately 50 K lower than that of the other double anion complex Li2(BH4)(NH2). The crystal structure of Mg(BH4)(NH2) was determined by the measurement at 300 K (crystal system: tetragonal, space group: I41 (No. 80), lattice constants: a = 5.792(1), c = 20.632(4) Å at 300 K). In the crystal of Mg(BH4)(NH2), the cation (Mg2+) and the anions (BH4- and NH2-) are stacked alternately along the c-axis direction. The Mg2+ cation is tetrahedrally coordinated with two BH4- anions and two NH2- anions

  11. Oxidative Dehydrogenation of Ethane to Ethylene over LiCI/MnOx/PC Catalysts

    葛庆杰; 李文钊; 于春英; 徐恒泳

    2001-01-01

    The caalytic stability of LiCl/MnOx/PC catalyst have been investigated, the deactivation mechanism was discussed. Tne experimental results show that ethane conversion decreases and etihylene selectivotu keeps about 90% as reaction time increases. The main deactivation reasons LiCI/MnOx/PCcatalyst for oxidative dehydrogenation of ethane (ODHE) to ethylene are the transiton of active species Mn2O3 TO MnOspecies and the loss of active component Cl in catalyst. Instead of ethane with FCC tailed-gas, the stability of LiCl/MnOx/PC catalyst has been largely improved.

  12. A STUDY ON MEMBRANE PROCESS WITH γ-ALUMINA MEMBRANE REACTOR FOR ETHYLBENZENE DEHYDROGENATION TO STYRENE

    Chen Qingling; Xu Zhongqiang

    2001-01-01

    The membrane reaction of ethylbenzene(EB) dehydrogenation to styrene(ST) has been studied by using K2O/Fe2O3 industrial catalyst and γ-alumina ceramic membrane developed by our institute. In comparison with the packed bed reactor (that is, plug flow reactor, abbr. PFR) in industrial practice, the yield of styrene was increased by 5%~10% in the membrane reactor. Furthermore, mathematical modeling of membrane reaction has been studied to display the principle of optimal match between the catalytic activity and the membrane permeability.

  13. Kinetics of dehydrogenation of MgH{sub 2} and AlH{sub 3}

    Gabis, I., E-mail: igor.gabis@gmail.com [Physics Department of St. Petersburg State University, St. Petersburg (Russian Federation); Dobrotvorskiy, M.; Evard, E.; Voyt, A. [Physics Department of St. Petersburg State University, St. Petersburg (Russian Federation)

    2011-09-15

    Kinetics of dehydrogenation was studied using isothermal barometry, TDS and SEM methods. Two stages of the decomposition process are considered: incubation preceding the formation of metallic nuclei on the surface of the particle and hydrogen evolution via these metallic regions serving as facilitating channels for desorption. Duration of the first stage depends on the temperature of the sample. Relationship with material's electronic band structure is discussed. Kinetics of the second stage is controlled by two reactions: desorption of the hydrogen molecules from the surface and shift of the metal-hydride interphase in the bulk. Physical mechanisms of decomposition with detailed reaction kinetics are proposed and kinetic parameters are evaluated.

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

    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

  15. Oxygen Assisted Dehydrogenation of Ethane over Alumina Supported Pt-Sn Catalysts

    Radstake, Paul B.

    2012-01-01

    The oxygen-assisted dehydrogenation of ethane (ODE) over supported Pt-Sn catalysts seems to be a promising alternative for the conventional steam cracking of ethane for the production of ethylene. However, despite the fact that much research has been performed on this catalytic system during the last years, little is known about the precise role of the Pt-Sn catalyst on the overall product distribution.The focus of this research work lay therefore on gaining a better understanding of the role...

  16. Formation and Decay of the Dehydrogenated Parent Anion upon Electron Attachment to Dialanine

    Gschliesser, David; Vizcaino, Violaine; Probst, Michael; Scheier, Paul; Denifl, Stephan

    2012-01-01

    Abstract The dehydrogenated parent anion [M−H]− is one of the most dominant anions formed in dissociative electron attachment to various small biomolecules like nucleobases and single amino acids. In the present study, we investigate the [M−H]− channel for the dipeptide dialanine by utilizing an electron monochromator and a two-sector-field mass spectrometer. At electron energies below 2 eV, the measured high-resolution ion-efficiency curve has a different shape to that for the single amino a...

  17. Dynamic Structure of Mo-O Species in Ag-Mo-P-O Catalyst for Oxidative Dehydrogenation of Propane

    2002-01-01

    The dynamic structure of Mo-O species in Ag-Mo-P-O catalyst was studied by in situ confocal microprobe laser Raman spectroscopy (LRS) and catalytic test. The results indicate Mo-O species of MoO3 transformed to Mo-O species of AgMoO2PO4 in C3H8/O2/N2 (3/1/4) flow at 773 K. This behavior is closely relative to oxidative dehydrogenation of propane and intrinsic properties of Mo-O species. The Mo-O species of AgMoO2PO4 may be active species for oxidative dehydrogenation of propane.

  18. A DFT study on the Cu (1 1 1) surface for ethyl acetate synthesis from ethanol dehydrogenation

    Li Ruzhen; Zhang Minhua [Key Laboratory for Green Chemical Technology of Ministry of Education, Tianjin University R and D Center for Petrochemical Technology, Tianjin (China); Yu Yingzhe, E-mail: lrz1699@126.com [Key Laboratory for Green Chemical Technology of Ministry of Education, Tianjin University R and D Center for Petrochemical Technology, Tianjin (China)

    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.

  19. Characterization of Metal Dispersion of Some Naphtha Reforming Catalysts by Methylcyclohexane Dehydrogenation Reaction

    Ameel Mohammed Rahman

    2009-01-01

    Full Text Available The dispersion of supported Pt and Pt–Ir reforming catalysts have been studied, after treatment with oxidative and reducing atmosphere. Methylcyclohexane dehydrogenation reaction in the absence of hydrogen was used as a test reaction. An attempt was made to relate the behavior of the catalysts upon subject to reaction, to the dispersion of the same type of catalysts upon treatment with similar atmosphere and temperatures which appeared in literature. The total conversion of reaction can be explained by a change in metal dispersion. Thus, methylcyclohexane dehydrogenation reaction appears to be a really “structure sensitive” reaction. The toluene yield increases as the oxidation temperature increases over the studied catalyst RG-402, RG-412, RG-422 and RG-432 respectively and reached a maximum value at 550°C. Above 550 the conversion decreases due to the effect of catalyst sintering. No significant change were observed for reduction temperature range 400-600°C for the above studied catalysts.The selectivity order for the studied catalysts and for reduction treatment experiments arranged as follows:RG-422> RG-432> RG-412> RG-402

  20. Rate Parameter Distributions for Isobutane Dehydrogenation and Isobutene Dimerization and Desorption over HZSM-5

    Trevor C. Brown

    2013-11-01

    Full Text Available Deconvolution of the evolved isobutene data obtained from temperature-programmed, low-pressure steady-state conversion of isobutane over HZSM-5 has yielded apparent activation energies for isobutane dehydrogenation, isobutene dimerization and desorption. Intrinsic activation energies and associated isobutane collision frequencies are also estimated. A combination of wavelet shrinkage denoising, followed by time-varying flexible least squares of the evolved mass-spectral abundance data over the temperature range 150 to 450 °C, provides accurate, temperature-dependent, apparent rate parameters. Intrinsic activation energies for isobutane dehydrogenation range from 86 to 235.2 kJ mol−1 (average = 150 ± 42 kJ mol−1 for isobutene dimerization from 48.3 to 267 kJ mol−1 (average = 112 ± 74 kJ mol−1 and for isobutene desorption from 64.4 to 97.8 kJ mol−1 (average = 77 ± 12 kJ mol−1. These wide ranges reflect the heterogeneity and acidity of the zeolite surface and structure. Seven distinct locations and sites, including Lewis and Brønsted acid sites can be identified in the profiles. Isobutane collision frequencies range from 10−0.4 to 1022.2 s−1 and are proportional to the accessibility of active sites, within the HZSM-5 micropores or on the external surface.

  1. Role of Platinum Deposited on TiO2 in Photocatalytic Methanol Oxidation and Dehydrogenation Reactions

    Luma M. Ahmed

    2014-01-01

    Full Text Available Titania modified nanoparticles have been prepared by the photodeposition method employing platinum particles on the commercially available titanium dioxide (Hombikat UV 100. The properties of the prepared photocatalysts were investigated by means of the Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, atomic force microscopy (AFM, and UV-visible diffuse spectrophotometry (UV-Vis. XRD was employed to determine the crystallographic phase and particle size of both bare and platinised titanium dioxide. The results indicated that the particle size was decreased with the increasing of platinum loading. AFM analysis showed that one particle consists of about 9 to 11 crystals. UV-vis absorbance analysis showed that the absorption edge shifted to longer wavelength for 0.5% Pt loading compared with bare titanium dioxide. The photocatalytic activity of pure and Pt-loaded TiO2 was investigated employing the photocatalytic oxidation and dehydrogenation of methanol. The results of the photocatalytic activity indicate that the platinized titanium dioxide samples are always more active than the corresponding bare TiO2 for both methanol oxidation and dehydrogenation processes. The loading with various platinum amounts resulted in a significant improvement of the photocatalytic activity of TiO2. This beneficial effect was attributed to an increased separation of the photogenerated electron-hole charge carriers.

  2. Theoretical Study on the Dehydrogenation Reaction of H2S by VS+ (3∑-)

    2005-01-01

    The dehydrogenation reaction of H2S by the 3∑- ground state of VS+: VS+ + H2S → VS2+ + H2 has been studied by using Density Functional Theory (DFT) at the B3LYP/DZVP level. It is found that the reaction proceeds along two possible pathways (A and B) yielding two isomer dehydrogenation products VS2+-1 (3B2) and VS2+-2 (3A1), respectively. For both pathways,the reaction has a two-step-reaction mechanism that involves the migration of two hydrogen atoms from S2 to V+, respectively. The migration of the second hydrogen via TS3 and that of the first via TS4 are the rate-determining steps for pathways A and B, respectively. The activation energy is 17.4 kcal/mol for pathway A and 22.8 kcal/mol for pathway B relative to the reactants. The calculated reaction heat of 9.9 kcal/mol indicates the endothermicity of pathway A and that of -11.9 kcal/mol suggests the exothermicity of pathway B.

  3. Novel dehydrogenation properties derived from nanoscale LiBH{sub 4}

    Wan Xuefei [Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, CT (United States); Shaw, Leon L., E-mail: leon.shaw@uconn.edu [Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, CT (United States)

    2011-06-15

    Graphical abstract: The nanoscale LiBH{sub 4}: (a) exhibits the largest H{sub 2} release, whereas the bulk LiBH{sub 4}, (c) has the smallest H{sub 2} release with the partially oxidized nanoscale LiBH{sub 4} and (b) showing the intermediate behavior. - Abstract: Nanoscale, amorphous LiBH{sub 4} powder with sizes from 20 to 50 nm is synthesized via a solvent evaporation process without the aid of nanoscaffolds. The nanoscale LiBH{sub 4} starts to release H{sub 2} at {approx}32 deg. C and forms Li{sub 2}B{sub 12}H{sub 12} at 265 deg. C or lower. The amount of H{sub 2} released in the solid state from 25 to 265 deg. C reaches 3.5 wt.%, which is substantially higher than 0.75 wt.% H{sub 2} released by bulk LiBH{sub 4}. These novel dehydrogenation properties have been discussed based on the observed improvements in both the thermodynamic driving force and reaction kinetics. The nanoscale LiBH{sub 4} not only enhances the dehydrogenation kinetics, but also alters the rate-limiting step.

  4. Oxidative dehydrogenation of ethane on rare-earth oxide-based catalysts

    Buyevskaya, O.; Baerns, M. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany)

    1998-12-31

    Results on the oxidative dehydrogenation of ethane on rare-earth oxide (REO) based catalysts (Na-P-Sm-O, Sm-Sr(Ca)-O, La-Sr-O and Nd-Sr-O) are described. Oxygen adsorption was found to be a key factor which determines the activity of this type of catalysts. Continuous flow experiments in the presence of catalysts which reveal strong oxygen adsorption showed that the reaction mixture is ignited resulting in an enhanced heat generation at the reactor inlet. The heat produced by the oxidative reactions was sufficient under the conditions chosen for the endothermic thermal pyrolysis which takes place preferentially in the gas phase. Ignition of the reaction mixture is an important catalyst function. Contrary to non-catalytic oxidative dehydrogenation, reaction temperatures above 700 C could be achieved without significant external heat input. Ethylene yields of up to 34-45% (S=66-73%) were obtained on REO-based catalysts under non-isothermal conditions (T{sub max}=810-865 C) at contact times in the order of 30 to 40 ms. (orig.)

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

    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.

  6. ENHANCEMENT OF EQUILIBRIUMSHIFT IN DEHYDROGENATION REACTIONS USING A NOVEL MEMBRANE REACTOR; FINAL

    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

  7. G6PD Deficiency

    Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a genetic disorder that is most common in males. About 1 in 10 African American males in the United States has it. G6PD deficiency mainly affects red blood cells, which carry oxygen ...

  8. Deficiently Extremal Gorenstein Algebras

    Pavinder Singh

    2011-08-01

    The aim of this article is to study the homological properties of deficiently extremal Gorenstein algebras. We prove that if / is an odd deficiently extremal Gorenstein algebra with pure minimal free resolution, then the codimension of / must be odd. As an application, the structure of pure minimal free resolution of a nearly extremal Gorenstein algebra is obtained.

  9. Iron deficiency anemia

    Anemia - iron deficiency ... iron from old red blood cells. Iron deficiency anemia develops when your body's iron stores run low. ... You may have no symptoms if the anemia is mild. Most of the time, ... slowly. Symptoms may include: Feeling weak or tired more often ...

  10. Nutritional iron deficiency

    Zimmermann, M.B.; Hurrell, R.F.

    2007-01-01

    Iron deficiency is one of the leading risk factors for disability and death worldwide, affecting an estimated 2 billion people. Nutritional iron deficiency arises when physiological requirements cannot be met by iron absorption from diet. Dietary iron bioavailability is low in populations consuming

  11. Vitamin deficiencies and excesses

    Vitamins are essential nutrients that must be supplied exogenously either as part of a well balanced diet or as supplements. Deficiency states are uncommon in developed countries except, perhaps, among some food insecure families. In contrast, deficiency states are quite common in many developing ...

  12. Iron-Deficiency Anemia

    Full Text Available ... Blood Tests Blood Transfusion Restless Legs Syndrome Send a link to NHLBI to someone by E-MAIL | ... Iron-Deficiency Anemia? Español Iron-deficiency anemia is a common, easily treated condition that occurs if you ...

  13. Muscle phosphorylase kinase deficiency

    Preisler, N; Orngreen, M C; Echaniz-Laguna, A; Laforet, P; Lonsdorfer-Wolf, E; Doutreleau, S; Geny, B; Akman, H O; Dimauro, S; Vissing, J

    2012-01-01

    To examine metabolism during exercise in 2 patients with muscle phosphorylase kinase (PHK) deficiency and to further define the phenotype of this rare glycogen storage disease (GSD).......To examine metabolism during exercise in 2 patients with muscle phosphorylase kinase (PHK) deficiency and to further define the phenotype of this rare glycogen storage disease (GSD)....

  14. Lipoprotein lipase deficiency.

    Shankar K; Bava H; Shetty J; Joshi M

    1997-01-01

    A rare case of a 3 month old child with lipoprotein lipase deficiency who presented with bronchopneumonia is reported. After noticing lipaemic serum and lipaemia retinalis, a diagnosis of hyperlipoproteinaemia was considered. Lipoprotein lipase deficiency was confirmed with post heparin lipoprotein lipase enzyme activity estimation.

  15. Catalytic effect of Ti and Ni on dehydrogenation of AlH{sub 3}: A first principles investigation

    Yu, H.Z.; Dai, J.H.; Song, Y., E-mail: sy@hitwh.edu.cn

    2015-08-30

    Graphical abstract: - Highlights: • Ni doped in bulk and on the surface of AlH{sub 3} are unfavourable comparing to Ti. • Ti and Ni prefer to substitute for Al atom in both the bulk and surface doped systems. • Ti improves the dissociation properties of AlH{sub 3} by weakening the interactions between Al and H atoms, but the catalytic effect is weaker if Ti substitutes for Al than its interstitial doping. - Abstract: Ab initio calculations were performed for the M-doped (M = Ti or Ni) AlH{sub 3} to investigate influence of dopants Ti and Ni on the dehydrogenation properties of AlH{sub 3}. It was found that Ti and Ni prefer to substitute for Al atom in both the bulk phase and the slab surface. However a large amount of energy was needed for Ni to dope into AlH{sub 3} making that Ni might not a suitable catalyst for AlH{sub 3}. Mechanisms that Ti improved the dehydrogenation properties of AlH{sub 3} were clarified. Ti greatly decreased the dehydrogenation energy of AlH{sub 3} by weakening the interaction between Al and H atoms, its influence on the dehydrogenation of AlH3 was however sensitive to the occupation behavior. The calculations indicated that the catalytic effect of Ti was weaker if Ti substitutes for Al than its interstitial occupation.

  16. Dehydrogenative Synthesis of Imines from Alcohols and Amines Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

    Maggi, Agnese; Madsen, Robert

    2012-01-01

    applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction. A deuterium labeling experiment indicates that the catalytically active species is a ruthenium dihydride. The reaction is believed to proceed by initial dehydrogenation of the alcohol to the...

  17. Combined oxidative and non-oxidative dehydrogenation of n-butane over VOX species supported on HMS

    Setnička, Michal; Čičmanec, Pavel; Tvarůžková, Eva; Bulánek, Roman

    2013-01-01

    The combination of oxidative and non-oxidative dehydrogenation of n-butane as an attractive possibility for production of C4 olefins was studied over VOX based catalyst. Long-term activity and selectivity to desired products could be achieved over the catalysts with well dispersed monomeric vanadium oxide species supported on mesoporous silica support.

  18. Tailored Formation of N-Doped Nanoarchitectures by Diffusion-Controlled on-Surface (Cyclo)-Dehydrogenation of Heteroaromatics

    Pinardi, A. L.; Otero-Irurueta, G.; Palacio, I.; Martinez, J. I.; Sánchez-Sánchez, C.; Tello, M.; Rogero, C.; Cossaro, A.; Preobrajenski, A.; Gomez-Lor, B.; Jančařík, Andrej; Stará, Irena G.; Starý, Ivo; Lopez, M. F.; Méndez, J.; Martin-Gago, J. A.

    2013-01-01

    Roč. 7, č. 4 (2013), s. 3676-3684. ISSN 1936-0851 R&D Projects: GA ČR(CZ) GAP207/10/2207 Institutional support: RVO:61388963 Keywords : surface-assisted dehydrogenation * dibenzo[5]helicene * N-doped nanographene * heteroaromatic polymer Subject RIV: CC - Organic Chemistry Impact factor: 12.033, year: 2013

  19. Facile synthesis of TiN decorated graphene and its enhanced catalytic effects on dehydrogenation performance of magnesium hydride.

    Wang, Ying; Li, Li; An, Cuihua; Wang, Yijing; Chen, Chengcheng; Jiao, Lifang; Yuan, Huatang

    2014-06-21

    TiN@rGO nanohybrids were successfully synthesized by a simple "urea glass" technique. Experimental results demonstrated that TiN nanocrystals, with an average particle size of 20 nm, were uniformly anchored onto highly reduced graphene nanosheets. The as-synthesized TiN@rGO nanohybrids showed a porous planar-like structure, which had a large surface area of 177 m(2) g(-1). More importantly, the as-prepared TiN@rGO hybrids showed enhanced catalytic effects on the dehydrogenation of MgH2. The dehydrogenation thermodynamics and kinetics of the MgH2-TiN@rGO composites were systematically investigated and some significant improvements were confirmed. It was found that the 10 wt% TiN@rGO doped MgH2 sample started to release hydrogen at about 167 °C, and roughly 6.0 wt% hydrogen was released within 18 min when isothermally heated to 300 °C. In contrast, the onset dehydrogenation temperature of the pure MgH2 sample was about 307 °C, and only 3.5 wt% hydrogen was released even after 120 min of heating under identical conditions. In addition, the catalytic mechanism of TiN@rGO on the dehydrogenation of MgH2 was discussed using the Johnson-Mehl-Avrami (JMA) model and X-ray diffraction equipment. PMID:24817573

  20. The mechanism of pyridine hydrogenolysis on molybdenum-containing catalysts : III. Cracking, hydrocracking, dehydrogenation and disproportionation of pentylamine

    Sonnemans, J.; Mars, P.

    1974-01-01

    The conversion of pentylamine on a MoO3-Al2O3 catalyst was studied between 250 and 350 °C, at various hydrogen pressures. The reactions observed were cracking to pentene and ammonia, hydrocracking to pentane and ammonia, dehydrogenation to pentanimine and butylcarbonitrile, and disproportionation to

  1. Catalytic effect of Ti and Ni on dehydrogenation of AlH3: A first principles investigation

    Graphical abstract: - Highlights: • Ni doped in bulk and on the surface of AlH3 are unfavourable comparing to Ti. • Ti and Ni prefer to substitute for Al atom in both the bulk and surface doped systems. • Ti improves the dissociation properties of AlH3 by weakening the interactions between Al and H atoms, but the catalytic effect is weaker if Ti substitutes for Al than its interstitial doping. - Abstract: Ab initio calculations were performed for the M-doped (M = Ti or Ni) AlH3 to investigate influence of dopants Ti and Ni on the dehydrogenation properties of AlH3. It was found that Ti and Ni prefer to substitute for Al atom in both the bulk phase and the slab surface. However a large amount of energy was needed for Ni to dope into AlH3 making that Ni might not a suitable catalyst for AlH3. Mechanisms that Ti improved the dehydrogenation properties of AlH3 were clarified. Ti greatly decreased the dehydrogenation energy of AlH3 by weakening the interaction between Al and H atoms, its influence on the dehydrogenation of AlH3 was however sensitive to the occupation behavior. The calculations indicated that the catalytic effect of Ti was weaker if Ti substitutes for Al than its interstitial occupation

  2. Theoretical study on the structure and dehydrogenation mechanism of mixed metal amidoborane, Na[Li(NH{sub 2}BH{sub 3})]{sub 2}

    Wang, Kun; Zhang, Jian-Guo, E-mail: zjgbit@bit.edu.cn; He, Piao

    2013-12-25

    Highlights: •The systematic study of its structure and electronic structure in gas and solid phase. •The gas phase structures indicate that Li{sup +} cation and Na{sup +} cation acts as very different roles in the dehydrogenation. •Potential energy curves of dehydrogenation were obtained by CCSD(T) method. •Obtained the dehydrogenation rates similar to the experimental values. -- Abstract: This study is based on the synthesis of a mixed metal amidoborane, Na[Li(NH{sub 2}BH{sub 3})]{sub 2} (SLAB), the first example of an inorganic sodium–lithium compound. This paper is the first systematic study of its structure and dehydrogenation mechanism, and the results obtained were consistent with the experimental results. The first principle method was used to study the structure of SLAB in solid phase, while the second Moller–Plesset Perturbation Theory was used for gas-phase kinetic studies. Potential energy curves were obtained by CCSD(T) method. Three mechanistic pathways were designed to study its dehydrogenation, which include A pathway (without the cleavage of N–B bond (S and S′ pathways)), B pathway (with the cleavage of the intramolecular N–B bond before dehydrogenation), and D pathway (with the formation of direct dihydrogen bonds). Na{sup +} cation movement was proved to play a very important role in the hydrogen-transfer process. Finally, a possible dissociation pathway (A pathway) was confirmed and dehydrogenation rates similar to the experimental values were obtained.

  3. In situ synchrotron X-ray diffraction study on the improved dehydrogenation performance of NaAlH4–Mg(AlH4)2 mixture

    Highlights: •The dehydrogenation reactions of NaAlH4–Mg(AlH4)2 mixture were explored by in situ XRD. •NaAlH4–Mg(AlH4)2 mixture exhibited multiple-step dehydrogenation processes. •The mutual catalytic roles of NaAlH4 and Mg(AlH4)2 in the mixture were investigated. •NaAlH4–Mg(AlH4)2 mixture release 5.35 wt% H2 at an initial temperature of 120 °C. -- Abstract: The dehydrogenation performance and mechanism of the synthesized NaAlH4–Mg(AlH4)2 powders were investigated by performing thermogravimetric analysis and in situ synchrotron X-ray diffraction analysis. NaAlH4 not only facilitates the first step dehydrogenation of Mg(AlH4)2 in lowering its initial dehydrogenation temperature but also increases the total amount of H2 released. Besides, MgH2 and/or Al phases, the products of the first step dehydrogenation reaction, play a catalytic role in lowering the initial dehydrogenation temperature of NaAlH4. The synthesized NaAlH4–Mg(AlH4)2 mixture has an initial dehydrogenation temperature as low as 120 °C, and is able to release 5.35 wt% H2 below 350 °C. The self-catalytic dehydrogenation behavior of the NaAlH4–Mg(AlH4)2 mixture was elaborated in this work with the aid of in situ synchrotron XRD

  4. Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni2P supported on active carbon

    Graphical abstract: - Highlights: • Ni2P catalyst is tested in dehydrogenation of isobutane for the first time. • The effects of Cs promoter on catalytic performance of Ni2P/AC were investigated. • Cs-Ni2P/AC exhibits high activity and selectivity for isobutane dehydrogenation. - Abstract: In this article, an environmentally friendly non-noble-metal class of Cs-Ni2P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H2-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni2P particles, which decreases the strength of Ni-C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni2P/AC catalysts display much higher catalytic performance as compared to Ni2P/AC catalyst. Cs-Ni2P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni2P particles, transfer electron from Cs to Ni, and decrease acid site number and strength

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

    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.

  6. Dehydrogenation properties and crystal structure analysis of Mg(BH{sub 4})(NH{sub 2})

    Noritake, Tatsuo, E-mail: e0553@mosk.tytlabs.co.jp [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Miwa, Kazutoshi; Aoki, Masakazu; Matsumoto, Mitsuru; Towata, Shin-ichi [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Li, Hai-Wen [International Research Center for Hydrogen Energy, Kyushu University, Fukuoka 819-0395 (Japan); Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2013-12-15

    Highlights: •The thermal properties of Mg(BH{sub 4})(NH{sub 2}) was clarified. •Mg(BH{sub 4})(NH{sub 2}) is crystallized at 453 K and then is stable at 300 K. •The crystal structure of Mg(BH{sub 4})(NH{sub 2}) at 300 K was determined. -- Abstract: Dehydrogenation properties and crystal structure of the double anion complex hydride Mg(BH{sub 4})(NH{sub 2}) were studied by thermal analyses and synchrotron X-ray diffraction. The stoichiometric mixture of Mg(BH{sub 4}){sub 2} and Mg(NH{sub 2}){sub 2} were ball-milled and then heated to 453 K to form Mg(BH{sub 4})(NH{sub 2}) crystal. The dehydrogenation of Mg(BH{sub 4})(NH{sub 2}) occurs in two-stage at 513 K and 688 K. The following reaction sequence is suggested by the results of thermal analyses; Mg(BH{sub 4})(NH{sub 2}) → MgH{sub 2} + BN + 2H{sub 2} (7.3 mass% weight loss) → Mg + BN + 3H{sub 2} (11.0 mass% weight loss in total). The dehydrogenation temperature of Mg(BH{sub 4})(NH{sub 2}) is approximately 50 K lower than that of the other double anion complex Li{sub 2}(BH{sub 4})(NH{sub 2}). The crystal structure of Mg(BH{sub 4})(NH{sub 2}) was determined by the measurement at 300 K (crystal system: tetragonal, space group: I4{sub 1} (No. 80), lattice constants: a = 5.792(1), c = 20.632(4) Å at 300 K). In the crystal of Mg(BH{sub 4})(NH{sub 2}), the cation (Mg{sup 2+}) and the anions (BH{sub 4}{sup -} and NH{sub 2}{sup -}) are stacked alternately along the c-axis direction. The Mg{sup 2+} cation is tetrahedrally coordinated with two BH{sub 4}{sup -} anions and two NH{sub 2}{sup -} anions.

  7. A First Principles Study of Mass Transport in the Dehydrogenation of Lithium Amides and Lithium Alanates

    Rolih, Biljana

    The pursuit of competitive alternatives to energy derived from the combustion of fossil fuels, has led to a great variety of new technologies. Exceptional develop- ments in electrochemical storage and production promise to lead to clean burning passenger vehicles. The high chemical density of a hydrogen fuel cell enables it to meet current standards for driving range and weight required of vehicles, making it an excellent candidate for universal application in the automotive industry. One of the biggest obstacles the fuel cell industry has yet to overcome is the means of practical hydrogen storage. Solid state metal hydrides are a class of materials that show potential for both economic and practical hydrogen storage. The search for the ideal metal hydride is defined by thermodynamic and kinetic constraints, since the requirements for a viable system are a rapid release of hydrogen in the temperature range of -40°C, to 80°C. First-principles density functional theory is an excellent method for gaining insight into the kinetics and thermodynamics of metal hydride solid state reactions. In the work presented here, density functional theory is used to explore formation energies, concentrations and migration barriers of metal hydrides. In particular, the following systems were analyzed: • Li - N - H It is well known that the reactive hydride composite LiNH 2 + LiH reversibly releases a large amount of hydrogen gas, with more favorable thermodynamics than LiNH2 alone. Kinetics of mass transport during the dehydrogenation of LiNH2 + LiH are investigated. A model is developed for determining activation energies of native defects in bulk crystals. In order to establish whether mass transport is the rate-limiting step in the dehydrogenation reaction, results are compared to experimental values. • Li - Al - H Kinetics of mass transport during the dehydrogenation of the metal hydride LiAlH2 are investigated. It is known that LiAlH4 endothermically decomposes via a two

  8. Thiamine deficiency and delirium.

    Osiezagha, Kenneth; Ali, Shahid; Freeman, C; Barker, Narviar C; Jabeen, Shagufta; Maitra, Sarbani; Olagbemiro, Yetunde; Richie, William; Bailey, Rahn K

    2013-04-01

    Thiamine is an essential vitamin that plays an important role in cellular production of energy from ingested food and enhances normal neuronal actives. Deficiency of this vitamin leads to a very serious clinical condition known as delirium. Studies performed in the United States and other parts of the world have established the link between thiamine deficiency and delirium. This literature review examines the physiology, pathophysiology, predisposing factors, clinical manifestations (e.g., Wernicke's encephalopathy, Wernicke-Korsakoff syndrome, structural and functional brain injuries) and diagnosis of thiamine deficiency and delirium. Current treatment practices are also discussed that may improve patient outcome, which ultimately may result in a reduction in healthcare costs. PMID:23696956

  9. Metal oxides modified NiO catalysts for oxidative dehydrogenation of ethane to ethylene

    Zhu, Haibo

    2014-06-01

    The sol-gel method was applied to the synthesis of Zr, Ti, Mo, W, and V modified NiO based catalysts for the ethane oxidative dehydrogenation reaction. The synthesized catalysts were characterized by XRD, N2 adsorption, SEM and TPR techniques. The results showed that the doping metals could be highly dispersed into NiO domains without the formation of large amount of other bulk metal oxide. The modified NiO materials have small particle size, larger surface area, and higher reduction temperature in contrast to pure NiO. The introduction of group IV, V and VI transition metals into NiO decreases the catalytic activity in ethane ODH. However, the ethylene selectivity is enhanced with the highest level for the Ni-W-O and Ni-Ti-O catalysts. As a result, these two catalysts show improved efficiency of ethylene production in the ethane ODH reaction. © 2014 Elsevier B.V. All rights reserved.

  10. Highly selective oxidative dehydrogenation of ethane with supported molten chloride catalysts

    Gaertner, C.A.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen (Germany). Catalysis Research Center

    2011-07-01

    Ethene production is one of the most important transformations in chemical industry, given that C{sub 2}H{sub 4} serves as building block for many mass-market products. Besides conventional thermal processes like steam cracking of ethane, ethane can be produced selectively by catalytic processes. One of the classes of catalysts that have been reported in literature as active and highly selective for the oxidative dehydrogenation of ethane is that of supported molten chloride catalysts, containing an alkali chloride overlayer on a solid support. This work deals with fundamental aspects of the catalytic action in latter class of catalysts. Results from kinetic reaction studies are related to observations in detailed characterization and lead to a comprehensive mechanistic understanding. Of fundamental importance towards mechanistic insights is the oxygen storage capacity of the catalysts that has been determined by transient step experiments. (orig.)

  11. High speed laser activated membrane introduction mass spectrometric evaluation of bulk methylcyclohexane dehydrogenation catalysts

    Laser activated membrane introduction mass spectrometry (LAMIMS) is a modification of membrane introduction mass spectrometry where a silicone membrane serves as a separator between an analyte stream and the vacuum of a quadrupole mass spectrometer. Carbon paper, commonly used as a fuel cell gas diffusion layer, has been overlaid upon the silicone membrane to serve as a support for catalyst array libraries that are heated by a CO2 laser during evaluation. The LAMIMS reactor is a closed environment permitting steady state exposure of the catalyst library to the reactant stream. In this work, Pt/Al2O3 catalysts for the dehydrogenation of methylcyclohexane (MCH) to toluene have been ranked by LAMIMS. Spot-to-spot evaluation times (after preconditioning) are 1 min in this study. The data suggests that by optimization of signal-to-noise and spot-to-spot dwell times, ranking can be conducted at substantially under a minute per array spot candidate

  12. Influence of promoters and oxidants on propane dehydrogenation over chromium-oxide catalysts

    Lapidus, A.L.; Agafonov, Yu.A.; Shaporeva, N.Yu.; Trushin, D.V.; Gaidai, N.A.; Nekrasov, N.V. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

    2010-12-30

    Possibilities for increasing the efficiency of supported on SiO{sub 2} chromium-oxide catalysts in propane oxidative dehydrogenation in CO{sub 2} presence are investigated: the introduction of Li, Na, K, Ca in catalysts and the addition of O{sub 2} in the reaction mixture. It was been found that the positive role of K - the increase of the selectivity to propene and stability of catalysts at long-duration tests - appeared at the relation of Cr:K=20. It was shown that the presence of little amount of O{sub 2} (2%) in the reaction mixtures of propane and carbon dioxide resulted in the increase of propene yield and catalyst stability. (orig.)

  13. Concept and progress in coupling of dehydrogenation and hydrogenation reactions through catalysts

    C V Pramod; C Raghavendra; K Hari Prasad Reddy; G V Ramesh Babu; K S Rama Rao; B David Raju

    2014-03-01

    This review focuses on the importance of coupling of catalytic reactions which involves dehydrogenation and hydrogenation simultaneously and the study of catalytic materials that are designed, adopted and/or modified for these reactions. The special features of these reactions are minimization of H2 utilization and reduction in production cost. Structural and textural properties also play a decisive role in this kind of coupled reactions. This particular review although not comprehensive discusses the significant progress made in the area of coupled reactions and also helps future researchers or engineers to find out the improvements required in areas such as advancements in catalytic material preparation, design of the new reactors and the application of new technologies.

  14. Compensation Effect in the Hydrogenation/Dehydrogenation Kinetics of Metal Hydrides

    Andreasen, A.; Vegge, T.; Pedersen, Allan Schrøder

    2005-01-01

    The possible existence of a compensation effect, i.e. concurrent changes in activation energy and prefactor, is investigated for the hydrogenation and dehydrogenation kinetics of metal hydrides, by analyzing a series of reported kinetic studies on Mg and LaNi5 based hydrides. For these systems, we...... find a clear linear relation between apparent prefactors and apparent activation energies, as obtained from an Arrhenius analysis, indicating the existence of a compensation effect. Large changes in apparent activation energies in the case of Mg based hydrides are rationalized in terms of a dependency...... of observed apparent activation energy on the degree of surface oxidation, i.e., a physical effect. On the other hand, we find the large concurrent changes in apparent prefactors to be a direct result of the Arrhenius analysis. Thus, we find the observed compensation effect to be an artifact of the data...

  15. Minor dehydrogenated and cleavaged dammarane-type saponins from the steamed roots of Panax notoginseng.

    Gu, Cheng-Zhen; Lv, Jun-Jiang; Zhang, Xiao-Xia; Yan, Hui; Zhu, Hong-Tao; Luo, Huai-Rong; Wang, Dong; Yang, Chong-Ren; Xu, Min; Zhang, Ying-Jun

    2015-06-01

    Nine new minor dehydrogenated and cleavaged dammarane-type triterpenoid saponins, namely notoginsenosides ST6-ST14 (1-9) were isolated from the steamed roots of Panax notoginseng, together with 14 known ones. Among them, 5-7 and 21-22 were protopanaxadiol type and the left 18 compounds, including 1-4, 8-20, and 23 were protopanaxatriol type saponins. Their structures were identified by extensive analysis of MS, 1D and 2D NMR spectra, and acidic hydrolysis. Resulted from the side chain cleavage, the new saponins 1 and 2 featured in a ketone group at C-25, and 3-5 had an aldehyde unit at C-23. The known saponins 12, 16 and 18 displayed the enhancing potential of neurite outgrowth of NGF-mediated PC12 cells at a concentration of 10 μM, while 20 exhibited acetyl cholinesterase inhibitory activity, with IC50 value of 13.97 μM. PMID:25797537

  16. Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

    Zhu, Haibo

    2015-03-05

    The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300°C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90% of their original intrinsic activity was retained after 50h with time on-stream. Furthermore, the stability was much less affected by the Nb content than in composites prepared by classical "wet" syntheses. These materials, obtained in a solvent-free way, are thus promising green and sustainable alternatives to the current Ni-Nb candidates for the low-temperature ODH of ethane.

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

    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

  18. Iron-Deficiency Anemia

    Full Text Available ... symptoms. Severe iron-deficiency anemia can lead to heart problems, infections, problems with growth and development in ... 18/2011 This video—presented by the National Heart, Lung, and Blood Institute, part of the National ...

  19. Iron-Deficiency Anemia

    Full Text Available ... Entire Site Health Topics News & Resources Intramural Research Public Health Topics Education & Awareness Resources Contact The Health ... Severe iron-deficiency anemia can lead to heart problems, infections, problems with growth and development in children, ...

  20. Folate-deficiency anemia

    Folate-deficiency anemia is a decrease in red blood cells (anemia) due to a lack of folate. Folate is a type ... B vitamin. It is also called folic acid. Anemia is a condition in which the body does ...

  1. Sleep Deprivation and Deficiency

    ... page from the NHLBI on Twitter. What Are Sleep Deprivation and Deficiency? Sleep deprivation (DEP-rih-VA- ... Rate This Content: NEXT >> Updated: February 22, 2012 Sleep Infographic Sleep Disorders & Insufficient Sleep: Improving Health through ...

  2. Iron-Deficiency Anemia

    Full Text Available ... Digg. Share this page from the NHLBI on Facebook. Add this link to the NHLBI to my ... such as tiredness, poor skin tone, dizziness, and depression. After her doctor diagnosed her with iron-deficiency ...

  3. Iron-Deficiency Anemia

    Full Text Available ... Topics Anemia Blood Tests Blood Transfusion Restless Legs Syndrome Send a link to NHLBI to someone by ... symptoms. Severe iron-deficiency anemia can lead to heart problems, infections, problems with growth and development in ...

  4. Iron-Deficiency Anemia

    Full Text Available ... CAUSES WHO IS AT RISK SIGNS & SYMPTOMS DIAGNOSIS TREATMENTS PREVENTION LIVING WITH CLINICAL TRIALS LINKS Related Topics ... Doctors usually can successfully treat iron-deficiency anemia. Treatment will depend on the cause and severity of ...

  5. Iron-Deficiency Anemia

    Full Text Available ... iron-rich protein that carries oxygen from the lungs to the rest of the body. Iron-deficiency ... 2011 This video—presented by the National Heart, Lung, and Blood Institute, part of the National Institutes ...

  6. Iron-Deficiency Anemia

    Full Text Available ... Health Topics Education & Awareness Resources Contact The Health Information Center Health Professionals Systematic Evidence Reviews & Clinical Practice ... and see the benefits of treatment. For more information about living with and managing iron-deficiency anemia, ...

  7. Iron-Deficiency Anemia

    Full Text Available ... Alerts E-Newsletters About NHLBI Organization NHLBI Director Budget, Planning, & Legislative Advisory Committees Contact Us FAQs Home » ... severity of the condition. Treatments may include dietary changes, medicines, and surgery. Severe iron-deficiency anemia may ...

  8. Iron-Deficiency Anemia

    Full Text Available ... intravenous iron therapy. Rate This Content: NEXT >> Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video—presented by the National Heart, Lung, and Blood ...

  9. A study of the isobutane dehydrogenation in a porous membrane catalytic reactor: design, use and modelling

    Casanave, D.

    1996-01-26

    The aim of this study was to set up and model a catalytic fixed-bed membrane reactor for the isobutane dehydrogenation. The catalyst, developed at Catalysis Research Institute (IRC), was a silicalite-supported Pt-based catalyst. Their catalytic performances (activity, selectivity, stability) where found better adapted to the membrane reactor, when compared with commercial Pt or Cr based catalysts. The kinetic study of the reaction has been performed in a differential reactor and led to the determination of a kinetic law, suitable when the catalyst is used near thermodynamic equilibrium. The mass transfer mechanisms were determined in meso-porous and microporous membranes through both permeability and gas mixtures (iC{sub 4}/H{sub 2}/N{sub 2}) separation measurements. For the meso-porous {gamma}-alumina, the mass transfer is ensured by a Knudsen diffusion mechanism which can compete with surface diffusion for condensable gas like isobutane. The resulting permselectivity H{sub 2}/iC4 of this membrane is low ({approx} 4). For the microporous zeolite membrane, molecular sieving occurs due to steric hindrance, leading to higher permselectivity {approx}14. Catalyst/membrane associations were compared in terms of isobutane dehydrogenation performances, for both types of membranes (meso-porous and microporous) and for two different reactor configurations (co-current and counter-current sweep gas flow). The best experimental results were obtained with the zeolite membrane, when sweeping the outer compartment in a co-current flow. The equilibrium displacement observed with the {gamma}-alumina membrane was lower and mainly due to a dilution effect of the reaction mixture by the sweep gas. A mathematical model was developed, which correctly describes all the experimental results obtained with the zeolite membrane, when the co-current mode is used. (Abstract Truncated)

  10. Ethylbenzene dehydrogenation over binary FeOx–MeOy/Mg(Al)O catalysts derived from hydrotalcites

    Balasamy, Rabindran J.

    2010-12-20

    A series of FeOx-MeOy/Mg(Al)O catalysts were prepared from hydrotalcite-like compounds as precursors and were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The hydrotalcite-like precursors of the metal compositions of Mg3Fe 0.25Me0.25Al0.5 (Me = Cu, Zn, Cr, Mn, Fe, Co and Ni) were coprecipitated from the nitrates of metal components and calcined to mixed oxides at 550 °C. After the calcination, the mixed oxides showed high surface area of 150-200 m2 gcat -1, and were mainly composed of (MgMe)(Fe3+Al)O periclase in the bulk, whereas the surface was enriched by (MgMe)(Fe3+Al)2O 4 pinel. Among the Me species tested, Co2+ was the most effective, followed by Ni2+. Co2+ addition increased the activity of original FeOx/Mg(Al)O catalyst, whereas Ni2+ increased the activity at the beginning of reaction, but deactivated the catalyst during the reaction. The other metals formed isolated MeOx species in the catalyst, resulting in a decrease in the activity compared to the original FeOx/Mg(Al)O catalyst. The active Fe species exists as metastable Fe3+ on the FeOx/Mg(Al)O catalyst. By the addition of Co2+, the reduction-oxidation between Fe3+ and Fe2+ was facilitated and, moreover, the active Fe3+ species was stabilized. It is likely that the dehydrogenation proceeds on the active Fe3+ species via its reduction-oxidation assisted by Co 2+. © 2010 Elsevier B.V.

  11. Kinetics modeling of ethylbenzene dehydrogenation to styrene over a mesoporous alumina supported iron catalyst

    Hossain, Mohammad M.

    2012-10-01

    The kinetics of ethylbenzene (EB) dehydrogenation over a FeO x-meso-Al 2O 3 catalyst is studied. The models were developed based on physicochemical characterization and a CREC fluidized Riser Simulator data. N 2 adsorption shows that the synthesized FeO x-meso-Al 2O 3 catalyst is mesoporous with pore size between 9 and 35nm. TPR profile indicates that iron on meso-Al 2O 3 forms easily reducible nanostructured crystals which is confirmed by TEM image. NH 3- and CO-TPD analysis, respectively reveals the availability of both acidic and basic sites. The dehydrogenation of ethylbenzene on FeO x-meso-Al 2O 3 catalyst mainly gives styrene (∼99%) while a small amount of benzene, toluene and coke are also detected. Based on the experimental observations two Langmuir-Hinshelwood type kinetics models are formulated. The possible catalyst deactivation is expressed as function of EB conversion. Parameters are estimated by fitting of the experimental data implemented in MATLAB. Results show that one type site Langmuir-Hinshelwood model appropriately describes the experimental data, with adequate statistical fitting indicators and also satisfied the physical constraints. The activation energy for the formation of styrene (80kJ/mol) found to be significantly lower than that of the undesired products benzene (144kJ/mol) and toluene (164kJ/mol). The estimated heat of adsorptions of EB and ST are found to be 55kJ/mol and 19kJ/mol, respectively. © 2012 Elsevier B.V.

  12. Clinical significance of complement deficiencies.

    Pettigrew, H David; Teuber, Suzanne S; Gershwin, M Eric

    2009-09-01

    The complement system is composed of more than 30 serum and membrane-bound proteins, all of which are needed for normal function of complement in innate and adaptive immunity. Historically, deficiencies within the complement system have been suspected when young children have had recurrent and difficult-to-control infections. As our understanding of the complement system has increased, many other diseases have been attributed to deficiencies within the complement system. Generally, complement deficiencies within the classical pathway lead to increased susceptibility to encapsulated bacterial infections as well as a syndrome resembling systemic lupus erythematosus. Complement deficiencies within the mannose-binding lectin pathway generally lead to increased bacterial infections, and deficiencies within the alternative pathway usually lead to an increased frequency of Neisseria infections. However, factor H deficiency can lead to membranoproliferative glomerulonephritis and hemolytic uremic syndrome. Finally, deficiencies within the terminal complement pathway lead to an increased incidence of Neisseria infections. Two other notable complement-associated deficiencies are complement receptor 3 and 4 deficiency, which result from a deficiency of CD18, a disease known as leukocyte adhesion deficiency type 1, and CD59 deficiency, which causes paroxysmal nocturnal hemoglobinuria. Most inherited deficiencies of the complement system are autosomal recessive, but properidin deficiency is X-linked recessive, deficiency of C1 inhibitor is autosomal dominant, and mannose-binding lectin and factor I deficiencies are autosomal co-dominant. The diversity of clinical manifestations of complement deficiencies reflects the complexity of the complement system. PMID:19758139

  13. Adult growth hormone deficiency

    Vishal Gupta

    2011-01-01

    Adult growth hormone deficiency (AGHD) is being recognized increasingly and has been thought to be associated with premature mortality. Pituitary tumors are the commonest cause for AGHD. Growth hormone deficiency (GHD) has been associated with neuropsychiatric-cognitive, cardiovascular, neuromuscular, metabolic, and skeletal abnormalities. Most of these can be reversed with growth hormone therapy. The insulin tolerance test still remains the gold standard dynamic test to diagnose AGHD. Growth...

  14. Iron deficiency anemia Review

    Yıldız, İnci

    2009-01-01

    Iron deficiency anemia is the most frequent and widespread anemia around the world Its prevalence is increased in infants and adolescent girls The etiologic factors may vary but anemia is essentially related to iron deficient nutrition blood loss and malabsorption Children may have paleness cardiovascular and neurologic impacts of anemia pica epithelial changes as koilonychia glossitis angular stomatitis Treatment is by oral or parenteral supplementation of iron Turk Arch Ped 2009; 44 Suppl: ...

  15. Iron deficiency in Europe.

    Hercberg, S; Preziosi, P; Galan, P

    2001-04-01

    In Europe, iron deficiency is considered to be one of the main nutritional deficiency disorders affecting large fractions of the population, particularly such physiological groups as children, menstruating women and pregnant women. Some factors such as type of contraception in women, blood donation or minor pathological blood loss (haemorrhoids, gynaecological bleeding...) considerably increase the difficulty of covering iron needs. Moreover, women, especially adolescents consuming low-energy diets, vegetarians and vegans are at high risk of iron deficiency. Although there is no evidence that an absence of iron stores has any adverse consequences, it does indicate that iron nutrition is borderline, since any further reduction in body iron is associated with a decrease in the level of functional compounds such as haemoglobin. The prevalence of iron-deficient anaemia has slightly decreased in infants and menstruating women. Some positive factors may have contributed to reducing the prevalence of iron-deficiency anaemia in some groups of population: the use of iron-fortified formulas and iron-fortified cereals; the use of oral contraceptives and increased enrichment of iron in several countries; and the use of iron supplements during pregnancy in some European countries. It is possible to prevent and control iron deficiency by counseling individuals and families about sound iron nutrition during infancy and beyond, and about iron supplementation during pregnancy, by screening persons on the basis of their risk for iron deficiency, and by treating and following up persons with presumptive iron deficiency. This may help to reduce manifestations of iron deficiency and thus improve public health. Evidence linking iron status with risk of cardiovascular disease or cancer is unconvincing and does not justify changes in food fortification or medical practice, particularly because the benefits of assuring adequate iron intake during growth and development are well established

  16. Glucose-6-phosphate dehydrogenase deficiency

    G-6-PD deficiency; Hemolytic anemia due to G6PD deficiency; Anemia - hemolytic due to G6PD deficiency ... G6PD deficiency occurs when a person is missing or doesn't have enough of an enzyme called glucose- ...

  17. Influence of Vanadium Oxidation States on the Performance of V-Mg-Al Mixed-Oxide Catalysts for the Oxidative Dehydrogenation of Propane

    Leticia Schacht; Juan Navarrete; Persi Schacht; Ramírez, Marco A.

    2010-01-01

    V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %). Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined...

  18. Dehydrogenation of N{sub 2}H{sub X} (X = 2 − 4) by nitrogen atoms: Thermochemical and kinetics

    Spada, Rene Felipe Keidel; Araujo Ferrão, Luiz Fernando de [Departamento de Química, Instituto Tecnológico de Aeronáutica, São José dos Campos 12.228-900, São Paulo (Brazil); Departamento de Física, Instituto Tecnológico de Aeronáutica, São José dos Campos 12.228-900, São Paulo (Brazil); Roberto-Neto, Orlando [Divisão de Aerotermodinâmica e Hipersônica, Instituto de Estudos Avançados, São José dos Campos 12.229-840, São Paulo (Brazil); Machado, Francisco Bolivar Correto, E-mail: fmachado@ita.br [Departamento de Química, Instituto Tecnológico de Aeronáutica, São José dos Campos 12.228-900, São Paulo (Brazil)

    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, N{sub 2}H{sub 4} + N, N{sub 2}H{sub 3} + N, and N{sub 2}H{sub 2} + 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{sup −20} cm{sup 3} molecule{sup −1} s{sup −1} at 298 K.

  19. Antepartum ornithine transcarbamylase deficiency.

    Nakajima, Hitoshi; Sasaki, Yosuke; Maeda, Tadashi; Takeda, Masako; Hara, Noriko; Nakanishi, Kazushige; Urita, Yoshihisa; Hattori, Risa; Miura, Ken; Taniguchi, Tomoko

    2014-01-01

    Ornithine transcarbamylase deficiency (OTCD) is the most common type urea cycle enzyme deficiencies. This syndrome results from a deficiency of the mitochondrial enzyme ornithine transcarbamylase, which catalyzes the conversion of ornithine and carbamoyl phosphate to citrullin. Our case was a 28-year-old female diagnosed with OTCD following neurocognitive deficit during her first pregnancy. Although hyperammonemia was suspected as the cause of the patient's mental changes, there was no evidence of chronic liver disease. Plasma amino acid and urine organic acid analysis revealed OTCD. After combined modality treatment with arginine, sodium benzoate and hemodialysis, the patient's plasma ammonia level stabilized and her mental status returned to normal. At last she recovered without any damage left. PMID:25759629

  20. Mechanistic understanding and kinetic studies of highly selective oxidative dehydrogenation of ethane over novel supported molten chloride catalysts

    Gaertner, C.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry

    2012-07-01

    Ethene is one of the most important feedstocks for chemical industry, nowadays mainly produced via steam cracking. However, oxidative dehydrogenation becomes a more important process route, allowing to produce ethene selectively and at lower temperatures. Supported alkali chloride catalysts are promising materials. However, the ODH mechanism of this class of catalysts is not well investigated so far. The investigation of the reaction mechanism is thus the aim of this contribution. (orig.)

  1. Study of the performance of vanadium based catalysts prepared by grafting in the oxidative dehydrogenation of propane

    Santacesaria, E.; Carotenuto, G.; Tesser, R.; Di Serio, M. [Naples Univ. (Italy). Dept. of Chemistry

    2011-07-01

    The oxidative dehydrogenation (ODH) of propane has been investigated by using many different vanadia based catalysts, prepared by grafting technique and containing variable amounts of active phase supported on SiO{sub 2} previously coated, by grafting in three different steps, with multilayer of TiO{sub 2}. A depth catalytic screening, conducted in a temperature range of 400-600 C, at atmospheric pressure and in a range of residence time W/F=0.08-0.33 ghmol{sub -1}, has shown that the vanadium oxide catalysts on TiO{sub 2}-SiO{sub 2} support, prepared by grafting have good performances in the ODH of propane. In particular, a preliminary study has demonstrated that higher selectivities can be obtained employing catalysts having a well dispersed active phase that can be achieved with a V{sub 2}O{sub 5} content lower than 10%{sub w}t. It is well known that, in the case of redox catalysts, an increase of the selectivity can be achieved not only by using an adequate catalytic system but also via engineering routes like decoupling catalytic steps of reduction and re-oxidation. In fact it has been observed that by operating in dehydrogenating mode, on the same catalysts, a higher selectivity is obtained although the catalyst is poisoned by the formation of coke on the surface. As consequence of the results obtained in dehydrogenation, in this work has been explored the possibility to feed low amounts of oxygen, below the stoichiometric level with the aim to keep clean the surface from coke but maintaining high the selectivity, because, dehydrogenation reaction prevails. In this work, the behavior of catalysts containing different amounts of V2O5 has been studied in the propane-propene reaction by using different ratios C{sub 3}H{sub 8}/O{sub 2} included in the range 0-2. (orig.)

  2. Catalytic mechanism of the dehydrogenation of ethylbenzene over Fe–Co/Mg(Al)O derived from hydrotalcites

    Tope, Balkrishna B.

    2011-11-01

    Catalytic mechanism of ethylbenzene dehydrogenation over Fe-Co/Mg(Al)O derived from hydrotalcites has been studied based on the XAFS and XPS catalyst characterization and the FTIR measurements of adsorbed species. Fe-Co/Mg(Al)O showed synergy, whereas Fe-Ni/Mg(Al)O showed no synergy, in the dehydrogenation of ethylbenzene. Ni species were stably incorporated as Ni2+ in the regular sites in periclase and spinel structure in the Fe-Ni/Mg(Al)O. Contrarily, Co species exists as a mixture of Co3+/Co2+ in the Fe-Co/Mg(Al)O and was partially isolated from the regular sites in the structures with increasing the Co content. Co addition enhanced Lewis acidity of Fe3+ active sites by forming Fe3+-O-Co 3+/2+(1/1) bond, resulting in an increase in the activity. FTIR of ethylbenzene adsorbed on the Fe-Co/Mg(Al)O clearly showed formations of C-O bond and π-adsorbed aromatic ring. This suggests that ethylbenzene was strongly adsorbed on the Fe3+ acid sites via π-bonding and the dehydrogenation was initiated by α-H+ abstraction from ethyl group on Mg2+-O2- basic sites, followed by C-O-Mg bond formation. The α-H+ abstraction by O2-(-Mg 2+) was likely followed by β-H abstraction, leading to the formations of styrene and H2. Such catalytic mechanism by the Fe 3+ acid-O2-(-Mg2+) base couple and the Fe 3+/Fe2+ reduction-oxidation cycle was further assisted by Co3+/Co2+, leading to a good catalytic activity for the dehydrogenation of ethylbenzene. © 2011 Elsevier B.V. All rights reserved.

  3. Characterization of Industrial Pt-Sn/Al2O3 Catalyst and Transient Product Formations during Propane Dehydrogenation

    Kah Sing Ho; Joanna Jo Ean Chye; Sim Yee Chin; Chin Kui Cheng

    2013-01-01

    The major problem plaguing propane dehydrogenation process is the coke formation on the Pt-Sn/Al2O3 catalyst which leads to catalyst deactivation. Due to information paucity, the physicochemical characteristics of the commercially obtained regenerated Pt-Sn/Al2O3 catalyst (operated in moving bed reactor) and coke formation at different temperatures of reaction were discussed. The physicochemical characterization of regenerated catalyst gave a BET surface area of 104.0 m2/g with graphitic carb...

  4. Chemical, Structural, and Morphological Changes of a MoVTeNb Catalyst during Oxidative Dehydrogenation of Ethane

    Valente, Jaime S.; Armendariz-Herrera, Héctor; Quintana-Solorzano, Roberto; Del Angel, Paz; Nava, Noel; Masso Ramírez, Amada; López Nieto, José Manuel

    2014-01-01

    MoVTeNb mixed oxide, a highly active and selective catalyst for the oxidative dehydrogenation of ethane to produce ethylene, exhibits the so-called M1 and M2 crystalline phases. The thermal stability of the MoVTeNb catalytic system was assessed under varying reaction conditions; to this end, the catalyst was exposed to several reaction temperatures spanning from 440 to 550 °C. Both the pristine and spent materials were analyzed by several characterization techniques. The ...

  5. Making coke a more efficient catalyst in the oxidative dehydrogenation of ethylbenzene using wide-pore transitional aluminas

    Zarubina, V.; Nederlof, C.; B. VAN DER LINDEN; F. Kapteijn; Heeres, H. J.; Makkee, M.; Melián-Cabrera, I.

    2014-01-01

    The thermal activation of a silica-stabilized gamma-alumina impacts positively on the oxidative dehydrogenation of ethylbenzene (EB) to styrene (ST). A systematic thermal study reveals that the transition from gamma-alumina into transitional phases at 1050 degrees C leads to an optimal enhancement of both conversion and selectivity under pseudo-steady state conditions; where active and selective coke have been deposited. The effect is observed in the reaction temperature range of 450-475 degr...

  6. Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts

    Pham, Hien N.; Sattler, Jesper J. H. B.; Weckhuysen, Bert M.; Datye, Abhaya K.

    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. Surprising...

  7. Adsorption and dehydrogenation mechanism of methane on clean and oxygen-covered Pd (1 0 0) surfaces: A DFT study

    Highlights: • Adsorption and dehydrogenation mechanisms of methane on Pd (1 0 0) surface were studied using DFT calculations. • The optimized structures and adsorption energies were obtained. The energy barriers and reaction energies were calculated. • The presence of oxygen atom inhibited the dissociation of CHx except for CH3 group. - Abstract: Using density functional theory (DFT) together with periodic slab models, the adsorption and dehydrogenation mechanisms of methane on clean and oxygen-covered Pd (1 0 0) surfaces have been studied systematically. Different adsorption geometries were investigated for CH4 and related intermediates (CH3, CH2, CH, C, H, O and OH). It was found that CH4 and CH3 prefer to adsorb on the top site, CH2 and OH are favorable on the bridge site, while CH, C, O and H species adsorb preferentially on the hollow site. In addition, this work identified the stable co-adsorption configurations for the relevant co-adsorption groups. It was concluded that the effect of co-adsorbed oxygen atom tends to weaken the adsorbate–substrate interaction on the Pd (1 0 0) surface. Finally, transition states, energy barriers and reaction energies were determined to confirm the mechanism of dehydrogenation of CH4 on clean and oxygen-covered Pd (1 0 0) surfaces. The existence of oxygen atom increases the energy barriers obviously and inhibits the dissociation of CHx (x = 1, 2 and 4) except for CH3 group

  8. Towards understanding a mechanism for reversible hydrogen storage: theoretical study of transition metal catalysed dehydrogenation of sodium alanate.

    Ljubić, Ivan; Clary, David C

    2010-04-28

    On the basis of density functional theory and coupled-cluster CCSD(T) calculations we propose a mechanism of the dehydrogenation of transition metal doped sodium alanate. Insertion of two early 3d-transition metals, scandium and titanium, both of which are promising catalysts for reversible hydrogen storage in light metal hydrides, is compared. The mechanism is deduced from studies on the decomposition of a model system consisting of one transition metal atom and two NaAlH(4) units. Subsequently, the significance of such minimal cluster model systems to the real materials is tested by embedding the systems into the surface of the NaAlH(4) crystal. It is found that the dehydrogenation proceeds via breaking of the bridge H-Al bond and consequent formation of intermediate coordination compounds in which the H(2) molecule is side-on (eta(2)-) bonded to the transition metal centre. The total barrier to the H(2) release is thus dependent upon both the strength of the Al-H bond to be broken and the depth of the coordinative potential. The analogous mechanism applies for the recognized three successive dehydrogenation steps. The gas-phase model structures embedded into the surface of the NaAlH(4) crystal exhibit an unambiguous kinetic stability and their general geometric features remain largely unchanged. PMID:20379493

  9. Microbial transformations of steroids--IV. 6,7-Dehydrogenation; a new class of fungal steroid transformation product.

    Smith, K E; Latif, S; Kirk, D N; White, K A

    1989-08-01

    Microbial steroid dehydrogenation is quite common. The reaction seems to occur mainly in bacteria and usually results in hydrogen abstraction from positions C(1)-C(2) and/or C(4)-C(5) with occasional aromatisation of ring A. We have screened large numbers of fungal cultures for their ability to monohydroxylate steroids at unusual sites and in the course of our investigations we have identified seven fungal strains capable of dehydrogenating ring B of progesterone and androstenedione at positions C(6)-C(7). Microbiological dehydrogenation at this site seems not to have been reported previously. The structures of the metabolites isolated from progesterone, and the producing fungi, are: 6-dehydroprogesterone (Botryodiplodia theobromae), 11 alpha-hydroxy-6-dehydroprogesterone (Botryosphaerica obtusa, Mucor racemosus and Nigrospora sphaerica), 12 alpha-, 15 beta- and 16 alpha-hydroxy-6-dehydroprogesterones (B. obtusa) and 14 alpha-hydroxy-6-dehydroprogesterone (Apiocrea chrysosperma) [1]. From androstenedione we isolated 6-dehydroandrostenedione (Absidia coerulea and Curvularia lunata) and 6-dehydrotestosterone (C. lunata). PMID:2770300

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

    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

  11. Iron-Deficiency Anemia

    Full Text Available ... the body. Iron-deficiency anemia usually develops over time if your body doesn't have enough iron ... Institutes of Health—shows how Susan, a full-time worker and student, has coped with having iron- ...

  12. Iron-Deficiency Anemia

    Full Text Available ... body. Low iron levels usually are due to blood loss, poor diet, or an inability to absorb enough iron from food. Overview Iron-deficiency anemia is a common type of anemia . The term "anemia" usually refers to ...

  13. Alpha1-antitrypsin deficiency

    Stolk, Jan; Seersholm, Niels; Kalsheker, Noor

    2006-01-01

    biennially to exchange views and research findings. The fourth biennial meeting was held in Copenhagen, Denmark, on 2-3 June 2005. This review covers the wide range of AAT deficiency-related topics that were addressed encompassing advances in genetic characterization, risk factor identification, clinical...... epidemiology, inflammatory and signalling processes, therapeutic advances, and lung imaging techniques....

  14. MCAD deficiency in Denmark

    Andresen, Brage Storstein; Lund, Allan Meldgaard; Hougaard, David Michael; Christensen, Ernst; Gahrn, Birthe; Christensen, Mette; Bross, Peter; Vested, Anne; Simonsen, Henrik; Skogstrand, Kristin; Olpin, Simon; Brandt, Niels Jacob; Skovby, Flemming; Nørgaard-Pedersen, Bent; Gregersen, Niels

    2012-01-01

    Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common defect of fatty acid oxidation. Many countries have introduced newborn screening for MCADD, because characteristic acylcarnitines can easily be identified in filter paper blood spot samples by tandem mass spectrometry (MS/M...

  15. Interaction of methanol and its dehydrogenation species with Pt-alloy surfaces

    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.

  16. Spectroscopic Characterization of Lanthanum-Mediated Dehydrogenation and C-C Bond Coupling of Ethylene.

    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

  17. Catalytic propane dehydrogenation over In₂O₃–Ga₂O₃ mixed oxides

    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. (Dow); (GIT)

    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.

  18. Study of the hydrogenation/dehydrogenation process in the Mg–Ni–C–Al system

    Palumbo, O. [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Research Center Hydro-Eco, Sapienza University of Rome, Via A. Scarpa 14, 00161 Roma (Italy); Trequattrini, F. [Physics Department, Sapienza University of Rome, Piazzale A. Moro 5, 00185 Roma (Italy); Vitucci, F.M. [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Bianchin, A. [MBN Nanomaterialia S.p.A., Via G. Bortolan 42, 31040 Vascon di Carbonera-TV (Italy); Paolone, A., E-mail: annalisa.paolone@roma1.infn.it [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Research Center Hydro-Eco, Sapienza University of Rome, Via A. Scarpa 14, 00161 Roma (Italy)

    2015-10-05

    Highlights: • A Mg–Ni–C–Al mixture synthesized for application as pellets in a tank is studied. • It is the combination of a hydrogen storing composite with a binding phase. • The storage properties are studied by PCI curves, TGA–DSC and XRD. • The hydrogen absorbtion/desorption occurs in two steps. • The thermodynamics of the first more massive step is improved compared to MgH{sub 2}. - Abstract: In this work we present a detailed study of the hydrogenation and dehydrogenation processes of a nanostructured Mg–Ni–C–Al mixture. The sample has been characterized by means of X-ray diffraction, concomitant thermogravimetric and differential scanning calorimetry measurements and pressure-composition isothermal analyses. The hydrogenation takes place in two steps and is compatible with the formation of MgH{sub 2} and Mg{sub 2}NiH{sub 4}. The enthalpy and the activation energy measured for the main hydrogen desorption are lower than those ones reported for magnesium hydride.

  19. Incorporation of catalytic dehydrogenation into Fischer-Tropsch synthesis to lower carbon dioxide emissions

    Huffman, Gerald P

    2012-09-18

    A method for producing liquid fuels includes the steps of gasifying a starting material selected from a group consisting of coal, biomass, carbon nanotubes and mixtures thereof to produce a syngas, subjecting that syngas to Fischer-Tropsch synthesis (FTS) to produce a hyrdrocarbon product stream, separating that hydrocarbon product stream into C1-C4 hydrocarbons and C5+ hydrocarbons to be used as liquid fuels and subjecting the C1-C4 hydrocarbons to catalytic dehydrogenation (CDH) to produce hydrogen and carbon nanotubes. The hydrogen produced by CDH is recycled to be mixed with the syngas incident to the FTS reactor in order to raise the hydrogen to carbon monoxide ratio of the syngas to values of 2 or higher, which is required to produce liquid hydrocarbon fuels. This is accomplished with little or no production of carbon dioxide, a greenhouse gas. The carbon is captured in the form of a potentially valuable by-product, multi-walled carbon nanotubes (MWNT), while huge emissions of carbon dioxide are avoided and very large quantities of water employed for the water-gas shift in traditional FTS systems are saved.

  20. Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation.

    Kocić, Nemanja; Liu, Xunshan; Chen, Songjie; Decurtins, Silvio; Krejčí, Ondřej; Jelínek, Pavel; Repp, Jascha; Liu, Shi-Xia

    2016-05-01

    Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, the tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation. PMID:27059121

  1. OXIDATIVE DEHYDROGENATION OF PROPANE BY RARE EARTH PHOSPHATES SUPPORTED ON AL-PILC

    Carolina De Los Santos

    2012-12-01

    Full Text Available Catalytic activity in propane oxidative dehydrogenation of rare earth phosphates LnPO4 (where Ln = La, Ce, Pr, Nd, Sm and of the same supported by an aluminum pillared clay, of high specific surface area, is presented. The solids were characterized by TGA, XRD, nitrogen adsorption and immediate analysis after reaction in order to determine eventual carbon formation. Catalytic assays were performed at temperatures in the range 400oC-600oC, the reaction mixture was C3H8/O2/Ar = 10/10/80. All the catalysts were active. The reaction products were H2, CO, CO2, CH4, C2H4 and C3H6 and there were no organic oxygenated compounds detected. Although all the investigated systems were active, the Al-PILC supported catalysts presented a higher activity than the bulk materials. In this context, the samarium supported catalyst showed a propene yield increase from 4% to 10% compared with bulk samarium phosphate at 600°C. This effect was attributed to the increase in the specific surface area.

  2. Upgrading Lignocellulosic Products to Drop-In Biofuels via Dehydrogenative Cross-Coupling and Hydrodeoxygenation Sequence.

    Sreekumar, Sanil; Balakrishnan, Madhesan; Goulas, Konstantinos; Gunbas, Gorkem; Gokhale, Amit A; Louie, Lin; Grippo, Adam; Scown, Corinne D; Bell, Alexis T; Toste, F Dean

    2015-08-24

    Life-cycle analysis (LCA) allows the scientific community to identify the sources of greenhouse gas (GHG) emissions of novel routes to produce renewable fuels. Herein, we integrate LCA into our investigations of a new route to produce drop-in diesel/jet fuel by combining furfural, obtained from the catalytic dehydration of lignocellulosic pentose sugars, with alcohols that can be derived from a variety of bio- or petroleum-based feedstocks. As a key innovation, we developed recyclable transition-metal-free hydrotalcite catalysts to promote the dehydrogenative cross-coupling reaction of furfural and alcohols to give high molecular weight adducts via a transfer hydrogenation-aldol condensation pathway. Subsequent hydrodeoxygenation of adducts over Pt/NbOPO4 yields alkanes. Implemented in a Brazilian sugarcane biorefinery such a process could result in a 53-79% reduction in life-cycle GHG emissions relative to conventional petroleum fuels and provide a sustainable source of low carbon diesel/jet fuel. PMID:26216783

  3. Synthesis, spectral and catalytic dehydrogenation studies of ruthenium complexes containing NO bidentate ligands

    Shoair, A. F.; El-Bindary, A. A.

    2014-10-01

    The synthesis and characterization of ruthenium mononuclear complexes containing NO bidentate ligands are reported. The complexes cis-[RuII(bpy)2L](PF6)n (1a-c), [RuIIICl(L)2(H2O)] (2a-b) and [RuIIICl2(L)2]Cl (2c) were prepared by the reaction of cis-[RuIICl2(bpy)2]·2H2O (bpy = 2,2";-bipyridine) and/or RuCl3·nH2O with the Ligands: 2-aminophenol (2-aph), 8-hydroxyquinoline (8-hq) and 4-aminoantipyrine (4-apy). These complexes were characterized by elemental analysis, spectroscopic (IR, UV-Vis, 1H NMR, ESR) and magnetic susceptibility measurements. The ligand field parameters, Δo (splitting parameter), B (Racah parameter of interelectronic repulsion), and β (nephelauxetic ratio) were calculated. The redox properties were also investigated electrochemically by cyclic voltammetry. The complexes cis-[RuII(bpy)2(8-hq)](PF6)2 (1b) and [RuIIICl(8-hq)2(H2O)] (2b) have been investigated in conjunction with N-methylmorpholine-N-oxide (NMO) as co-oxidant for the catalytic dehydrogenation of benzyl amine, p-methyl benzylamine and p-nitrobenzylamine to their respective nitriles.

  4. Oxidative dehydrogenation of isobutyl alcohol over different structure type of zeolites

    Full text: Partial heterogen-catalytic of aliphatic alcohols is perspective method for production of important oxygen-containing compounds. Numerous of the literature data testify that the different mixed oxides of metals show the relatively high catalytic activity in the reactions of oxidation of aliphatic alcohols. Until recently however little attention had been given to the possibility of using of the modified zeolites for promoting these reactions. The present paper is devoted to oxidative dehydrogenation of isobutyl alcohol in the presence of molecular oxygen over different structure type of synthetical (A, X, Y, ZSM-5) and natural zeolites modified by cations of transition elements (Cu2+, Sn2+, Ni2+, Co2+, Fe2+ and Pd2+) for the purpose of selection of an active catalyst for production of corresponding aldehyde. For making of active catalyst on the first stage the study was carried out ever mono- and on the second stage over bimethalzeolite catalysts. It has been established that for each of zeolite has there optimum concentration of transition element cation in the dependence of structure of zeolites. It has been found that, the mono metallic catalysts on the basis of synthetical zeolites more active in this reaction than catalysts on the basis of natural zeolites. Introduction of second metal cation (Pd2+) into structure of mono metallic catalyst leaded considerable increasing of conversion of alcohol and selectivity of the process and stability of operation of catalysts

  5. Oxidative Dehydrogenation of Methanol on Chromium Oxide/Montmorillonite K10 Catalysts

    Methanol conversion was carried out on one of meso porous materials, Chromia I Montmorillonite K10 (MK10) in a pulse micro catalytic system. Methanol was converted to formaldehyde and ethylene by two different mechanisms. Methanol dehydrogenation increases by reaction temperature (300-400 degree C) and as chromia loading decrease. In contradiction, the dehydration of methanol takes place at higher temperature (400-500 degree C) and as chromia loading increase, 3-18% Cr. Redox and exposed non-redox Cr3+ are responsible for HCHO formation. There is relationship between increasing of C2H4 production and the increase of Cr+6 phase (from TPR and UV-Vis) according to the acidity of chromia catalysts 34 and 76 μL tert-Butylamine /gram catalyst for 3% Cr and 18% Cr, respectively. Formaldehyde formation is diffusional controlled at high temperature (400-500 degree C) and kinetically controlled at lower reaction temperature (300-400 degree C) while methanol dehydration to ethylene is surface reaction controlled at 400-500 degree C

  6. Glucose-6-phosphate dehydrogenase deficiency

    ... this page: //medlineplus.gov/ency/article/000528.htm Glucose-6-phosphate dehydrogenase deficiency To use the sharing features on this page, please enable JavaScript. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a condition ...

  7. Transient partial growth hormone deficiency due to zinc deficiency.

    Nishi, Y; Hatano, S; Aihara, K; Fujie, A; Kihara, M

    1989-04-01

    We present here a 13-year-old boy with partial growth hormone deficiency due to chronic mild zinc deficiency. When zinc administration was started, his growth rate, growth hormone levels, and plasma zinc concentrations increased significantly. His poor dietary intake resulted in chronic mild zinc deficiency, which in turn could be the cause of a further loss of appetite and growth retardation. There was also a possibility of renal zinc wasting which may have contributed to zinc deficiency. Zinc deficiency should be carefully ruled out in patients with growth retardation. PMID:2708733

  8. Iron deficiency and cognitive functions

    Jáuregui-Lobera I

    2014-11-01

    Full Text Available Ignacio Jáuregui-Lobera Department of Nutrition and Bromatology, Pablo de Olavide University, Seville, Spain Abstract: Micronutrient deficiencies, especially those related to iodine and iron, are linked to different cognitive impairments, as well as to potential long-term behavioral changes. Among the cognitive impairments caused by iron deficiency, those referring to attention span, intelligence, and sensory perception functions are mainly cited, as well as those associated with emotions and behavior, often directly related to the presence of iron deficiency anemia. In addition, iron deficiency without anemia may cause cognitive disturbances. At present, the prevalence of iron deficiency and iron deficiency anemia is 2%–6% among European children. Given the importance of iron deficiency relative to proper cognitive development and the alterations that can persist through adulthood as a result of this deficiency, the objective of this study was to review the current state of knowledge about this health problem. The relevance of iron deficiency and iron deficiency anemia, the distinction between the cognitive consequences of iron deficiency and those affecting specifically cognitive development, and the debate about the utility of iron supplements are the most relevant and controversial topics. Despite there being methodological differences among studies, there is some evidence that iron supplementation improves cognitive functions. Nevertheless, this must be confirmed by means of adequate follow-up studies among different groups. Keywords: iron deficiency, anemia, cognitive functions, supplementation

  9. Biotin and biotinidase deficiency

    Zempleni, Janos; Hassan, Yousef I.; Wijeratne, Subhashinee SK

    2008-01-01

    Biotin is a water-soluble vitamin that serves as an essential coenzyme for five carboxylases in mammals. Biotin-dependent carboxylases catalyze the fixation of bicarbonate in organic acids and play crucial roles in the metabolism of fatty acids, amino acids and glucose. Carboxylase activities decrease substantially in response to biotin deficiency. Biotin is also covalently attached to histones; biotinylated histones are enriched in repeat regions in the human genome and appear to play a role...

  10. Iron Deficiency Anemia

    Hassan Ahari

    1965-01-01

    Full Text Available The object of this paper is to draw attention to iron deficiency anemia which is the most common nutritional disturbance in infants and children. Iron deficiency anemia constitutes the most prevalent form of anemia in this age group. The records of infants and children admitted to the Pediatric Department of Tehran University Puhlavi Hospital for various ailments during a one year period (Mnrch l!l63 - HHi-t were analyzed. 262 infants and children out of a total number of an5, or 7t•/., showed iron deficiency anemia detect cd by blood film studies and hemoglobin determination, The majority, 123 or 4{.!t•/., of these patients were infants and children between six months and two years of age. The etiology indicates that faulty feeding is the main cause. Infections, parnsitcs, and hemorrhage were among other causes observed. ,'('itll regard to treatment, parenteral iron was preferred because cf its ef., Icctivcncss in short periods of hospital stay. In conclusion, the routine study of blood films and hemoglobin determiualion, especially in the low socio _ economic group of medically less organized countries is advised

  11. Iron-Deficiency Anemia (For Parents)

    ... Things to Know About Zika & Pregnancy Iron-Deficiency Anemia KidsHealth > For Parents > Iron-Deficiency Anemia Print A ... common nutritional deficiency in children. About Iron-Deficiency Anemia Every red blood cell in the body contains ...

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

    Ryo eWatanabe

    2013-10-01

    Full Text Available 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.

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

    Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: 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

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

    Kootenaei, A.H. Shahbazi [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Towfighi, J., E-mail: towfighi@modares.ac.ir [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Khodadadi, A.; Mortazavi, Y. [Catalysis and Nanostructured Materials Laboratory, Oil and Gas Processing Center of Excellence, Department of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of)

    2014-04-01

    Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V{sub 2}O{sub 5} 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.

  15. Modeling-based optimization of a fixed-bed industrial reactor for oxidative dehydrogenation of propane

    Ali Darvishi; Razieh Davand; Farhad Khorasheh; Moslem Fattahi

    2016-01-01

    An industrial scale propylene production via oxidative dehydrogenation of propane (ODHP) in multi-tubular re-actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of smal diameter tubes immersed in a shel through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefin over V2O5/γ-Al2O3 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa-rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100%conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run-away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl-ene production in an industrial scale reactor.

  16. In situ NMR study of hydrogenation/dehydrogenation of ZrCr2 and physisorbed hydrogen

    Highlights: ► In situ NMR study of hydrogenation of C14-ZrCr2. ► Observation of physisorbed hydrogen peak in NMR spectra. ► Change of chemical shift of physisorbed H2 (δphy) with degree of hydrogenation. ► Linearity between δphy and degree of hydrogenation. ► Linearity between degree of hydrogenation and density of states, Nd(EF). - Abstract: In situ proton nuclear magnetic resonance (NMR) was employed to study the hydrogenation and dehydrogenation kinetics of ZrCr2. The powder samples prepared by arc melting followed by homogenizing heat treatment and grinding were put inside a boron nitride (BN) crucible, which was placed inside a quartz tube attached to a high pressure assembly specially designed for in situ NMR measurements. The samples were activated at 573 K under vacuum inside the high temperature probe and then exposed to the required hydrogen gas pressure at room temperature for hydrogenation. Gradual hydrogenation of the samples was recorded through in situ NMR. Before activation of the sample, the exposure to high pressure showed two peaks with NMR shifts of 8.5 and −3.3 ppm, which were assigned to hydrogen gas and physisorbed hydrogen, respectively. After activation, the sample showed absorption manifested through the appearance of a broad peak with an NMR shift of −141 ppm. The NMR shift of absorption peak increased to higher magnetic fields as the hydrogen absorption proceeded. It was also accompanied by a change in NMR shift of physisorbed hydrogen peak in the same direction. Both the shifts, i.e., of absorbed hydrogen as well as of physisorbed hydrogen were linearly related with the degree of hydrogenation. This change in NMR shift of physisorbed hydrogen was explained on the basis of increase in density of d-electronic states at Fermi level with an increase in the absorbed hydrogen.

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

    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.

  18. Nb effect in the nickel oxide-catalyzed low-temperature oxidative dehydrogenation of ethane

    Zhu, Haibo

    2012-01-01

    A method for the preparation of NiO and Nb-NiO nanocomposites is developed, based on the slow oxidation of a nickel-rich Nb-Ni gel obtained in citric acid. The resulting materials have higher surface areas than those obtained by the classical evaporation method from nickel nitrate and ammonium niobium oxalate. These consist in NiO nanocrystallites (7-13 nm) associated, at Nb contents >3 at.%., with an amorphous thin layer (1-2 nm) of a niobium-rich mixed oxide with a structure similar to that of NiNb 2O 6. Unlike bulk nickel oxides, the activity of these nanooxides for low-temperature ethane oxidative dehydrogenation (ODH) has been related to their redox properties. In addition to limiting the size of NiO crystallites, the presence of the Nb-rich phase also inhibits NiO reducibility. At Nb content >5 at.%, Nb-NiO composites are thus less active for ethane ODH but more selective, indicating that the Nb-rich phase probably covers part of the unselective, non-stoichiometric, active oxygen species of NiO. This geometric effect is supported by high-resolution transmission electron microscopy observations. The close interaction between NiO and the thin Nb-rich mixed oxide layer, combined with possible restructuration of the nanocomposite under ODH conditions, leads to significant catalyst deactivation at high Nb loadings. Hence, the most efficient ODH catalysts obtained by this method are those containing 3-4 at.% Nb, which combine high activity, selectivity, and stability. The impact of the preparation method on the structural and catalytic properties of Nb-NiO nanocomposites suggests that further improvement in NiO-catalyzed ethane ODH can be expected upon optimization of the catalyst. © 2011 Elsevier Inc. All rights reserved.

  19. Dehydrogenation kinetics of pure and nickel-doped magnesium hydride investigated by in situ time-resolved powder X-ray diffraction

    Jensen, T.R.; Andreasen, A.; Vegge, Tejs;

    2006-01-01

    The dehydrogenation kinetics of pure and nickel (Ni)-doped (2w/w%) magnesium hydride (MgH2) have been investigated by in situ time-resolved powder X-ray diffraction (PXD). Deactivated samples, i.e. air exposed, are investigated in order to focus on the effect of magnesium oxide (MgO) surface layers...... conditions. A quartz capillary cell allowed the in situ study of gas/solid reactions. Three phases were identified: Mg, MgH2 and MgO and their phase fractions were extracted by Rietveld refinement or integration of selected reflections from each phase. Dehydrogenation curves were constructed and analysed by...... the Johnson-Mehi-Avrami formalism in order to derive rate constants at different temperatures. The apparent activation energies for dehydrogenation of pure and Ni-doped magnesium hydride were E-A approximate to 300 and 250 kJ/mol, respectively. Differential scanning calorimetry gave, E-A = 270 k...

  20. Dehydrogenation kinetics for pure and nickel-doped magnesium hydride investigated by in-situ, time-resolved powder diffraction (poster)

    Jensen, T.R.; Andreasen, A.; Vegge, T.;

    2004-01-01

    The dehydrogenation kinetics of pure and nickel-doped magnesium hydride was investigated by in-situ, time-resolved X-ray powder diffraction. A special reaction cell allowed the study of gas/solid reactions and analysis of the exhaust gas by massspectroscopy. X-ray data (0 <2è <120°) was collected...... under isothermal conditions with a time resolution of 45 s. Three phases were identified, Mg,MgH2 and MgO, and the phase fractions were extracted for each phase. Dehydrogenation curves wereconstructed and analyzed by the Johnson-Mehl-Avrami formalism in order to derive rateconstants at different....... Furthermore, the difference in apparent activation energy of ca. 50 kJ/mol compares totheoretical calculations for the atomisation of H2 molecules, which might be the rate-determining step in the dehydrogenation process....

  1. Environmentally benign synthesis of amides and ureas via catalytic dehydrogenation coupling of volatile alcohols and amines in a Pd-Ag membrane reactor

    Chen, Tao

    2016-05-31

    In this study, we report the direct synthesis of amides and ureas via the catalytic dehydrogenation of volatile alcohols and amines using the Milstein catalyst in a Pd-Ag/ceramic membrane reactor. A series of amides and ureas, which could not be synthesized in an open system by catalytic dehydrogenation coupling, were obtained in moderate to high yields via catalytic dehydrogenation of volatile alcohols and amines. This process could be monitored by the hydrogen produced. Compared to the traditional method of condensation, this catalytic system avoids the stoichiometric pre-activation or in situ activation of reagents, and is a much cleaner process with high atom economy. This methodology, only possible by employing the Pd-Ag/ceramic membrane reactor, not only provides a new environmentally benign synthetic approach of amides and ureas, but is also a potential method for hydrogen storage.

  2. Adsorption and dehydrogenation mechanism of methane on clean and oxygen-covered Pd (1 0 0) surfaces: A DFT study

    Jiang, Zhao; Wang, Bin; Fang, Tao, E-mail: taofang@mail.xjtu.edu.cn

    2014-11-30

    Highlights: • Adsorption and dehydrogenation mechanisms of methane on Pd (1 0 0) surface were studied using DFT calculations. • The optimized structures and adsorption energies were obtained. The energy barriers and reaction energies were calculated. • The presence of oxygen atom inhibited the dissociation of CH{sub x} except for CH{sub 3} group. - Abstract: Using density functional theory (DFT) together with periodic slab models, the adsorption and dehydrogenation mechanisms of methane on clean and oxygen-covered Pd (1 0 0) surfaces have been studied systematically. Different adsorption geometries were investigated for CH{sub 4} and related intermediates (CH{sub 3}, CH{sub 2}, CH, C, H, O and OH). It was found that CH{sub 4} and CH{sub 3} prefer to adsorb on the top site, CH{sub 2} and OH are favorable on the bridge site, while CH, C, O and H species adsorb preferentially on the hollow site. In addition, this work identified the stable co-adsorption configurations for the relevant co-adsorption groups. It was concluded that the effect of co-adsorbed oxygen atom tends to weaken the adsorbate–substrate interaction on the Pd (1 0 0) surface. Finally, transition states, energy barriers and reaction energies were determined to confirm the mechanism of dehydrogenation of CH{sub 4} on clean and oxygen-covered Pd (1 0 0) surfaces. The existence of oxygen atom increases the energy barriers obviously and inhibits the dissociation of CH{sub x} (x = 1, 2 and 4) except for CH{sub 3} group.

  3. Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

    Zhu, Haibo

    2015-09-01

    The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

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

    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

  5. The oxidative coupling of methane and the oxidative dehydrogenation of ethane over a niobium promoted lithium doped magnesium oxide catalyst

    Swaan, H.M.; Li, X.; Seshan, K.; Ommen, van, B.; Ross, J.R.H.

    1993-01-01

    The promoting effect of niobium in a Li/MgO catalyst for the oxidative coupling of methane (OCM) and for the oxidative dehydrogenation of ethane (ODHE) has been studied in some detail. It has been found that a Li/Nb/MgO catalyst with 16 wt % niobium showed the highest activity for the C2 production in the OCM reaction; the activity at 600 °C was ten times that of the Li/MgO catalyst at the same temperature. The Li/Nb/MgO catalyst was also slightly more active for the ODHE reaction than was th...

  6. Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature

    Mohammed H. Al-Hazmi

    2015-01-01

    Full Text Available The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C.

  7. Study on dehydrogenation properties of the LiAlH{sub 4}-NH{sub 4}Cl system

    Zheng, Xueping, E-mail: zxp2004b@yahoo.com.cn [School of Materials Science and Engineering, Chang' an University, Xi' an 710061 (China); Zheng, Jiaojiao [School of Materials Science and Engineering, Chang' an University, Xi' an 710061 (China); Ma, Qiuhua [Materials Science and Engineering Institute, Henan University of Technology, Zhengzhou 450001 (China); Liu, Shenglin; Feng, Xin; Lin, Xiaobin; Xiao, Guo [School of Materials Science and Engineering, Chang' an University, Xi' an 710061 (China)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The dehydrogenation amount of the sample with the molar ratio of 1:1 reaches to about 6.6 wt%. Black-Right-Pointing-Pointer Doping with CeO{sub 2} has raised the dehydrogenation properties of the LiAlH{sub 4}-NH{sub 4}Cl system. Black-Right-Pointing-Pointer The microstructures of LiAlH{sub 4}-NH{sub 4}Cl with different molar ratio of LiAlH{sub 4} to NH{sub 4}Cl are similar. Black-Right-Pointing-Pointer Amount of CeO{sub 2} has not caused change of microstructures of LiAlH{sub 4}-NH{sub 4}Cl doped with CeO{sub 2}. Black-Right-Pointing-Pointer Doping with CeO{sub 2} makes the flocculent microstructure of LiAlH{sub 4}-NH{sub 4}Cl more loose. - Abstract: In this work, the dehydrogenation properties of the LiAlH{sub 4}-NH{sub 4}Cl system and the LiAlH{sub 4}-NH{sub 4}Cl doped with CeO{sub 2} were analyzed by PCT (pressure-composition-temperature) equipment and SEM (Scanning Electron Microscope) analysis method. The result showed that the LiAlH{sub 4}-NH{sub 4}Cl system presented the fastest rate and the earliest starting time of hydrogen release when the molar ratio of LiAlH{sub 4} to NH{sub 4}Cl was 1:1, and the dehydrogenation amount of the sample which the molar ratio of LiAlH{sub 4} to NH{sub 4}Cl is 1:1 was very high and reached to 6.6 wt%. The study on doping with CeO{sub 2} showed that doping with CeO{sub 2} had further raised the rate and the amount of hydrogen release of the LiAlH{sub 4}-NH{sub 4}Cl system and shortened the starting time of hydrogen release. Furthermore, the result showed that doping with CeO{sub 2} made the flocculent microstructure of the LiAlH{sub 4}-NH{sub 4}Cl system more obvious and looser.

  8. ESR Characterization and Activity of V2O5/γ-Al2O3 Catalysts for Dehydrogenation of Isobutane

    2002-01-01

    The ESR spectra of catalyst V2O5/γ-Al2O3 and its activity for the dehydrogenation of isobutane were investigated. On the basis of the results of the ESR spectroscopy associated with the TPR results, it is suggested that there is a strong interaction between V2O5 and γ-Al2O3 and the V4+ species on the surface is the active center of catalyst V2O5/γ-Al2O3 for this reaction.

  9. Vanadium Oxide Supported on MSU-1 as a Highly Active Catalyst for Dehydrogenation of Isobutane with CO2

    Guosong Sun; Qingze Huang; Shiyong Huang; Qiuping Wang; Huiquan Li; Haitao Liu; Shijie Wan; Xuewang Zhang; Jinshu Wang

    2016-01-01

    Vanadium oxide supported on MSU-1, with VOx loading ranging from 2.5 to 17.5 wt. %, was developed as a highly active catalyst in dehydrogenation of isobutane with CO2. The obtained catalysts of VOx/MSU-1 were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and H2-temperature programmed reduction (H2-TPR) methods and the results showed that the large surface area of MSU-1 was favorable for the dispersion of VOx species and the optimal loading of VOx was 12.0 wt. %. Meanwhil...

  10. Catalytic B-N Dehydrogenation Using Frustrated Lewis Pairs: Evidence for a Chain-Growth Coupling Mechanism.

    Mo, Zhenbo; Rit, Arnab; Campos, Jesús; Kolychev, Eugene L; Aldridge, Simon

    2016-03-16

    The catalytic dehydrogenation of ammonia- and amine-boranes by a dimethylxanthene-derived frustrated Lewis pair is described. Turnover is facilitated on a thermodynamic basis by the ready release of H2 from the weakly basic PPh2-containing system. In situ NMR studies and the isolation of intermediates from stoichiometric reactions support a mechanism initiated by B-H activation, followed by end-growth BN coupling involving the terminal NH bond of the bound BN fragment and a BH bond of the incoming borane monomer. PMID:26918906

  11. Oxidative dehydrogenation of propane with K-MoO3/MgAl2O4 catalysts

    Serkan Naci Koc; Kubra Dayioglu; Hasan Ozdemir

    2016-01-01

    In this study, for the first time, MoO3/MgAl2O4 catalysts and their potassium-promoted forms were prepared and tested for oxidative dehydrogenation of propane. Catalysts were characterized with XRD, BET, NH3-TPD, TPR and XPS methods. Catalytic activity measurement was done with quartz microreactor between 450 and 550°C. It has been observed that the conversion of propane increased with temperature and total hydrocarbon selectivity increased with molybdenum oxide content. The acidity of catalysts decreased with potassium addition due to interaction with MoO3 sites. For this reason total hydrocarbon selectivity highly increased.

  12. Metal-Free Dehydrogenation of Formic Acid to H2 and CO2 Using Boron-Based Catalysts

    Chauvier, Clément; Tlili, Anis; Das Neves Gomes, Christophe; Thuéry, Pierre; Cantat, Thibault

    2015-01-01

    Formic acid is at the crossroads of novel sustainable energy strategies because it is an efficient H2 carrier. Yet, its decomposition to H2 today relies on metal-based catalysts. Herein, we describe the first metal-free catalysts able to promote the dehydrogenation of formic acid. Using dialkylborane derivatives, HCOOH is decomposed to H2 and CO2, in the presence of a base, with high selectivity. Experimental and computational results point to the involvement of bis(formyloxy)borates as key i...

  13. Coupling dehydrogenation of isobutane in the presence of carbon dioxide over chromium oxide supported on active carbon

    Jian Fei Ding; Zhang Feng Qin; Xue Kuan Li; Guo Fu Wang; Jian Guo Wang

    2008-01-01

    The dehydrogenation of isobutane (IB) to produce isobutene coupled with reverse water gas shift in the presence of carbon dioxide was investigated over the catalyst Cr2O3 supported on active carbon (Cr2O3/AC). The results illustrated that isobutane c onversion and isobutene yield can be enhanced through the reaction coupling in the presence of carbon dioxide. Moreover, carbon dioxide can partially eliminate carbonaceous deposition on the catalyst and keep the active phase (Cr2O3), which are then helpful to alleviate the catalyst deactivation.

  14. Treatment of carnitine deficiency.

    Winter, S C

    2003-01-01

    Carnitine deficiency is a secondary complication of many inborn errors of metabolism. Pharmacological treatment with carnitine not only corrects the deficiency, it facilitates removal of accumulating toxic acyl intermediates and the generation of mitochondrial free coenzyme A (CoA). The United States Food and Drug Administration (US FDA) approved the use of carnitine for the treatment of inborn errors of metabolism in 1992. This approval was based on retrospective chart analysis of 90 patients, with 18 in the untreated cohort and 72 in the treated cohort. Efficacy was evaluated on the basis of clinical and biochemical findings. Compelling data included increased excretion of disease-specific acylcarnitine derivatives in a dose-response relationship, decreased levels of metabolites in the blood, and improved clinical status with decreased hospitalization frequency, improved growth and significantly lower mortality rates as compared to historical controls. Complications of carnitine treatment were few, with gastrointestinal disturbances and odour being the most frequent. No laboratory or clinical safety issues were identified. Intravenous carnitine preparations were also approved for treatment of secondary carnitine deficiency. Since only 25% of enteral carnitine is absorbed and gastrointestinal tolerance of high doses is poor, parenteral carnitine treatment is an appealing alternative therapeutic approach. In 7 patients treated long term with high-dose weekly to daily venous boluses of parenteral carnitine through a subcutaneous venous port, benefits included decreased frequency of decompensations, improved growth, improved muscle strength and decreased reliance on medical foods with liberalization of protein intake. Port infections were the most troubling complication. Theoretical concerns continue to be voiced that carnitine might result in fatal arrhythmias in patients with long-chain fat metabolism defects. No published clinical studies substantiate these

  15. Carnitine palmitoyltransferase II deficiency

    Roe, C R.; Yang, B-Z; Brunengraber, H; Roe, D S.; Wallace, M; Garritson, B K.

    2008-01-01

    Background: Carnitine palmitoyltransferase II (CPT II) deficiency is an important cause of recurrent rhabdomyolysis in children and adults. Current treatment includes dietary fat restriction, with increased carbohydrate intake and exercise restriction to avoid muscle pain and rhabdomyolysis. Methods: CPT II enzyme assay, DNA mutation analysis, quantitative analysis of acylcarnitines in blood and cultured fibroblasts, urinary organic acids, the standardized 36-item Short-Form Health Status survey (SF-36) version 2, and bioelectric impedance for body fat composition. Diet treatment with triheptanoin at 30% to 35% of total daily caloric intake was used for all patients. Results: Seven patients with CPT II deficiency were studied from 7 to 61 months on the triheptanoin (anaplerotic) diet. Five had previous episodes of rhabdomyolysis requiring hospitalizations and muscle pain on exertion prior to the diet (two younger patients had not had rhabdomyolysis). While on the diet, only two patients experienced mild muscle pain with exercise. During short periods of noncompliance, two patients experienced rhabdomyolysis with exercise. None experienced rhabdomyolysis or hospitalizations while on the diet. All patients returned to normal physical activities including strenuous sports. Exercise restriction was eliminated. Previously abnormal SF-36 physical composite scores returned to normal levels that persisted for the duration of the therapy in all five symptomatic patients. Conclusions: The triheptanoin diet seems to be an effective therapy for adult-onset carnitine palmitoyltransferase II deficiency. GLOSSARY ALT = alanine aminotransferase; AST = aspartate aminotransferase; ATP = adenosine triphosphate; BHP = β-hydroxypentanoate; BKP = β-ketopentanoate; BKP-CoA = β-ketopentanoyl–coenzyme A; BUN = blood urea nitrogen; CAC = citric acid cycle; CoA = coenzyme A; CPK = creatine phosphokinase; CPT II = carnitine palmitoyltransferase II; LDL = low-density lipoprotein; MCT

  16. Antithrombin deficiency in pregnancy.

    Durai, Shivani; Tan, Lay Kok; Lim, Serene

    2016-01-01

    We present a case of a 39-year-old, gravida 3 para 2, Chinese female with a history of inherited type 1 Antithrombin deficiency and multiple prior episodes of venous thromboembolism. She presented at 29+4 weeks' gestation with severe pre-eclampsia complicated by haemolysis, elevated liver enzymes and low platelet (HELLP) syndrome. She subsequently underwent an emergency caesarean section for non-reassuring fetal status, which was complicated by postpartum haemorrhage secondary to uterine atony, requiring a B-Lynch suture intraoperatively. PMID:27207982

  17. Nasal Tip Deficiency.

    Cerkes, Nazim

    2016-01-01

    Nasal tip deficiency can be congenital or secondary to previous nasal surgeries. Underdeveloped medial crura usually present with underprojected tip and lack of tip definition. Weakness or malposition of lateral crura causes alar rim retraction and lateral nasal wall weakness. Structural grafting of alar cartilages strengthens the tip framework, reinforces the disrupted support mechanisms, and controls the position of the nasal tip. In secondary cases, anatomic reconstruction of the weakened or interrupted alar cartilages and reconstitution of a stable nasal tip tripod must be the goal for a predictable outcome. PMID:26616702

  18. Protonation and Dehydrogenation During the Multiphoton Ionization of the Cluster: C4H5N(H2O)n

    2001-01-01

    Multiphoton ionization (MPI) of the hydrogen-bonded clusters C4H5N-(H2O)m was studied with a time of flight (TOF) mass spectrometer at 355 nm. Series of the pyrrole-water cluster ions were observed, including unprotonated cluster ions [C4H5N-(H2O)n]+, protonated cluster ions [C4H5N-(H2O)nH]+ and dehydrogenated cluster ions [C4H4N-(H2O)n]+. Both the experimental and ab initio calculated results agree with that the dehydrogenation has more probabilities to occur while the value of n is raised

  19. Glucose-6-phosphatase deficiency

    Labrune Philippe

    2011-05-01

    Full Text Available Abstract Glucose-6-phosphatase deficiency (G6P deficiency, or glycogen storage disease type I (GSDI, is a group of inherited metabolic diseases, including types Ia and Ib, characterized by poor tolerance to fasting, growth retardation and hepatomegaly resulting from accumulation of glycogen and fat in the liver. Prevalence is unknown and annual incidence is around 1/100,000 births. GSDIa is the more frequent type, representing about 80% of GSDI patients. The disease commonly manifests, between the ages of 3 to 4 months by symptoms of hypoglycemia (tremors, seizures, cyanosis, apnea. Patients have poor tolerance to fasting, marked hepatomegaly, growth retardation (small stature and delayed puberty, generally improved by an appropriate diet, osteopenia and sometimes osteoporosis, full-cheeked round face, enlarged kydneys and platelet dysfunctions leading to frequent epistaxis. In addition, in GSDIb, neutropenia and neutrophil dysfunction are responsible for tendency towards infections, relapsing aphtous gingivostomatitis, and inflammatory bowel disease. Late complications are hepatic (adenomas with rare but possible transformation into hepatocarcinoma and renal (glomerular hyperfiltration leading to proteinuria and sometimes to renal insufficiency. GSDI is caused by a dysfunction in the G6P system, a key step in the regulation of glycemia. The deficit concerns the catalytic subunit G6P-alpha (type Ia which is restricted to expression in the liver, kidney and intestine, or the ubiquitously expressed G6P transporter (type Ib. Mutations in the genes G6PC (17q21 and SLC37A4 (11q23 respectively cause GSDIa and Ib. Many mutations have been identified in both genes,. Transmission is autosomal recessive. Diagnosis is based on clinical presentation, on abnormal basal values and absence of hyperglycemic response to glucagon. It can be confirmed by demonstrating a deficient activity of a G6P system component in a liver biopsy. To date, the diagnosis is most

  20. Iron Deficiency and Bariatric Surgery

    Ignacio Jáuregui-Lobera

    2013-01-01

    It is estimated that the prevalence of anaemia in patients scheduled for bariatric surgery is higher than in the general population and the prevalence of iron deficiencies (with or without anaemia) may be higher as well. After surgery, iron deficiencies and anaemia may occur in a higher percentage of patients, mainly as a consequence of nutrient deficiencies. In addition, perioperative anaemia has been related with increased postoperative morbidity and mortality and poorer quality of life aft...

  1. Iatrogenic limbal stem cell deficiency.

    Holland, E J; Schwartz, G S

    1997-01-01

    PURPOSE: To describe a group of patients with limbal stem cell (SC) deficiency without prior diagnosis of a specific disease entity known to be causative of SC deficiency. METHODS: We performed a retrospective review of the records of all patients with ocular surface disease presenting to the University of Minnesota between 1987 and 1996. Patients were categorized according to etiology of limbal deficiency. Patients who did not have a specific diagnosis previously described as being causative...

  2. Zinc deficiency and eating disorders.

    Humphries, L; Vivian, B; Stuart, M; McClain, C J

    1989-12-01

    Decreased food intake, a cyclic pattern of eating, and weight loss are major manifestations of zinc deficiency. In this study, zinc status was evaluated in 62 patients with bulimia and 24 patients with anorexia nervosa. Forty percent of patients with bulimia and 54% of those with anorexia nervosa had biochemical evidence of zinc deficiency. The authors suggest that for a variety of reasons, such as lower dietary intake of zinc, impaired zinc absorption, vomiting, diarrhea, and binging on low-zinc foods, patients with eating disorders may develop zinc deficiency. This acquired zinc deficiency could then add to the chronicity of altered eating behavior in those patients. PMID:2600063

  3. Ru-N-C Hybrid Nanocomposite for Ammonia Dehydrogenation: Influence of N-doping on Catalytic Activity

    Nguyen Thi Bich Hien

    2015-06-01

    Full Text Available For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl3·6H2O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH3 conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity.

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

    Chen, Shu; Ma, Fei; Xu, Aixin [Institute of Catalysis, Zhejiang University (Xixi Campus), Hangzhou 310028 (China); Wang, Lina [Key Laboratory of Advanced Textile Materials and Manufacturing Technology (Zhejiang Sci-tech University), Hangzhou 310012 (China); Chen, Fang [Institute of Catalysis, Zhejiang University (Xixi Campus), Hangzhou 310028 (China); Lu, Weimin, E-mail: luweimin@zju.edu.cn [Institute of Catalysis, Zhejiang University (Xixi Campus), Hangzhou 310028 (China)

    2014-01-15

    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 ZrO{sub 2}. 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 ZrV{sub 0.01} catalyst showed good conversion and selectivity with a yield of propylene of 21.3%.

  5. Ultrafast Bulk Diffusion of AlHxin High-Entropy Dehydrogenation Intermediates of NaAlH4

    Zhang, Feng [Ames Laboratory; Wood, Brandon C [Lawrence Livermore National Laboratory; Wang, Yan [Georgia Institute of Technology; Wang, Cai-Zhuang [Ames Laboratory; Ho, Kai-Ming [Ames Laboratory; Chou, Mei-Yin [Georgia Institute of Technology

    2014-08-14

    Using first-principles molecular dynamics (FPMD) and total-energy calculations, we demonstrate low-barrier bulk diffusion of Al-bearing species in γ-NaAlH4, a recently proposed high-entropy polymorph of NaAlH4. For charged AlH4– and neutral AlH3 vacancies, the computed barriers for diffusion are <0.1 eV, and we directly observe the predicted diffusive pathways in FPMD simulations at picosecond time scales. In contrast, such diffusion in the α phase is inaccessible to FPMD, consistent with much higher barriers. The transport behavior of γ-NaAlH4, in addition to key dynamical and structural signatures, is consistent with experimental observations of high-mobility species, strongly supporting the idea that an intermediate transition from the α phase to a high-entropy polymorph facilitates the hydrogen-releasing decomposition of NaAlH4. Our results provide an answer to longstanding questions regarding the responsible agent for the experimentally observed efficient Al transport during dehydrogenation and suggest that mass transport and phase transformation kinetics are coupled. Implications for understanding the (de)hydrogenation of undoped and catalyzed NaAlH4 are discussed.

  6. A DFT study on the possibility of using boron nitride nanotubes as a dehydrogenation catalyst for methanol

    Esrafili, Mehdi D., E-mail: esrafili@maragheh.ac.ir; Nurazar, Roghaye

    2014-09-30

    Graphical abstract: The most stable complex of CH{sub 3}OH and BNNT. - Highlights: • The adsorption and dissociative reaction of CH{sub 3}OH on the BNNT is investigated. • Five adsorption types and four reaction pathways are identified. • The O–H bond scission is the most favorable pathway of CH{sub 3}OH decomposition on the BNNT surface. - Abstract: The adsorption and subsequent dissociative dehydrogenation reaction of methanol (CH{sub 3}OH) on (6,0) zigzag boron nitride nanotube (BNNT) are investigated using the density functional theory calculations. Five adsorption types and four reaction channels are identified. The calculated adsorption energies range from −1.4 to −21.9 kcal/mol. The results indicate that O–H bond scission is the most favorable pathway on the tube surface. It is predicted that on the surface of the BNNT, the rate-determining step is the dehydrogenation of adsorbed OCH{sub 3}. The activation energy barrier for generation of a H{sub 2} molecule and its subsequent desorption from the surface is approximately 28 kcal/mol. The side reaction that generates CH{sub 3} and OH fragments is exothermic by −1.6 kcal/mol with an energy-barrier height of 58 kcal/mol.

  7. A New Solid Sorbent System for Rapid Monitoring of Dehydrogenated Nicotine by Using Furfural-hydrochloric Acid

    B. AMBADE; E. K. JANGHEL; M. K. RAI; G. L. MUNDHARA

    2006-01-01

    A new solid sorbent system is developed for the monitoring of dehydrogenated nicotine in the environment. The reagent system for the indicator tube consists of furfural-hydrochloric acid and phosphoric acid impregnated over a cellulose fibre (cotton) and a humectant calcium chloride. The reagent system has also been used for the preparation of reagent paper. After exposing the indicator tubes and test paper to dehydrogenated nicotine, for a constant time, the red-violet colour developed could be compared with those obtained from standards. Alternatively the coloured compound was extracted in water and the absorbance measured at 540 nm. The lower limit of detection is 0.03 μg/m3 of nicotine for the reagent papers and indicator tubes. The lower limit of determination by spectrophotometric procedure is 0.001 μg/m3 of air.The preparation of indicator tubes, test papers and their applications for the detection and determination of nicotine in environmental tobacco smoke (ETS), mainstream smoke (MS), side stream smoke (SS) and biological samples is described in this paper.

  8. Vanadium Oxide Supported on MSU-1 as a Highly Active Catalyst for Dehydrogenation of Isobutane with CO2

    Guosong Sun

    2016-03-01

    Full Text Available Vanadium oxide supported on MSU-1, with VOx loading ranging from 2.5 to 17.5 wt. %, was developed as a highly active catalyst in dehydrogenation of isobutane with CO2. The obtained catalysts of VOx/MSU-1 were characterized by X-ray diffraction (XRD, N2 adsorption-desorption, and H2-temperature programmed reduction (H2-TPR methods and the results showed that the large surface area of MSU-1 was favorable for the dispersion of VOx species and the optimal loading of VOx was 12.0 wt. %. Meanwhile, the catalytic activity of VOx/MSU-1 was investigated, and VOx/MSU-1 with 12.0 wt. % VOx content was found to be the best one, with the conversion of isobutane (58.8% and the selectivity of isobutene (78.5% under the optimal reaction conditions. In contrast with the reaction in the absence of CO2, the presence of CO2 in the reaction stream could obviously enhance the isobutane dehydrogenation, which raised the conversion of reaction and the stability of VOx/MSU-1.

  9. Cu, Fe, or Ni doped molybdenum oxide supported on Al2O3 for the oxidative dehydrogenation of ethylbenzene

    Tiago Pinheiro Braga; Antônio Narcísio Pinheiro; Edson R. Leite; Regina Cláudia R. dos Santos; Antoninho Valentini

    2015-01-01

    Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was sup-ported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dis-persed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet im-pregnation did not affect the texture of the support. TPR results indicated a synergistic effect be-tween the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conver-sion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.

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

    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%.

  11. VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

    Zhu, Haibo

    2015-09-07

    The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    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

  13. Microcalorimetric Adsorption of Alumina Oxide Catalysts for Combination of Ethylbenzene dehydrogenation and carbon Dioxide Shift-reaction

    GE Xin; SHEN Jian-yi

    2004-01-01

    Styrene (STY) is now produced industrially in fairly large quantities by the dehydrogenation of ethylbenzene (EB) using promoted iron oxide catalyst with superheated steam.In this case, small amount of carbon dioxide formed as a by-product was known to inhibit the catalytic activity of commercial catalyst. Recently, there have been some reports which carbon dioxide showed positive effects to promote catalytic activities on the reaction over several catalysts.In this study, we attempted to combine the dehydrogenation of EB to STY with the carbon dioxide shift-reaction. The combine reaction (EB + CO2 → STY + H2O + CO) can be considered as one of the ways of using CO2 resources and can yield simultaneously STY and Carbon oxide.Alumina oxide catalysts such as Al2O3, Na2O/Al2O3 and K2O/Al2O3 were prepared by the usual impregnation method with an aqueous solution of NaNO3 and KNO3, and then calcined at 650℃ for 5 h in a stream of air. The reaction condition is 600℃, flow of CO2 38ml/mon and space velocity (EB) 1.28h-1.

  14. Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

    Jacques C. Védrine

    2016-01-01

    Full Text Available This paper presents an overview of heterogeneous partial (ammoxidation and oxidative dehydrogenation (ODH of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the “seven pillars”, and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms, Me–O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C1–C4 oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(SbNb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (ammoxidation to (acrylonitrile acrylic acid on MoVTe(SbNb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO2P2O7-based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until

  15. Mechanistic and kinetic analysis of the oxidative dehydrogenation of ethane via novel supported alkali chloride catalysts

    Gaertner, C.; Veen, A.C. van; Lercher, J.A. [Technische Universitaet Muenchen (Germany). Catalysis Research Center

    2013-11-01

    The oxidative dehydrogenation of ethane over advanced catalysts is promising to selectively produce ethylene, an essential building block for the chemical industry. In this way, ethane from shale gas can be efficiently valorized. Supported alkali chloride catalysts are investigated in this work. Essential feature of those materials is the presence of a solid core (magnesium oxide in part doped with Dy{sub 2}O{sub 3}) covered under reaction conditions with a molten alkali chloride shell. It is shown that especially the lowered melting point of eutectic mixtures of LiCl with other alkali/alkaline earth metals is the key to taylor highly efficient materials. Elucidating the ODH reaction mechanism is essential to understand the reactivity of this novel catalyst class and provides the basis for improving performances. Information about elementary steps and the rate determining step were extracted from kinetic measurements, both in steady state and in transient configuration. Furthermore, isotopic labelling studies were performed, i.e. SSITKA studies and temperature programmed isotopic exchange experiments. Step experiments showed a significant oxygen uptake by the catalysts. Retained oxygen reacted quantitatively with ethane at nearly 100% selectivity to ethylene and conversion rates were comparable with rates observed during steady state operation. Thus, chemically bound oxygen in the melt is the active and selective intermediate in the ODH. Therefore, it is required to consider an intermediate and the activation is concluded to relate to the oxygen dissociation. The total concentration of stored oxygen can be correlated to the steady-state activity, while the viscosity of the melts mainly influences the selectivity towards ethene. Properties of the solid core impact on the catalyst efficiency suggesting that the oxygen species forms at the interface between support and overlayer. The quantity of retained oxygen additionally depends on the properties of the chloride

  16. Mo-V-Te-Nb oxides as catalysts for ethene production by oxidative dehydrogenation of ethane

    Hartmann, D. [Technische Universitaet Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center; Meiswinkel, A.; Thaller, C.; Bock, M.; Alvarado, L. [Linde AG, Pullach (Germany)

    2013-11-01

    The availability of ethane in shale gas, as well as the interest in valorising previously underutilized carbon feedstocks, makes the oxidative dehydrogenation (ODH) of ethane an attractive alternative to the industrially established processes for production of ethylene. Mo-V-Te-Nb mixed oxide has been chosen as catalyst for the ODH reaction in view of its outstanding ability to activate alkane molecules. Catalytic test results showed that this type of catalyst can selectively oxidize ethane to ethene at moderate temperatures (350-400 C) with minor production of CO{sub x}. The catalytic performance of Mo-V-Te-Nb mixed-oxide is mainly attributable to the crystalline phase 'M1'. Rietveld analysis of the X-Ray diffractograms allowed us to quantify the amount of MoVTeNb oxide that has crystallized as M1. In this way, it was possible to find a linear correlation of the reaction rate with the abundance of M1 in the solid. Therefore, it is clear that for improving the efficiency of MoVTeNb oxide in ODH, the amount of M1 in the catalyst should be maximized. With this purpose, several MoVTeNb oxides were subject to different thermal treatments prior to the catalytic test. Structural changes in the catalyst were monitored by in-situ XRD technique. Under oxidative atmosphere, it was observed a recrystallization of M2 and possibly, amorphous oxide, into M1 phase, leading to correspondingly more active and selective catalysts (selectivities above 95 % for ethane conversions up to 40 % under industrially relevant conditions). The active site of M1 involves V species, likely with redox properties enhanced by the proximity of Mo and Te species, while the function of the crystalline structure itself is to provide the spatial configuration that allows interaction between these species. However, ethene formation rate was observed to be independent of the V content of the samples. The vanadium species exposed at the surface were studied by LEIS and by IR spectroscopy of CO

  17. Dehydrogenation inhibition on nano-Au/ZSM-5 catalyst: a novel route for anti-coking in methanol to propylene reaction.

    Sun, Chao; Yang, Yisu; Du, Junming; Qin, Feng; Liu, Zhipan; Shen, Wei; Xu, Hualong; Tang, Yi

    2012-06-11

    A novel route for anti-deactivation of methanol-to-propylene catalyst has been established through supporting nano-gold on ZSM-5, which efficiently reinforces the catalytic stability due to the effect of gold nanoparticles on the stabilization of dehydrogenation intermediates within the coking process. PMID:22549078

  18. Dehydrogenation of cyclohexane to benzene on lanthanide catalysts formed by thermal decomposition of Eu or Yb metal solutions in liquid ammonia

    Full text: Active lanthanide catalysts for the dehydrogenation of cyclohexane to benzene were prepared by impregnation of active carbon (AC) or MnO with liquid ammonia solutions of lanthanide (Ln: Eu or Yb) metals. The catalytic properties of the lanthanide catalysts varied markedly with changes in evacuation temperatures of Ln/AC and Ln/MnO during their pre-treatment. Yb/AC and Yb/MnO which were subjected to the evacuation treatment around 773 K and 673 K, respectively, showed a maximal activity and the catalysts thus treated could effectively dehydrogenated cyclohexane to benzene at 473 K. For Ln/AC, the europium and ytterbium catalysts exhibited similar activities. Studies of x-ray diffraction and Fourier-transform infrared spectra for Ln/AC showed that the lanthanides deposited on active carbon were changed through varied steps (metal, amide, imide or nitride) by the thermal treatments and simultaneously the dehydrogenation activity varied markedly. It was concluded that imide or imide-like spices formed during the thermal decomposition processes of lanthanide amide to nitride were active for the dehydrogenation. The dependence of activity on such thermal treatments was similar to that observed for the hydrogenation of olefin

  19. Operando UV-Vis spectroscopy of a catalytic solid in a pilos-scale reactor: deactivation of a CrOx/Al2O3 propane dehydrogenation catalyst

    Sattler, J.J.H.B.; Gonzalez-Jimenez, I.D.; Mens, A.J.M.; Arias, M.J.; Visser, T.; Weckhuysen, B. M.

    2013-01-01

    A novel operando UV-Vis spectroscopic set-up has been constructed and tested for the investigation of catalyst bodies loaded in a pilot-scale reactor under relevant reaction conditions. Spatiotemporal insight into the formation and burning of coke deposits on an industrial CrOx/Al2O3 catalyst during propane dehydrogenation has been obtained.

  20. Advances in the promoters of Pt-based catalysts for propane dehydrogenation%铂系丙烷脱氢催化剂助剂研究进展

    马占华; 张慧; 李军; 薛沙; 孙兰义; 刘雪暖

    2011-01-01

    Platinum-based catalysts for propane dehydrogenation have problems of poor long-term stability and low selectivity. The performance of the dehydrogenation catalysts can be greatly improved by adding additives. The recent research progress in the platinum-based catalysts promoters and the action mechanism are reviewed in this paper. The effects of alkali metals, alkaline-earth metals, rare earth metals and transition metals as promoters on the Pt-based catalysts for propane dehydrogenation are summarized. The perspective for future research of the Pt-based catalysts for propane dehydrogenation is also presented.%铂基催化剂用于丙烷催化脱氢的主要缺点是稳定性差、选择性低,通过添加助剂可以大大改善该催化剂的脱氢性能.针对催化剂助剂,综述了铂基丙烷脱氢催化剂的研究现状,分别介绍了碱金属、碱土金属、稀土金属和过渡金属作为助剂对铂基催化剂的影响,探讨了所添加助剂的作用机制,并对铂基催化剂研究前景进行了展望.

  1. Hydroformylation of olefins and reductive carbonylation of aryl halides with syngas formed ex situ from dehydrogenative decarbonylation of hexane-1,6-diol

    Christensen, Stig Holden; Olsen, Esben Paul Krogh; Rosenbaum, Jascha;

    2014-01-01

    A variety of primary alcohols have been investigated as convenient substrates for the ex situ delivery of carbon monoxide and molecular hydrogen in a two-chamber reactor. The gaseous mixture is liberated in one chamber by an iridium-catalysed dehydrogenative decarbonylation of the alcohol and then...

  2. Synergistic effect of Ti and F co-doping on dehydrogenation properties of MgH{sub 2} from first-principles calculations

    Zhang, J., E-mail: zj4343@126.com [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114 (China) and Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Changsha 410004 (China); Huang, Y.N. [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Mao, C. [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114 (China); Peng, P. [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer The co-incorporation of Ti and F into MgH{sub 2} lattice is energetically favorable. Black-Right-Pointing-Pointer The incorporated Ti and F in MgH{sub 2} preferably generate TiH{sub 2} and MgF{sub 2}, respectively. Black-Right-Pointing-Pointer The synergistic effect of Ti and F is superior to that of pure Ti. Black-Right-Pointing-Pointer The weakened interactions of Mg-H explain enhanced dehydrogenation properties. - Abstract: The energetic and electronic properties of MgH{sub 2} co-doped with Ti and F are investigated using first-principles calculations based on density functional theory. The calculation results show that incorporation of Ti combined with F atoms into MgH{sub 2} lattice is energetically favorable relative to single incorporation of Ti atom. After dehydrogenation, the co-doped Ti and F in MgH{sub 2} preferably generate TiH{sub 2} and MgF{sub 2}, respectively. Comparatively, the combined effect of Ti and F in improving the dehydrogenation properties of MgH{sub 2} is superior to that of pure Ti. These results provide a reasonable explanation for experimental observations. Analysis of electronic structures suggests the enhanced dehydrogenation properties of doped MgH{sub 2} can be attributed to the weakened bonding interactions between Mg and H due to foreign species doping.

  3. A kinetic rate expression for the time-dependent coke formation rate during propane dehydrogenation over a platinum alumina monolithic catalyst.

    Sint Annaland, van M.; Kuipers, J.A.M.; Swaaij, van W.P.M.

    2001-01-01

    Coke formation rates under propane dehydrogenation reaction conditions on a used monolithic Pt/y-Al2O3 catalyst have been experimentally determined in a thermogravimetric analyser (TGA) as a function of time on stream covering wide temperature and concentration ranges. For relatively short times on

  4. Influence of the Pressure on the Product Distribution in the Oxidative Dehydrogenation of Propane over a Ga2O3/MoO3 Catalyst

    Kotanjac, Zeljko S.; Niederer, John P.M.; Versteeg, Geert F.

    2007-01-01

    The yields and selectivities in both the catalyzed and non-catalyzed oxidative dehydrogenation of propane were found to increase with increasing pressure. The results showed that the maximum yields of valuable ODH products could be obtained by adjusting only reactants' partial pressure, while keeping their ratio constant.

  5. Solid-Solid heterogeneous catalysis: the role of potassium in promoting the dehydrogenation of the Mg(NH(2))(2)/2 LiH composite.

    Wang, Jianhui; Chen, Ping; Pan, Hongge; Xiong, Zhitao; Gao, Mingxia; Wu, Guotao; Liang, Chu; Li, Cao; Li, Bo; Wang, Jieru

    2013-11-01

    Considerable efforts have been devoted to the catalytic modification of hydrogen storage materials. The K-modified Mg(NH2 )2 /2 LiH composite is a typical model for such studies. In this work, we analyze the origin of the kinetic barrier in the first step of the dehydrogenation and investigate how K catalyzes this heterogeneous solid-state reaction. Our results indicate that the interface reaction of Mg(NH2 )2 and LiH is the main source of the kinetic barrier at the early stage of the dehydrogenation for the intensively ball-milled Mg(NH2 )2 /2 LiH sample. K can effectively activate Mg(NH2 )2 as well as promote LiH to participate in the dehydrogenation. Three K species of KH, K2 Mg(NH2 )4 , and Li3 K(NH2 )4 likely transform circularly in the dehydrogenation (KH↔K2 Mg(NH2 )4 ↔KLi3 (NH2 )4 ), which creates a more energy-favorable pathway and thus leads to the overall kinetic enhancement. This catalytic role of K in the amide/hydride system is different from the conventional catalysis of transition metals in the alanate system. PMID:23913537

  6. Activation of the C-H bond: catalytic hydroxylation of hydrocarbons by new cobaltic alkylperoxydic complexes; selective and catalytic cycloalkane dehydrogenation in presence of uranium for hydrogen transfer

    The aim of the thesis is to improve efficiency and selectivity of chemical reactions for alkane transformations. In the first part decomposition of hydroperoxides and hydrocarbon hydroxylation by cobalt complexes is studied. In the second part cycloalkanes are dehydrogenated into aromatics with a Pt catalyst, trapping hydrogen by uranium. Uranium hydride UH3 can yield very pure hydrogen at reasonable temperature

  7. Cleft palate and gonadotrophin deficiency.

    Gillis, P H; Peeters, R.

    1984-01-01

    A boy who had previously had a cleft lip and palate repaired and bilateral orchiopexies presented at 16 years of age with delayed puberty. Isolated gonadotrophin deficiency and testicular hyporesponsiveness to human chorionic gonadotrophin were found. The possibility of bilateral cryptorchidism due to gonadotrophin deficiency should be considered in boys with either cleft lip or palate, or both.

  8. Mitigation of degradation in the dehydrogenation behavior of air-exposed MgH{sub 2} catalyzed with NbF{sub 5}

    Park, Mirae [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Shim, Jae-Hyeok, E-mail: jhshim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Lee, Young-Su [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Im, Yeon Ho [School of Chemical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Cho, Young Whan [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

    2013-10-25

    Highlights: •NbF{sub 5} mitigates the degradation in dehydrogenation behavior of air-exposed MgH{sub 2}. •NbF{sub 5} lowers the activation energy for dehydrogenation reaction of air-exposed MgH{sub 2}. •NbF{sub 5} retards the formation of hydroxide layers on air-exposed MgH{sub 2} surfaces. -- Abstract: This paper addresses the dehydrogenation behavior of MgH{sub 2} exposed to air for up to 24 h at room temperature, focusing on the effect of the addition of a small amount of NbF{sub 5} and Nb{sub 2}O{sub 5} as a catalytic additive. Although the dehydrogenation reaction of MgH{sub 2} with no catalytic additive and Nb{sub 2}O{sub 5} is significantly retarded after air exposure compared with unexposed samples, the degradation in the dehydrogenation behavior of MgH{sub 2} with NbF{sub 5} due to air exposure is found to be effectively mitigated. Although differential scanning calorimetry of the air-exposed samples indicates that the activation energy for the dehydrogenation reaction significantly increases after air exposure, the activation energy for MgH{sub 2} with NbF{sub 5} remains the lowest. Scanning electron microscopy with energy dispersive X-ray spectroscopy shows that the amount of oxygen on the surfaces of air-exposed MgH{sub 2} particles catalyzed with NbF{sub 5} is much lower than that of air-exposed MgH{sub 2} with no catalytic additive and Nb{sub 2}O{sub 5.} This implies that the addition of NbF{sub 5} forms protective layers on the surfaces of MgH{sub 2} particles against oxygen and moisture in the air, which seems to be responsible for the positive effect of NbF{sub 5} on the degradation of the dehydrogenation behavior of air-exposed MgH{sub 2}.

  9. Iron deficiency anemia in children.

    Subramaniam, Girish; Girish, Meenakshi

    2015-06-01

    Iron deficiency is not just anemia; it can be responsible for a long list of other manifestations. This topic is of great importance, especially in infancy and early childhood, for a variety of reasons. Firstly, iron need is maximum in this period. Secondly, diet in infancy is usually deficient in iron. Thirdly and most importantly, iron deficiency at this age can result in neurodevelopmental and cognitive deficits, which may not be reversible. Hypochromia and microcytosis in a complete blood count (CBC) makes iron deficiency anemia (IDA) most likely diagnosis. Absence of response to iron should make us look for other differential diagnosis like β thalassemia trait and anemia of chronic disease. Celiac disease is the most important cause of true IDA not responding to oral iron therapy. While oral ferrous sulphate is the cheapest and most effective therapy for IDA, simple nonpharmacological and pharmacological measures can go a long way in prevention of iron deficiency. PMID:25636824

  10. In situ synchrotron X-ray diffraction study on the improved dehydrogenation performance of NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture

    Yang, Cheng-Hsien; Chen, Tzu-Teng [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tsai, Wen-Ta, E-mail: wttsai@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan (China); Liu, Bernard Haochih [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-11-15

    Highlights: •The dehydrogenation reactions of NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture were explored by in situ XRD. •NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture exhibited multiple-step dehydrogenation processes. •The mutual catalytic roles of NaAlH{sub 4} and Mg(AlH{sub 4}){sub 2} in the mixture were investigated. •NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture release 5.35 wt% H{sub 2} at an initial temperature of 120 °C. -- Abstract: The dehydrogenation performance and mechanism of the synthesized NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} powders were investigated by performing thermogravimetric analysis and in situ synchrotron X-ray diffraction analysis. NaAlH{sub 4} not only facilitates the first step dehydrogenation of Mg(AlH{sub 4}){sub 2} in lowering its initial dehydrogenation temperature but also increases the total amount of H{sub 2} released. Besides, MgH{sub 2} and/or Al phases, the products of the first step dehydrogenation reaction, play a catalytic role in lowering the initial dehydrogenation temperature of NaAlH{sub 4}. The synthesized NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture has an initial dehydrogenation temperature as low as 120 °C, and is able to release 5.35 wt% H{sub 2} below 350 °C. The self-catalytic dehydrogenation behavior of the NaAlH{sub 4}–Mg(AlH{sub 4}){sub 2} mixture was elaborated in this work with the aid of in situ synchrotron XRD.

  11. Interactions between copper deficiency, selenium deficiency and adriamycin toxicity

    Fischer, J.; Tackett, R.; Johnson, M.A. (Univ. of Georgia, Athens (United States))

    1991-03-15

    The objective of this study was to test the hypothesis that there are interactions between copper (Cu) and selenium (Se) status, and adriamycin (ADR) toxicity. Male Sprague Dawley rats were fed Cu,Se adequate; Cu deficient, Se adequate ({minus}Cu); Cu adequate, Se deficient; or Cu,Se deficient diets for 38-41 days. ADR or saline (SAL) were administered weekly for the last 4 weeks of the study. Cu deficiency was confirmed by a 3-fold decrease in liver Cu,Zn-superoxide dismutase and liver Cu, and a 5-fold decrease in RBC Cu,Zn-SOD. Se deficiency was confirmed by a 10-fold decrease in liver glutathione peroxidase (GSH-Px). ADR, Cu deficiency and Se deficiency all caused EKG abnormalities. However, Cu and Se deficiencies did not enhance ADR's influence on EKGs. ADR increased lipid peroxidation in liver by 15% and in heart by 18% (NS). Cu deficiency decreased ADR-induced lipid peroxidation in heart tissue by 25%. ADR influenced Se status by significantly increasing heart GSH-Px, and Cu status by increasing liver Cu, plasma ceruloplasmin and liver Cu, Zn-SOD. These elevations in Cu,Zn-SOD and GSH-Px may be a consequence of the increased lipid peroxidation initiated by ADR. In {minus}Cu rats, ADR caused severe hemolytic anemia characterized by a 19% decrease in hematocrit and a 17-fold increase in splenic Fe. These data suggest that there are numerous interactions between ADR toxicity and Cu and Se status.

  12. Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni{sub 2}P supported on active carbon

    Xu, Yanli [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Sang, Huanxin [Tianjin Academy of Environmental Sciences, Tianjin 300191 (China); Wang, Kang [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang, Xitao, E-mail: wangxt@tju.edu.cn [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2014-10-15

    Graphical abstract: - Highlights: • Ni{sub 2}P catalyst is tested in dehydrogenation of isobutane for the first time. • The effects of Cs promoter on catalytic performance of Ni2P/AC were investigated. • Cs-Ni2P/AC exhibits high activity and selectivity for isobutane dehydrogenation. - Abstract: In this article, an environmentally friendly non-noble-metal class of Cs-Ni{sub 2}P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H{sub 2}-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni{sub 2}P particles, which decreases the strength of Ni-C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni{sub 2}P/AC catalysts display much higher catalytic performance as compared to Ni{sub 2}P/AC catalyst. Cs-Ni{sub 2}P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni{sub 2}P particles, transfer electron from Cs to Ni, and decrease acid site number and strength.

  13. How Is Alpha-1 Antitrypsin Deficiency Diagnosed?

    ... Alpha-1 Antitrypsin Deficiency Diagnosed? Alpha-1 antitrypsin (AAT) deficiency usually is diagnosed after you develop a ... related to the condition. Your doctor may suspect AAT deficiency if you have signs or symptoms of ...

  14. How Is Alpha-1 Antitrypsin Deficiency Treated?

    ... Alpha-1 Antitrypsin Deficiency Treated? Alpha-1 antitrypsin (AAT) deficiency has no cure, but its related lung ... pulmonary disease). If you have symptoms related to AAT deficiency, your doctor may recommend: Medicines called inhaled ...

  15. Glucose-6-Phosphate Dehydrogenase Deficiency Overview

    ... Drugs GARD Information Navigator FAQs About Rare Diseases Glucose-6-phosphate dehydrogenase deficiency Title Other Names: G6PD ... G6PD deficiency Categories: Newborn Screening Summary Summary Listen Glucose 6 phosphate dehydrogenase (G6PD) deficiency is a hereditary ...

  16. Genetics Home Reference: factor V deficiency

    ... Genetics Home Health Conditions factor V deficiency factor V deficiency Enable Javascript to view the expand/collapse ... Print All Open All Close All Description Factor V deficiency is a rare bleeding disorder. The signs ...

  17. Monocular Elevation Deficiency - Double Elevator Palsy

    ... Español Condiciones Chinese Conditions Monocular Elevation Deficiency/ Double Elevator Palsy En Español Read in Chinese What is monocular elevation deficiency (Double Elevator Palsy)? Monocular Elevation Deficiency, also known by the ...

  18. Genetics Home Reference: leptin receptor deficiency

    ... Understand Genetics Home Health Conditions leptin receptor deficiency leptin receptor deficiency Enable Javascript to view the expand/ ... boxes. Print All Open All Close All Description Leptin receptor deficiency is a condition that causes severe ...

  19. Genetics Home Reference: congenital leptin deficiency

    ... Genetics Home Health Conditions congenital leptin deficiency congenital leptin deficiency Enable Javascript to view the expand/collapse ... Print All Open All Close All Description Congenital leptin deficiency is a condition that causes severe obesity ...

  20. Genetics Home Reference: carnitine palmitoyltransferase I deficiency

    ... Understand Genetics Home Health Conditions CPT I deficiency carnitine palmitoyltransferase I deficiency Enable Javascript to view the ... boxes. Print All Open All Close All Description Carnitine palmitoyltransferase I (CPT I) deficiency is a condition ...

  1. Genetics Home Reference: factor XIII deficiency

    ... InfoSearch: Factor XIII deficiency Factor XIII Registry Database: Introduction to Factor XIII Deficiency MalaCards: factor xiii deficiency ... Library of Medicine Lister Hill National Center for Biomedical Communications 8600 Rockville Pike, Bethesda, MD 20894, USA ...

  2. Genetics Home Reference: combined pituitary hormone deficiency

    ... Genetics Home Health Conditions combined pituitary hormone deficiency combined pituitary hormone deficiency Enable Javascript to view the ... boxes. Print All Open All Close All Description Combined pituitary hormone deficiency is a condition that causes ...

  3. Mortality and GH deficiency

    Stochholm, Kirstine; Gravholt, Claus Højbjerg; Laursen, Torben;

    2007-01-01

    OBJECTIVE: To estimate the mortality in Denmark in patients suffering from GH deficiency (GHD). DESIGN: Mortality was analyzed in 1794 GHD patients and 8014 controls matched on age and gender. All records in GHD patients were studied and additional morbidity noted. Patients were divided into...... childhood onset (CO) and adult onset (AO), discriminated by an age cutoff below or above 18 years at onset of GHD. METHOD: Data on death were identified in national registries. Sex- and cause-specific mortalities were identified in CO and AO GHD when compared with controls. RESULTS: Mortality was increased...... in CO and AO GHD in both genders, when compared with controls. The hazard ratio (HR) for CO males was 8.3 (95% confidence interval (CI) 4.5-15.1) and for females 9.4 (CI 4.6-19.4). For AO males, HR was 1.9 (CI 1.7-2.2) and for females 3.4 (CI 2.9-4.0). We found a significantly higher HR in AO females...

  4. Iodine deficiency disorders.

    Elliott, T C

    1987-01-01

    Iodine deficiency disorder (IDD) affects 800 million people in the world, yet iodine supplementation is one of the most cost-effective nutritional interventions known. Iodine is incorporated into thyroid hormones, necessary for regulating metabolic rate, growth, and development of the brain and nervous system. IDD may appear as goiter in adults, usually not a serious problem, or in cretinism in children, which is marked by severe mental and physical retardation, with irreversible hearing and speech defects and either deaf-mutism, squint and paralysis, or stunting and edema. Children supplemented by age 1 or 2 can sometimes be helped. Foods contain variable amounts of iodine dependent on the soil where they are grown, hence mountainous and some inland regions have high goiter and IDD incidence. There are also goitrogenic foods, typically those of the cabbage family. Diagnosis is clinical or by blood tests for thyroid hormone levels and ratios. Finger-stick methods are available. Prevention of IDD is simple with either iodized salt or flour, iodinated central water supplies, injectable or oral iodine-containing oil. All cost about $.04 per person per year, except injections, which cost about $1 per person, but have the advantage that they could be combined with immunizations. Local problems with supplements are loss of iodine in salt with storage in tropics, and local production of cheaper uniodinated salt. Emphasis should be given to pregnant women and young children. There is no harm in giving pregnant women iodine injections in 2nd or 3rd trimester. PMID:12343033

  5. The significance of secondary interactions during alkaline earth-promoted dehydrogenation of dialkylamine-boranes.

    Bellham, Peter; Anker, Mathew D; Hill, Michael S; Kociok-Köhn, Gabriele; Mahon, Mary F

    2016-09-21

    Reactions of anilidoimine magnesium n-butyl and calcium bis(trimethylsilyl)amide derivatives with Me2NH·BH3 at 25 °C resulted in the isolation of complexes containing [NMe2BH2NMe2BH3](-) and [NMe2BH3](-) anions respectively. Although onward reaction of the calcium species at 30 °C with a further equivalent of Me2NH·BH3 provided ca. 90% conversion of the coordinated dimethylamidoborane anion to [NMe2BH2NMe2BH3](-), this process also resulted in significant (ca. 25%) levels of competitive protonation of the anilidoimine spectator ligand. A similar reaction performed between a previously reported β-diketiminato calcium dimethylamidoborane and Me2NH·BH3, however, provided clean conversion to a structurally characterised calcium [NMe2BH2NMe2BH3](-) complex. Reaction of a more sterically congested β-diketiminato magnesium n-butyl reagent with Me2NH·BH3 has allowed the isolation of a magnesium derivative of the [NMe2BH3](-) anion. The thermal stability of these compounds as well as previously reported magnesium and calcium amidoborane species indicate, in partial agreement with a recent DFT study, that all of these compounds are resistant to the β- and δ-hydride elimination reactions that have previously been implicated as the key B-N bond-forming and dehydrogenative steps in the group 2-catalysed dehydrocoupling of Me2NH·BH3. In contrast to these observations, addition of stoichiometric quantities of Me2NH·BH3 to the various isolated group 2 amidoborane species was found to result in facile elimination of the cyclic borazane [Me2N-BH2]2 which occurs with regeneration of the metallated amidoborane. On this basis, we suggest that the dehydrocoupling of Me2NH·BH3 at group 2 centres takes place as a sequence of concerted proton-assisted steps during which B-H and N-H bond breaking plays an equally prominent role, with the efficacy of boron hydride protonolysis dictated by the relative polarising influence of the B-H to Mg/Ca interactions. Furthermore, we propose

  6. Clinical manifestations of zinc deficiency.

    Prasad, A S

    1985-01-01

    The essentiality of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, chronic renal diseases, following uses of certain drugs such as penicillamine for Wilson's disease and diuretics in some cases, and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. In pregnancy and during periods of growth the requirement of zinc is increased. The clinical manifestations in severe cases of zinc deficiency include bullous-pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections, hypogonadism in males; it is fatal if unrecognized and untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities, and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss, and hyperammonemia. Zinc is a growth factor. Its deficiency adversely affects growth in many animal species and humans. Inasmuch as zinc is needed for protein and DNA synthesis and for cell division, it is believed that the growth effect of zinc is related to its effect on protein synthesis. Whether or not zinc is required for the metabolism of somatomedin needs to be investigated in the future. Testicular functions are affected adversely as a result of zinc deficiency in both humans and experimental animals. This effect of zinc is at the end organ level; the hypothalamic-pituitary axis is intact in zinc-deficient subjects. Inasmuch as zinc is intimately involved in cell division, its deficiency may adversely affect testicular size and thus affect its functions. Zinc is required for the functions of several enzymes and whether or not it has an enzymatic role in steroidogenesis is not known at present

  7. [Immune deficiencies in nutritional anemias].

    Bonnet Gajdos, M; Navarro, J; Belas, F; Traineau, R

    1982-12-16

    A transient cellular immunologic defect caused by folic acid deficiency was seen in a goat-milk-fed infant with severe enterocolitis. Data on the immunologic consequences of folic acid, protein and iron deficiencies were reviewed in the medical literature. Investigations are difficult because of the patients' poor general condition. Results are difficult to interpret as many etiologic factors are often combined and mechanisms of immunologic responses are complex. Attention is drawn to the danger of iron therapy in patients with transferrin deficiency. PMID:6297076

  8. Iron deficiency - a global problem

    Iron deficiency is an important nutritional global problem. This paper contains summery of information gathered from a dietary survey as iron deficiency anaemia is major public health problem in many developing countries including Pakistan. Comparison of anaemia in different age group and sex versus various regions in the world are given. In Pakistan also anaemia is widespread. According to the report of Micro-Nutrient survey of Pakistan 40% of the population are found to have low level of haemoglobin, more than half of pregnant women suffered from marginal or deficient haemoglobin. (A.B.)

  9. Genetics Home Reference: adenosine monophosphate deaminase deficiency

    ... links) CLIMB: Children Living with Inherited Metabolic Diseases Muscular Dystrophy Association: Myoadenylate Deaminase Deficiency Genetic Testing Registry (1 link) Muscle AMP deaminase deficiency ...

  10. Conversion of alkanes to linear alkylsilanes using an iridium-iron-catalysed tandem dehydrogenation-isomerization-hydrosilylation

    Jia, Xiangqing; Huang, Zheng

    2016-02-01

    The conversion of inexpensive, saturated hydrocarbon feedstocks into value-added speciality chemicals using regiospecific, catalytic functionalization of alkanes is a major goal of organometallic chemistry. Linear alkylsilanes represent one such speciality chemical—they have a wide range of applications, including release coatings, silicone rubbers and moulding products. Direct, selective, functionalization of alkanes at primary C-H bonds is difficult and, to date, methods for catalytically converting alkanes into linear alkylsilanes are unknown. Here, we report a well-defined, dual-catalyst system for one-pot, two-step alkane silylations. The system comprises a pincer-ligated Ir catalyst for alkane dehydrogenation and an Fe catalyst that effects a subsequent tandem olefin isomerization-hydrosilylation. This method exhibits exclusive regioselectivity for the production of terminally functionalized alkylsilanes. This dual-catalyst strategy has also been applied to regioselective alkane borylations to form linear alkylboronate esters.

  11. Mathematical Modeling and Simulation of the Dehydrogenation of Ethyl Benzene to Form Styrene Using Steady-State Fixed Bed Reactor

    Zaidon M. Shakoor

    2013-05-01

    Full Text Available In this research, two models are developed to simulate the steady state fixed bed reactor used for styrene production by ethylbenzene dehydrogenation. The first is one-dimensional model, considered axial gradient only while the second is two-dimensional model considered axial and radial gradients for same variables.The developed mathematical models consisted of nonlinear simultaneous equations in multiple dependent variables. A complete description of the reactor bed involves partial, ordinary differential and algebraic equations (PDEs, ODEs and AEs describing the temperatures, concentrations and pressure drop across the reactor was given. The model equations are solved by finite differences method. The reactor models were coded with Mat lab 6.5 program and various numerical techniques were used to obtain the desired solution.The simulation data for both models were validated with industrial reactor results with a very good concordance.

  12. Catalytic synthesis of 2-methylpyrazine over Cr-promoted copper based catalyst via a cyclo-dehydrogenation reaction route

    Fangli Jing; Yuanyuan Zhang; Shizhong Luo; Wei Chu; Hui Zhang; Xinyu Shi

    2010-07-01

    The cyclo-dehydrogenation of ethylene diamine and propylene glycol to 2-methylpyrazine was performed under the atmospheric conditions at 380°C. The Cr-promoted Cu-Zn/Al2O3 catalysts were prepared by impregnation method and characterized by ICP-AES, N2 adsorption/desorption, XRD, XPS, N2O chemisorption, TPR and NH3-TPD techniques. The amorphous chromium species existing in Cu-Zn-Cr/Al2O3 catalyst enhanced the dispersion of active component Cu, promoted the reduction of catalyst. Furthermore, the catalytic performance was significantly improved. The acidity of the catalyst played an important role in increasing the 2-MP selectivity. To optimize the reaction parameters, influences of different chromium content, reaction temperature, liquid hourly space velocity (LHSV), reactants molar ratio and time on stream on the product pattern were studied. The results demonstrated that addition of chromium promoter revealed satisfying catalytic activity, stability and selectivity of 2-methylpyrazine.

  13. Intrinsic kinetics of oxidative dehydrogenation of propane in the presence of CO2 over Cr/MSU-1 catalyst

    Haitao Liu; Zhao Zhang; Huiquan Li; Qingze Huang

    2011-01-01

    The intrinsic kinetics of oxidative dehydrogenation of propane with CO2 has been investigated over Cr/MSU-1 catalyst in a fixed bed reactor.Without limitations of both internal and external diffusion, intrinsic kinetic data were obtained under the following conditions: 490-530 C,space velocity of 3600-6000 mL·h-l·g-1 and 3/1 molar ratio for CO2/C3H8 under normal pressure. Based on Langmuir-Hinshelwood mechanism, the kinetic models were established, and they were validated by statistical analysis. The parameters were estimated using Simplex Method combined with Universal Global Optimization Algorithm. The model, taking the surface reaction process as the rate-determining step,is the best one in agreement with the experimental data.

  14. A comparative study of the circulating and fixed bed reactors running. Application to the isobutyric acid oxy-dehydrogenation

    Bechara, R.; Lakraa, M.; Vanhove, D.; Pietrzyk, S. [Ecole Nationale Superieure de Chimie de Lille, 59 - Villeneuve d`Ascq (France); Hecquet, G. [Societe Nationale Elf-Aquitaine (France)

    1995-12-31

    This work deals with the study of the catalytic oxy-dehydrogenation process of the isobutyric acid in methacrylic acid on a Fe-Cs-P-O catalyst. The reaction has been carried out on two facilities: a circulating bed pilot reactor and a bench-scale packed bed reactor. Although there are considerable differences between the two reactors, a comparison has been established. When the reaction is carried out in the circulating bed reactor, an important ratio of carbonaceous species remain adsorbed at the catalyst surface. A more extensive analysis of the catalyst surface suggest that the main part of this adsorbed phase is probably methacrylic acid. (O.M.). 8 refs., 1 fig., 1 tab.

  15. Cluster-derived Ir-Sn/SiO2 catalysts for the catalytic dehydrogenation of propane: A spectroscopic study

    Gallo, Alessandro

    2013-01-01

    Ir-Sn bimetallic silica-based materials have been prepared via deposition of the molecular organometallic clusters (NEt4)2[Ir 4(CO)10(SnCl3)2] and NEt 4[Ir6(CO)15(SnCl3)] or via deposition of Sn organometallic precursor Sn(n-C4H9) 4 onto pre-formed Ir metal particles. These solids possess promising properties, in terms of selectivity, as catalysts for propane dehydrogenation to propene. Detailed CO-adsorption DRIFTS, XANES and EXAFS characterization studies have been performed on these systems in order to compare the structural and electronic evolution of systems in relation to the nature of the Ir-Sn bonds present in the precursor compounds and to propose a structural model of the Ir-Sn species present at the silica surface of the final catalyst. © 2013 The Royal Society of Chemistry.

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

    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.

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

    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.

  18. Amlodipine metabolism in human liver microsomes and roles of CYP3A4/5 in the dihydropyridine dehydrogenation.

    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

  19. Characterization of Industrial Pt-Sn/Al2O3 Catalyst and Transient Product Formations during Propane Dehydrogenation

    Kah Sing Ho

    2013-06-01

    Full Text Available The major problem plaguing propane dehydrogenation process is the coke formation on the Pt-Sn/Al2O3 catalyst which leads to catalyst deactivation. Due to information paucity, the physicochemical characteristics of the commercially obtained regenerated Pt-Sn/Al2O3 catalyst (operated in moving bed reactor and coke formation at different temperatures of reaction were discussed. The physicochemical characterization of regenerated catalyst gave a BET surface area of 104.0 m2/g with graphitic carbon content of 8.0% indicative of incomplete carbon gasification during the industrial propylene production. Effect of temperatures on coke formation was identified by studying the product yield via temperature-programmed reaction carried out at 500oC, 600oC and 700oC. It was found that ethylene was precursor to carbon laydown while propylene tends to crack into methane. Post reaction, the spent catalyst possessed relatively lower surface area and pore radius whilst exhibited higher carbon content (31.80% at 700oC compared to the regenerated catalyst. Significantly, current studies also found that higher reaction temperatures favoured the coke formation. Consequently, the propylene yield has decreased with reaction temperature. © 2013 BCREC UNDIP. All rights reservedReceived: 10th March 2013; Revised: 28th April 2013; Accepted: 6th May 2013[How to Cite: Kah, S.H., Joanna Jo, E.C., Sim, Y.C., Chin, K.C. (2013. Characterization of Industrial Pt-Sn/Al2O3 Catalyst and Transient Product Formations during Propane Dehydrogenation. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1: 77-82. (doi:10.9767/bcrec.8.1.4569.77-82][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4569.77-82] | View in  |

  20. Sn surface-enriched Pt-Sn bimetallic nanoparticles as a selective and stable catalyst for propane dehydrogenation

    Zhu, Haibo

    2014-12-01

    A new one pot, surfactant-free, synthetic route based on the surface organometallic chemistry (SOMC) concept has been developed for the synthesis of Sn surface-enriched Pt-Sn nanoparticles. Bu3SnH selectively reacts with [Pt]-H formed in situ at the surface of Pt nanoparticles, Pt NPs, obtained by reduction of K2PtCl4 by LiB(C2H5)3H. Chemical analysis, 1H MAS and 13C CP/MAS solid-state NMR as well as two-dimensional double-quantum (DQ) and triple-quantum (TQ) experiments show that organo-tin moieties Sn(n-C4H9) are chemically linked to the surface of Pt NPs to produce, in fine, after removal of most of the n-butyl fragment, bimetallic Pt-Sn nanoparticles. The Sn(n-CH2CH2CH2CH3) groups remaining at the surface are believed to stabilize the as-synthesized Pt-Sn NPs, enabling the bimetallic NPs to be well dispersed in THF. Additionally, the Pt-Sn nanoparticles can be supported on MgAl2O4 during the synthesis of the nanoparticles. Some of the Pt-Sn/MgAl2O4 catalyst thus prepared exhibits high activity in PROX of CO and an extremely high selectivity and stability in propane dehydrogenation to propylene. The enhanced activity in propane dehydrogenation is associated with the high concentration of inactive Sn at the surface of Pt nanoparticles which ”isolates” the active Pt atoms. This conclusion is confirmed by XRD, NMR, TEM, and XPS analysis.

  1. Adsorption and dehydrogenation of 2-propanol on the surface of γ-Al2O3-supported gold

    Martinez-Ramirez, Z.; Gonzalez-Calderon, J. A.; Almendarez-Camarillo, A.; Fierro-Gonzalez, J. C.

    2012-08-01

    The adsorption and reactions of 2-propanol on γ-Al2O3 and γ-Al2O3-supported gold samples were investigated by infrared (IR) spectroscopy, modulated differential scanning calorimetry (MDSC) and mass spectrometry. Adsorption of the alcohol on the samples at room temperature led to formation of molecularly adsorbed 2-propanol and 2-propoxide species bonded to Al3+ sites. Treatment of γ-Al2O3 after alcohol adsorption in flowing He from 25 to 300 °C led to 2-propanol desorption, without evidence of surface reactions. In contrast, when supported gold samples were exposed to the same thermal treatment, formation of acetone and H2 was observed by mass spectra of the effluent gases from the flow reactor. Concomitantly, IR spectra of the samples showed the appearance of a band at 1698 cm- 1, assigned to νCO vibrations of adsorbed acetone. The formation of acetone occurred by the dehydrogenation of 2-propoxide species bonded to Al3+ sites, as evidenced by (a) the decrease in the intensities of their IR bands and (b) the presence of a MDSC peak at approximately the same temperature as that at which acetone was formed and the 2-propoxide species were consumed. It is proposed that gold particles on the γ-Al2O3 surface facilitate breaking of the β-Csbnd H bond of neighboring surface 2-propoxide species to give acetone. Our results emphasize the bifunctional character of supported gold catalysts for the dehydrogenation of alcohols.

  2. Evolutionary Processes and Mental Deficiency

    Spitz, Herman H.

    1973-01-01

    The author hypothesizes that central nervous system damage of deficiency associated with mental retardation affects primarily those cortical processes which developed at a late stage in man's evolutionary history. (Author)

  3. [Niacin deficiency and cutaneous immunity].

    Ikenouchi-Sugita, Atsuko; Sugita, Kazunari

    2015-01-01

    Niacin, also known as vitamin B3, is required for the synthesis of coenzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Niacin binds with G protein-coupled receptor (GPR) 109A on cutaneous Langerhans cells and causes vasodilation with flushing in head and neck area. Niacin deficiency due to excessive alcohol consumption, certain drugs or inadequate uptake in diet causes pellagra, a photosensitivity dermatitis. Recently several studies have revealed the mechanism of photosensitivity in niacin deficiency, which may pave a way for new therapeutic approaches. The expression level of prostaglandin E synthase (PTGES) is up-regulated in the skin of both pellagra patients and niacin deficient pellagra mouse models. In addition, pellagra is mediated through prostaglandin E₂-EP4 (PGE₂-EP4) signaling via reactive oxygen species (ROS) production in keratinocytes. In this article, we have reviewed the role of niacin in immunity and the mechanism of niacin deficiency-induced photosensitivity. PMID:25765687

  4. Cutaneous findings of nutritional deficiencies in children.

    Goskowicz, M; Eichenfield, L F

    1993-08-01

    Nutritional deficiencies may be associated with a variety of cutaneous findings in children. This review emphasizes new developments relating to cutaneous findings of nutritional deficiencies. Zinc deficiency, acrodermatitis enteropathica, and acrodermatitis enteropathica-like eruptions are seen with a variety of conditions including cystic fibrosis, anorexia nervosa, and breastfeeding. Similar cutaneous findings not related to zinc deficiency may also occur with such metabolic disorders as methylmalonic aciduria, multiple carboxylase deficiency, essential fatty acid deficiency and other amino acid deficiencies. Vitamin K deficiency is associated with hemorrhagic disease of the newborn and coagulopathy. Vitamin A deficiency presents with a variety of systemic findings and distinctive dermatologic findings. Acute vitamin A deficiency may be seen in children infected with measles and is associated with more severe disease. The systemic and cutaneous findings of vitamin C deficiency, scurvy, are discussed. PMID:8374671

  5. Health Consequences of Iodine Deficiency

    Kapil, Umesh

    2007-01-01

    Iodine Deficiency Disorders (IDD) are one of the biggest worldwide public health problem of today. Their effect is hidden and profoundly affects the quality of human life. Iodine deficiency occurs when the soil is poor in iodine, causing a low concentration in food products and insufficient iodine intake in the population. When iodine requirements are not met, the thyroid may no longer be able to synthesize sufficient amounts of thyroid hormone. The resulting low-level of thyroid hormones in ...

  6. Organophosphates and monocyte esterase deficiency.

    1995-01-01

    AIMS--To examine the possibility that monocyte esterase deficiency (MED) could be caused by exposure to organophosphates. METHODS--Pseudocholinesterase, paraoxonase and arylesterase activities were measured in the serum and acetylcholinesterase activity was measured in the red cells of a group of monocyte esterase deficient subjects and compared with the enzyme activities of a control group of monocyte esterase positive subjects. RESULTS--No significant difference was found between the enzyme...

  7. Zinc and its deficiency diseases.

    Evans, G W

    1986-01-01

    The pervasive role of zinc in the metabolic function of the body results from its function as a cofactor of a multitude of enzymes. Zinc is found in every tissue in the body, and because zinc metalloenzymes are found in every known class of enzymes, the metal has a function in every conceivable type of biochemical pathway. Symptoms resulting from zinc deficiency are as diverse as the enzymes with which the metal is associated. If chronic, severe, and untreated, zinc deficiency can be fatal. Less drastic symptoms include infections, hypogonadism, weight loss, emotional disturbance, dermatitis, alopecia, impaired taste acuity, night blindness, poor appetite, delayed wound healing, and elevated blood ammonia levels. Many symptoms of zinc deficiency result from poor diet consumption, but often the most severe symptoms result from other factors including excessive alcohol use, liver diseases, malabsorption syndromes, renal disease, enteral or parenteral alimentation, administration of sulfhydryl-containing drugs, and sickle cell disease. The most severe symptoms of zinc deficiency occur in young children affected with the autosomal-recessive trait, acrodermatitis enteropathica. This disease results in decreased synthesis of picolinic acid which causes an impaired ability to utilize zinc from common food. Because simple laboratory analyses are often not reliable in determining zinc nutriture of a patient, those symptoms caused by suspected zinc deficiency are best verified by the oral administration of zinc dipicolinate. This zinc compound is efficacious and safe and would provide an accurate means of identifying symptoms that do result from zinc deficiency. PMID:3514057

  8. Influence of the pressure on the product distribution in the oxidative dehydrogenation of propane over a Ga2O3/MoO3 catalystInfluence of the pressure on the product distribution in the oxidative dehydrogenation of propane over a Ga2O3/MoO3 catalyst

    Kotanjac, Z. S.; Niederer, J. P. M.; Versteeg, G. F.

    2007-01-01

    The yields and selectivities in both the catalyzed and non-catalyzed oxidative dehydrogenation of propane were found to increase with increasing pressure. The results showed that the maximum yields of valuable ODH products could be obtained by adjusting only reactants' partial pressure, while keepin

  9. Inlfuence of the Alkali Treatment of HZSM-5 Zeolite on Catalytic Performance of PtSn-Based Catalyst for Propane Dehydrogenation

    Huang Li; Zhou Shijian; Zhou Yuming; Zhang Yiwei; Xu Jun; Wang Li

    2013-01-01

    The porous material ATZ with micro-mesopore hierarchical porosity was prepared by alkali treatment of parent HZSM-5 zeolite and applied for propane dehydrogenation. The zeolite samples were characterized by XRD, N2-physisorption, and NH3-TPD analysis. The results showed that the alkali treatment can modify the physicochemical prop-erties of HZSM-5 zeolite. In this case, the porous material ATZ showed larger external surface area with less acid sites as compared to the HZSM-5 zeolite. It was found out that the alkali treatment of HZSM-5 zeolite could promote the catalytic performance of PtSn/ATZ catalyst. The possible reason was ascribed to the low acidity of ATZ. Furthermore, the presence of mesopores could reduce the carbon deposits on the metallic surface, which was also favorable for the dehydrogenation reaction.

  10. Dehydrogenation kinetics, reversibility, and reaction mechanisms of reversible hydrogen storage material based on nanoconfined MgH2-NaAlH4

    Plerdsranoy, Praphatsorn; Meethom, Sukanya; Utke, Rapee

    2015-12-01

    Studies of dehydrogenation kinetics, reversibility, and reaction mechanisms during de/rehydrogenation of nanoconfined MgH2-NaAlH4 into carbon aerogel scaffold (CAS) for reversible hydrogen storage material are for the first time proposed. Two different MgH2:NaAlH4 molar ratios (1:1 and 2:1) of hydride composite are melt infiltrated into CAS under 1:1 (CAS:hydride composite) weight ratio. Successful nanoconfinement is confirmed by N2 adsorption-desorption. Multiple-step dehydrogenation of milled samples is reduced to two-step reaction due to nanoconfinement. Peak temperatures corresponding to main dehydrogenation of nanoconfined samples significantly reduce as compared with those of milled samples, i.e., ∆T=up to 50 and 34 °C for nanoconfined sample with 1:1 and 2:1 (MgH2:NaAlH4) molar ratios, respectively. Hydrogen content released (the 1st cycle) and reproduced (the 2nd, 3rd, and 4th cycles) of nanoconfined samples enhance up to 80% and 68% with respect to theoretical hydrogen storage capacity, respectively, while those of milled samples are 71% and 38%, respectively. Remarkable hydrogen content reproduced after nanoconfinement is due to the fact that metallic Al obtained after dehydrogenation (T=300 °C under vacuum) of nanoconfined samples prefer to react with MgH2 and produces Al12Mg17, favorable for reversibility of MgH2-NaAlH4 system, whereas that of milled samples stays in the form of unreacted Al under the same temperature and pressure condition.

  11. Improved dehydrogenation performance of LiBH4 by 3D hierarchical flower-like MoS2 spheres additives

    Zhao, Yan; Liu, Yongchang; Liu, Huiqiao; Kang, Hongyan; Cao, Kangzhe; Wang, Qinghong; Zhang, Chunling; Wang, Yijing; Yuan, Huatang; Jiao, Lifang

    2015-12-01

    In this work, 3D hierarchical flower-like MoS2 spheres are successfully fabricated via a hydrothermal method followed by a heat treatment. The obtained product is composed of few-layered MoS2 nanosheets with enlarged interlayer distance (ca. 0.66 nm) of the (002) plane. Meanwhile, the hydrogen storage properties of the as-prepared MoS2 ball milled with LiBH4 are systematically investigated. The results of temperature programmed desorption (TPD) and isothermal measurement suggest that the LiBH4-MoS2 (as-prepared) mixture exhibits favorable dehydrogenation properties in both lowering the hydrogen release temperature and improving kinetics of hydrogen release rate. LiBH4-MoS2 (as-prepared) sample (the preparation mass ratio is 1:1) starts to release hydrogen at 171 °C, and roughly 5.6 wt% hydrogen is released within 1 h when isothermally heated to 320 °C, which presents superior dehydrogenation performance compared to that of the bulk LiBH4. The excellent dehydrogenation performance of the LiBH4-MoS2 (as-prepared) mixture may be attributed to the high active site density and enlarged interlayer distance of the MoS2 nanosheets, 3D architectures and hierarchical structures.

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

    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

  13. Ceria-Based Mixed Oxide Supported Nano-Gold as an Efficient and Durable Heterogeneous Catalyst for Oxidative Dehydrogenation of Amines to Imines Using Molecular Oxygen

    Bashir Ahmad Dar

    2012-06-01

    Full Text Available The present work is intended to determine the catalytic activity of Mixed Oxide supported gold for aerobic oxidative dehydrogenation of amines to imines using Ceria as a main constituent of the each support. The model catalysts Au/CeO2:TiO2 Au/CeO2:SiO2, Au/CeO2:ZrO2 and Au/CeO2:Al2Os were prepared by deposition co-precipitation method and deposition of gold was determined by EDEX analysis. The supported nano-gold catalyzes the dehydrogenation of secondary amines to imines without loss of activity. On recycling good amount of product yield is obtained. Oxidation of secondary amines to imines is carried at 100˚C and almost 90 % conversion was obtained with >99% selectivity. © 2012 BCREC UNDIP. All rights reservedReceived: 26th December 2011; Revised: 7th June 2012; Accepted: 13rd June 2012[How to Cite: B.A. Dar, M. Sharma, B. Singh. (2012. Ceria-Based Mixed Oxide Supported Nano-Gold as an Efficient and Durable Heterogeneous Catalyst for Oxidative Dehydrogenation of Amines to Imines Using Molecular Oxygen. Bulletin of Chemical Reaction Engineering & Catalysis, 7(1: 79-84.  doi:10.9767/bcrec.7.1.1257.79-84][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.1257.79-84 ] | View in 

  14. Influence of preparation conditions of hollow titania–nickel composite spheres on their catalytic activity for hydrolytic dehydrogenation of ammonia borane

    Highlights: • We study influence of preparation conditions on activity of hollow titania–nickel composite spheres. • The activity for hydrolytic dehydrogenation of NH3BH3 increases with increase of Ti + Ni content. • The activity depends on the amount of PS residue in the hollow spheres. - Abstract: The present work reports influence of preparation conditions of hollow titania–nickel composite spheres on their morphology and catalytic activity for hydrolytic dehydrogenation of ammonia borane (NH3BH3). The as-prepared hollow titania–nickel composite spheres were characterized by transmission electron microscopy (TEM). Catalytic activities of the hollow spheres for hydrolytic dehydrogenation of aqueous NaBH4/NH3BH3 solution improve with the decrease of Ti + Ni content. From the results of FTIR spectra and elemental analysis, the amount of residual polystyrene (PS) templates is able to be reduced by increasing aging time for the preparation, and the catalytic activity of the hollow spheres increases when the amount of residual PS templates decreases. The carbon content in the hollow spheres prepared with aging time = 24 h is 17.3 wt.%, and the evolution of 62 mL hydrogen is finished in about 22 min in the presence of the hollow spheres from aqueous NaBH4/NH3BH3 solution. The molar ratio of the hydrolytically generated hydrogen to the initial NH3BH3 in the presence of the hollow spheres is 2.7

  15. Fabrication of hollow silica–zirconia composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

    Umegaki, Tetsuo, E-mail: umegaki.tetsuo@nihon-u.ac.jp [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Hosoya, Tatsuya; Toyama, Naoki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Xu, Qiang [National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Kojima, Yoshiyuki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan)

    2014-09-01

    Highlights: • Hollow silica–zirconia composite spheres were fabricated on polystyrene templates by the sol–gel method. • We study the effect of preparation conditions on the activity for hydrolytic dehydrogenation of ammonia borane. • The activity of hollow silica–zirconia composite spheres depends on wall thickness. - Abstract: In this paper, we report fabrication of hollow silica–zirconia composite spheres by polystyrene (PS) template method and control of wall thickness of the hollow spheres in nanoscale. Both the hollow spheres before and after calcination were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and powder X-ray diffraction analysis (XRD). Morphology of the hollow spheres does not significantly change after calcination from the results of SEM and TEM images, while the amount of residual PS templates drastically decreases via the calcination procedure from the results of FTIR and elemental analysis. The sample after calcination mainly includes amorphous silica from the results of XRD, indicating that the hollow silica–zirconia composite spheres consist of amorphous phases and/or fine particles. Wall thicknesses of the samples after calcination are controlled by adjusting the amount of PS template suspension, and hollow silica–zirconia composite spheres with the wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm are obtained using the PS template suspension of 25.0, 33.5, 100.0, and 400.0 g, respectively. The activities of the hollow spheres for hydrolytic dehydrogenation of ammonia borane (NH{sub 3}BH{sub 3}) were compared. The evolutions of 2.0, 3.1, 5.0, and 8.0 mL hydrogen from aqueous NH{sub 3}BH{sub 3} solution were finished in about 4, 5, 3, and 7 min in the presence of the hollow spheres with wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm, respectively. The molar ratios of the hydrolytically generated hydrogen to

  16. Folate Deficiency in Chronic Pancreatitis

    Gopalakrishna Rajesh

    2010-07-01

    Full Text Available Dear Sir, While there has been a spurt of interest in genetic alterations associated with pancreatitis in the past few years, interest in the role of environmental factors has largely focused on alcoholism and smoking with insufficient attention being paid to the contributions of nutritional deficiency, and the role of environmental toxins in the pathogenesis of pancreatitis. Braganza and Dormandy [1] argue convincingly about the role played by cytochrome P450 monooxygenases (especially CYP1A enzyme induction by xenobiotics and the resultant oxidative stress, as also the now increasingly recognized reductive stress posed by the metabolites in initiating pancreatic injury. Their article underlines the important part played by the deficiency of methyl and thiol molecules in different stages of the progression of pancreatic damage. Furthermore, they attempt to establish a link between environmental and genetic factors and bring in a holistic view on the etiopathogenesis of chronic pancreatitis. We have recently demonstrated lower plasma methionine levels in two cohorts of chronic pancreatitis patients; one of tropical chronic pancreatitis and the other, of alcoholic chronic pancreatitis as compared to healthy controls [2] which suggests that deficiency of methyl groups may be a factor in various forms of pancreatitis. Similarly, we have shown lower red cell glutathione levels in chronic pancreatitis patients with tropical chronic pancreatitis and alcoholic chronic pancreatitis, indicating deficiency of thiol molecules. In addition, we have demonstrated significantly higher levels of plasma total homocysteine in chronic pancreatitis patients than in healthy controls. Moreover, our study has shown that there is a deficiency of red cell folate in the majority of chronic pancreatitis patients, more so in tropical chronic pancreatitis; and that folate deficiency appeared to be the key factor in hyperhomocysteinemia in chronic pancreatitis patients

  17. Iron deficiency in the tropics.

    Fleming, A F

    1982-06-01

    Iron in food is classified as belonging to the haem pool, the nonhaem pool, and extraneous sources. Haem iron is derived from vegetable and animal sources with varying bioavailability. Hookworm infestation of the intestinal tract affects 450 million people in the tropics. Schistosoma mansoni caused blood loss in 7 Egyptian patients of 7.5- 25.9 ml/day which is equivalent to a daily loss of iron of .6-7.3 mg daily urinary loss of iron in 9 Egyptian patients. Trichuris trichiura infestation by whipworm is widespread in children with blood loss of 5 ml/day/worm. The etiology of anemia in children besides iron deficiency includes malaria, bacterial or viral infections, folate deficiency and sickle-cell disease. Severe infections cause profound iron-deficiency anemia in children in central American and Malaysia. Plasmodium falciparum malaria-induced anaemia in tropical Africa lowers the mean haemoglobin concentration in the population by 2 g/dI, causing profound anaemia in some. The increased risk of premature delivery, low birthweight, fetal abnormalities, and fetal death is directly related to the degree of maternal anemia. Perinatal mortality was reduced from 38 to 4% in treated anemic mothers. Mental performance was significantly lower in anemic school children and improved after they received iron. Supplements of iron, soy-protein, calcium, and vitamins given to villagers with widespread malnutrition, iron deficiency, and hookworm infestation in Colombia reduced enteric infections in children. Severe iron-deficiency anemia was treated in adults in northern Nigeria by daily in Ferastral 10 ml, which is equivalent to 500 mg of iron per day. Choloroquine, folic acid, rephenium hydroxynaphthoate, and tetrachlorethylene treat adults with severe iron deficiency from hookworm infestation in rural tropical Africa. Blood transfusion is indicated if the patient is dying of anaemia or is pregnant with a haemoglobin concentration 6 gm/dl. In South East Asia, mg per day

  18. Main: 1W07 [RPSD[Archive

    Full Text Available 1; Arabidopsis Thaliana Molecule: Acyl-Coa Oxidase; Chain: A, B; Mutation: Yes; Engineered: Yes Oxidoreducta...AGSRHAFEVSDRIARLVASDPVFEKSNRARLSRKELFKSTLRKCAHAFKRIIELRLNEEEAGRLRHFIDQPAYVDLHWGMFVPAI...YLWCSGLPELFAVYVPACTYEGDNVVLQLQVARFLMKTVAQLGSGKVPVGTTAYMGRAAHLLQCRSGVQKAEDWLNPDVVLEAFEARALRMAVTCAKNLSKFENQEQGFQELLADLVEAAI

  19. Dopamine beta-hydroxylase deficiency

    Senard Jean-Michel

    2006-03-01

    Full Text Available Abstract Dopamine beta-hydroxylase (DβH deficiency is a very rare form of primary autonomic failure characterized by a complete absence of noradrenaline and adrenaline in plasma together with increased dopamine plasma levels. The prevalence of DβH deficiency is unknown. Only a limited number of cases with this disease have been reported. DβH deficiency is mainly characterized by cardiovascular disorders and severe orthostatic hypotension. First symptoms often start during a complicated perinatal period with hypotension, muscle hypotonia, hypothermia and hypoglycemia. Children with DβH deficiency exhibit reduced ability to exercise because of blood pressure inadaptation with exertion and syncope. Symptoms usually worsen progressively during late adolescence and early adulthood with severe orthostatic hypotension, eyelid ptosis, nasal stuffiness and sexual disorders. Limitation in standing tolerance, limited ability to exercise and traumatic morbidity related to falls and syncope may represent later evolution. The syndrome is caused by heterogeneous molecular alterations of the DBH gene and is inherited in an autosomal recessive manner. Restoration of plasma noradrenaline to the normal range can be achieved by therapy with the synthetic precursor of noradrenaline, L-threo-dihydroxyphenylserine (DOPS. Oral administration of 100 to 500 mg DOPS, twice or three times daily, increases blood pressure and reverses the orthostatic intolerance.

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

    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

  1. Ruthenium nanoparticles confined in SBA-15 as highly efficient catalyst for hydrolytic dehydrogenation of ammonia borane and hydrazine borane

    Yao, Qilu; Lu, Zhang-Hui; Yang, Kangkang; Chen, Xiangshu; Zhu, Meihua

    2015-10-01

    Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)-1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol-1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.

  2. Substitution of Tyr254 with Phe at the active site of flavocytochrome b2: consequences on catalysis of lactate dehydrogenation

    Dubois, J.; Chapman, S.K.; Mathews, F.S.; Reid, G.A.; Lederer, F. (INSERM U 25, CNRS UA 122, Hopital Necker, Paris (France))

    1990-07-10

    A role for Tyr254 in L-lactate dehydrogenation catalyzed by flavocytochrome b2 has recently been proposed on the basis of the known active-site structure and of studies that had suggested a mechanism involving the initial formation of a lactate carbanion. This role is now examined after replacement of Tyr254 with phenylalanine. The kcat is decreased about 40-fold, Km for lactate appears unchanged, and the mainly rate-limiting step is still alpha-hydrogen abstraction, as judged from the steady-state deuterium isotope effect. Modeling studies with lactate introduced into the active site indicate two possible substrate conformations with different hydrogen-bonding partners for the substrate hydroxyl. If the hydrogen bond is formed with Tyr254, as was initially postulated, the mechanism must involve removal by His373 of the C2 hydrogen, with carbanion formation. If, in the absence of the Tyr254 phenol group, the hydrogen bond is formed with His373 N3, the substrate is positioned in such a way that the reaction must proceed by hydride transfer. Therefore the mechanism of the Y254F enzyme was investigated so as to distinguish between the two mechanistic possibilities. 2-Hydroxy-3-butynoate behaves with the mutant as a suicide reagent, as with the wild-type enzyme. Similarly, the mutant protein also catalyzes the reduction and the dehydrohalogenation of bromopyruvate under transhydrogenation conditions.

  3. Oxidative Dehydrogenation of n-Butane over LaV Catalysts Supported on TiO2

    Le Minh Cam

    2013-01-01

    Full Text Available The catalytic performance of vanadia catalysts with 15 wt% V supported on TiO2 and (15 wt% V + 4.6 wt% La supported on TiO2 in oxidative dehydrogenation (ODH of n-butane was investigated. The catalysts were characterized by means of TPD-NH3, TPR-H2, UV-Vis, and BET. Testing of samples showed that vanadia catalysts were active for the reaction. It was found that La doping of V/TiO2 catalyst had a negative effect on the dispersion of V species and led to formation of V2O5 clusters. This resulted in a loss of activity. Although slight improvement of selectivity was observed in comparison to undoped V/TiO2 samples due to lower acidity of La-doped –V/TiO2, this could not compensate the loss of activity and finally did not lead to higher butene yields.

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

    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.

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

    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.

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

    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.

  7. Incorporation of catalytic dehydrogenation into Fischer-Tropsch synthesis of liquid fuels from coal to minimize carbon dioxide emissions

    Gerald P. Huffman [University of Kentucky, Lexington, KY (United States). Consortium for Fossil Fuel Science and Department of Chemical & Materials Engineering

    2011-08-15

    Synthesis gas (syngas) produced from coal typically has hydrogen to carbon monoxide ratios in the range of approximately 0.7-1.1, depending on the gasification method. In order to produce liquid fuels from this syngas by Fischer-Tropsch synthesis (FTS), these ratios must be raised to 2.0 or higher. If this is accomplished by the water-gas shift reaction, the traditional method, large emissions of carbon dioxide are produced. In this paper, it is shown that catalytic dehydrogenation (CDH) of the gaseous C1-C4 products of FT synthesis and recycling of the resulting hydrogen to the syngas feed-stream can increase the H{sub 2}/CO ratio to the desired values with little or no production of carbon dioxide. All carbon from the CDH reaction is in the form of a potentially valuable by-product, multi-walled carbon nanotubes (MWCNT). The amounts of hydrogen and MWCNT produced, carbon dioxide emissions avoided, and water saved are calculated for a 50,000 bbl/day FTS-CDH plant and it is demonstrated that the energy balance for the process is favorable. Methods of utilizing the large quantity of MWCNT produced are discussed. 50 refs., 6 figs., 3 tabs.

  8. Kinetic study of propane dehydrogenation and catalyst deactivation over Pt-Sn/Al2O3 catalyst

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

    2013-01-01

    The kinetics of propane dehydrogenation and catalyst deactivation over Pt-Sn/Al2O3 catalyst were studied.Performance test runs were carried out in a fixed-bed integral reactor.Using a power-law rate expression for the surface reaction kinetics and independent law for deactivation kinetics,the experimental data were analyzed both by integral and a novel differential method of analysis and the results were compared.To avoid fluctuation of time-derivatives of conversion required for differential analysis,the conversion-time data were first fitted with appropriate functions.While the time-zero and rate constant of reaction were largely insensitive to the function employed,the rate constant of deactivation was much more sensitive to the function form.The advantage of the proposed differential method,however,is that the integration of the rate expression is not necessary which otherwise could be complicated or impossible.It was also found that the reaction is not limited by external and internal mass transfer limitations,implying that the employed kinetics could be considered as intrinsic ones.

  9. Microstructure and electrochemical hydrogenation/dehydrogenation performance of melt-spun La-doped Mg2Ni alloys

    This work focuses on microstructure and electrochemical hydrogen storage properties of La-doped Mg2Ni alloys. The alloys with nominal compositions of Mg2Ni1−xLax (x = 0, 0.1, 0.3, 0.5) were prepared via metallurgical smelting and melt-spun on a rotating copper wheel. The scanning electron microscope, X-ray diffraction, differential scanning calorimetry and transition electron microscope, galvanostatic charging/discharging and other electrochemical measurements were employed to investigate. The results show that the increasing of La content and melt-spinning speed favors the formation of Mg–Ni–La amorphous/nanocrystalline alloys. It is found that the melt-spun ribbons display increased discharge capacities and superior cycle stabilities compared to the as-cast alloys with and without La. The potentiodynamic polarization results indicate that melt-spun La-doped Mg2Ni ribbons possess more positive corrosion potential Ecorr and exhibit relatively high corrosion resistance against the alkaline solution. The mechanism for electrochemical hydrogenation/dehydrogenation has been proposed based on the effect of microstructures on the mass/charge transfer process for electrode electrochemical reaction. - Highlights: • Nanocrystalline/amorphous Mg–Ni–La alloys are obtained by melt-spinning. • Microstructures of as-cast and rapid quenched Mg2Ni1−xLax alloys are investigated. • Electrochemical hydrogenation properties of experimental alloys are characterized. • Electrochemical hydrogen absorption/desorption mechanism is proposed

  10. Photocatalytic Ethanol Oxidative Dehydrogenation over Pt/TiO2: Effect of the Addition of Blue Phosphors

    J. J. Murcia

    2012-01-01

    Full Text Available Ethanol oxidative dehydrogenation over Pt/TiO2 photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO2 with a loading of 0.5 wt% of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO2 catalyst, keeping at the same time the high selectivity to acetaldehyde.

  11. Studies on ethylbenzene dehydrogenation with CO2 as soft oxidant over Co3O4/COK-12 catalysts

    Ramudu Pochamoni; Anand Narani; Mohan Varkolu; Murali Dhar Gudimella; S Sai Prasad Potharaju; David Raju Burri; Seetha Rama Rao Kamaraju

    2015-04-01

    Oxidative dehydrogenation of ethylbenzene to styrene has been studied over Co3O4 supported on mesoporous silica (COK-12) with CO2 as soft oxidant in a fixed bed reactor at atmospheric pressure in the temperature range of 723 to 923K. While COK-12 has been prepared by self-assembly method using long chain ionic surfactant i.e., P123 as template, cobalt oxide supported on COK-12 catalysts with variable Co content have been synthesised by simple wet impregnation technique. All the catalysts were characterized by N2 adsorption - desorption, XRD, FT-IR, TPR, UV-Vis and XPS techniques. XRD and pore size distribution studies indicate the intactness of mesoporous structure of SiO2 even after incorporation of Co3O4. Presence of Co3O4 crystallites were observed beyond 5 wt% Co loading. High ethylbenzene conversion and stable styrene yields have been observed over 3% Co3O4/COK-12 catalyst due to the presence of large number of active Co3O4 catalytic sites. Enhancement in the activity has been observed with CO2 as soft oxidant than with N2 as diluent. This is because of the fact that the liberated H2 reacts with CO2 in the form of reverse water gas shift reaction.

  12. Diagnosis of vitamin B12 deficiency.

    HU, Rehman

    1984-01-01

    Vitamin B12 (cobalamin) deficiency occurs primarily as a result  of insufficient dietary intake or poor absorp-tion. There is widespread global prevalence of vitamin B12 deficiency, resulting in considerable morbidity.

  13. What Causes Alpha-1 Antitrypsin Deficiency?

    ... this page from the NHLBI on Twitter. What Causes Alpha-1 Antitrypsin Deficiency? Alpha-1 antitrypsin (AAT) ... develop. The most common faulty gene that can cause AAT deficiency is called PiZ. If you inherit ...

  14. Diagnosis of Vitamin B12 Deficiency

    HU, Rehman

    2016-01-01

    Vitamin B12 (cobalamin) deficiency occurs primarily as a result  of insufficient dietary intake or poor absorp-tion. There is widespread global prevalence of vitamin B12 deficiency, resulting in considerable morbidity.

  15. Genetics Home Reference: tyrosine hydroxylase deficiency

    Skip to main content Your Guide to Understanding Genetic Conditions Enable Javascript for addthis links to activate. ... Conditions Genes Chromosomes & mtDNA Resources Help Me Understand Genetics Home Health Conditions TH deficiency tyrosine hydroxylase deficiency ...

  16. Glucose-6-Phosphate Dehydrogenase Deficiency Overview

    ... Information Center (GARD) Print friendly version Glucose-6-phosphate dehydrogenase deficiency Table of Contents Overview Symptoms Cause ... National Institutes of Health. Overview Listen Glucose 6 phosphate dehydrogenase (G6PD) deficiency is a hereditary condition in ...

  17. Cobalamin deficiency, hyperhomocysteinemia, and dementia

    Steven F Werder

    2010-04-01

    Full Text Available Steven F Werder1,21Kansas University School of Medicine – Wichita, Wichita, KS, USA; 2Community Health Center of Southeast Kansas, Pittsburg, KS, USAIntroduction: Although consensus guidelines recommend checking serum B12 in patients with dementia, clinicians are often faced with various questions: (1 Which patients should be tested? (2 What test should be ordered? (3 How are inferences made from such testing? (4 In addition to serum B12, should other tests be ordered? (5 Is B12 deficiency compatible with dementia of the Alzheimer’s type? (6 What is to be expected from treatment? (7 How is B12 deficiency treated?Methods: On January 31st, 2009, a Medline search was performed revealing 1,627 citations related to cobalamin deficiency, hyperhomocysteinemia, and dementia. After limiting the search terms, all abstracts and/or articles and other references were categorized into six major groups (general, biochemistry, manifestations, associations and risks, evaluation, and treatment and then reviewed in answering the above questions.Results: The six major groups above are described in detail. Seventy-five key studies, series, and clinical trials were identified. Evidence-based suggestions for patient management were developed.Discussion: Evidence is convincing that hyperhomocysteinemia, with or without hypovitaminosis B12, is a risk factor for dementia. In the absence of hyperhomocysteinemia, evidence is less convincing that hypovitaminosis B12 is a risk factor for dementia. B12 deficiency manifestations are variable and include abnormal psychiatric, neurological, gastrointestinal, and hematological findings. Radiological images of individuals with hyperhomocysteinemia frequently demonstrate leukoaraiosis. Assessing serum B12 and treatment of B12 deficiency is crucial for those cases in which pernicious anemia is suspected and may be useful for mild cognitive impairment and mild to moderate dementia. The serum B12 level is the standard initial test

  18. CH4 dehydrogenation on Cu(1 1 1), Cu@Cu(1 1 1), Rh@Cu(1 1 1) and RhCu(1 1 1) surfaces: A comparison studies of catalytic activity

    Highlights: • Adsorbed Rh atom on Cu catalyst exhibits better catalytic activity for CH4 dehydrogenation. • The adsorbed Rh atom is the reaction active center for CH4 dehydrogenation. • The morphology of Cu substrate has negligible effect on CH4 dehydrogenation. - Abstract: In the CVD growth of graphene, the reaction barriers of the dehydrogenation for hydrocarbon molecules directly decide the graphene CVD growth temperature. In this study, density functional theory method has been employed to comparatively probe into CH4 dehydrogenation on four types of Cu(1 1 1) surface, including the flat Cu(1 1 1) surface (labeled as Cu(1 1 1)) and the Cu(1 1 1) surface with one surface Cu atom substituted by one Rh atom (labeled as RhCu(1 1 1)), as well as the Cu(1 1 1) surface with one Cu or Rh adatom (labeled as Cu@Cu(1 1 1) and Rh@Cu(1 1 1), respectively). Our results show that the highest barrier of the whole CH4 dehydrogenation process is remarkably reduced from 448.7 and 418.4 kJ mol−1 on the flat Cu(1 1 1) and Cu@Cu(1 1 1) surfaces to 258.9 kJ mol−1 on RhCu(1 1 1) surface, and to 180.0 kJ mol−1 on Rh@Cu(1 1 1) surface, indicating that the adsorbed or substituted Rh atom on Cu catalyst can exhibit better catalytic activity for CH4 complete dehydrogenation; meanwhile, since the differences for the highest barrier between Cu@Cu(1 1 1) and Cu(1 1 1) surfaces are smaller, the catalytic behaviors of Cu@Cu(1 1 1) surface are very close to the flat Cu(1 1 1) surface, suggesting that the morphology of Cu substrate does not obviously affect the dehydrogenation of CH4, which accords with the reported experimental observations. As a result, the adsorbed or substituted Rh atom on Cu catalyst exhibit a better catalytic activity for CH4 dehydrogenation compared to the pure Cu catalyst, especially on Rh-adsorbed Cu catalyst, we can conclude that the potential of synthesizing high-quality graphene with the help of Rh on Cu foils may be carried out at relatively low

  19. CH{sub 4} dehydrogenation on Cu(1 1 1), Cu@Cu(1 1 1), Rh@Cu(1 1 1) and RhCu(1 1 1) surfaces: A comparison studies of catalytic activity

    Zhang, Riguang; Duan, Tian [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Ling, Lixia [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Wang, Baojun, E-mail: wangbaojun@tyut.edu.cn [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

    2015-06-30

    Highlights: • Adsorbed Rh atom on Cu catalyst exhibits better catalytic activity for CH{sub 4} dehydrogenation. • The adsorbed Rh atom is the reaction active center for CH{sub 4} dehydrogenation. • The morphology of Cu substrate has negligible effect on CH{sub 4} dehydrogenation. - Abstract: In the CVD growth of graphene, the reaction barriers of the dehydrogenation for hydrocarbon molecules directly decide the graphene CVD growth temperature. In this study, density functional theory method has been employed to comparatively probe into CH{sub 4} dehydrogenation on four types of Cu(1 1 1) surface, including the flat Cu(1 1 1) surface (labeled as Cu(1 1 1)) and the Cu(1 1 1) surface with one surface Cu atom substituted by one Rh atom (labeled as RhCu(1 1 1)), as well as the Cu(1 1 1) surface with one Cu or Rh adatom (labeled as Cu@Cu(1 1 1) and Rh@Cu(1 1 1), respectively). Our results show that the highest barrier of the whole CH{sub 4} dehydrogenation process is remarkably reduced from 448.7 and 418.4 kJ mol{sup −1} on the flat Cu(1 1 1) and Cu@Cu(1 1 1) surfaces to 258.9 kJ mol{sup −1} on RhCu(1 1 1) surface, and to 180.0 kJ mol{sup −1} on Rh@Cu(1 1 1) surface, indicating that the adsorbed or substituted Rh atom on Cu catalyst can exhibit better catalytic activity for CH{sub 4} complete dehydrogenation; meanwhile, since the differences for the highest barrier between Cu@Cu(1 1 1) and Cu(1 1 1) surfaces are smaller, the catalytic behaviors of Cu@Cu(1 1 1) surface are very close to the flat Cu(1 1 1) surface, suggesting that the morphology of Cu substrate does not obviously affect the dehydrogenation of CH{sub 4}, which accords with the reported experimental observations. As a result, the adsorbed or substituted Rh atom on Cu catalyst exhibit a better catalytic activity for CH{sub 4} dehydrogenation compared to the pure Cu catalyst, especially on Rh-adsorbed Cu catalyst, we can conclude that the potential of synthesizing high-quality graphene with the

  20. G6PD Deficiency in Turkish Cypriots

    SÖZÜÖZ, Ayşe

    1998-01-01

    1108 Turkish Cypriot men and 318 male labourers from mainland Turkey were screened for G6PD deficiency and haemoglobinopathy traits. The results revealed a 6.7% G6PD deficiency rate in the Turkish Cypriot men and a 1.6% prevalance rate in the Turkish men. The mean haemoglobin level of the G6PD deficient males was approximately 1g/dl lower than that of the non-deficient males.

  1. Congenital longitudinal deficiency of the tibia

    Spiegel, D. A.; Loder, R T; Crandall, R. C.

    2003-01-01

    We performed a clinical and radiographic review of 15 patients (19 limbs) with longitudinal deficiency of the tibia treated between 1981 and 2001. Ten limbs with Kalamchi type I deficiencies were managed by through-knee amputation. Five type II deficiencies were treated by foot ablation and tibiofibular synostosis, either at the same time or staged, but prosthetic problems may arise from varus alignment and prominence of the proximal fibula. Patients with type III deficiencies (four cases) we...

  2. Cobalamin deficiency in children: A literature review

    Moen, Synne Helland

    2013-01-01

    Objective: The aim of this review is to present cobalamin deficiency in children with a specific focus on infants. Background: Cobalamin deficiency is caused by inadequate intake, malabsorption or inborn errors of vitamin B12 metabolism. Cobalamin deficiency in infants is usually caused by deficiency in the mother. There is often a diagnostic delay among infants because the most frequent symptoms are unspecific, e.g., developmental delay, apathy, hypotonia, anorexia and failure to thrive. Chi...

  3. Iron Deficiency in Autism and Asperger Syndrome.

    Latif, A.; Heinz, P.; Cook, R.

    2002-01-01

    Retrospective analysis of the full blood count and, when available, serum ferritin measurements of 96 children (52 with autism and 44 with Asperger syndrome) found six autistic children had iron deficiency and 12 of the 23 autistic children with serum ferritin measures were iron deficient. Far fewer Asperger children were iron deficient. Results…

  4. DNA repair deficiency in neurodegeneration

    Jeppesen, Dennis Kjølhede; Bohr, Vilhelm A; Stevnsner, Tinna V.

    2011-01-01

    Deficiency in repair of nuclear and mitochondrial DNA damage has been linked to several neurodegenerative disorders. Many recent experimental results indicate that the post-mitotic neurons are particularly prone to accumulation of unrepaired DNA lesions potentially leading to progressive...... neurodegeneration. Nucleotide excision repair is the cellular pathway responsible for removing helix-distorting DNA damage and deficiency in such repair is found in a number of diseases with neurodegenerative phenotypes, including Xeroderma Pigmentosum and Cockayne syndrome. The main pathway for repairing oxidative...... base lesions is base excision repair, and such repair is crucial for neurons given their high rates of oxygen metabolism. Mismatch repair corrects base mispairs generated during replication and evidence indicates that oxidative DNA damage can cause this pathway to expand trinucleotide repeats, thereby...

  5. Vitamin D deficiency in Europe

    Cashman, Kevin D.; Dowling, Kirsten G; Škrabáková, Zuzana;

    2016-01-01

    BACKGROUND: Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing...... 25(OH)D values from national health/nutrition surveys. OBJECTIVE: This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D...... deficiency in Europe. DESIGN: The VDSP protocols were applied in 14 population studies [reanalysis of subsets of serum 25(OH)D in 11 studies and complete analysis of all samples from 3 studies that had not previously measured it] by using certified liquid chromatography-tandem mass spectrometry on biobanked...

  6. Muscle phosphoglycerate mutase deficiency revisited

    Naini, Ali; Toscano, Antonio; Musumeci, Olimpia; Vissing, John; Akman, Hasan O; DiMauro, Salvatore

    2009-01-01

    BACKGROUND: Phosphoglycerate mutase (PGAM) deficiency (glycogen storage disease type X) has been reported in 12 patients of whom 9 were African American. OBJECTIVE: To describe 2 patients, 1 of Pakistani and 1 of Italian ethnic origin, with typical clinical and biochemical changes of glycogen...... type X is not confined to the African American population, is often associated with sarcoplasmic reticulum (SR) proliferation, and is genetically heterogeneous....

  7. Primary Carnitine Deficiency and Cardiomyopathy

    Fu, Lijun; Huang, Meirong; Chen, Shubao

    2013-01-01

    Carnitine is essential for the transfer of long-chain fatty acids from the cytosol into mitochondria for subsequent β-oxidation. A lack of carnitine results in impaired energy production from long-chain fatty acids, especially during periods of fasting or stress. Primary carnitine deficiency (PCD) is an autosomal recessive disorder of mitochondrial β-oxidation resulting from defective carnitine transport and is one of the rare treatable etiologies of metabolic cardiomyopathies. Patients affec...

  8. Vitamin D deficiency in Fibromyalgia

    Objective: To check the Vitamin D levels in patients diagnosed as fibromyagia in our population. Methods: Study was done at Medical OPD of Civil Hospital Karachi, from January to March 2009. Female patients diagnosed as Fibromyalgia according to American College of Rheumatology (ACR) criteria and exclusion of systemic illness on examination, and normal reports of blood CP, ESR, serum calcium, phosphate and Alkaline Phosphatase, were asked to get Vitamin D levels in their serum. Vitamin D deficiency is defined as 30 ng/ml. Result: Forty female patients were included in the study. The mean age was 37.65 +- 11.5 years. Mean Vitamin D level was 17.41 +- 5.497 ng/ml. Thirty two (80%) of patients had Vitamin D deficiency, mean levels of 15.855 +- 4.918 ng/ml and 8(20%) had Vitamin D insufficiency, mean levels of 23.64 +- 2.39 ng/ml. Patients with vitamin D deficiency and age less than 45 years were 22 (68.75%), had mean vitamin D level 16.87 +- 4.48 ng/ml whereas in age ranging from 46-75 years were 10 (31.25%) had mean vitamin D level 16.09 +- 6.45 ng/ml. Conclusion: Vitamin D deficiency is frequently seen in patients diagnosed as fibromyalgia and nonspecific musculoskeletal pain in our population. Although the sample size of the study is small, but the figures are so alarming that it is an eye opener towards the need of a population based study, including normal population as well as those presenting with musculoskeletal pain. (author)

  9. Zinc Deficiency in Humans and its Amelioration

    Yashbir Singh Shivay

    2015-01-01

    Zinc (Zn) deficiency in humans has recently received considerable attention. Global mortality in children under 5 years of age in 2004 due to Zn deficiency was estimated at 4,53,207 as against 6,66,771 for vitamin A deficiency; 20,854 for iron deficiency and 3,619 for iodine deficiency. In humans 2800-3000 proteins contain Zn prosthetic group and Zn is an integral component of zinc finger prints that regulate DNA transcription. Zinc is a Type-2 nutrient, which means that its concentration in ...

  10. Microstructure and electrochemical hydrogenation/dehydrogenation performance of melt-spun La-doped Mg{sub 2}Ni alloys

    Hou, Xiaojiang; Hu, Rui; Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Kou, Hongchao; Song, Wenjie; Li, Jinshan

    2015-08-15

    This work focuses on microstructure and electrochemical hydrogen storage properties of La-doped Mg{sub 2}Ni alloys. The alloys with nominal compositions of Mg{sub 2}Ni{sub 1−x}La{sub x} (x = 0, 0.1, 0.3, 0.5) were prepared via metallurgical smelting and melt-spun on a rotating copper wheel. The scanning electron microscope, X-ray diffraction, differential scanning calorimetry and transition electron microscope, galvanostatic charging/discharging and other electrochemical measurements were employed to investigate. The results show that the increasing of La content and melt-spinning speed favors the formation of Mg–Ni–La amorphous/nanocrystalline alloys. It is found that the melt-spun ribbons display increased discharge capacities and superior cycle stabilities compared to the as-cast alloys with and without La. The potentiodynamic polarization results indicate that melt-spun La-doped Mg{sub 2}Ni ribbons possess more positive corrosion potential E{sub corr} and exhibit relatively high corrosion resistance against the alkaline solution. The mechanism for electrochemical hydrogenation/dehydrogenation has been proposed based on the effect of microstructures on the mass/charge transfer process for electrode electrochemical reaction. - Highlights: • Nanocrystalline/amorphous Mg–Ni–La alloys are obtained by melt-spinning. • Microstructures of as-cast and rapid quenched Mg{sub 2}Ni{sub 1−x}La{sub x} alloys are investigated. • Electrochemical hydrogenation properties of experimental alloys are characterized. • Electrochemical hydrogen absorption/desorption mechanism is proposed.

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

    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.

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

    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

  13. In situ formed catalytically active ruthenium nanocatalyst in room temperature dehydrogenation/dehydrocoupling of ammonia-borane from Ru(cod)(cot) precatalyst.

    Zahmakiran, Mehmet; Ayvalı, Tuğçe; Philippot, Karine

    2012-03-20

    The development of simply prepared and effective catalytic materials for dehydrocoupling/dehydrogenation of ammonia-borane (AB; NH(3)BH(3)) under mild conditions remains a challenge in the field of hydrogen economy and material science. Reported herein is the discovery of in situ generated ruthenium nanocatalyst as a new catalytic system for this important reaction. They are formed in situ during the dehydrogenation of AB in THF at 25 °C in the absence of any stabilizing agent starting with homogeneous Ru(cod)(cot) precatalyst (cod = 1,5-η(2)-cyclooctadiene; cot = 1,3,5-η(3)-cyclooctatriene). The preliminary characterization of the reaction solutions and the products was done by using ICP-OES, ATR-IR, TEM, XPS, ZC-TEM, GC, EA, and (11)B, (15)N, and (1)H NMR, which reveal that ruthenium nanocatalyst is generated in situ during the dehydrogenation of AB from homogeneous Ru(cod)(cot) precatalyst and B-N polymers formed at the initial stage of the catalytic reaction take part in the stabilization of this ruthenium nanocatalyst. Moreover, following the recently updated approach (Bayram, E.; et al. J. Am. Chem. Soc.2011, 133, 18889) by performing Hg(0), CS(2) poisoning experiments, nanofiltration, time-dependent TEM analyses, and kinetic investigation of active catalyst formation to distinguish single metal or in the present case subnanometer Ru(n) cluster-based catalysis from polymetallic Ru(0)(n) nanoparticle catalysis reveals that in situ formed Ru(n) clusters (not Ru(0)(n) nanoparticles) are kinetically dominant catalytically active species in our catalytic system. The resulting ruthenium catalyst provides 120 total turnovers over 5 h with an initial turnover frequency (TOF) value of 35 h(-1) at room temperature with the generation of more than 1.0 equiv H(2) at the complete conversion of AB to polyaminoborane (PAB; [NH(2)BH(2)](n)) and polyborazylene (PB; [NHBH](n)) units. PMID:22356554

  14. Influence of preparation conditions of hollow titania–nickel composite spheres on their catalytic activity for hydrolytic dehydrogenation of ammonia borane

    Umegaki, Tetsuo, E-mail: umegaki.tetsuo@nihon-u.ac.jp [Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Ohashi, Takato [Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Xu, Qiang [National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Kojima, Yoshiyuki [Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan)

    2014-04-01

    Highlights: • We study influence of preparation conditions on activity of hollow titania–nickel composite spheres. • The activity for hydrolytic dehydrogenation of NH{sub 3}BH{sub 3} increases with increase of Ti + Ni content. • The activity depends on the amount of PS residue in the hollow spheres. - Abstract: The present work reports influence of preparation conditions of hollow titania–nickel composite spheres on their morphology and catalytic activity for hydrolytic dehydrogenation of ammonia borane (NH{sub 3}BH{sub 3}). The as-prepared hollow titania–nickel composite spheres were characterized by transmission electron microscopy (TEM). Catalytic activities of the hollow spheres for hydrolytic dehydrogenation of aqueous NaBH{sub 4}/NH{sub 3}BH{sub 3} solution improve with the decrease of Ti + Ni content. From the results of FTIR spectra and elemental analysis, the amount of residual polystyrene (PS) templates is able to be reduced by increasing aging time for the preparation, and the catalytic activity of the hollow spheres increases when the amount of residual PS templates decreases. The carbon content in the hollow spheres prepared with aging time = 24 h is 17.3 wt.%, and the evolution of 62 mL hydrogen is finished in about 22 min in the presence of the hollow spheres from aqueous NaBH{sub 4}/NH{sub 3}BH{sub 3} solution. The molar ratio of the hydrolytically generated hydrogen to the initial NH{sub 3}BH{sub 3} in the presence of the hollow spheres is 2.7.

  15. 国内外乙苯脱氢催化剂供需分析%Analysis on Supply and Demand of Ethylbenzene Dehydrogenation Catalyst at Home and Abroad

    王俊琪; 姜宁; 田凤

    2011-01-01

    通过对国内外乙笨脱氧催化剂市场需求、主要生产企业、填装量、工业应用牌号、应用业绩及进出El量等的分析,认为全球苯乙烯产能增长主要集中在亚洲和中东地区,我国是苯乙烯增产最快的国家,国内乙苯脱氢催化剂需求旺盛。未来随着我国苯乙烯新装置的陆续建成,我国苯乙烯的生产能力以及对乙苯脱氧催化剂的需求量也将随之增加,乙苯脱氢制苯乙烯催化剂市场前景良好。%Based on analysis of market supply and demand, major manufactures, loading level, trademarks, application achievements and import and export volume of ethylbenzene dehydrogenation catalyst at home and abroad, it holds that the global increase of styrene capacity is concentrated in Asia and Middle East area, among which China has the highest increasing speed in styrene capacity, so China has high demand on ethylbenzene dehydrogenation catalyst. With the successive completion and operation of newly built styrene plants in China,the production capacity of styrene and demand of ethylbenzene dehydrogenation catalyst will increase therewith, so the catalyst has a good market prospect.

  16. Ethylbenzene dehydrogenation over FeOx/(Mg,Zn)(Al)O catalysts derived from hydrotalcites: Role of MgO as basic sites

    Balasamy, Rabindran J.

    2011-05-01

    A series of Mg3-xZnxFe0.5Al0.5 mixed oxide catalysts derived from hydrotalcites were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The catalysts were prepared by coprecipitation from the nitrates of metal components followed by calcination to mixed oxides at 550 °C. A part of Mg2+ in Mg 3Fe0.5Al0.5 mixed oxide was replaced with Zn2+ to test the effect of MgO as the support. The mixed oxides were composed of periclase and spinel-type compounds with a high surface area of 100-180m2gcat-1. Mössbauer and XPS measurements indicated the presence of Fe3+ on the catalysts and H2-TPR measurement suggested that the dehydrogenation reaction is catalyzed by the reduction-oxidation between Fe3+/Fe2+. The activity of Mg3-xZnxFe0.5Al0.5 mixed oxide decreased with increasing x, indicating an important role of MgO on the activity. Both CO2-TPD measurements as well as IR measurements of adsorbed CO2 clearly indicated the presence of basic sites of Mg 2+O2- on the catalysts. It seems that the combination of Mg2+O2- and Fe3+ was essential for the catalytic activity. It is concluded that the surface base sites generated on O2- bound Mg2+ near Fe3+ sites are responsible for H+-abstraction; the dehydrogenation of ethylbenzene was initiated by the H+ abstraction on Mg2+O2- basic sites, and accelerated by the reduction-oxidation of Fe3+/Fe2+ active species. © 2011 Elsevier B.V.

  17. Regeneration of LOHC dehydrogenation catalysts: In-situ IR spectroscopy on single crystals, model catalysts, and real catalysts from UHV to near ambient pressure

    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.

  18. A liquid-based eutectic system: LiBH4·NH 3-nNH3BH3 with high dehydrogenation capacity at moderate temperature

    Tan, Yingbin

    2011-01-01

    A novel eutectic hydrogen storage system, LiBH4·NH 3-nNH3BH3, which exists in a liquid state at room temperature, was synthesized through a simple mixing of LiBH 4·NH3 and NH3BH3 (AB). In the temperature range of 90-110 °C, the eutectic system showed significantly improved dehydrogenation properties compared to the neat AB and LiBH 4·NH3 alone. For example, in the case of the LiBH4·NH3/AB with a mole ratio of 1:3, over 8 wt.% hydrogen could be released at 90 °C within 4 h, while only 5 wt.% hydrogen released from the neat AB at the same conditions. Through a series of experiments it has been demonstrated that the hydrogen release of the new system is resulted from an interaction of AB and the NH3 group in the LiBH4·NH3, in which LiBH4 works as a carrier of ammonia and plays a crucial role in promoting the interaction between the NH3 group and AB. The enhanced dehydrogenation of LiBH 4·NH3/AB may result from the polar liquid state reaction environments and the initially promoted formation of the diammoniate of diborane, which will facilitate the B-H⋯H-N interaction between LiBH4·NH3 and AB. Kinetics analysis revealed that the rate-controlling steps of the dehydrogenation process are three-dimensional diffusion of hydrogen at temperatures ranging from 90 to 110 °C. This journal is © The Royal Society of Chemistry.

  19. Primary Carnitine (OCTN2) Deficiency Without Neonatal Carnitine Deficiency

    de Boer, L.; Kluijtmans, L.A.J.; Morava, E.

    2012-01-01

    Although the diagnosis of a primary carnitine deficiency is usually based on a very low level of free and total carnitine (free carnitine: 1–5 μM, normal 20–55 μM) (Longo et al. 2006), we detected a patient via newborn screening with a total carnitine level 67 % of the normal value. At the age of 1 year, after interruption of carnitine supplementation for a 4-week period the carnitine profile was assessed and the free carnitine level had dropped to 10.4 μmol/l (normal: 20–55 μM) and total car...

  20. Deficiencies in the Management of Iron Deficiency Anemia During Childhood.

    Powers, Jacquelyn M; Daniel, Catherine L; McCavit, Timothy L; Buchanan, George R

    2016-04-01

    Limited high-quality evidence supports the management of iron deficiency anemia (IDA). To assess our institutional performance in this area, we retrospectively reviewed IDA treatment practices in 195 consecutive children referred to our center from 2006 to mid-2010. The majority of children were ≤4 years old (64%) and had nutritional IDA (74%). In 11- to 18-year-old patients (31%), the primary etiology was menorrhagia (42%). Many were referred directly to the emergency department and/or prescribed iron doses outside the recommended range. Poor medication adherence and being lost-to-follow-up were common. Substantial improvements are required in the management of IDA. PMID:26728130

  1. Iminoiodane- and Brønsted Base-Mediated Cross Dehydrogenative Coupling of Cyclic Ethers with 1,3-Dicarbonyl Compounds

    Ciputra Tejo

    2015-07-01

    Full Text Available A one-pot, two-step approach to prepare 2-tetrahydrofuran and -pyran substituted 1,3-dicarbonyl compounds by PhI=NTs-mediated amination/Brønsted base-catalyzed cross dehydrogenative coupling (CDC reaction of the cyclic ether and 1,3-dicarbonyl derivative under mild conditions is reported. The reaction is compatible with a variety of cyclic ethers and 1,3-dicarbonyl compounds, affording the corresponding coupled products in moderate to good yields of up to 80% over two steps.

  2. Revisitation of the βCl-Elimination Reaction of d-Amino Acid Oxidase: NEW INTERPRETATION OF THE REACTION THAT SPARKED FLAVOPROTEIN DEHYDROGENATION MECHANISMS*

    Ghisla, Sandro; Pollegioni, Loredano; Molla, Gianluca

    2011-01-01

    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 DAA...

  3. In situ transmission electron microscopy study on microstructural changes in NbF5-doped MgH2 during dehydrogenation

    Microstructural changes in NbF5-doped MgH2 during the dehydrogenation reaction (MgH2 → Mg + H2) have been investigated by in situ heating transmission electron microscopy. Nanocrystalline MgH2 shows fast hydrogen sorption kinetics, as well as a high density of defects induced by high-energy ball milling. Since the network-structured Nb layer covering Mg grains acts both as an impediment to grain growth of Mg and a gateway for hydrogen diffusion by forming metastable NbH1-x, the improved kinetics can be maintained during hydrogen cycling.

  4. Oxidative dehydrogenation of propane with N2O over Fe-ZSM-5 and Fe-SiO2: Influence of the iron species and acid sites

    Ates, Ayten; Hardacre, Christopher; Goguet, Alexandre

    2012-01-01

    A series of iron containing zeolites with varying Si/Al ratios (11.5-140) and low iron content (similar to 0.9 wt.% Fe) have been synthesised by solid-state ion exchange with commercially available zeolites and tested, for the first time, in the oxidative dehydrogenation of propane (ODHP) with N2O. The samples were characterised by XRD, N-2-Adsorption, NH3-TPD and DR-UV-vis spectroscopy. The acidity of the Fe-ZSM-5 can be controlled by high temperature and steam treatments and Si/Al ratio. Th...

  5. Modifications induced by potassium addition on chromia/alumina catalysts and their influence on the catalytic activity for the oxidative dehydrogenation of propane

    The oxidative dehydrogenation of propane was investigated on K-containing chromia/alumina catalysts, with nominal Cr and K loadings of 10 and 0-2 wt%, respectively. Their chemical composition, structure, texture, nature of surface species, redox features and surface acidity were determined. Catalytic behaviour was investigated in a continuous-flow micro-reactor under different conditions. Besides the nature and concentration of the chromium species, potassium addition was found to affect the reducibility of the catalysts as well as their acid surface features. Such modifications were found to condition the catalytic behaviour, which appeared somewhat peculiar in comparison with that of the catalytic systems reported in literature.

  6. Effect of the plasma-chemical treatment of ZnO and NiO on their activity in the dehydrogenation of isopropanol

    Danilova, M. N.; Pylinina, A. I.; Platonov, E. A.; Yagodovskii, V. D.

    2015-08-01

    Treating ZnO and NiO oxides with glow discharge oxygen plasma and high-frequency argon plasma is found to affect the catalytic activity of these oxides in the dehydrogenation reaction of isopropanol, leading to an increase in the conversion of alcohol and the yield of acetone. The increased activity of ZnO is due to the high number of acid sites induced by plasma-chemical treatment. With NiO, the increased activity results from the formation of new, more active sites with low experimental activation energy, rather than a change in the surface acidity.

  7. Catalytic Dehydrogenation over Pd-Supported ZSM-5 Zeolite for o-Phenylphenol Synthesis%载钯ZSM-5分子筛催化脱氢合成邻苯基苯酚

    蔡春; 吕春绪

    2001-01-01

    Pd-supported ZSM-5 zeolites prepared through ion exchange technique were used as a dehydrogenation catalyst for synthesis of o-phenylphenol from cyclohexanone. When Si/A1 ratio in the catalyst was 85: 1 or more, an obvious reduction in attenuation rate of catalyst activity was observed.When the Si/Al ratio was of 17 . 1 or less, polymer compounds could be formed on the surface of zeolite, that would decrease the dehydrogenation activity due to the reduction of the specific surface area of the catalyst.

  8. Carnitine deficiency disorders in children.

    Stanley, Charles A

    2004-11-01

    Mitochondrial oxidation of long-chain fatty acids provides an important source of energy for the heart as well as for skeletal muscle during prolonged aerobic work and for hepatic ketogenesis during long-term fasting. The carnitine shuttle is responsible for transferring long-chain fatty acids across the barrier of the inner mitochondrial membrane to gain access to the enzymes of beta-oxidation. The shuttle consists of three enzymes (carnitine palmitoyltransferase 1, carnitine acylcarnitine translocase, carnitine palmitoyl-transferase 2) and a small, soluble molecule, carnitine, to transport fatty acids as their long-chain fatty acylcarnitine esters. Carnitine is provided in the diet (animal protein) and also synthesized at low rates from trimethyl-lysine residues generated during protein catabolism. Carnitine turnover rates (300-500 micromol/day) are benefit in genetic or acquired disorders of energy production to improve fatty acid oxidation, to remove accumulated toxic fatty acyl-CoA metabolites, or to restore the balance between free and acyl-CoA. Two disorders have been described in children where the supply of carnitine becomes limiting for fatty acid oxidation: (1) A recessive defect of the muscle/kidney sodium-dependent, plasma membrane carnitine symporter, which presents in infancy with cardiomyopathy or hypoketotic hypoglycemia; treatment with oral carnitine is required for survival. (2) Chronic administration of pivalate-conjugated antibiotics in which excretion of pivaloyl-carnitine can lead to carnitine depletion; tissue levels may become low enough to limit fatty acid oxidation, although no cases of illness due to carnitine deficiency have been described. There is speculation that carnitine supplements might be beneficial in other settings (such as genetic acyl-CoA oxidation defects--"secondary carnitine deficiency", chronic ischemia, hyperalimentation, nutritional carnitine deficiency), but efficacy has not been documented. The formation of abnormal

  9. Vitamin D deficiency and stroke

    2012-12-01

    Full Text Available Vitamin D comprises a group of fat-soluble pro-hormones, obtained from sun exposure, food, and supplements, and it must undergo two hydroxylation reactions to be activated in the body. Several studies have shown the role of vitamin D in mineral metabolism regulation, especially calcium, phosphorus, and bone metabolism. Some factors such as inadequate vitamin intake and liver or kidney disorders can lead to vitamin D deficiency. Furthermore, vitamin D malnutrition may also be linked to susceptibility to chronic diseases such as heart failure, peripheral artery disease, high blood pressure, cognitive impairment including foggy brain and memory loss, and autoimmune diseases including diabetes type I. Recent research has revealed that low levels of vitamin D increase the risk of cardiovascular-related morbidity (Sato et al., 2004 and mortality (Pilz et al., 2008. Also, hypertension contributes to a reduction in bone mineral density and increase in the incidence of stroke and death. This article reviews the function and physiology of vitamin D and examines the effects of vitamin D deficiency on susceptibility to stroke, as a cardiovascular event, and its morbidity and subsequent mortality.

  10. Organometallic Model Complexes Elucidate the Active Gallium Species in Alkane Dehydrogenation Catalysts Based on Ligand Effects in Ga K-Edge XANES

    Getsoian, Andrew ' Bean' ; Das, Ujjal; Camacho-Bunquin, Jeffrey; Zhang, Guanghui; Gallagher, James R.; Hu, Bo; Cheah, Singfoong; Schaidle, Joshua A.; Ruddy, Daniel A.; Hensley, Jesse E.; Krause, Theodore R.; Curtiss, Larry A.; Miller, Jeffrey T.; Hock, Adam S.

    2016-08-21

    Gallium-modified zeolites are known catalysts for the dehydrogenation of alkanes, reactivity that finds industrial application in the aromatization of light alkanes by Ga-ZSM5. While the role of gallium cations in alkane activation is well known, the oxidation state and coordination environment of gallium under reaction conditions has been the subject of debate. Edge shifts in Ga K-edge XANES spectra acquired under reaction conditions have long been interpreted as evidence for reduction of Ga(III) to Ga(I). However, a change in oxidation state is not the only factor that can give rise to a change in the XANES spectrum. In order to better understand the XANES spectra of working catalysts, we have synthesized a series of molecular model compounds and grafted surface organometallic Ga species and compared their XANES spectra to those of gallium-based catalysts acquired under reducing conditions. We demonstrate that changes in the identity and number of gallium nearest neighbors can give rise to changes in XANES spectra similar to those attributed in literature to changes in oxidation state. Specifically, spectral features previously attributed to Ga(I) may be equally well interpreted as evidence for low-coordinate Ga(III) alkyl or hydride species. These findings apply both to gallium-impregnated zeolite catalysts and to silica-supported single site gallium catalysts, the latter of which is found to be active and selective for dehydrogenation of propane and hydrogenation of propylene.

  11. Dehydrogenation of propane in the presence of CO{sub 2} over polyacid chromium oxide catalysts modified by Mo, W and Mn

    Lapidus, A.L.; Agafonov, Yu.A.; Gaidai, N.A.; Nekrasov, N.V.; Davydov, P.E. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Institute of Organic Chemistry

    2013-11-01

    Effective chromium oxide catalysts without additions and with addition of Mo, W and Mn were prepared and tested in long-duration experiments for propane dehydrogenation in the presence of CO{sub 2}. The optimal concentrations of metals were found. It was shown that the best combination of acid-base and redox properties necessary for a decrease of aggregation of chromium-oxide particles was observed over the following catalyst: (3.0 wt.%Cr-1.5 wt.% Mn)/SiO{sub 2}. This catalyst worked stably in durable tests (500 h). Mechanism of propane oxidative dehydrogenation was studied using unstationary response method. It was shown that the process mechanism was similar over all studied catalysts but the catalysts were differed by the adsorption capacity of the reaction components: CO{sub 2} was tied more firmly than C{sub 3}H{sub 6} over Cr and Cr-Mn, C{sub 3}H{sub 6} was tied more strongly than CO{sub 2} over Cr-W. The reverse water-gas shift reaction proceeded in more extent over chromium-oxide catalysts without additions. (orig.)

  12. Novel Flower-Like Ag-SiO2-MgO-Al2O3 Material: Preparation, Characterization and Catalytic Application in Methanol Dehydrogenation

    LI,Jing-Xia; REN,Li-Ping; DAI,Wei-Lin; CAO,Yong; FAN,Kang-Nian

    2008-01-01

    Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag-SiO2-MgO-Al2O3 catalysts prepared by sol-gel method.The optimal preparation mass fractions were determined as 8.3% MgO,16.5% Al2O3 and 20% silver loading.Using this optimum catalyst,excellent activity and selectivity were obtained.The conversion of methanol and the selectivity to formaldehyde both reached 100%,which were much higher than other previously reported silver supported catalysts.Based on combined characterizations,such as X-ray diffraction (XRD),scanning electronic microscopy (SEM),diffuse reflectance ultraviolet-visible spectroscopy (UV-Vis,DRS),nitrogen adsorption at low temperature,temperature programmed desorption of ammonia (NH3-TPD),desorption of CO2 (CO2-TPD),etc.,the correlation of the catalytic performance to the structural properties of the Ag-SiO2-MgO-Al2O3 catalyst was discussed in detail.This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side-products is attributed to its unique flower-like structure with a surface area less than 1 m2/g,and the strong interactions between neutralized support and the nano-sized Ag particles as active centers.

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

    Miguel Menéndez

    2013-05-01

    Full Text Available 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.

  14. The Effect of Sulphate Doping on Nanosized TiO2 and MoOx/TiO2 Catalysts in Cyclohexane Photooxidative Dehydrogenation

    P. Ciambelli

    2008-01-01

    Full Text Available The effect of sulphate doping of titania in promoting activity and selectivity of MoOx/TiO2 catalysts for the cyclohexane photooxidative dehydrogenation has been investigated in a gas-solid fluidized bed reactor. Sulphate and/or molybdate-modified titania catalysts were prepared by incipient wet impregnation of nanosized (5–10 nm crystallite size samples. At 60% of titania surface coverage by MoOx, sulphate surface density was obtained up to 19 μmol/m2 without formation of MoO3. The catalysts were characterized by N2 adsorption-desorption at −196∘C, micro-Raman and UV-visible reflectance spectroscopy, thermogravimetric analysis coupled with mass spectroscopy (TG-MS, and mass titration. Unsulphated and sulphated titania are both active in cyclohexane total oxidation, but sulphate doping of titania has a detrimental effect on the reaction rate. On Mo-based catalysts, polymolybdate species enabled sulphated titania to convert cyclohexane to benzene (99% selectivity and cyclohexene, reducing at zero the formation of CO2. Cyclohexane conversion to benzene is almost linearly dependent on sulphate surface density, resulting in enhanced yield to benzene. The enhanced photooxidative dehydrogenation activity and benzene yield by sulphate doping could be attributed to the increase of surface acidity and, as a consequence, of cyclohexane adsorption.

  15. Defining Active Catalyst Structure and Reaction Pathways from ab Initio Molecular Dynamics and Operando XAFS: Dehydrogenation of Dimethylaminoborane by Rhodium Clusters

    Rousseau, Roger J.; Schenter, Gregory K.; Fulton, John L.; Linehan, John C.; Engelhard, Mark H.; Autrey, Thomas

    2009-08-05

    We present the results of a detailed operando XAFS and density functional theory (DFT) based ab initio molecular dynamics (AIMD) investigation of the proposed mechanism of dehydrogenation of dimethylaminoborane (DMAB) by a homogeneous Rh4 cluster catalyst. Our AIMD simulations reveal that the previously proposed Rh structures are highly fluxional exhibiting both metal cluster and ligand isomerizations and dissociaton which can only be accounted for by a examining finite temperature ensemble as generated by AIMD. It is found that a highly fluxional species Rh4((H2BNMe2)82+ is fully compatible with operando XAFS measurements which suggest that this species may be the catalyst resting state. Based on this assignment we propose a catalytic mechanism for DMAB dehydrogenation which exhibits a maximum energy barrier of 24 kcal/mol, which is half that observed for the uncatalyzed thermal reaction. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program, and was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a DOE national scientific user facility located at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. Department of Energy.

  16. Size effects in C2H4 dehydrogenation studied by HR-PES: Pt(111) versus Pt/CeO2/Cu(111) model catalysts

    Complex catalysts consisting of noble metal particles on reducible CeO2 supports show unique reactivity and reduced carbon precipitation during hydrocarbon reforming. In order to explore these effects at the microscopic level, we have studied the adsorption and dehydrogenation of C2H4 on a Pt/CeO2(111)/Cu(111) and Pt(111)model catalysts. Reaction and decomposition of C2H4 are investigated by means of HR-PES as a function of the CeO2-x stoichiometry and Pt particle size. In contrast to the behavior on Pt(111), where molecular adsorption of C2H4 is observed, dissociation intermediates, namely CCH3 and CHCH3, were found on the Pt nanoparticles even at 100 K. The dehydrogenation of these products to carbonaceous deposits is accompanied by the hydrogen spillover and formation of hydroxyl groups on ceria. The decomposition of the hydroxyl groups and desorption of H2 occurs at 450 K. At higher temperatures, carbonaceous species react with oxygen, which is supplied via reverse spillover from the ceria and, subsequently, desorb in the form of CO and/or CO2.

  17. Synthesis of defect-rich, (001) faceted-ZnO nanorod on a FTO substrate as efficient photocatalysts for dehydrogenation of isopropanol to acetone

    Tan, Sin Tee; Umar, Akrajas Ali; Salleh, Muhamad Mat

    2016-06-01

    Highly oriented ZnO nanorod was successfully synthesised on Ag nanoseed coated FTO substrate via a microwave hydrolysis approach. It was found that the morphology and the optical properties of the ZnO nanorod are strongly influenced by the power of the microwave irradiation used during the growth process. The aspect ratio of the nanorods changed from high to low with the increasing of microwave power. It was also found that the optical band gap of the ZnO nanorod red shifted with the increasing of the microwave power, reflecting an excellent tune ability of the optical properties of ZnO nanorods. The photocatalytic activity of these unique nanorod was evaluated by a dehydrogenation process of isopropanol to acetone in the presence of ZnO nanorod. It was found that the ZnO nanorod exhibited an excellent catalytic performance by showing an ability to accelerate the production of 0.031 mol L-1 of acetone within only 35 min or 0.9 mmol L-1 min-1 from isopropyl alcohol dehydrogenation. It was almost no conversion from isopropyl alcohol when ZnO nanorods was absence during the reaction. In this report, a detailed mechanism of ZnO nanorod formation and the relationship between morphology and optical energy band gap are described.

  18. Evaluation of the Parameters and Conditions of Process in the Ethylbenzene Dehydrogenation with Application of Permselective Membranes to Enhance Styrene Yield

    Araújo, Paulo Jardel P.; Leite, Manuela Souza; Kakuta Ravagnani, Teresa M.

    2016-01-01

    Styrene is an important monomer in the manufacture of thermoplastic. Most of it is produced by the catalytic dehydrogenation of ethylbenzene. In this process that depends on reversible reactions, the yield is usually limited by the establishment of thermodynamic equilibrium in the reactor. The styrene yield can be increased by using a hybrid process, with reaction and separation simultaneously. It is proposed using permselective composite membrane to remove hydrogen and thus suppress the reverse and secondary reactions. This paper describes the simulation of a dehydrogenation process carried out in a tubular fixed-bed reactor wrapped in a permselective composite membrane. A mathematical model was developed, incorporating the various mass transport mechanisms found in each of the membrane layers and in the catalytic fixed bed. The effects of the reactor feed conditions (temperature, steam-to-oil ratio, and the weight hourly space velocity), the fixed-bed geometry (length, diameter, and volume), and the membrane geometry (thickness of the layers) on the styrene yield were analyzed. These variables were used to determine experimental conditions that favour the production of styrene. The simulation showed that an increase of 40.98% in the styrene yield, compared to a conventional fixed-bed process, could be obtained by wrapping the reactor in a permselective composite membrane. PMID:27069982

  19. Vitamin B12 deficiency and depression

    Milanlıoğlu, Aysel

    2011-01-01

    Vitamin B12 deficiency may cause psychiatric manifestations preceding the hematological and neurological symptoms. Despite a variety of symptoms, data on the role of vitamin B12 deficiency in depression are sparse. We report a case with B12 deficiency that is diagnosed with psychotic depression and treated successively with vitamin B12 replacement instead of using conventional therapy. Future investigations should focus on the role of vitamin B12 status in depression and other neurops...

  20. Atypical B12 Deficiency with Nonresolving Paraesthesia

    Haider, S.; Ahmad, N; Anaissie, E J; Abdel Karim, N.

    2013-01-01

    Vitamin B12 deficiency can present with various hematological, gastrointestinal and neurological manifestations. We report a case of elderly female who presented with neuropathy and vitamin B12 deficiency where the final work-up revealed polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS). This case suggests that, although POEMS syndrome is a rare entity, it can present with vitamin-B12 deficiency and thus specific work up for early diagnosis of P...

  1. Multispectral Analysis of Color Vision Deficiency Tests

    Sergejs FOMINS; Ozolinsh, Maris

    2011-01-01

    Color deficiency tests are usually produced by means of polygraphy technologies and help to diagnose the type and severity of the color deficiencies. Due to different factors, as lighting conditions or age of the test, standard characteristics of these tests fail, thus not allowing diagnosing unambiguously the degree of different color deficiency. Multispectral camera was used to acquire the spectral images of the Ishihara and Rabkin pseudoisochromatic plates in the visible spectrum. Spectral...

  2. Prevalence of Color Vision Deficiency in Qazvin

    Mohammad khalaj; Ameneh Barikani; Mozhgan Mohammadi

    2014-01-01

    Background: Color vision deficiency (CVD) is an X chromosome-linked recessive autosomal dominant. Determine the prevalence of color blindness in Qazvin population. Materials and Methods: In a cross sectional study color vision deficiency examined in 1853 individuals with age 10-25 years old who participated in private clinics and eye clinic of Bu-Ali hospital in Qazvin in 2010. The screening of color vision deficiency was performed using Ishihara test. Data were analyzed by SPSS-16 with χP...

  3. SEAWEED SUPPLEMENTATION TO PREVENT IODINE DEFICIENCY

    Juhi Agarwal; Sirimavo Nair

    2012-01-01

    Iodine is considered as one of the essential elements for the proper functioning of the hormones of human and animal thyroid glands. In many parts of the world iodine deficiency disorders develop because of deficiency of iodine in water and food supply. An iodine deficient goitrous mother may give birth to a cretinous baby because the fetus requires an adequate secretion of thyroxine during the later stages of pregnancy. Seaweed has such a large proportion of iodine compared to dietary minimu...

  4. Vitamin B12 deficiency and depression

    Aysel Milanlıoğlu

    2011-01-01

    Vitamin B12 deficiency may cause psychiatric manifestations preceding the hematological and neurological symptoms. Despite a variety of symptoms, data on the role of vitamin B12 deficiency in depression are sparse.We report a case with B12 deficiency that is diagnosed with psychotic depression and treated successively with vitamin B12 replacement instead of using conventional therapy.Future investigations should focus on the role of vitamin B12 status in depression and other neuropsychiatric ...

  5. Treatment of Iron Deficiency in Women

    Breymann, C; Römer, T.; Dudenhausen, J. W.

    2013-01-01

    Iron deficiency with and without anaemia is a common cause of morbidity, particularly in women. Iron deficiency is generally the result of an imbalance between iron loss and iron absorption. In women with symptoms suspicious for iron deficiency, it is important to confirm or exclude the suspicion using proper tests. The use of serum ferritin levels is considered the gold standard for diagnosis. Although the ideal ferritin levels are not unknown the current consent is that le...

  6. Vitamin D Deficiency in Early Pregnancy

    Flood-Nichols, Shannon K.; Tinnemore, Deborah; Huang, Raywin R.; Napolitano, Peter G.; Ippolito, Danielle L.

    2015-01-01

    Objective Vitamin D deficiency is a common problem in reproductive-aged women in the United States. The effect of vitamin D deficiency in pregnancy is unknown, but has been associated with adverse pregnancy outcomes. The objective of this study was to analyze the relationship between vitamin D deficiency in the first trimester and subsequent clinical outcomes. Study Design This is a retrospective cohort study. Plasma was collected in the first trimester from 310 nulliparous women with singlet...

  7. Vitamin D Deficiency in Children and Adolescents

    Andıran, Nesibe; Çelik, Nurullah; AKÇA, Halise; Doğan, Güzide

    2012-01-01

    Objective Vitamin D deficiency is an important health problem in both developed and developing countries. Recent reports on the extraskeletal effects of vitamin D have led to increased interest in prevalence studies on states of deficiency/insufficiency of vitamin D. The aim of this study was to determine the frequency of vitamin D deficiency and insufficiency in children and adolescents residing in Ankara, Turkey and to investigate the factors associated with low vitamin D status. Methods: A...

  8. In situ NMR study of hydrogenation/dehydrogenation of ZrCr{sub 2} and physisorbed hydrogen

    Ahmad, Jamil, E-mail: mjasomba@gmail.com [Graduate School of Engineering, Tohoku University (Japan); Maekawa, Hideki; Takamura, Hitoshi; Oikawa, Itaru; Ando, Mariko; Takahashi, Kuniaki [Graduate School of Engineering, Tohoku University (Japan)

    2012-11-05

    Highlights: Black-Right-Pointing-Pointer In situ NMR study of hydrogenation of C14-ZrCr{sub 2}. Black-Right-Pointing-Pointer Observation of physisorbed hydrogen peak in NMR spectra. Black-Right-Pointing-Pointer Change of chemical shift of physisorbed H{sub 2} ({delta}{sub phy}) with degree of hydrogenation. Black-Right-Pointing-Pointer Linearity between {delta}{sub phy} and degree of hydrogenation. Black-Right-Pointing-Pointer Linearity between degree of hydrogenation and density of states, N{sub d}(E{sub F}). - Abstract: In situ proton nuclear magnetic resonance (NMR) was employed to study the hydrogenation and dehydrogenation kinetics of ZrCr{sub 2}. The powder samples prepared by arc melting followed by homogenizing heat treatment and grinding were put inside a boron nitride (BN) crucible, which was placed inside a quartz tube attached to a high pressure assembly specially designed for in situ NMR measurements. The samples were activated at 573 K under vacuum inside the high temperature probe and then exposed to the required hydrogen gas pressure at room temperature for hydrogenation. Gradual hydrogenation of the samples was recorded through in situ NMR. Before activation of the sample, the exposure to high pressure showed two peaks with NMR shifts of 8.5 and -3.3 ppm, which were assigned to hydrogen gas and physisorbed hydrogen, respectively. After activation, the sample showed absorption manifested through the appearance of a broad peak with an NMR shift of -141 ppm. The NMR shift of absorption peak increased to higher magnetic fields as the hydrogen absorption proceeded. It was also accompanied by a change in NMR shift of physisorbed hydrogen peak in the same direction. Both the shifts, i.e., of absorbed hydrogen as well as of physisorbed hydrogen were linearly related with the degree of hydrogenation. This change in NMR shift of physisorbed hydrogen was explained on the basis of increase in density of d-electronic states at Fermi level with an increase in

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

    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

  10. Genetics Home Reference: common variable immune deficiency

    ... 2 links) National Institute of Allergy and Infectious Diseases: Immune System National Institute of Allergy and Infectious Diseases: Primary Immune Deficiency Diseases Educational Resources (8 links) Boston Children's ...

  11. Congenital longitudinal deficiency of the tibia.

    Spiegel, D A; Loder, R T; Crandall, R C

    2003-01-01

    We performed a clinical and radiographic review of 15 patients (19 limbs) with longitudinal deficiency of the tibia treated between 1981 and 2001. Ten limbs with Kalamchi type I deficiencies were managed by through-knee amputation. Five type II deficiencies were treated by foot ablation and tibiofibular synostosis, either at the same time or staged, but prosthetic problems may arise from varus alignment and prominence of the proximal fibula. Patients with type III deficiencies (four cases) were treated by foot ablation. Prosthetic problems relating to proximal or distal tibiofibular instability may necessitate additional surgical intervention. PMID:12879290

  12. Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra

    Marashdeh, A.; Frankcombe, T.J.

    2008-01-01

    The dehydrogenation enthalpies of Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4 have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski’s direct method. The dehydrog

  13. Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra.

    Marashdeh, Ali; Frankcombe, Terry J

    2008-06-21

    The dehydrogenation enthalpies of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski's direct method. The dehydrogenation of Ca(AlH(4))(2) is exothermic, indicating a metastable hydride. Calculations for CaAlH(5) including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH(4) with CaH(2) is a promising system after ZPE-corrected enthalpy calculations. The calculations confirm that including ZPE effects in the harmonic approximation for the dehydrogenation of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca(AlH(4))(2) and CaAlH(5) calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH(5) is presented in the more useful standard setting of P2(1)c symmetry and the phonon density of states of CaAlH(5), significantly different to other common complex metal hydrides, is rationalized. PMID:18570508

  14. Glucose-6-phosphate Dehydrogenase Deficiency and Malaria: Cytochemical Detection of Heterozygous G6PD Deficiency in Women

    Peters, Anna L.; Van Noorden, Cornelis J. F.

    2009-01-01

    Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a X-chromosomally transmitted disorder of the erythrocyte that affects 400 million people worldwide. Diagnosis of heterozygously-deficient women is complicated: as a result of lyonization, these women have a normal and a G6PD-deficient population of erythrocytes. The cytochemical assay is the only reliable assay to discriminate between heterozygously-deficient women and non-deficient women or homozygously-deficient women. G6PD deficiency ...

  15. Photodissociation of neutron deficient nuclei

    Sonnabend, K.; Babilon, M.; Hasper, J.; Mueller, S.; Zarza, M.; Zilges, A. [TU Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany)

    2006-03-15

    The knowledge of the cross sections for photodissociation reactions like e.g. ({gamma}, n) of neutron deficient nuclei is of crucial interest for network calculations predicting the abundances of the so-called p nuclei. However, only single cross sections have been measured up to now, i.e., one has to rely nearly fully on theoretical predictions. While the cross sections of stable isotopes are accessible by experiments using real photons, the bulk of the involved reactions starts from unstable nuclei. Coulomb dissociation (CD) experiments in inverse kinematics might be a key to expand the experimental database for p-process network calculations. The approach to test the accuracy of the CD method is explained. (orig.)

  16. Photodissociation of neutron deficient nuclei

    Sonnabend, K.; Babilon, M.; Hasper, J.; Müller, S.; Zarza, M.; Zilges, A.

    2006-03-01

    The knowledge of the cross sections for photodissociation reactions like e.g. (γ, n) of neutron deficient nuclei is of crucial interest for network calculations predicting the abundances of the so-called p nuclei. However, only single cross sections have been measured up to now, i.e., one has to rely nearly fully on theoretical predictions. While the cross sections of stable isotopes are accessible by experiments using real photons, the bulk of the involved reactions starts from unstable nuclei. Coulomb dissociation (CD) experiments in inverse kinematics might be a key to expand the experimental database for p-process network calculations. The approach to test the accuracy of the CD method is explained.

  17. [Iron deficiency in the elderly].

    Helsen, Tuur; Joosten, Etienne

    2016-06-01

    Anemia is a common diagnosis in the geriatric population, especially in institutionalized and hospitalized elderly. Most common etiologies for anemia in elderly people admitted to a geriatric ward are iron-deficiency anemia and anemia associated with chronic disease.Determination of serum ferritin is the most used assay in the differential diagnosis, despite low sensitivity and moderate specificity. New insights into iron homeostasis lead to new diagnostic assays such as serum hepcidin, serum transferrin receptor and reticulocyte hemoglobin equivalent.Importance of proper diagnosis and treatment for this population is large since there is a correlation between anemia and morbidity - mortality. Anemia is usually defined as hemoglobin less than 12 g/dl for women and less than 13 g/dl for men. There is no consensus for which hemoglobinvalue an investigation into underlying pathology is obligatory. This needs to be evaluated depending on functional condition of the patient. PMID:27106490

  18. Academic Deficiency: Student Experiences of Institutional Labeling

    Barouch-Gilbert, Abraham

    2015-01-01

    Limited existing research examines how undergraduate students in the United States experience the process of being identified as deficient due to their academic performance. The purpose of this phenomenological study was to explore the lived experiences of college students on academic probation who were labeled academically deficient. Students…

  19. Short Stature and Growth Hormone Deficiency

    Matemi, Sezer

    1994-01-01

    This paper summarizes the importance of measurements of height and weight in normal children and emphasizes the role of growth increments for the diagnosis of short stature Causes of short stature methods for diagnosis of GH hormone deficiency actions of growth hormone treatment of growth hormone deficiency and doses for biosynthetic GH treatment are described Key words: Short Stature Growth Hormone

  20. Growth Hormone Deficiency, Brain Development, and Intelligence

    Meyer-Bahlburg, Heino F. L.; And Others

    1978-01-01

    Available from: American Medical Association, 535 N. Dearborn Street, Chicago, Illinois 60610. In order to determine what effect, if any, growth hormone (GH) has on human brain development, 29 patients (mean age 11.7 years) with GH deficiency were selected according to the following criteria: no evidence of reversible GH deficiency, onset of…

  1. Genetics Home Reference: beta-ketothiolase deficiency

    ... Test Genetic Testing Registry: Deficiency of acetyl-CoA acetyltransferase These resources from MedlinePlus offer information about the ... Testing Registry (1 link) Deficiency of acetyl-CoA acetyltransferase ACT Sheets (1 link) Elevated C5-OH Acylcarnitine ...

  2. Acquired Zinc Deficiency in an Adult Female

    Mohanan Saritha; Divya Gupta; Laxmisha Chandrashekar; Devinder M Thappa; Nachiappa G Rajesh

    2012-01-01

    Acrodermatitis enteropathica is an autosomal recessive inherited disorder of zinc absorption. Acquired cases are reported occasionally in patients with eating disorders or Crohn′s disease. We report a 24-year-old housewife with acquired isolated severe zinc deficiency with no other comorbidities to highlight the rare occurrence of isolated nutritional zinc deficiency in an otherwise normal patient.

  3. Genetics Home Reference: pyruvate kinase deficiency

    ... National (UK) Information Centre for Metabolic Diseases National Organization for Rare Disorders (NORD): Pyruvate Kinase Deficiency Genetic Testing Registry (1 link) Pyruvate kinase deficiency of red cells Scientific articles on PubMed (1 link) PubMed OMIM (1 link) ...

  4. Genetics Home Reference: pyruvate dehydrogenase deficiency

    ... the most common cause of pyruvate dehydrogenase deficiency , accounting for approximately 80 percent of cases. These mutations ... deficiency ClinicalTrials.gov (1 link) ClinicalTrials.gov Scientific articles on PubMed (1 link) PubMed OMIM (5 links) ...

  5. 30 CFR 57.5015 - Oxygen deficiency.

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen....

  6. Genetics Home Reference: complement factor I deficiency

    ... the complement system decreases blood levels of another complement protein called C3, reducing the immune system's ability to fight infections. ... in my area? Other Names for This Condition C3 inactivator deficiency complement component 3 inactivator deficiency Related Information How are ...

  7. How common is vitamin B12 deficiency?

    In considering the vitamin B-12 fortification of flour, it is important to know who is at risk of vitamin B-12 deficiency and whether those individuals would benefit from flour fortification.This article reviews current knowledge of the prevalence and causes of vitamin B-12 deficiency and considers ...

  8. Breath hydrogen test and sucrase isomaltase deficiency.

    Ford, R P; Barnes, G L

    1983-01-01

    Sucrose breath hydrogen tests were performed on 7 children with proved sucrase isomaltase deficiency. All children had raised breath hydrogen excretion. The amount of hydrogen produced and symptoms experienced increased with increasing sucrose loads. The sucrose breath hydrogen test appears to be a reliable indicator of sucrose malabsorption in sucrase isomaltase deficiency.

  9. Growth hormone deficiency and hyperthermia during exercise

    Juul, A; Hjortskov, N; Jepsen, Leif;

    1995-01-01

    Sweat secretion is often disturbed in patients with GH secretory disorders. Hyperhidrosis is a classic feature of acromegaly, and it has recently been shown that GH-deficient patients exhibit decreased sweating capacity after pilocarpine stimulation of the skin. Thus, patients with GH-deficiency ...

  10. [Vitamin B12 deficiency in the elderly].

    Leischker, A H; Kolb, G F

    2015-01-01

    The prevalence of vitamin B12 deficiency increases with age. Patients with dementia and spouses of patients with dementia are at special risk for the development of vitamin B12 deficiency. In a normal diet this vitamin is present only in animal source foods; therefore, vegans frequently develop vitamin B12 deficiency if not using supplements or foods fortified with cobalamin. Apart from dementia, most of these manifestations are completely reversible under correct therapy; therefore it is crucial to identify and to treat even atypical presentations of vitamin B12 deficiency as early as possible. This article deals with the physiology and pathophysiology of vitamin B12 metabolism. A practice-oriented algorithm which also considers health economic aspects for a rational laboratory diagnosis of vitamin B12 deficiency is presented. In cases with severe neurological symptoms, therapy should be parenteral, especially initially. For parenteral treatment, hydroxocobalamin is the drug of choice. PMID:25586321

  11. Prevalence of Color Vision Deficiency in Qazvin

    Mohammad khalaj

    2014-01-01

    Full Text Available Background: Color vision deficiency (CVD is an X chromosome-linked recessive autosomal dominant. Determine the prevalence of color blindness in Qazvin population. Materials and Methods: In a cross sectional study color vision deficiency examined in 1853 individuals with age 10-25 years old who participated in private clinics and eye clinic of Bu-Ali hospital in Qazvin in 2010. The screening of color vision deficiency was performed using Ishihara test. Data were analyzed by SPSS-16 with χP2P test with p<0.05. Results: Mean age of participant was 17.86±4.48 years. 59.5% of them were female. 3.49% of the total population had color vision deficiency that 0.93% and 2.56% were female and male respectively. Conclusion: color vision deficiency must be noticed by decision makers in health field for screen planning.

  12. Influence of preparation conditions of hollow silica–nickel composite spheres on their catalytic activity for hydrolytic dehydrogenation of ammonia borane

    Umegaki, Tetsuo, E-mail: umegaki.tetsuo@nihon-u.ac.jp [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Seki, Ayano [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Xu, Qiang [National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Kojima, Yoshiyuki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan)

    2014-03-05

    Highlights: • We study influence of preparation conditions on activity of hollow silica–nickel composite spheres. • The activity for hydrolytic dehydrogenation of NH{sub 3}BH{sub 3} increases with increase of Si+Ni content. • The particle size distribution affects the activity and reducibility of active nickel species. • The amount of PS residue in the hollow spheres decreases by treatment of as-prepared sample in toluene. -- Abstract: In this paper, we investigated influence of preparation conditions of hollow silica–nickel composite spheres on their morphology and catalytic activity for hydrolytic dehydrogenation of ammonia borane. In the preparation method of this study, when silica–nickel composite shells were coated on polystyrene templates by the sol–gel method using L(+)-arginine as the promoter for the reaction to form silica–nickel composite shell, the polystyrene templates were dissolved subsequently, even synchronously, in the same medium to form hollow spheres. The as-prepared silica–nickel composite spheres were characterized by transmission electron microscopy and scanning electron microscopy. The effects of Si+Ni content on the morphology were systematically evaluated. All the as-prepared hollow silica–nickel composite spheres have the similar morphology as identified by SEM and TEM measurement. Homogeneity of the hollow silica–nickel composite spheres increases with the increase in the Si+Ni content as shown by the laser diffraction particle size analysis. The catalytic activities of the hollow silica–nickel composite spheres for hydrolytic dehydrogenation of ammonia borane prepared with different Si+Ni contents were compared. The catalytic activity for the hydrogen evolution in the presence of the hollow spheres increases with the increase of Si+Ni content. The results of FTIR spectra of the hollow silica–nickel composite spheres indicate that a certain amount of residual PS templates exists in hollow silica

  13. Influence of preparation conditions of hollow silica–nickel composite spheres on their catalytic activity for hydrolytic dehydrogenation of ammonia borane

    Highlights: • We study influence of preparation conditions on activity of hollow silica–nickel composite spheres. • The activity for hydrolytic dehydrogenation of NH3BH3 increases with increase of Si+Ni content. • The particle size distribution affects the activity and reducibility of active nickel species. • The amount of PS residue in the hollow spheres decreases by treatment of as-prepared sample in toluene. -- Abstract: In this paper, we investigated influence of preparation conditions of hollow silica–nickel composite spheres on their morphology and catalytic activity for hydrolytic dehydrogenation of ammonia borane. In the preparation method of this study, when silica–nickel composite shells were coated on polystyrene templates by the sol–gel method using L(+)-arginine as the promoter for the reaction to form silica–nickel composite shell, the polystyrene templates were dissolved subsequently, even synchronously, in the same medium to form hollow spheres. The as-prepared silica–nickel composite spheres were characterized by transmission electron microscopy and scanning electron microscopy. The effects of Si+Ni content on the morphology were systematically evaluated. All the as-prepared hollow silica–nickel composite spheres have the similar morphology as identified by SEM and TEM measurement. Homogeneity of the hollow silica–nickel composite spheres increases with the increase in the Si+Ni content as shown by the laser diffraction particle size analysis. The catalytic activities of the hollow silica–nickel composite spheres for hydrolytic dehydrogenation of ammonia borane prepared with different Si+Ni contents were compared. The catalytic activity for the hydrogen evolution in the presence of the hollow spheres increases with the increase of Si+Ni content. The results of FTIR spectra of the hollow silica–nickel composite spheres indicate that a certain amount of residual PS templates exists in hollow silica–nickel composite

  14. Folate deficiency affects histone methylation.

    Garcia, Benjamin A; Luka, Zigmund; Loukachevitch, Lioudmila V; Bhanu, Natarajan V; Wagner, Conrad

    2016-03-01

    that the bound THF serves to protect the FAD class of histone demethylases from the destructive effects of formaldehyde generation by formation of 5,10-methylene-THF. We present pilot data showing that decreased folate in livers as a result of dietary folate deficiency is associated with increased levels of methylated lysine 4 of histone 3. This can be a result of decreased LSD1 activity resulting from the decreased folate available to scavenge the formaldehyde produced at the active site caused by the folate deficiency. Because LSD1 can regulate gene expression this suggests that folate may play a more important role than simply serving as a carrier of one-carbon units and be a factor in other diseases associated with low folate. PMID:26880641

  15. Structure and properties of oxidative dehydrogenation catalysts based on MoO3/Al2O3

    The effects of MoOx structure on propane oxidative dehydrogenation (ODH) rates and selectivity were examined on Al2O3-supported molybdenum oxide catalysts with a wide range of Mo surface density (0.4-12 Mo/nm2). X-ray diffraction and Raman, UV-visible, and X-ray absorption spectroscopies showed that the structure of dispersed molybdena depends strongly on the Mo surface density. Two-dimensional MoOx oligomers formed preferentially for Mo surface densities below 4 Mo/nm2. At higher surface densities, these MoOx oligomers coexist on Al2O3 surfaces with three-dimensional MoO3. UV-visible edge energies decrease with increasing Mo surface density, consistent with the growth of MoOx structures. The evolution of near-edge spectral features in the X-ray absorption spectra and the gradual appearance of a Mo-Mo scattering peak in the radial structure function confirmed the growth of MoOx domains with increasing surface density. ODH rates per Mo atom increased with increasing Mo surface density a nd reached a maximum value for samples with (a) 4.5 Mo/nm2; this behavior reflects an increase in the reactivity of surface Mo species, because all MoOx species are exposed at domain surfaces in this surface density range. As also shown for VOx-based catalysts, turnover rates are higher on two-dimensional domains than on isolated monomers and they increase as the MoOx domain size increases. The rates of reduction of MoOx species in H2 or C3H8 were probed using kinetic and X-ray absorption methods; these reduction rates increased in parallel with ODH rates as the MoOx surface density increased, apparently as a result of the ability of larger domains to delocalize the higher electron density that accompanies the reduction process. As the surface density increased above 4.5 Mo/nm2, ODH rates (per Mo atom) decrease, as a result of the loss of accessibility caused by the formation of MoO3 crystallites. For these latter samples, the ODH rate per BET surface area approached a constant value

  16. Genetics Home Reference: dopamine beta-hydroxylase deficiency

    ... Genetics Home Health Conditions dopamine beta-hydroxylase deficiency dopamine beta-hydroxylase deficiency Enable Javascript to view the ... boxes. Print All Open All Close All Description Dopamine beta (β)-hydroxylase deficiency is a condition that ...

  17. Who Is at Risk for Alpha-1 Antitrypsin Deficiency?

    ... for Alpha-1 Antitrypsin Deficiency? Alpha-1 antitrypsin (AAT) deficiency occurs in all ethnic groups. However, the ... most often in White people of European descent. AAT deficiency is an inherited condition. "Inherited" means the ...

  18. Genetics Home Reference: mannose-binding lectin deficiency

    ... Health Conditions mannose-binding lectin deficiency mannose-binding lectin deficiency Enable Javascript to view the expand/collapse ... PDF Open All Close All Description Mannose-binding lectin deficiency is a condition that affects the immune ...

  19. Genetics Home Reference: iron-refractory iron deficiency anemia

    ... refractory iron deficiency anemia iron-refractory iron deficiency anemia Enable Javascript to view the expand/collapse boxes. ... All Close All Description Iron-refractory iron deficiency anemia is one of many types of anemia , which ...

  20. Genetics Home Reference: ataxia with vitamin E deficiency

    ... Home Health Conditions ataxia with vitamin E deficiency ataxia with vitamin E deficiency Enable Javascript to view ... boxes. Download PDF Open All Close All Description Ataxia with vitamin E deficiency is a disorder that ...

  1. Flu Vaccine Guidance for Patients with Immune Deficiency

    ... Vaccine Guidance for Patients with Immune Deficiency Share | Flu Vaccine Guidance for Patients with Immune Deficiency This ... is the best tool for prevention of the flu, should patients with immune deficiency be given the ...

  2. Synthesis and characterization of TiO2 –SiO2 nanoparticles as catalyst for dehydrogenation of 1,4-dihydropyridines

    F Farzaneh; L Jafarie Fourozune

    2014-02-01

    Nanoparticles of binary TiO2–SiO2 mixed oxides was prepared via sol–gel method using tetraethylorthosilicate (TEOS) and titanium isopropoxide (TIPP) in different reaction conditions (solvent and pH) using ammonium hyhdroxide, acetic acid, sodium hydroxide, ethyleneglycol and polyethylene glycol followed by calcination at 850–970° C. The morphologies, structures and chemical compositions were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transmission infrared spectroscopy (FTIR) techniques. The catalytic activity of the obtained nanomaterials was explored for the dehydrogenation of 1,4-dihydropyridines (1,4-DHPs). Observation of 86–100% conversion and 100% selectivity towards the formation of desired products with prepared nanoparticles will be discussed here.

  3. Effect of ball-milling duration and dehydrogenation on the morphology, microstructure and catalyst dispersion in Ni-catalyzed MgH2 hydrogen storage materials

    The effects of high-energy ball-milling on catalyst morphology and dispersion as a function of milling duration and on hydrogen desorption were investigated. Samples of MgH2 doped with 0.05 Ni catalyst were examined after 1, 5 and 10 h of milling. Longer milling durations produced finer catalyst particle sizes and more uniform dispersions, but yielded higher hydrogen desorption temperatures. This behavior is attributed to the formation of Mg2NiH4 with increased milling times. Electron tomography was used to show that the Ni particles reside both inside and outside the MgH2 particles. On dehydrogenation there was a redistribution of catalyst and continued formation of Mg2Ni. The formation of this phase is proposed to explain the reported degradation of hydrogen capacity and the change in kinetics of this system with cycling

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

    Khan, Faiza B.; Dasireddy, Venkata D. B. C., E-mail: Dasireddy@gmail.com; Bharuth-Ram, K. [University of KwaZulu-Natal, School of Chemistry and Physics (South Africa); Masenda, H. [University of the Witwatersrand, School of Physics (South Africa); Friedrich, H. B. [University of KwaZulu-Natal, School of Chemistry and Physics (South Africa)

    2015-04-15

    A phase specific iron orthophosphate catalyst, FePO{sub 4}, 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 FePO{sub 4}, to i) the tridymite-like phase, ii) the reduced form, iron(II) pyrophosphate and Fe{sub 2}P{sub 2}O{sub 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.

  5. An investigation of the microstructure and hydrogenation/dehydrogenation properties of ball-milled CeMg{sub 12} alloys with Ni powders

    Hu, Feng [Inner Mongolia Univ. of Science and Technology, Baotou (China). The School of Rare Earth; Inner Mongolia Univ. of Science and Technology, Baotou (China). Elected State Key Lab.; Zhang, Yanghuan [Inner Mongolia Univ. of Science and Technology, Baotou (China). Elected State Key Lab.; Central Iron and Steel Research Institute, Beijing (China). Depts. of Functional Material Research; Zhang, Yin; Xu, Jianyi; Cai, Ying [Inner Mongolia Univ. of Science and Technology, Baotou (China). The School of Rare Earth; Deng, Leibo [Inner Mongolia Univ. of Science and Technology, Baotou (China). Elected State Key Lab.

    2014-01-15

    CeMg{sub 12} + 100 wt.% Ni composite hydrogen storage alloys were prepared using ball-milling. The phase structure, morphologies, and hydrogen absorption and desorption kinetics of these alloys were systematically investigated. The results show that the milled CeMg{sub 12} + 100 wt.% Ni alloys consisted of Mg{sub 2}Ni and Ni phase with nanocrystalline and amorphous structures. Additionally, the volume fractions of the phase increased with prolonged ball-milling times, which improved the hydrogenation rates and the hydrogen storage capacities of the alloy samples. However, the dehydrogenation kinetics of the alloy samples were also impaired by the increased milling times. The poor dehydriding kinetics of the alloy samples milled for 80 h and 100 h were primarily attributed to grain size effects. (orig.)

  6. Core-shell structured nanospheres with mesoporous silica shell and Ni core as a stable catalyst for hydrolytic dehydrogenation of ammonia borane

    Hua; Liu; Changyan; Cao; Ping; Li; Yu; Yu; Weiguo; Song

    2014-01-01

    Core-shell structured nanospheres with mesoporous silica shell and Ni core(denoted as Ni@meso-SiO2) are prepared through a three-step process. Monodispersed Ni precursors are first prepared, and then coated with mesoporous SiO2. Final Ni@meso-SiO2spheres are obtained after calcination. The products are characterized by X-ray powder diffraction, transmission electron microscopy and N2adsorption-desorption methods. These spheres have a high surface area and are well dispersed in water, showing a high catalytic activity with a TOF value of 18.5,and outstanding stability in hydrolytic dehydrogenation of ammonia borane at room temperature.

  7. Picomole-Scale Real-Time Photoreaction Screening: Discovery of the Visible-Light-Promoted Dehydrogenation of Tetrahydroquinolines under Ambient Conditions.

    Chen, Suming; Wan, Qiongqiong; Badu-Tawiah, Abraham K

    2016-08-01

    The identification of new photocatalytic pathways expands our knowledge of chemical reactivity and enables new environmentally friendly synthetic applications. However, the development of miniaturized screening procedures/platforms to expedite the discovery of photochemical reactions remains challenging. Herein, we describe a picomole-scale, real-time photoreaction screening platform in which a handheld laser source is coupled with nano-electrospray ionization mass spectrometry. By using this method, we discovered an accelerated dehydrogenation pathway for the conversion of tetrahydroquinolines into the corresponding quinolines. This transformation is readily promoted by an off-the-shelf [Ru(bpy)3 ]Cl2 ⋅6 H2 O complex in air at ambient temperature in direct sunlight, or with the aid of an energy-saving lamp. Moreover, radical cations and trans-dihydride intermediates captured by the screening platform provided direct evidence for the mechanism of the photoredox reaction. PMID:27321152

  8. Studies on the mode of action of sterol carrier protein in the dehydrogenation of 5-cholest-7-en-3 beta-ol

    Sterol carrier protein (SCP) promotes the microsomal dehydrogenation of 5-cholest-7-en-3 beta-ol (lathosterol) to 7-dehydrocholesterol. This promotion occurs whether the substrate is exogenous or preincorporated into microsomes. Similarly, SCP promotes an intermembrane transfer of lathosterol from one microsomal population to another. Here the authors present evidence for an SCP-mediated collisional interaction which results in the intermembrane transfer of sterol substrate and excludes a conventional substrate-carrier mechanism for SCP. Radioactive carboxymethyl SCP is shown to bind to microsomes and to anionic phospholipids but not to phosphatidylcholine. Treatment of microsomes with trypsin, but not with phospholipase A2, reduces SCP binding. Binding studies with small molecules substantiate the identity of SCP with Z-protein

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

    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 Fe2P2O7, 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

  10. Primary Immuno-deficiencies (PID

    Javad Ghaffari1

    2009-01-01

    Full Text Available (Received 6 June, 2009 ; Accepted 22 July, 2009AbstractBackground and purpose: Primary immune-deficiencies (PID are associated with a wide range of clinical disorders along with variable symptoms. The aim of this study was to evaluate and improve our knowledge regarding PID from patients that were referred to Booali Sina Hospital.Materials and methods: We evaluated all of PID`s that were referred to Booali Sina Hospital from their data records. Demography, clinical and laboratory data were recorded and then analyzed.Results: In the duration of 3 years, we had 10 patients with PID (7 males and 3 females. Of these cases, 5 had hum oral (50%, 1case had phagocytic (10%, 3 cases had cellular (30% and 1 case had hyper IgE syndrome (10%. Many of them had respiratory and otitis media infections, while a few patients had adenitis, gastroenteritis, liver abscesses, bleedings and malignancy.Conclusion: PID is a diverse disorder that involves different immune systems. Knowledge from patient’s clinical symptoms and consideration in their differential diagnosis can be helpful in early diagnosis and an effective treatment.J Mazand Univ Med Sci 2009; 19(70: 76-80 (Persian

  11. Cernunnos deficiency: a case report.

    Turul, T; Tezcan, I; Sanal, O

    2011-01-01

    B cell-negative severe combined immunodeficiency (SCID) is caused by molecules involved in the variable (diversity) joining (V[D]J) recombination process. Four genes involved in the nonhomologous end joining pathway--Artemis, DNA-PKcs, DNA ligase 4, and Cernunnos--are involved in B cell-negative radiosensitive SCID. Deficiencies in DNA ligase 4 and the recently described Cernunnos gene result in microcephaly, growth retardation, and typical bird-like facies. Lymphopenia and hypogammaglobulinemia with normal or elevated immunoglobulin (Ig) M levels indicate a defect in V(D)J recombination. We present a case with recurrent postnatal pulmonary infections leading to chronic lung disease, disseminated molluscum contagiosum, lymphopenia, low IgG, IgA and normal IgM levels. Our patient had phenotypic features such as microcephaly and severe growth retardation. Clinical presentation in patients with the B cell-negative subtype ranges from SCID to atypical combined immunodeficiency, occasionally associated with autoimmune manifestations and cytomegalovirus infection. Our patient survived beyond infancy with combined immunodeficiency and no autoimmune manifestations. PMID:21721379

  12. Reticulocyte maturity indices in iron deficiency anemia

    Muriel Wollmann

    2014-01-01

    Full Text Available Objective: The aim of this study was to analyze the reticulocyte maturity indices (low, medium, and high fluorescence ratios in iron deficient 1- to 6-year-old children, and identify the prevalence of iron deficiency anemia in this population. Methods: The present study included 39 subjects, divided into two groups: control subjects (n = 33, and subjects with iron deficiency anemia (n = 6. The results were analyzed by Student's t-test for comparison of means. Differences were considered significant when two-tailed p-value < 0.05. Results: Subjects with iron deficiency anemia presented increases in the proportion of mean (10.3 ± 4.7% vs. 6.0 ± 3.4%; p-value = 0.003, and high fluorescence reticulocytes (2.3 ± 0.87% vs. 0.9 ± 0.9%; p-value = 0.03 compared to the control group. The prevalence of anemia in this population was 15% (n = 6. Conclusion: The indices related to immaturity of reticulocytes are higher in the presence of iron deficiency, thus demonstrating a deficiency in the raw material to form hemoglobin and are, therefore, possible early markers of iron deficiency and anemia. We emphasize the need to standardize these indices for use in clinical practice and lab test results.

  13. Perinatal iron deficiency and neurocognitive development

    Emily Clare Radlowski

    2013-09-01

    Full Text Available Iron deficiency is the most common form of nutrient deficiency worldwide. It is highly prevalent due to the limited availability of high quality food in developing countries, and poor dietary habits in industrialized countries. According to the World Health Organization, it affects nearly 2 billion people and up to 50% of women who are pregnant. Maternal anemia during pregnancy is especially burdensome to healthy neurodevelopment in the fetus because iron is needed for proper neurogenesis, development, and myelination. Maternal anemia also increases the risk of low birth weight, either due to premature birth or fetal growth restriction, which is associated with delayed neurocognitive development and even psychiatric illness. As rapid neurodevelopment continues after birth infants that received sufficient iron in utero, but that receive a low iron diet after 6 months of age, also show deficits in neurocognitive development, including impairments in learning and memory. Unfortunately, the neurocognitive complications of iron deficiency during critical pre- and postnatal periods of brain development are difficult to remedy, persisting into adulthood. Thus, preventing iron deficiency in the pre- and postnatal periods is critical as is devising new means to recapture cognitive function in individuals who experienced early iron deficiency. This review will discuss the prevalence of pre- and postnatal iron deficiency, the mechanism, and effects of iron deficiency on brain and cognitive development.

  14. Corneal proteoglycan changes under vitamin A deficiency

    The vitamin A-deficient keratinized cornea is very susceptible to ulceration possibly due to altered stromal components. In this study the proteoglycans present in the corneal stroma of vitamin A-deficient, pair-fed and normal rabbits were compared. Rabbits after weaning were placed on a vitamin A deficient diet, the same diet with retinyl palmitate added (pair-fed) or normal rabbit chow. After 5 months, the corneas of the vitamin A-deficient animals became keratinized. The corneal components were then labeled by injection of 3H-leucine and Na35SO4 into the anterior chamber of the eyes on 3 successive days. On the 4th day the animals were sacrificed the corneas removed and dissected. The labeled corneal stromas were extracted with 4 M GuHCl and the components separated on a DEAE-Sepharose column. The proteoglycans were eluted with 0.5 M and 1.0 M NaCl. The 1.0 M NaCl fraction (mainly keratin sulfate proteoglycans) was increased 25% in the vitamin A-deficient corneas over that for the pair-fed and normal corneas. These proteoglycans from the deficient corneas gave a different elution pattern on Octyl-Sepharose eluted with a Triton X-100 gradient than those from the pair-fed corneas. The total labeled proteoglycans were similar in the stromas from the 3 types of rabbits. These results indicate the various corneal proteoglycan ratios differ under vitamin A deficiency conditions

  15. SURF1 deficiency: a multi-centre natural history study

    Wedatilake, Y; Brown, R; Mcfarland, R.; Yaplito-Lee, J.; Morris, A.A.; Champion, M; Jardine, P E; Clarke, A.; Thorburn, D R; Taylor, R. W.; Land, J M; Forrest, K.; Dobbie, A.; Simmons, L; Aasheim, E. T.

    2013-01-01

    Background SURF1 deficiency, a monogenic mitochondrial disorder, is the most frequent cause of cytochrome c oxidase (COX) deficient Leigh syndrome (LS). We report the first natural history study of SURF1 deficiency. Methods We conducted a multi-centre case notes review of 44 SURF1-deficient patients from ten different UK centres and two Australian centres. Survival data for LRPPRC-deficient LS and nuclear-encoded complex I-deficient LS patients were obtained from previous publications. The su...

  16. Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2.

    El-Eskandarany, M Sherif

    2016-01-01

    Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation. PMID:27220994

  17. Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4 and Lithium Amide (LiNH2 Hydride Composites

    Leszek Zbroniec

    2012-04-01

    Full Text Available Hydrogen storage properties of the (nLiAlH4 + LiNH2 hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of H2 (up to ~5 wt.% during ball milling up to 100–150 min. The quantity of released H2 rapidly decreases for the molar ratio n = 3 and is not observed for n = 11.5 and 30. The XRD studies indicate that the H2 release is a result of a solid state decomposition of LiAlH4 into (1/3Li3AlH6 + (2/3Al + H2 and subsequently decomposition of (1/3Li3AlH6 into LiH + (1/3Al + 0.5H2. Apparently, LiAlH4 is profoundly destabilized during ball milling by the presence of a large quantity of LiNH2 (37.7 wt.% in the n = 1 composite. The rate of dehydrogenation at 100–170 °C (at 1 bar H2 is adversely affected by insufficient microstructural refinement, as observed for the n = 1 composite, which was milled for only 2 min to avoid H2 discharge during milling. XRD studies show that isothermal dehydrogenation of (nLiAlH4 + LiNH2 occurs by the same LiAlH4 decomposition reactions as those found during ball milling. The ball milled n = 1 composite stored under Ar at 80 °C slowly discharges large quantities of H2 approaching 3.5 wt.% after 8 days of storage.

  18. Oxidative Dehydrogenation of Cyclohexane on Cobalt Oxide (Co3O4) Nanoparticles: The Effect of Particle Size on Activity and Selectivity

    Tyo, Eric C.; Yin, Chunrong; Di Vece, Marcel; Qian, Qiang; Kwon, Gihan; Lee, Sungsik; Lee, Byeongdu; DeBartolo, Janae E.; Seifert, Sönke; Winans, Randall E.; Si, Rui; Ricks, Brian; Goergen, Simone; Rutter, Matthew; Zugic, Branko; Flytzani-Stephanopoulos, Maria; Wang, Zhi Wei; Palmer, Richard E.; Neurock, Matthew; Vajda, Stefan

    2012-10-02

    The oxidative dehydrogenation of cyclohexane by cobalt oxide nanoparticles was studied via temperature programmed reaction combined with in situ grazing incidence X-ray absorption spectroscopy and grazing incidence small-angle X-ray scattering and theoretical calculations on model Co3O4 substrates. Both 6 and 12 nm Co3O4 nanoparticles were made through a surfactant-free preparation and dispersed on an Al2O3 surface formed by atomic layer deposition. Under reaction conditions the nanoparticles retained their oxidation state and did not sinter. They instead underwent an assembly/disassembly process and could reorganize within their assemblies. The selectivity of the catalyst was found to be size- and temperature-dependent, with larger particles preferentially producing cyclohexene at lower temperatures and smaller particles predominantly resulting in benzene at higher temperatures. The mechanistic features thought to control the oxidative dehydrogenation of cyclohexane and other light alkanes on cobalt oxide were established by carrying out density functional theory calculations on the activation of propane, a surrogate model alkane, over model Co3O4 surfaces. The initial activation of the alkane (propane) proceeds via hydrogen abstraction over surface oxygen sites. The subsequent activation of the resulting alkoxide intermediate occurs at a second surface oxygen site to form the alkene (propene) which then desorbs from the surface. Hydroxyl recombination results in the formation of water which desorbs from the surface. Finally, oxygen is necessary to regenerate the surface oxygen sites, catalyze C–H activation steps, and minimize catalyst degradation.

  19. Development of an oxidative dehydrogenation-based fluorescent probe for Cu{sup 2+} and its biological imaging in living cells

    Fan Jiangli, E-mail: fanjl@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, No. 2 Linggong Road, High-tech District, Dalian 116024 (China); Liu Xiaojian; Hu Mingming; Zhu Hao; Song Fengling [State Key Laboratory of Fine Chemicals, Dalian University of Technology, No. 2 Linggong Road, High-tech District, Dalian 116024 (China); Peng Xiaojun, E-mail: pengxj@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, No. 2 Linggong Road, High-tech District, Dalian 116024 (China)

    2012-07-20

    Highlights: Black-Right-Pointing-Pointer The fluorescent probe contains an N, O and S tridentate ligand. Black-Right-Pointing-Pointer The probe is simple but highly sensitive and selective toward Cu{sup 2+}. Black-Right-Pointing-Pointer The mechanism is based on the Cu{sup 2+}-promoted dehydrogenation of amine in different organic and aqueous solutions. Black-Right-Pointing-Pointer It was successfully applied to visualize Cu{sup 2+} in living cells. - Abstract: Based on a boron dipyrromethene (BODIPY) derivative containing an N, O and S tridentate ligand, a Cu{sup 2+} fluorescent probe BTCu was developed. The detection mechanism was verified as Cu{sup 2+}-promoted oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu{sup +}-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{sup 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 Multiplication-Sign 10{sup -8} M and 4.96 Multiplication-Sign 10{sup -8} M in the two different solutions, respectively. And BTCu could work in a wide pH range with an extraordinary low pK{sub 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{sup 2+} changes.

  20. Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2

    El-Eskandarany, M. Sherif

    2016-05-01

    Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation.

  1. SCID patients with ARTEMIS vs RAG deficiencies following HCT: increased risk of late toxicity in ARTEMIS-deficient SCID

    Schuetz, Catharina; Neven, Benedicte; Dvorak, Christopher C.; Leroy, Sandrine; Ege, Markus J.; Pannicke, Ulrich; Schwarz, Klaus; Schulz, Ansgar S.; Hoenig, Manfred; Sparber-Sauer, Monika; Gatz, Susanne A.; Denzer, Christian; Blanche, Stephane; Moshous, Despina; Picard, Capucine

    2014-01-01

    No difference in survival, early toxicity, or occurrence of tumors between ARTEMIS and RAG-deficient SCID.ARTEMIS-deficient patients develop late toxicity following HCT: growth retardation, endocrinologic deficiencies, and dental abnormalities.

  2. C3 Deficiency – A Case Report

    Carreiro-Martins, P; Gaspar, A.; Rosado-Pinto, J.

    2006-01-01

    O sistema do complemento é um componente essencial do sistema imunitário inato, pelo que as deficiências de proteínas da sua complexa cascata podem ter consequências mais ou menos graves, de acordo com a importância do factor afectado. As complicações mais usuais das deficiências do complemento são infecções recorrentes a bactérias encapsuladas e distúrbios autoimunes. Os autores apresentam um caso clínico de deficiência do factor C3, situação extremamente rara, discutindo a fisiopatolo...

  3. Auditory Neuropathy/Dyssynchrony in Biotinidase Deficiency

    Yaghini, Omid

    2016-01-01

    Biotinidase deficiency is a disorder inherited autosomal recessively showing evidence of hearing loss and optic atrophy in addition to seizures, hypotonia, and ataxia. In the present study, a 2-year-old boy with Biotinidase deficiency is presented in which clinical symptoms have been reported with auditory neuropathy/auditory dyssynchrony (AN/AD). In this case, transient-evoked otoacoustic emissions showed bilaterally normal responses representing normal function of outer hair cells. In contrast, acoustic reflex test showed absent reflexes bilaterally, and visual reinforcement audiometry and auditory brainstem responses indicated severe to profound hearing loss in both ears. These results suggest AN/AD in patients with Biotinidase deficiency. PMID:27144235

  4. Severe Vitamin D Deficiency Causing Kyphoscoliosis.

    Singhai, Abhishek; Banzal, Subodh

    2013-01-01

    Vitamin D deficiency is common among Indian population. Women are especially at risk for severe vitamin D deficiency. The risk is higher for those who are multiparous and postmenopausal. Poor exposure to sunlight, higher latitude, winter season, inadequate diet, older age, obesity and malabsorption are also important risk factors. Symptoms of hypovitaminosis D, including diffuse or migratory pain affecting several sites (especially the shoulder, pelvis, ribcage and lower back) have also been misdiagnosed as musculoskeletal disorders, including fibromyalgia, polymyalgia rheumatica and ankylosing spondylitis. Here, we report two cases presented with kyphoscoliosis, diagnosed to have severe vitamin D deficiency. PMID:26664847

  5. Investigation of suspected growth hormone deficiency

    Milner, R. D. G.; Burns, E C

    1982-01-01

    This paper describes views of the Health Services Human Growth Hormone Committee on how a child suspected of growth hormone deficiency should be investigated in a district general hospital or in a regional growth centre.

  6. Genetics Home Reference: glutathione synthetase deficiency

    ... elevated acidity in the blood and tissues (metabolic acidosis). In addition to the features present in moderate ... Kaabachi N, Hachicha M. Hemolytic anemia and metabolic acidosis: think about glutathione synthetase deficiency. Fetal Pediatr Pathol. ...

  7. Genetics Home Reference: phosphoglycerate kinase deficiency

    ... Children Living with Inherited Metabolic Diseases (CLIMB) (UK) Muscular Dystrophy Association National Organization for Rare Disorders (NORD) Resource list from the University of Kansas Medical Center: Metabolic Conditions Genetic Testing Registry (2 links) Deficiency of phosphoglycerate kinase ...

  8. FastStats: Anemia or Iron Deficiency

    ... this? Submit What's this? Submit Button NCHS Home Anemia or Iron Deficiency Recommend on Facebook Tweet Share ... visits Number of visits to emergency departments with anemia as the primary hospital discharge diagnosis: 237,000 ...

  9. Vitamin D Deficiency (Beyond the Basics)

    ... of Use ©2016 UpToDate, Inc. Patient education: Vitamin D deficiency (Beyond the Basics) Author Marc K Drezner, ... topic last updated: Jun 09, 2015. INTRODUCTION — Vitamin D plays an important role in many places throughout ...

  10. Genetics Home Reference: sepiapterin reductase deficiency

    Skip to main content Your Guide to Understanding Genetic Conditions Enable Javascript for addthis links to activate. ... Conditions Genes Chromosomes & mtDNA Resources Help Me Understand Genetics Home Health Conditions sepiapterin reductase deficiency sepiapterin reductase ...

  11. Genetics Home Reference: dopamine transporter deficiency syndrome

    Skip to main content Your Guide to Understanding Genetic Conditions Enable Javascript for addthis links to activate. ... Conditions Genes Chromosomes & mtDNA Resources Help Me Understand Genetics Home Health Conditions dopamine transporter deficiency syndrome dopamine ...

  12. Genetics Home Reference: holocarboxylase synthetase deficiency

    ... the body is unable to use the vitamin biotin effectively. This disorder is classified as a multiple ... impaired activity of certain enzymes that depend on biotin. The signs and symptoms of holocarboxylase synthetase deficiency ...

  13. Genetics Home Reference: familial glucocorticoid deficiency

    ... Clark AJ, Metherell LA. ACTH resistance: genes and mechanisms. Endocr Dev. 2013;24:57-66. doi: 10. ... Metherell LA. Familial glucocorticoid deficiency: New genes and mechanisms. Mol Cell Endocrinol. 2013 May 22;371(1- ...

  14. Genetics Home Reference: mevalonate kinase deficiency

    ... net Patient Support and Advocacy Resources (2 links) Autoinflammatory Alliance National Organization for Rare Disorders (NORD): Hyper ... Haas D, Hoffmann GF. Mevalonate kinase deficiency and autoinflammatory disorders. N Engl J Med. 2007 Jun 28; ...

  15. Genetics Home Reference: glucose phosphate isomerase deficiency

    ... resulting in a shortage of red blood cells ( anemia ). Chronic hemolytic anemia can lead to unusually pale skin (pallor), yellowing ... ducts (gallstones) may also occur in this disorder. Hemolytic anemia in GPI deficiency can range from mild to ...

  16. Somatomedin C deficiency in Asian sisters.

    McGraw, M E; Price, D A; D. J. Hill

    1986-01-01

    Two sisters of Asian origin showed typical clinical and biochemical features of primary somatomedin C (SM-C) deficiency (Laron dwarfism). Abnormalities of SM-C binding proteins were observed, one sister lacking the high molecular weight (150 Kd) protein.

  17. Genetics Home Reference: deoxyguanosine kinase deficiency

    ... or mtDNA, which is essential for the normal function of these structures. Deoxyguanosine kinase is involved in producing and maintaining the ... DNA (known as mitochondrial DNA depletion) impairs mitochondrial function ... deficiency . Learn more about the gene associated ...

  18. Antibody deficiency in Rubinstein-Taybi syndrome.

    Herriot, R; Miedzybrodzka, Z

    2016-03-01

    The developmental disorder Rubinstein-Taybi syndrome (RTS) is frequently complicated by recurrent respiratory infections. In many cases this is likely to be the result of microaspiration or gastro-oesophageal reflux but, in a proportion, underlying antibody deficiency is a potentially modifiable susceptibility factor for infection. Relatively subtle, specific defects of pneumococcal antibody production have previously been described in the context of RTS. Here, we report a rare association between the syndrome and an overt, major primary antibody deficiency disorder (common variable immune deficiency) which was successfully managed with immunoglobulin replacement therapy. Early recognition and investigation for antibody deficiency associated with RTS allied to effective and optimized treatment are essential to minimize morbidity and mortality and improve quality and duration of life. PMID:26307339

  19. Growth hormone deficiency and hyperthermia during exercise

    Juul, A; Hjortskov, N; Jepsen, Leif;

    1995-01-01

    -deficiency may be at risk for developing hyperthermia. To pursue this, we performed a controlled study on sweating and body temperature regulation during exercise in the heat in 16 GH-treated GH-deficient patients with normalized insulin-like growth factor-I and insulin-like growth factor/binding protein-3 serum...... levels [11 with multiple pituitary deficiency (MPD) and 5 with isolated GH deficiency] and in 10 healthy subjects as controls (CTs). Each subject exercised on a bicycle ergometer for 60 min at a workload corresponding to 45% of their individual maximal oxygen consumption (VO2max), in a room maintained at...... 35 C. GH serum concentrations increased significantly after approximately 10 min of exercise in the CTs (P <0.001) but remained low in the patients. Body heat storage was significantly higher in the patients compared with the CTs [89 (SE +/- 10) watts (MPD) vs. 37 (SE +/- 8) watts (CTs), P <0...

  20. Genetics Home Reference: GLUT1 deficiency syndrome

    ... genetic conditions treated or managed? What is genetic testing? How can I find a genetics professional in my area? Other Names for This Condition De Vivo disease encephalopathy due to GLUT1 deficiency G1D glucose ...