Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts

Science.gov (United States)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu

2017-02-01

Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H2) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H2 evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu2MoS4 nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu2MoS4nanosheets. These layered Cu2MoS4 nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H2 production by water splitting. We have obtained superior H2 production rates by using Cu2MoS4 loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Hydrotreatment of heavy oil from coal liquefaction on Sulfide Ni - W Catalysts

International Nuclear Information System (INIS)

Zhi-ping Lei; Li-juan Gao; Heng-fu Shui; Shi-biao, Ren; Zhi-cai Wang; Kang-shi Gang

2011-01-01

Heavy oil (distillation temperature: 320-340 deg C) derived from the direct coal liquefaction process using Shengli coal were hydrotreated using sulfided Ni-Mo/Al 2 O 3 , Ni-W/Al 2 O 3 , and Ni-W/SiO 2 catalysts respectively. The sulfided catalysts were characterized by BET, XRD, H 2 -TPR and NH 3 -TPD respectively. The evaluations of the hydrodenitrogenation (HDN) and hydrodearomatization (HDA) properties of heavy oil on the three catalysts were carried out at 400 deg C and 5.0 MPa initial H2 pressure. The W-based catalysts displayed better performances than Mo-based catalysts for the HDN and HDA reactions. Al 2 O 3 supported catalysts were found to have higher catalytic activities than on SiO 2 supported ones. The activities of sulfided catalysts were associated mainly with the nature of active sites, acidity, metal sulfide crystallite size and the amount of the reducible sulfur species of metal sulfide. (author)

Evidence of molybdenum association with particulate organic matter under sulfidic conditions

DEFF Research Database (Denmark)

Dahl, Tais Wittchen; Chappaz, A.; Hoek, Joost

2017-01-01

, consisting of mainly Mo(IV)-sulfide compounds with molecular structures similar to Mo enzymes and to those found in natural euxinic sediments. Therefore, we propose that Mo removal in natural sulfidic waters can proceed via a non-Fe-assisted pathway that requires particulate organic matter (dead or living......The geochemical behavior of molybdenum (Mo) in the oceans is closely linked to the presence of sulfide species in anoxic environments, where Fe availability may play a key role in the Mo scavenging. Here, we show that Mo(VI) is reduced in the presence of particulate organic matter (represented...

Design of hydroprocessing catalyst for the production of ultra clean fuels. Super clean nenryo wo mezashita jushitsu tanka suiso seisei shokubai no kokinoka

Energy Technology Data Exchange (ETDEWEB)

Shimada, Hiromichi (National Chemical Lab. for Industry,Tsukuba, (Japan))

1990-02-01

In order to develop high function catalyst for the ultra clean fuel refining and other purposes, the catalyst was studied in correlation between the function and structure. Hydrogenation power of aromatic ring and hydrogenolysis power of carbon-carbon bonding, which are principal functions of catalyst in the hydrogenation refining, were evaluated with model material. 30 kinds of catalyst were figure shown in classification result of evaluation. As for the mutual operation of molybdenum and carrier, it is necessary for molybdenum sulfide to be highly dispersed on carrier in order to heighten the hydrogenation activity. While the hydrogenolysis activity, as necessitating electrically negative molybdenum type to be formed on carrier, is manifested by the formation of Bronsted acidity point with hydrogen sulfide, adhering thereto. As for the molybdenum sulfide catalyst, mainly hydrogenation activity point, in case that structure, similar to molybdenum disulfide, is dispersed as a single layer on carrier, and hydrogenolysis activity point, in case that it forms a multi-layer structure thereon, are formed in edge part of respective crystal. The lowering in activity under a long time sevre condition, which mainly are carbonic material deposition, matallic adhesion, etc., is also influenced by the structural change in catalyst. 10 refs., 5 figs. 2 tabs.

Molybdenum-containing acidic catalysts to convert cellulosic biomass to glycolic acid

KAUST Repository

Han, Yu

2014-09-30

Embodiments of the present invention include methods and compositions related to catabolic conversion of cellulosic biomass to glycolic acid using molybdenum-containing acidic catalysts. The invention includes the use of heteropoly and isopoly acids and salts as the molybdenum-containing multi-functional catalysts for biomass conversion. In embodiments of the invention, the reactions employ successive hydrolysis, retro-aldol fragmentation, and selective oxidation in a noble metal-free system.

Hydrotreatment of heavy oil from coal liquefaction on Sulfide Ni - W Catalysts

Energy Technology Data Exchange (ETDEWEB)

Zhi-ping Lei; Li-juan Gao; Heng-fu Shui; Shi-biao, Ren; Zhi-cai Wang; Kang-shi Gang, E-mail: shhf@ahut.edu.c [Anhui University of Technology, Maanshan (China). School of Chemistry and Chemical Engineering. Anhui Key Lab. of Coal Clean Conversion and Utilization

2011-07-01

Heavy oil (distillation temperature: 320-340 deg C) derived from the direct coal liquefaction process using Shengli coal were hydrotreated using sulfided Ni-Mo/Al{sub 2}O{sub 3}, Ni-W/Al{sub 2}O{sub 3}, and Ni-W/SiO{sub 2} catalysts respectively. The sulfided catalysts were characterized by BET, XRD, H{sub 2}-TPR and NH{sub 3}-TPD respectively. The evaluations of the hydrodenitrogenation (HDN) and hydrodearomatization (HDA) properties of heavy oil on the three catalysts were carried out at 400 deg C and 5.0 MPa initial H2 pressure. The W-based catalysts displayed better performances than Mo-based catalysts for the HDN and HDA reactions. Al{sub 2}O{sub 3} supported catalysts were found to have higher catalytic activities than on SiO{sub 2} supported ones. The activities of sulfided catalysts were associated mainly with the nature of active sites, acidity, metal sulfide crystallite size and the amount of the reducible sulfur species of metal sulfide. (author)

Coupling of Alcohols over Alkali-Promoted Cobalt-Molybdenum Sulfide

DEFF Research Database (Denmark)

Christensen, Jakob Munkholt; Jensen, Peter Arendt; Schiødt, N.C.

2010-01-01

Double or nothing: Higher alcohols are produced by the hydrogenation of CO with a K-promoted Co-MoS2/C catalyst. Ethanol, which is passed over the sulfide catalyst along with CO and H2, is mainly converted into 1-butanol, which indicates that alcohol condensation contributes to the build-up of hi...

{gamma} alumina- and HY zeolite-supported molybdenum catalysts: characterisation of the oxidic and sulfided phases; Catalyseurs a base de molybdene supporte sur alumine {gamma} et zeolithe HY: caracterisation des phases oxydes et sulfures

Energy Technology Data Exchange (ETDEWEB)

Plazenet, G

2001-10-01

Oxidic precursors of hydro-treatment catalysts (Co)Mo/alumina or zeolite were characterised by Raman spectroscopy, NMR and EXAFS at the Mo and Co K-edges. The formation of an Anderson-type alumino-molybdate compound upon impregnation of the support with an ammonium hepta-molybdate solution was confirmed for alumina, and also observed for the HY zeolitic support, with consumption of the amorphous alumina of the zeolite. In absence of the latter, ammonium hepta-molybdate precipitates. The species are conserved upon drying; upon calcination, the alumino-molybdate evolves into a surface aluminium molybdate type phase, whereas the hepta-molybdate transforms into MoO{sub 3}. The species formed upon impregnation are located in the inter-granular porosity whereas MoO{sub 3} vapor-condensation leads to formation of dimers located inside the zeolitic structure. The study of the cobalt-promoted precursors showed that the evolution of the molybdenum is the same in the case of co-impregnation preparation. Impregnation with cobalt-molybdate prevents the formation of the alumino-molybdate anion and thus enables the preservation of the Mo-Co interaction but, whatever the precursor, the leveling effect of the calcination-re-hydration steps was demonstrated. An EXAFS study at different sulfur coverages of the MoS{sub 2} platelets in the alumina-supported sulfided catalysts showed the limitations of EXAFS for size determination of MoS{sub 2} crystallites, a parameter that can be reached by AWAXS, which also conveys information about sheet-stacking. The EXAFS study of sulfided (Co)Mo/HY systems revealed incomplete sulfidation of the samples and the very high dispersion of the active phase. The absence of an observable Mo-Co interaction whatever the preparation of the promoted catalysts is consistent with the absence of promoting effect in toluene hydrogenation. (author)

Principal component analysis of NEXAFS spectra for molybdenum speciation in hydrotreating catalysts

International Nuclear Information System (INIS)

Faro Junior, Arnaldo da C.; Rodrigues, Victor de O.; Eon, Jean-G.; Rocha, Angela S.

2010-01-01

Bulk and supported molybdenum based catalysts, modified by nickel, phosphorous or tungsten were studied by NEXAFS spectroscopy at the Mo L III and L II edges. The techniques of principal component analysis (PCA) together with a linear combination analysis (LCA) allowed the detection and quantification of molybdenum atoms in two different coordination states in the oxide form of the catalysts, namely tetrahedral and octahedral coordination. (author)

New sulfide catalysts for the hydroliquefaction of coal

NARCIS (Netherlands)

Vissers, J.P.R.; Oers, van E.M.; Beer, de V.H.J.; Prins, R.

1987-01-01

Possibilities for the preparation of new metal sulfide catalyst systems based on carbon carriers having favourable textural and surface properties have been explored, and attention has been given to the characterization (structure) and evaluation (hydrosulfurization activity) of these catalysts. Two

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Final technical progress report, September 12, 1991--December 11, 1994

Energy Technology Data Exchange (ETDEWEB)

Klier, K.; Herman, R.G.; Deemer, M.; Richards-Babb, M.; Carr, T.

1995-07-01

The objective of this research was to investigate sulfur-resistant catalysts for the conversion of synthesis gas having H{sub 2}/CO {le} 1 into C{sub 1}--C{sub 4} alcohols, especially ethanol, by a highly selective and efficient pathway, while also promoting the water gas shift reaction (WGSR). The catalysts chosen are bifunctional, base-hydrogenation, sulfur-tolerant transition metal sulfides with heavy alkali, e.g. Cs{sup +}, promoter dispersed on their surfaces. The modes of activation of H{sub 2} and CO on MoS{sub 2} and alkali-doped MoS{sub 2} were considered, and computational analyses of the thermodynamic stability of transition metal sulfides and of the electronic structure of these sulfide catalysts were carried out. In the preparation of the cesium-promoted MoS{sub 2} catalysts, a variety of preparation methods using CsOOCH were examined. In all cases, doping with CsOOCH led to a lost of surface area. The undoped molybdenum disulfide catalyst only produced hydrocarbons. Cs-doped MoS{sub 2} catalysts all produced linear alcohols, along with smaller amounts of hydrocarbons. With a 20 wt% CsOOCH/MoS{sub 2} catalyst, temperature, pressure, and flow rate dependences of the synthesis reactions were investigated in the presence and absence of H{sub 2}S in the H{sub 2}/CO = 1/1 synthesis gas during short term testing experiments. It was shown that with a carefully prepared 10 wt% CsOOCH/MoS{sub 2} catalyst, reproducible and high alcohol synthesis activity could be obtained. For example, at 295 C with H{sub 2}/CO = 1 synthesis gas at 8.3 MPa and with GHSV = 7,760 l/kg cat/hr, the total alcohol space time yield was ca 300 g/kg cat/hr (accompanied with a hydrocarbon space time yield of ca 60 g/kg cat/hr). Over a testing period of ca 130 hr, no net deactivation of the catalyst was observed. 90 refs., 82 figs., 14 tabs.

The structure of well defined SiO2 supported MoO3 clusters during sulfidation : an in situ EXAFS-study

NARCIS (Netherlands)

Boer, de M.; Dillen, van A.J.; Koningsberger, D.C.; Geus, J.W.; Kuroda, H.; Ohta, T.

1993-01-01

The sulfidation of a well defined MoO3/SiO2 catalyst has been examd. by means of TPS, EXAFS, and TEM. The oxidic clusters in a 5.6 wt% MoO3/SiO2 catalyst are transformed into almost completely sulfided particles (MoOxSy) by O-S exchange at RT. A molybdenum-sulfido particle that resembles the MoS3

Carbon a support for sulfide catalysts

NARCIS (Netherlands)

Vissers, J.P.R.; Lensing, T.J.; Mercx, F.P.M.; Beer, de V.H.J.; Prins, R.

1983-01-01

Two types of carbon materials, carbon black composite and carbon covered alumina, were studied for-their use as support for sulfide catalysts. The following parameters were varied: type of carbon black, carbon coverage of the alumina and carbon pretreatment. Pore size distributions were determined

Surface science models of CoMoS hydrodesulfurisation catalysts

Energy Technology Data Exchange (ETDEWEB)

De Jong, A.M.; De Beer, V.H.J.; Van Veen, J.A.R.; Niemantsverdriet, J.W. [Schuit Institute of Catalysis, Eindhoven University of Technology, Eindhoven (Netherlands)

1997-07-01

Characterization of supported catalysts with surface spectroscopic techniques is often limited due to restraints imposed by the support material. The use of flat conducting substrates as a model support offers a way to apply these techniques to their full potential. Such surface science models of silica and alumina supported CoMoS catalysts have been made by impregnating thin SiO{sub 2} and Al{sub 2}O{sub 3} films with a solution of nitrilotriacetic acid (NTA) complexes of cobalt and molybdenum. X-ray Photoelectron Spectroscopy (XPS) spectra indicate that the order in which cobalt and molybdenum transfer to the sulfided state is reversed with respect to oxidic Co and Mo systems prepared by conventional methods, implying that NTA complexation retards the sulfidation of cobalt to temperatures where MoS{sub 2} is already formed. Catalytic tests show that the CoMoS model catalysts exhibit activities for thiophene desulfurisation and product distributions similar to those of their high surface area counterparts. 25 refs.

Structure-performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

NARCIS (Netherlands)

Stellwagen, D.R.; Bitter, J.H.

2015-01-01

This work demonstrates for the first time that carbide particle size is a critical factor for the activity and stability of carbon supported tungsten- and molybdenum carbide catalysts in (hydro-)deoxygenation reactions. The stability of the catalyst was shown to increase for larger particles due to

An XPS [x-ray photoelectron spectroscopy] study of the sulfidation-regeneration cycle of a hydroprocessing catalyst

Energy Technology Data Exchange (ETDEWEB)

Shang, D.Y.; Adnot, A.; Kaliaguine, S. (Laval Univ., Ste-Foy, PQ (Canada)); Chmielowiec, J. (Petro Canada Products Co., Mississauga, ON (Canada))

1993-10-01

The formation of sulfates in an industrial Ni-W hydroprocessing (HP) catalyst was investigated by x-ray photoelectron spectroscopy (XPS). A small fluidized bed test unit with on-line sampling device was constructed to simulate industrial sulfidation and oxyregeneration processes of HP catalysts. The results obtained show that the sulfates observed on the surface of sulfided catalysts are not formed during the sulfidation process. Two oxidation processes seem to be responsible for the formation of sulfates: one happens when the catalyst is exposed to air before it is properly cooled and the other is a slow conversion at ambient temperature. The two different processes might be associated to different sulfidic species formed during the sulfidation processes, with the sulfides in the bulk of catalyst particles being more easily oxidized than the ones on the external surface of the catalyst particles. The sulfate formed during the air oxidation of sulfided catalysts, as well as that after oxyregeneration, is not aluminum sulfate but nickel sulfate in both cases. XPS results also indicate that oxygenates in the feedstock are not directly involved in the sulfate formation. 18 refs., 9 figs., 6 tabs.

Catalytic activity of oxide cerium-molybdenum-tellurium catalysts in oxidation ammonolysis

International Nuclear Information System (INIS)

Dzhordano, N.; Bart, D.; Madzhori, R.

1984-01-01

A commercial catalyst containing a mixture of Ce-, Mo-, Te oxides deposited on SiO 2 is shown to manifest a high efficiency in oxidative ammonolysis of propylene (C 3 - ) to acrylonitrile (AN). The dependence of the catalytic properties on the catalyst composition and reaction conditions is studied. It is established that three-component mixtures are more active and selective than the systems with a lesser number of components. Using the catalyst with the optimum ratio of constituent oxides in a microreactor at 440 deg enabled one to achieve initial selectivity in terms of AN equal to 82.5% at 97% conversion of C 3 - . Acrolein, acetonitrile, HCN and nitrogen oxides are the reaction by-products. A supposition is made that the reaction proceeds via the formation of π-compleXes on the centres of Te(4). Setective oxidation occurs on oxygen atoms bonded with the Mo(6) ions. Tellurium enhances the molybdenum reducibleness due to delocalization of electrons, whereas the cerium addition to the mixture of tellurium- and molybdenum oxides increases the rate of molybdenum reoxidation and thus enhances the catalytic system stability

Characterization and performances of cobalt-tungsten and molybdenum-tungsten carbides as anode catalyst for PEFC

International Nuclear Information System (INIS)

Izhar, Shamsul; Yoshida, Michiko; Nagai, Masatoshi

2009-01-01

The preparation of carbon-supported cobalt-tungsten and molybdenum-tungsten carbides and their activity as an anode catalyst for a polymer electrolyte fuel cell were investigated. The electrocatalytic activity for the hydrogen oxidation reaction over the catalysts was evaluated using a single-stack fuel cell and a rotating disk electrode. The characterization of the catalysts was performed by XRD, temperature-programmed carburization, temperature-programmed reduction and X-ray photoelectron spectroscopy. The maximum power densities of the 30 wt% 873 K-carburized cobalt-tungsten and molybdenum-tungsten mixed with Ketjen carbon (cobalt-tungsten carbide (CoWC)/Ketjen black (KB) and molybdenum-tungsten carbide (MoWC)/KB) were 15.7 and 12.0 mW cm -2 , respectively, which were 14 and 11%, compared to the in-house membrane electrode assembly (MEA) prepared from a 20 wt% Pt/C catalyst. The CoWC/KB catalyst exhibited the highest maximum power density compared to the MoWC/KB and WC/KB catalysts. The 873 K-carburized CoW/KB catalyst formed the oxycarbided and/or carbided CoW that are responsible for the excellent hydrogen oxygen reaction

Hydroprocessing with self-promoted molybdenum and tungsten sulfide catalyst

International Nuclear Information System (INIS)

Mc Candish, L.E.; Ho, T.C.

1987-01-01

A hydroprocessing process is described comprising contacting a hydrocarbon feed at elevated temperature of at least about 100 0 C and in the presence of hydrogen with a supported, self-promoted catalyst obtained by compositioning one or more catalyst precursors of the formula (ML) (Mo/sub y/W/sub 1-y/O/sub 4/) with an inorganic refractory oxide support and heating the composition in a non-oxidizing atmosphere in the presence of sulfur at elevated temperature for a time sufficient to form the catalyst. M comprises one or more divalent promoter metals, y is any value ranging from 0 to 1, and wherein L is one or more, neutral, nitrogen-containing ligands at least one of which is a chelating polydentate ligand. The contacting occurs for a time sufficient to convert at least a portion of the feed

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu{sub 2}MoS{sub 4}) nanosheets as co-catalysts

Energy Technology Data Exchange (ETDEWEB)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu, E-mail: tkkim@pusan.ac.kr

2017-02-28

Highlights: • Developed Cu{sub 2}MoS{sub 4} nanosheets as co-catalysts. • Cu{sub 2}MoS{sub 4} as active replacements for precious noble metal. • Controlled charge recombination for use in photocatalytic H{sub 2} evolution. • Obtained superior rate of H{sub 2} production by using Cu{sub 2}MoS{sub 4} loaded CdS nanorods. - Abstract: Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H{sub 2}) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu{sub 2}MoS{sub 4}) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H{sub 2} evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu{sub 2}MoS{sub 4} nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu{sub 2}MoS{sub 4}nanosheets. These layered Cu{sub 2}MoS{sub 4} nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H{sub 2} production by water splitting. We have obtained superior H{sub 2} production rates by using Cu{sub 2}MoS{sub 4} loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device.

Science.gov (United States)

Fremerey, Peter; Jess, Andreas; Moos, Ralf

2015-10-23

In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was electrically contacted and its electrical response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H₂S. This catalyst had a very low conductivity in the reduced state. During sulfidation, the conductivity of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This conductivity increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a volume increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quantitatively estimated by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions.

Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device

Directory of Open Access Journals (Sweden)

Peter Fremerey

2015-10-01

Full Text Available In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was electrically contacted and its electrical response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H2S. This catalyst had a very low conductivity in the reduced state. During sulfidation, the conductivity of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This conductivity increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a volume increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quantitatively estimated by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions.

Molybdenum-containing acidic catalysts to convert cellulosic biomass to glycolic acid

KAUST Repository

Han, Yu; Zhang, Jizhe; Liu, Xin

2014-01-01

Embodiments of the present invention include methods and compositions related to catabolic conversion of cellulosic biomass to glycolic acid using molybdenum-containing acidic catalysts. The invention includes the use of heteropoly and isopoly acids

Study of heterogeneous catalytic processes over cobalt, molybdenum and cobalt-molybdenum catalysts supported on alumina by temperature-programmed desorption and temperature-programmed reaction. 1. Adsorption of hydrozen

International Nuclear Information System (INIS)

Rozanov, V.V.; Tsao Yamin; Krylov, O.V.

1996-01-01

Hydrogen adsorption on reduced, sulphidized and reoxidized specimens of molybdenum-and cobalt-molybdenum-containing catalysts applied on aluminium oxide has been studied by the method of thermal desorption (TD). Comparison of TD spectra of hydrogen and data of X-ray phase analysis of the specimens and mass-spectrometric analysis of the products desorbed from the surface of catalysts after their successive reduction sulphidizing, carbonizing and reoxidation permitted a correlation between various forms of hydrogen adsorption and certain centres on the surface of the catalysts. 12 refs., 2 figs

High-Sulfur-Vacancy Amorphous Molybdenum Sulfide as a High Current Electrocatalyst in Hydrogen Evolution

KAUST Repository

Lu, Ang-Yu

2016-08-31

The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.

Molybdenum extraction from copper-molybdenum ores

International Nuclear Information System (INIS)

Nevaeva, L.M.

1982-01-01

Molybdenum extraction from copper-molybdenum ores as practised in different countries is reviewed. In world practice the production process including depression of copper and iron sulfides and flotation of molybdenite is widely spread. At two USA factories the process of a selective flotation with molybdenite depression by dextrin is used

Iridium Sulfide and Ir Promoted Mo Based Catalysts.

Czech Academy of Sciences Publication Activity Database

Vít, Zdeněk

2007-01-01

Roč. 322, - (2007), s. 142-151 ISSN 0926-860X R&D Projects: GA ČR(CZ) GA104/06/0870 Institutional research plan: CEZ:AV0Z40720504 Keywords : iridium sulfide * IrMo catalyst * hydrodesulfurization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2007

Catalytic hydrotreating of lignin with water-soluble molybdenum catalyst

Energy Technology Data Exchange (ETDEWEB)

Osmaa, A.; Johansson, A. (Technical Research Centre of Finland, Espoo (Finland). Lab. of Fuel and Process Technology)

High yields (61% of the original lignin) of low molecular weight oil (84% of the oil eluted through GC) have been obtained by hydrotreating kraft pine lignin with a water-soluble molybdenum catalyst at 430[degree]C for 60 min. The main compounds in the product oil were phenols (8.7% of the original lignin), cyclohexanes (5.0%), benzenes (3.8%), naphthalenes (4.0%), and phenanthrenes (1.2%). The degree of hydrodeoxygenation was 98%. The quality (measured by GPC and GC) of the product was as good as when using more expensive solid NiMo-CR[sub 2]O[sub 3] catalysts. 30 refs., 6 tabs.

The role of Ni in sulfided carbon-supported Ni-Mo hydrodesulfurization catalysts

NARCIS (Netherlands)

Bouwens, S.M.A.M.; Barthe-Zahir, N.; Beer, de V.H.J.; Prins, R.

1991-01-01

The thiophene hydrodesulfurization activities of Ni and Ni---Mo sulfide catalysts supported on activated carbon were measured at atmospheric pressure and the catalyst structures were studied by means of X-ray photoelectron spectroscopy, dynamic oxygen chemisorption, and chemical sulfur analysis. The

Flame spray synthesis of CoMo/Al2O3 hydrotreating catalysts

DEFF Research Database (Denmark)

Høj, Martin; Linde, Kasper; Hansen, Thomas Klint

2011-01-01

containing 16wt.% Mo (atomic ratio Co/Mo=1/3), which did not contain crystalline MoO3 and only small amounts of CoAl2O4. The hydrotreating activity was approximately 75% of that of commercial cobalt molybdenum catalysts prepared by wet impregnation of pre-shaped alumina extrudates. Since the commercial...... obtained consisted mostly of γ-Al2O3 with some CoAl2O4, as evidenced by X-ray diffraction (XRD) and UV–vis spectroscopy. Bulk MoO3 was not detected by XRD, except at the highest molybdenum content (32wt.%) and in the unsupported sample, indicating that molybdenum is well dispersed on the surface.......After activation by sulfidation the activity of the catalysts were measured for the three hydrotreating reactions hydrodesulfurization, hydrodenitrogenation and hydrogenation using a model oil containing dibenzothiophene, indole and naphthalene in n-heptane solution. The best catalyst was the FSP-produced material...

Well-Defined Silica Grafted Molybdenum Bis(imido) Catalysts for Imine Metathesis Reactions

KAUST Repository

Barman, Samir

2017-04-06

Novel site-isolated tetracoordinated molybdenum complexes possessing bis(imido) ligands, [(≡Si–O)2Mo(═NR)2] (R = t-Bu, 2,6-C6H3-i-Pr2), were immobilized on partially dehydroxylated silica (SiO2-200) by a rigorous surface organometallic chemistry protocol. The newly developed materials adorned with bis(imido) functional units, which were previously exploited mainly as spectator ligands on silica-supported olefin metathesis molybdenum catalysts, are found to be efficient heterogeneous catalytic systems for imine cross metathesis under mild conditions.

Well-Defined Silica Grafted Molybdenum Bis(imido) Catalysts for Imine Metathesis Reactions

KAUST Repository

Barman, Samir; Merle, Nicolas; Minenkov, Yury; De Mallmann, Aimery; Samantaray, Manoja; Le Qué mé ner, Fré dé ric; Szeto, Kai C.; Abou-Hamad, Edy; Cavallo, Luigi; Taoufik, Mostafa; Basset, Jean-Marie

2017-01-01

Novel site-isolated tetracoordinated molybdenum complexes possessing bis(imido) ligands, [(≡Si–O)2Mo(═NR)2] (R = t-Bu, 2,6-C6H3-i-Pr2), were immobilized on partially dehydroxylated silica (SiO2-200) by a rigorous surface organometallic chemistry protocol. The newly developed materials adorned with bis(imido) functional units, which were previously exploited mainly as spectator ligands on silica-supported olefin metathesis molybdenum catalysts, are found to be efficient heterogeneous catalytic systems for imine cross metathesis under mild conditions.

Recovery of molybdenum and cobalt powders from spent hydrogenation catalyst

International Nuclear Information System (INIS)

Rabah, M.A.; Hewaidy, I.F.; Farghaly, F.E.

1996-01-01

Free powders as well as compact shapes of molybdenum and cobalt have been successfully recovered from spent hydrogenation and desulphurization catalysts. A process flow sheet was followed involving crushing, milling, particle sizing, hydrometallurgical acid leaching roasting of the obtained salts in an atmospheric oxygen to obtain the respective oxides. These were reduced by hydrogen gas at 110 degree C and 900 degree C respectively. Parameters affecting the properties of the products and the recovery efficiency value such as acid concentration, particle diameter of the solid catalyst, temperature time under a constant mass flow rate the hydrogen gas, have been investigated. A mixture of concentration.sulphuric and nitric acids (3:1 by volume) achieved adequate recovery of both metals. The latter increased with the increase in acid concentration, time up 10 3 hours and temperature: 100 degree C and with the decrease in particle diameter of the spent catalyst. The PH of the obtained filtrate was adjusted to 2 with ammonia to precipitate insoluble ammonium molybdate and a solution of cobalt sulphate. Cobalt hydroxide can be precipitate from the latter solution at a PH = 7.6 using excess ammonium hydroxide solution. The obtained results showed that the metallic products are technically pure meeting the standard specifications. Compact shapes of molybdenum acquire density values increasing with the increase of the pressing load whereby a maximum density value of 2280 kg/m 3 is attained at 0.75 MPa. Maximum recovery efficiency amounts to 96%. 10 figs., 3 tabs

Preparation of Mo/Al2O3 Sulfide Catalysts Modified by Ir Nanoparticles

Czech Academy of Sciences Publication Activity Database

Cinibulk, Josef; Vít, Zdeněk

2002-01-01

Roč. 143, - (2002), s. 443-451 ISSN 0167-2991. [International Symposium Scientific Bases for the Preparation of Heterogeneous Catalysts /8./. Louvain-la-Neuve, 09.09.2002-12.09.2002] R&D Projects: GA AV ČR IAA4072103 Keywords : catalysts modified * sulfide catalysts * Mo/Al2O3 Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.468, year: 2002

Selective recovery of molybdenum from spent HDS catalyst using oxidative soda ash leach/carbon adsorption method

International Nuclear Information System (INIS)

Park, Kyung Ho; Mohapatra, D.; Reddy, B. Ramachandra

2006-01-01

The petroleum refining industry makes extensive use of hydroprocessing catalysts. These catalysts contain environmentally critical and economically valuable metals such as Mo, V, Ni and Co. In the present study, a simple hydrometallurgical processing of spent hydrodesulphurization (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixture was investigated. Recovery of molybdenum was largely dependent on the concentrations of Na 2 CO 3 and H 2 O 2 in the reaction medium, which in turn controls the pH of leach liquor and the presence of Al and Ni as impurities. Under the optimum leaching conditions (40 g L -1 Na 2 CO 3 , 6 vol.% H 2 O 2 , room temperature, 1 h) about 85% recovery of Mo was achieved. The leach liquor was processed by the carbon adsorption method, which selectively adsorbs Mo at pH around 0.75. Desorption of Mo was selective at 15 vol.% NH 4 OH. With a single stage contact, it was found possible to achieve >99%, adsorption and desorption efficiency. Using this method, recovery of molybdenum as MoO 3 product of 99.4% purity was achieved

Transition metal sulfide promoted molybdenum or tungsten sulfide catalysts and their uses for hydroprocessing

International Nuclear Information System (INIS)

Jacobson, A.J.; Chianelli, R.R.; Pecoraro, T.A.

1987-01-01

A process is described for hydrorefining a hydrocarbon feed which comprises contacting the feed at a temperature of at least about 150 0 C and in the presence of hydrogen with a catalyst obtained by heating one or more precursor salts at elevated temperature of at least about 150 0 C, in the presence of sulfur or one or more sulfur-bearing compounds and under oxygen-free conditions for a time sufficient to form the catalyst. The precursor salt contains a tetrathiometallate anion of Mo, W or mixture thereof and a cation comprising one or more divalent promoter metals which are chelated by at least one neutral, nitrogen-containing polydentate ligand. The divalent promoter metal is selected from the group consisting of Ni, Co, Zn, Cu and mixture thereof. The contacting occurs for a time sufficient to hydrorefine at least a portion of the feed

Preparation, characterization of Mo catalysts supported on Ni- containing calcium deficient hydroxyapatite and reactivity for the thiophene HDS reaction

Directory of Open Access Journals (Sweden)

Cherif A.

2013-09-01

Full Text Available Ni-containing Calcium Hydroxyapatite (NiCaHAp; 3.31 wt.% Ni was synthesized by coprecipitation and used as catalyst support. Molybdenum was supported on NiCaHAp by impregnation using ammonium heptamolybdate. The prepared catalysts Mo(x/NiCaHAp (x: 2 to 8 wt % in Mo were characterized by elemental analysis, XRD, FT-IR, N2 adsorption-desorption and TEM-EDX. The catalysts were sulfided in-situ at 673 K under flowing H2S/H2 (15 Vol.% H2S and tested in hydrodesulfurization (HDS of thiophene at 673 K. The main XRD peaks of hydroxyapatite CaHAp phase were observed in all samples and a peak due probably to crystalline MoO3 phase was also identified from the results. However, no crystalline phase of NiO was found for the catalysts, which showed its Ni species were highly dispersed. The sulfided catalysts Mo(x/NiCaHAp presented are active in HDS of thiophene, despite the presence of some large MoO3 crystallites and incomplete sulfidation. This activity may be due to interaction of NiO and MoO3 on CaHAp resulting in the formation of Ni-Mo-S phase under flowing H2S/H2. When the molybdenum content increased the HDS activity increasead slightly, which was caused by the agglomeration of MoO3. The Mo(8/NiCaHAp catalyst is about two times less active for thiophene HDS than the commercial NiMoP/Al2O3.

The structure and function of supported molybdenum nitride and molybdenum carbide hydrotreating catalysts

Science.gov (United States)

Dolce, Gregory Martin

1997-11-01

A series of gamma-Alsb2Osb3 supported molybdenum nitrides and carbides were prepared by the temperature programmed reaction of supported molybdates with ammonia and methane/hydrogen mixtures, respectively. In the first part of this research, the effects of synthesis heating rates and molybdenum loading on the catalytic properties of the materials were examined. A significant amount of excess carbon was deposited on the surface of the carbides during synthesis. The materials consisted of small particles which were very highly dispersed. Oxygen chemisorption indicated that the nitride particles may have been two-dimensional. The dispersion of the carbides, however, appeared to decrease as the loading increased. The catalysts were evaluated for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). The molybdenum loading had the largest effect on the activity of the materials. For the nitrides, the HDN and HDS activities were inverse functions of the loading. This suggested that the most active HDN and HDS sites were located at the perimeter of the two-dimensional particles. The HDN and HDS activities of the carbides followed the same trend as the oxygen uptake. This result suggested that oxygen titrated the active sites on the supported carbides. Selected catalysts were evaluated for methylcarbazole HDN, dibenzothiophene HDS, and dibenzofuran HDO. The activity and selectivity of the nitrides and carbides were competitive with a presulfided commercial catalyst. In the second part of this work, a series of supported nitrides and carbides were prepared using a wider range of loadings (5-30 wt% Mo). Thermogravimetric analysis was used to determine the temperature at which excess carbon was deposited on the carbides. By modifying the synthesis parameters, the deposition of excess carbon was effectively inhibited. The dispersions of the supported nitrides and carbides were constant and suggested that the materials consisted of two

The effect of passivation on the activity and structure of sulfided hydrotreating catalysts

NARCIS (Netherlands)

Louwers, S.P.A.; Crajé, M.W.J.; Kraan, van der A.M.; Geantet, C.; Prins, R.

1993-01-01

Air exposure (passivation) and subsequent resulfidation caused a substantial increase in the thiophene hydrodesulfurization activity of sulfided Co-Mo/Al2O3 catalysts. Since no effect was observed for Mo/Al2O3 and Co/Al2O3 catalysts, the passivation effect must be related to the Co---Mo---S

Effect of thermal treatment conditions on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid

International Nuclear Information System (INIS)

Gorshkova, T.P.; Tarasova, D.V.; Olen'kova, I.P.; Andrushkevich, T.V.; Nikoro, T.A.

1984-01-01

The effect of thermal treatment conditions (temperature and gas medium) on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid is investigated. It is shown that active and selective catalysts are formed in the course of thermal decomposition of the drying product of ammonium metavanadate and paramolybdate under the conditions ensuring the vanadium ion reduction up to tetravalent state with conservation of molybdenum oxidation degree equal to 6. It is possible to realize it either by treatment of the catalyst calcinated in the air flow at 300 deg by the reaction mixture at the activation stage or by gas-reducer flow treatment at 280 deg. Thermal treatment in the reducing medium of the oxidized catalyst does not lead to complete regeneration of its properties

Secondary promoters in alumina-supported nickel-molybdenum hydroprocessing catalysts

Energy Technology Data Exchange (ETDEWEB)

Lewis, J.M.

1992-01-01

Two secondary promoters, phosphorus and fluoride, have been investigated for their influences on the physicochemical properties of alumina-supported nickel-molybdenum hydroprocessing catalysts. Model compound reactions and infrared spectroscopy were used to probe the functionalities of the different catalysts, and the catalysts were tested in the hydroprocessing of a low-nitrogen and a high-nitrogen (quinoline-spiked) gas oil feed to assess the utility of the model compound reaction studies. Fluoride-promoted catalysts with high cumene hydrocracking activity and with comparable thiophene hydrodesulphurization (HDS) activity to Ni-Mo/Al[sub 2]O[sub 3] can be prepared by coimpregnation of the F, Ni and Mo additives. Fluoride promotes the hydrogenation (HYD) and HDS activity of Ni-Mo/Al[sub 2]O[sub 3] in the hydroprocessing (HYD) and HDS activity of Ni-Mo/Al[sub 2]O[sub 3] in the hydroprocessing of a low-nitrogen feed. Fluoride promotes the quinoline hydrodenitrogenation (HDN) activity of Ni-Mo/Al[sub 2]O[sub 3] catalysts. Impregnation of phosphorus prior to the metal additives results in catalysts which are more active in HDS. Phosphorus increases indirectly the Broensted acidity of the catalyst by increasing the activity of the MoS[sub 2]-associated acid sites. Phosphorus promotes the HDSW and HYD activities of Ni-Mo/Al[sub 2]O[sub 3] in the hydroprocessing of the low-N feed. A promotional effect of phosphorus is seen in quinoline HDN. P- and F-promoted Ni-MO/Al[sub 2]O[sub 3] catalysts are very active in quinoline HDN and maintain good activity in HDS and HYD of the high-N feed. Thiophene HDS was a good reaction for probing the activity of catalysts in the HDS of sterically-unhindered molecules, but an inaccurate probe for the HDS of hindered compounds.

Catalytic oxidation of sulfide in drinking water treatment: activated carbon as catalyst; Katalytische Oxidation von Sulfid bei der Trinkwasseraufbereitung: Aktivkohle als Katalysator

Energy Technology Data Exchange (ETDEWEB)

Hultsch, V; Grischek, T; Wolff, D; Worch, E [Technische Univ. Dresden (Germany). Inst. fuer Wasserchemie; Gun, J [Hebrew Univ. of Jerusalem (Israel). Div. of Environmental Sciences, Fredy and Nadine Herrmann School of Applied Science

2001-07-01

In regions with warm climate and limited water resources high sulfide concentrations in groundwater can cause problems during drinking water treatment. Aeration of the raw water is not always sufficient to ensure the hydrogen sulfide concentration below the odour threshold value for hydrogen sulfide. As an alternative, activated carbon can be used as a catalyst for sulfide oxidation of raw water. The use of different types of activated carbon was investigated in kinetic experiments. Both Catalytic Carbon from Calgon Carbon and granulated activated carbon from Norit showed high catalytic activities. The results of the experiments are discussed with regard to the practical use of activated carbon for the elimination of hydrogen sulfide during drinking water treatment. (orig.)

Electron Tomography Reveals the Active Phase–Support Interaction in Sulfidic Hydroprocessing Catalysts

NARCIS (Netherlands)

Eijsbouts, Sonja; Li, Xuang; Juan-Alcaniz, Jana; van den Oetelaar, Leon C A; Bergwerff, Jaap; Loos, Joachim; Carlsson, Anna; Vogt, E.T.C.

2017-01-01

Conventional two-dimensional (2D) transmission electron microscopy of sulfidic hydroprocessing catalysts can be deceiving and give the impression that parts of the support are overloaded with active phase. High-angle annular dark field scanning transmission electron microscopy tomography reveals

A novel process for heavy residue hydroconversion using a recoverable pseudo-homogenous catalyst PHC system

Energy Technology Data Exchange (ETDEWEB)

Romocki, S.M.; Rhodey, W.G. [Mobis Energy Inc., Calgary, AB (Canada)

2008-10-15

This paper described a pseudo-homogenous catalyst (PHC) designed to refine heavy hydrocarbon residues containing sulfur, nitrogen, metals, and asphaltene impurities known to clog pores and deactivate traditional hydrocrackers. The heavy residue hydroconversion (HRH) process incorporated a single particle, chemically generated PHC uniformly distributed in the feed. Thermal decomposition within the reaction system of a water-in-oil emulsion containing ammonium paramolybdate was used to form molybdenum oxide, which was then sulfided within the feed in order to create an ultra-dispersed suspension of catalytically active molybdenum disulfide particles measuring between 2 and 9 nm. A proprietary online catalyst recovery and regeneration step was used to maintain high catalyst activity. The molybdenum was then recovered from a purge stream and then reintroduced to the catalyst preparation area as a catalyst precursor. After being conditioned, the feed was combined with hydrogen and a water-oil catalyst emulsion and introduced into a furnace. Heavy components were cracked, hydrogenated and converted to lighter products. The high performance catalyst system was able to convert 95 per cent of residues at pressures below 7.3 Mpa and at reaction temperatures ranging between 400 and 460 degrees C. The catalyst was tested at a pilot plant using Athabasca vacuum bottoms. It was concluded that the HRH process is now being successfully used to produce 200 barrels of heavy oil per day. Designs for commercial installations are now being prepared. 4 refs., 2 tabs., 2 figs.

Structure, activity and kinetics of supported molybdenum oxide and mixed molybdenum-vanadium oxide catalysts prepared by flame spray pyrolysis for propane OHD

DEFF Research Database (Denmark)

Høj, Martin; Kessler, Thomas; Beato, Pablo

2013-01-01

reflectance UV-vis spectroscopy and evaluated as catalysts for the oxidative dehydrogenation (ODH) of propane. The results show that samples with high specific surface areas between 122 and 182 m2/g were obtained, resulting in apparent MoOx and VOx surface densities from 0.7 to 7.7 nm -2 and 1.5 to 1.9 nm-2......, respectively. Raman spectroscopy, UV-vis spectroscopy and XRD confirmed the high dispersion of molybdenum and vanadia species on γ-Al2O3 as the main crystalline phase. Only at the highest loading of 15 wt% Mo, with theoretically more than monolayer coverage, some crystalline molybdenum oxide was observed...

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

Science.gov (United States)

Wagner, Meghan; Chappaz, Anthony; Lyons, Timothy W.

2017-06-01

Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth's history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes-many containing organic ligands-we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H2S(aq)] < 11 μM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO3, MoOxS4-x2- (intermediate thiomolybdates), and [MoOx(cat)4-x]2- (cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS42- (tetrathiomolybdate).

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

Energy Technology Data Exchange (ETDEWEB)

Wagner, Meghan; Chappaz, Anthony; Lyons, Timothy W.

2017-06-01

Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth’s history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes—many containing organic ligands—we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H2S(aq)] < 11 µM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO3, MoOxS4-x2- (intermediate thiomolybdates), and [MoOx(cat)4-x]2- (cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS42- (tetrathiomolybdate).

Synthesis of carbon nanotubes by CVD method using iron and molybdenum-based catalysts supported on ceramic matrices

International Nuclear Information System (INIS)

Teixeira, Ana Paula de Carvalho

2010-01-01

Molybdenum is known for its synergistic effect in the synthesis of carbon nanotubes (CNs) by chemical vapor deposition (CVD method). When added to typical catalysts like iron, nickel, and cobalt, even in small quantities, it is increases the yield of these nanostructures. The presence of Mo also has an influence on the type and number of CN walls formed. Although this effect is widely documented in the literature, there is not yet a consensus about the mechanism of action of molybdenum in catalytic systems. The objective of the present work is to study the influence of molybdenum on the catalytic activity of iron nanoparticle-based catalysts supported on magnesium oxide (Fe/MgO system) in the synthesis of carbon nanotubes by the CVD method. The Mo concentration was systematically varied from null to molar ratio values four times greater than the quantity of Fe, and the obtained material (catalysts and carbon nanotubes) were broadly characterized by different techniques. In order to also study the influence of the preparation method on the final composition of the catalytic system phases, the catalytic systems (Fe/MgO e FeMo x /MgO) were synthesized by two different methods: co-precipitation and impregnation. The greatest CN yields were observed for the catalysts prepared by coprecipitation. The difference was attributed to better dispersion of the Fe and Mo phases in the catalyst ceramic matrix. In the precipitation stage, it was observed the formation of layered double hydroxides whose concentration increased with the Mo content up to the ratio of Mo/Fe equal to 0.2. This phase is related to a better distribution of Fe and Mo in this concentration range. Another important characteristic observed is that the ceramic matrix is not inert. It can react both with Fe and Mo and form the iron solid solution in the magnesium oxide and the phases magnesium-ferrite (MgFe 2 0 4 ) and magnesium molybdate (MgMo0 4 ). The MgFe 2 0 4 phase is observed in all catalytic systems

“Non-hydrolytic” sol–gel synthesis of molybdenum sulfides

Energy Technology Data Exchange (ETDEWEB)

Leidich, Saskia; Buechele, Dominique; Lauenstein, Raphael; Kluenker, Martin; Lind, Cora, E-mail: cora.lind@utoledo.edu

2016-10-15

Non-hydrolytic sol–gel reactions provide a low temperature solution based synthetic approach to solid-state materials. In this paper, reactions between molybdenum chloride and hexamethyldisilthiane in chloroform were explored, which gave access to both MoS{sub 2} and Mo{sub 2}S{sub 3} after heat treatment of as-recovered amorphous samples to 600–1000 °C. Interesting morphologies were obtained for MoS{sub 2}, ranging from fused spherical particles to well-defined nanoplatelets and nanoflakes. Both 2H- and 3R-MoS{sub 2} were observed, which formed thin hexagonal and triangular platelets, respectively. The platelets exhibited thicknesses of 10–30 nm, which corresponds to 15–50 MoS{sub 2} layers. No attempts to prevent agglomeration were made, however, well separated platelets were observed for many samples. Heating at 1000 °C led to formation of Mo{sub 2}S{sub 3} for samples that showed well-defined MoS{sub 2} at lower temperatures, while less crystalline samples had a tendency to retain the MoS{sub 2} structure. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • Molybdenum sulfides were prepared by non-hydrolytic sol–gel chemistry. • Nanocrystalline 3R-MoS{sub 2} and 2H-MoS{sub 2}, and microcrystalline Mo{sub 2}S{sub 3} were obtained. • Particle morphology correlated strongly with crystalline phases. • Ultrathin platelets with limited tendency to agglomerate were recovered.

Investigation of the oxidative ammonolysis of propylene on oxide catalysts containing molybdenum and using the response method

International Nuclear Information System (INIS)

Gadzhiev, K.N.; Adzhamov, K.Y.; Alkhazov, T.G.; Khanmamedova, A.K.

1985-01-01

The response method has been used to study the oxidative ammonolysis of propylene on MoO 3 and molybdenum oxide systems containing bismuth, silicon, and phosphorous ions. The response curves obtained for ammonia, propylene, CO 2 , acrolein, acrylonitrile in these systems are discussed and compared with individual molybdenum trioxide. It has been shown that the modifying action of ammonia on the catalyst surfaces determines the direction of the oxidative conversion of the propylene

Hydroprocessing of Jatropha Oil for Production of Green Diesel over Non-sulfided Ni-PTA/Al2O3 Catalyst

Science.gov (United States)

Liu, Jing; Lei, Jiandu; He, Jing; Deng, Lihong; Wang, Luying; Fan, Kai; Rong, Long

2015-01-01

The non-sulfided Ni-PTA/Al2O3 catalyst was developed to produce green diesel from the hydroprocessing of Jatropha oil. The Ni-PTA/Al2O3 catalyst was prepared by one-pot synthesis of Ni/Al2O3 with the co-precipitation method and then impregnanting Ni/Al2O3 with PTA solution. The catalysts were characterized with BET, SEM-EDX, TEM, XRD, XPS, TGA and NH3-TPD. The Ni and W species of the Ni-PTA/Al2O3 catalyst were much more homogeneously distributed on the surface than that of commercial Al2O3. Catalytic performance in the hydroprocessing of Jatropha oil was evaluated by GC. The maximum conversion of Jatropha oil (98.5 wt%) and selectivity of the C15-C18 alkanes fraction (84.5 wt %) occurred at 360 °C, 3.0 MPa, 0.8 h−1. The non-sulfided Ni-PTA/Al2O3 catalyst is more environmentally friendly than the conventional sulfided hydroprocessing catalyst, and it exhibited the highest catalytic activity than the Ni-PTA catalyst supported with commercial Al2O3 grain and Al2O3 powder. PMID:26162092

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

Energy Technology Data Exchange (ETDEWEB)

Wagner, Meghan; Chappaz, Anthony; Lyons, Timothy W.

2017-06-01

Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth’s history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes—many containing organic ligands—we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H₂S_(aq)] < 11 µM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO₃, MoO_xS_4-x^2- (intermediate thiomolybdates), and [MoO_x(cat)_4-x]^2- (cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS₄^2- (tetrathiomolybdate).

Electrochemical deposition of molybdenum sulfide thin films on conductive plastic substrates as platinum-free flexible counter electrodes for dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Cheng, Chao-Kuang; Hsieh, Chien-Kuo, E-mail: jack_hsieh@mail.mcut.edu.tw

2015-06-01

In this study, pulsed electrochemical deposition (pulsed ECD) was used to deposit molybdenum sulfide (MoS{sub x}) thin films on indium tin oxide/polyethylene naphthalate (ITO/PEN) substrates as flexible counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The surface morphologies and elemental distributions of the prepared MoS{sub x} thin films were examined using field-emission scanning electron microscope (FE-SEM) equipped with energy-dispersive X-ray spectroscopy. The chemical states and crystallinities of the prepared MoS{sub x} thin films were examined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The optical transmission (T (%)) properties of the prepared MoS{sub x} samples were determined by ultraviolet–visible spectrophotometry. Cyclic voltammetry (CV) and Tafel-polarization measurements were performed to analyze the electrochemical properties and catalytic activities of the thin films for redox reactions. The FE-SEM results showed that the MoS{sub x} thin films were deposited uniformly on the ITO/PEN flexible substrates via the pulsed ECD method. The CV and Tafel-polarization curve measurements demonstrated that the deposited MoS{sub x} thin films exhibited excellent performances for the reduction of triiodide ions. The photoelectric conversion efficiency (PCE) of the DSSC produced with the pulsed ECD MoS{sub x} thin-film CE was examined by a solar simulator. In combination with a dye-sensitized TiO{sub 2} working electrode and an iodine-based electrolyte, the DSSC with the MoS{sub x} flexible CE showed a PCE of 4.39% under an illumination of AM 1.5 (100 mW cm{sup −2}). Thus, we report that the MoS{sub x} thin films are active catalysts for triiodide reduction. The MoS{sub x} thin films are prepared at room temperature and atmospheric pressure and in a simple and rapid manner. This is an important practical contribution to the production of flexible low-cost thin-film CEs based on plastic substrates. The MoS{sub x

Phase composition and catalytic properties of oxide multicomponent molybdenum-containing catalysts for partial oxidation of propylene

International Nuclear Information System (INIS)

Malakhov, V.V.; Vlasov, A.A.; Boldyreva, N.N.; Dovlitova, L.S.; Plyasova, L.M.; Andrushkevich, T.V.; Kuznetsova, T.G.

1996-01-01

The catalytic properties and phase composition of multicomponent molybdenum-containing catalyst treated under various redox conditions have been studied. The phase composition has been considered by the methods of X-ray phase analysis and noncalibrated methods of differentiating dissolution (DD). Using the DD method the data on element composition, stoichiometry and quantitative content of phases of complex molybdates have been obtained for the first time. Data on modification of basic phases of the catalyst-cobalt and iron molybdates - by other cations from its composition suggest that the mechanism of action of the multicomponent catalyst is defined by the properties of one or several formed modified phases combining all the functions of an effective catalyst. 18 refs., 7 figs., 2 tabs

Friction behaviour of anodic oxide film on aluminum impregnated with molybdenum sulfide compounds

Energy Technology Data Exchange (ETDEWEB)

Maejima, M.; Saruwatari, K. [Fujikura Ltd., Tokyo (Japan); Takaya, M. [Faculty of Engineering, Chiba Institute of Technology 17-1, Tsudanuma 2-Chome, 275-0016, Narasino-shi Chiba (Japan)

2000-10-23

In order to improve the lubricity and wear resistance of aluminum anodic oxide films, it is necessary to ensure the film layers are dense to prevent cracking, and to harden the films as well as reduce the shear stress of the film surfaces. From this view point, lubricious, hard anodic oxide films have been studied in the past, but fully satisfactory results have yet to be realized. In this paper, we report on our study of the re-anodizing of anodic oxide film in an aqueous solution of (NH)MoS. Molybdenum sulfide and compounds filled the 20-nm diameter pores of the film, creating internal stress which compressed the film, suppressing the occurrence of cracks and reducing the friction coefficient. (orig.)

Study on supported binary sulfide catalysts for secondary hydrogenation of coal-derived liquids; Sekitan ekikayu niji suisoka shokubai no kenkyu

Energy Technology Data Exchange (ETDEWEB)

Shimada, H.; Matsubayashi, N.; Sato, T.; Imamura, M.; Yoshimura, Y.; Nishijima, A. [National Institute of Materials and Chemical Research, Tsukuba (Japan)

1995-07-28

To utilize the high performance of supported catalysts in coal liquefaction processes, one of the promising ways is to apply hydroprocessing sulfide catalysts to the secondary hydrogenation of coal-derived liquids which have undergone the solid separation unit. However, when the product yield from the first-stage liquefaction is maximized, the feed stocks in the secondary hydrogenation contain large amounts of residual fractions with preasphaltenes and metallic components. In this case, the development of a long-life catalyst is essential to establish the two-stage process as a practical one. From this viewpoint, the authors have investigated the deactivation causes of supported Ni-Mo sulfide catalysts through the analysis of the used catalysts in the secondary hydrogenation of coal-derived liquids for long periods. The major cause of the catalyst deactivation has been found to be metallic and carbonaceous deposition on the catalyst, which results thin layer which covers the catalyst particles. The catalysts located at the reactor inlet are more rapidly deactivated than those at the rector exit because of larger amounts of metallic foul ants and the above described shell-like layer. Hydrocracking active sites are much heavily deactivated compared with hydrogenation active sites. It is inferred that the basic or polar compounds contained in coal liquids are permanency adsorbed on the hydrocracking active sites. Spectroscopic analysis of the used catalysts clarified the destruction of the active phase of the binary sulfides, through the segregation and crystal growth. The structural changes of the catalysts are very likely caused by heteroatom compounds in the preasphaltenes. Thus, the primary cause of the catalyst deactivation is the preasphaltenes in the coal liquids. Hydroaromatic compounds in the coal liquids suppress the change of the deposited carbonaceous materials into inert coke which permanently deactivate the catalyst.

Catalytic conversion of CO, NO and SO2 on supported sulfide catalysts. Part 2. Catalytic reduction of NO and SO2 by CO

International Nuclear Information System (INIS)

Zhuang, S.-X.; Yamazaki, M.; Omata, K.; Takahashi, Y.; Yamada, M.

2001-01-01

To investigate the possibility of simultaneous catalytic reduction of NO and SO 2 by CO, reactions of NO, NO-CO, and NO-SO 2 -CO were performed on γ-alumina-supported sulfides of transition metals including Co, Mo, CoMo and FeMo. NO was decomposed into N 2 O and N 2 accompanied with the formation of SO 2 ; this serious oxidation of lattice sulfur resulted in the deactivation of the catalysts. The addition of CO to the NO stream suppressed SO 2 formation and yielded COS instead. A stoichiometric conversion of NO and CO to N 2 and CO 2 was observed above 350C on the CoMo and the FeMo catalysts. Although the CO addition lengthened catalyst life, it was not enough to maintain activity. After the NO-CO reaction, an XPS analysis showed the growth of Mo 6+ and SO 4 2- peaks, especially for the sulfided FeMo/Al 2 O 3 ; the FeMo catalyst underwent strong oxidation in the NO-CO reaction. The NO and the NO-CO reactions proceeded non-catalytically, consuming catalyst lattice sulfur to yield SO 2 or COS. The addition of SO 2 in the NO-CO system enabled in situ regeneration of the catalysts; the catalysts oxidized through abstraction of lattice sulfur experienced anew reduction and sulfurization through the SO 2 -CO reaction at higher temperature. NO and SO 2 were completely and catalytically converted at 400C on the sulfided CoMo/Al 2 O 3 . By contrast, the sulfided FeMo/Al 2 O 3 was easily oxidized by NO and hardly re-sulfided under the test conditions. Oxidation states of the metals before and after the reactions were determined. Silica and titania-supported CoMo catalysts were also evaluated to study support effects

Co-Processing of Jatropha-Derived Bio-Oil with Petroleum Distillates over Mesoporous CoMo and NiMo Sulfide Catalysts

Directory of Open Access Journals (Sweden)

Shih-Yuan Chen

2018-02-01

Full Text Available The co-processing of an unconventional type of Jatropha bio-oil with petroleum distillates over mesoporous alumina-supported CoMo and NiMo sulfide catalysts (denoted CoMo/γ-Al2O3 and NiMo/γ-Al2O3 was studied. Either a stainless-steel high-pressure batch-type reactor or an up-flow fixed-bed reaction system was used under severe reaction conditions (330–350 °C and 5–7 MPa, similar to the conditions of the conventional diesel hydrodesulfurization (HDS process. To understand the catalytic performance of the mesoporous sulfide catalysts for co-processing, we prepared two series of oil feedstocks. First, model diesel oils, consisting of hydrocarbons and model molecules with various heteroatoms (sulfur, oxygen, and nitrogen were used for the study of the reaction mechanisms. Secondly, low-grade oil feedstocks, which were prepared by dissolving of an unconventional type of Jatropha bio-oil (ca. 10 wt % in the petroleum distillates, were used to study the practical application of the catalysts. Surface characterization by gas sorption, spectroscopy, and electron microscopy indicated that the CoMo/γ-Al2O3 sulfide catalyst, which has a larger number of acidic sites and coordinatively unsaturated sites (CUS on the mesoporous alumina framework, was associated with small Co-incorporated MoS2-like slabs with high stacking numbers and many active sites at the edges and corners. In contrast, the NiMo/γ-Al2O3 sulfide catalyst, which had a lower number of acidic sites and CUS on mesoporous alumina framework, was associated with large Ni-incorporated MoS2-like slabs with smaller stacking numbers, yielding more active sites at the brims and corresponding to high hydrogenation (HYD activity. Concerning the catalytic performance, the mesoporous CoMo/γ-Al2O3 sulfide catalyst with large CUS number was highly active for the conventional diesel HDS process; unfortunately, it was deactivated when oxygen- and nitrogen-containing model molecules or Jatropha bio

Atomic-scale investigation of the interaction of organic molecules with MoS₂-based hydrotreating model catalysts

DEFF Research Database (Denmark)

Salazar Moreira, Norberto José

The aim of this work is to provide new insight into the formation, activation and reactivity of hydrotreating catalysts extensively used in the refinery for the conversion of heavy feedstocks and for improving the quality of the final oil products. This is done through numerous studies of the con......The aim of this work is to provide new insight into the formation, activation and reactivity of hydrotreating catalysts extensively used in the refinery for the conversion of heavy feedstocks and for improving the quality of the final oil products. This is done through numerous studies...... of the conversion of molybdenum oxides and metallic precursors into molybdenum disulfide (MoS2), the active phase involved in most of the hydrotreating reactions, especially for those dedicated to the removal of sulfur from various fuel fractions, commonly referred to as hydrodesulfurization (HDS). The evolution...... the presence of the reduced MoOx phase impedes the MoS2 growth and leads to rather stable amorphous oxysulfide phases. The sulfidation in H2S atmosphere of molybdenum metal and bimetallic cobalt-molybdenum clusters deposited on Au(111) facilitate instead the formation of well-dispersed MoS2 and Co-promoted Mo...

Reactivity of a Carbon-Supported Single-Site Molybdenum Dioxo Catalyst for Biodiesel Synthesis

Energy Technology Data Exchange (ETDEWEB)

Mouat, Aidan R.; Lohr, Tracy L.; Wegener, Evan C.; Miller, Jeffrey T.; Delferro, Massimiliano; Stair, Peter C.; Marks, Tobin J.

2016-08-23

A single-site molybdenum dioxo catalyst, (O_c)₂Mo(=O)₂@C, was prepared via direct grafting of MoO₂Cl₂(dme) (dme = 1,2-dimethoxyethane) on high-surface- area activated carbon. The physicochemical and chemical properties of this catalyst were fully characterized by N₂ physisorption, ICP-AES/OES, PXRD, STEM, XPS, XAS, temperature-programmed reduction with H₂ (TPR-H₂), and temperature-programmed NH₃ desorption (TPD-NH₃). The single-site nature of the Mo species is corroborated by XPS and TPR-H₂ data, and it exhibits the lowest reported MoO_x Tmax of reduction reported to date, suggesting a highly reactive MoVI center. (O_c)₂Mo(=O)₂@C catalyzes the transesterification of a variety of esters and triglycerides with ethanol, exhibiting high activity at moderate temperatures (60-90 °C) and with negligible deactivation. (O_c)₂Mo(=O)₂@C is resistant to water and can be recycled at least three times with no loss of activity. The transesterification reaction is determined experimentally to be first order in [ethanol] and first order in [Mo] with ΔH = 10.5(8) kcal mol^-1 and ΔS = -32(2) eu. The low energy of activation is consistent with the moderate conditions needed to achieve rapid turnover. This highly active carbon-supported single-site molybdenum dioxo species is thus an efficient, robust, and lowcost catalyst with significant potential for transesterification processes.

Catalytic oxidation of albendazole using molybdenum supported on carbon nanotubes as catalyst

International Nuclear Information System (INIS)

Sun-Kou, Maria del Rosario; Vega Carrasco, Edgar R.; Picasso Escobar, Gino I.

2013-01-01

The catalytic oxidation reaction of the thioether group (-S-) in the structure to the drug albendazole (C 12 H 15 N 3 O 2 S) was studied in order to obtain a pharmacologically active molecule known as albendazole sulfoxide. With this purpose, three heterogeneous catalysts were prepared using molybdenum (Mo) as active phase and carbon nanotubes as a multiple-layer catalyst support. The incorporation of the active phase was performed by wet impregnation, with subsequent calcination for 4 hours at 400 o C. For the catalytic oxidation reaction was employed hydrogen peroxide-urea (H 2 NCONH 2 ·H 2 O 2 ) as oxidizing agent and methanol (CH 3 OH) as reaction medium. The textural and morphology characterization of carbon nanoparticles and catalysts was carried out by adsorption-desorption of N 2 (BET) and scanning electron microscopy (SEM). The identification and quantification of the reaction products were followed by Fourier transform infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC), respectively. With the yield, selectivity and conversion higher than 90% after 60 minutes of reaction, albendazole sulphoxide was obtained as major product of oxidation reaction. (author)

Nitrogen reduction: Molybdenum does it again

Science.gov (United States)

Schrock, Richard R.

2011-02-01

Nature reduces dinitrogen under mild conditions using nitrogenases, the most active of which contains molybdenum and iron. The only abiological dinitrogen reduction catalyst that avoids the harsh conditions of the Haber-Bosch process contains just molybdenum.

Supported transition metal sulfide promoted molybdenum or tungsten sulfide catalysts and their uses for hydroprocessing

International Nuclear Information System (INIS)

Ho, T.C.; Chianelli, R.R.; Jacobson, A.J.; Young, A.R.

1987-01-01

A process is described for hydrotreating a hydrocarbon feed which comprises contacting the feed at a temperature of at least about 150 0 C and heating the composite at elevated temperature of at least about 150 0 C, in the presence of sulfur and under oxygen-free conditions for a time sufficient to form the catalyst. The precursor salt contains a tetrathiometallate anion of Mo, W or mixture thereof and a cation comprising one or more divalent promoter metals which are chelated by at least one neutral, nitrogen-containing polydentate ligand L. The divalent promoter metal is selected from the group consisting of Ni, Co, Zn, Cu and mixture thereof. The contacting occurs for a time sufficient to hydrotreat at least a portion of the feed

Experiment on bio-leaching of associated molybdenum and uranium ore

International Nuclear Information System (INIS)

Zheng Ying; Fan Baotuan; Liu Jian; Meng Yunsheng; Liu Chao

2007-01-01

Column leaching experiment results on associated molybdenum uranium ore by bacteria (T. f) are introduced. The ore are leached for 210 days using bacteria domesticated to tolerate molybdenum, the leaching of uranium is of 98% and leaching of molybdenum is of 41%. Sulphuric acid produced by bio-oxidation of sulfides in ore can meet the demand of ore leaching. (authors)

Influence of the sulfidation procedure on the performance and the selectivity of hydro-treating catalysts; Influence de la procedure de sulfuration sur la performance et la selectivite des catalyseurs d'hydrotraitement

Energy Technology Data Exchange (ETDEWEB)

Texier, S

2004-10-15

This work is part of a general effort to reduce the sulfur content of fuels to satisfy new European regulations. The objective was to determine the influence of several activating agents during sulfidation on the activity of hydro-desulfurization (HDS) catalysts. Indeed, sulfidation is a critical step to achieve a good level of HDS activity on sulfide catalysts. Under industrial conditions, the activation by organo-sulfide compounds would be more beneficial to obtain active catalysts than the use of hydrogen sulfide. A systematic study of the various operational parameters of the activation process was thus carried out by comparing precisely activation by H{sub 2}S or by organo-sulfides. This study reveals that the recognized advantage of organo-sulfides compounds has not a 'purely chemical origin' but would be more probably related to a heating and/or thermodynamic effect which depends on the processes and on the implementation of sulfidation under the industrial conditions. (author)

Influence of the sulfidation procedure on the performance and the selectivity of hydro-treating catalysts; Influence de la procedure de sulfuration sur la performance et la selectivite des catalyseurs d'hydrotraitement

Energy Technology Data Exchange (ETDEWEB)

Texier, S.

2004-10-15

This work is part of a general effort to reduce the sulfur content of fuels to satisfy new European regulations. The objective was to determine the influence of several activating agents during sulfidation on the activity of hydro-desulfurization (HDS) catalysts. Indeed, sulfidation is a critical step to achieve a good level of HDS activity on sulfide catalysts. Under industrial conditions, the activation by organo-sulfide compounds would be more beneficial to obtain active catalysts than the use of hydrogen sulfide. A systematic study of the various operational parameters of the activation process was thus carried out by comparing precisely activation by H{sub 2}S or by organo-sulfides. This study reveals that the recognized advantage of organo-sulfides compounds has not a 'purely chemical origin' but would be more probably related to a heating and/or thermodynamic effect which depends on the processes and on the implementation of sulfidation under the industrial conditions. (author)

Comparison of P-containing {gamma}-Al{sub 2}O{sub 3} supported Ni-Mo bimetallic carbide, nitride and sulfide catalysts for HDN and HDS of gas oils derived from Athabasca bitumen

Energy Technology Data Exchange (ETDEWEB)

Sundaramurthy, V.; Dalai, A.K. [Catalysis and Chemical Reaction Engineering Laboratories, Department of Chemical Engineering, University of Saskatchewan, Saskatoon, SK (Canada); Adjaye, J. [Syncrude Edmonton Research Centre, Edmonton, AB (Canada)

2006-09-01

Phosphorus containing {gamma}-Al{sub 2}O{sub 3} supported bimetallic Ni-Mo carbide, nitride and sulfide catalysts have been synthesized from an oxide precursor containing 12.73wt.% Mo, 2.54wt.% Ni and 2.38wt.% P and characterized by elemental analysis, pulsed CO chemisorption, surface area measurements, X-ray diffraction, temperature-programmed reduction and DRIFT spectroscopy of CO adsorption. DRIFT spectroscopy of adsorbed CO on activated catalysts showed that carbide and nitride catalysts have surface exposed sites of Mo{sup o+} (0sulfidation with H{sub 2}S/H{sub 2} mixture at 370{sup o}C. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of the bimetallic Ni-Mo carbide, nitride and sulfide catalysts were compared against commercial Ni-Mo/Al{sub 2}O{sub 3} catalyst in a trickle bed reactor using light gas oil and heavy gas oil derived from Athabasca bitumen in the temperature range 340-370 and 375-400{sup o}C respectively at 8.8MPa. The gradual transformation of Ni-Mo carbide and nitride phases into Ni-Mo sulfide phases was observed during precoking period, and the formed Ni-Mo sulfide phases enhanced the HDN and HDS activities of carbide and nitride catalysts. The {gamma}-Al{sub 2}O{sub 3} supported Ni-Mo bimetallic sulfide catalyst was found to be more active for HDN and HDS of light gas oil and heavy gas oil than the corresponding carbide and nitride catalysts on the basis of unit weight. (author)

HDS, HDN and HDA activities of nickel-molybdenum catalysts supported on alumina

Energy Technology Data Exchange (ETDEWEB)

Dominguez-Crespo, M.A. [Instituto Mexicano del Petroleo, Programa de Tratamiento de Crudo Maya. Avenida Eje Central Lazaro Cardenas No.152, Col. San Bartolo Atepehuacan, 07730, Mexico D. F. (Mexico); Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA-Altamira, IPN) Km 14.5 Carretera Tampico-puerto Industrial 89600, Altamira, Tamaulipas (Mexico); Torres-Huerta, A.M.; Ramirez-Meneses, E. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA-Altamira, IPN) Km 14.5 Carretera Tampico-puerto Industrial 89600, Altamira, Tamaulipas (Mexico); Diaz-Garcia, L. [Instituto Mexicano del Petroleo, Programa de Tratamiento de Crudo Maya. Avenida Eje Central Lazaro Cardenas No.152, Col. San Bartolo Atepehuacan, 07730, Mexico D. F. (Mexico); Arce-Estrada, E.M. [Instituto Politecnico Nacional, Departamento de Metalurgia y Materiales. A.P. 75-876, 07300 Mexico, D. F. (Mexico)

2008-08-15

In this work, NiMo-Al{sub 2}O{sub 3} catalysts were prepared by using different alumina precursors. The supports were impregnated by means of the spray at incipient wetness technique in both basic and acid media. Both the supports and fresh catalysts were characterized by the adsorption-desorption isotherms, Temperature-Programmed Reduction (TPR), Thermal Pyridine Adsorption-Desorption (TPD) and X-Ray Diffraction analyses (XRD). After sulfidation, the NiMoS metallic particles were characterized by Transmission Electron Microscopy (TEM). The initial analyses were performed in a trickle-bed reactor by using a real feedstock (Mexican heavy gas oil) and performing hydrotreating reactions (HDS, HDN and HDA) at three different temperatures: 613, 633 and 653 K; and 54 kg cm{sup -} {sup 2}. The catalytic activities are discussed in relation to the physicochemical properties of the NiMo catalysts, alumina phase and pH of the impregnating solution. The catalytic results show an increase in the conversion profiles with temperature. The sulfur conversion was increased from 89 to 99.25%, 91-99%, 90.8-97%, 83-95% and 78-96% when the crystal size of the support varied from 3 to 20 nm, respectively. The nitrogen and aromatic conversions were also increased in the range of 23-45 wt.%. It was found that the {gamma} phase reached a higher catalytic performance than the {eta} phase. The NiMo catalysts synthesized in a basic medium showed a better catalytic performance than that obtained with those prepared in acid solutions. The significance of the kinetic data to compare the catalysts is discussed. The maximum value of the catalytic activity was reached with the catalysts with the smallest particle sizes. (author)

Recovery of molybdenum in froth flotation

International Nuclear Information System (INIS)

Parlman, R.M.; Bresson, C.R.

1981-01-01

Beta-mercaptoethanol has been found to be an effective suppressant for such minerals as copper, iron and lead in a molybdenum sulfide ore froth flotation operation. The recovery process and a suppressant utilizing said compound are claimed

New insides in the characterization of HDS industrial catalysts by HAADF-STEM

Science.gov (United States)

Del Angel, Paz; Ponce, Arturo; Arellano, Josefina; Yacaman, Miguel J.; Hernandez-Pichardo, Martha; Montoya, J. Ascencion; Escobar, Jose

2015-03-01

Hydrodesulfurization (HDS) catalysts are of great importance in the petroleum industry. Transition metal sulphides catalysts of Ni(Co)Mo(W)/Al2O3 are widely used for hydrotreating reactions, like hydrodenitrogenation and HDS. One of the main issue in these catalysts is to understand the mechanism of the reaction, where MoS2 plays the most important role in the catalytic activity. We studied an industrial NiMo/Alumina sulfide catalyst highly active by using aberration-corrected HAADF-STEM techniques. The used catalysts was a state-of- the art commercial nickel-molybdenum alumina-supported formulation, including organic agent modifier. This type of material belongs to a novel family of catalysts specially designed for ultra-low sulfur production from straight-run gas oil (SRGO), cycle oil, coker gas oil, or their combinations at operating conditions of commercial interest in hydrotreating units at industrial scale. Aberration corrected HAADF-STEM allowed to observe the nanostructure and location of MoS2 and his interaction with the alumina. The results indicate that the MoS2 is highly dispersed on the alumina, however the location of Ni is one of the task of this kind of catalyst.

The Synthesis and Electrocatalytic Activities of Molybdenum Sulfide for Hydrogen Evolution Reaction

KAUST Repository

Li, Zhengxing

2014-07-01

In the context of the future hydrogen economy, effective production of hydrogen (H2) from readily available and sustainable resources is of crucial importance. Hydrogen generation via water splitting by solar energy or electricity has attracted great attention in recent years. In comparison with photocatalytic water-splitting directly using solar light, which is ideal but the relevant technologies are not yet mature, electrolysis of water with catalyst is more practical at the current stage. The Pt-group noble metals are the most effective electrocatalysts for hydrogen evolution reaction (HER) from water, but their high costs limit their applications. Due to the earth-abundance and low price, MoS2 is expected to be a good alternative of the Pt-group metals for HER. Plenty of researches have been conducted for improving the HER activities of MoS2 by optimizing its synthesis method. However, it remains challenging to prepare MoS2 catalysts with high and controllable activity, and more investigations are still needed to better understand the structure-performance correlation in this system. In this thesis, we report a new strategy for fabricating MoS2 eletrocatalysts which gives rise to much improved HER performance and allows us to tune the electrocatalytic activity by varying the preparation conditions. Specifically, we sulfurized molybdenum oxide on the surface of a Ti foil electrode via a facile chemical vapor deposition (CVD) method, and directly used the electrode for HER testing. Depending on the CVD temperature, the MoO2-MoS2 nanocomposites show different HER activities. Under the optimal synthesis condition (400ºC), the resulting catalyst exhibited excellent HER activity: an onset potential (overpotential) of 0.095 V versus RHE and the Tafel slope of 40 mv/dec. Such a performance exceeds those of most reported MoS2 based HER electrocatalysts. We demonstrated that the CVD temperature has significant influence on the catalysts in crystallinity degree, particle

Molybdenum isotope fractionation and speciation in a euxinic lake—Testing ways to discern isotope fractionation processes in a sulfidic setting

Energy Technology Data Exchange (ETDEWEB)

Dahl, Tais W.; Wirth, Stefanie B.

2017-06-01

The molybdenum (Mo) isotope composition in euxinic shales has been used as a proxy for the global distribution of anoxic conditions in ancient oceans, and since more recently also as a proxy for sulfide concentrations in depositional environments. However, there is currently no way to distinguish isotope fractionation at low bottom water sulfide concentrations in ‘local’ basins from ‘global’ secular isotope variations associated with changing seawater composition. This uncertainty is challenging the use of Mo isotopes for paleoceanographic reconstructions. To explore this further, we present new data from sediments deposited over the past ~ 9800 years in one of the best studied euxinic localities in the world: Lake Cadagno in Switzerland. The sample set allows us to test ways to discern isotope fractionation processes at play in a highly restricted euxinic basin. Most of our drill core samples (n = 18) show high δ98Mo values similar to previously studied shallow sediments, indicative of quantitative Mo removal from the water column (Dahl et al. 2010a). However, a few samples (n = 3) deposited between about 1200 and 3400 years ago carry low δ98Mo values and have been isotopically fractionated in the lake. Sedimentological and geochemical characterizations show that these δ98Mo-fractionated sediments formed during times of frequent injection of O2- and sediment-rich river water into the deep sulfidic water column. A positive correlation between δ98Mo and sedimentary Mo contents suggests that isotope fractionation occurred during times of non-quantitative Mo removal, although Mn-oxide cycling at the chemocline might also contribute a subordinate proportion of (98Mo-depleted) molybdenum into the sulfidic zone. Sedimentary Mo/U enrichments relative to oxic lake water further supports the hypothesis that a particulate Mo shuttle was most efficient during times of quantitative Mo removal. Therefore, periods with inefficient Mo capture are ascribed to

Structure and coke preventing characteristics of Ca-Ni-Mo/Al sub 2 O sub 3 catalyst for hydrogenation of brown coal liquid bottoms. Kattan ekikaabura suisokayo Ca-Ni-Mo/Al sub 2 O sub 3 shokubai no kozo to tansoshitsu seisei yokusei sayo

Energy Technology Data Exchange (ETDEWEB)

Kimura, T. (Cosmo Oil Co. Ltd., Tokyo (Japan)); Kaneko, T.; Kageyama, Y. (Mitsubishi Kasei Corp., Tokyo (Japan). Research Center); Kawai, S. (Nippon Brown Coal Liquefaction Co. Ltd., Tokyo (Japan))

1990-09-01

Operating a 50 t/d fixed bed pilot plant, hydroprocessing of de-ashed coal liquid bottoms (DAO) derived from Victorial Brown coal liquefaction has been carried out in Australia using a newly developed Ca-Ni-Mo/Al {sub 2} O {sub 3} catalyst. This catalyst has a great advantage compared with conventional molybdenum catalysts in that there is less coke formation using this catalyst as indicated by 5,000 h runs in a 0.1 t/d bench scale plant. In this paper, the catalyst active center and the role of Ca in the Ca-Ni-Mo/Al {sub 2} O {sub 3} catalyst were analyzed using Raman, TPS-XPS, EXAFS and AES methods. Molybdenum is loaded as CaMoO {sub 4} and X-ray diffraction data. But the oxide is changed to MoS {sub 2} after sulfiding treatment. Data of the Mo-S bond obtained from EXAFS analysis indicated that MoS {sub 2} has a tendency to pile up on the Ca-Ni-Mo/Al {sub 2} O {sub 3} catalyst. 20 refs., 12 figs., 5 tabs.

One-Pot Catalyst-Free Synthesis of β- and γ-Hydroxy Sulfides using Diaryliodonium Salts and Microwave Irradiation

Science.gov (United States)

A facile one-pot high-yield protocol is described for the preparation of β- and γ-hydroxy sulfides directly from diaryliodonium salts, potassium thiocyanate, and ethane-1,2-diol (ethylene glycol)/propane-1,3-diol (β-propylene glycol) without the need for any additional catalyst o...

Synthesis and characterization of molybdenum catalysts supported on γ-Al2O3-CeO2 composite oxides

International Nuclear Information System (INIS)

Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri

2012-01-01

The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on γ-Al 2 O 3 and γ-Al 2 O 3 -CeO 2 mixed oxides with varying loading of CeO 2 (5, 10, 15, 20 wt% with respect to γ-Al 2 O 3 ) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO 2 into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.

Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

Directory of Open Access Journals (Sweden)

Eduardo Santillan-Jimenez

2015-03-01

Full Text Available Molybdenum carbide was supported on three types of carbon support—activated carbon; multi-walled carbon nanotubes; and carbon nanofibers—using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases were obtained on carbon nanofibers and, in some cases, on carbon nanotubes. When the resulting catalysts were tested in the hydrodeoxygenation (HDO of guaiacol in dodecane, catechol and phenol were obtained as the main products, although in some instances significant amounts of cyclohexane were produced. The observation of catechol in all reaction mixtures suggests that guaiacol was converted into phenol via sequential demethylation and HDO, although the simultaneous occurrence of a direct demethoxylation pathway cannot be discounted. Catalysts based on carbon nanofibers generally afforded the highest yields of phenol; notably, the only crystalline phase detected in these samples was Mo2C or Mo2C-ζ, suggesting that crystalline Mo2C is particularly selective to phenol. At 350 °C, carbon nanofiber supported Mo2C afforded near quantitative guaiacol conversion, the selectivity to phenol approaching 50%. When guaiacol HDO was performed in the presence of acetic acid and furfural, guaiacol conversion decreased, although the selectivity to both catechol and phenol was increased.

NiMo-sulfide supported on activated carbon to produce renewable diesel

Directory of Open Access Journals (Sweden)

Nancy Y Acelas

2017-03-01

Full Text Available Due to their weak polarity and large surface area, activated carbon supports have the potential to enhance the dispersion of metal-sulfides. It is expected that the absence of a strong metal-support interaction can result in the formation of a very active and stable Ni-Mo-S phase. In this study, catalysts with different amounts of nickel and molybdenum supported on a commercial activated carbon were prepared by a co-impregnation method and characterized by BET, XRF, and SEM techniques. The catalytic activity for hydroprocessing of Jatropha oil was evaluated in a batch reactor, and the composition of the liquid and gaseous products were determined. Results showed that gaseous products are mainly composed of high amounts of propane and small amounts of other light hydrocarbons (C1 to C5. Liquid hydrocarbon products consisted of a mixture containing mainly n-paraffins of C15-C18 and some oxygenated compounds. The catalysts with a mass fraction of 3 % Ni, 15 % Mo (Ni3Mo15/AC presented the highest selectivity toward C17-C18 hydrocarbons, with a product distribution similar to a commercial alumina-supported Ni-Mo-S catalyst.

Hydrophilic cobalt sulfide nanosheets as a bifunctional catalyst for oxygen and hydrogen evolution in electrolysis of alkaline aqueous solution.

Science.gov (United States)

Zhu, Mingchao; Zhang, Zhongyi; Zhang, Hu; Zhang, Hui; Zhang, Xiaodong; Zhang, Lixue; Wang, Shicai

2018-01-01

Hydrophilic medium and precursors were used to synthesize a hydrophilic electro-catalyst for overall water splitting. The cobalt sulfide (Co 3 S 4 ) catalyst exhibits a layered nanosheet structure with a hydrophilic surface, which can facilitate the diffusion of aqueous substrates into the electrode pores and towards the active sites. The Co 3 S 4 catalyst shows excellent bifunctional catalytic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solution. The assembled water electrolyzer based on Co 3 S 4 exhibits better performance and stability than that of Pt/C-RuO 2 catalyst. Thereforce the hydrophilic Co 3 S 4 is a highly promising bifunctional catalyst for the overall water splitting reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

The Comparison of Co, Ni, Mo, CoMo and NiMo Sulfided Catalysts in Rapeseed Oil Hydrodeoxygenation.

Czech Academy of Sciences Publication Activity Database

Kaluža, Luděk; Kubička, D.

2017-01-01

Roč. 122, č. 1 (2017), s. 333-341 ISSN 1878-5190 R&D Projects: GA ČR(CZ) GA17-22490S Institutional support: RVO:67985858 Keywords : triolein hydrodeoxygenation scheme * rapeseed oil * sulfide catalysts Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.264, year: 2016

Second row transition metal sulfides for the hydrotreatment of coal-derived naphtha. 1. Catalyst preparation, characterization and comparison of rate of simultaneous removal of total sulfur, nitrogen and oxygen

Energy Technology Data Exchange (ETDEWEB)

Raje, A.P.; Liaw, S.-J.; Srinivasan, R.; Davis, B.H. [University of Kentucky, Lexington, KY (United States). Center for Applied Energy Research

1997-03-13

Naphtha derived from an Illinois No. 6 coal contains appreciable quantities of sulfur-, nitrogen- and oxygen-containing compounds. The hydrotreatment of this naphtha was evaluated over unsupported transition metal sulfide catalysts (Ru, Rh, Mo, Pd, Zr, Mb). The catalysts were prepared by a room temperature precipitation reaction. Surface areas, crystalline phase and particle size distributions were determined by Brunauer-Emmet-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. A comparison of average particle sizes calculated from these three techniques has enable the understanding of the morphology of the transition metal sulfides. The catalysts exhibit a so-called volcano plot for the HDS of dibenzothiophene. Similar so-called volcano plots are also exhibited for the simultaneous hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and the hydrodeoxygenation (HDO) of the coal-derived naphtha containing a mixture of heteroatoms. The order of reactivity of the transition metal catalysts is the same for all three of the processes. Ruthenium sulfide is the most active catalyst for HDS, HDN and HDO of the coal-derived naphtha. 22 refs., 3 figs., 4 tabs.

Gel Fabrication of Molybdenum “Beads”

Energy Technology Data Exchange (ETDEWEB)

Lowden, Richard Andrew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Armstrong, Beth L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Cooley, Kevin M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

2016-11-01

Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of ⁹⁹Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however, the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.

Multifunctional Interlayer Based on Molybdenum Diphosphide Catalyst and Carbon Nanotube Film for Lithium-Sulfur Batteries.

Science.gov (United States)

Luo, Yufeng; Luo, Nannan; Kong, Weibang; Wu, Hengcai; Wang, Ke; Fan, Shoushan; Duan, Wenhui; Wang, Jiaping

2018-02-01

A multifunctional interlayer, composed of molybdenum diphosphide (MoP 2 ) nanoparticles and a carbon nanotube (CNT) film, is introduced into a lithium-sulfur (Li-S) battery system to suppress polysulfide migration. Molybdenum diphosphide acts as the catalyst and can capture polysulfides and improve the polysulfide conversion activity during the discharge/charge processes. The CNT film acts as a conductive skeleton to support the MoP 2 nanoparticles and to ensure their uniform distribution. The CNT film physically hinders polysulfide migration, acts as a current collector, and provides abundant electron pathways. The Li-S battery containing the multifunctional MoP 2 /CNT interlayer exhibits excellent electrochemical performance. It delivers a reversible specific capacity of 905 mA h g -1 over 100 cycles at 0.2 C, with a capacity decay of 0.152% per cycle. These results suggest the introduction of the multifunctional CNT/MoP 2 interlayer as an effective and practical method for producing high-performance Li-S batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The active component of vanadium-molybdenum catalysts for the oxidation of acrolein to acrylic acid

International Nuclear Information System (INIS)

Andrushkevich, T.V.; Kuznetsova, T.G.

1986-01-01

The catalytic properties of the vanadium-molybdenum oxide system were investigated in the oxidation of acrolein to acrylic acid. The active component of the catalyst is the compound VMo 3 O 11 , the maximum amount of which is observed at a content of 7-15 mole% V 2 O 4 . The compound VMo 3 O 11 is formed in the thermodecomposition of silicomolybdovanadium heteropoly acids or isopoly compounds, reduced with respect to vanadium, and contains V 4+ and Mo 6+ . The optimum treatment for the formation of this compound is treatment in the reaction mixture at 400 degrees C

Understanding hydrodenitrogenation on novel unsupported sulfide Mo-W-Ni catalysis

Energy Technology Data Exchange (ETDEWEB)

Hein, J.; Hrabar, A.; Gutierrez, O.Y.; Lercher, J.A. [Technische Univ. Muenchen (Germany). Catalysis Research Center

2011-07-01

WNi, NiMo and Mo-W-Ni unsupported catalysts were synthesized, characterized and tested with respect to their hydrodenitrogenation properties using o-propylaniline as test reactant. The bimetallic oxide precursors are crystalline metallates, whereas the trimetallic materials are amorphous. In the sulfide form, the catalysts are mixtures of agglomerated Mo(W)S{sub 2} and Ni sulfides. The performance of all catalysts is similar, suggesting the same nature of active sites regardless the composition. Due to the lack of correlation between activity and density of coordinatively unsaturated sites of the catalysts, two kinds of active sites are proposed, i.e. coordinatively unsaturated sites and electron rich sites at the edges of the sulfides. (orig.)

Upgrading pyrolysis bio-oil through hydrodeoxygenation (HDO) using non-sulfided Fe-Co/SiO2 catalyst

International Nuclear Information System (INIS)

Cheng, Shouyun; Wei, Lin; Julson, James; Rabnawaz, Muhammad

2017-01-01

Highlights: • Fe-Co/SiO 2 catalyst with medium acidity was more effective for bio-oil upgrading. • Co-loading of Fe and Co on SiO 2 support improved catalyst performance. • Catalyst showing the best catalytic activity had a Fe/Co mole ratio of 1. • Biofuel produced by Fe-Co(1)/SiO 2 had the higher hydrocarbons content at 22.44%. • The mechanism of bio-oil HDO on Fe-Co/SiO 2 catalysts is proposed. - Abstract: Hydrodeoxygenation (HDO) is an effective route to upgrade bio-oil to hydrocarbon bio-oil, but the development of efficient catalysts for bio-oil HDO still remains a challenge. In this study, non-sulfided Fe-Co/SiO 2 catalysts were used to upgrade bio-oil using HDO. A series of Fe-Co/SiO 2 catalysts with different Fe/Co mole ratios were prepared, characterized and evaluated. The Fe and/or Co loading did not change SiO 2 crystalline structure. The Fe and/or Co metals increased the amount and strength of Fe-Co/SiO 2 catalyst acidity. Physicochemical properties of upgraded bio-oils produced using Fe-Co/SiO 2 catalysts such as water content, total acid number, viscosity and higher heating values improved in comparison to raw bio-oil. Bimetallic Fe-Co/SiO 2 catalysts resulted in better HDO performance than monometallic Fe/SiO 2 or Co/SiO 2 catalysts. This was due to the synergistic effect of Fe and Co occurring on the SiO 2 support. Fe-Co/SiO 2 catalyst having medium amount of acidity was more effective for bio-oil upgrading. The highest hydrocarbons content produced using Fe-Co(1)/SiO 2 catalyst was 22.44%. The mechanism of bio-oil HDO on Fe-Co/SiO 2 catalysts is proposed.

Low-crystallinity molybdenum sulfide nanosheets assembled on carbon nanotubes for long-life lithium storage: Unusual electrochemical behaviors and ascending capacities

Energy Technology Data Exchange (ETDEWEB)

Li, Xiaodan, E-mail: xiaodan_li@yeah.net [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Wu, Gaoxiang, E-mail: wgxjimmy@126.com [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Chen, Jiewei, E-mail: kzscjw@126.com [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Li, Meicheng, E-mail: mcli@ncepu.edu.cn [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Chongqing Materials Research Institute, Chongqing 400707 (China); Li, Wei, E-mail: wei.li@inl.int [International Iberian Nanotechnology Laboratory (INL), Braga 4715-330 (Portugal); Wang, Tianyue, E-mail: 1355796015@qq.com [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Jiang, Bing, E-mail: BingJiang@ncepu.edu.cn [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); He, Yue, E-mail: 947667748@qq.com [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China ElectricPower University, Beijing, 102206 (China); Mai, Liqiang, E-mail: mlq518@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2017-01-15

Highlights: • Low-crystallinity molybdenum sulfide coated on carbon nanotubes were synthesized. • This anode material has unusual electrochemical behaviors compared to typical MoS{sub 2}. • It exhibits noticable ascending trends in capacity and superior rate performance. • The ascending performance can effectively extend the circulation life of batteries. - Abstract: Low-crystallinity molybdenum sulfide (LCMS, Mo:S = 1:2.75) nanosheets synthesized by a facile and low temperature solvothermal method is now reported. The as-prepared LCMS anode material is composited of MoS{sub 2} layers mixed with amorphous MoS{sub 3}, which leads to an unusual electrochemical process for lithium storage compared to typical MoS{sub 2} anode. The existence of MoS{sub 3} and Mo (VI) provide strong adsorption and binding sites for polar polysulphides, which compels abundant sulfur to turn into new-formed MoS{sub 3} rather than diffuse into electrolyte. To fully utilize this novel electrochemical process, LCMS is decorated on carbon nanotubes, obtaining well-dispersed CNTs@LCMS. As electrode material for lithium storage, CNTs@LCMS exhibits a noticable ascending trend in capacity from 820 mA h g{sup −1} to 1350 mA h g{sup −1} at 100 mA g{sup −1} during 130 cycles. The persistent ascending capacity is ascribed to the increasing lithium storage caused by new-formed MoS{sub 3}, combined with the reduced volume change benifiting from well-dispersed CNTs@LCMS. Furthermore, the ascending performance is proved to be able to effectively extend the circulation life (up to 200%) for lithium-ion batteries by mathematical modeling and calculation. Accordingly, the CNTs@LCMS composite is a promising anode material for long-life lithium-ion batteries.

Basic study of catalyst aging in the H-coal process

Energy Technology Data Exchange (ETDEWEB)

Cable, T.L.; Massoth, F.E.; Thomas, M.G.

1985-04-01

Samples of CoMo/Al/sub 2/O/sub 3/ catalysts used in an H-coal process demonstration run were studied to determine causes of catalyst deactivation. Physical and surface properties of the aged and regenerated catalysts were examined. Model compounds were used to assess four catalyst activity functions, viz., hydrodesulfurization (HDS), hydrogenation, cracking and hydrodeoxygenation (HDO). Other tests were performed to study the effects of coke and metals separately on the four catalyst activity functions. Catalyst coke content and metal deposits first increased rapidly, then more gradually with exposure time in the process run. Surface area and pore volume markedly decreased with exposure time. Catalyst activities of aged catalysts showed a rapid decline with exposure time. One-day exposure to coal resulted in significant losses in HDS and hydrogenation activities and nearly complete loss in cracking and HDO activities. Although metal deposits caused some permanent catalyst deactivation, coke had a much greater effect. Regenerated catalysts showed less recovery of catalytic activity as processing time increased. These results agreed well with product inspections from the process run. Oxygen chemisorption on aged-regenerated catalysts decreased with catalyst exposure time, indicating a significant loss of active sites. However, ESCA results showed no evidence of extensive sintering of the active MoS/sub 2/ phase. Permanent deactivation of the longer-time exposed catalysts can be ascribed, at least partly, to lateral growth of the active molybdenum sulfide phase. In addition, some loss in cobalt promotion occurred early in the process, which may account for the rapid loss in HDS and HDO activity in regenerated catalysts. 24 references.

Effects of H2S and process conditions in the synthesis of mixed alcohols from syngas over alkali promoted cobalt-molybdenum sulfide

DEFF Research Database (Denmark)

Christensen, Jakob Munkholt; Mortensen, Peter Mølgaard; Trane, Rasmus

2009-01-01

pressures of H2 and CO are also investigated. With or without H2S in the feed the pre-sulfided catalyst requires an initiation period to reach a stabilized behavior, but the duration of this period depends upon the H2S level. Operation with a feed containing more than 103 ppmv H2S leads to a fairly rapid...... coverage and low hydrogen coverage. Hydrogen sulfide in the syngas feed generally promotes chain growth for both alcohols and hydrocarbons, but lowers the alcohol selectivity by enhancing the hydrocarbon formation. The highest alcohol productivity reached in these investigations was 0.276 g/g cat...

Recent situation and future of molybdenum mineral resources; Molybdenum shigen no genjo to shorai

Energy Technology Data Exchange (ETDEWEB)

Ono, K.; Nishiyama, T. [Kyoto University, Kyoto (Japan)

1997-05-05

Molybdenum is produced mainly from molybdenite, and the majority of this ore is exploited from the porphyry deposit. The reserve is estimated at 5.5-million ton. A total of 118-thousand ton was produced across the world in 1995, in the U.S., China, Chile, and Canada, the countries named in the order of quantities they exploited. Molybdenite is first refined by flotation for the production of a sulphide. It is subjected to oxidizing roasting for conversion into crude molybdenum trioxide, which is next subjected to extraction in warmed-up aqueous ammonia and then to evaporation for the crystallization of ammonium paramolybdate. The crystals are baked for conversion into molybdenum trioxide of the ordinary purity, to be further processed into ferromolybdenum, molybdenum compounds, molybdenum powder, etc. In view of the magnitude of demand, the metal is used mostly for the manufacture of special steels and special alloys. The demand for this metal, though small in size, involves important articles, such as line materials for semiconductors in the power industry, catalysts in the chemical industry, and lubricants. Japan`s stockpile includes molybdenum, but the U.S. has been stockpiling none since 1977. 9 refs., 4 figs., 1 tab.

Molybdenum/alkali metal/ethylene glycol complexes useful as epoxidation catalysts

International Nuclear Information System (INIS)

Marquis, E.T.; Sanderson, J.R.; Keating, K.P.

1987-01-01

This patent describes a clear, storage stable solution of a molybdenum/alkali metal/ethylene glycol complex in ethylene glycol made by the process comprising: reacting at an elevated temperature between about 25 0 and 150 0 C a solid ammonium molybdate or a hydrate thereof and a solid alkali metal molybdate or a hydrate thereof with ethylene glycol, such that the ratio of moles of ethylene glycol to total gram atoms of molybdenum in the molybdates ranges from about 7:10 to 10:1, and the ratio of gram atoms of molybdenum in the ammonium molybdate or hydrate thereof to gram atoms of molybdenum in the alkali metal molybdate is from about 1:1 to about 20:1 to thereby provide a reaction product composed of a solution of an alkali metal-containing complex of molybdenum, alkali metal and ethylene glycol and by-products, including water, in the ethylene glycol and subsequently stripping the solution at a reduced pressure to remove from about 5 to about 25% of the reaction product, as distillate, to thereby provide a storage stable solution of the complex in the ethylene glycol having a molybdenum content of about 6 wt. % to about 20 wt. %, a water concentration of about 0.1 wt. % to about 6 wt. % and an acid number of more than about 60

Catalyst Deactivation and Regeneration Processes in Biogas Tri-Reforming Process. The Effect of Hydrogen Sulfide Addition

Directory of Open Access Journals (Sweden)

Urko Izquierdo

2018-01-01

Full Text Available This work studies Ni-based catalyst deactivation and regeneration processes in the presence of H2S under a biogas tri-reforming process for hydrogen production, which is an energy vector of great interest. 25 ppm of hydrogen sulfide were continuously added to the system in order to provoke an observable catalyst deactivation, and once fully deactivated two different regeneration processes were studied: a self-regeneration and a regeneration by low temperature oxidation. For that purpose, several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on alumina modified with CeO2 and ZrO2 were used as well as a commercial Katalco 57-5 for comparison purposes. Ni/Ce-Al2O3 and Ni/Ce-Zr-Al2O3 catalysts almost recovered their initial activity. For these catalysts, after the regeneration under oxidative conditions at low temperature, the CO2 conversions achieved—79.5% and 86.9%, respectively—were significantly higher than the ones obtained before sulfur poisoning—66.7% and 45.2%, respectively. This effect could be attributed to the support modification with CeO2 and the higher selectivity achieved for the Reverse Water-Gas-Shift (rWGS reaction after catalysts deactivation. As expected, the bimetallic Rh-Ni/Ce-Al2O3 catalyst showed higher resistance to deactivation and its sulfur poisoning seems to be reversible. In the case of the commercial and Ni/Zr-Al2O3 catalysts, they did not recover their activity.

Scaling Relations for Adsorption Energies on Doped Molybdenum Phosphide Surfaces

International Nuclear Information System (INIS)

Fields, Meredith; Tsai, Charlie; Chen, Leanne D.; Abild-Pedersen, Frank; Nørskov, Jens K.; Chan, Karen

2017-01-01

Molybdenum phosphide (MoP), a well-documented catalyst for applications ranging from hydrotreating reactions to electrochemical hydrogen evolution, has yet to be mapped from a more fundamental perspective, particularly in the context of transition-metal scaling relations. In this work, we use periodic density functional theory to extend linear scaling arguments to doped MoP surfaces and understand the behavior of the phosphorus active site. The derived linear relationships for hydrogenated C, N, and O species on a variety of doped surfaces suggest that phosphorus experiences a shift in preferred bond order depending on the degree of hydrogen substitution on the adsorbate molecule. This shift in phosphorus hybridization, dependent on the bond order of the adsorbate to the surface, can result in selective bond weakening or strengthening of chemically similar species. As a result, we discuss how this behavior deviates from transition-metal, sulfide, carbide, and nitride scaling relations, and we discuss potential applications in the context of electrochemical reduction reactions.

A Non-sulfided flower-like Ni-PTA Catalyst that Enhances the Hydrotreatment Efficiency of Plant Oil to Produce Green Diesel

Science.gov (United States)

Liu, Jing; Chen, Pan; Deng, Lihong; He, Jing; Wang, Luying; Rong, Long; Lei, Jiandu

2015-01-01

The development of a novel non-sulfided catalyst with high activity for the hydrotreatment processing of plant oils, is of high interest as a way to improve the efficient production of renewable diesel. To attempt to develop such a catalyst, we first synthesized a high activity flower-like Ni-PTA catalyst used in the hydrotreatment processes of plant oils. The obtained catalyst was characterized with SEM, EDX, HRTEM, BET, XRD, H2-TPR, XPS and TGA. A probable formation mechanism of flower-like Ni(OH)2 is proposed on the basis of a range of contrasting experiments. The results of GC showed that the conversion yield of Jatropha oil was 98.95%, and the selectivity of C11-C18 alkanes was 70.93% at 360 °C, 3 MPa, and 15 h−1. The activity of this flower-like Ni-PTA catalyst was more than 15 times higher than those of the conventional Ni-PTA/Al2O3 catalysts. Additionally, the flower-like Ni-PTA catalyst exhibited good stability during the process of plant oil hydrotreatment. PMID:26503896

REACTION PRODUCTS AND CORROSION OF MOLYBDENUM ELECTRODE IN GLASS MELT CONTAINING ANTIMONY OXIDES AND SODIUM SULFATE

Directory of Open Access Journals (Sweden)

JIŘÍ MATĚJ

2012-09-01

Full Text Available The products on the interface of a molybdenum electrode and glass melt were investigated primarily at 1400°C in three model glass melts without ingredients, with 1 % Sb2O3 and with 1 % Sb2O3 and 0.5 % SO3 (wt. %, both under and without load by alternating current. Corrosion of the molybdenum electrode in glass melt without AC load is higher by one order of magnitude if antimony oxides are present. The corrosion continues to increase if sulfate is present in addition to antimony oxides. Isolated antimony droplets largely occur on the electrode-glass melt interface, and numerous droplets are also dissipated in the surrounding glass if only antimony oxides are present in the glass melt. A comparatively continuous layer of antimony occurs on the interface if SO3 is also present, antimony being always in contact with molybdenum sulfide. Almost no antimony droplets are dissipated in the glass melt. The total amount of precipitated antimony also increases. The presence of sulfide on the interface likely facilitates antimony precipitation. The reaction of molybdenum with antimony oxides is inhibited in sites covered by an antimony layer. The composition of sulfide layers formed at 1400°C approximates that of Mo2S3. At 1100°C, the sulfide composition approximates that of MoS4. Corrosion multiplies in the glass melt without additions through the effect of AC current, most molybdenum being separated in the form of metallic particles. Corrosion also increases in the glass melt containing antimony oxides. This is due to increased corrosion in the neighborhood of the separated antimony droplets. This mechanism also results in the loosening of molybdenum particles. The amount of precipitated antimony also increases through the effect of the AC current. AC exerts no appreciable effect on either corrosion, the character of the electrode-glass interface, or antimony precipitation in the glass melt containing SO3.

Oxidation of methyl heterocyclic compounds on vanadium oxide catalysts

International Nuclear Information System (INIS)

Shimanskaya, M.V.; Lejtis, L.A.; Iovel', I.G.; Gol'dberg, Yu.Sh.; Skolmejstere, R.A.; Golender, L.O.

1985-01-01

Data on vapor-phase oxidation of methyl derivatives of thiophene, Δ 2 - thiazo line, pyridine, pyrazine and pyramidine on oxide vanadium-molybdenum catalysts to corresponding heterylaldehydes are generalized. The dependence of catalytic properties of oxide vanadium-molybdenum systems in oxidation reactions of methylheterocyclic compounds on V:Mo ratio in the catalyst is revealed. It is shown that heterocyclic compounds are coordinated by a heteroatom on Lewis centres of V-Mo-O-catalyst primarily with partially reduced vanadium ions

Nanostructured metal sulfides for energy storage

Science.gov (United States)

Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

2014-08-01

Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

Sulfur deactivation of fatty ester hydrogenolysis catalysts

Energy Technology Data Exchange (ETDEWEB)

Brands, D.S.; U-A-Sai, G.; Poels, E.K.; Bliek, A. [Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering

1999-08-15

Trace organosulfur compounds present as natural impurities in oleochemical feedstocks may lead to activation of copper-containing catalysts applied for hydrogenolysis of esters toward fatty alcohols. In this paper, the sulfur deactivation of Cu/SiO{sub 2} and Cu/ZnO/SiO{sub 2} catalysts was studied in the liquid-phase hydrogenolysis of methyl palmitate. The rate of deactivation is fast and increases as a function of the sulfur-containing compound present: octadecanethiol {approx} dihexadecyl disulfide < benzyl isothiocyanate < methyl p-toluene sulfonate < dihexadecyl sulfide < dibenzothiophene. The rapid deactivation is caused by the fact that sulfur is quantitatively removed from the reaction mixture and because mainly surface sulfides are formed under hydrogenolysis conditions. The life time of a zinc-promoted catalyst is up to two times higher than that of the Cu/SiO{sub 2} catalyst, most likely due to zinc surface sulfide formation. The maximum sulfur coverage obtained after full catalyst deactivation with dibenzothiophene and dihexadecyl sulfide--the sulfur compounds that cause the fastest deactivation--may be as low as 0.07. This is due to the fact that decomposition of these compounds as well as the hydrogenolysis reaction itself proceeds on ensembles of copper atoms. Catalyst regeneration studies reveal that activity cannot be regained by reduction or combined oxidation/reduction treatments. XRD, TPR, and TPO results confirm that no distinct bulk copper or zinc sulfide or sulfate phases are present.

Synthesis and characterization of molybdenum catalysts supported on {gamma}-Al{sub 2}O{sub 3}-CeO{sub 2} composite oxides

Energy Technology Data Exchange (ETDEWEB)

Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri [Department of Chemical EngineeringUniversiti Teknologi PETRONAS Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Department of Chemical EngineeringUniversiti Teknologi PETRONAS Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2012-09-26

The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on {gamma}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3}-CeO{sub 2} mixed oxides with varying loading of CeO{sub 2} (5, 10, 15, 20 wt% with respect to {gamma}-Al{sub 2}O{sub 3}) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO{sub 2} into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.

Combined spectroscopy and microscopy of supported MoS2 nanoparticles

DEFF Research Database (Denmark)

Nielsen, Jane Hvolbæk; Bech, Lone; Nielsen, Kenneth

2009-01-01

Supported molybdenum-sulfide nanoparticles are known catalysts for petroleum hydrodesulfurization as well as for electrochemical hydrogen evolution. In this study, we investigate molybdenum-sulfide nanoparticles supported on Au(111) using X-ray photoelectron spectroscopy (XPS) and scanning...... tunneling microscopy (STM), aiming to correlate spectroscopically determined chemical states with atomically resolved nanostructure. The results of this study allow us to conclude the following: (1) the XPS results from our model system are in good agreement with previously published results on supported Mo...

Regeneration of Hydrotreating and FCC Catalysts

Energy Technology Data Exchange (ETDEWEB)

CM Wai; JG Frye; JL Fulton; LE Bowman; LJ Silva; MA Gerber

1999-09-30

-earth exchanged Y zeolite in a silica-alumina matrix. X-ray fluorescence analyses showed that the rare earths used in preparing the catalysts were a mixture of lanthanum and cerium. Antimony found in the spent catalyst was added during operation of the FCC unit as a way to suppress the adverse effects of deposited nickel. The fresh HDS samples consisted of sulfided nickel and molybdenum on an alumina support. The spent catalyst showed nearly 10% vanadium on the catalyst and a modest increase in nickel and sulfur on the catalyst as a result of operations. Hydrocracking catalysts were not available for this study.

Efficient epoxidation of propene using molecular catalysts

DEFF Research Database (Denmark)

Markovits, Iulius I. E.; Anthofer, Michael H.; Kolding, Helene

2014-01-01

The epoxidation of propene is performed in homogeneous phase using various molecular catalysts and H2O2 or tert-butyl hydroperoxide as oxidants. A comparison between some molybdenum catalysts and methyltrioxorhenium (MTO) shows that the well known Re catalyst is the best among the examined...

A peroxotungstate-ionic liquid brush assembly: an efficient and reusable catalyst for selectively oxidizing sulfides with aqueous H{sub 2}O{sub 2} solution in neat water

Energy Technology Data Exchange (ETDEWEB)

Shi, Xianying; Ma, Wenjuan; Ou, Hui; Han, Xiaoyan; Lu, Congmin; Chen, Yan; Wei, Junfa, E-mail: shixy@snnu.edu.cn, E-mail: weijf@snnu.edu.cn [School of Chemistry and Chemical Engineering, Shaanxi Normal University and Key Laboratory for Macromolecular Science of Shaanxi Province, Xian (China)

2012-08-15

An efficient and reusable heterogeneous catalytic assembly of peroxotungstate held in a ionic liquid (IL) brush was synthesized and an environmentally-friendly procedure was developed for selective oxidation of sulfides at room temperature using 30 wt.% hydrogen peroxide as the terminal oxidant and water as a sole solvent. No organic co-solvent or other additive was needed. A 1.5-2.0 mol% (based on W atom) loading catalyst was found to be sufficient for a smooth and clean reaction. Both aliphatic and aromatic sulfides were efficiently and selectively transformed into their respective sulfoxides or sulfones by simply controlling of equivalents of hydrogen peroxide. In addition to the high catalytic activity, the catalyst exhibits excellent chemoselectivity. Sensitive functional groups, such as double bond and hydroxyl, remained under the oxidation conditions the reaction even with an excess hydrogen peroxide. The catalyst was easily recovered (via simple filtration) and reused at least eight times without a noticeable loss of activity. (author)

Studies of Deactivation of Methanol to Formaldehyde Selective Oxidation Catalyst

DEFF Research Database (Denmark)

Raun, Kristian Viegaard; Schumann, Max; Høj, Martin

Formaldehyde (CH2O) may be synthesized industrially by selective oxidation of methanol over an iron-molybdate (Fe-Mo) oxide catalyst according to: CH3OH + ½O2 →CH2O + H2O. The reaction is normally carried out in a multitubular reactor with excess of air at 250-400 °C (yield = 90-95 %), known...... the activity of the catalyst [2]. Pure MoO3 in itself has low activity. Literature from the last decades agrees that the major reason for the deactivation is loss of molybdenum from the catalyst. Molybdenum forms volatile species with methanol, which can leave behind Mo poor zones. The catalyst is usually...

STUDY OF HYDROGEN SULFIDE REMOVAL FROM GROUNDWATER

Directory of Open Access Journals (Sweden)

T. Lupascu

2013-06-01

Full Text Available The process of the hydrogen sulfide removal from the underground water of the Hancesti town has been investigated. By oxygen bubbling through the water containing hydrogen sulfide, from the Hancesti well tube, sulfur is deposited in the porous structure of studied catalysts, which decreases their catalytic activity. Concomitantly, the process of adsorption / oxidation of hydrogen sulfide to sulfate take place. The kinetic research of the hydrogen sulfide removal from the Hancesti underground water, after its treatment by hydrogen peroxide, proves greater efficiency than in the case of modified carbonic adsorbents. As a result of used treatment, hydrogen sulfide is completely oxidized to sulfates

Modification of molybdenum disulfide in methanol solvent for hydrogen evolution reaction

Science.gov (United States)

Niyitanga, Theophile; Jeong, Hae Kyung

2018-05-01

Molybdenum disulfide is a promising catalyst to replace the expensive platinum as an electrocatalyst but needs to be modified to present excellent electrocatalytic properties. Herein, we successfully modify molybdenum disulfide in methanol solvent for hydrogen evolution reaction by using a simple hydrothermal method. Overpotential reduced to -0.6 V from -1.5 V, and energy band gap decreased from 1.73 eV to 1.58 eV after the modification. The modified molybdenum disulfide also demonstrated lower resistance (42 Ω) at high frequency (1000 kHz) compared with that (240 Ω) of the precursor, showing that conductivity of the modified molybdenum disulfide has improved.

Characterization of catalysts by Moessbauer spectroscopy: An application to the study of Fischer-Tropsch, hydrotreating and super Claus catalysts

International Nuclear Information System (INIS)

Kraan, A.M. van der; Boellaard, E.; Craje, M.W.J.

1993-01-01

Moessbauer spectroscopy is an excellent in-situ technique for the identification of phases present in catalysts. Applied to metallic iron catalysts used in the Fischer-Tropsch reaction it reveals a detailed picture of the carburization process and provides insight into the relation between the properties of the catalytic material and its activity. The influence of a support and the effect of alloying iron with an (in)active metal on the catalytic performance is discussed for Fe, Cu-Fe and Ni-Fe systems. In addition, Moessbauer spectroscopy is used for the identification of 'Co-sulfide' species present in sulfided Co and CoMo catalysts applied in one of the largest chemical processes in the world, the hydrotreatment of crude oil. A structural model is proposed. Finally, the contribution of Moessbauer spectroscopic studies to the development of a new catalyst for cleaning of Claus tail gas via selective oxidation of hydrogen sulfide to elemental sulfur is discussed. (orig.)

Application of molybdenum(VI) dichloride dioxide (MoO2 Cl2 ) in ...

Indian Academy of Sciences (India)

Administrator

A major use is in the hydrodesulfurisation (HDS) of petroleum, petro- chemicals and coal-derived liquids. Molybdenum catalysts are resistant to poisoning by sulfur and hence used for conversion of hydrogen and carbon monoxide to alcohols even in the presence of sulfur which would poison precious metal catalysts. Simi-.

Synthesis of waste cooking oil based biodiesel via ferric-manganese promoted molybdenum oxide / zirconia nanoparticle solid acid catalyst: influence of ferric and manganese dopants.

Science.gov (United States)

Alhassan, Fatah H; Rashid, Umer; Taufiq-Yap, Yun Hin

2015-01-01

The utilization of ferric-manganese promoted molybdenum oxide/zirconia (Fe-Mn- MoO3/ZrO2) (FMMZ) solid acid catalyst for production of biodiesel was demonstrated. FMMZ is produced through impregnation reaction followed by calcination at 600°C for 3 h. The characterization of FMMZ had been done using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), transmission electron microscopy(TEM) and Brunner-Emmett-Teller (BET) surface area measurement. The effect of waste cooking oil methyl esters (WCOME's) yield on the reactions variables such as reaction temperature, catalyst loading, molar ratio of methanol/oil and reusability were also assessed. The catalyst was used to convert the waste cooking oil into corresponding methyl esters (95.6%±0.15) within 5 h at 200℃ reaction temperature, 600 rpm stirring speed, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The reported catalyst was successfully recycled in six connective experiments without loss in activity. Moreover, the fuel properties of WCOME's were also reported using ASTM D 6751 methods.

Synthesis of carbon nanotubes by CVD method using iron and molybdenum-based catalysts supported on ceramic matrices;Sintese de nanotubos de carbono por CVD utilizando catalisadores a base de ferro e molibdenio suportados em matrizes ceramicas

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Ana Paula de Carvalho

2010-07-01

Molybdenum is known for its synergistic effect in the synthesis of carbon nanotubes (CNs) by chemical vapor deposition (CVD method). When added to typical catalysts like iron, nickel, and cobalt, even in small quantities, it is increases the yield of these nanostructures. The presence of Mo also has an influence on the type and number of CN walls formed. Although this effect is widely documented in the literature, there is not yet a consensus about the mechanism of action of molybdenum in catalytic systems. The objective of the present work is to study the influence of molybdenum on the catalytic activity of iron nanoparticle-based catalysts supported on magnesium oxide (Fe/MgO system) in the synthesis of carbon nanotubes by the CVD method. The Mo concentration was systematically varied from null to molar ratio values four times greater than the quantity of Fe, and the obtained material (catalysts and carbon nanotubes) were broadly characterized by different techniques. In order to also study the influence of the preparation method on the final composition of the catalytic system phases, the catalytic systems (Fe/MgO e FeMo{sub x}/MgO) were synthesized by two different methods: co-precipitation and impregnation. The greatest CN yields were observed for the catalysts prepared by coprecipitation. The difference was attributed to better dispersion of the Fe and Mo phases in the catalyst ceramic matrix. In the precipitation stage, it was observed the formation of layered double hydroxides whose concentration increased with the Mo content up to the ratio of Mo/Fe equal to 0.2. This phase is related to a better distribution of Fe and Mo in this concentration range. Another important characteristic observed is that the ceramic matrix is not inert. It can react both with Fe and Mo and form the iron solid solution in the magnesium oxide and the phases magnesium-ferrite (MgFe{sub 2}0{sub 4}) and magnesium molybdate (MgMo0{sub 4}). The MgFe{sub 2}0{sub 4} phase is observed in

Reduction and immobilization of molybdenum by Desulfovibrio desulfuricans

Energy Technology Data Exchange (ETDEWEB)

Tucker, M.D.; Barton, L.L.; Thomson, B.M. [Sandia National Laboratories, Albuquerque, NM (United States)

1997-07-01

Molybdenum contamination of groundwater occurs through activities such as molybdenum and copper mining and processing, shale oil production and power generation from coal-fired power plants. The mobility of Mo in the environment is strongly dependent on its chemical oxidation state. Under oxidizing conditions, Mo occurs as highly soluble and mobile Mo(VI) and Mo(V) compounds. However, under reducing conditions Mo usually forms insoluble Mo(IV) phases. The objective of this study was to demonstrate the ability of the sulfate-reducing bacterium, Desulfovibrio desulfuricans, to reduce Mo(IV) to Mo(IV) in anaerobic environments. Molybdenum-VI was reduced to Mo(IV) by washed cells of D. desulfuricans suspended in bicarbonate buffer solution with either lactate or H{sub 2} as the electron donor and Mo(VI) as the electron acceptor. Molybdenum-VIi reduction by D. desulfuricans in the presence of sulfide resulted in the extracelluar precipitation of the mineral molybdenite. Molybdenum-VI reduction did not occur in the absence of an electron donor or in the presence of heat-killed cells of D. desulfuricans. The results indicate that enzymatic reduction of Mo(VI) by sulfate-reducing bacteria may contribute to the accumulation of Mo(IV) in anaerobic environments and that there organisms may be useful for removing soluble Mo from contaminated water. 20 refs., 6 figs., 4 tabs.

Characterization of alumina supported molybdenum catalysts

Energy Technology Data Exchange (ETDEWEB)

Pastura, N M; Carmo, L M.P.M.; Sachett, C M.M.; Lam, Y L [Instituto Militar de Engenharia, Rio de Janeiro (Brazil). Secao de Quimica

1983-10-01

In order to optimize a bifunctional catalyst (acid and hydrogenating) of Mo/Al/sub 2/O/sub 3/, oxygen adsorption at 195 K and ethanol dehydration at 480-520 K were carried out using a series of these catalysts. The increase of Mo content increased the quantity of adsorbed oxygen, thus indicating that the number of hydrogenating sites also increased. The specific activity of ethanol dehydration varied slightly, indicating that the number of acid sites remains almost constant. On the other hand, the selectivity in ethylene (versus ether) increased markedly. This may be attributed to the increase in acid force of the acid sites.

Characterization of alumina supported molybdenum catalysts

International Nuclear Information System (INIS)

Pastura, N.M.; Carmo, L.M.P.M.; Sachett, C.M.M.; Lam, Y.L.

1983-01-01

In order to optimize a bifunctional catalyst (acid and hydrogenating) of Mo/Al 2 O 3 , oxygen adsorption at 195 K and ethanol dehydration at 480-520 K were carried out using a series of these catalysts. The increase of Mo content increased the quantity of adsorbed oxygen, thus indicating that the number of hydrogenating sites also increased. The specific activity of ethanol dehydration varied slightly, indicating that the number of acid sites remains almost constant. On the other hand, the selectivity in ethylene (versus ether) increased markedly. This may be attributed to the increase in acid force of the acid sites. (C.L.B.) [pt

MoO3/Al2O3 Catalyst: Comparison of Catalysts Prepared by New Slurry Impregnation with Molybdic Acid with Conventional Samples

Czech Academy of Sciences Publication Activity Database

Spojakina, A. A.; Kostova, N. G.; Vít, Zdeněk; Zdražil, Miroslav

2003-01-01

Roč. 77, - (2003), s. 767-778 ISSN 0137- 5083 R&D Projects: GA AV ČR IAA4072802 Institutional research plan: CEZ:AV0Z4072921 Keywords : hydrodesulfurization * molybdenum sulphide catalyst * alumina supported molybdenum oxide Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.515, year: 2003

Molybdenum oxide supported on silica (MoO3/SiO2): an efficient and reusable catalyst for the synthesis of 1,8-dioxodecahydroacridines under solvent-free conditions

International Nuclear Information System (INIS)

Khojastehnezhad, A.; Vafaei, M.; Moeinpour, F.

2014-01-01

Silica supported molybdenum oxide (MoO 3 /SiO 2 ) was found to be and efficient, eco-friendly and heterogeneous catalyst for the multicomponent reaction of aromatic aldehydes, dimedone and ammonium acetate or aromatic amines under solvent-free conditions to afford the corresponding 1,8-dioxodecahydroacridines in high yields. The catalyst can be easily recovered and reused for several times without considerable loss of activity. Furthermore, the present method offers several advantages, such as an easy experimental and work-up procedures, short reaction times and good to excellent yields. For the characterization were used: Fourier transform infrared spectroscopy (Ft-IR), X-ray diffraction and scanning electron microscopy analyses. (Author)

On the pelletizing of sulfide molybdenite concentrate

International Nuclear Information System (INIS)

Palant, A.A.

2007-01-01

Investigation results are discussed on the process of pelletizing with the use of various binders (water, syrup, sulfite-alcoholic residue and bentonite) for flotation sulfide molybdenite concentrate (∼84 % MoS 2 ) of the Mongolian deposit. It is established that with the use of syrup rather strong pellets (>300 g/p) of desired size (2-3 mm) can be obtained at a binder flowrate of 1 kg per 100 kg of concentrate. The main advantage of using syrup instead of bentonite lies in the fact that in this instance no depletion of a molybdenum calcine obtained by oxidizing roasting of raw ore takes place due to syrup complete burning out. This affects positively subsequent hydrometallurgical conversion because of decreasing molybdenum losses with waste cakes [ru

Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

KAUST Repository

Merle, Nicolas

2017-09-25

A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

KAUST Repository

Merle, Nicolas; Le Qué mé ner, Fré dé ric; Barman, Samir; Samantaray, Manoja; Szeto, Kai C.; De Mallmann, Aimery; Taoufik, Mostafa; Basset, Jean-Marie

2017-01-01

A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

Molybdenum carbide nanoparticles as catalysts for oil sands upgrading: Dynamics and free-energy profiles

International Nuclear Information System (INIS)

Liu, Xingchen; Salahub, Dennis R.

2015-01-01

There is no doubt that a huge gap exists in understanding heterogeneous catalysis between a cluster model of a few atoms and a bulk model of periodic slabs. Nanoparticles, which are crucial in heterogeneous catalysis in industry, lie in the middle of the gap. We present here our work on the computational modelling of molybdenum carbide nanoparticles (MCNPs) as the catalysts for the upgrading of oil sands in the in-situ environment, using benzene hydrogenation as a model reaction. With a cluster model, efforts were first made to understand the mechanism of the reaction with a density functional theory (DFT) study on the adsorption of benzene and its hydrogenation product – cyclohexane, as well as the cyclic hydrogenation reaction intermediates on the Mo 2 C(0001) surface. From the thermodynamic data, along with literature information, it was found that the benzene hydrogenation reaction on molybdenum carbide happens most likely through a Langmuir-Hinshelwood mechanism with the gradual lifting up of the benzene molecule. The electron localization function (ELF) was then used to help understand the nature of the interactions between the MCNPs, identifying strong multi-center interactions between the adsorbates and the MCNPs. To enable the treatment of larger nanoparticles, a fast semi-empirical density functional tight-binding (DFTB) method was parameterized. With this method, the potential energy profiles of benzene hydrogenation reactions on different sizes of MCNPs are calculated. The study was then extended to consider a MCNP embedded in solvent (benzene), using a quantum mechanical (DFTB) / molecular mechanical approach. Calculations on the free energies profiles with the umbrella sampling method show that the entropy of the MCNPs and the solvent are essential in understanding the catalytic activity of the transition metal related nanoparticles for solid/liquid heterogeneous catalysis

Molybdenum carbide nanoparticles as catalysts for oil sands upgrading: Dynamics and free-energy profiles

Energy Technology Data Exchange (ETDEWEB)

Liu, Xingchen; Salahub, Dennis R. [Department of Chemistry, Institute for Quantum Science and Technology, and Centre for Molecular Simulation, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4 (Canada)

2015-12-31

There is no doubt that a huge gap exists in understanding heterogeneous catalysis between a cluster model of a few atoms and a bulk model of periodic slabs. Nanoparticles, which are crucial in heterogeneous catalysis in industry, lie in the middle of the gap. We present here our work on the computational modelling of molybdenum carbide nanoparticles (MCNPs) as the catalysts for the upgrading of oil sands in the in-situ environment, using benzene hydrogenation as a model reaction. With a cluster model, efforts were first made to understand the mechanism of the reaction with a density functional theory (DFT) study on the adsorption of benzene and its hydrogenation product – cyclohexane, as well as the cyclic hydrogenation reaction intermediates on the Mo{sub 2}C(0001) surface. From the thermodynamic data, along with literature information, it was found that the benzene hydrogenation reaction on molybdenum carbide happens most likely through a Langmuir-Hinshelwood mechanism with the gradual lifting up of the benzene molecule. The electron localization function (ELF) was then used to help understand the nature of the interactions between the MCNPs, identifying strong multi-center interactions between the adsorbates and the MCNPs. To enable the treatment of larger nanoparticles, a fast semi-empirical density functional tight-binding (DFTB) method was parameterized. With this method, the potential energy profiles of benzene hydrogenation reactions on different sizes of MCNPs are calculated. The study was then extended to consider a MCNP embedded in solvent (benzene), using a quantum mechanical (DFTB) / molecular mechanical approach. Calculations on the free energies profiles with the umbrella sampling method show that the entropy of the MCNPs and the solvent are essential in understanding the catalytic activity of the transition metal related nanoparticles for solid/liquid heterogeneous catalysis.

Organic-inorganic hybrid polyionic liquid based polyoxometalate as nano porous material for selective oxidation of sulfides

Science.gov (United States)

Rafiee, Ezzat; Shahebrahimi, Shabnam

2017-07-01

Organic-inorganic hybrid nano porous materials based on poly(ionic liquid)-polyoxometalate (PIL-POM) were reported. These hybrid materials were synthesized by the reaction of 4-vinyl pyridine with 1,3-propanesultone, followed by the polymerization and also sulfonate-functionalized cross-linked poly(4-vinylpyridine) and combining these polymers with H5PMo10V2O40 (PMo10V2). Activity of prepared PIL-PMo10V2 hybrids were investigated as catalysts for oxidation of sulfides with H2O2 as oxidant. For understanding catalytic activities of the PIL-PMo10V2 hybrids in oxidation of sulfides, effect of catalyst composition, substrate, and reaction conditions were studied. The results show that the PIL-PMo10V2 hybrids are active as selective heterogeneous catalysts for oxidation of sulfides and can be recovered and reused. The catalyst was characterized by FT-IR, TGA-DSC, XRD, SEM/EDX, BET, CV and zeta potential measurement. Also, average molecular weight of prepared catalysts were measured.

Effect of Ni on the characteristics and hydrogenation activity of sulfide Mo/γ-Al2O3

International Nuclear Information System (INIS)

Schachtl, E.; Wuttke, E.; Gutierrez, O.Y.; Lercher, J.A.

2012-01-01

The hydrogenation of phenanthrene was explored on sulfide Mo/γ-Al 2 O 3 catalysts promoted with increasing concentrations of Ni. The characterization of the materials was done by N 2 -physisorption, X-ray diffraction, transmission electron microscopy, temperature programmed sulfidation and NO adsorption experiments. Increasing loading of Ni improves the dispersion of MoS 2 species; however, at Ni/(Mo+Ni) molar ratio higher than 0.5, segregation of Ni-sulfides is observed. The presence of Ni also facilitates the sulfidation of oxidic catalyst precursors by lowering the reduction temperature of Mo species. In the sulfide catalysts, Ni changes the structure of MoS 2 leading to shorter slabs with higher stacking degree than on Mo/γ-Al 2 O 3 , and increases the concentration of coordinatively unsaturated sites. The kinetic results (increased hydrogenation rate and changed reaction network in the presence of Ni) suggest that a highly active kind of active site is created by Ni promotion. (orig.)

NEXAFS characterization and reactivity studies of bimetallic vanadium molybdenum oxynitride hydrotreating catalysts

Energy Technology Data Exchange (ETDEWEB)

Kapoor, R.; Oyama, S.T. [Virginia Polytechnic Inst., Blacksburg, VA (United States); Fruehberger, B.; Chen, J.G. [Exxon Research and Engineering Company, Annandale, NJ (United States)

1997-02-27

The surface and bulk compositions of vanadium molybdenum oxynitride (V{sub 2}MoO{sub 1.7}N{sub 2.4}), prepared by temperature-programmed reaction (TPR) of vanadium molybdenum oxide (V{sub 2}MoO{sub 8}) with ammonia, have been characterized using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS data were recorded at the K-edges of nitrogen and oxygen, the L-edge of vanadium, and the M-edge of molybdenum. The nitrogen K-edge region of V-Mo oxynitride shows the characteristic NEXAFS features of early-transition-metal nitrides, although these features are different from those of either VN or Mo{sub 2}N. Furthermore, comparison of the electron yield and fluorescence yield measurements also reveals that the oxidation state is different for vanadium near the surface region and for vanadium in the bulk, which is estimated to be 2.8 {+-} 0.3 and 3.8 {+-} 0.3, respectively. The oxidation state of bulk molybdenum is also estimated to be 4.4 {+-} 0.3. The X-ray diffraction pattern shows that the bulk phase of the bimetallic oxide is different from the pure monometallic oxide phases but the oxynitride has a cubic structure that resembles the pure vanadium and molybdenum nitride phases. The V-Mo oxide as prepared shows a preferential orientation of [001] crystallographic planes which is lost during the nitridation process. This shows that the solid state transformation V{sub 2}MoO{sub 8} {yields} V{sub 2}MoO{sub 1.7}N{sub 2.4} is not topotactic. 27 refs., 8 figs., 1 tab.

Mössbauer emission study on 57Co doped carbon-supported Ni and Ni-Mo sulfide hydrotreating catalysts : the influence of phosphorus on the structure

NARCIS (Netherlands)

Crajé, M.W.J.; Beer, de V.H.J.; Kraan, van der A.M.

1991-01-01

In the present study it is demonstrated that Mössbauer emission spectroscopy (MES) can generate information on the various Ni phases present in sulfided Ni containing catalysts when a small amount of 57Co is used as a probe for Ni.Application of MES to 57Co:Ni(4.5)Mo(8.0)/C and 57Co:Ni(5.6)/C

Reactivity of non conventional supported mixed sulfides for hydro-treatment reactions; Reactivite de sulfures mixtes supportes non conventionnels pour les reactions d`hydrotraitement

Energy Technology Data Exchange (ETDEWEB)

Quartararo, J

1996-11-07

The properties of non conventional NiM sulfides (M: Mn, Fe, Cu,Zn, Re, Ru) was evaluated for two hydro treating reactions: hydro desulfurization (HDS) of dibenzo thiophene and benzo thiophene and hydrogenation (HYD) of cyclohexyl. The reactions were t first studied on Ni, Mo and NiMo sulfide catalysts. The influence of the nature of the molecule on the magnitude of promoting effect was demonstrated. The non conventional mono-metallic and bimetallic catalysts studied in this work were characterized by XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy) and TEM (transmission electron microscopy). Ni exhibits a negative effect on the activity of Mn, Cu, Zn and Re sulfide catalysts. This effect could be related to the formation of two separated sulfide phases: base metal sulfide and nickel sulfide. Nevertheless, a promoting effect was found in NiRu catalyst. In this catalyst, the Ru and the Ni are in a mixed phase. The results of this study demonstrate the importance of the type of metal associated to the nickel for the promoting effect and relate this effect to the formation of a mixed phase. (author)

Reaction of Hydrogen Sulfide with Oxygen in the Presence ofSulfite

Energy Technology Data Exchange (ETDEWEB)

Weres, Oleh; Tsao, Leon

1983-01-01

Commonly, abatement of hydrogen sulfide emissions from a geothermal powerplant requires that hydrogen sulfide dissolved in the cooling water be eliminated by chemical reaction. Oxidation by atmospheric oxygen is the preferred reaction, but requires a suitable catalyst. Nickel is the most potent and thereby cheapest catalyst for this purpose. One Mg/L nickel in the cooling water would allow 99% removal of hydrogen sulfide to be attained. A major drawback of catalytic air oxidation is that colloidal sulfur is a major reaction product; this causes rapid sludge accumulation and deposition of sulfur scale. The authors studied the kinetics and product distribution of the reaction of hydrogen sulfide with oxygen, catalyzed by nickel. Adding sodium sulfite to the solution completely suppresses formation of colloidal sulfur by converting it to thiosulfate. The oxidation reaction is an autocatalytic, free radical chain reaction. A rate expression for this reaction and a detailed reaction mechanism were developed. Nickel catalyzes the chain initiation step, and polysulfidoradical ions propagate the chains. Several complexes of iron and cobalt were also studied. Iron citrate and iron N-hydroxyEDT are the most effective iron based catalysts. Uncomplexed cobalt is as effective as nickel, but forms a precipitate of cobalt oxysulfide and is too expensive for practical use.

Reaction of hydrogen sulfide with oxygen in the presence of sulfite

Energy Technology Data Exchange (ETDEWEB)

Weres, O.; Tsao, L.

1983-01-14

Commonly, abatement of hydrogen sulfide emission from a geothermal powerplant requires that hydrogen sulfide dissolved in the cooling water be eliminated by chemical reaction. Oxidation by atmospheric oxygen is the preferred reaction, but requires a suitable catalyst. Nickel is the most potent and thereby cheapest catalyst for this purpose. One mg/L nickel in the cooling water would allow 99% removal of hydrogen sulfide to be attained. A major drawback of catalytic air oxidation is that colloidal sulfur is a major reaction product; this causes rapid sludge accumulation and deposition of sulfur scale. We studied the kinetics and product distribution of the reaction of hydrogen sulfide with oxygen, catalyzed by nickel. Adding sodium sulfite to the solution completely suppresses formation of colloidal sulfur by converting it to thiosulfate. The oxidation reaction is an autocatalytic, free radical chain reaction. A rate expression for this reaction and a detailed reaction mechanism were developed. Nickel catalyzes the chain initiation step, and polysulfidoradical ions propagate the chains. Several complexes of iron and cobalt were also studied. Iron citrate and iron N-hydroxyEDTA are the most effective iron based catalysts. Uncomplexed cobalt is as effective as nickel, but forms a precipitate of cobalt oxysulfide and is too expensive for practical use. 33 figures, 9 tables.

High hydrogen desorption properties of Mg-based nanocomposite at moderate temperatures: The effects of multiple catalysts in situ formed by adding nickel sulfides/graphene

Science.gov (United States)

Xie, Xiubo; Chen, Ming; Liu, Peng; Shang, Jiaxiang; Liu, Tong

2017-12-01

Nickel sulfides decorated reduced graphene oxide (rGO) has been produced by co-reducing Ni2+ and graphene oxide (GO), and is subsequently ball milled with Mg nanoparticles (NPs) produced by hydrogen plasma metal reaction (HPMR). The nickel sulfides of about 800 nm completely in situ change to MgS, Mg2Ni and Ni multiple catalysts after first hydrogenation/dehydrogenation process at 673 K. The Mg-5wt%NiS/rGO nanocomposite shows the highest hydrogen desorption kinetics and capacity properties, and the catalytic effect order of the additives is NiS/rGO, NiS and rGO. At 573 K, the Mg-NiS/rGO nanocomposite can quickly desorb 3.7 wt% H2 in 10 min and 4.5 wt% H2 in 60 min. The apparent hydrogen absorption and desorption activation energies of the Mg-5wt%NiS/rGO nanocomposite are decreased to 44.47 and 63.02 kJ mol-1, smaller than those of the Mg-5wt%rGO and Mg-5wt%NiS samples. The best hydrogen desorption properties of the Mg-5wt%NiS/rGO nanocomposite can be explained by the synergistic catalytic effects of the highly dispersed MgS, Mg2Ni and Ni catalysts on the rGO sheets, and the more nucleation sites between the catalysts, rGO sheets and Mg matrix.

Molybdenum oxide supported on silica (MoO{sub 3}/SiO{sub 2}): an efficient and reusable catalyst for the synthesis of 1,8-dioxodecahydroacridines under solvent-free conditions

Energy Technology Data Exchange (ETDEWEB)

Khojastehnezhad, A.; Vafaei, M. [Islamic Azad University, Mashhad Branch, Department of Chemistry, Mashhad (Iran, Islamic Republic of); Moeinpour, F., E-mail: akhojastehnezhad@yahoo.com [Islamic Azad University, Bandar Abbas Branch, Department of Chemistry, Bandar Abbas (Iran, Islamic Republic of)

2014-07-01

Silica supported molybdenum oxide (MoO{sub 3}/SiO{sub 2}) was found to be and efficient, eco-friendly and heterogeneous catalyst for the multicomponent reaction of aromatic aldehydes, dimedone and ammonium acetate or aromatic amines under solvent-free conditions to afford the corresponding 1,8-dioxodecahydroacridines in high yields. The catalyst can be easily recovered and reused for several times without considerable loss of activity. Furthermore, the present method offers several advantages, such as an easy experimental and work-up procedures, short reaction times and good to excellent yields. For the characterization were used: Fourier transform infrared spectroscopy (Ft-IR), X-ray diffraction and scanning electron microscopy analyses. (Author)

Molybdenum and tungsten disulfides surface-modified with a conducting polymer, polyaniline, for application in electrorheology

Czech Academy of Sciences Publication Activity Database

Stejskal, Jaroslav; Mrlík, M.; Plachý, T.; Trchová, Miroslava; Kovářová, Jana; Li, Yu

2017-01-01

Roč. 120, November (2017), s. 30-37 ISSN 1381-5148 R&D Projects: GA ČR(CZ) GA17-04109S Institutional support: RVO:61389013 Keywords : molybdenum sulfide * polyaniline * conducting polymer Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.151, year: 2016

Effect of Ni on the characteristics and hydrogenation activity of sulfide Mo/{gamma}-Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Schachtl, E.; Wuttke, E.; Gutierrez, O.Y.; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center

2012-07-01

The hydrogenation of phenanthrene was explored on sulfide Mo/{gamma}-Al{sub 2}O{sub 3} catalysts promoted with increasing concentrations of Ni. The characterization of the materials was done by N{sub 2}-physisorption, X-ray diffraction, transmission electron microscopy, temperature programmed sulfidation and NO adsorption experiments. Increasing loading of Ni improves the dispersion of MoS{sub 2} species; however, at Ni/(Mo+Ni) molar ratio higher than 0.5, segregation of Ni-sulfides is observed. The presence of Ni also facilitates the sulfidation of oxidic catalyst precursors by lowering the reduction temperature of Mo species. In the sulfide catalysts, Ni changes the structure of MoS{sub 2} leading to shorter slabs with higher stacking degree than on Mo/{gamma}-Al{sub 2}O{sub 3}, and increases the concentration of coordinatively unsaturated sites. The kinetic results (increased hydrogenation rate and changed reaction network in the presence of Ni) suggest that a highly active kind of active site is created by Ni promotion. (orig.)

Ternary cobalt-molybdenum-zirconium coatings for alternative energies

Science.gov (United States)

Yar-Mukhamedova, Gulmira; Ved', Maryna; Sakhnenko, Nikolay; Koziar, Maryna

2017-11-01

Consistent patterns for electrodeposition of Co-Mo-Zr coatings from polyligand citrate-pyrophosphate bath were investigated. The effect of both current density amplitude and pulse on/off time on the quality, composition and surface morphology of the galvanic alloys were determined. It was established the coating Co-Mo-Zr enrichment by molybdenum with current density increasing up to 8 A dm-2 as well as the rising of pulse time and pause duration promotes the content of molybdenum because of subsequent chemical reduction of its intermediate oxides by hydrogen ad-atoms. It was found that the content of the alloying metals in the coating Co-Mo-Zr depends on the current density and on/off times extremely and maximum Mo and Zr content corresponds to the current density interval 4-6 A dm-2, on-/off-time 2-10 ms. Chemical resistance of binary and ternary coatings based on cobalt is caused by the increased tendency to passivity and high resistance to pitting corrosion in the presence of molybdenum and zirconium, as well as the acid nature of their oxides. Binary coating with molybdenum content not less than 20 at.% and ternary ones with zirconium content in terms of corrosion deep index are in a group ;very proof;. It was shown that Co-Mo-Zr alloys exhibits the greatest level of catalytic properties as cathode material for hydrogen electrolytic production from acidic media which is not inferior a platinum electrode. The deposits Co-Mo-Zr with zirconium content 2-4 at.% demonstrate high catalytic properties in the carbon(II) oxide conversion. This confirms the efficiency of materials as catalysts for the gaseous wastes purification and gives the reason to recommend them as catalysts for red-ox processes activating by oxygen as well as electrode materials for red-ox batteries.

Preparation of transition metal sulfide nanoparticles via hydrothermal route

International Nuclear Information System (INIS)

Fei-Ling, P.; Chin-Hua, C.; Sarani Zakaria; Tze-Khong, L.; Mohd Ambar Yarmo; Nay-Ming, H.

2010-01-01

Nano sized copper sulfide, iron sulfide and molybdenum sulfide were successfully synthesised via a simple hydrothermal method. Sodium thiosulfate pentahydrate (Na 2 S 2 O 3 ·5H 2 O) and hydroxylamine sulfate ((H 3 NO) 2 ·H 2 SO 4 ) were used as the starting materials and reacted with the transition metal source at 200 degree Celsius for 90 min. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FTIR). Spherical shape CuS and FeS 2 nanoparticles with high crystallinity were successfully produced. The transmission electron micrographs revealed the well-dispersibility of the produced nanoparticles. Scanning electron micrograph showed the MoS 2 nanoparticles possessed a spherical shape with sheet-like structure covering on the outer surface of the particles. (author)

Effect of the nature of the support on molybdenum catalytic behavior in diesel particulate combustion

International Nuclear Information System (INIS)

Braun, Silvana; Appel, Lucia G.; Schmal, Martin

2002-01-01

Mo/SiO 2 and Mo/TiO 2 catalysts with three different molybdenum contents were prepared using non-porous supports and the thermal spreading method for the combustion of a particulate material (PM). The results of scanning electron microscopy (SEM) and N 2 adsorption/desorption techniques showed that the thermal spreading preparation method does not induce relevant textural changes on the supports. X-ray diffraction (XRD) results showed the occurrence of thermal spreading of MoO 3 onto silica and titania supports. Diffuse reflection spectroscopy (DRS) results provided clear evidence of different Mo species on these systems: highly dispersed species on the silica catalysts and polymolybdates on the titania catalysts. It may be inferred that when prepared by the thermal spreading method the nature of the support determines the kind of molybdenum species formed in these catalysts, irrespective of the Mo content. The reactive data were evaluated by differential scanning calorimetry (DSC), using a physical mixture of PM and the catalysts. The silica-supported catalysts showed higher reactivity for PM combustion than the titania-supported ones, being the most active the systems with the Mo monolayer. The results suggested that the dispersed species are far more active than the polymolybdates or MoO 3 itself

Importance of molybdenum in the nitrogen metabolism of microorganisms and higher plants

Energy Technology Data Exchange (ETDEWEB)

Mulder, E G

1948-01-01

The effect of molybdenum on the growth of microorganisms and higher plants and on some well-defined biochemical reactions was investigated. Results indicate that Aspergillus niger requires small amounts of molybdenum when growing in a culture solution supplied with nitrate nitrogen. With ammonium sulfate as a source of nitrogen, the response of the fungus to molybdenum was much smaller. It was shown that this different response of Aspergillus to molybdenum was not brought about by a difference in purity of both nitrogen compounds used, nor by a difference in absorption of the molybdenum impurity, but by a considerably higher requirement of molybdenum in a medium with nitrate nitrogen. The growth-rate curve and the increasing sporulation of Aspergillus niger with increasing amounts of molybdenum were used in estimating very small amounts of this element in various materials. In culture solution experiments with tomato, barley and oat plants the effect of traces of molybdenum on the growth of these plants was investigated. In good agreement with the results of the experiments with Aspergillus and denitrifying bacteria it could be shown that in the green plant as in these microorganisms molybdenum is acting as a catalyst in nitrate reduction. In experiments with Azotobacter chroococcum and leguminous plants the effect of molybdenum on the fixation of gaseous N/sub 2/ was studied. In culture solutions with pea plants the effect of molybdenum on the nitrogen fixation of the nodules was investigated. In the absence of molybdenum as well as in a complete nutrient medium many nodules were formed. 30 references, 6 figures, 16 tables.

GEMAS: Molybdenum Spatial Distribution Patterns in European Soil

Science.gov (United States)

Cicchella, Domenico; Zuzolo, Daniela; Demetriades, Alecos; De Vivo, Benedetto; Eklund, Mikael; Ladenberger, Anna; Negrel, Philippe; O'Connor, Patrick

2017-04-01

Molybdenum is an essential trace element for both plants and animals as well as for human being. It is one such trace element for which potential health concerns have been raised but for which few data exist and little investigation or interpretation of distributions in soils has been made. The main goal of this study was to fill this gap. Molybdenum (Mo) concentrations are reported for the similar spatial distribution patterns mainly governed by geology (parent material and mineralisation), as well as weathering, soil formation and climate since the last glaciations period. The dominant feature is represented by low Mo concentrations over the coarse-grained sandy deposits of the last glaciations in central northern Europe while the most extensive anomalies occur in Scandinavian soils. The highest Mo concentration value occurs to the North of Oslo close to one of the largest porphyry Mo deposit of the World. Some interesting anomalous patterns occur also in Italy in correspondence with alkaline volcanics, in Spain and Greece associated with sulfides mineralizations and in Slovenia and Croatia where are probably related to the long weathering history of karstic residual soils. Anomalous concentrations in some areas of Ireland represent a clear example of how an excess of molybdenum has produced potentially toxic pastures. In fact, these give rise to problems particularly in young cattle when excess molybdenum in the herbage acts as an antagonist, which militates against efficient copper absorption by the animal.

Highly active sulfided CoMo catalysts supported on (ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} ternary oxides

Energy Technology Data Exchange (ETDEWEB)

Escobar, José, E-mail: jeaguila@imp.mx [Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero, México, D.F. 07730 (Mexico); De Los Reyes, José A., E-mail: jarh@xanum.uam.mx [Area de Ing. Química, UAM – Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, México, D.F. 09340 (Mexico); Ulín, Carlos A. [Area de Ing. Química, UAM – Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, México, D.F. 09340 (Mexico); Barrera, María C., E-mail: mcbdgavilan@gmail.com [Facultad de Ciencias Químicas, Universidad Veracruzana, Av. Universidad km. 7.5, Col. Santa Isabel, Coatzacoalcos, Veracruz, México, D.F. 96538 (Mexico)

2013-12-16

(ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} ternary oxide at 20 mol% Al{sub 2}O{sub 3} (80% ZrO{sub 2}–TiO{sub 2}, in turn at 40–60 mol ratio) prepared by controlled co-precipitation (by urea thermal decomposition) of zirconium (ZrOCl{sub 2}·8H{sub 2}O) and titanium (TiCl{sub 4}) chlorides over a ground alumina substrate constitutes a promising material to be used as carrier of sulfided hydrodesulfurization (HDS) catalysts. After calcining (at 500 °C), the ternary oxide presented textural properties (S{sub g} = 387 m{sup 2} g{sup −1}, V{sub p} = 0.74 ml g{sup −1}, mean pore diameter = 7.6 nm) suitable to its utilization as carrier of catalysts applied in the oil-derived middle distillates HDS. As determined by temperature programmed-reduction and Raman and UV–vis spectroscopies ZrO{sub 2}–TiO{sub 2} deposition over alumina substrate resulted in decreased proportion of Mo{sup 6+} species in tetrahedral coordination on the oxidic impregnated material. As those species constitute hardly reducible precursors, their diminished concentration could be reflected in enhanced amount of Mo species susceptible of activation by sulfiding (H{sub 2}S/H{sub 2} at 400 °C) over our ternary carrier. Limiting the concentration of zirconia-titania (at 40–60 mol ratio) to 20 mol% in the mixed oxides support allowed the preparation of highly active promoted (by cobalt, at Co/(Co + Mo) = 0.3) MoS{sub 2} phase (at 2.8 atoms/nm{sup 2}), that formulation showing excellent properties in hydrodesulfurization (HDS) of both dibenzothiophene and highly-refractory 4,6-dimethyl-dibenzothiophene. Due to alike yields to various HDS products over CoMo/(ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} and the corresponding Al{sub 2}O{sub 3}-supported formulation, presence of similar actives sites over those catalysts was strongly suggested. It seemed that enhanced concentration of octahedral Mo{sup 6+} over the oxidic impregnated precursor with (ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3

Report of liquefaction catalyst study meeting (March 1996); Ekika shokubai kentokai hokoku

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-03-01

Studied in the research are four iron-based catalysts, which are natural pyrite, synthetic iron sulfide, synthetic iron hydroxide, and catalyst-attached carbon. Tanito Harum coal is treated in a 0.01t/d-capable continuous operation furnace (once-through) under conditions of 450 degrees C and 170kgf/cm{sup 2} with catalyst addition of 1.0, 3.0wt% (catalyst-attached carbon 0.6, 1.0wt%), and a liquid yield of 41.5-48.6wt%-daf coal is achieved. A higher yield results when more catalyst is added. The same yield as achieved by the addition of 3wt% natural pyrite is obtained by the addition of 1.9wt% synthetic iron sulfide, 1.5wt% of synthetic iron hydroxide, or 0.7wt% catalyst-attached coal. The catalyst cost for treating a ton of coal is 4-9 hundred yen, which is far more expensive than the cost set forth as the target. Catalysts whose production process embodiment is now under study are natural pyrite and synthetic iron sulfide, and studies for others are just preliminary. Provided that the practical application of the liquefaction technology realizes in about 2000, then the petroleum price is predicted to be 23 dollars per barrel. Coal liquefaction products will have to be produced at a cost which will enable competition with the said petroleum price. (NEDO)

Ammonia treated Mo/AC catalysts for CO hydrogenation with ...

Indian Academy of Sciences (India)

A series of ammonia treated Mo/Activated Carbon (AC) catalysts were synthesized by wet impregnation method by nominal incorporation of 5, 10 and 15 wt% of molybdenum. The calcined catalysts (500◦C, 4 h, N₂ flow) were subjected to a stepwise ammonia treatment at temperatures from 25 up to 700◦C. This work ...

Molybdenum, molybdenum oxides, and their electrochemistry.

Science.gov (United States)

Saji, Viswanathan S; Lee, Chi-Woo

2012-07-01

The electrochemical behaviors of molybdenum and its oxides, both in bulk and thin film dimensions, are critical because of their widespread applications in steels, electrocatalysts, electrochromic materials, batteries, sensors, and solar cells. An important area of current interest is electrodeposited CIGS-based solar cells where a molybdenum/glass electrode forms the back contact. Surprisingly, the basic electrochemistry of molybdenum and its oxides has not been reviewed with due attention. In this Review, we assess the scattered information. The potential and pH dependent active, passive, and transpassive behaviors of molybdenum in aqueous media are explained. The major surface oxide species observed, reversible redox transitions of the surface oxides, pseudocapacitance and catalytic reduction are discussed along with carefully conducted experimental results on a typical molybdenum glass back contact employed in CIGS-based solar cells. The applications of molybdenum oxides and the electrodeposition of molybdenum are briefly reviewed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular and Silica-Supported Molybdenum Alkyne Metathesis Catalysts: Influence of Electronics and Dynamics on Activity Revealed by Kinetics, Solid-State NMR, and Chemical Shift Analysis.

Science.gov (United States)

Estes, Deven P; Gordon, Christopher P; Fedorov, Alexey; Liao, Wei-Chih; Ehrhorn, Henrike; Bittner, Celine; Zier, Manuel Luca; Bockfeld, Dirk; Chan, Ka Wing; Eisenstein, Odile; Raynaud, Christophe; Tamm, Matthias; Copéret, Christophe

2017-12-06

Molybdenum-based molecular alkylidyne complexes of the type [MesC≡Mo{OC(CH 3 ) 3-x (CF 3 ) x } 3 ] (MoF 0 , x = 0; MoF 3 , x = 1; MoF 6 , x = 2; MoF 9 , x = 3; Mes = 2,4,6-trimethylphenyl) and their silica-supported analogues are prepared and characterized at the molecular level, in particular by solid-state NMR, and their alkyne metathesis catalytic activity is evaluated. The 13 C NMR chemical shift of the alkylidyne carbon increases with increasing number of fluorine atoms on the alkoxide ligands for both molecular and supported catalysts but with more shielded values for the supported complexes. The activity of these catalysts increases in the order MoF 0 molecular and supported species. Detailed solid-state NMR analysis of molecular and silica-supported metal alkylidyne catalysts coupled with DFT/ZORA calculations rationalize the NMR spectroscopic signatures and discernible activity trends at the frontier orbital level: (1) increasing the number of fluorine atoms lowers the energy of the π*(M≡C) orbital, explaining the more deshielded chemical shift values; it also leads to an increased electrophilicity and higher reactivity for catalysts up to MoF 6 , prior to a sharp decrease in reactivity for MoF 9 due to the formation of stable metallacyclobutadiene intermediates; (2) the silica-supported catalysts are less active than their molecular analogues because they are less electrophilic and dynamic, as revealed by their 13 C NMR chemical shift tensors.

Novel catalysts for upgrading coal-derived liquids. Final technical progress report

Energy Technology Data Exchange (ETDEWEB)

Thompson, L.T.; Savage, P.E.; Briggs, D.E.

1995-03-31

Research described in this report was aimed at synthesizing and evaluating supported Mo oxynitrides and oxycarbides for the selective removal of nitrogen, sulfur and oxygen from model and authentic coal-derived liquids. The Al{sub 2}O{sub 3}-supported oxynitrides and oxycarbides were synthesized via the temperature programmed reaction of supported molybdenum oxides or hydrogen bronzes with NH{sub 3} or an equimolar mixture of CH{sub 4} and H{sub 2}. Phase constituents and composition were determined by X-ray diffraction, CHN analysis, and neutron activation analysis. Oxygen chemisorption was used to probe the surface structure of the catalysts. The reaction rate data was collected using specially designed micro-batch reactors. The Al{sub 2}O{sub 3}-supported Mo oxynitrides and oxycarbides were competitively active for quinoline hydrodenitrogenation (HDN), benzothiophene hydrodesulfurization (HDS) and benzofuran hydrodeoxygenation (HDO). In fact, the HDN and HDO specific reaction rates for several of the oxynitrides and oxycarbides were higher than those of a commercial Ni-Mo/Al{sub 2}O{sub 3} hydrotreatment catalyst. Furthermore, the product distributions indicated that the oxynitrides and oxycarbides were more hydrogen efficient than the sulfide catalysts. For HDN and HDS the catalytic activity was a strong inverse function of the Mo loading. In contrast, the benzofuran hydrodeoxygenation (HDO) activities did not appear to be affected by the Mo loading but were affected by the heating rate employed during nitridation or carburization. This observation suggested that HDN and HDS occurred on the same active sites while HDO was catalyzed by a different type of site.

Recycling of spent hydroprocessing catalysts: EURECAT technology

Energy Technology Data Exchange (ETDEWEB)

Berrebi, G.; Dufresne, P.; Jacquier, Y. (EURECAT-European Reprocessing Catalysts, La Voulte sur Rhone (France))

1994-04-01

Disposal of spent catalyst is a growing concern for all refiners. Environmental regulations are becoming stricter and stricter and there are State recommendations to develop disposal routes which would emphasize recycling as much as possible, and processing the wastes as near as possible to the production center. In this context, EURECAT has developed a recycling process for the hydroprocessing catalysts used in the oil refineries (NiMo, CoMo, NiW on alumina or mixed alumina silica). The process starts with a regeneration of the catalyst to eliminate hydrocarbons, carbon and sulfur. After a caustic roasting, the material is leached to obtain a solution containing mainly molybdenum (or tungsten) and vanadium, and a solid containing essentially alumina, cobalt and/or nickel. Molybdenum and vanadium are separated by an ion exchange resin technique. The solid is processed in an arc furnace to separate the alumina. Nickel and cobalt are separated by conventional solvent extraction to obtain pure metal. Alumina is disposed of as an inert slag. The strength of the process lies in the combination of proven technologies applied by companies whose reliability in their respective field is well known. The aspects concerning spent catalyst handling, packaging and transport are also discussed. 13 refs., 2 figs., 2 tabs.

Catalytic oxidation of albendazole using molybdenum supported on carbon nanotubes as catalyst; Oxidacion catalitica de albendazol empleando como catalizador molibdeno soportado en nanotubos de carbono

Energy Technology Data Exchange (ETDEWEB)

Sun-Kou, Maria del Rosario; Vega Carrasco, Edgar R., E-mail: msun@pucp.edu.pe [Departamento de Ciencias, Seccion Quimica. Pontificia Universidad Catolica del Peru, Avenida Universitaria 1801, Lima (Peru); Picasso Escobar, Gino I. [Laboratorio de Investigacion de Fisicoquimica, Facultad de Ciencias, Universidad Nacional de Ingenieria, Avenida Tupac Amaru 210, Lima (Peru)

2013-10-15

The catalytic oxidation reaction of the thioether group (-S-) in the structure to the drug albendazole (C{sub 12}H{sub 15}N{sub 3}O{sub 2}S) was studied in order to obtain a pharmacologically active molecule known as albendazole sulfoxide. With this purpose, three heterogeneous catalysts were prepared using molybdenum (Mo) as active phase and carbon nanotubes as a multiple-layer catalyst support. The incorporation of the active phase was performed by wet impregnation, with subsequent calcination for 4 hours at 400 {sup o}C. For the catalytic oxidation reaction was employed hydrogen peroxide-urea (H{sub 2}NCONH{sub 2}·H{sub 2}O{sub 2}) as oxidizing agent and methanol (CH{sub 3}OH) as reaction medium. The textural and morphology characterization of carbon nanoparticles and catalysts was carried out by adsorption-desorption of N{sub 2} (BET) and scanning electron microscopy (SEM). The identification and quantification of the reaction products were followed by Fourier transform infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC), respectively. With the yield, selectivity and conversion higher than 90% after 60 minutes of reaction, albendazole sulphoxide was obtained as major product of oxidation reaction. (author)

Recovery of molybdenum using alumina microspheres and precipitation with selective organic reagents

International Nuclear Information System (INIS)

Carvalho, Fatima Maria Sequeira de; Abrao, Alcidio

1998-01-01

In this paper is presented a study for the optimization of dissolution of the UAL x plates used for irradiation and production of radiomolybdenum. The alloy is dissolved in nitric acid with mercury as catalyst. The separation and concentration of the molybdenum was achieved using a chromatographic grade alumina microspheres column. the purified eluted molybdenum is finally precipitated using one of the selective reagents: alizarine blue, α,α'- bipyridine and 1,10-phenanthroline. Any one of the obtained precipitate can be fired to the molybdenum trioxide. The interference of the following elements was studied: Re(VII), U(VI), Cr(VI), W(VI), V(V), Te(IV), Ti(IV), Zr(IV), Th(IV), Fe(III), Au(III), Ru(III), Al(III), Bi(III), Sb(III), Ce(IV), Pr(III), Sc(III), Y(III), Sm(III), Ba(II), Sr(II), Ni(II), Co(II), Cs(I). The molybdenum precipitates were characterized by gravimetric, CHN, TG, DTG, IR and X-ray diffraction analyses. (author)

On the role of acidity in amorphous silica-alumina based catalysts

NARCIS (Netherlands)

Poduval, D.G.

2011-01-01

Amorphous silica-alumina (ASA) is widely used as a solid acid catalyst or as a carrier for well-dispersed metal sulfide or metal catalysts. They are often involved in hydrocracking catalyst formulations, especially so when the aim is to produce middle distillates from heavy oil fractions. With

Hydrogen sulfide-powered solid oxide fuel cells

Science.gov (United States)

Liu, Man

2004-12-01

The potential utilization of hydrogen sulfide as fuel in solid oxide fuel cells has been investigated using an oxide-ion conducting YSZ electrolyte and different kinds of anode catalysts at operating temperatures in the range of 700--900°C and at atmospheric pressure. This technology offers an economically attractive alternative to present methods for removing toxic and corrosive H2S gas from sour gas streams and a promising approach for cogenerating electrical energy and useful chemicals. The primary objective of the present research was to find active and stable anode materials. Fuel cell experimental results showed that platinum was a good electrocatalyst for the conversion of H2S, but the Pt/YSZ interface was physically unstable due to the reversible formation and decomposition of PtS in H 2S streams at elevated temperatures. Moreover, instability of the Pt/YSZ interface was accelerated significantly by electrochemical reactions, and ultimately led to the detachment of the Pt anode from the electrolyte. It has been shown that an interlayer of TiO2 stabilized the Pt anode on YSZ electrolyte, thereby prolonging cell lifetime. However, the current output for a fuel cell using Pt/TiO2 as anode was not improved compared to using Pt alone. It was therefore necessary to investigate novel anode systems for H 2S-air SOFCs. New anode catalysts comprising composite metal sulfides were developed. These catalysts exhibited good electrical conductivity and better catalytic activity than Pt. In contrast to MoS2 alone, composite catalysts (M-Mo-S, M = Fe, Co, Ni) were not volatile and had superior stability. However, when used for extended periods of time, detachment of Pt current collecting film from anodes comprising metal sulfides alone resulted in a large increase in contact resistance and reduction in cell performance. Consequently, a systematic investigation was conducted to identify alternative electronic conductors for use with M-Mo-S catalysts. Anode catalysts

Rate and selectivity modification in Fischer-Tropsch synthesis over charcoal supported molybdenum by forced concentration cycling

International Nuclear Information System (INIS)

Dun, J.W.; Gulari, E.

1985-01-01

Forced concentration cycling of the feed between pure CO and pure H/sub 2/ was used to successfully change both the selectivities and reactivities of promoted and unpromoted charcoal supported molybdenum catalysts in Fischer-Tropsch synthesis. It was found that with the unpromoted catalyst the rate enhancement increases with temperature and selectivity shifts towards methane. At the lower temperatures concentration cycling increases selectivity to ethane and higher hydrocarbons to levels only achievable with promised catalysts. Periodic operation with the potassium promoted catalyst results in small rate enhancements but the olefin to paraffin ratio is dramatically changed without changing the carbon number distribution

MOLYBDENUM CATALYZED ACID PEROXIDE BLEACHING OF EUCALYPTUS KRAFT PULP

Directory of Open Access Journals (Sweden)

Marcos S. Rabelo

2008-08-01

Full Text Available Molybdenum catalyzed peroxide bleaching (PMo Stage consists of pulp treatment with hydrogen peroxide under acidic conditions in the presence of a molybdenum catalyst. Molybdenum is applied in catalytic doses (50-200 mg/kg pulp and may originate from various sources, including (NH46Mo7O24.4H2O, Na2MoO4.2H2O, siliconmolybdate, etc. This work is aimed at optimizing the PMo stage and evaluating its industrial application in the OAZDP sequence. Optimum PMo stage conditions for bleaching eucalyptus pulp were 90 ºC, pH 3.5, 2 h, 0.1 kg/adt Mo and 5 kg/adt H2O2. The PMo stage was more efficient to remove pulp hexenuronic acids than lignin. Its efficiency decreased with increasing pH in the range of 1.5-5.5, while it increased with increasing temperature and peroxide and molybdenum doses. The application of the PMo stage as replacement for the A-stage of the AZDP sequence significantly decreased chlorine dioxide demand. The PMo stage caused a decrease of 20-30% in the generation of organically bound chlorine. The quality parameters of the pulp produced during the PMo stage mill trial were comparable to those obtained with the reference A-stage.

Hydrous titanium oxide-supported catalysts

International Nuclear Information System (INIS)

Dosch, R.G.; Stohl, F.V.; Richardson, J.T.

1990-01-01

Catalysts were prepared on hydrous titanium oxide (HTO) supports by ion exchange of an active metal for Na + ions incorporated in the HTO support during preparation by reaction with the parent Ti alkoxide. Strong active metal-HTO interactions as a result of the ion exchange reaction can require significantly different conditions for activation as compared to catalysts prepared by more widely used incipient wetness methods. The latter catalysts typically involve conversion or while the HTO catalysts require the alteration of electrostatic bonds between the metal and support with subsequent alteration of the support itself. In this paper, the authors discuss the activation, via sulfidation or reduction, of catalysts consisting of Co, Mo, or Ni-Mo dispersed on HTO supports by ion exchange. Correlations between the activation process and the hydrogenation, hydrodeoxygenation, and hydrodesulfurization activities of the catalysts are presented

Metal recovery from spent refinery catalysts by means of biotechnological strategies

International Nuclear Information System (INIS)

Beolchini, F.; Fonti, V.; Ferella, F.; Veglio, F.

2010-01-01

A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts.

Metal recovery from spent refinery catalysts by means of biotechnological strategies

Energy Technology Data Exchange (ETDEWEB)

Beolchini, F., E-mail: f.beolchini@univpm.it [Department of Marine Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona (Italy); Fonti, V. [Department of Marine Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona (Italy); Ferella, F.; Veglio, F. [Department of Chemistry, Chemical Engineering and Materials, University of L' Aquila, Monteluco di Roio, 67040 L' Aquila (Italy)

2010-06-15

A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts.

Molybdenum Sulfide Induce Growth Enhancement Effect of Rice ( Oryza sativa L.) through Regulating the Synthesis of Chlorophyll and the Expression of Aquaporin Gene.

Science.gov (United States)

Li, Yadong; Jin, Qian; Yang, Desong; Cui, Jianghu

2018-04-25

Molybdenum sulfide (MoS 2 ) has been applied widely in industrial and environmental application, leading to increasing release into environment. So far, no studies have been investigated with regard to the potential effect of MoS 2 on plants. Herein, we studied the impact of MoS 2 on the growth, chlorophyll content, lipid peroxidation, antioxidase system, and aquaporins of rice for the first time. Results showed that MoS 2 did not significantly affect the germination of rice seeds, malonaldehyde (MDA) content, and the antioxidant enzyme activity. While the length and biomass of rice root and shoot, chlorophyll content index (CCI), and expression of aquaporin genes were significantly increased. Based on these results, we concluded that MoS 2 promoted rice growth through (i) the promotion of nitrogen source assimilation, (ii) the enhancement of photosynthesis, enzymatic-related biochemical reactions, and metabolic processes, subsequently, (iii) the acceleration of cell division and expansion, furthermore (iv) no abiotic stress and favorable condition of antioxidant enzyme system. These results provided an important insight into the further application of MoS 2 on agriculture and environment.

Sythesis of metal sulfide nanomaerials via thermal decomposition of single-source percursors

Energy Technology Data Exchange (ETDEWEB)

Jen-La Plante, Ilan; Zeid, Tahani W.; Yang, Peidong; Mokari, Taleb

2010-06-03

In this report, we present a synthetic method for the formation of cuprous sulfide (Cu2S) and lead sulfide (PbS) nanomaterials directly on substrates from the thermolysis of single-source precursors. We find that the final morphology and arrangement of the nanomaterials may be controlled through the concentration of the dissolved precursors and choice of solvent. One-dimensional (1-D) morphologies may also be grown onto substrates with the addition of a metal catalyst layer through solution-liquid-solid (SLS) growth. These synthetic techniques may be expanded to other metal sulfide materials.

Catalytic Hydrodeoxygenation of Biomass Pyrolysis Vapor Model Compounds over Molybdenum Sulfide Catalysts: Influence of Support, H₂S and Water

DEFF Research Database (Denmark)

Arndal, Trine Marie Hartmann; Høj, Martin; Pintos, Delfina Garcia

value, acidity and stability [1,2]. Upgrading ofcondensed pyrolysis oil is challenged by severe polymerization and coking upon heating. Instead, it is proposed toperform pyrolysis in the presence of hydrogen and an HDO catalyst for immediate stabilization and upgrading ofreactive pyrolysis products...

Synthesis and characterization of catalysts for the selective transformation of biomass-derived materials

Science.gov (United States)

Ghampson, Isaac Tyrone

The experimental work in this thesis focuses on generating catalysts for two intermediate processes related to the thermal conversion of lignocellulosic biomass: the synthesis and characterization of mesoporous silica supported cobalt catalysts for the Fischer-Tropsch reaction, and an exploration of the reactivity of bulk and supported molybdenum-based nitride catalysts for the hydrodeoxygenation (HDO) of guaiacol, a lignin model compound. The first section of the work details the synthesis of a series of silica-supported cobalt Fischer-Tropsch catalysts with pore diameters ranging from 2-23 nm. Detailed X-ray diffraction measurements were used to determine the composition and particle diameters of the metal fraction, analyzed as a three-phase system containing Cofcc, Cohcp and CoO particles. Catalyst properties were determined at three stages in catalyst history: (1) after the initial calcination step to thermally decompose the catalyst precursor into Co3O4, (2) after the hydrogen reduction step to activate the catalyst to Co and (3) after the FT reaction. From the study, it was observed that larger pore diameters supported higher turnover frequency; smaller pore diameters yielded larger mole fraction of CoO; XRD on post-reduction and post-FTS catalyst samples indicated significant changes in dispersivity after reduction. In the next section, the catalytic behaviors of unsupported, activated carbon-, alumina-, and SBA-15 mesoporous silica-supported molybdenum nitride catalysts were evaluated for the hydrodeoxygenation of guaiacol (2-methoxy phenol) at 300°C and 5 MPa. The nitride catalysts were prepared by thermal decomposition of bulk and supported ammonium heptamolybdate to form MoO 3 followed by nitridation in either flowing ammonia or a nitrogen/hydrogen mixture. The catalytic properties were strongly affected by the nitriding and purging treatment as well as the physical and chemical properties of support. The overall reaction was influenced by the

Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

Science.gov (United States)

Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

2008-01-01

Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

Elucidation of hydrodesulfurization mechanism using 35S radioisotope pulse tracer methods

International Nuclear Information System (INIS)

Kabe, Toshiaki; Qian, Weihua; Ishihara, Atsushi

1997-01-01

Molybdenum-based catalysts as hydrodesulfurization (HDS) catalysts are among the most important industrial catalysts. One of the new approaches characterizing the structure of such catalysts and the behavior of sulfur over the 'working' catalyst is a 35S radioisotope pulse tracer method (RPTM). By tracing the behavior of sulfur in the HDS reaction and sulfur exchange reaction over the sulfided Mo/Al 2 O 3 and Co-Mo/Al 2 O 3 catalysts under practical reaction conditions, it becomes possible for us to observe the catalytic behavior of the catalyst in situ. The formation process of active sites, the important role that H 2 S plays in this process, and the promotion by cobalt for Mo/Al 2 O 3 catalyst have become better understood

Tungsten carbide and tungsten-molybdenum carbides as automobile exhaust catalysts

International Nuclear Information System (INIS)

Leclercq, L.; Daubrege, F.; Gengembre, L.; Leclercq, G.; Prigent, M.

1987-01-01

Several catalyst samples of tungsten carbide and W, Mo mixed carbides with different Mo/W atom ratios, have been prepared to test their ability to remove carbon monoxide, nitric oxide and propane from a synthetic exhaust gas simulating automobile emissions. Surface characterization of the catalysts has been performed by X-ray photoelectron spectroscopy (XPS) and selective chemisorption of hydrogen and carbon monoxide. Tungsten carbide exhibits good activity for CO and NO conversion, compared to a standard three-way catalyst based on Pt and Rh. However, this W carbide is ineffective in the oxidation of propane. The Mo,W mixed carbides are markedly different having only a very low activity. 9 refs.; 10 figs.; 5 tabs

Mechanism of pyrrhotite formation from ferric oxyhydroxide catalyst; Kokoritsu sekitan ekika shokubai no kaihatsu (Okishi suisankatetsu shokubai karano pyrrhotite seisei kyodo)

Energy Technology Data Exchange (ETDEWEB)

Tazawa, K.; Koyama, T.; Kaneko, T.; Shimasaki, K. [Nippon Brown Coal Liquefaction Co. Ltd., Tokyo (Japan)

1996-10-28

It is thought that iron-based catalysts for coal liquefaction exercise their catalytic activity by forming pyrrhotite (Fe(1-x)S). However, there are still a lot of unknown problems remained concerning the formation and agglomeration behaviors of pyrrhotite. These make a difficulty for improving the activity of iron-based catalysts. In this study, sulfiding behaviors of {alpha}-iron oxyhydroxide ({alpha}-FeOOH) and {gamma}-iron oxyhydroxide ({gamma}-FeOOH) were investigated to reveal the formation and agglomeration behaviors of pyrrhotite. It was found that pyrrhotite was easily converted from ferric oxyhydroxide catalysts having large specific surface areas at the sulfiding temperature below 250{degree}C, and fine crystallites of pyrrhotite were formed at the initial stage of sulfiding. Crystal growth of pyrrhotite at the sulfiding temperature over 350{degree}C depended on the catalyst forms. It was also found that smaller crystallites of pyrrhotite were formed from {gamma}-FeOOH than from {alpha}-FeOOH and amorphous iron oxyhydroxide. 5 refs., 7 figs., 1 tab.

Locus-specific microemulsion catalysts for sulfur mustard (HD) chemical warfare agent decontamination.

Science.gov (United States)

Fallis, Ian A; Griffiths, Peter C; Cosgrove, Terence; Dreiss, Cecile A; Govan, Norman; Heenan, Richard K; Holden, Ian; Jenkins, Robert L; Mitchell, Stephen J; Notman, Stuart; Platts, Jamie A; Riches, James; Tatchell, Thomas

2009-07-22

The rates of catalytic oxidative decontamination of the chemical warfare agent (CWA) sulfur mustard (HD, bis(2-chlororethyl) sulfide) and a range (chloroethyl) sulfide simulants of variable lipophilicity have been examined using a hydrogen peroxide-based microemulsion system. SANS (small-angle neutron scattering), SAXS (small-angle X-ray scattering), PGSE-NMR (pulsed-gradient spin-echo NMR), fluorescence quenching, and electrospray mass spectroscopy (ESI-MS) were implemented to examine the distribution of HD, its simulants, and their oxidation/hydrolysis products in a model oil-in-water microemulsion. These measurements not only present a means of interpreting decontamination rates but also a rationale for the design of oxidation catalysts for these toxic materials. Here we show that by localizing manganese-Schiff base catalysts at the oil droplet-water interface or within the droplet core, a range of (chloroethyl) sulfides, including HD, spanning some 7 orders of octanol-water partition coefficient (K(ow)), may be oxidized with equal efficacy using dilute (5 wt. % of aqueous phase) hydrogen peroxide as a noncorrosive, environmentally benign oxidant (e.g., t(1/2) (HD) approximately 18 s, (2-chloroethyl phenyl sulfide, C(6)H(5)SCH(2)CH(2)Cl) approximately 15 s, (thiodiglycol, S(CH(2)CH(2)OH)(2)) approximately 19 s {20 degrees C}). Our observations demonstrate that by programming catalyst lipophilicity to colocalize catalyst and substrate, the inherent compartmentalization of the microemulsion can be exploited to achieve enhanced rates of reaction or to exert control over product selectivity. A combination of SANS, ESI-MS and fluorescence quenching measurements indicate that the enhanced catalytic activity is due to the locus of the catalyst and not a result of partial hydrolysis of the substrate.

Synthesis and properties of catalysts prepared from silicomolybdovanadium heteropoly acid

International Nuclear Information System (INIS)

Chumachenko, N.N.; Tarasova, D.V.; Nikoro, T.A.; Yaroslavtseva, I.V.

1984-01-01

Catalytic properties of samples prepared of silicomolybdovanadium heteropoly acid (HPA) have been investigated. The massive catalyst is shown to be comparatively low effective in the reaction of acrolein oxidation to acrylic acid. Impregnation of coarse-dispersed silica gel by the HPA solution results in the formation of active and selective catalyst, whereas low-active catalyst of deep oxidation is formed on the base of high-dispersed silica gel. The obtained data are explained by the formation and stabilization of different forms of vanadium- and molybdenum-containing compounds on the carrier surface

A real support effect on the hydrodeoxygenation of methyl oleate by sulfided NiMo catalysts

NARCIS (Netherlands)

Coumans, A.E.; Hensen, E.J.M.

2017-01-01

The effect of the support on the catalytic performance of sulfided NiMo in the hydrodeoxygenation of methyl oleate as a model compound for triglyceride upgrading to green diesel was investigated. NiMo sulfides were prepared by impregnation and sulfidation on activated carbon, silica, γ-alumina and

Hydrodeoxygenation of water-insoluble bio-oil to alkanes using a highly dispersed Pd-Mo catalyst.

Science.gov (United States)

Duan, Haohong; Dong, Juncai; Gu, Xianrui; Peng, Yung-Kang; Chen, Wenxing; Issariyakul, Titipong; Myers, William K; Li, Meng-Jung; Yi, Ni; Kilpatrick, Alexander F R; Wang, Yu; Zheng, Xusheng; Ji, Shufang; Wang, Qian; Feng, Junting; Chen, Dongliang; Li, Yadong; Buffet, Jean-Charles; Liu, Haichao; Tsang, Shik Chi Edman; O'Hare, Dermot

2017-09-19

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.Bio-oil is a potential major source of renewable fuels and chemicals. Here, the authors report a palladium-molybdenum mixed catalyst for the selective hydrodeoxygenation of water-insoluble bio-oil to mixtures of alkanes with high carbon yield.

The behavior of molybdenum and its isotopes across the chemocline and in the sediments of sulfidic Lake Cadagno, Switzerland

DEFF Research Database (Denmark)

Dahl, Tais W.; Anbar, Ariel D.; Gordon, Gwyneth W.

2010-01-01

scavenging of Mo when buried into sulfidic sediments. This paper contains the first complete suite of Mo isotope fractionation observations in a sulfidic water column and sediment system, the meromictic Lake Cadagno, Switzerland, a small alpine lake with a pronounced oxygen-sulfide transition reaching up...

Comparison of Tungsten and Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Oleic Acid

NARCIS (Netherlands)

Hollak, S.A.W.; Gosselink, R.J.A.; Es, van D.S.; Bitter, J.H.

2013-01-01

Group 6 (W, Mo) metal carbide catalysts are promising alternatives to hydrodesulfurization (NiMo, CoMo) catalysts and group 10 (Pd) type catalysts in the deoxygenation of vegetable fats/oils. Herein, we report a comparison of carbon nanofiber-supported W2C and Mo2C catalysts on activity,

Vapor deposition of molybdenum oxide using bis(ethylbenzene) molybdenum and water

International Nuclear Information System (INIS)

Drake, Tasha L.; Stair, Peter C.

2016-01-01

Three molybdenum precursors—bis(acetylacetonate) dioxomolybdenum, molybdenum isopropoxide, and bis(ethylbenzene) molybdenum—were tested for molybdenum oxide vapor deposition. Quartz crystal microbalance studies were performed to monitor growth. Molybdenum isopropoxide and bis(ethylbenzene) molybdenum achieved linear growth rates 0.01 and 0.08 Å/cycle, respectively, using atomic layer deposition techniques. Negligible MoO_x growth was observed on alumina powder using molybdenum isopropoxide, as determined by inductively coupled plasma optical emission spectroscopy. Bis(ethylbenzene) molybdenum achieved loadings of 0.5, 1.1, and 1.9 Mo/nm"2 on alumina powder after one, two, and five cycles, respectively, using atomic layer deposition techniques. The growth window for bis(ethylbenzene) molybdenum is 135–150 °C. An alternative pulsing strategy was also developed for bis(ethylbenzene) molybdenum that results in higher growth rates in less time compared to atomic layer deposition techniques. The outlined process serves as a methodology for depositing molybdenum oxide for catalytic applications. All as-deposited materials undergo further calcination prior to characterization and testing.

Spent catalyst waste management. A review. Part 1. Developments in hydroprocessing catalyst waste reduction and use

Energy Technology Data Exchange (ETDEWEB)

Marafi, M.; Stanislaus, A. [Petroleum Refining Department, Petroleum Research and Studies Center, Kuwait Institute for Scientific Research, P.O. Box 24885, 13109-Safat (Kuwait)

2008-04-15

Solid catalysts containing metals, metal oxides or sulfides, which play a key role in the refining of petroleum to clean fuels and many other valuable products, become solid wastes after use. In many refineries, the spent catalysts discarded from hydroprocessing units form a major part of these solid wastes. Disposal of spent hydroprocessing catalysts requires compliance with stringent environmental regulations because of their hazardous nature and toxic chemicals content. Various options such as minimizing spent catalyst waste generation by regeneration and reuse, metals recovery, utilization to produce useful materials and treatment for safe disposal, could be considered to deal with the spent catalyst environmental problem. In this paper, information available in the literature on spent hydroprocessing catalyst waste reduction at source by using improved more active and more stable catalysts, regeneration, rejuvenation and reuse of deactivated catalysts in many cycles, and reusing in other processes are reviewed in detail with focus on recent developments. Available methods for recycling of spent hydroprocessing catalysts by using them as raw materials for the preparation of active new catalysts and many other valuable products are also reviewed. (author)

Magnetic MoS2 on multiwalled carbon nanotubes for sulfide sensing.

Science.gov (United States)

Li, Chunxiang; Zhang, Dan; Wang, Jiankang; Hu, Pingan; Jiang, Zhaohua

2017-07-04

A novel hybrid metallic cobalt insided in multiwalled carbon nanotubles/molybdenum disulfide (Co@CNT/MoS 2 ) modified glass carbon electrode (GCE) was fabricated with a adhesive of Nafion suspension and used as chemical sensors for sulfide detection. Single-layered MoS 2 was coated on CNTs through magnetic traction force between paramagnetic monolayer MoS 2 and Co particles in CNTs. Co particles faciliated the collection of paramagnetic monolayer MoS 2 exfoliated from bulk MoS 2 in solution. Amperometric analysis, cycle voltammetry, cathodic stripping analysis and linear sweep voltammetry results showed the Co@CNT/MoS 2 modified GCE exhibited excellent electrochemical activity to sulfide in buffer solutions, but amperometric analysis was found to be more sensitive than the other methods. The amperometric response result indicated the Co@CNT/MoS 2 -modified GCE electrode was an excellent electrochemical sensor for detecting S 2- with a detection limit of 7.6 nM and sensitivity of 0.23 mA/μM. The proposed electrode was used for the determination of sulfide levels in hydrogen sulfide-pretreated fruits, and the method was also verified with recovery studies. Copyright © 2017 Elsevier B.V. All rights reserved.

Report on the research achievements in the Sunshine Project in fiscal 1992. Studies on a direct gasification catalyst; 1992 nendo chokusetsu ekika shokubai ni kansuru kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1993-10-01

This paper describes the research achievements in the Sunshine Project in fiscal 1992 in studies on a direct gasification catalyst. The paper summarizes the points where the catalyst research has reached to date. The catalyst surface effective for hydrogenation is the metal surface that can dissociate hydrogen. However, metals having large adsorption heat against hydrogen do not show the activity greatly because these metals are difficult of desorbing hydrogen having high dissociating activity. The coal liquefaction system has the surface oxidized by water content, wherein hydrogen dissociation cannot be expected, and sulfides are suitable. When a sulfide catalyst contacts hydrogen, the catalyst itself is desulfurized, producing H{sub 2}S and becomes a low-order sulfide. When atmospheric H{sub 2}S contacts this sulfide, it dissociates into HS and H, and this H behaves as active hydrogen. However, the liquefaction activity can be recognized even in a sulfuric acid type catalyst containing no sulfide whatsoever, wherein the H{sub 2}S partial pressure in the reaction system becomes extremely low. This fact means that the active hydrogen is not necessarily generated by the dissociation of H{sub 2}S. There is no other way but to think that hydrogen is dissociated directly without going through H{sub 2}S. If this is true, it provides a new guideline in developing and designing the future catalysts. (NEDO)

Boron-dependency of molybdenum boride electrocatalysts for the hydrogen evolution reaction

International Nuclear Information System (INIS)

Park, Hyounmyung; Encinas, Andrew; Fokwa, Boniface P.T.; Scheifers, Jan P.; Zhang, Yuemei

2017-01-01

Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo_2B, α-MoB, β-MoB, and MoB_2 by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB_2 and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo_2C phases, while the molybdenum richest phase Mo_2B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB_2 and β-MoB show long-term cycle stability in acidic solution. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Boron-dependency of molybdenum boride electrocatalysts for the hydrogen evolution reaction

Energy Technology Data Exchange (ETDEWEB)

Park, Hyounmyung; Encinas, Andrew; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Department of Chemical and Environmental Engineering, University of California, Riverside, CA (United States); Scheifers, Jan P.; Zhang, Yuemei [Department of Chemistry, University of California, Riverside, CA (United States)

2017-05-08

Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo{sub 2}B, α-MoB, β-MoB, and MoB{sub 2} by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB{sub 2} and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo{sub 2}C phases, while the molybdenum richest phase Mo{sub 2}B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB{sub 2} and β-MoB show long-term cycle stability in acidic solution. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Petroleum residue upgrading with dispersed catalysts: Part 2. Effect of operating conditions

Energy Technology Data Exchange (ETDEWEB)

Panariti, N.; Del Bianco, A.; Del Piero, G. [ENITECNOLOGIE S.p.A, Via Maritano 26, 20097 San Donato Mil (Italy); Marchionna, M. [SNAMPROGETTI S.p.A, Via Maritano 26, 20097 San Donato Mil (Italy); Carniti, P. [Universita degli Studi di Milano, Dip. Chimica Fisica ed Elettrochimica, Via Celoria 20, Milan (Italy)

2000-12-04

The hydrotreatment of a petroleum residue in the presence of dispersed molybdenite was carried out within a wide range of operating conditions and catalyst loading. The effect of reaction severity as well as of molybdenum concentration on product distribution and quality was studied. Based on the experimental results, a simplified reaction scheme was proposed. The hydroprocessing of the residue was described in terms of the competition between two reactions: the direct conversion of the feedstock to distillate and coke, and the catalytic hydrogenation. Compared to thermal conditions, the presence of dispersed molybdenite controls very well coke formation; however, a trend of increasing formation of solids was observed at high catalyst concentrations. The overall upgrading of the feedstock requires significant amounts of molybdenum as well as relatively high hydrogen pressure.

Synthesis and superconductivity of molybdenum cluster compounds (Chevrel phase)

International Nuclear Information System (INIS)

Culetto, F.J.

1979-05-01

The discovery of superconductivity in ternary molybdenum sulfides (Chevrel phases) in 1972 has stimulated research on these compounds. Some of the phases show extremely high critical fields Hc 2 and might therefore find technical application as high field superconductors. In order to understand the electron-phonon-interaction in these substances, measurements of the superconducting isotope effect in 92-100 Mo 6 Se 8 , Mo 6 76-82 Se 8 , and 116-124 SnMo 6 S 8 have been performed. The corresponding isotope effect exponents β (βmo=0.27 +- 0.04, βSe=0.27 +- 0.05 and βSn 6 Se 8 . In case of the ternary Chevrel phase SnMo 6 S 8 , phonon modes connected with displacements of the Sn-ions have only minor influence on the transition temperature. This result can be explained by the weak overlap of the molybdenum dsub(x)2sub(-y)2 - orbitals with Sn-sites. Furthermore, we report experiments on the synthesis of new Chevrel phase materials. In order to optimize the valence electron concentration in some ternary molybdenum selenide compounds, chalcogen exchange reactions have been performed. A new Chevrel phase superconductor, Cusub(x)Mo 6 S 6 J 2 with x=0 - 1.2, has been synthesized by copper diffusion into the non occupied channels running between the Mo 6 S 6 J 2 -'molecules' of Mo 6 S 6 J 2 . (orig.)

Organic-mineral binder for molybdenum concentrate granulation

International Nuclear Information System (INIS)

Guro, Vitaliy P.; Ibragimova, Matluba A.; Safarov, Edgorjon T.

2016-01-01

Process of pyrite cinders production from Mo middlings consists of molybdenite concentrate granulation, firing to oxidize sulfide minerals and to recover Re-oxide. If kaolin binder is used a pyrite cinders dilution with Mo takes place. So, the development of organic binding agents, alternative to kaolin, is an actual issue. The approach is based on the comparison of the hydrophilic, strength and technological features of the hydrometallurgical processing of pellets. The new batch is developed. It differs from the traditional mixture by polymer burning and minimizing Mo dilution, thus aiming to maximize Re, Au, Ag recovery. The composition of the new organic-mineral batch is as follows: 97.3 % of molybdenite concentrate, 2 % of kaolin and 0.7 % of SK polymer. Keywords: molybdenum middlings, binder, organic additive, batch, granulation.

Atomic layer deposition of molybdenum disulfide films using MoF ₆ and H ₂ S

Energy Technology Data Exchange (ETDEWEB)

Mane, Anil U. [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439; Letourneau, Steven [Micron School of Materials Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho 83725; Mandia, David J. [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439; Liu, Jian [Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208; Libera, Joseph A. [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439; Lei, Yu [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439; Peng, Qing [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439; Graugnard, Elton [Micron School of Materials Science and Engineering, Boise State University, 1910 University Dr., Boise Idaho 83725; Elam, Jeffrey W. [Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, Illinois 60439

2018-01-01

Molybdenum sulfide films were grown by atomic layer deposition on silicon and fused silica substrates using molybdenum hexafluoride (MoF6) and hydrogen sulfide at 200 degrees C. In situ quartz crystal microbalance (QCM) measurements confirmed linear growth at 0.46 angstrom/cycle and self-limiting chemistry for both precursors. Analysis of the QCM step shapes indicated that MoS2 is the reaction product, and this finding is supported by x-ray photoelectron spectroscopy measurements showing that Mo is predominantly in the Mo(IV) state. However, Raman spectroscopy and x-ray diffraction measurements failed to identify crystalline MoS2 in the as-deposited films, and this might result from unreacted MoFx residues in the films. Annealing the films at 350 degrees C in a hydrogen rich environment yielded crystalline MoS2 and reduced the F concentration in the films. Optical transmission measurements yielded a bandgap of 1.3 eV. Finally, the authors observed that the MoS2 growth per cycle was accelerated when a fraction of the MoF6 pulses were substituted with diethyl zinc. Published by the AVS

Spectroscopy, microscopy and theoretical study of NO adsorption on MoS2 and Co-Mo-S hydrotreating catalysts

DEFF Research Database (Denmark)

Topsøe, Nan-Yu; Tuxen, Anders Kyrme; Hinnemann, Berit

2011-01-01

nfrared (IR) spectroscopy using NO as a probe molecule has been one of the important methods for characterizing hydrotreating catalysts, since this technique provides information on the nature and quantity of active edge sites of these catalysts. However, due to the strong adsorption of NO, which......) calculations, we present new atomic-scale insight into the nature of NO adsorption on MoS2 and Co-Mo-S nanoclusters. The DFT calculations and STM experiments show that NO does not adsorb at fully sulfided MoS2 edges not containing hydrogen. However, typical sulfided catalysts will have hydrogen present...... NO as a probe molecule to obtain detailed atomic-scale information on hydrotreating catalysts and the origins of activity differences. (C) 2011 Published by Elsevier Inc....

Nanoscal design of molybdenum sulfides for more efficient electro- and photoelectrocatalytic hydrogen evolution

DEFF Research Database (Denmark)

Laursen, Anders Bo

above. These catalysts were studied on titania protected silicon photocathodes. These showed an excellent activity and demonstrated the potential of these electrodes for sustainable H2 production without the use of Pt. Electrodes using MoS2 as both the protection layer and the catalyst were also...... investigated. The full potential of these electrodes could not be realized due to time constraints, given the severe limitations in the electron transport across the protection layer. Regardless, these electrodes showed superior stability to the titania protected photoelectrodes. It was attempted to improve...... the electron transport through the catalyst layers by synthesizing composites of carbon nanotubes and MoSx. The syntheses included both electro-co-deposition and electrodeposition on a pre-fabricated nanotube film. No improvement could consistently be detected in these experiments. Hence, MoS3 was coated...

A Polyoxovanadate-Resorcin[4]arene-Based Porous Metal-Organic Framework as an Efficient Multifunctional Catalyst for the Cycloaddition of CO2 with Epoxides and the Selective Oxidation of Sulfides.

Science.gov (United States)

Lu, Bing-Bing; Yang, Jin; Liu, Ying-Ying; Ma, Jian-Fang

2017-10-02

In this work, we report a new polyoxovanadate-resorcin[4]arene-based metal-organic framework (PMOF), [Co 2 L 0.5 V 4 O 12 ]·3DMF·5H 2 O (1), assembled with a newly functionalized wheel-like resorcin[4]arene ligand (L). 1 features an elegant porous motif and represents a rare example of PMOFs composed of both a resorcin[4]arene ligand and polyoxovanadate. Remarkably, 1 shows open V sites in the channel, which makes 1 an efficient heterogeneous Lewis acid catalyst for the cycloaddition of carbon dioxide to epoxides with high conversion and selectivity. Strikingly, 1 also exhibits high catalytic activity for the heterogeneous oxidative desulfurization of sulfides. Particularly, the heterogeneous catalyst 1 can be easily separated and reused with good catalytic activity.

Controllable synthesis of hierarchical nickel cobalt sulfide with enhanced electrochemical activity

Science.gov (United States)

Tie, Jinjin; Han, Jiaxi; Diao, Guiqiang; Liu, Jiwen; Xie, Zhuopeng; Cheng, Gao; Sun, Ming; Yu, Lin

2018-03-01

The composition of nickel cobalt sulfide has great influence on its electrochemical performance. Herein, the nickel cobalt sulfide with different composition and mixed phase were synthesized by one-step solvothermal method through changing the molar ratio of Ni to Co in the reaction system. The electrochemical measurements showed that the nickel cobalt sulfide with a theoretical molar ratio of Ni/Co to be 1.5:1.5 (NCS-2) demonstrates the superior pseudocapacitive performance with a high specific capacitance (6.47 F cm-2 at 10 mA cm-2) and a favorable Coulombic efficiency (∼99%). Whereas, when applied as the catalyst for hydrogen evolution reaction in 1 M KOH aqueous electrolyte, the nickel cobalt sulfide with a theoretical molar ratio of Ni/Co is 1:2 (NCS-1) displays better catalytic activity, and it requires a relatively lower overpotential of 282 mV to deliver the current density of 10 mA cm-2.

Cobalt oxide-molybdenum oxide-aluminum oxide catalyst : II. The structure of the catalyst

NARCIS (Netherlands)

Lipsch, J.M.J.G.; Schuit, G.C.A.

1969-01-01

The structure of the \\"Co molybdate on alumina\\" catalyst was investigated. Infrared spectra show that the Mo is present as MoO3. Reflection spectra lead to the conclusion that the Co is distributed throughout the bulk of the alumina as CoAl2O4, whereas the MoO3 is spread over the carrier surface,

Continuous bench-scale slurry catalyst testing direct coal liquefaction rawhide sub-bituminous coal

Energy Technology Data Exchange (ETDEWEB)

Bauman, R.F.; Coless, L.A.; Davis, S.M. [and others

1995-12-31

In 1992, the Department of Energy (DOE) sponsored research to demonstrate a dispersed catalyst system using a combination of molybdenum and iron precursors for direct coal liquefaction. This dispersed catalyst system was successfully demonstrated using Black Thunder sub-bituminous coal at Wilsonville, Alabama by Southern Electric International, Inc. The DOE sponsored research continues at Exxon Research and Development Laboratories (ERDL). A six month continuous bench-scale program using ERDL`s Recycle Coal Liquefaction Unit (RCLU) is planned, three months in 1994 and three months in 1995. The initial conditions in RCLU reflect experience gained from the Wilsonville facility in their Test Run 263. Rawhide sub-bituminous coal which is similar to the Black Thunder coal tested at Wilsonville was used as the feed coal. A slate of five dispersed catalysts for direct coal liquefaction of Rawhide sub-bituminous coal has been tested. Throughout the experiments, the molybdenum addition rate was held constant at 100 wppm while the iron oxide addition rate was varied from 0.25 to 1.0 weight percent (dry coal basis). This report covers the 1994 operations and accomplishments.

Heterogeneous inhibition of the liquid phase oxidation of hydrocarbons by molybdenum compounds

Energy Technology Data Exchange (ETDEWEB)

Tavadyan, L.A.; Karapetyan, A.P.; Madatovyan, V.M.

1988-05-01

The heterogeneous action of molybdenum compounds: MoB, MoSe/sub 2/, MoSi/sub 2/, Mo/sub 2/C, MoO/sub 3/, Mo on the oxidation of n-decane, ethylbenzene, and nonene-1 has been investigated. A parameter representing the inhibiting effect of the heterogeneous catalyst was calculated theoretically. It was found that NoB, MoSe/sub 2/, and MoSi/sub 2/ inhibited the oxidation of n-decane at 408 K while the remaining heterogeneous contacts catalyzed it. A critical phenomenon was detected in the inhibition by MoSi/sub 2/. All the molybdenum compounds investigated inhibited the oxidation of ethylbenzene at 393 K owing to the formation of phenol by catalytic decomposition of the hydroperoxide. The liquid phase oxidation autoinhibited by phenol is described theoretically.

Catalyst dispersion and activity under conditions of temperature-staged liquefaction

Energy Technology Data Exchange (ETDEWEB)

Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

1993-02-01

This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275[degrees]C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

Process for the regeneration of metallic catalysts

Science.gov (United States)

Katzer, James R.; Windawi, Hassan

1981-01-01

A method for the regeneration of metallic hydrogenation catalysts from the class consisting of Ni, Rh, Pd, Ir, Pt and Ru poisoned with sulfur, with or without accompanying carbon deposition, comprising subjecting the catalyst to exposure to oxygen gas in a concentration of about 1-10 ppm. intermixed with an inert gas of the group consisting of He, A, Xe, Kr, N.sub.2 and air substantially free of oxygen to an extent such that the total oxygen molecule throughout is in the range of about 10 to 20 times that of the hydrogen sulfide molecular exposure producing the catalyst poisoning while maintaining the temperature in the range of about 300.degree. to 500.degree. C.

Transition-Metal-Free Highly Efficient Aerobic Oxidation of Sulfides to Sulfoxides under Mild Conditions

Directory of Open Access Journals (Sweden)

Hua Zhang

2009-12-01

Full Text Available A highly efficient transition-metal-free catalytic system Br2/NaNO2/H2O has been developed for a robust and economic acid-free aerobic oxidation of sulfides. It is noteworthy that the sulfide function reacts under mild conditions without over-oxidation to sulfone. The role of NaNO2as an efficient NO equivalent for the activation of molecular oxygen was identified. Under the optimal conditions, a broad range of sulfide substrates were converted into their corresponding sulfoxides in high yields by molecular oxygen. The present catalytic system utilizes cheap and readily available agents as the catalysts, exhibits high selectivity for sulfoxide products and releases only innocuous water as the by-products.

Role of non-ferrous coal minerals and by-product metallic wastes in coal liquefaction. Technical progress report, March 1, 1981-May 31, 1981

Energy Technology Data Exchange (ETDEWEB)

Garg, D.; Givens, E.N.; Schweighardt, F.K.; Curtis, C.W.; Guin, J.A.; Huang, W.J.; Shridharani, K.

1981-06-01

This report covers results from both tubing-bomb experiments and continuous PDU runs. The following materials were evaluated in the PDU on Elkhorn No. 2 coal from Floyd County, Kentucky: Molybdic oxides; iron oxide; pyrite; pyrite/iron oxide mixture, and iron sulfate impregnation. A base case liquefaction run was also made for direct comparison. All of the above materials were examined at both 825 and 850/sup 0/F. Tubing-bomb experiments are reported on pyrite, red mud, sodium sulfide and organic compounds of cobalt, nickel, molybdenum, zinc, chromium and lead. Significant conclusions were drawn on the catalysis by different materials. Especially significant was the higher level of activity resulting from impregnation versus particle incorporation of the catalyst in the system. Impregnation of coal decreased the hydrocarbon gases yield and increased oil yield. Hydrogen consumption was significantly reduced by impregnation. Addition of molybdic oxide containing 90% MoO/sub 3/ and 10% silica to coal liquefaction reaction mixture had the following effect: coal conversion increased, oil yield increased by more than a factor of two at both temperatures, hydrogen consumption increased, solvent/oil fraction showed substantial increase in hydrogen content, and molybdenum in the resulting liquefaction residue was apparently transformed into an amorphous material. A more thorough evaluation of completely sulfided molybdenum will be made to see if its activity increases. In the tubing-bomb experiments organic compound of molybdenum showed the highest activity for coal conversion and oil production. Significant synergism was noted between red mud and sodium sulfide in the coal liquefaction reaction.

Aromatic hydrocarbon production via eucalyptus urophylla pyrolysis over several metal modified ZSM-5 catalysts – an analysis by py-GC/MS

Science.gov (United States)

Metal modified HZSM-5 catalysts were prepared by ion exchange of NH4ZSM-5 (SIO2/Al2O3 = 23) using gallium, molybdenum, nickel and zinc, and their combinations thereof. The prepared catalysts were used to evaluate catalytic pyrolysis for the conversion of Eucalyptus urophylla to fuels and chemicals, ...

The Effect of gamma-Al2O3, TiO2, and ZrO2 Supports on Hydrodesulfurization Activity of Transition-Metal Sulfides

Czech Academy of Sciences Publication Activity Database

Kaluža, Luděk; Zdražil, Miroslav

2008-01-01

Roč. 73, 8-9 (2008), s. 945-955 ISSN 0010-0765 R&D Projects: GA ČR GP104/06/P034 Institutional research plan: CEZ:AV0Z40720504 Keywords : hydrodesulfurization * transition metal sulfides * sulfide catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.784, year: 2008

Report on the achievements in the Sunshine Project in fiscal 1992 on research and development of coal energy. Studies on coal liquefying catalysts and a method for analyzing liquefied oil; 1992 nendo sekitan ekikayo shokubai oyobi ekikayu bunsekiho no kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1983-03-01

This paper describes the achievements in the Sunshine Project in fiscal 1992 on research of coal liquefying catalysts and a method for analyzing liquefied oil. Oxidative regeneration was performed on an Ni-W based waste catalyst used in reforming (hydrogenating) coal liquefied light oil fraction. If the regeneration can be done with low oxygen partial pressure and step-wise temperature rise, the activity after the regeneration can be restored to the level of a new catalyst, with sulfate production being suppressed. Model reaction was discussed by changing the amount of W and Mo carried by alumina. Suppressing the carrying amount can control the hydrogenation activity and the hydrogenating decomposition activity. Comparison was given on compositions of woods and such hydrogenation products as peat and coal. Analysis was performed on composition of the circulating solvent used in the NEDO bituminous coal liquefying PSU. In the initial stage of the operation, the solvent had higher concentrations in the groups of compounds not having alkyl groups, and compounds having the alkyl groups increased in the end of the operation. Discussions were given also on index materials to control the operation of solvent hydrogenating process. Efficient preparation conditions were discussed on an iron sulfide particulate catalyst that utilizes surface reaction of a solid metal while mechanical impact such as vibration is being given. Effects of the catalyst concentration in coal liquefaction were experimented by using oil soluble molybdenum, wherein no change was found in the reaction mechanism. (NEDO)

Catalyst dispersion and activity under conditions of temperature-staged liquefaction. Final report

Energy Technology Data Exchange (ETDEWEB)

Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

1993-02-01

This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275{degrees}C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

Hydrogen-water deuterium exchange over metal oxide promoted nickel catalysts

Energy Technology Data Exchange (ETDEWEB)

Sagert, N H; Shaw-Wood, P E; Pouteau, R M.L. [Atomic Energy of Canada Ltd., Pinawa, Manitoba. Whiteshell Nuclear Research Establishment

1975-11-01

Specific rates have been measured for hydrogen-water deuterium isotope exchange over unsupported nickel promoted with about 20% of various metal oxides. The oxides used were Cr/sub 2/O/sub 3/, MoO/sub 2/, MnO, WO/sub 2/-WO/sub 3/, and UO/sub 2/. Nickel surface areas, which are required to measure the specific rates, were determined by hydrogen chemisorption. Specific rates were measured as a function of temperature in the range 353 to 573 K and as a function of the partial pressure of hydrogen and water over a 10-fold range of partial pressure. The molybdenum and tungsten oxides gave the highest specific rates, and manganese and uranium oxides the lowest. Chromium oxide was intermediate, although it gave the highest rate per gram of catalyst. The orders with respect to hydrogen and water over molybdenum oxide and tungsten oxide promoted nickel were consistent with a mechanism in which nickel oxide is formed from the reaction of water with the catalyst, and then is reduced by hydrogen. Over manganese and uranium oxide promoted catalysts, these orders are consistent with a mechanism in which adsorbed water exchanges with chemisorbed hydrogen atoms on the nickel surface. Chromium oxide is intermediate. It was noted that those oxides which favored the nickel oxide route had electronic work functions closest to those of metallic nickel and nickel oxide.

The Synthesis and Electrocatalytic Activities of Molybdenum Sulfide for Hydrogen Evolution Reaction

KAUST Repository

Li, Zhengxing

2014-01-01

of the Pt-group metals for HER. Plenty of researches have been conducted for improving the HER activities of MoS2 by optimizing its synthesis method. However, it remains challenging to prepare MoS2 catalysts with high and controllable activity, and more

The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

Directory of Open Access Journals (Sweden)

Jakob G. Howalt

2014-01-01

Full Text Available The presence of water often gives rise to oxygen adsorption on catalyst surfaces through decomposition of water and the adsorbed oxygen or hydroxide species often occupy important surfaces sites, resulting in a decrease or a total hindrance of other chemical reactions taking place at that site. In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free energy profile for electrochemical protonation of O and N2 species on cuboctahedral Mo13 nanoclusters. The calculations show that the molybdenum nanocluster will preferentially bind oxygen over nitrogen and hydrogen at neutral bias, but under electrochemical reaction conditions needed for nitrogen reduction, oxygen adsorption is severely weakened and the adsorption energy is comparable to hydrogen and nitrogen adsorption. The potentials required to reduce oxygen off the surface are −0.72 V or lower for all oxygen coverages studied, and it is thus possible to (reactivate (partially oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface and electrochemical ammonia production via the associative mechanism is possible at potentials as low as −0.45 V to −0.7 V.

Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol

Directory of Open Access Journals (Sweden)

Khalid Khazzal Hummadi

2009-06-01

Full Text Available The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK, 10 atm (1013 kPa, with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a commercial catalyst; maximum selectivity (82.3% was obtained at 573oK when the conversion was 59.7%. Catalysts prepared by reacting iron (III and molybdate by kneading or precipitation followed by evaporation, omitting a filtration stage, were less active and less selective. The selectivity-activity relationships of these catalysts as a function of temperature were discussed in relation to the method of preparation, surface areas and composition. By combing this catalytic data with data from the patent literature we demonstrate a synergy between iron and molybdenum in regard to methanol oxidation to formaldehyde; the optimum composition corresponded to an iron mole fraction 0.2-0.3. The selectivity to formaldehyde was practically constant up to an iron mole fraction 0.3 and then decreased at higher iron concentrations. The iron component can be regarded as the activity promoter. The iron molybdate catalysts can thus be related to other two-component MoO3-based selective oxidation catalysts, e.g. bismuth and cobalt molybdates. The iron oxide functions as a relatively basic oxide abstracting, in the rate-controlling step, a proton from the methyl of a bound methoxy group of chemisorbed methanol. It was proposed that a crucial feature of the sought after iron(III molybdate catalyst is the presence of -O-Mo-O-Fe-O-Mo-O- groups as found in the compound Fe2(MoO43 and for Fe3+ well dispersed in MoO3 generally. At the higher iron(III concentrations the loss of

Evaluation of oxide dispersion strengthened (ODS) molybdenum and molybdenum-rhenium alloys

International Nuclear Information System (INIS)

Mueller, A.J.; Bianco, R.; Buckman, R.W. Jr.

1999-01-01

Oxide dispersion strengthened (ODS) molybdenum alloys being developed for high temperature applications possess excellent high temperature strength and creep resistance. In addition they exhibit a ductile-to-brittle transition temperature (DBIT) in the worked and stress-relieved condition under longitudinal tensile load well below room temperature. However, in the recrystallized condition, the DBTT maybe near or above room temperature, depending on the volume fraction of oxide dispersion and the amount of prior work. Dilute rhenium additions (7 and 14 wt.%) to ODS molybdenum were evaluated to determine their effect on low temperature ductility. The addition of 7 wt.% rhenium to the ODS molybdenum did not significantly enhance the mechanical properties. However, the addition of 14 wt.% rhenium to the ODS molybdenum resulted in a DBTT well below room temperature in both the stress-relieved and recrystallized condition. Additionally, the tensile strength of ODS Mo-14Re is greater than the base ODS molybdenum at 1,000 to 1,250 C

Mechanism of hydrodenitrogenation on phosphides and sulfides.

Science.gov (United States)

Oyama, S Ted; Lee, Yong-Kul

2005-02-17

The mechanism of hydrodenitrogenation (HDN) of 2-methylpiperidine was studied over a silica-supported nickel phosphide catalyst (Ni2P/SiO2, Ni/P = 1/2) and a commercial Ni-Mo-S/Al2O3 catalyst in a three-phase trickle-bed reactor operated at 3.1 MPa and 450-600 K. Analysis of the product distribution as a function of contact time indicated that the reaction proceeded in both cases predominantly by a substitution mechanism, with a smaller contribution of an elimination mechanism. Fourier transform infrared spectroscopy (FTIR) of the 2-methylpiperidine indicated that at reaction conditions a piperidinium ion intermediate was formed on both the sulfide and the phosphide. It is concluded that the mechanism of HDN on nickel phosphide is very similar to that on sulfides. The mechanism on the nickel phosphide was also probed by comparing the reactivity of piperidine and several of its derivatives in the presence of 3000 ppm S. The relative elimination rates depended on the structure of the molecules, and followed the sequence: 4-methylpiperidine approximately piperidine > 3-methylpiperidine > 2,6-dimethylpiperidine > 2-methylpiperidine. [Chemical structure: see text] This order of reactivity was not dependent on the number of alpha-H or beta-H atoms in the molecules, ruling out their reaction through a single, simple mechanism. It is likely that the unhindered piperidine molecules reacted by an S(N)2 substitution process and the more hindered 2,6-dimethylpiperidine reacted by an E2 elimination process.

Coking of residue hydroprocessing catalysts

Energy Technology Data Exchange (ETDEWEB)

Gray, M.R.; Zhao, Y.X. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical Engineering; McKnight, C.A. [Syncrude Canada Ltd., Edmonton, AB (Canada); Komar, D.A.; Carruthers, J.D. [Cytec Industries Inc., Stamford, CT (United States)

1997-11-01

One of the major causes of deactivation of Ni/Mo and Co/Mo sulfide catalysts for hydroprocessing of heavy petroleum and bitumen fractions is coke deposition. The composition and amount of coke deposited on residue hydroprocessing catalysts depends on the composition of the liquid phase of the reactor. In the Athabasca bitumen, the high molecular weight components encourage coke deposition at temperatures of 430 to 440 degrees C and at pressures of 10 to 20 MPa hydrogen pressure. A study was conducted to determine which components in the heavy residual oil fraction were responsible for coking of catalysts. Seven samples of Athabasca vacuum residue were prepared by supercritical fluid extraction with pentane before being placed in the reactor. Carbon content and hydrodesulfurization activity was measured. It was concluded that the deposition of coke depended on the presence of asphaltenes and not on other compositional variables such as content of nitrogen, aromatic carbon or vanadium.

Effect of zirconia morphology on sulfur-resistant methanation performance of MoO3/ZrO2 catalyst

Science.gov (United States)

Liu, Chen; Wang, Weihan; Xu, Yan; Li, Zhenhua; Wang, Baowei; Ma, Xinbin

2018-05-01

Two kinds of ZrO2 support with different morphologies were prepared by facile solvothermal method in different solvents. The obtained two supports showed monoclinic zirconia (m-ZrO2) and tetragonal zirconia (t-ZrO2) phase with similar crystalline size. Their supported Mo-based catalysts were prepared by impregnation method and the effect of zirconia morphology on the performance of sulfur-resistant methanation was examined. The results indicated that the MoO3/m-ZrO2 has higher CO conversion than the MoO3/t-ZrO2 catalyst. Characterizations by XRD, Raman, H2-TPR and IR confirmed that the m-ZrO2 is superior to t-ZrO2 for dispersing molybdenum species. In addition, the MoO3/m-ZrO2 catalyst has weaker interaction between support and active Mo speices than the MoO3/t-ZrO2 catalyst, which facilitates to forming active species of nanocrystalline MoS2 layers for sulfur-resistant methanation. The weaker interaction of molybdenum species with m-ZrO2 is related with the more covalent character of the Zrsbnd O bond and more oxygen defective structure of m-ZrO2. A larger number of Lewis acid centers appear on the surface of m-ZrO2, which verified the substantial vacancies on m-ZrO2 exposing coordinately unsaturated Zr3+ and Zr4+ cations. Meanwhile, the less Lewis acid of t-ZrO2 result in stronger interaction between support and molybdenum species and trigger crystalline phase MoO3 and Mosbnd Osbnd Zr linkages.

Effect of molybdenum and chromium additions on the mechanical properties of Fe3Al-based alloys

International Nuclear Information System (INIS)

Sun Yangshan; Xue Feng; Mei Jianping; Yu Xingquan; Zhang Lining

1995-01-01

Iron aluminides based on Fe 3 Al offer excellent oxidation and sulfidation resistance, with lower material cost and density than stainless steels. However, their potential use as structural material has been hindered by limited ductility and a sharp drop in strength above 600 C. Recent development efforts have indicated that adequate engineering ductility of 10--20% and tensile yield strength of as high as 500 MPa can be achieved through control of composition and microstructure. These improved tensile properties make Fe 3 Al-based alloys more competitive against conventional austenic and ferritic steels. The improvement of high temperature mechanical properties has been achieved mainly by alloying processes. Molybdenum has been found to be one of the most important alloying elements for strengthening Fe 3 Al-based alloys at high temperatures. However, the RT(room temperature) ductility decreases with the increase of a molybdenum addition. On the other hand, a chromium addition to Fe 3 Al-based alloys is very efficient for improving RT ductility but not beneficial to yield strength at temperatures to 800 C. The purpose of the present paper is to report the effects of combined additions of molybdenum and chromium on mechanical properties at ambient temperature and high temperature of 600 C

Potentiometric determination of molybdenum

International Nuclear Information System (INIS)

Rusina, O.N.; Gorbatkova, B.Kh.

1977-01-01

Potentiometric titration by lead acetate is used to determine molybdenum in the form of molybdate ions. The behaviour of bimetallic electrode couples, i.e. tungsten-lead, platinum-lead, lead-carbon electrode, molybdenum-carbon electrode platinum-molibdenum has been investigated. The greatest jump of the potential in the finite point is observed for platinum-molybdenum electrode couple (150 mV/ml at pH 4.0-5.5). The limiting concentration of molybdenum in potentiometric titration by lead acetate is 2.8x10 -4 M. The measurements are accurate to within +-0.1%

From biomass to fuels: hydrotreating of oxygen-containing feeds on a CoMo/Al{sub 2}O{sub 3} hydrodesulfurization catalyst

Energy Technology Data Exchange (ETDEWEB)

Viljava, T.-R.

2001-07-01

Biomass is a renewable alternative to fossil raw materials in the production of liquid fuels and chemicals. Liquefied biomass contains an abundance of oxygen-containing molecules that need to be removed to improve the stability of the liquids. A hydrotreating process, hydrodeoxygenation (HDO), is used for the purpose. Hydrodeoxygenation is similar to the hydrodesulfurization (HDS) process used in oil refining, relying upon a presulfided CoMo/{gamma}-Al{sub 2}O{sub 2}; catalyst. The stability of the sulfided catalyst is critical in HDO because biocrudes usually do not contain the sulfur compounds needed to maintain the sulfidation of the catalyst. The aim of this work was to examine the role of sulfur in maintaining the activity of the HDO catalyst. Sulfur was introduced as an organic sulfur-containing co-reactant or as a sulfur substituent in an oxygen-containing reactant molecule as a way of simulating mixed feeds composed of biocrudes and conventional crudes, or it was introduced as a low molecular weight sulfiding agent. In addition, the stability of the sulfided catalyst against changes in the feed composition was studied to find out whether the activity of the catalyst could be maintained by carrying out HDO alternately with HDS. Simultaneous HDO and HDS was studied in a batch reactor with model compounds having a sulfur-containing (inercapto or inethylmercapto) and an oxygen-containing (hydroxyl or inethoxy) substituent in the same molecule, and with binary mixtures of mono-substituted benzene compounds. In both cases, the reactions of the oxygencontaining substituents were strongly suppressed as long as a sulfur-containing functionality was present. HDS reactions of inercapto and inethylinercapto groups were either enhanced or retarded in the presence of oxygen-containing functionality. HDS was enhanced when the oxygen-containing substituent was located in Para-position to the sulfur substituent thereby increasing the electronegativity of the sulfur atom and

The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

DEFF Research Database (Denmark)

Howalt, Jakob Geelmuyden; Vegge, Tejs

2014-01-01

are -0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface...... and electrochemical ammonia production via the associative mechanism is possible at potentials as low as -0.45 V to -0.7 V. © 2014 Howalt and Vegge........ In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density...

The role of reaction pathways and support interactions in the development of high activity hydrotreating catalysts

DEFF Research Database (Denmark)

Topsøe, Henrik; Hinnemann, Berit; Nørskov, Jens Kehlet

2005-01-01

structures may be present as single sulfide sheets. Thus, stacking is not an essential feature of Type II catalysts. The article illustrates how the new scientific insight has aided the introduction of the new high activity BRIM (TM) type catalysts for FCC pre-treatment and production of ultra low sulfur...... exhibiting a metallic character are observed to be involved in adsorption, hydrogenation and C-S bond cleavage. The insight is seen to provide a new framework for understanding the DDS and HYD pathways and the role of steric hindrance and poisons. Density functional theory (DFT) calculations have illustrated...... how support interactions may influence the activity of sulfided catalysts. The brim sites and the tendency to form vacancies are seen to differ in types I and II Co-Mo-S. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) studies show that the high activity Type II...

The functionalities of Pt/{gamma}-Al{sub 2}O{sub 3} catalysts in simultaneous HDS and HDA reactions

Energy Technology Data Exchange (ETDEWEB)

V.G. Baldovino-Medrano; Sonia A. Giraldo; Aristobulo Centeno [Universidad Industrial de Santander (UIS), Bucaramanga (Colombia). Centro de Investigaciones en Catalisis (CICAT)

2008-08-15

A Pt/{gamma}-Al{sub 2}O{sub 3} catalyst was tested in simultaneous hydrodesulfurization (HDS) of dibenzothiophene and hydrodearomatization (HDA) of naphthalene reactions. Samples of it were subjected to different pretreatments: reduction, reduction-sulfidation, sulfidation with pure H{sub 2}S and non-activation. The reduced catalyst presented the best performance, even comparable to that of Co(Ni)Mo catalysts. All catalyst samples were selective to the HDS reaction over HDA, and to the direct desulfurization pathway of dibenzothiophene HDS over the hydrogenation reaction pathway of HDS. The effect of H{sub 2}S partial pressure on the functionalities of the reduced Pt/{gamma}-Al{sub 2}O{sub 3} catalyst was studied. The results showed that an increase in H{sub 2}S partial pressure does not cause poisoning, but an inhibition effect, without changing the catalyst selectivity. Accordingly, the activity trends were ascribed to adsorption differences between the different reactive molecules over the same catalytic active site. TPR characterization along with a thermodynamics analysis showed that the active phase of reduced Pt/{gamma}-Al{sub 2}O{sub 3} is constituted by Pt{sup 0} particles. However, presulfidation of the catalyst leads to a mixture of PtS and Pt{sup 0}which has a negative effect on the catalytic performance without changing catalyst functionalities. 61 refs., 4 figs., 1 tab.

The behavior of molybdenum and its isotopes across the chemocline and in the sediments of sulfidic Lake Cadagno

DEFF Research Database (Denmark)

Dahl, Tais Wittchen; Anbar, Ariel; Gordon, Gwyneth

2010-01-01

Molybdenum (Mo) isotope studies in black shales can provide information about the redox evolution of the Earth’s oceans, provided the isotopic consequences of Mo burial into its major sinks are well understood. Previous applications of the Mo isotope paleo-ocean redox proxy assumed quantitative...

Molybdenum acetate like precursor of molybdenum carburized supported on alumina: a catalyst for hydrogenation reactions

International Nuclear Information System (INIS)

Petkovic, Lucia M; Parra, Ruben D; Marquez Manuel; Larsen, Gustavo

1994-01-01

The stability of the Al203 supported dimers under relatively high temperatures and hydrocarbon/H2 (carburizing) atmospheres is reported also, it has been developed a new method for Mo2 loading of the support based on the wet impregnation of the latter. Since carbided Mo is active for hydrogenations, the isobutene/H2 has been chosen as the probe reaction. Al203 supported Mo2(Ac)4 results in a catalyst active for isobutene hydrogenation after treatment with a H2/C2H6 2:1 mixture at 753 k

HDO of guaiacol over NiMo catalyst supported on activated carbon derived from castor de-oiled cake

Directory of Open Access Journals (Sweden)

Viviana Ospina

2015-05-01

Full Text Available Physical and chemical activation methods were used to prepare two different activated carbons (ACs from castor de-oiled cake. H2O/CO2 mixture was used as the physical activating agent, and for chemical activation potassium carbonate (K2CO3 was used. For both materials, textural and chemical properties were characterized by N2 adsorption–desorption isotherms, thermogravimetric analysis (TGA, Fourier Transform Infrared Spectroscopy (FTIR, thermal programmed reduction (TPR, X-ray fluorescence (XRF, and scanning electron microscopy (SEM. The ACs were used as supports for NiMo sulfide catalysts, which were prepared by wetness impregnation and in-situ sulfided for the hydrodeoxygenation (HDO of guaiacol (GUA as a model compound of bio-oil. The HDO reaction was carried out in a typical batch reactor at 5 MPa of H2 and 350 °C. Under the same test conditions, commercial catalysts were also tested in the reaction. Although the commercial catalysts displayed higher GUA conversion, the prepared catalysts showed higher activity and non-oxygenated and saturated products yield.

Dissulfeto de molibdênio, um material multifuncional e surpreendente Molybdenum disulfide, a multifunctional and remarkable material

Directory of Open Access Journals (Sweden)

Fernando Wypych

2002-02-01

Full Text Available The aim of this work is to review the chemical and physical properties of layered molybdenum disulfide. The three polymorphic/polytypic modifications of the compound were found, the polytypes 2H (molybdenite and 3R are semiconductors while the polymorph 1T is an electronic conductor. 2H-MoS2 has several important industrial applications as hydrotreatment catalysts, energy storage devices, solar cells, solid lubricants, among others. When intercalated, the 2H phase changes to a distorted 1T phase, producing unstable intercalation compounds that can be exfoliated in solution, producing single layers and consequently nanocomposites. The direct synthesis of the 1T phase produces stable intercalation compounds. Recently molybdenum disulfide was prepared as nanotubes and fulerene-like structures that bring new insights in the investigation of this important material.

Rational geometrical engineering of palladium sulfide multi-arm nanostructures as a superior bi-functional electrocatalyst.

Science.gov (United States)

Nandan, R; Nanda, K K

2017-08-31

Geometrical tunability offers sharp edges and an open-armed structure accompanied with a high electrochemical active surface area to ensure the efficient and effective utilization of materials by exposing the electrochemical active sites for facile accessibility of reactant species. Herein, we report a one-step, single-pot, surfactant-free, electroless, and economic route to synthesize palladium sulfide nanostructures with different geometries at mild temperatures and their catalytic properties towards the oxygen reduction reaction (ORR) and methanol electro-oxidation (MOR). For ORR, the positive on-set, half wave potentials, smaller Tafel slope, high electrochemical active surface area, large roughness factor, and better cyclic stability of the proposed nanostructures as compared to those of the commercial state-of-the-art Pt-C/PdS catalysts suggest their superiority in an alkaline medium. In addition, high mass activity (J f ∼ 715 mA mg -1 ), in comparison with that of the commercial state-of-the-art Pt-C/PdS catalysts (J f ∼ 138/41 mA mg -1 , respectively), and high J f /J b (1.52) along with the superior operational stability of the multi-arm palladium sulfide nanostructures towards MOR advocates the bi-functional behavior of the catalyst and its potential as a promising Pt-free anode/cathode electrocatalyst in fuel cells.

Analytic chemistry of molybdenum

International Nuclear Information System (INIS)

Parker, G.A.

1983-01-01

Electrochemical, colorimetric, gravimetric, spectroscopic, and radiochemical methods for the determination of molybdenum are summarized in this book. Some laboratory procedures are described in detail while literature citations are given for others. The reader is also referred to older comprehensive reviews of the analytical chemistry of molybdenum. Contents, abridged: Gravimetric methods. Titrimetric methods. Colorimetric methods. X-ray fluorescence. Voltammetry. Catalytic methods. Molybdenum in non-ferrous alloys. Molydbenum compounds

Molybdenum from uranium solutions

International Nuclear Information System (INIS)

Gardner, H.E.

1981-01-01

A method of removing molybdenum from a uranium bearing solution is claimed. It comprises adding sufficient reactive lead compound to supply at least 90 percent of the stoichiometric quantity of lead ion required to fully react with the molybdenum present to form insoluble lead molybdate and continuing the reaction with agitation until the desired percentage of the molybdenum present has reacted with the lead ion

Molybdenum Cycling During Crust Formation and Destruction

Science.gov (United States)

Greaney, A. T.; Rudnick, R. L.

2016-12-01

Molybdenum geochemistry has become an important tool for tracking the redox state of the early atmosphere and oceans as well as the emergence and sustainability of Mo-cofactored enzymes. However, in order for Mo to be enriched in the oceans, it must first be weathered out of the crust. Sulfides that weather in the presence of atmospheric O2have historically been deemed the predominant crustal source of Mo. Here, we test this assumption by determining the mineralogical hosts of Mo in Archean, Proterozoic, and Phanerozoic upper crustal rocks, using LA-ICP-MS. We also investigate Mo behavior during igneous differentiation and continental crust formation. We find that molybdenite, MoS2, is a weatherable sulfide source of Mo, but common igneous sulfides are not because their Mo concentrations are too low. However, molybdenite is uncommon in the upper continental crust. By contrast, volcanic glass is much more abundant and is a significant weatherable source of Mo that readily breaks down to release oxidized, soluble Mo whether or not atmospheric O2is present. Other common crustal mineral hosts of Mo are Ti-bearing phases like titanite, ilmenite, magnetite, and rutile that are resistant to weathering. Significant Mo depletion (relative to Ce and Pr) is observed in nearly every granitic rock analyzed in our study, but is not observed in OIB or MORB (Jenner and O'Neill, 2012). There are two possible reasons for this: 1) Mo is removed from cooling plutons during fluid expulsion, or 2) Mo is fractionated during igneous differentiation. The first scenario is a likely explanation given the solubility of oxidized Mo. However, correlations between Mo/Ce and Nb/La in several plutonic suites suggest a fractionating phase like rutile may sequester Mo in the lower crust. Additionally, a correlation between Mo/Ce and inferred tectonic setting (enrichments observed in rift-related plutons) suggest an overall tectonic influence on the availability of Mo in the upper crust.

Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

Directory of Open Access Journals (Sweden)

Jakkrit Suriboot

2016-04-01

Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

Bibliographic study on molybdenum biokinetics

International Nuclear Information System (INIS)

Erzberger, A.

1988-05-01

This bibliographical study compiles and analyzes findings about the metabolism and resorption of molybdenum. Besides including studies on the physiology of molybdenum 99, a general survey is given on molybdenum in the environment and on its physiological behaviour. In particular, information on the dependence of molybdenum resorption on various factors, such as the chemical form, antagonisms etc., are gathered from literature. These factors have to be considered for sensibly carrying out necessary experiments. (orig./MG) [de

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.; Shinagawa, Tatsuya; Ould-Chikh, Samy; Qureshi, Muhammad; Peng, Xuyuan; Wei, Nini; Anjum, Dalaver H.; Clo, Alain M.; Weng, Tsu-Chien; Nordlund, Dennis; Sokaras, Dimosthenis; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

2017-01-01

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.

2017-04-13

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

Support effects on hydrotreating activity of NiMo catalysts

International Nuclear Information System (INIS)

Dominguez-Crespo, M.A.; Arce-Estrada, E.M.; Torres-Huerta, A.M.; Diaz-Garcia, L.; Cortez de la Paz, M.T.

2007-01-01

The effect of the gamma alumina particle size on the catalytic activity of NiMoS x catalysts prepared by precipitation method of aluminum acetate at pH = 10 was studied. The structural characterization of the supports was measured by using XRD, pyridine FTIR-TPD and nitrogen physisorption. NiMo catalysts were characterized during the preparation steps (annealing and sulfidation) using transmission electron microscopy (TEM). Hydrogen TPR studies of the NiMo catalysts were also carried out in order to correlate their hydrogenating properties and their catalytic functionality. Catalytic tests were carried out in a pilot plant at 613, 633 and 653 K temperatures. The results showed that the rate constants of hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatizing (HDA) at 613-653 K decreased in the following order: A > B > C corresponding to the increase of NiMoS particle size associated to these catalysts

Geochemistry, Mineralogy and Microbiology of Molybdenum in Mining-Affected Environments

Directory of Open Access Journals (Sweden)

Francesca Frascoli

2018-01-01

Full Text Available Molybdenum is an essential element for life, with growing production due to a constantly expanding variety of industrial applications. The potentially harmful effects of Mo on the environment, and on human and ecosystem health, require knowledge of Mo behavior in mining-affected environments. Mo is usually present in trace amounts in ore deposits, but mining exploitation can lead to wastes with very high Mo concentrations (up to 4000 mg/kg Mo for tailings, as well as soil, sediments and water contamination in surrounding areas. In mine wastes, molybdenum is liberated from sulfide mineral oxidation and can be sorbed onto secondary Fe(III-minerals surfaces (jarosite, schwertmannite, ferrihydrite at moderately acidic waters, or taken up in secondary minerals such as powellite and wulfenite at neutral to alkaline pH. To date, no Mo-metabolising bacteria have been isolated from mine wastes. However, laboratory and in-situ experiments in other types of contaminated land have suggested that several Mo-reducing and -oxidising bacteria may be involved in the cycling of Mo in and from mine wastes, with good potential for bioremediation. Overall, a general lack of data is highlighted, emphasizing the need for further research on the contamination, geochemistry, bio-availability and microbial cycling of Mo in mining-affected environments to improve environmental management and remediation actions.

Catalytic effects of various catalysts in hydroprocessing of Cold Lake vacuum bottom. Cold Lake zansayu no hydroprocessing ni okeru kakushu shokubai no koka

Energy Technology Data Exchange (ETDEWEB)

Yokoyama, S.; Yamamoto, M.; Maekawa, Y.; Kotanigawa, T. (Government Industrial Development Laboratory, Hokkaido, Sapporo (Japan))

1991-11-07

The effects of various types of catalysts were studied on hydroprocessing of Cold Lake vacuum bottom (CLVB). FeS2 [Py] of an analytical reagent grade was used as sulfide catalyst, Fe2O3(SO4)[sup 2[minus

Molybdenum dioxide-molybdenite roasting

International Nuclear Information System (INIS)

Sabacky, B.J.; Hepworth, M.T.

1984-01-01

A process is disclosed for roasting molybdenite concentrates directly to molybdenum dioxide. The process comprises establishing a roasting zone having a temperature of about 700 0 C. to about 800 0 C., introducing into the roasting zone particulate molybdenum dioxide and molybdenite in a weight ratio of at least about 2:1 along with an oxygen-containing gas in amount sufficient to oxidize the sulfur content of the molybdenite to molybdenum dioxide

Polymer nanocomposite membranes with hierarchically structured catalysts for high throughput dehalogenation

Science.gov (United States)

Crock, Christopher A.

Halogenated organics are categorized as primary pollutants by the Environmental Protection Agency. Trichloroethylene (TCE), which had broad industrial use in the past, shows persistence in the environment because of its chemical stability. The large scale use and poor control of TCE resulted in its prolonged release into the environment before the carcinogenic risk associated with TCE was fully understood. TCE pollution stemmed from industrial effluents and improper disposal of solvent waste. Membrane reactors are promising technology for treating TCE polluted groundwater because of the high throughput, relatively low cost of membrane fabrication and facile retrofitting of existing membrane based water treatment facilities with catalytic membrane reactors. Compared to catalytic fluidized or fixed bed reactors, catalytic membrane reactors feature minimal diffusional limitation. Additionally, embedding catalyst within the membrane avoids the need for catalyst recovery and can prevent aggregation of catalytic nanoparticles. In this work, Pd/xGnP, Pd-Au/xGnP, and commercial Pd/Al2O3 nanoparticles were employed in batch and flow-through membrane reactors to catalyze the dehalogenation of TCE in the presence of dissolved H2. Bimetallic Pd-Au/xGnP catalysts were shown to be more active than monometallic Pd/xGnP or commercial Pd/Al 2O3 catalysts. In addition to synthesizing nanocomposite membranes for high-throughput TCE dehalogenation, the membrane based dehalogenation process was designed to minimize the detrimental impact of common catalyst poisons (S2-, HS-, and H2S -) by concurrent oxidation of sulfide species to gypsum in the presence of Ca2+ and removal of gypsum through membrane filtration. The engineered membrane dehalogenation process demonstrated that bimetallic Pd-Au/xGnP catalysts resisted deactivation by residual sulfide species after oxidation, and showed complete removal of gypsum during membrane filtration.

Process for hydroprocessing heavy oils utilizing sepiolite-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Auden, C.A.; Yan, T.-Y.

1986-04-15

A process is described for demetallizing and desulfurizing a hydrocarbon oil comprising contacting the hydrocarbon oil in the presence of hydrogen and a sepiolite-based catalyst composition under conditions of pressure and temperature sufficient to effect demetallization and desulfurization. The sepiolite-based catalyst composition has been prepared by first contacting the sepiolite with an aqueous solution of a first metal salt, then contacting the resultant metal ion-exchanged sepiolite with an aqueous solution of a compound of a second metal selected from the group consisting of molybdenum, tungsten and vanadium, and finally contacting the resultant metal-exchanged sepiolite product with an aqueous solution of a magnesium compound, thereby effecting a magnesium ion-exchange with the metal-exchanged sepiolite product and neutralizing acid sites on the sepiolite product.

Evaluation of molybdenum and its alloys

International Nuclear Information System (INIS)

Lundberg, L.B.

1981-01-01

The choice of pure molybdenum as the prime candidate material for space reactor core heat pipes is critically examined. Pure molybdenum's high ductile-brittle transition temperature appears to be its major disadvantage. The candidate materials examined in detail for this application include low carbon arc-cast molybdenum, TZM-molybdenum alloy, and molybdenum-rhenium alloys. Published engineering properties are collected and compared, and it appears that Mo-Re alloys with 10 to 15% rhenium offer the best combination. Hardware is presently being made from electron beam melted Mo-13Re to test this conclusion

Recovery of uranium and molybdenum from a carbonate type uranium-molybdenum ore

International Nuclear Information System (INIS)

Zhou Genmao; Zeng Yijun; Tang Baobin; Meng Shu; Xu Guolong

2014-01-01

Based on the results of process mineralogical research of a carbonate type uranium-molybdenum ore, leaching behaviors of the uranium-molybdenum ore were studied by alkali agitation leaching, conventional alkali column leaching and alkali curing column leaching processes. The results showed that using the alkali curing column leaching process, the leaching rate of molybdenum increased to more than 90%, and the leaching rate of uranium was about 85%, Compared with the conventional alkali column leaching process, the leaching time of the alkali curing column leaching process decreased by 60 days. (authors)

Rapid analysis of molybdenum contents in molybdenum master alloys by X-ray fluorescence technique

International Nuclear Information System (INIS)

Tongkong, P.

1985-01-01

Determination of molybdenum contents in molybdenum master alloy had been performed using energy dispersive x-ray fluorescence (EDX) technique where analysis were made via standard additions and calibration curves. Comparison of EDX technique with other analyzing techniques, i.e., wavelength dispersive x-ray fluorescence, neutron activation analysis and inductive coupled plasma spectrometry, showed consistency in the results. This technique was found to yield reliable results when molybdenum contents in master alloys were in the range of 13 to 50 percent using HPGe detector or proportional counter. When the required error was set at 1%, the minimum analyzing time was found to be 30 and 60 seconds for Fe-Mo master alloys with molybdenum content of 13.54 and 49.09 percent respectively. For Al-Mo master alloys, the minimum times required were 120 and 300 seconds with molybdenum content of 15.22 and 47.26 percent respectively

Method of producing oxidation resistant coatings for molybdenum

International Nuclear Information System (INIS)

Timmons, G.A.

1989-01-01

A method is described for producing a molybdenum element having adherently bonded thereto a thermally self-healing plasma-sprayed coating consisting essentially of a composite of molybdenum and a refactory oxide material capable of reacting with molybdenum oxide under oxidizing conditions to form a substantially thermally stable refractory compound of molybdenum, the method comprising plasma-spraying a coating formed by the step-wise application of a plurality of interbonded plasma-sprayed layers of a composite of molybdenum/refractory oxide material produced from a particulate mixture thereof. The coating comprises a first layer of molybdenum plasma-sprayed bonded to the substrate of the molybdenum element, a second layer of plasma-sprayed mixture of particulate molybdenum/refactory oxide consisting essentially of predominantly molybdenum bonded to the first layer, and succeeding layers of this mixture. The next step is heating the coated molybdenum element under oxidizing conditions to an elevated temperature sufficient to cause oxygen to diffuse into the surface of the multi-layered coating to react with dispersed molybdenum therein to form molybdenum oxide and effect healing of the coating by reaction of the molybdenum oxide with the contained refractory oxide and thereby protect the substrate of the molybdenum element against oxidation

Molybdenum reduction to molybdenum blue in Serratia sp. Strain DRY5 is catalyzed by a novel molybdenum-reducing enzyme.

Science.gov (United States)

Shukor, M Y; Halmi, M I E; Rahman, M F A; Shamaan, N A; Syed, M A

2014-01-01

The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a V max for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent K m for NADH was 0.79 mM. At 5 mM NADH, the apparent V max and apparent K m values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (k cat/K m ) of the Mo-reducing enzyme was 5.47 M(-1) s(-1). The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction.

Molybdenum Reduction to Molybdenum Blue in Serratia sp. Strain DRY5 Is Catalyzed by a Novel Molybdenum-Reducing Enzyme

Directory of Open Access Journals (Sweden)

M. Y. Shukor

2014-01-01

Full Text Available The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C. A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a Vmax for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent Km for NADH was 0.79 mM. At 5 mM NADH, the apparent Vmax and apparent Km values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (kcat/Km of the Mo-reducing enzyme was 5.47 M-1 s-1. The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction.

Glucose aided synthesis of molybdenum sulfide/carbon nanotubes composites as counter electrode for high performance dye-sensitized solar cells

International Nuclear Information System (INIS)

Yue, Gentian; Zhang, Weifeng; Wu, Jihuai; Jiang, Qiwei

2013-01-01

Graphical abstract: - Highlights: • The glucose aided (G-A) preparation of MoS 2 /CNTs composites were employed as CE in Pt-free DSSC. • The (G-A) MoS 2 /CNTs* CE showed the low R ct of 1.77 Ω cm 2 . • The efficiency of the DSSC reached 7.92% based on the (G-A) MoS 2 /CNTs* CE. - Abstract: In our present study, the composites of molybdenum disulfide/carbon nanotubes (MoS 2 /CNTs) were synthesized with glucose aided (G-A) by using an in situ hydrothermal route, and proposed as counter electrode (CE) catalyst in the dye-sensitized solar cells (DSSCs) for enhancing electrocatalytic activity toward the reduction of triiodide. The MoS 2 /CNTs composites with tentacle-like structure were confirmed by using the scanning and transmission electron microscopy. The superior structural characteristics including large active surface area and particularly the unique tentacle-like nanostructure along with 3D large interconnected interstitial volume guaranteed fast mass transport for the electrolyte, and enabled the (G-A) MoS 2 /CNTs CE to speed up the reduction of triiodide to iodide. The extensive electrochemical studies by the cyclic voltammetry, electrochemical impedence spectroscopy and Tafel measurements indicated that the (G-A) MoS 2 /CNTs CE possessed superior electrocatalytic activity, great electrochemical stability and impressive low charge transfer resistance on the electrolyte|electrode interface (1.77 Ω cm 2 ) in the triiodide/iodide system compared to the pristine MoS 2 , MoS 2 /C and sputtered Pt CEs. The DSSC assembled with the novel (G-A) MoS 2 /CNTs CE exhibited high power conversion efficiency of 7.92% under the illumination of 100 mW cm −2 , comparable to that of the DSSC with the Pt electrode (7.11%)

Study of the effect of ionizing radiation for utilization of spent cracking catalysts

International Nuclear Information System (INIS)

Kondo, Fernando Mantovani

2014-01-01

Catalyst is a substance that changes the rate of a reaction. In the petroleum industry the commonly catalysts are used for Fluid Catalytic Cracking (FCC) and Hydrocatalytic Cracking (HCC), which one applied in a specific stage. These catalysts are used to facilitate the molecular chains cracking which will generate a mixture of hydrocarbons. However, the catalyst gradually loses its activity, either by changing its original molecular structure or by its contamination from other petroleum molecules. The application of ionizing radiation (electron beam and gamma rays) over these spent catalysts was studied to contribute with the extraction of metals or rare-earths of high added-value. Tests carried out with FCC catalysts were used the techniques of 60 Co irradiation and electron beam (EB) and had as a subject the extraction of lanthanum (La 2 O 3 ), regeneration and utilization of these catalysts. However, the use of ionizing radiation has not contributed in these processes. Meanwhile with HCC catalysts the irradiation used was electron beam and had as a subject the extraction of molybdenum (MoO 3 ). In temperature around 750°C, these irradiated catalysts of the lower region have an extraction yield twice higher compared to non-irradiated ones, in other words 57.65% and 26.24% respectively. (author)

Raman study of supported molybdenum disulfide single layers

Science.gov (United States)

Durrer, William; Manciu, Felicia; Afanasiev, Pavel; Berhault, Gilles; Chianelli, Russell

2008-10-01

Owing to the increasing demand for clean transportation fuels, highly dispersed single layer transition metal sulfides such as MoS2-based catalysts play an important role in catalytic processes for upgrading and removing sulfur from heavy petroleum feed. In its crystalline bulk form, MoS2 is chemically rather inactive due to a strong tendency to form highly stacked layers, but, when dispersed as single-layer nanoclusters on a support, the MoS2 becomes catalytically active in the hydrogenolysis of sulphur and nitrogen from organic compounds (hydrotreating catalysis). In the present studies alumina-supported MoS2 samples were analyzed by confocal Raman spectroscopy. Evidence of peaks at 152 cm-1, 234 cm-1, and 336 cm-1, normally not seen in the Raman spectrum of the standard bulk crystal, confirms the formation of single layers of MoS2. Furthermore, the presence of the 383 cm-1 Raman line suggests the trigonal prismatic coordination of the formed MoS2 single layers. Depending on the sample preparation method, a restacking of MoS2 layers is also observed, mainly for ex-thiomolybdate samples sulfided at 550 C.

The use of mixed pyrrhotite/pyrite catalysts for co-liquefaction of coal and waste rubber tires

Energy Technology Data Exchange (ETDEWEB)

Dadyburjor, D.B.; Zondlo, J.W.; Sharma, R.K. [West Virginia Univ., Morgantown, WV (United States)] [and others

1995-12-31

The overall objective of this research program is to determine the optimum processing conditions for tire/coal co-liquefaction. The catalysts used will be a ferric-sulfide-based materials, as well as promising catalysts from other consortium laboratories. The intent here is to achieve the maximum coal+tire conversion at the mildest conditions of temperature and pressure. Specific objectives include an investigation of the effects of time, temperature, pressure, catalyst and co-solvent on the conversion and product slate of the co-liquefaction. Accomplishments and conclusions are discussed.

Method of producing molybdenum-99

Science.gov (United States)

Pitcher, Eric John

2013-05-28

Method of producing molybdenum-99, comprising accelerating ions by means of an accelerator; directing the ions onto a metal target so as to generate neutrons having an energy of greater than 10 MeV; directing the neutrons through a converter material comprising techentium-99 to produce a mixture comprising molybdenum-99; and, chemically extracting the molybdenum-99 from the mixture.

Intense molybdenum accumulation in sediments underneath a nitrogenous water column and implications for the reconstruction of paleo-redox conditions based on molybdenum isotopes

Science.gov (United States)

Scholz, Florian; Siebert, Christopher; Dale, Andrew W.; Frank, Martin

2017-09-01

The concentration and isotope composition of molybdenum (Mo) in sediments and sedimentary rocks are widely used proxies for anoxic conditions in the water column of paleo-marine systems. While the mechanisms leading to Mo fixation in modern restricted basins with anoxic and sulfidic (euxinic) conditions are reasonably well constrained, few studies have focused on Mo cycling in the context of open-marine anoxia. Here we present Mo data for water column particulate matter, modern surface sediments and a paleo-record covering the last 140,000 years from the Peruvian continental margin. Mo concentrations in late Holocene and Eemian (penultimate interglacial) shelf sediments off Peru range from ∼70 to 100 μg g-1, an extent of Mo enrichment that is thought to be indicative of (and limited to) euxinic systems. To investigate if this putative anomaly could be related to the occasional occurrence of sulfidic conditions in the water column overlying the Peruvian shelf, we compared trace metal (Mo, vanadium, uranium) enrichments in particulate matter from oxic, nitrate-reducing (nitrogenous) and sulfidic water masses. Coincident enrichments of iron (Fe) (oxyhydr)oxides and Mo in the nitrogenous water column as well as co-variation of dissolved Fe and Mo in the sediment pore water suggest that Mo is delivered to the sediment surface by Fe (oxyhydr)oxides. Most of these precipitate in the anoxic-nitrogenous water column due to oxidation of sediment-derived dissolved Fe with nitrate as a terminal electron acceptor. Upon reductive dissolution in the surface sediment, a fraction of the Fe and Mo is re-precipitated through interaction with pore water sulfide. The Fe- and nitrate-dependent mechanism of Mo accumulation proposed here is supported by the sedimentary Mo isotope composition, which is consistent with Mo adsorption onto Fe (oxyhydr)oxides. Trace metal co-variation patterns as well as Mo and nitrogen isotope systematics suggest that the same mechanism of Mo delivery

Preparation and Characterization of MoO3/Al2O3 Catalyst for Oxidative Desulfurization of Diesel using H2O2: Effect of Drying Method and Mo Loading

OpenAIRE

Azam Akbari; Mohammadreza Omidkhah; Jafar Toufighi Darian

2012-01-01

The mesoporous MoO3/γ-Al2O3 catalyst was prepared by incipient wetness impregnation method aiming to investigate the effect of drying method and molybdenum content on the catalyst property and performance towards the oxidation of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyle dibenzothiophene (4,6-DMDBT) with H2O2 for deep oxidative desulfurization of diesel fuel. The catalyst was characterized by XRD, BET, BJH and SEM method. The catalyst with 10wt.% and 1...

An oxygen-insensitive hydrogen evolution catalyst coated by a molybdenum-based layer for overall water splitting

Energy Technology Data Exchange (ETDEWEB)

Garcia-Esparza, Angel T.; Shinagawa, Tatsuya; Ould-Chikh, Samy; Qureshi, Muhammad; Peng, Xuyuan; Takanabe, Kazuhiro [KAUST Catalysis Center (KCC) and Physical Science and Engineering Division - PSE, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Wei, Nini; Anjum, Dalaver H. [Advanced Nanofabrication, Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Clo, Alain [Research Computing, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Weng, Tsu-Chien [Center for High Pressure Science and Technology Advanced Research, Shanghai (China); Nordlund, Dennis; Sokaras, Dimosthenis [Stanford Synchrotron Radiation Lightsource, Menlo Park, CA (United States); Kubota, Jun [Department of Chemical Engineering, Fukuoka University (Japan); Domen, Kazunari [Department of Chemical System Engineering, School of Engineering, The University of Tokyo (Japan)

2017-05-15

For overall water-splitting systems, it is essential to establish O{sub 2}-insensitive cathodes that allow cogeneration of H{sub 2} and O{sub 2}. An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H{sub 2} evolution in the presence of O{sub 2}. In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O{sub 2} gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoO{sub x}/Pt/SrTiO{sub 3} with inhibited water formation from H{sub 2} and O{sub 2}, which is the prevailing back reaction on the bare Pt/SrTiO{sub 3} photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Electrochemical behavior of Ni-Mo electro catalyst for water electrolysis

Energy Technology Data Exchange (ETDEWEB)

Fernandez V, S. M.; Ordonez R, E. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Cabanas M, G. [IPN, Centro de Nanociencias y Micro y Nanotecnologias, A. P. 75-874, 07300 Mexico D. F. (Mexico); Solorza F, O., E-mail: suilma.fernandez@inin.gob.m [IPN, Centro de Investigacion y de Estudios Avanzados, Departamento de Quimica, A. P. 14-740, 07000 Mexico D. F. (Mexico)

2010-07-01

Nickel-molybdenum based electrocatalysts were synthesized in organic media for the hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The structure, morphology and chemical composition of the catalysts were evaluated by X-ray diffraction, scanning electron microscopy and Aas. Results revealed nanocrystalline powder materials with Ni{sub 0.006}Mo, Ni{sub 0.1}Mo and Ni Mo compositions. The best performance for hydrogen evolution reaction, was obtained on Ni{sub 0.1}Mo electrode, whereas Ni Mo was for the oxygen evolution reaction. Results suggest that the material with 1:1 stoichiometric ratio could be considered as a promising electro catalyst for oxygen evolution reaction. This nanocrystalline powder is formed by Ni{sub 2}Mo{sub 3}O{sub 8} and a crystalline structure attributed to the possible formation of a Ni Mo cluster, becomes NiMoO{sub 4} after thermal treatment at 1073 K in air. The Ni Mo 1:1 cluster catalyst presented electrochemical stability during the oxygen evolution reaction. (Author)

Electrochemical behavior of Ni-Mo electro catalyst for water electrolysis

International Nuclear Information System (INIS)

Fernandez V, S. M.; Ordonez R, E.; Cabanas M, G.; Solorza F, O.

2010-01-01

Nickel-molybdenum based electrocatalysts were synthesized in organic media for the hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The structure, morphology and chemical composition of the catalysts were evaluated by X-ray diffraction, scanning electron microscopy and Aas. Results revealed nanocrystalline powder materials with Ni 0.006 Mo, Ni 0.1 Mo and Ni Mo compositions. The best performance for hydrogen evolution reaction, was obtained on Ni 0.1 Mo electrode, whereas Ni Mo was for the oxygen evolution reaction. Results suggest that the material with 1:1 stoichiometric ratio could be considered as a promising electro catalyst for oxygen evolution reaction. This nanocrystalline powder is formed by Ni 2 Mo 3 O 8 and a crystalline structure attributed to the possible formation of a Ni Mo cluster, becomes NiMoO 4 after thermal treatment at 1073 K in air. The Ni Mo 1:1 cluster catalyst presented electrochemical stability during the oxygen evolution reaction. (Author)

Graphene-Molybdenum Disulfide-Graphene Tunneling Junctions with Large-Area Synthesized Materials.

Science.gov (United States)

Joiner, Corey A; Campbell, Philip M; Tarasov, Alexey A; Beatty, Brian R; Perini, Chris J; Tsai, Meng-Yen; Ready, William J; Vogel, Eric M

2016-04-06

Tunneling devices based on vertical heterostructures of graphene and other 2D materials can overcome the low on-off ratios typically observed in planar graphene field-effect transistors. This study addresses the impact of processing conditions on two-dimensional materials in a fully integrated heterostructure device fabrication process. In this paper, graphene-molybdenum disulfide-graphene tunneling heterostructures were fabricated using only large-area synthesized materials, unlike previous studies that used small exfoliated flakes. The MoS2 tunneling barrier is either synthesized on a sacrificial substrate and transferred to the bottom-layer graphene or synthesized directly on CVD graphene. The presence of graphene was shown to have no impact on the quality of the grown MoS2. The thickness uniformity of MoS2 grown on graphene and SiO2 was found to be 1.8 ± 0.22 nm. XPS and Raman spectroscopy are used to show how the MoS2 synthesis process introduces defects into the graphene structure by incorporating sulfur into the graphene. The incorporation of sulfur was shown to be greatly reduced in the absence of molybdenum suggesting molybdenum acts as a catalyst for sulfur incorporation. Tunneling simulations based on the Bardeen transfer Hamiltonian were performed and compared to the experimental tunneling results. The simulations show the use of MoS2 as a tunneling barrier suppresses contributions to the tunneling current from the conduction band. This is a result of the observed reduction of electron conduction within the graphene sheets.

Molybdenum market in transition

International Nuclear Information System (INIS)

Sutulov, A.

1980-01-01

Since the beginning of 1980 - after seven years of constant unbalance between supply and demand of molybdenum, characterized by a demand overhang and after two years of unprecedented spot market prices - clear signals for a consolidation of the molybdenum market can be recognized. (orig.) [de

Investigation and development of heavy oil upgrading catalysts. 3

Energy Technology Data Exchange (ETDEWEB)

Lee, D.K.; Lee, I.C.; Yoon, W.L.; Lee, H.T.; Chung, H.; Hwang, Y.J.; Park, S.H. [Korea Inst. of Energy Research, Taejon (Korea, Republic of)

1995-12-01

This study aimed at the domestic development of HDS catalysts which are most fundamental and wide-used in the petroleum refinery. In this year, some experimental works were conducted for developing the effective utilization technology of the novel dispersed-catalysts in the hydro-desulfurization of heavy oils, and improving the reaction performance of alumina-supported Mo-based hydro-treating catalysts conventionally used in most of refineries. First, it was experimentally proved that the dispersed catalysts of Co-Mo could be employed for the hydro-desulfurization of a heavy atmospheric residual oil excluding the catalyst deactivation. The utilization of a carbon-expanded reactor in combination with this dispersed catalyst system exhibited an enhanced reaction performance and provided an efficient way for the separation and recovery of the dispersed catalytic component from oils. Second, the tungsten-incorporated WCoMo/{gamma}-Al{sub 2}O{sub 3} catalyst revealed the improved catalytic performance in the various hydro-treating reactions and in the initial deactivation rates for the high pressure hydro-treatment of a heavy oil as compared with the commercial CoMo/{gamma}-Al{sub 2}O{sub 3} catalyst. This new experimental finding for the promoting role of the monomeric WO{sub 3} species in CoMo/{gamma}-Al{sub 2}O{sub 3} catalyst may be generally applicable to the Mo-based alumina-sulfide phase, higher catalytic activity, and more extended service life. (author). 101 refs., 33 figs., 18 tabs.

Formation of nitrogen compounds from nitrogen-containing rings during oxidative regeneration of spent hydroprocessing catalysts

Energy Technology Data Exchange (ETDEWEB)

Furimsky, E.; Nielsen, M.; Jurasek, P. [CANMET, Ottawa, ON (Canada). Energy Research Laboratories

1995-05-01

Commercial CoMo and NiMo catalysts in an oxidic and sulfided form and a {gamma}-alumina were deposited with pyrrole, pyridine, and quinoline. The deposited catalysts and two spent hydroprocessing catalysts were pyrolyzed and oxidized under conditions typical of regeneration of hydroprocessing catalysts. The formation of NH{sub 3} and HCN, as well as selected cases of N{sub 2}O and NO, was monitored during the experiments. NH{sub 3} and HCN were formed during pyrolysis of pyrrole-deposited catalysts whereas only NH{sub 3} was formed during that of pyridine-and quinoline-deposited catalysts. For all deposited catalysts, both NH{sub 3} and HCN were formed during temperature programmed oxidation in 2% O{sub 2}. For spent catalysts, a small amount of N{sub 2}O was formed in 2 and 4% O{sub 2}. For pyrrole-deposited catalysts, large yields of N{sub 2}O were formed in 4% O{sub 2}. Under the same conditions, N{sub 2}O yields for pyridine- and quinoline-deposited catalysts were very small. 13 refs., 12 figs., 6 tabs.

Molybdenum Oxides - From Fundamentals to Functionality.

Science.gov (United States)

de Castro, Isabela Alves; Datta, Robi Shankar; Ou, Jian Zhen; Castellanos-Gomez, Andres; Sriram, Sharath; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-10-01

The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for purifying molybdenum

International Nuclear Information System (INIS)

Cheresnowsky, J.

1989-01-01

This patent describes a process for purifying molybdenum containing arsenic and phosphorus. The process comprising: adding to an acidic slurry of molybdenum trioxide, a source of magnesium ions in a solid form, with the amount of magnesium and the magnesium ion concentration in the subsequently formed ammonium molybdate solution being sufficient to subsequently form insoluble compounds containing greater than about 80% by weight of the arsenic and greater than about 80% by weight of the phosphorus, and ammonia in an amount sufficient to subsequently dissolve the molybdenum and subsequently form the insoluble compounds, with the source of magnesium ions being added prior to the addition of the ammonia; digesting the resulting ammoniated slurry at a temperature sufficient to dissolve the molybdenum and form an ammonium molybdate solution while the pH is maintained at from bout 9 to about 10 to form a solid containing the insoluble compounds; and separating the solid from the ammonium molybdate solution

Cooperative research in coal liquefaction. Final report, May 1, 1992--April 30, 1993

Energy Technology Data Exchange (ETDEWEB)

Huffman, G.P. [ed.

1996-03-01

Research on sulfate and metal (Mo, Sn) promoted Fe{sub 2}O{sub 3} catalysts in the current year focused on optimization of conditions. Parameters varied included temperature, solvent, solvent-to-coal ratio, and the effect of presulfiding versus in situ sulfiding. Oil yields were found to increase approximately proportionately with both temperature and solvent-to-coal ratio. The donor solvent, tetralin, proved to give better total conversion and oil yields than either 1-methylnaphthalene or Wilsonville recycle oil. A significant enhancement of both total liquefaction yields and oil yields from lignites and subbituminous coals has been achieved by incorporating iron into the coal matrix by cation exchange. A study has been conducted on the synthesis of iron, molybdenum, and tungsten catalysts using a laser pyrolysis technique.

Elimination of excess molybdenum by cattle

Energy Technology Data Exchange (ETDEWEB)

Toelgyesi, G.; Elmoty, I.A.

1967-01-01

It was found that cattle would ingest spontaneously 5-15 g of molybdenum on one occasion. The uptake of this quantity caused but moderate loss of appetite and mild enteritis, both normalizing in one week. The occurrence of a severe acute molybdenum poisoning can be practically excluded, owing to refusal of the poisoned feed. Spontaneously ingested molybdenum caused on the first day a 30-100 fold rise of ruminal Mo-level, decreasing to the order of the normal value in about one week. But in the urine and faeces, Mo-level was at least 10 fold, in the blood and milk about 4 fold of the normal one, even one or two weeks after ingestion. During this period at least 90% of ingested Mo was eliminated with the faeces, urine and milk. One week after the ingestion of molybdenum, the rumen content showed no evidence on poisoning and no trace of molybdenum. Oral administration of ammonium molybdenate in an amount equivalent to 40 g molybdenum caused no fatality. In fact, cattle would never ingest spontaneously such a large dose.

Hydrogen production through microheterogeneous photocatalysis of hydrogen sulfide cleavage. The thiosulfate cycle

Energy Technology Data Exchange (ETDEWEB)

Borgarello, E; Serpone, N; Graetzel, M; Pelizzetti, E

1985-01-01

Cleavage of hydrogen sulfide into hydrogen and sulfur occurs in alkaline aqueous CdS dispersions under visible light illumination. Small quantities of a noble metal catalyst (RuO/sub 2/) loaded onto 'naked' CdS particles markedly improve the yield of hydrogen formation. The effect of RuO/sub 2/ is ascribed to catalysis of electron transfer to proton. Simultaneous and efficient photogeneration of hydrogen and thiosulfate occurs in CdS dispersions containing both sulfite and bisulfide (or sulfide) ions. Electron transfer from the conduction band of CdS to that of TiO/sub 2/ particles occurs in alkaline suspensions containing these HS/sup -/ ions and has been exploited to improve the performance of a system achieving decomposition of H/sub 2/S by visible light. Equally important is a recent finding that the performance of a system containing 'naked' CdS in combination with RuO/sub 2/-loaded TiO/sub 2/ particles is far better than that of CdS/RuO/sub 2/ alone. Additionally, conduction band electrons produced by bandgap excitation of TiO/sub 2/ particles efficiently reduce thiosulfate to sulfide and sulfite. The valence band process in alklaine TiO/sub 2/ dispersions is thought to involve oxidation of S/sub 2/O/sub 3//sup 2 -/ to tetrathionate, S/sub 4/O/sub 6//sup 2 -/, which quantitatively dismutates into sulfite and thiosulfate. The photodriven disproportionation of thiosulfate into sulfide and sulfate is of great interest in systems that photochemically cleave hydrogen sulfide into hydrogen and sulfur. (author).

Light-Induced Activation of a Molybdenum Oxotransferase Model within a Ru(II)-Mo(VI) Dyad.

Science.gov (United States)

Ducrot, Aurélien B; Coulson, Ben A; Perutz, Robin N; Duhme-Klair, Anne-Kathrin

2016-12-19

Nature uses molybdenum-containing enzymes to catalyze oxygen atom transfer (OAT) from water to organic substrates. In these enzymes, the two electrons that are released during the reaction are rapidly removed, one at a time, by spatially separated electron transfer units. Inspired by this design, a Ru(II)-Mo(VI) dyad was synthesized and characterized, with the aim of accelerating the rate-determining step in the cis-dioxo molybdenum-catalyzed OAT cycle, the transfer of an oxo ligand to triphenyl phosphine, via a photo-oxidation process. The dyad consists of a photoactive bis(bipyridyl)-phenanthroline ruthenium moiety that is covalently linked to a bioinspired cis-dioxo molybdenum thiosemicarbazone complex. The quantum yield and luminescence lifetimes of the dyad [Ru(bpy) 2 (L 2 )MoO 2 (solv)] 2+ were determined. The major component of the luminescence decay in MeCN solution (τ = 1149 ± 2 ns, 67%) corresponds closely to the lifetime of excited [Ru(bpy) 2 (phen-NH 2 )] 2+ , while the minor component (τ = 320 ± 1 ns, 31%) matches that of [Ru(bpy) 2 (H 2 -L 2 )] 2+ . In addition, the (spectro)electrochemical properties of the system were investigated. Catalytic tests showed that the dyad-catalyzed OAT from dimethyl sulfoxide to triphenyl phosphine proceeds significantly faster upon irradiation with visible light than in the dark. Methylviologen acts as a mediator in the photoredox cycle, but it is regenerated and hence only required in stoichiometric amounts with respect to the catalyst rather than sacrificial amounts. It is proposed that oxidative quenching of the photoexcited Ru unit, followed by intramolecular electron transfer, leads to the production of a reactive one-electron oxidized catalyst, which is not accessible by electrochemical methods. A significant, but less pronounced, rate enhancement was observed when an analogous bimolecular system was tested, indicating that intramolecular electron transfer between the photosensitizer and the catalytic center

Molybdenum solubility in aluminium nitrate solutions

Energy Technology Data Exchange (ETDEWEB)

Heres, X.; Sans, D.; Bertrand, M.; Eysseric, C. [CEA, Centre de Marcoule, Nuclear Energy Division, DRCP, BP 17171, 30207 Bagnols-sur-Ceze Cedex (France); Brackx, E.; Domenger, R.; Excoffier, E. [CEA, Centre de Marcoule, Nuclear Energy Division, DTEC, BP 17171, 30207 Bagnols-sur-Ceze Cedex (France); Valery, J.F. [AREVA-NC, DOR/RDP, Paris - La Defense (France)

2016-07-01

For over 60 years, research reactors (RR or RTR for research testing reactors) have been used as neutron sources for research, radioisotope production ({sup 99}Mo/{sup 99m}Tc), nuclear medicine, materials characterization, etc... Currently, over 240 of these reactors are in operation in 56 countries. They are simpler than power reactors and operate at lower temperature (cooled to below 100 C. degrees). The fuel assemblies are typically plates or cylinders of uranium alloy and aluminium (U-Al) coated with pure aluminium. These fuels can be processed in AREVA La Hague plant after batch dissolution in concentrated nitric acid and mixing with UOX fuel streams. The aim of this study is to accurately measure the solubility of molybdenum in nitric acid solution containing high concentrations of aluminium. The higher the molybdenum solubility is, the more flexible reprocessing operations are, especially when the spent fuels contain high amounts of molybdenum. To be most representative of the dissolution process, uranium-molybdenum alloy and molybdenum metal powder were dissolved in solutions of aluminium nitrate at the nominal dissolution temperature. The experiments showed complete dissolution of metallic elements after 30 minutes long stirring, even if molybdenum metal was added in excess. After an induction period, a slow precipitation of molybdic acid occurs for about 15 hours. The data obtained show the molybdenum solubility decreases with increasing aluminium concentration. The solubility law follows an exponential relation around 40 g/L of aluminium with a high determination coefficient. Molybdenum solubility is not impacted by the presence of gadolinium, or by an increasing concentration of uranium. (authors)

Mechanism of 1, 1-d2 propene oxidation over oxide catalysts

International Nuclear Information System (INIS)

Portefaix, J.L.; Figueras, F.; Forissier, M.

1980-01-01

CD 2 CHCH 3 was oxidized over bismuth molybdate, tin-antimony mixed oxides and supported molybdenum and vanadium oxide catalysts. The deuterium retention is high ( > 90%) in the recovered propene. Percentage retentions of deuterium in the acrolein agree with literature data when bismuth molybdate is used as catalyst. On Sb-Sn-O and supported Mo and V oxides, no isotope effect is noticed for the abstraction of the second hydrogen from the olefin. The slow step of the reaction may therefore be different for the oxidation of propene on Bi-Mo-O and Sb-Sn-O. The ethanal produced by oxidation of CD 2 CHCH 3 contains only minor amounts of deuterium, whatever the catalyst used. It is suggested that partial oxidation of propene to acrolein and C-C bond rupture are parallel reactions which involve different intermediates. Possible mechanisms adapted from organic chemistry are presented to explain these findings. 4 tables

Kinetics of molybdenum reduction to molybdenum blue by Bacillus sp. strain A.rzi.

Science.gov (United States)

Othman, A R; Bakar, N A; Halmi, M I E; Johari, W L W; Ahmad, S A; Jirangon, H; Syed, M A; Shukor, M Y

2013-01-01

Molybdenum is very toxic to agricultural animals. Mo-reducing bacterium can be used to immobilize soluble molybdenum to insoluble forms, reducing its toxicity in the process. In this work the isolation of a novel molybdate-reducing Gram positive bacterium tentatively identified as Bacillus sp. strain A.rzi from a metal-contaminated soil is reported. The cellular reduction of molybdate to molybdenum blue occurred optimally at 4 mM phosphate, using 1% (w/v) glucose, 50 mM molybdate, between 28 and 30 °C and at pH 7.3. The spectrum of the Mo-blue product showed a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of bacterial electron transport system (ETS) such as rotenone, sodium azide, antimycin A, and potassium cyanide could not inhibit the molybdenum-reducing activity. At 0.1 mM, mercury, copper, cadmium, arsenic, lead, chromium, cobalt, and zinc showed strong inhibition on molybdate reduction by crude enzyme. The best model that fitted the experimental data well was Luong followed by Haldane and Monod. The calculated value for Luong's constants p max, K(s), S(m), and n was 5.88 μmole Mo-blue hr(-1), 70.36 mM, 108.22 mM, and 0.74, respectively. The characteristics of this bacterium make it an ideal tool for bioremediation of molybdenum pollution.

Formation conditions for regenerated uranium blacks in uranium-molybdenum deposits

International Nuclear Information System (INIS)

Skvortsova, K.V.; Sychev, I.V.; Modnikov, I.S.; Zhil'tsova, I.G.

1980-01-01

Formation conditions of regenerated uranium blacks in the zone of incomplete oxidation and cementation of uranium-molybdenum deposit have been studied. Mixed and regenerated blacks were differed from residual ones by the method of determining excess quantity of lead isotope (Pb 206 ) in ores. Determined were the most favourable conditions for formation of regenerated uranium blacks: sheets of brittle and permeable volcanic rocks characterized by heterogeneous structure of a section, by considerable development of gentle interlayer strippings and zones of hydrothermal alteration; predominance of reduction conditions in a media over oxidation ones under limited oxygen access and other oxidating agents; the composition of hypogenic ores characterized by optimum correlations of uranium minerals, sulfides and carbonates affecting violations of pH in oxidating solutions in the range of 5-6; the initial composition of ground water resulting from climatic conditions of the region and the composition of ore-bearing strata and others. Conditions unfavourable for the formation of regenerated uranium blacks are shown

Core-shell rhodium sulfide catalyst for hydrogen evolution reaction / hydrogen oxidation reaction in hydrogen-bromine reversible fuel cell

Science.gov (United States)

Li, Yuanchao; Nguyen, Trung Van

2018-04-01

Synthesis and characterization of high electrochemical active surface area (ECSA) core-shell RhxSy catalysts for hydrogen evolution oxidation (HER)/hydrogen oxidation reaction (HOR) in H2-Br2 fuel cell are discussed. Catalysts with RhxSy as shell and different percentages (5%, 10%, and 20%) of platinum on carbon as core materials are synthesized. Cyclic voltammetry is used to evaluate the Pt-equivalent mass specific ECSA and durability of these catalysts. Transmission electron microscopy (TEM), X-ray Photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX) techniques are utilized to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively. Cycling test and polarization curve measurements in the H2-Br2 fuel cell are used to assess the catalyst stability and performance in a fuel cell. The results show that the catalysts with core-shell structure have higher mass specific ECSA (50 m2 gm-Rh-1) compared to a commercial catalyst (RhxSy/C catalyst from BASF, 6.9 m2 gm-Rh-1). It also shows better HOR/HER performance in the fuel cell. Compared to the platinum catalyst, the core-shell catalysts show more stable performance in the fuel cell cycling test.

A model compound (methyl oleate, oleic acid, triolein) study of triglycerides hydrodeoxygenation over alumina-supported NiMo sulfide

NARCIS (Netherlands)

Coumans, A.E.; Hensen, E.J.M.

We studied hydrodeoxygenation of model compounds for vegetable oil into diesel-range hydrocarbons on a sulfided NiMo/γ-Al2O3 catalyst under trickle-flow conditions. Methyl oleate (methyl ester of oleic acid, a C18 fatty acid with one unsaturated bond in the chain) represented the C18 alkyl esters in

CVD molybdenum films of high infrared reflectance

Energy Technology Data Exchange (ETDEWEB)

Carver, G. E.

1979-01-01

Molybdenum thin films of high infrared reflectance have been deposited by pyrolytic decomposition of molybdenum carbonyl (Mo(CO)/sub 6/), and by hydrogen reduction of molybdenum pentachloride (MoCl/sub 5/). Reflectance values within 0.7% of the reflectance of supersmooth bulk molybdenum have been attained by annealing films of lower reflectance in both reducing and non-reducing atmospheres. All depositions and anneals proceed at atmospheric pressure, facilitating a continuous, flow-through fabrication. These reflectors combine the high temperature stability of molybdenum thin films with the infrared reflectance of a material such as aluminum. Deposition from Mo(CO)/sub 6/ under oxidizing conditions, and subsequent anneal in a reducing atmosphere, results in films that combine high solar absorptance with low thermal emittance. If anti-reflected, black molybdenum films can serve as highly selective single layer photothermal converters. Structural, compositional, and crystallographic properties have been measured after both deposition and anneal.

MORE ACTIVE AND SULFUR RESISTANT BIMETALLIC Pd-Ni CATALYSTS

OpenAIRE

Betti, Carolina; Carrara, Nicolás; Badano, Juan; Lederhos, Cecilia; Vera, Carlos; Quiroga, Mónica

2018-01-01

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfided compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the pr...

Kinetics of Molybdenum Reduction to Molybdenum Blue by Bacillus sp. Strain A.rzi

Directory of Open Access Journals (Sweden)

A. R. Othman

2013-01-01

Full Text Available Molybdenum is very toxic to agricultural animals. Mo-reducing bacterium can be used to immobilize soluble molybdenum to insoluble forms, reducing its toxicity in the process. In this work the isolation of a novel molybdate-reducing Gram positive bacterium tentatively identified as Bacillus sp. strain A.rzi from a metal-contaminated soil is reported. The cellular reduction of molybdate to molybdenum blue occurred optimally at 4 mM phosphate, using 1% (w/v glucose, 50 mM molybdate, between 28 and 30°C and at pH 7.3. The spectrum of the Mo-blue product showed a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of bacterial electron transport system (ETS such as rotenone, sodium azide, antimycin A, and potassium cyanide could not inhibit the molybdenum-reducing activity. At 0.1 mM, mercury, copper, cadmium, arsenic, lead, chromium, cobalt, and zinc showed strong inhibition on molybdate reduction by crude enzyme. The best model that fitted the experimental data well was Luong followed by Haldane and Monod. The calculated value for Luong’s constants pmax, Ks, Sm, and n was 5.88 μmole Mo-blue hr−1, 70.36 mM, 108.22 mM, and 0.74, respectively. The characteristics of this bacterium make it an ideal tool for bioremediation of molybdenum pollution.

Preparation of selective molybdenum concentrate from collective coppermolybdenum concentrate

Directory of Open Access Journals (Sweden)

N. Tusupbaev

2016-06-01

Full Text Available The paper considers possibilities of selective separation of the concentrate of copper and molybdenum from a collective copper-molybdenum concentrate of Aktogay deposit using regrinding and conventional flotation reagents. In the case of conventional flotoreagents, the content of molybdenum in a molybdenum concentrate was 8.0% at extraction effectiveness 83.12%. At 27.96% extraction degree of copper, it’s content in the concentrate equaled to 21.3%. After regrinding, molybdenum content in the concentrate was 24.0% at the extraction effectiveness 59.63%, and copper content in the concentrate was 21.9% at the recovery of 61.23%. Thus, the regrinding of a collective copper-molybdenum concentrate resulted in an increase in the content of molybdenum in molybdenum concentrate by 16%, and the copper concentration increased by 0.6%.

More active and sulfur resistant bimetallic Pd-Ni catalysts

Energy Technology Data Exchange (ETDEWEB)

Betti, Carolina; Carrara, Nicolás; Badano, Juan; Lederhos, Cecilia; Vera, Carlos; Quiroga, Mónica, E-mail: mquiroga@fiq.unl.edu.ar [Instituto de Investigaciones en Catálisis y Petroquímica, INCAPE (FIQ-UNL, CONICET), Santa Fe (Argentina)

2018-02-15

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfide compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the presence of different Pd species: Pd{sup δ-}, Pd{sup 0} and Pd{sup δ+}. In the case of the Ni containing catalysts, Ni{sup 0} and NiO species were also detected. These palladium and nickel species would be responsible of the variation of activity and sulfur resistance of the catalysts. NiClPd catalysts had a higher resistance to deactivation by sulfur poisoning. This was associated to a higher concentration of Pd{sup η+}Cl{sub x}O{sub y} species that would prevent the adsorption of thiophene by both steric and electronic effects. It could also be due to the lower concentration of Pd{sup 0} and Ni{sup 0} on these catalysts, as compared to those shown by the PdNiCl catalysts. Both the Pd{sup 0} and Ni{sup 0} species are more prone to poisoning because of their higher electronic availability. (author)

Modifiers in rhodium catalysts for carbon monoxide hydrogenation: Structure-activity relationships

Energy Technology Data Exchange (ETDEWEB)

Bhore, N. A.

1989-05-01

This report is aimed at identifying interesting modified rhodium systems and elucidating structure-activity relationships in these systems with the overall goal of understanding the scientific issues in the catalytic conversion of syngas to oxygenates. Specific additives (sodium and molybdenum) are selected based on the scoping experiments. The effect of the additives on supported rhodium catalysts is then investigated. Throughout the investigation, experiments and analysis were performed on real systems instead of ideal systems. 374 refs., 82 figs., 57 tabs.

Electroless Nickel-Based Catalyst for Diffusion Limited Hydrogen Generation through Hydrolysis of Borohydride

Directory of Open Access Journals (Sweden)

Shannon P. Anderson

2013-07-01

Full Text Available Catalysts based on electroless nickel and bi-metallic nickel-molybdenum nanoparticles were synthesized for the hydrolysis of sodium borohydride for hydrogen generation. The catalysts were synthesized by polymer-stabilized Pd nanoparticle-catalyzation and activation of Al2O3 substrate and electroless Ni or Ni-Mo plating of the substrate for selected time lengths. Catalytic activity of the synthesized catalysts was tested for the hydrolyzation of alkaline-stabilized NaBH4 solution for hydrogen generation. The effects of electroless plating time lengths, temperature and NaBH4 concentration on hydrogen generation rates were analyzed and discussed. Compositional analysis and surface morphology were carried out for nano-metallized Al2O3 using Scanning Electron Micrographs (SEM and Energy Dispersive X-Ray Microanalysis (EDAX. The as-plated polymer-stabilized electroless nickel catalyst plated for 10 min and unstirred in the hydrolysis reaction exhibited appreciable catalytic activity for hydrolysis of NaBH4. For a zero-order reaction assumption, activation energy of hydrogen generation using the catalyst was estimated at 104.6 kJ/mol. Suggestions are provided for further work needed prior to using the catalyst for portable hydrogen generation from aqueous alkaline-stabilized NaBH4 solution for fuel cells.

Spatially resolved spectroscopy on the preparation of CoMo/Al2O3 hydrodesulphurization catalysts

NARCIS (Netherlands)

Bergwerff, J.A.

2007-01-01

Supported catalysts form an important class of functional materials, since they are widely applied in oil refining and the manufacturing of both bulk and fine chemicals. In these systems, the active phase, consisting of a metal, metal-oxide or metal-sulfide is dispersed into the pore system of

Theoretical studies of homogeneous catalysts mimicking nitrogenase.

Science.gov (United States)

Sgrignani, Jacopo; Franco, Duvan; Magistrato, Alessandra

2011-01-10

The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen 'fixation' via an iron molybdenum cofactor (FeMo-co) under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N₂ to various degrees. However, to date Mo(N₂)(HIPTN)₃N with (HIPTN)₃N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N₂. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

Commercial application of titania-supported hydrodesulfurization catalysts in the production of hydrogen using full-range FCC off-gas

Energy Technology Data Exchange (ETDEWEB)

Wang, Shaohu [SINOPEC Wuhan Branch, Qingshan, Wuhan 430082 (China); Shen, Binglong; Qu, Lianglong [Beijing Haishunde Titanium Catalyst Co. Ltd., A-1 North East-Ring Road, Beijing Economic-Technological Development Area, Beijing 100176 (China)

2004-11-24

This paper provides an alternative for low-cost feed used for on-purpose hydrogen production. Full-range FCC off-gas was applied to steam-reforming process as feed after treating with hydrogenation and hydrodesulfurization catalysts. Commercial run results were reported with novel TiO{sub 2}-supported Mo-based catalysts, T205A-1 and T205. The processes of catalysts loading, sulfidation, start-up and long-term run were described in details. Long-term run showed that TiO{sub 2}-supported Mo catalysts have good low-temperature hydrogenation activity, excellent HDS activity, and outstanding stability. Use of FCC off-gas as feed for hydrogen production is quite promising and will increase margins for refiners today.

The Development of Molybdenum Speciation as a Paleoredox Tool

Science.gov (United States)

Rodley, J.; Peacock, C.; Mosselmans, J. F. W.; Poulton, S.

2017-12-01

The redox state of the oceans has changed throughout geological time and an understanding of these changes is essential to elucidate links between ocean chemistry, climate and life. Due to its abundance in seawater and redox-sensitive nature, molybdenum has enormous potential as a paleoredox proxy. Although a significant amount of research has been done on molybdenum in ancient and modern sediments in terms of its concentrations and isotopic ratios there remains a limited understanding of the drawdown mechanisms of molybdenum under different redox conditions restricting its use in identifying a range of redox states. In order to address these uncertainties, we have developed a novel sequential extraction technique to examine molybdenum concentrations in six sediment fractions from modern samples that represent oxic, nitrogenous, ferruginous and euxinic environments. In addition we use µ-XRF and µ-XANES synchrotron spectroscopy to examine the molybdenum speciation within these fractions and environments. To interpret our µ-XANES data we have developed an extensive library of molybdenum XANES standards that represent molybdenum sequestration by the sediment fractions identified from the sequential extraction. To further verify our synchrotron results we developed a series of µ-XANES micro-column experiments to examine preferential uptake pathways of molybdenum to different sediment phases under a euxinic water column. The initial data from both the sequential extraction and µ-XANES methods indicate that molybdenum is not limited to a single burial pathway in any of the redox environments. We find that each of the redox environments can be characterised by a limited set of molybdenum phase associations, with molybdenum adsorption to pyrite likely the dominant burial pathway. These findings agree with existing research for molybdenum speciation in euxinic environments suggesting that both pyrite and sulphidised organic matter act as important molybdenum sinks. Our

Molybdenum distribution and sensitivity in tomatoes, sunflowers and beans

Energy Technology Data Exchange (ETDEWEB)

Hecht-Buchholz, C

1973-01-01

The influence of increasing levels of molybdenum on the growth, molybdenum uptake and distribution in individual plant organs was investigated in tomatoes, beans and sunflowers in a 9 day trial. With tomatoes, which showed marked damage with high molybdenum levels, the molybdenum content of dry matter was highest in the leaf and lowest in the stem. On the other hand, beans, insensitive towards the high molybdenum level, dry matter molybdenum content was appreciably higher in the stem than in the leaf. It is supposed that in plant species, insensitive to high molybdenum levels, molybdenum is held less firmly in this tissue and can attain damaging levels in the cytoplasm of the youngest leaf tissue cells. It is supposed, on the basis of the reactions which were carried out with expressed root juice and on the basis of the yellow coloration attainable in vitro in the tissue caused by the addition of molybdate solution, that the yellow coloration appearing in the cells and plant organs of various plant species, here tomatoes and sunflowers, with high molybdenum levels is due to a reaction between molybdenum and polyvalent phenols in cellsap.

Amorphous nickel/cobalt tungsten sulfide electrocatalysts for high-efficiency hydrogen evolution reaction

Energy Technology Data Exchange (ETDEWEB)

Yang, Lun [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wu, Xinglong, E-mail: hkxlwu@nju.edu.cn [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Department of Physics, NingBo University, NingBo 315001 (China); Zhu, Xiaoshu [Center for Analysis and Testing, Nanjing Normal University, Nanjing 210093 (China); He, Chengyu; Meng, Ming; Gan, Zhixing [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2015-06-30

Graphical abstract: - Highlights: • Amorphous nickel/cobalt tungsten sulfides were synthesized by a thermolytic process. • Amorphous NiWS and CoWS could realize hydrogen evolution efficiently. • Ni/Co promotion and annealing alter the porous structure and chemical bonding states. • Active sites on the surface of amorphous WS{sub x} are increased with Ni or Co doping. • Amorphous NiWS and CoWS have immense potentials in water splitting devices. - Abstract: The hydrogen evolution reaction (HER), an appealing solution for future energy supply, requires efficient and inexpensive electrocatalysts with abundant active surface sites. Although crystalline MoS{sub 2} and WS{sub 2} are promising candidates, their activity is dominated by edge sites. Amorphous tungsten sulfide prepared so far lacks the required active sites and its application has thus been hampered. In this work, nickel and cobalt incorporated amorphous tungsten sulfide synthesized by a thermolytic process is demonstrated to enhance the HER efficiency dramatically. The amorphous nickel tungsten sulfide (amorphous NiWS) annealed at 210 °C delivers the best HER performance in this system boasting a Tafel slope of 55 mV per decade and current density of 8.6 mA cm{sup −2} at 250 mV overpotential in a sustained test for 24 h. The introduction of Ni or Co into the catalyst and subsequent thermal treatment alters the porous structure and chemical bonding states thereby increasing the density of active sites on the surface.

Novel Microbial Assemblages Dominate Weathered Sulfide-Bearing Rock from Copper-Nickel Deposits in the Duluth Complex, Minnesota, USA.

Science.gov (United States)

Jones, Daniel S; Lapakko, Kim A; Wenz, Zachary J; Olson, Michael C; Roepke, Elizabeth W; Sadowsky, Michael J; Novak, Paige J; Bailey, Jake V

2017-08-15

The Duluth Complex in northeastern Minnesota hosts economically significant deposits of copper, nickel, and platinum group elements (PGEs). The primary sulfide mineralogy of these deposits includes the minerals pyrrhotite, chalcopyrite, pentlandite, and cubanite, and weathering experiments show that most sulfide-bearing rock from the Duluth Complex generates moderately acidic leachate (pH 4 to 6). Microorganisms are important catalysts for metal sulfide oxidation and could influence the quality of water from mines in the Duluth Complex. Nevertheless, compared with that of extremely acidic environments, much less is known about the microbial ecology of moderately acidic sulfide-bearing mine waste, and so existing information may have little relevance to those microorganisms catalyzing oxidation reactions in the Duluth Complex. Here, we characterized the microbial communities in decade-long weathering experiments (kinetic tests) conducted on crushed rock and tailings from the Duluth Complex. Analyses of 16S rRNA genes and transcripts showed that differences among microbial communities correspond to pH, rock type, and experimental treatment. Moreover, microbial communities from the weathered Duluth Complex rock were dominated by taxa that are not typically associated with acidic mine waste. The most abundant operational taxonomic units (OTUs) were from the genera Meiothermus and Sulfuriferula , as well as from diverse clades of uncultivated Chloroflexi , Acidobacteria , and Betaproteobacteria Specific taxa, including putative sulfur-oxidizing Sulfuriferula spp., appeared to be primarily associated with Duluth Complex rock, but not pyrite-bearing rocks subjected to the same experimental treatment. We discuss the implications of these results for the microbial ecology of moderately acidic mine waste with low sulfide content, as well as for kinetic testing of mine waste. IMPORTANCE Economic sulfide mineral deposits in the Duluth Complex may represent the largest

Behavior of molybdenum in mixed-oxide fuel

International Nuclear Information System (INIS)

Giacchetti, G.; Sari, C.

1976-01-01

Metallic molybdenum, Mo--Ru--Rh--Pd alloys, barium, zirconium, and tungsten were added to uranium and uranium--plutonium oxides by coprecipitation and mechanical mixture techniques. This material was treated in a thermal gradient similar to that existing in fuel during irradiation to study the behavior of molybdenum in an oxide matrix as a function of the O/(U + Pu) ratio and some added elements. Result of ceramographic and microprobe analysis shows that when the overall O/(U + Pu) ratio is less than 2, molybdenum and Mo--Ru--Rh--Pd alloy inclusions are present in the uranium--plutonium oxide matrix. If the O/(U + Pu) ratio is greater than 2, molybdenum oxidizes to MoO 2 , which is gaseous at a temperature approximately 1000 0 C. Molybdenum oxide vapor reacts with barium oxide and forms a compound that exists as a liquid phase in the columnar grain region. Molybdenum oxide also reacts with tungsten oxide (tungsten is often present as an impurity in the fuel) and forms a compound that contains approximately 40 wt percent of actinide metals. The apparent solubility of molybdenum in uranium and uranium--plutonium oxides, determined by electron microprobe, was found to be less than 250 ppM both for hypo- and hyperstoichiometric fuels

Isotope analysis of molybdenum in selected minerals

International Nuclear Information System (INIS)

Becker, S.; Dietze, H.J.

1980-01-01

An analytical method is described for the mass spectrometric determination of molybdenum abundance values. The results of analyses of three molybdenum mineral samples are presented and compared with the results of other authors. It is shown that the fine variations of molybdenum in natural minerals cannot be analysed with currently available mass spectrometers

PGAA method for control of the technologically important elements at processing of sulfide ores

International Nuclear Information System (INIS)

Kurbanov, B.I.; Aripov, G.A.; Allamuratova, G.; Umaraliev, M.

2006-01-01

Full text: Many precious elements (Au, Re, Pt, Pd, Ag, Cu, Ni, Co, Mo) in ores mainly exist in the form of sulfide minerals and the flotation method is often used for processing of such kind of ores. To enhance the efficiency of the process it is very important to carry out the operative control of the elements of interest at various stages of ore processing. In this work the results of studies for developing methods for control of technologically important elements at processing and enrichment sulfide ores, which content the gold, copper, nickel, molybdenum in the ore-processing plants of Uzbekistan. The design of transportable experimental PGAA device on the basis of low-power radionuclide neutron source ( 252 Cf) with neutrons of 2x10 7 neutr/sec allowing to determine element content of the above named ores and their processing products is offered. It is shown that the use of the thermal neutron capture gamma-ray spectrometry in real samples and technological products allows prompt determination of such elements as S, Cu, Ti and others, which are important for flotation of sulfide ores. Efficiency control of the flotation processing of sulfide ores is based on quick determination of the content of sulfur and some other important elements at different stages of the process. It was found that to determine elements the following gamma lines are the most suitable - 840.3 keV for sulfur, 609 keV and 7307 keV for copper and 1381.5 keV, 1498.3 keV and 1585.3 keV for titanium. Based on the measurements of original ores, concentrates of various stages of flotation and flotation slime the possibility for prompt determination of S, Cu and Ti content and thus to get necessary information on the efficiency of the flotation process was shown. (author)

Selenium Sulfide

Science.gov (United States)

Selenium sulfide, an anti-infective agent, relieves itching and flaking of the scalp and removes the dry, ... Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium ...

Neutron diffraction investigations of the superionic conductors lithium sulfide and sodium sulfide

International Nuclear Information System (INIS)

Altorfer, F.

1990-03-01

Statics and dynamics of the superionic conductors lithium sulfide and sodium sulfide were investigated using the following experimental methods: elastic scattering on sodium sulfide powder in the temperature range 20 - 1000 C, elastic scattering on a lithium sulfide single crystal in the temperature range 20 - 700 C, inelastic scattering on a 7 Li 2 S single crystal at 10 K. 34 figs., 2 tabs., 10 refs

Preparation of molybdenum oxide thin films by MOCVD

International Nuclear Information System (INIS)

Guerrero, R. Martinez; Garcia, J.R. Vargas; Santes, V.; Gomez, E.

2007-01-01

In this study, molybdenum oxide films were prepared in a horizontal hot-wall MOCVD apparatus using molybdenum dioxide acetylacetonate as precursor. The molybdenum precursor was synthesized from acetylacetone and molybdenum oxide powder. Thermal gravimetric (TG) and differential thermal analyses (DTA) of the precursor suggested the formation of molybdenum oxides around 430 o C (703 K). Thus, a range of deposition temperatures varying from 350 to 630 o C (623-903 K) was explored to investigate the effects on the nature of the molybdenum oxide films. X-ray diffraction (XRD) results showed that the films consisted of α-MoO 3 phase at deposition temperatures ranging from 400 to 560 o C (673-833 K). Crystalline α-MoO 3 films can be obtained from molybdenum dioxide acetylacetonate precursor, without need of a post-annealing treatment. The best crystalline quality was found in films having needle-like crystallites grown at deposition temperature of about 560 o C (833 K), which exhibit a strong (0 1 0) preferred orientation and a transparent visual appearance

Preparation of molybdenum oxide thin films by MOCVD

Energy Technology Data Exchange (ETDEWEB)

Guerrero, R. Martinez [Depto. de Ingenieria Metalurgica, ESIQIE-IPN, Mexico 07300, D.F. (Mexico); Garcia, J.R. Vargas [Depto. de Ingenieria Metalurgica, ESIQIE-IPN, Mexico 07300, D.F. (Mexico)]. E-mail: rvargasga@ipn.mx; Santes, V. [CIIEMAD-IPN, Miguel Othon de Mendizabal 485, Mexico 07700, D.F. (Mexico); Gomez, E. [Instituto de Quimica-UNAM, Circuito Exterior-Ciudad Universitaria, Mexico 04510, D.F. (Mexico)

2007-05-31

In this study, molybdenum oxide films were prepared in a horizontal hot-wall MOCVD apparatus using molybdenum dioxide acetylacetonate as precursor. The molybdenum precursor was synthesized from acetylacetone and molybdenum oxide powder. Thermal gravimetric (TG) and differential thermal analyses (DTA) of the precursor suggested the formation of molybdenum oxides around 430 {sup o}C (703 K). Thus, a range of deposition temperatures varying from 350 to 630 {sup o}C (623-903 K) was explored to investigate the effects on the nature of the molybdenum oxide films. X-ray diffraction (XRD) results showed that the films consisted of {alpha}-MoO{sub 3} phase at deposition temperatures ranging from 400 to 560 {sup o}C (673-833 K). Crystalline {alpha}-MoO{sub 3} films can be obtained from molybdenum dioxide acetylacetonate precursor, without need of a post-annealing treatment. The best crystalline quality was found in films having needle-like crystallites grown at deposition temperature of about 560 {sup o}C (833 K), which exhibit a strong (0 1 0) preferred orientation and a transparent visual appearance.

Ionic Liquids in Selective Oxidation: Catalysts and Solvents.

Science.gov (United States)

Dai, Chengna; Zhang, Jie; Huang, Chongpin; Lei, Zhigang

2017-05-24

Selective oxidation has an important role in environmental and green chemistry (e.g., oxidative desulfurization of fuels and oxidative removal of mercury) as well as chemicals and intermediates chemistry to obtain high-value-added special products (e.g., organic sulfoxides and sulfones, aldehydes, ketones, carboxylic acids, epoxides, esters, and lactones). Due to their unique physical properties such as the nonvolatility, thermal stability, nonexplosion, high polarity, and temperature-dependent miscibility with water, ionic liquids (ILs) have attracted considerable attention as reaction solvents and media for selective oxidations and are considered as green alternatives to volatile organic solvents. Moreover, for easy separation and recyclable utilization, IL catalysts have attracted unprecedented attention as "biphasic catalyst" or "immobilized catalyst" by immobilizing metal- or nonmetal-containing ILs onto mineral or polymer supports to combine the unique properties of ILs (chemical and thermal stability, capacity for extraction of polar substrates and reaction products) with the extended surface of the supports. This review highlights the most recent outcomes on ILs in several important typical oxidation reactions. The contents are arranged in the series of oxidation of sulfides, oxidation of alcohols, epoxidation of alkenes, Baeyer-Villiger oxidation reaction, oxidation of alkanes, and oxidation of other compounds step by step involving ILs as solvents, catalysts, reagents, or their combinations.

Syntheses, Characterization and Kinetics of Nickel-Tungsten Nitride Catalysts for Hydrotreating of Gas Oil

Science.gov (United States)

Botchwey, Christian

This thesis summarizes the methods and major findings of Ni-W(P)/gamma-Al 2O3 nitride catalyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts' activities to their synthesis parameters and properties. The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, transmission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: temperature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydrogen to oil ratio (600 ml/ml, STP). The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al 2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity increased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide. The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed

Removal of H₂S from Biogas by Iron (Fe³⁺ Doped MgO on Ceramic Honeycomb Catalyst using Double Packed Columns System

Directory of Open Access Journals (Sweden)

Juntima Chungsiriporn

2010-03-01

Full Text Available Hydrogen sulfide is a toxic and corrosive in nature, gas should be safely removed from the biogas streams before subjecting into the fuel cell. Fe3+ doped magnesium oxide was synthesized using sol-gel technique and dip coating process of Fe3+ doped MgO on foam ceramic honeycomb. XRD and SEM indicate that Fe3+ in Fe3+ doped MgO on foam ceramic honeycomb catalyst is finely dispersed in the MgO support. Performance of the synthesized Fe3+ doped magnesium oxide on the honeycomb catalyst was examined for hydrogen sulfide (H2S oxidation by double packed column scrubbers. The absorption column was used for H2S scrubbing from biogas by deionized water absorption and catalytic column was used as catalyst bed for degradation of absorbed H2S in scrubbing water. In the catalytic column, counter current flow of the scrubbing water and air through the catalyst pack was performed for H2S oxidation accompany with catalyst regeneration. System capacity for H2S removal from gas stream showed 98% constant along 3 hr testing time at room temperature.

Features of the kinetics of heterogeneous reactions with phase transformations on catalyst surfaces

Energy Technology Data Exchange (ETDEWEB)

Berman, A D; Krylov, O V

1978-01-01

This paper presents a review of 41 bibliographic references to experiments on the adsorption of various gases (e.g., carbon monoxide, formic acid, ammonia, and oxygen) on metals (e.g., nickel, molybdenum, and platinum) and oxides covers observations of two-dimensional phases during adsorption; the kinetics of adsorption and catalysis associated with two-dimensional phase transitions; and several approximate models for describing the kinetics of heterogeneous catalysis which account for two-dimensional phase transformations on catalyst surfaces.

Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

Science.gov (United States)

Gardner, Todd H.

2015-09-15

Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

THE ECONOMICAL PRODUCTION OF ALCOHOL FUELS FROM COAL-DERIVED SYNTHESIS GAS. Includes quarterly technical progress report No.25 from 10/01/1997-12/31/1997, and quarterly technical progress report No.26 from 01/01/1998-03/31/1998

Energy Technology Data Exchange (ETDEWEB)

None

1999-03-01

This project was divided into two parts. One part evaluated possible catalysts for producing higher-alcohols (C{sub 2} to C{sub 5+}) as fuel additives. The other part provided guidance by looking both at the economics of mixed-alcohol production from coal-derived syngas and the effect of higher alcohol addition on gasoline octane and engine performance. The catalysts studied for higher-alcohol synthesis were molybdenum sulfides promoted with potassium. The best catalysts produced alcohols at a rate of 200 g/kg of catalyst/h. Higher-alcohol selectivity was over 40%. The hydrocarbon by-product was less than 20%. These catalysts met established success criteria. The economics for mixed alcohols produced from coal were poor compared to mixed alcohols produced from natural gas. Syngas from natural gas was always less expensive than syngas from coal. Engine tests showed that mixed alcohols added to gasoline significantly improved fuel quality. Mixed-alcohols as produced by our catalysts enhanced gasoline octane and decreased engine emissions. Mixed-alcohol addition gave better results than adding individual alcohols as had been done in the 1980's when some refiners added methanol or ethanol to gasoline.

THE ECONOMICAL PRODUCTION OF ALCOHOL FUELS FROM COAL-DERIVED SYNTHESIS GAS. Includes quarterly technical progress report No.25 from 10/01/1997-12/31/1997, and quarterly technical progress report No.26 from 01/01/1998-03/31/1998; FINAL

International Nuclear Information System (INIS)

1999-01-01

This project was divided into two parts. One part evaluated possible catalysts for producing higher-alcohols (C(sub 2) to C(sub 5+)) as fuel additives. The other part provided guidance by looking both at the economics of mixed-alcohol production from coal-derived syngas and the effect of higher alcohol addition on gasoline octane and engine performance. The catalysts studied for higher-alcohol synthesis were molybdenum sulfides promoted with potassium. The best catalysts produced alcohols at a rate of 200 g/kg of catalyst/h. Higher-alcohol selectivity was over 40%. The hydrocarbon by-product was less than 20%. These catalysts met established success criteria. The economics for mixed alcohols produced from coal were poor compared to mixed alcohols produced from natural gas. Syngas from natural gas was always less expensive than syngas from coal. Engine tests showed that mixed alcohols added to gasoline significantly improved fuel quality. Mixed-alcohols as produced by our catalysts enhanced gasoline octane and decreased engine emissions. Mixed-alcohol addition gave better results than adding individual alcohols as had been done in the 1980's when some refiners added methanol or ethanol to gasoline

Preparation, Characterization, and Catalytic Activity of MoCo/USY Catalyst on Hydrodeoxygenation Reaction of Anisole

Science.gov (United States)

Nugrahaningtyas, K. D.; Suharbiansah, R. S. R.; Rahmawati, F.

2018-03-01

This research aims to prepare, characterize, and study the catalytic activity of Molybdenum (Mo) and Cobalt (Co) metal with supporting material Ultra Stable Y-Zeolite (USY), to produce catalysts with activity in hydrotreatment reaction and in order to eliminate impurities compounds that containing unwanted groups heteroatoms. The bimetallic catalysts MoCo/USY were prepared by wet impregnation method with weight variation of Co metal 0%, 2%, 4%, 6%, 8%, and Mo metal 8% (w/w), respectively. Activation method of the catalyst included calcination, oxidation, reduction and the crystallinity was characterized using X-ray diffraction (XRD), the acidity of the catalyst was analyzed using Fourier Transform Infrared Spectroscopy (FT-IR) and gravimetry method, minerals present in the catalyst was analyzed using X-Ray Fluorescence (XRF), and surface of the catalyst was analyzed using Surface Area Analyzer (SAA). Catalytic activity test (benzene yield product) of MoCo/USY on hydrodeoxigenation reaction of anisole aimed to determine the effect of Mo-Co/USY for catalytic activity in the reaction hydrodeoxigenation (HDO) anisole. Based on characterization and test of catalytic activity, it is known that catalytic of MoCo/USY 2% (catalyst B) shows best activities with acidity of 10.209 mmol/g, specific area of catalyst of 426.295 m2/g, pore average of 14.135 Å, total pore volume 0.318 cc/g, and total yield of HDO products 6.06%.

Hydrogenation of fructose to 2,5-dimethyltetrahydrofuran using a sulfur poisoned Pt/C catalyst

Science.gov (United States)

In order to expand the number of biobased chemicals available, fructose has been hydrogenated to 2,5-dimethyltetrahydrofuran using a sulfided Pt/C catalyst. The reaction was carried out in a stirred reactor at 10.3 MPa H2 and 175°C which allowed a 10% fructose solution to be converted in about 2 h. ...

Molybdenum sealing glass-ceramic composition

International Nuclear Information System (INIS)

Eagan, R.J.

1976-01-01

A glass-ceramic composition is described having low hydrogen and helium permeability properties, along with high fracture strength, and a thermal coefficient of expansion similar to that of molybdenum. The composition is adaptable for hermetically sealing to molybdenum at temperatures between 900 and about 950 0 C to form a hermetically sealed insulator body

Development of Silicide Coating on Molybdenum Alloy Cladding

International Nuclear Information System (INIS)

Lim, Woojin; Ryu, Ho Jin

2015-01-01

The molybdenum alloy is considered as one of the accident tolerant fuel (ATF) cladding materials due to its high temperature mechanical properties. However, molybdenum has a weak oxidation resistance at elevated temperatures. To modify the oxidation resistance of molybdenum cladding, silicide coating on the cladding is considered. Molybdenum silicide layers are oxidized to SiO 2 in an oxidation atmosphere. The SiO 2 protective layer isolates the substrate from the oxidizing atmosphere. Pack cementation deposition technique is widely adopted for silicide coating for molybdenum alloys due to its simple procedure, homogeneous coating quality and chemical compatibility. In this study, the pack cementation method was conducted to develop molybdenum silicide layers on molybdenum alloys. It was found that the Mo 3 Si layer was deposited on substrate instead of MoSi 2 because of short holding time. It means that through the extension of holding time, MoSi 2 layer can be formed on molybdenum substrate to enhance the oxidation resistance of molybdenum. The accident tolerant fuel (ATF) concept is to delay the process following an accident by reducing the oxidation rate at high temperatures and to delay swelling and rupture of fuel claddings. The current research for Atf can be categorized into three groups: First, modification of existing zirconium-based alloy cladding by improving the high temperature oxidation resistance and strength. Second, replacing Zirconium based alloys with alternative metallic materials such as refractory elements with high temperature oxidation resistance and strength. Third, designing alternative fuel structures using ceramic and composite systems

High strength tungsten heavy alloys with molybdenum additions

International Nuclear Information System (INIS)

Bose, A.; Sims, D.M.; German, R.M.

1987-01-01

Tungsten heavy alloys are candidates for numerous applications based on the unique combination of high density, high strength, and high ductility coupled with excellent machinability. Though there has been considerable research on heavy alloys, the primary focus has been on the ductility. These alloys are well suited for ballistic uses due to their high densities and it is expected that for superior ballistic performance, a high hardness, high strength and moderate ductility alloy would be ideal. The major goal of this investigation was to obtain heavy alloys with hardness greater than HRA 72. It is evident from the phase diagrams that molybdenum, which goes into solution in tungsten, nickel and iron, could act as a potential strengthening addition. With this in view, tungsten heavy alloys with molybdenum additions were fabricated from mixed elemental powders. A baseline composition of 90W-7Ni-3Fe was chosen to its good elongation and moderate strength. The molybdenum additions were made by replacing the tungsten. Compared to the baseline properties with no molybdenum addition, the strength and hardness showed a continuous increase with molybdenum addition. The ductility of the alloy continued to decrease with increasing molybdenum content, but even with 16% wt. % molybdenum of the elongation was still around 6%. An interesting facet of these alloying additions is the grain refinement that is brought about by adding to molybdenum to the system. The grain refinement is related to the lower solubility of tunbsten in the matrix due to partial displacement by molybdenum

Method of molybdenum kinetic determination

International Nuclear Information System (INIS)

Krejngol'd, S.U.; Dzotsenidze, N.E.; Ruseishviyai, T.G.; Nelen', I.M.

1980-01-01

The method molybdenum kinetic determination according to oxidation of pyrogallol with bromate in the medium of 0.05-0.15 M perchloric or sulphuric acids is presented. 1 mg of Ni, Co, Mn, Mg, Zn, Cr(3); 100 μg of Ca, Al, Cu, 10 μg of Cr(4), W; 10 μg of Fe in the presence of 22x10 - 4 M solution of EDTA, as well as 10 - 4 M solutions of chlorides and fluorides, 10 - 5 M solutions of bromides do not interfere with molybdenum determination using the given method. The method is rather simple, it takes 30 min to carry out the analysis. Determination limit of molybdenum constitutes 0.01 μg/ml

Large-Batch Reduction of Molybdenum Trioxide

Energy Technology Data Exchange (ETDEWEB)

Kiggans, Jr, James O. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lowden, Richard Andrew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Menchhofer, Paul A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nunn, Stephen D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bryan, Chris [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-12-01

Unconverted, isotopically-enriched molybdenum metal must be recovered from the spent radiopharmaceutical solution used in NorthStar’s Technetium-99m generator and reused. The recycle process begins by recovering the metal from the aqueous potassium molybdate (K₂MoO₄) solutions as molybdenum trioxide (MoO₃) employing a process developed at Argonne National Laboratory. The MoO₃ powder is subsequently reduced to molybdenum metal powder which can be blended with new powder and further processed into a flowable form to be used to produce target disks for irradiation. The molybdenum oxide reduction process has been examined and scaled to produce kilogram quantities of metal powder suitable for processing into a useable form employing spray drying or similar technique and ultimately used for target fabrication.

Process for separation of tungsten and molybdenum by extraction

International Nuclear Information System (INIS)

Zelikman, A.N.; Voldman, G.M.; Rumyantsev, V.K.; Ziberov, G.N.; Kagermanian, V.S.

1976-01-01

A process for the separation of tungsten and molybdenum by extraction involves the addition of HCl or HNO 3 to an aqueous solution containing tungsten and molybdenum to obtain a pH from 0.5 to 4.3, and introduction of a stabilizer comprising water-soluble phosphorus salts and a complexing agent, hydrogen peroxide, in an amount from 1.5 to 2 mole per 1 g-atom of the total content of tungsten and molybdenum. Then molybdenum is selectively extracted from the resulting aqueous solution with tri-n-butylphosphate with equal volumetric proportioning of the aqueous and organic solutions. Re-extraction of molybdenum and partially tungsten is carried out from the organic extracting agent with an alkali or soda solution. The process makes possible the preparation of tungsten solution containing no more than 0.001 g/l of molybdenum, and an increase in the degree of extraction of tungsten and molybdenum

Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst.

Science.gov (United States)

Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Michał; Skupiński, Wincenty

2011-11-15

A new catalyst, H(3)PO(4)/MoO(3)/SiO(2), was prepared by modification of MoO(3)/SiO(2) using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds. Copyright © 2011 Elsevier B.V. All rights reserved.

Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase

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Alessandra Magistrato

2011-01-01

Full Text Available The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen ‘fixation’ via an iron molybdenum cofactor (FeMo-co under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N2 to various degrees. However, to date Mo(N2(HIPTN3N with (HIPTN3N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N2. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase*

Science.gov (United States)

Mishanina, Tatiana V.; Yadav, Pramod K.; Ballou, David P.; Banerjee, Ruma

2015-01-01

The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be −123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. PMID:26318450

Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase.

Science.gov (United States)

Mishanina, Tatiana V; Yadav, Pramod K; Ballou, David P; Banerjee, Ruma

2015-10-09

The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be -123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Effect of molybdenum and iron supply on molybdenum (99Mo) and iron (59Fe) uptake and activity of certain enzymes in tomato plants grown in sand culture

International Nuclear Information System (INIS)

Chatterjee, C.; Agarwala, S.C.

1979-01-01

Tomato (Lycopersicon esculentum Mill. var. Marglobe) plants were raised under controlled sand culture to study the interaction of molybdenum and iron supply on the uptake of molybdenum and iron and activity of certain enzymes affected by iron and/or molybdenum supply. Iron deficiency caused a decrease in the molybdenum uptake and accentuated the effect of molybdenum deficiency in reducing the uptake and more so the translocation of molybdenum from roots to shoots, thus inducing more severe molybdenum deficiency. The deficiency of iron and molybdenum decreased the activity of catalase, succinate dehydrogenase and nitrate reductase, the most marked decrease being found in plants supplied with both iron and molybdenum at low levels. Changes in the activities of nitrate reductase and catalase can be attributed to the interaction of iron and molybdenum supply in their absorption and translocation. (auth.)

Molybdenum-A Key Component of Metal Alloys

Science.gov (United States)

Kropschot, S.J.

2010-01-01

Molybdenum, whose chemical symbol is Mo, was first recognized as an element in 1778. Until that time, the mineral molybdenite-the most important source of molybdenum-was believed to be a lead mineral because of its metallic gray color, greasy feel, and softness. In the late 19th century, French metallurgists discovered that molybdenum, when alloyed (mixed) with steel in small quantities, creates a substance that is remarkably tougher than steel alone and is highly resistant to heat. The alloy was found to be ideal for making tools and armor plate. Today, the most common use of molybdenum is as an alloying agent in stainless steel, alloy steels, and superalloys to enhance hardness, strength, and resistance to corrosion.

TiO2 nanotubes supported NiW hydrodesulphurization catalysts: Characterization and activity

International Nuclear Information System (INIS)

Palcheva, R.; Dimitrov, L.; Tyuliev, G.; Spojakina, A.; Jiratova, K.

2013-01-01

Highlights: ► NiW catalysts supported on TiO 2 nanotubes, titania and alumina. ► The best results are obtained with NiW/TiO 2 nanotubes in hydrodesulfurization (HDS) of thiophene. ► Active phase is Ni-WO x S y . ► Electronic promotion of W by Ti. - Abstract: High surface area TiO 2 nanotubes (Ti-NT) synthesized by alkali hydrothermal method were used as a support for NiW hydrodesulphurization catalyst. Nickel salt of 12-tungstophosphoric acid – Ni 3/2 PW 12 O 40 was applied as oxide precursor of the active components. The catalyst was characterized by S BET , XRD, UV–vis DRS, Raman spectroscopy, XPS, TPR and HRTEM. The results obtained were compared with those for the NiW catalysts prepared over high surface area titania and alumina supports. A polytungstate phase evidenced by Raman spectroscopy was observed indicating the destruction of the initial heteropolyanion. The catalytic experiments revealed two times higher thiophene conversion on NiW catalyst supported on Ti-NT than those of catalysts supported on alumina and titania. Increased HDS activity of the NiW catalyst supported on Ti-NT could be related to a higher amount of W oxysulfide entities interacting with Ni sulfide particles as consequence of the electronic effects of the Ti-NT observed with XPS analysis.

Molybdenum solar neutrino experiment

International Nuclear Information System (INIS)

Wolfsberg, K.; Cowan, G.A.; Bryant, E.A.

1984-01-01

The goal of the molybdenum solar neutrino experiment is to deduce the 8 B solar neutrino flux, averaged over the past several million years, from the concentration of 98 Tc in a deeply buried molybdenum deposit. The experiment is important to an understanding of stellar processes because it will shed light on the reason for the discrepancy between theory and observation of the chlorine solar neutrino experiment. Possible reasons for the discrepancy may lie in the properties of neutrinos (neutrino oscillations or massive neutrinos) or in deficiencies of the standard solar model. The chlorine experiment only measures the 8 B neutrino flux in current times and does not address possible temporal variations in the interior of the sun, which are also not considered in the standard model. In the molybdenum experiment, we plan to measure 98 Tc (4.2 Myr), also produced by 8 B neutrinos, and possibly 97 Tc (2.6 Myr), produced by lower energy neutrinos

Catalytic upgrading of oleic acid into biofuel using Mo modified zeolite supported Ni oxalate catalyst functionalized with fluoride ion

International Nuclear Information System (INIS)

Ayodele, O.B.; Abbas, Hazzim F.; Daud, Wan Mohd Ashri Wan

2014-01-01

Highlights: • Modification of zeolite with freshly prepared molybdenum oxalate. • Functionalization of Ni oxalate with HF and incorporation into Mo modified zeolite. • Characterization of synthesized Mo modified zeolite supported Ni oxalate catalyst. • Deoxygenation of oleic acid with the synthesized zeolite supported catalyst. • Reusability study on the synthesized zeolite supported catalyst. - Abstract: In this study, fluoride ion functionalized nickel oxalate supported on molybdenum modified zeolite (NiMoFOx/Zeol) catalyst was synthesized, characterized and tested on the hydrodeoxygenation (HDO) of oleic acid (OA) into paraffinic fuel. The NiMoFOx/Zeol characterization results confirmed the presence of both Ni and Mo as well as the formation of NiMoO 4 which is a highly HDO reactive specie at 2θ value of 43.6° according to the XRD result. NiMoFOx/Zeol also showed loss in crystallinity and reduction in the average particle size leading to increase in the pore volume and specific surface area due to the combined effects of fluoride ion presence, oxalic acid functionalization and calcination. The effect of temperature, pressure and NiMoFOx/Zeol loading studied showed that initial increase in their values increased the yield of the target fractions until some points where reduction was observed. The best observed experimental conditions to hydrodeoxygenate 40 g (∼45 mL) of OA into 75% n-C 18 and 23% i-C 18 were 360 °C, 30 mg NiMoFOx/Zeol loading and 20 bar using 100 mL H 2 /min. The presence of i-C 18 was due to the functionalization of the catalyst with fluoride ion. The catalyst reusability result displayed excellent qualities with marginal loss of only 2% in activity after third reuse due to the improved synthesis protocol that employed organometallic precursor. The results are strongly encouraging for further studies toward industrialization of HDO process

SULFIDE MINERALS IN SEDIMENTS

Science.gov (United States)

The formation processes of metal sulfides in sediments, especially iron sulfides, have been the subjects of intense scientific research because of linkages to the global biogeochemical cycles of iron, sulfur, carbon, and oxygen. Transition metal sulfides (e.g., NiS, CuS, ZnS, Cd...

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1993

Energy Technology Data Exchange (ETDEWEB)

Schmidt, E.; Kirby, S.; Song, Chunshan; Schobert, H.H.

1994-04-01

Development of new catalysts is a promising approach to more, efficient coal liquefaction. It has been recognized that dispersed catalysts can be superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires infinite contact between the catalyst and coal. The primary objective of this research is to explore the potential of bimetallic dispersed catalysts from heterometallic molecular precursors in their use in model compound liquefaction reactions. This quarterly report describes the use of three precursors in model compound reactions. The first catalyst is a heterometallic complex consisting of two transition metals, Mo and Ni, and sulfur in a single molecule. The second is a thiocubane type complex consisting of cobalt, molybdenum and sulfur. The third is a thiocubane type cluster consisting of iron and sulfur and the fourth, the pure inorganic salt ammonium tetrathiomolybdate (ATM). It was found that the structure and the ligands in the model complexes affect the activity of the resulting catalyst significantly. The optimum reaction at a pressure of 6.9 MPa hydrogen gas varied for different catalysts. The bimetallic catalysts generated in situ from the organometallic precursor are more active than monometallic catalysts like ATTM and the thiocubane type cluster Fe{sub 4}. Main products are hydrogenated phenanthrene derivatives, like DBP, THP, sym-OHP, cis- and trans-unsym-OHP with minor isomerization products such as sym-OHA. Our results indicate that other transition metal and ligand combinations in the organometallic precursors and the use of another model compound could result in substantially higher conversion activity.

Determination of molybdenum by the gravimetric plumbate method (with the molybdenum content from 50 % and above)

International Nuclear Information System (INIS)

Stepin, V.V.; Kurbatova, V.I.; Fedorova, N.D.

1980-01-01

A gravimetric method of molybdenum determination in ferromolybdenum (Mo content from 50% and higher) after its dissolving in HNO 3 is developed. The method is based on Mo deposition in acetic acid solution in the form of molybdenum oxide lead after separation of Fe and other interfering elements with sodium hydroxide [ru

Thermodynamic Properties of Manganese and Molybdenum

International Nuclear Information System (INIS)

Desai, P.D.

1987-01-01

This work reviews and discusses the data on the various thermodynamic properties of manganese and molybdenum available through March 1985. These include heat capacity, enthalpy, enthalpy of transitions and melting, vapor pressure, and enthalpy of vaporization. The existing data have been critically evaluated and analyzed. The recommended values for the heat capacity, enthalpy, entropy, and Gibbs energy function from 0.5 to 2400 K for manganese and from 0.4 to 5000 K for molybdenum have been generated, as have heat capacity values for supercooled β-Mn and for γ-Mn below 298.15 K. The recommended values for vapor pressure cover the temperature range from 298.15 to 2400 K for manganese and from 298.15 to 5000 K for molybdenum. These values are referred to temperatures based on IPTS-1968. The uncertainties in the recommended values of the heat capacity range from +-3% to +-5% for manganese and from +-1.5% to +-3% for molybdenum

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October 1995--December 1995

Energy Technology Data Exchange (ETDEWEB)

Song, C.; Cooke, W.S.; Schmidt, E.; Schobert, H.H.

1996-02-01

Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. Here in this quarterly, we report on the catalytic effects of several molybdenum-, cobalt-, and iron-containing compounds in the reactions of dibenzothiophene (DBT) with hydrogen under conditions related to coal liquefaction. The catalytic effects of several molybdenum-, cobalt-, and iron-containing compounds have been examined in the hydrogenation and hydrodesulfurization reactions of dibenzothiophene (DBT) under conditions related to coal liquefaction. The metal compounds are candidate catalyst precursors for direct coal liquefaction. The reactions were carried out in batch microautoclave reactors at 400{degrees}C for 30 minutes with 6.9 MPa (cold) hydrogen pressure, and tridecane solvent. A metal loading of 0.5 mol% resulted in low conversion and only hydrogenation. Addition of sulfur in 4:1 molar ratio led only to a minor increase in conversion and hydrodesulfurization. The use of a higher boiling solvent (octadecane vs. tridecane) was beneficial in providing increased conversion, hydrodesulfurization, and hydrogenation. An increase in metal compound loading to 36.2 mol% led to a dramatic increase in conversion, hydrodesulfurization, and hydrocracking. Molybdenum hexacarbonyl at 36 mol% loading, with added sulfur at 6:1 ratio and octadecane solvent, gave 100% conversion of dibenzothiophene to other products with 100% hydrodesulfurization. Ammonium tetrathiomolybdate and molybdenum(III) chloride are less active under similar conditions. A cobalt-molybdenum thiocubane complex gave unexpectedly low conversions. Iron and cobalt carbonyls also provided very low conversions, even with added sulfur.

Vapor phase carbonylation of dimethyl ether and methyl acetate with supported transition metal catalysts

International Nuclear Information System (INIS)

Shikada, T.; Fujimoto, K.; Tominaga, H.O.

1986-01-01

The synthesis of acetic acid (AcOH) from methanol (MeOH) and carbon monoxide has been performed industrially in the liquid phase using a rhodium complex catalyst and an iodide promoter. The selectivity to AcOH is more than 99% under mild conditions (175 0 C, 28 atm). The homogeneous rhodium catalyst has been also effective for the synthesis of acetic anhydride (Ac 2 O) by carbonylation of dimethyl ether (DME) or methyl acetate (AcOMe). However, rhodium is one of the most expensive metals and its proved reserves are quite limited. It is highly desired, therefore, to develop a new catalyst as a substitute for rhodium. The authors have already reported that nickel supported on active carbon exhibits an excellent activity for the vapor phase carbonylation of MeOh in the presence of iodide promoter and under moderately pressurized conditions. In addition, corrosive attack on reactors by iodide compounds is expected to be negligible in the vapor phase system. In the present work, vapor phase carbonylation of DME and AcOMe on nickel-active carbon (Ni/A.C.) and molybdenum-active carbon (Mo/A.C.) catalysts was studied

Permanganate oxidation of sulfur compounds to prevent poisoning of Pd catalysts in water treatment processes.

Science.gov (United States)

Angeles-Wedler, Dalia; Mackenzie, Katrin; Kopinke, Frank-Dieter

2008-08-01

The practical application of Pd-catalyzed water treatment processes is impeded by catalyst poisoning by reduced sulfur compounds (RSCs). In this study, the potential of permanganate as a selective oxidant for the removal of microbially generated RSCs in water and as a regeneration agent for S-poisoned catalysts was evaluated. Hydrodechlorination using Pd/Al2O3 was carried out as a probe reaction in permanganate-pretreated water. The activity of the Pd catalysts in the successfully pretreated reaction medium was similar to that in deionized water. The catalyst showed no deactivation behavior in the presence of permanganate at a concentration level or = 0.08 mM, a significant but temporary inhibition of the catalytic dechlorination was observed. Unprotected Pd/Al2O3, which had been completely poisoned by sulfide, was reactivated by a combined treatment with permanganate and hydrazine. However, the anthropogenic water pollutants thiophene and carbon disulfide were resistant against permanganate. Together with the preoxidation of catalyst poisons, hydrophobic protection of the catalysts was studied. Pd/zeolite and various hydrophobically coated catalysts showed a higher stability against ionic poisons and permanganate than the uncoated catalyst. By means of a combination of oxidative water pretreatment and hydrophobic catalyst protection, we provide a new tool to harness the potential of Pd-catalyzed hydrodehalogenation for the treatment of real waters.

Molybdenum-UO2 cermet irradiation at 1145 K.

Science.gov (United States)

Mcdonald, G.

1971-01-01

Two molybdenum-uranium dioxide cermet fuel pins with molybdenum clad were fission-heated in a forced-convection helium coolant for sufficient time to achieve 5.3% burnup. The cermet core contained 20 wt % of 93.2% enriched uranium dioxide. The results were as follows: there was no visible change in the appearance of the molybdenum clad during irradiation; the maximum increase in diameter of the fuel pins was 0.8%; there was no migration of uranium dioxide along grain boundaries and no evident interaction between molybdenum and uranium dioxide; and, finally, approximately 12% of the fission gas formed was released from the cermet core into the gas plenum.

Spheroidization of molybdenum powder by radio frequency thermal plasma

Science.gov (United States)

Liu, Xiao-ping; Wang, Kuai-she; Hu, Ping; Chen, Qiang; Volinsky, Alex A.

2015-11-01

To control the morphology and particle size of dense spherical molybdenum powder prepared by radio frequency (RF) plasma from irregular molybdenum powder as a precursor, plasma process parameters were optimized in this paper. The effects of the carrier gas flow rate and molybdenum powder feeding rate on the shape and size of the final products were studied. The molybdenum powder morphology was examined using high-resolution scanning electron microscopy. The powder phases were analyzed by X-ray diffraction. The tap density and apparent density of the molybdenum powder were investigated using a Hall flow meter and a Scott volumeter. The optimal process parameters for the spherical molybdenum powder preparation are 50 g/min powder feeding rate and 0.6 m3/h carrier gas rate. In addition, pure spherical molybdenum powder can be obtained from irregular powder, and the tap density is enhanced after plasma processing. The average size is reduced from 72 to 62 µm, and the tap density is increased from 2.7 to 6.2 g/cm3. Therefore, RF plasma is a promising method for the preparation of high-density and high-purity spherical powders.

Synthesis and characterization of ternary Pt-Ni-M/C (M=Cu, Fe, Ce, Mo, W) nano-catalysts for low temperature fuel cells

International Nuclear Information System (INIS)

Ahmed, Riaz; Jamil, Rabia; Ansari, Muhammad Shahid

2014-01-01

Ternary metal catalysts were synthesized by impregnation method. The mixture of metal solutions was reduced slowly under inert atmosphere and the reduced metals were deposited on the Vulcan Carbon(VC). Tungsten, molybdenum, cerium, iron and copper were added to specified amounts of platinum and nickel. Addition of nickel generally improves catalytic activity of platinum. The XRD of the catalysts was done and the crystallite size and other parameters were calculated. Crystallite sizes were in the range of 5 to 16 nm. Electrochemical surface areas of the catalysts were determined by cyclic voltammetry (CV) in acidic media and are compared. Electro oxidation of methanol on the catalysts was done and peak potential, peak current, mass activity of the catalysts were calculated and are compared. These parameters were determined in acidic and basic media. It was found that mass activity increased significantly in basic media. Rate constants for the electro oxidation of methanol were also calculated in acidic and basic media and are compared and discussed. Rate constants were generally higher in basic media. Ternary catalysts showed improved catalytic activity than the binary catalyst. Nano alloying improved the catalytic activity and stability of the ternary catalysts

Features of soldering of molybdenum a lols

International Nuclear Information System (INIS)

Grishin, V.L.; Rybkin, B.V.; Cherkasov, A.F.

1980-01-01

Soldering features of complex-alloy molybdenum alloys were investigated in comparison with alloys based on solid solutions. Soldering features of heterogeneous molybdenum base alloys were investigated using samples of 0.5-1.O mm sheets with the strain of about 95% made of ingots which had been smelted in arc vacuum furnaces. The soldering of samples was carried out in 5x1O -5 mm Hg vacuum using different sources of heating: radiation, electron-ray and contact. It was shown that heat-resisting soldered joints of heterogeneous molybdenum alloys could be produced using zirconium and niobium base solders containing the most effective hardeners of the parent material (titanum, vanadium, tantalum, molybdenum, tungsten). To preserve high mechanical properties of heterogeneous alloys it was expedient to use for welding local heating sources which permitted to decrease considerably temperature- time conditions of the process

Dual-Function Metal-Organic Framework as a Versatile Catalyst for Detoxifying Chemical Warfare Agent Simulants.

Science.gov (United States)

Liu, Yangyang; Moon, Su-Young; Hupp, Joseph T; Farha, Omar K

2015-12-22

The nanocrystals of a porphyrin-based zirconium(IV) metal-organic framework (MOF) are used as a dual-function catalyst for the simultaneous detoxification of two chemical warfare agent simulants at room temperature. Simulants of nerve agent (such as GD, VX) and mustard gas, dimethyl 4-nitrophenyl phosphate and 2-chloroethyl ethyl sulfide, have been hydrolyzed and oxidized, respectively, to nontoxic products via a pair of pathways catalyzed by the same MOF. Phosphotriesterase-like activity of the Zr6-containing node combined with photoactivity of the porphyrin linker gives rise to a versatile MOF catalyst. In addition, bringing the MOF crystals down to the nanoregime leads to acceleration of the catalysis.

Feasibility of preparing patterned molybdenum coatings on bismuth telluride thermoelectric modules.

Energy Technology Data Exchange (ETDEWEB)

Sarobol, Pylin; Hall, Aaron Christopher; Miller, Stephen Samuel; Knight, Marlene E.; LePage, William S.; Sobczak, Catherine Elizabeth.; Wesolowski, Daniel Edward

2013-09-01

Molybdenum electrical interconnects for thermoelectric modules were produced by air plasma spraying a 30%CE%BCm size molybdenum powder through a laser-cut Kapton tape mask. Initial feasibility demonstrations showed that the molybdenum coating exhibited excellent feature and spacing retention (~170%CE%BCm), adhered to bismuth-telluride, and exhibited electrical conductivity appropriate for use as a thermoelectric module interconnect. A design of experiments approach was used to optimize air plasma spray process conditions to produce a molybdenum coating with low electrical resistivity. Finally, a molybdenum coating was successfully produced on a fullscale thermoelectric module. After the addition of a final titanium/gold layer deposited on top of the molybdenum coating, the full scale module exhibited an electrical resistivity of 128%CE%A9, approaching the theoretical resistivity value for the 6mm module leg of 112%CE%A9. Importantly, air plasma sprayed molybdenum did not show significant chemical reaction with bismuth-telluride substrate at the coating/substrate interface. The molybdenum coating microstructure consisted of lamellar splats containing columnar grains. Air plasma sprayed molybdenum embedded deeply (several microns) into the bismuth-telluride substrate, leading to good adhesion between the coating and the substrate. Clusters of round pores (and cracks radiating from the pores) were found immediately beneath the molybdenum coating. These pores are believed to result from tellurium vaporization during the spray process where the molten molybdenum droplets (2623%C2%B0C) transferred their heat of solidification to the substrate at the moment of impact. Substrate cooling during the molybdenum deposition process was recommended to mitigate tellurium vaporization in future studies.

Metal leaching from refinery waste hydroprocessing catalyst.

Science.gov (United States)

Marafi, Meena; Rana, Mohan S

2018-05-18

The present study aims to develop an eco-friendly methodology for the recovery of nickel (Ni), molybdenum (Mo), and vanadium (V) from the refinery waste spent hydroprocessing catalyst. The proposed process has two stages: the first stage is to separate alumina, while the second stage involves the separation of metal compounds. The effectiveness of leaching agents, such as NH 4 OH, (NH 4 ) 2 CO 3 , and (NH 4 ) 2 S 2 O 8 , for the extraction of Mo, V, Ni, and Al from the refinery spent catalyst has been reported as a function of reagent concentration (0.5 to 2.0 molar), leaching time (1 to 6 h), and temperature (35 to 60°C). The optimal leaching conditions were achieved to obtain the maximum recovery of Mo, Ni, and V metals. The effect of the mixture of multi-ammonium salts on the metal extraction was also studied, which showed an adverse effect for Ni and V, while marginal improvement was observed for Mo leaching. The ammonium salts can form soluble metal complexes, in which stability or solubility depends on the nature of ammonium salt and the reaction conditions. The extracted metals and support can be reused to synthesize a fresh hydroprocessing catalyst. The process will reduce the refinery waste and recover the expensive metals. Therefore, the process is not only important from an environmental point of view but also vital from an economic perspective.

Some problems of manufacturing and industrial application of CoMo-Al2O3 catalyst

International Nuclear Information System (INIS)

Walendziewski, J.

1991-01-01

The monograph presents results of studies of some selected problems relating to CoMo-Al 2 O 3 catalyst: method of production alumina support and catalyst; application of catalyst in the selected hydro refining processes; physicochemical properties of the used catalyst; reclamation of metal compounds from the spent catalyst. Results of investigations of catalyst preparation illustrate how the physicochemical properties of alumina support and catalyst, mainly porous structure could be controlled by the selection of raw materials and parameters of aluminum hydroxide precipitation, method of forming and calcination temperature of support. Application of the catalyst of modified porous structure has shown its high activity in hydro refining process of light cracking catalytic oil (over 95% hydrodesulphurization) and mild hydro cracking process of vacuum gas oil (sulphur content in product below 0.03% wt.). As an effect of studying of hydro refining process of aromatic hydrocarbon fraction it has been found that H 2 S concentration in reaction mixture is the main factor influencing process selectivity. Some effect on the selectivity exerts also other process parameters and chemical composition of the catalyst - cobalt molybdenum content ratio and promoters content. Long term exploitation of the domestic CoMo-Al 2 O 3 catalyst in hydrodesulphurization process indicates its satisfied thermal stability although results in deteriorating of mechanical resistance, lowering of specific surface area, increase in mean pore radius and decrease in acidity of catalyst. In the last chapter of the monograph the results of investigations of reclamation of metal compounds (molybdic acid, aluminum hydroxide, cobalt carbonate) from the spent catalyst as well as an original technology of manufacture of the fresh one using these compounds have been presented. (author). 338 refs, 31 figs, 32 tabs

FY 1990 Study Meeting of Catalyst (Iron system). Data; 1990 nendo shokubai kento kai (Tetsu kei) shiryo

Energy Technology Data Exchange (ETDEWEB)

NONE

1991-03-01

The FY 1990 Study Meeting of Iron-system Catalyst was held at NEDO on March 12, 1991, and the data were arranged. In the study meeting, papers titled as follows were made public: About the behavior of H{sub 2}S on iron-system catalyst by Muroran Institute of Technology; Results of the test on iron-system catalyst in the BCL project by Research Institute, Mitsubishi Kasei Corp.; Results of the test on iron-system catalyst by 2.4 t/d PDU by NKK; Results of the test on iron-system catalyst by 0.1 t/d BSU by Mitsui Engineering and Shipbuilding Co.; Results of the test on iron-system catalyst by 1 t/d PSU by Nippon Steel Corp.; Results of the research at Government Industrial Development Laboratory, Hokkaido, and the study; Results of the research at National Chemical Laboratory for Industry and the study; Results of the research at the University of Tokyo and the study; Details of the development of synthetic iron sulfide and the attainment up to now by Asahi Chemical Industry Co. Moreover, the plenary session was held on research items for the development of iron-system catalyst in future. (NEDO)

Sorption of molybdenum by cellulose polyphosphate from acid solutions

International Nuclear Information System (INIS)

Luneva, N.K.; Oputina, A.G.; Ermolenko, I.N.

1985-01-01

The sorption of molybdenum on cellulose polyphosphate from acid solutions of ammonium molybdate depending on the phosphorus content in samples, concentration and pH of the solution, sorption time is studied. It is shown that a maximum molybdenum content on the cellulose samples with different phosphorus content is pointed out at an ammonium molybdate concentration 0.02 M. Saturation of the sorption curve is attained at molar ratio of adsrbed molybdenum to phosphorus 1:4. In case of small fillings the compound with molybdenum to phosphorus ratio 1:10 is formed

On possibility of preparation of catalysts for ammonia synthesis based on cyanocomplexes of some d-metals

International Nuclear Information System (INIS)

Sergeeva, A.N.; Dovgej, V.V.; Pavlenko, L.I.; Zubritskaya, D.I.; Tkachenko, Zh.I.; Okorskaya, A.P.; Lyubchenko, Yu.A.

1983-01-01

The catalytic properties of the systems prepared on the basis of coordination cyanides of iron, ruthenium, osmium, rhenium, molydenum, vanadium and other d-metals in the ammonia synthesis reaction are studied. It has been found that thermal stability of catalytic systems containing vanadium and molybdenum is considerably higher than that of the industrial sample of similar type containing aluminium. The systems prepared on the basis of hexacyanoferrates, ruthenates and osmates can be referred to low-temperature type catalysts

Deformation localization and cyclic strength in polycrystalline molybdenum

Energy Technology Data Exchange (ETDEWEB)

Sidorov, O.T.; Rakshin, A.F.; Fenyuk, M.I.

1983-06-01

Conditions of deformation localization and its interrelation with cyclic strength in polycrystalline molybdenum were investigated. A fatigue failure of polycrystalline molybdenum after rolling and in an embrittled state reached by recrystallization annealing under cyclic bending at room temperature takes place under nonuniform distribution of microplastic strain resulting in a temperature rise in separate sections of more than 314 K. More intensive structural changes take place in molybdenum after rolling than in recrystallized state.

Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

Science.gov (United States)

Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

1998-01-01

Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

Purification of hydrogen sulfide

International Nuclear Information System (INIS)

Tsao, U.

1978-01-01

A process is described for purifying a hydrogen sulfide gas stream containing carbon dioxide, comprising (a) passing the gas stream through a bed of solid hydrated lime to form calcium hydrosulfide and calcium carbonate and (b) regenerating hydrogen sulfide from said calcium hydrosulfide by reacting the calcium hydrosulfide with additional carbon dioxide. The process is especially applicable for use in a heavy water recovery process wherein deuterium is concentrated from a feed water containing carbon dioxide by absorption and stripping using hydrogen sulfide as a circulating medium, and the hydrogen sulfide absorbs a small quantity of carbon dioxide along with deuterium in each circulation

Bioleaching of spent hydro-processing catalyst using acidophilic bacteria and its kinetics aspect

International Nuclear Information System (INIS)

Mishra, Debaraj; Kim, Dong J.; Ralph, David E.; Ahn, Jong G.; Rhee, Young H.

2008-01-01

Bioleaching of metals from hazardous spent hydro-processing catalysts was attempted in the second stage after growing the bacteria with sulfur in the first stage. The first stage involved transformation of elemental sulfur particles to sulfuric acid through an oxidation process by acidophilic bacteria. In the second stage, the acidic medium was utilized for the leaching process. Nickel, vanadium and molybdenum contained within spent catalyst were leached from the solid materials to liquid medium by the action of sulfuric acid that was produced by acidophilic leaching bacteria. Experiments were conducted varying the reaction time, amount of spent catalysts, amount of elemental sulfur and temperature. At 50 g/L spent catalyst concentration and 20 g/L elemental sulfur, 88.3% Ni, 46.3% Mo, and 94.8% V were recovered after 7 days. Chemical leaching with commercial sulfuric acid of the similar amount that produced by bacteria was compared. Thermodynamic parameters were calculated and the nature of reaction was found to be exothermic. Leaching kinetics of the metals was represented by different reaction kinetic equations, however, only diffusion controlled model showed the best correlation here. During the whole process Mo showed low dissolution because of substantiate precipitation with leach residues as MoO 3 . Bioleach residues were characterized by EDX and XRD

Bioleaching of spent hydro-processing catalyst using acidophilic bacteria and its kinetics aspect

Energy Technology Data Exchange (ETDEWEB)

Mishra, Debaraj [Mineral and Material Processing Division, Korea Institute of Geosciences and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Department of Microbiology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Kim, Dong J. [Mineral and Material Processing Division, Korea Institute of Geosciences and Mineral Resources, Daejeon 305-350 (Korea, Republic of)], E-mail: djkim@kigam.re.kr; Ralph, David E. [AJ Parker CRC for Hydrometallurgy, Murdoch University, South Street Murdoch, Perth 6153 (Australia); Ahn, Jong G. [Mineral and Material Processing Division, Korea Institute of Geosciences and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Rhee, Young H. [Department of Microbiology, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2008-04-15

Bioleaching of metals from hazardous spent hydro-processing catalysts was attempted in the second stage after growing the bacteria with sulfur in the first stage. The first stage involved transformation of elemental sulfur particles to sulfuric acid through an oxidation process by acidophilic bacteria. In the second stage, the acidic medium was utilized for the leaching process. Nickel, vanadium and molybdenum contained within spent catalyst were leached from the solid materials to liquid medium by the action of sulfuric acid that was produced by acidophilic leaching bacteria. Experiments were conducted varying the reaction time, amount of spent catalysts, amount of elemental sulfur and temperature. At 50 g/L spent catalyst concentration and 20 g/L elemental sulfur, 88.3% Ni, 46.3% Mo, and 94.8% V were recovered after 7 days. Chemical leaching with commercial sulfuric acid of the similar amount that produced by bacteria was compared. Thermodynamic parameters were calculated and the nature of reaction was found to be exothermic. Leaching kinetics of the metals was represented by different reaction kinetic equations, however, only diffusion controlled model showed the best correlation here. During the whole process Mo showed low dissolution because of substantiate precipitation with leach residues as MoO{sub 3}. Bioleach residues were characterized by EDX and XRD.

Sulfide oxidation in a biofilter

DEFF Research Database (Denmark)

Pedersen, Claus Lunde; Dezhao, Liu; Hansen, Michael Jørgen

Observed hydrogen sulfide uptake rates in a biofilter treating waste air from a pig farm were too high to be explained within conventional limits of sulfide solubility, diffusion in a biofilm and bacterial metabolism. Clone libraries of 16S and 18S rRNA genes from the biofilter found no sulfide...... higher hydrogen sulfide uptake followed by oxidation catalyzed by iron-containing enzymes such as cytochrome c oxidase in a process uncoupled from energy conservation....

Sulfide oxidation in a biofilter

DEFF Research Database (Denmark)

Pedersen, Claus Lunde; Liu, Dezhao; Hansen, Michael Jørgen

2012-01-01

Observed hydrogen sulfide uptake rates in a biofilter treating waste air from a pig farm were too high to be explained within conventional limits of sulfide solubility, diffusion in a biofilm and bacterial metabolism. Clone libraries of 16S and 18S rRNA genes from the biofilter found no sulfide...... higher hydrogen sulfide uptake followed by oxidation catalyzed by iron-containing enzymes such as cytochrome c oxidase in a process uncoupled from energy conservation....

Tungsten-Based Mesoporous Silicates W-MMM-E as Heterogeneous Catalysts for Liquid-Phase Oxidations with Aqueous H2O2

Directory of Open Access Journals (Sweden)

Nataliya Maksimchuk

2018-02-01

Full Text Available Mesoporous tungsten-silicates, W-MMM-E, have been prepared following evaporation-induced self-assembly methodology and characterized by elemental analysis, XRD, N2 adsorption, STEM-HAADF (high angle annular dark field in scanning-TEM mode, DRS UV-vis, and Raman techniques. DRS UV-vis showed the presence of two types of tungsten oxo-species in W-MMM-E samples: isolated tetrahedrally and oligomeric octahedrally coordinated ones, with the ratio depending on the content of tungsten in the catalyst. Materials with lower W loading have a higher contribution from isolated species, regardless of the preparation method. W-MMM-E catalyzes selectively oxidize of a range of alkenes and organic sulfides, including bulky terpene or thianthrene molecules, using green aqueous H2O2. The selectivity of corresponding epoxides reached 85–99% in up to 80% alkene conversions, while sulfoxides formed with 84–90% selectivity in almost complete sulfide conversions and a 90–100% H2O2 utilization efficiency. The true heterogeneity of catalysis over W-MMM-E was proved by hot filtration tests. Leaching of inactive W species depended on the reaction conditions and initial W loading in the catalyst. After optimization of the catalyst system, it did not exceed 20 ppm and 3 ppm for epoxidation and sulfoxidation reactions, respectively. Elaborated catalysts could be easily retrieved by filtration and reused several times with maintenance of the catalytic behavior.

Bibliographic study on molybdenum biokinetics. Literaturstudie zur Biokinetik von Molybdaen

Energy Technology Data Exchange (ETDEWEB)

Erzberger, A.

1988-05-01

This bibliographical study compiles and analyzes findings about the metabolism and resorption of molybdenum. Besides including studies on the physiology of molybdenum 99, a general survey is given on molybdenum in the environment and on its physiological behaviour. In particular, information on the dependence of molybdenum resorption on various factors, such as the chemical form, antagonisms etc., are gathered from literature. These factors have to be considered for sensibly carrying out necessary experiments.

Synthesis and characterization of new magnetically recoverable molybdenum nanocatalyst for epoxidation of olefins

Energy Technology Data Exchange (ETDEWEB)

Masteri-Farahani, M., E-mail: mfarahany@yahoo.com [Faculty of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of); Kashef, Z. [Faculty of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of)

2012-04-15

New heterogeneous molybdenum catalyst was prepared through covalent attachment of a Schiff base ligand on the surface of silica coated magnetite nanoparticles via aminopropyl spacer and subsequent complexation with MoO{sub 2}(acac){sub 2}. The prepared nanocatalyst was characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies and vibrating sample magnetometry. Catalytic epoxidation of some olefins and allylic alcohols by prepared nanocatalyst using tert-butyl hydroperoxide and cumene hydroperoxide as oxidants was achieved with good activities and selectivities. - Highlights: Black-Right-Pointing-Pointer Silica coated magnetite nanoparticles were modified with a Schiff base ligand. Black-Right-Pointing-Pointer Next reaction with MoO{sub 2}(acac){sub 2} afforded magnetically recoverable nanocatalyst. Black-Right-Pointing-Pointer The prepared nanocatalyst catalyzed the epoxidation of olefins with TBHP.

Thermal cyclic strength of molybdenum monocrystal at high temperatures

International Nuclear Information System (INIS)

Strizhalo, V.A.; Uskov, E.I.

1975-01-01

The results of the investigation of the thermocyclic creep and low-cycle fatigue of a molybdenum single crystal are discussed. The strength of a molybdenum single crystal under nonisothermal stressing has been investigated by using two different regimes of temperature and load variation. The temperature limits of the cycle were the same for the two testing regimes, the maximum temperature being 1700degC and the minimum 350degC. At higher temperatures (above 1500degC) the short-term strength of single-crystal molybdenum is comparable with that of commercial molybdenum and the refractory alloys, while the ductility is considerably higher. It should be noted that the failure of single-crystal molybdenum under rigid alternating loading is preceded by intensive distortion of the specimen, owing to directional cyclic creep of the metal in zones of bulging and thinning

Exploring atomic defects in molybdenum disulphide monolayers

KAUST Repository

Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

2015-01-01

Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm '2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

Exploring atomic defects in molybdenum disulphide monolayers

KAUST Repository

Hong, Jinhua

2015-02-19

Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

Molybdenum silicide based materials and their properties

International Nuclear Information System (INIS)

Yao, Z.; Stiglich, J.; Sudarshan, T.S.

1999-01-01

Molybdenum disilicide (MoSi 2 ) is a promising candidate material for high temperature structural applications. It is a high melting point (2030 C) material with excellent oxidation resistance and a moderate density (6.24 g/cm 3 ). However, low toughness at low temperatures and high creep rates at elevated temperatures have hindered its commercialization in structural applications. Much effort has been invested in MoSi 2 composites as alternatives to pure molybdenum disilicide for oxidizing and aggressive environments. Molybdenum disilicide-based heating elements have been used extensively in high-temperature furnaces. The low electrical resistance of silicides in combination with high thermal stability, electron-migration resistance, and excellent diffusion-barrier characteristics is important for microelectronic applications. Projected applications of MoSi 2 -based materials include turbine airfoils, combustion chamber components in oxidizing environments, missile nozzles, molten metal lances, industrial gas burners, diesel engine glow plugs, and materials for glass processing. On this paper, synthesis, fabrication, and properties of the monolithic and composite molybdenum silicides are reviewed

Crystalline structure and propylene oxidation in complex bismuth-molybdenum oxide catalysts

International Nuclear Information System (INIS)

Manaila, R.; Ionescu, N.I.; Caldararu, M.

1980-01-01

Complex Bi-Mo oxide catalysts supported on amorphous SiO 2 were prepared by coprecipitation and tested in the reaction of selective oxidation of propylene to acrolein. They consist of a mixture of molybdate phases and excess MoO 3 . The Fe 2 (MoO 4 ) 3 phase was found to have a high concentration of lattice defects, induced by a Mo excess. These defects could be related to the catalytic conversion and to the selectivity to total oxidation by varying the calcination temperature. Calcination above 500 0 C induced also the transition of the metastable modification β-NiMoO 4 to the stable form α, accompanied by a loss of conversion. A complex Bi molybdate with scheelitic structure was found to have a high selectivity to acrolein. (author)

Mixed alcohols production from syngas

International Nuclear Information System (INIS)

Stevens, R.R.; Conway, M.M.

1988-01-01

A process is described for selectively producing mixed alcohols from synthesis gas comprising contacting a mixture of hydrogen and carbon monoxide with a catalytic amount of a catalyst containing components of (1) a catalytically active metal of molybdenum or tungsten, in free or combined form; (2) a cocatalytic metal or cobalt or nickel in free or combined form; and (3) a Fischer-Tropsch promoter of an alkali or alkaline earth series metal, in free or combined form; the components combined by dry mixing, mixing as a wet paste, wet impregnation, and then sulfided, the catalyst excluding rhodium, ruthenium and copper, at a pressure of at least about 500 psig and under conditions sufficient to form the mixed alcohols in at least 20 percent CO/sub 2/ free carbon selectivity, the mixed alcohols containing a C/sub 1/ to C/sub 2-5/ alcohol weight ratio of less than about 1:1

Molybdenum: the element and aqueous solution chemistry

International Nuclear Information System (INIS)

Sykes, A.G.

1987-01-01

This chapter on the chemistry of the coordination compounds of molybdenum concentrates on the element itself, its recovery from ores and its use in the manufacture of steels. Most of the chapter is devoted to the aqueous solution chemistry of molybdenum in oxidation states II, III and IV. (UK)

Low-temperature heat capacity of molybdenum borides

International Nuclear Information System (INIS)

Bolgar, A.S.; Klinder, A.V.; Novoseletskaya, L.M.; Turov, V.P.; Klochkov, L.A.; Lyashchenko, A.B.

1988-01-01

Heat capacity of molybdenum borides Mo 2 B, MoB, Mo 2 B 5 is studied for the first time in the 60-300 K range using the adiabatic method. Standard (at 298.15 K) thermodynamic functions (enthalpy, heat capacity, entropy, reduced Gibbs energy) of molybdenum borides are calculated

XUV spectra of highly ionised molybdenum

Energy Technology Data Exchange (ETDEWEB)

Mansfield, M W.D.; Peacock, N J; Smith, C C; Hobby, M G [UKAEA, Abingdon. Culham Lab.; Cowan, R D

1978-05-14

The spectra of molybdenum ions produced in Tokamaks in the wavelength range 10-200 A have been reproduced in a plasma formed by laser beam irradiation of solid molybdenum targets. Lines from highly ionised stages of molybdenum (Mo XXX to Mo XXXII) have been distinguished by varying the laser beam intensity. Detailed analyses of the simpler ions, Mo XV (Ni-like), Mo XVI (Co-like), Mo XXXII (Na-like), and to a lesser extent Mo XXXI (Mg-like) and Mo XVII (Fe-like), have been achieved by comparison with ab initio calculations. A general interpretation of intermediate ion stages is also given but it is shown that most of these spectra are so complex, as a result of inner-subshell excitation, that detailed term-scheme analyses are nearly impossible.

Elaboration, physical and electrochemical characterizations of CO tolerant PEMFC anode materials. Study of platinum-molybdenum and platinum-tungsten alloys and composites; Elaborations et caracterisations electrochimiques et physiques de materiaux d'anode de PEMFC peu sensibles a l'empoisonnement par CO: etude d'alliages et de composites a base de platine-molybdene et de platine-tungstene

Energy Technology Data Exchange (ETDEWEB)

Peyrelade, E.

2005-06-15

PEMFC development is hindered by the CO poisoning ability of the anode platinum catalyst. It has been previously shown that the oxidation potential of carbon monoxide adsorbed on the platinum atoms can be lowered using specific Pt based catalysts, either metallic alloys or composites. The objective is then to realize a catalyst for which the CO oxidation is compatible with the working potential of a PEMFC anode. In our approach, to enhance the CO tolerance of platinum based catalyst supported on carbon, we studied platinum-tungsten and platinum-molybdenum alloys and platinum-metal oxide materials (Pt-WO{sub x} and Pt-MoO{sub x}). The platinum based alloys demonstrate a small effect of the second metal towards the oxidation of carbon monoxide. The platinum composites show a better tolerance to carbon monoxide. Electrochemical studies on both Pt-MoO{sub x} and Pt-WO{sub x} demonstrate the ability of the metal-oxides to promote the ability of Pt to oxidize CO at low potentials. However, chrono-amperometric tests reveal a bigger influence of the tungsten oxide. Complex chemistry reactions on the molybdenum oxide surface make it more difficult to observe. (author)

Microwave-Assisted Synthesis of Nanoporous Aluminum-Based Coordination Polymers as Catalysts for Selective Sulfoxidation Reaction

Directory of Open Access Journals (Sweden)

Madhan Vinu

2017-10-01

Full Text Available A series of aluminum-based coordination polymers or metal–organic frameworks (Al–MOFs, i.e., DUT-4, DUT-5, MIL-53, NH2-MIL-53, and MIL-100, have been facile prepared by microwave (MW-assisted reactions and used as catalysts for selective sulfoxidation reactions. The MW-assisted synthesis drastically reduced the reaction time from few days to hours. The prepared MOFs have smaller and uniform particle sizes and better yield compared to conventional hydrothermal method. Furthermore, the Al–MOFs have been successfully demonstrated as catalysts in oxidation reaction of methyl phenyl sulfide with H2O2 as oxidant, even under mild conditions, with more than 95% conversion.

Synthesis and essay of an Ionomer like catalyst of olefins epoxidation

International Nuclear Information System (INIS)

Boyaca Mendivelso, Alejandro; Tempesti, Ezio

1995-01-01

The purpose of the present work is the preparation of an ionomer with base in Molybdenum and to evaluate its activity like catalyst of olefins epoxidation like alternative of synthesis of catalysts of the Hawk process. A polymer is synthesized with available functional groups to stabilize the metal starting from sodium molybdate; the characterization is made by atomic absorption, spectroscopy to GO, and X.P.S. The characterization indicates that indeed it is possible to stabilize the Mo in the main polymeric. The evaluation in reaction in liquid phase allows similar conversions to those of a homogeneous catalyst. The selective epoxidation of olefins for alkyl hydroperoxides, it has acquired great importance inside the industrial processes obtaining of propylene oxide due to the recent use of the terbutilic alcohol (co-produced together with the epoxide), as preservative in gasoline free of lead. In the environment of these processes, and in particular in the Hawk process possibilities of technological innovation, in the concerning to the heterogenization of conventional catalysts, at the moment used in homogeneous phase. The present work collaborate to some tentative that look for to generate alternative of preparation of catalysts for the process Hawk, synthesizing and testing the activity of an ionomer like epoxidation catalyst, which tries to reproduce the chemical structure of the complexes organ-metallic pear to suppress the separation stages and necessary recovery facilitating its recurrent reutilization with eventual economic repercussions in the industrial process. It is described the procedure of synthesis of the ionomer, the characterization and the evaluation of the activity in reaction under diverse conditions. Of the made characterization it comes off that the heterogenization of catalysts for olefins epoxidation, according to the Hawk process, is possible by means of the preparation of polymers modified appropriately. Likewise the evaluation in

Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al{sub 2}O{sub 3} catalysts. Langmuir-Hinshelwood kinetic modelling

Energy Technology Data Exchange (ETDEWEB)

Monteiro-Gezork, Ana Cristina Alves; Winterbottom, John Mike [Department of Chemical Engineering, School of Engineering, The University of Birmingham, Birmingham B15 2TT (United Kingdom); Natividad, Reyna [Department of Chemical Engineering, Faculty of Chemistry, Universidad Autonoma del Estado de Mexico, Paseo Colon Esq. Tollocan, Toluca, Edo. de Mexico, Mexico CP 50120 (Mexico)

2008-01-30

The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al{sub 2}O{sub 3}) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir-Hinshelwood (L-H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al{sub 2}O{sub 3} catalysts) on the initial reaction rate. The L-H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al{sub 2}O{sub 3} catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al{sub 2}O{sub 3} or the presulphided NiMo/Al{sub 2}O{sub 3} catalyst. (author)

Low temperature incineration of mixed wastes using bulk metal oxide catalysts

International Nuclear Information System (INIS)

Gordon, M.J.; Gaur, S.; Kelkar, S.; Baldwin, R.M.

1996-01-01

Volume reduction of low-level mixed wastes from former nuclear weapons facilities is a significant environmental problem. Processing of these materials presents unique scientific and engineering problems due to the presence of minute quantities of radionuclides which must be contained and concentrated for later safe disposal. Low-temperature catalytic incineration is one option that has been utilized at the Rocky Flats facility for this purpose. This paper presents results of research regarding evaluation of bulk metal oxides as catalysts for low-temperature incineration of carbonaceous residues which are typical by-products of fluidized bed combustion of mixed wastes under oxygen-lean conditions. A series of 14 metal oxides were screened in a thermogravimetric analyzer, using on-line mass spectrometry for speciation of reaction product gases. Catalyst evaluation criteria focused on the thermal-redox activity of the metals using both carbon black and PVC char as surrogate waste materials. Results indicated that metal oxides which were P-type semiconductor materials were suitable as catalysts for this application. Oxides of cobalt, molybdenum, vanadium, and manganese were found to be particularly stable and active catalysts under conditions specific to this process (T<650C, low oxygen partial pressures). Bench-scale evaluation of these metal oxides with respect to stability to chlorine (HCl) attack was carried out at 550C using a TG/MS system. Cobalt oxide was found to be resistant to metal loss in a HCl/He gaseous environment while metal loss from Mo, Mn, and V-based catalysts was moderate to severe. XRD and SEM/EDX analysis of spent Co catalysts indicated the formation of non-stoichiometric cobalt chlorides. Regeneration of chlorinated cobalt was found to successfully restore the low-temperature combustion activity to that of the fresh metal oxide

Separation of uranium from molybdenum by alkyl phosphoric acid extraction

Energy Technology Data Exchange (ETDEWEB)

Zhongshi, Li

1986-08-01

The regularities of separation of uranium from molybdenum by alkyl phosphoric acid extraction are described. Two parameters, i.e., density ratio of uranium to molybdenum in organic phase at first stage and density of uranium in raffinate at last stage are presented. The relationship between these parameters and purity of molybdenum and uranium products is given. The method of adjusting and controlling these parameters in experiments and production is worked out. The technical key problem in comprehensive utilization of sedimentary type uranium ore containing molybdenum with close concentration of these to elements has been solved.

Alkaline elution of uranium and molybdenum and their recovery

International Nuclear Information System (INIS)

Song Wenlan; Wu Peisheng; Zhao Pinzhi; Tao Dening; Xie Chaoyan

1987-01-01

The uranium and molybdenum can be simultaneously eluted by using eluant (NH 4 ) 2 CO 3 + (NH 4 ) 2 SO 4 from resin loaded uranium and molybdenum. The ADU is precipitated from eluant by volatilization of ammonia. The molybdenum is extracted by TFA-TBP-kerosene from the filtrate at pH 3.0-3.2 with molybdenum extraction > 98%. Uranium is nearly not extracted. The precipitation of Mo is reached by sulphuric acid after stripping and the ammonium multimolybdate is obtained. This process can give the total recovery more than 99% for U and 90% for Mo. Because of the use of sulphate salt system, the hazard of NO 3 - can be avoided

Quantitative Surface Analysis by Xps (X-Ray Photoelectron Spectroscopy: Application to Hydrotreating Catalysts

Directory of Open Access Journals (Sweden)

Beccat P.

1999-07-01

Full Text Available XPS is an ideal technique to provide the chemical composition of the extreme surface of solid materials, vastly applied to the study of catalysts. In this article, we will show that a quantitative approach, based upon fundamental expression of the XPS signal, has enabled us to obtain a consistent set of response factors for the elements of the periodic table. In-depth spadework has been necessary to know precisely the transmission function of the spectrometer used at IFP. The set of response factors obtained enables to perform, on a routine basis, a quantitative analysis with approximately 20% relative accuracy, which is quite acceptable for an analysis of such a nature. While using this quantitative approach, we have developed an analytical method specific to hydrotreating catalysts that allows obtaining the sulphiding degree of molybdenum quite reliably and reproducibly. The usage of this method is illustrated by two examples for which XPS spectroscopy has provided with information sufficiently accurate and quantitative to help understand the reactivity differences between certain MoS2/Al2O3 or NiMoS/Al2O3-type hydrotreating catalysts.

Molybdenum erosion measurements in Alcator C-Mod

Energy Technology Data Exchange (ETDEWEB)

Wampler, W.R. [Sandia National Labs., Albuquerque, NM (United States); LaBombard, B.; Lipshultz, B.; Pappas, D.; Pitcher, C.S. [Massachusetts Inst. of Tech., Cambridge, MA (United States); McCracken, G.M. [JET Joint Undertaking, Abingdon (United Kingdom)

1998-05-01

Erosion of molybdenum was measured on a set of 21 tiles after a run campaign of 1,090 shots in the Alcator C-Mod tokamak. The net erosion of molybdenum, was determined from changes in the depth of a thin chromium marker layer measured by Rutherford backscattering. Net Mo erosion was found to be approximately 150 nm near the outer divertor strike point, and much less everywhere else. Gross erosion rates by sputtering were estimated using ion energies and fluxes obtained from Langmuir probe measurements of edge-plasma conditions. Predicted net erosion using calculated gross erosion with prompt redeposition and measured net erosion agree within a factor of 3. Sputtering by boron and molybdenum impurities dominates erosion.

Selective hydrodeoxygenation of biomass-derived oxygenates to unsaturated hydrocarbons using molybdenum carbide catalysts.

Science.gov (United States)

Ren, Hui; Yu, Weiting; Salciccioli, Michael; Chen, Ying; Huang, Yulin; Xiong, Ke; Vlachos, Dionisios G; Chen, Jingguang G

2013-05-01

Which cleavage do you prefer? With a combination of density functional theory (DFT) calculations, surface science studies, and reactor evaluations, Mo(2)C is identified as a highly selective HDO catalyst to selectively convert biomass-derived oxygenates to unsaturated hydrocarbons through selective C-O bond scissions without C-C bond cleavage. This provides high-value HDO products for utilization as feedstocks for chemicals and fuels; this also reduces the overall consumption of H2 . Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microbial control of hydrogen sulfide production

Energy Technology Data Exchange (ETDEWEB)

Montgomery, A.D.; Bhupathiraju, V.K.; Wofford, N.; McInerney, M.J. [Univ. of Oklahoma, Tulsa, OK (United States)] [and others

1995-12-31

A sulfide-resistant strain of Thiobacillus denitrificans, strain F, prevented the accumulation of sulfide by Desulfovibrio desulfuricans when both organisms were grown in liquid medium. The wild-type strain of T. denitrificans did not prevent the accumulation of sulfide produced by D. desulfuricans. Strain F also prevented the accumulation of sulfide by a mixed population of sulfate-reducing bacteria enriched from an oil field brine. Fermentation balances showed that strain F stoichiometrically oxidized the sulfide produced by D. desulfuricans and the oil field brine enrichment to sulfate. The ability of a strain F to control sulfide production in an experimental system of cores and formation water from the Redfield, Iowa, natural gas storage facility was also investigated. A stable, sulfide-producing biofilm was established in two separate core systems, one of which was inoculated with strain F while the other core system (control) was treated in an identical manner, but was not inoculated with strain F. When formation water with 10 mM acetate and 5 mM nitrate was injected into both core systems, the effluent sulfide concentrations in the control core system ranged from 200 to 460 {mu}M. In the test core system inoculated with strain F, the effluent sulfide concentrations were lower, ranging from 70 to 110 {mu}M. In order to determine whether strain F could control sulfide production under optimal conditions for sulfate-reducing bacteria, the electron donor was changed to lactate and inorganic nutrients (nitrogen and phosphate sources) were added to the formation water. When nutrient-supplemented formation water with 3.1 mM lactate and 10 mM nitrate was used, the effluent sulfide concentrations of the control core system initially increased to about 3,800 {mu}M, and then decreased to about 1,100 {mu}M after 5 weeks. However, in the test core system inoculated with strain F, the effluent sulfide concentrations were much lower, 160 to 330 {mu}M.

Extraction of molybdenum VI by alpha benzoinoxime

International Nuclear Information System (INIS)

Achache, M.; Meklati, M.

1990-06-01

The concentration of molybdenum, was studied using alpha benzoinoxime dissolved in chloroform. Several acids and salt at different levels of concentration were investigated as well as other parameters such as (mixing time, extractant to metal ratio, temperature etc.) The molybdenum stippling was also studied in alkaline medium with the subsequent recovery of the extractant and solvent

Synthesis of molybdenum borides and molybdenum silicides in molten salts and their oxidation behavior in an air-water mixture

NARCIS (Netherlands)

Kuznetsov, S.A.; Kuznetsova, S.V.; Rebrov, E.V.; Mies, M.J.M.; Croon, de M.H.J.M.; Schouten, J.C.

2005-01-01

The formation of various coatings in molybdenum-boron and molybdenum-silicon systems was investigated. Boronizing and siliciding treatments were conducted in molten salts under inert gas atm. in the 850-1050 DegC temp. range for 7 h. The presence of boride (e.g. Mo2B, MoB, Mo2B5) and silicide

Process for recovering tungsten from alkaline leaching solution of tungsten ores

International Nuclear Information System (INIS)

Onozaki, S.; Nemoto, S.; Hazeyama, T.

1976-01-01

This invention relates to a process for recovering tungsten from an alkaline leaching solution of tungsten ores. This invention comprises adjusting the pH of an alkaline leaching solution which is obtained by lixiviating ore containing tungsten with an alkaline solution to 7--8 with acid to oxidize molybdic acid ions in the solution, adding a sulfide donor, then precipitating molybdenum sulfide compounds by adjusting the pH value of the solution to 2--3. Tungstic acid ions are recovered as calcium tungstate by the addition of a calcium ion donor after the molybdenum sulfide compounds are separated

Weldability of powder-metallurgy molybdenum with low oxygen content

International Nuclear Information System (INIS)

Hiraoka, Yutaka; Okada, Masatoshi

1987-01-01

Relationships between the formation of weld pores and the chemical compositions in powder-metallurgy molybdenum were investigated. It is suggested that almost 100% of Ca and Mg form oxides. In contrast, Fe, Ni, Cr and Al, Si only partly form oxides. A powder-metallurgy molybdenum containing less than 84 at.ppm oxygen did not show any large weld pores. The reduction of the oxygen content was achieved by purifying the molybdenum powder. (orig.) [de

Hydrotreatment of bio-oil over Ni-based catalyst.

Science.gov (United States)

Zhang, Xinghua; Wang, Tiejun; Ma, Longlong; Zhang, Qi; Jiang, Ting

2013-01-01

Inexpensive non-sulfided Ni-based catalysts were evaluated for hydrotreatments using phenol as model compound. HZSM-5, a zeolite with different ratio of Si/Al and γ-Al(2)O(3) were impregnated with Ni(NO(3))(2) · 6H(2)O and calcined at 450 °C. Conversion rates and product distribution for treatment of phenol at 160-240 °C in the presence of catalysts with nickel loads of 6, 10, 14 and 17 wt.% were determined. Phenol conversion was highest (91.8%) at 240 °C in the presence of HZSM-5(Si/Al = 38) loaded with 10% Ni. When hydrotreatment was carried out with bio-oil obtained from pyrolysis of pine sawdust under the optimal conditions determined for phenol, the pH of bio-oil increased from 2.27 to 4.07, and the hydrogen content increased from 6.28 to 7.01 wt.%. The decrease in acidity is desirable for the use of upgraded bio-oil. Copyright © 2012. Published by Elsevier Ltd.

Separation and selective determination of molybdenum with sodiumthiosulfate and ethylacetate

International Nuclear Information System (INIS)

Hainberger, L.; de Oliveira Andrade, W.

1982-01-01

A sensitive and selective method of spectrophotometric determination of molybdenum is described. Molybdenum is extracted to more than 97%. Lambert-Beer's law is obeyed between 0.35 and 30μg/10ml of the used aqueous solution. 43 ions concerning their interference are studied. The method was used to determine the content of molybdenum in black beans. (Author)

Friction and corrosion resistance of sputter deposited supersaturated metastable aluminium-molybdenum alloys

Energy Technology Data Exchange (ETDEWEB)

Abu-Zeid, O.A. [Univ. of the United Arab Emirates, Al-Ain (United Arab Emirates). Dept. of Mech. Eng.; Bates, R.I. [Design, Mfg. and Marketing Research Inst., Univ. of Salford (United Kingdom)

1996-12-15

Two closed field unbalanced magnetrons with targets of aluminium and molybdenum have been used for the co-deposition of aluminium-molybdenum coatings with different compositions. A pin on disk machine and a computer controlled potentiostat have been used to evaluate respectively, the tribological and corrosion properties of the deposited alloys. Results have shown that introducing molybdenum into aluminium coatings improves their poor tribological properties. Aluminium-molybdenum coatings with different compositions have shown low wear behaviour and for coatings with high molybdenum contents (> 80%) friction coefficients against steel, as low as 0.18 have been obtained. The addition of molybdenum into aluminium coatings has reduced their corrosion tendency and corrosion current density in a marine environment. (orig.)

Mesostructured metal germanium sulfides

Energy Technology Data Exchange (ETDEWEB)

MacLachlan, M.J.; Coombs, N.; Bedard, R.L.; White, S.; Thompson, L.K.; Ozin, G.A.

1999-12-29

A new class of mesostructured metal germanium sulfide materials has been prepared and characterized. The synthesis, via supramolecular assembly of well-defined germanium sulfide anionic cluster precursors and transition-metal cations in formamide, represents a new strategy for the formation of this class of solids. A variety of techniques were employed to examine the structure and composition of the materials. Structurally, the material is best described as a periodic mesostructured metal sulfide-based coordination framework akin to periodic hexagonal mesoporous silica, MCM-41. At the molecular scale, the materials strongly resemble microstructured metal germanium sulfides, in which the structure of the [Ge{sub 4}S{sub 10}]{sup 4{minus}} cluster building-blocks are intact and linked via {mu}-S-M-S bonds. Evidence for a metal-metal bond in mesostructured Cu/Ge{sub 4}S{sub 10} is also provided.

Epoxidation of cyclohexene by ethyl-benzene hydroperoxide in the presence of molybdenum catalyst

International Nuclear Information System (INIS)

Sapunov, V.N.; Litvintsev, I.Yu.; Margitfal'vi, J.; Lebedev, N.N.

1977-01-01

A study has been made of the kinetic experimental pattern and mechanism of epoxidation of cyclohexene by ethylbenzene hydroperoxide during catalysis by Mo(CO) 6 in various solvents. A first order of reaction with respect to the catalyst and complex order of reaction with respect to the hydroperoxide and olefine have been established. Simple (square and cross) inhibition by reaction products, cyclohexene oxide and methylphenylcarbinol, have been found. An increase in the dielectric constant of the solvent diminishes the epoxidation rate. The mechanism scheme of the process is proposed and main kinetic parameters calculated

Molybdenum plasma spray powder, process for producing said powder, and coating made therefrom

International Nuclear Information System (INIS)

Lafferty, W.D.; Cheney, R.F.; Pierce, R.H.

1979-01-01

Plasma spray powders of molybdenum particles containing 0.5 to 15 weight percent oxygen and obtained by reacting molybdenum particles with oxygen or oxides in a plasma, form plasma spray coatings exhibiting hardness comparable to flame sprayed coatings formed from molybdenum wire and plasma coatings of molybdenum powders. Such oxygen rich molybdenum powders may be used to form wear resistant coatings, such as for piston rings. (author)

Solid solutions of hydrogen in niobium, molybdenum and their alloys

International Nuclear Information System (INIS)

Ishikawa, T.T.

1981-01-01

The solubility of hydrogen in niobium, molybdenum and niobium-molybdenum alloys with varying atomic fraction of molybdenum from 0.15 to 0.75 was measured on the temperature range of 673 0 K to 1273 0 k for one atmosphere hydrogen pressure. The experimental technique involved the saturation of the solvent metal or alloy with hydrogen, followed by quenching and analysis of the solid solution. The results obtained of hydrogen solubility are consistent with the quasi-regular model for the dilute interstitial solid solutions. The partial molar enthalpy and partial molar entropy in excess of the dissolved hydrogen atoms were calculated from data of solubility versus reciprocal doping temperature. The variation of the relative partial molar enthalpy of hydrogen dissolved in niobium-molybdenum alloys, with the increase of molybdenum content of the alloy was analized. (Author) [pt

Potentiometric titration of molybdenum (6) with a cathode-polarized solid electrode

International Nuclear Information System (INIS)

Boeva, L.V.; Kimstach, V.A.; Bagdasarov, K.N.

1980-01-01

The possibility has been studied of using solid electrodes for potentiometric precipitation titration of molybdenum (6). A cathode-polarized electrode, electrochemically covered with a molybdenum blue layer, can be used as indicator electrode. The best results were obtained during deposition of molybdenum blue on a tungsten electrode. The mechanism of electrode work during titration has been investigated. A procedure has been developed of titration of molybdenum (6) in acid solutions using hydroxylamine N-aryl derivatives as titrants

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas; Le Qué mé ner, Fré dé ric; Bouhoute, Yassine; Szeto, Kai C.; De Mallmann, Aimery; Barman, Samir; Samantaray, Manoja; Delevoye, Laurent; Gauvin, Ré gis M.; Taoufik, Mostafa; Basset, Jean-Marie

2016-01-01

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas

2016-12-05

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

Recovery of molybdenum metal powder from a low grade molybdenite concentrate

International Nuclear Information System (INIS)

Mukherjee, T.K.; Menon, P.R.; Shukla, P.P.; Gupta, C.K.

1988-01-01

An account is given of the development of a process for the production of molybdenum metal powder from a low grade molybdenite concentrate. The molybdenum value present in the concentrate was leached with a dilute hypochlorite solution generated in-situ by electrolysis of brine solution. The leach liquor was subsequently purified by carbon adsorption process. The leach liquor was chemically processed to recover the molybdenum value in the forms of calcium molybdate and ammonium molybdate salts. These molybdenum intermediates were hydrogen-reduced to metallic molybdenum powder. The experimental set up used, procedure followed and results obtained are discussed and a flowsheet indicating the entire processing scheme is included. 11 refs., 4 figs., 8 tabs

Air oxidation of aqueous sodium sulfide solutions with coal fly ash

Energy Technology Data Exchange (ETDEWEB)

Mallik, D; Chaudhuri, S K [Southern Illinois University, Carbondale, IL (United States). Dept. of Mining Engineering

1999-02-01

The paper investigated the potential of coal fly ash as a catalyst in the air oxidation of aqueous sodium sulfide (Na{sub 2}S) solutions in the temperature range of 303-333 K. The rate of oxidation was found to be independent of the initial concentration of Na{sub 2}S in the range of 5.80 x 10{sup -2} - 28.45 x 10{sup -2} kmol/m{sup 3}. The effects of fly ash loading, source of fly ash, speed of agitation, air flow rate, fly ash particle size were also studied. Experimental results suggested a film-diffusion controlled reaction mechanism. The deactivation of the catalytic effect of fly ash was found to be less than 31% even after five repeated uses.

Microstructure and mechanical properties of multi-components rare earth oxide-doped molybdenum alloys

International Nuclear Information System (INIS)

Zhang Guojun; Sun Yuanjun; Zuo Chao; Wei Jianfeng; Sun Jun

2008-01-01

Pure molybdenum and molybdenum alloys doped with two- or three-components rare earth oxide particles were prepared by powder metallurgy. Both the tensile property and fracture toughness of the pure molybdenum and multi-components rare earth oxide-doped molybdenum alloys were determined at room temperature. The multi-components rare earth oxide-doped molybdenum alloys are fine grained and contain a homogeneous distribution of fine particles in the submicron and nanometer size ranges, which is why the molybdenum alloys have higher strength and fracture toughness than pure molybdenum. Quantitative analysis is used to explain the increase in yield strength with respect to grain size and second phase strengthening. Furthermore, the relationship between the tensile properties and microstructural parameters is quantitatively established

Preparation and characterization of nanocomposite of graphitic carbon nitride and TiO2 as a porous support for nano catalyst for desulfurization process

Directory of Open Access Journals (Sweden)

Ezzat Rafiee

2017-12-01

Full Text Available A novel heterogeneous nanocatalyst H3PW12O40/TiO2/g-C3N4 (PW/TiO2/CN was successfully synthesized by immobilization of PW on TiO2/CN nanocomposite, and characterized by SEM, BET, FT-IR, XRD, EDX, TEM and ICP. Catalytic performance of the as-prepared catalyst was investigated for the selective oxidation of sulfides to sulfoxides and sulfones in the presence of H2O2 as oxidant with good conversion and high selectivity. The main factors influencing the ability for selective oxidation of sulfides were studied, including reaction temperature, amounts of the catalyst, H2O2 and type of the reaction solvent. Catalytic oxidation of the different model oils containing dibenzothiophene (DBT, benzothiophene (BT and thiophene (T into corresponding sulfone was also studied. Effects of different extractive solvents, aromatics, alkenes and nitrogen compounds on the oxidative desulfurization processes (ODS were also studied. In addition, reducing the level of sulfur content in real oil was investigated. The recyclability of the PW/TiO2/CN nanocatalyst for various cycles without a significant loss of activity was proved. The heterogeneity of the as-prepared catalyst was confirmed by leaching tests. Keywords: Graphitic carbon nitride, Extraction, Tetrabutyl titanate, Heteropoly acid, Oxidative desulfurization, Oil

A study on direct alloying with molybdenum oxides by feed wire method

Directory of Open Access Journals (Sweden)

Jingjing Zou

2018-04-01

Full Text Available Direct alloying with molybdenum oxides has been regarded in years; the main addition methods are adding to the bottom of electric arc furnace (EAF with scrap, adding to the ladle during the converter tapping and mixing molybdenum oxide, lime and reductant to prepare pellet added to basic oxygen furnace (BOF. In this paper, a new method for direct alloying with molybdenum trioxide is proposed, adding molybdenum trioxide molten steel by feeding wire method in ladle furnace (LF refining process. The feasibility of molybdenum oxide reduction, the influence rules of bottom-blown on liquid steel fluidity and the yield of molybdenum by feeding wire method were analyzed. Results show that molybdenum oxide can be reduced by [Al], [Si], [C], and even [Fe] in molten steel. Bottom blowing position has a significant influence on the flow of molten steel when the permeable brick is located in 1/2 radius. The yields of Mo are higher than 97% for the experiments with feed wire method, the implementation of direct alloying with molybdenum trioxide by feed wire method works even better than that uses of ferromolybdenum in the traditional process.

Investigation of pressing of molybdenum powder compacts

International Nuclear Information System (INIS)

Mymrin, S.A.; Kuznetsov, V.Eh.; Yampol'skij, M.L.; Leonov, S.A.; Mikhridinov, R.M.; Korzukhin, V.A.

1990-01-01

Results of an experimental investigation into pressing of compacts of MCh type molybdenum powders using the industrial equipment are presented. To measure the density of powder molybdenum billets a radioisotopic density meter with cesium-137 is used as radioactive gamma radiation source. The dependence of the produced billet density on the specific compacting pressure at different values of the powder bulk density is ascertained

Airborne concentrations of metals and total dust during solid catalyst loading and unloading operations at a petroleum refinery.

Science.gov (United States)

Lewis, Ryan C; Gaffney, Shannon H; Le, Matthew H; Unice, Ken M; Paustenbach, Dennis J

2012-09-01

Workers handle catalysts extensively at petroleum refineries throughout the world each year; however, little information is available regarding the airborne concentrations and plausible exposures during this type of work. In this paper, we evaluated the airborne concentrations of 15 metals and total dust generated during solid catalyst loading and unloading operations at one of the largest petroleum refineries in the world using historical industrial hygiene samples collected between 1989 and 2006. The total dust and metals, which included aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, platinum, silicon, silver, vanadium, and zinc, were evaluated in relation to the handling of four different types of solid catalysts associated with three major types of catalytic processes. Consideration was given to the known components of the solid catalysts and any metals that were likely deposited onto them during use. A total of 180 analytical results were included in this analysis, representing 13 personal and 54 area samples. Of the long-term personal samples, airborne concentrations of metals ranged from refinery and perhaps other modern refineries during the timeframe examined. Copyright © 2011 Elsevier GmbH. All rights reserved.

System Li2O-MoO3 as a catalyst of oxygen (air) electrode

International Nuclear Information System (INIS)

Gavdzik, A.; Gajda, S.; Sofronkov, A.

2000-01-01

Potential of electrode on the basis of system Li x Mo 2-x O 6 (x 0.1-0.5) in alkaline solution saturated by oxygen was studied by the method of polarization curves recording. It is ascertained that the value of stationary potential characteristic of the electrode described under the conditions mentioned is determined by reversible reaction between oxygen and water molecules, resulting in formation of hydroxyl and hydrogen peroxide anions. Practicability of using the solid solutions on the basis of molybdenum oxide with additions of lithium oxide as a catalyst of oxygen (air) electrode in electrochemical current sources is demonstrated [ru

Air-water transfer of hydrogen sulfide

DEFF Research Database (Denmark)

Yongsiri, C.; Vollertsen, J.; Rasmussen, M. R.

2004-01-01

The emissions process of hydrogen sulfide was studied to quantify air–water transfer of hydrogen sulfide in sewer networks. Hydrogen sulfide transfer across the air–water interface was investigated at different turbulence levels (expressed in terms of the Froude number) and pH using batch...... experiments. By means of the overall mass–transfer coefficient (KLa), the transfer coefficient of hydrogen sulfide (KLaH2S), referring to total sulfide, was correlated to that of oxygen (KLaO2) (i.e., the reaeration coefficient). Results demonstrate that both turbulence and pH in the water phase play...... a significant role for KLaH2S. An exponential expression is a suitable representation for the relationship between KLaH2S and the Froude number at all pH values studied (4.5 to 8.0). Because of the dissociation of hydrogen sulfide, KLaH2S increased with decreasing pH at a constant turbulence level. Relative...

The XUV spectra of highly ionised molybdenum

International Nuclear Information System (INIS)

Mansfield, M.W.D.; Peacock, N.J.; Smith, C.C.; Hobby, M.G.; Cowan, R.D.

1978-01-01

The spectra of molybdenum ions produced in Tokamaks in the wavelength range 10-200 A have been reproduced in a plasma formed by laser beam irradiation of solid molybdenum targets. Lines from highly ionised stages of molybdenum (Mo XXX to Mo XXXII) have been distinguished by varying the laser beam intensity. Detailed analyses of the simpler ions, Mo XV (Ni-like), Mo XVI (Co-like), Mo XXXII (Na-like), and to a lesser extent Mo XXXI (Mg-like) and Mo XVII (Fe-like), have been achieved by comparison with ab initio calculations. A general interpretation of intermediate ion stages is also given but it is shown that most of these spectra are so complex, as a result of inner-subshell excitation, that detailed term-scheme analyses are nearly impossible. (author)

Oxidative desulfurization of diesel by potato based-carbon as green support for H5PMo10V2O40: Efficient composite nanorod catalyst

Directory of Open Access Journals (Sweden)

Ezzat Rafiee

2017-07-01

Full Text Available The C@POM (carbon@polyoxometalate containing H3PMo12O40 (PMo12, H5PMo10V2O40 (PMo10V2, H6PMo9V3O40 (PMo9V3, H7PMo8V4O40 (PMo8V4, H3PW12O40 (PW, and H4SiW12O40 (SiW were prepared from natural potato as green, and cheap catalyst support source. The C@PMo10V2 was found to be a unique, effective, and eco-friendly catalyst for selective oxidation of sulfides, using 30% aq. H2O2. C@PMo10V2 composite was characterized by X-ray diffraction spectroscopy (XRD, energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM, thermal gravimetric analysis (TGA, Fourier transform infrared (FT-IR spectrophotometry, zeta sizer, and zeta potential. The XRD results show that during immobilization PMo10V2 on the carbon catalyst support (CCS, the crystallite structure of PMo10V2 and CCS was not changed. The SEM results show that PMo10V2 crystals deposited on the surface CCS rods as composite nanorod structure. A variety of sulfides, sulfur-containing model and real oil were oxidized with the C@PMo10V2/H2O2 at room temperature. Recovered catalyst show excellent activity for at least four repeating cycles.

Catalytic applications of niobium compounds

International Nuclear Information System (INIS)

Wright, C.J.; England, W.A.

1984-01-01

This article examines the potential uses of niobium, and its compounds, as catalysts in chemical processing. The word potential is deliberately chosen because in 1978 none of the world's twenty-five major catalysts (1) contained niobium. On the other hand, catalysts containing molybdenum and vanadium, neighbors of niobium in the periodic table, realized over 80 x 10 6 of sales in that same year. At the same time many of the patents for niobium catalysts cover applications in which niobium improves the activity of, or substitutes for, molybdenum based compounds. With favorable cost differentials and improvements in understanding, niobium may be able to replace molybdenum in some its traditional uses

Uranium and Molybdenum extraction from a Cerro Solo deposit ore

International Nuclear Information System (INIS)

Becquart, Elena T.; Arias, Maria J.; Fuente, Juan C. de la; Misischia, Yamila A.; Santa Cruz, Daniel E.; Tomellini, Guido C.

2009-01-01

Cerro Solo, located in Chubut, Argentina, is a sandstone type uranium-molybdenum deposit. Good recovery of both elements can be achieved by acid leaching of the ore but the presence of molybdenum in pregnant liquors is an inconvenient to uranium separation and purification. A two steps process is developed. A selective alkaline leaching of the ore with sodium hydroxide allows separating and recovering of molybdenum and after solid-liquid separation, the ore is acid leached to recover uranium. Several samples averaging 0,2% uranium and 0,1% molybdenum with variable U/Mo ratio have been used and in both steps, leaching and oxidant reagents concentration, temperature and residence time in a stirred tank leaching have been studied. In alkaline leaching molybdenum recoveries greater than 96% are achieved, with 1% uranium extraction. In acid leaching up to 93% of the uranium is extracted and Mo/U ratio in solvent extraction feed is between 0,013 and 0,025. (author)

Modeling of Syngas Reactions and Hydrogen Generation Over Sulfides

Energy Technology Data Exchange (ETDEWEB)

Kamil Klier; Jeffery A. Spirko; Michael L. Neiman

2002-09-17

The objective of the research is to analyze pathways of reactions of hydrogen with oxides of carbon over sulfides, and to predict which characteristics of the sulfide catalyst (nature of metal, defect structure) give rise to the lowest barriers toward oxygenated hydrocarbon product. Reversal of these pathways entails the generation of hydrogen, which is also proposed for study. In this first year of study, adsorption reactions of H atoms and H{sub 2} molecules with MoS{sub 2}, both in molecular and solid form, have been modeled using high-level density functional theory. The geometries and strengths of the adsorption sites are described and the methods used in the study are described. An exposed MO{sup IV} species modeled as a bent MoS{sub 2} molecule is capable of homopolar dissociative chemisorption of H{sub 2} into a dihydride S{sub 2}MoH{sub 2}. Among the periodic edge structures of hexagonal MoS{sub 2}, the (1{bar 2}11) edge is most stable but still capable of dissociating H{sub 2}, while the basal plane (0001) is not. A challenging task of theoretically accounting for weak bonding of MoS{sub 2} sheets across the Van der Waals gap has been addressed, resulting in a weak attraction of 0.028 eV/MoS{sub 2} unit, compared to the experimental value of 0.013 eV/MoS{sub 2} unit.

Mechanical properties of molybdenum coated with titanium carbide film

International Nuclear Information System (INIS)

Shikama, T.; Shinno, H.; Fukutomi, M.; Fujitsuka, M.; Okada, M.

1983-01-01

TiC-coated molybdenum is mechanically tensile tested. The 6 μm thick TiC-coated molybdenum has a higher 0.2% proof strength with a slight decrease in uniform and rupture elongation than the uncoated one. This strengthening effect of the TiC coating can be explained by the constrained effect of the high strength TiC film. The 1.2 μm thick TiC-coated molybdenum starts its plastic deformation at a lower stress than the uncoated one. Also, the coating makes the stress-strain curve more smooth. These effects are attributed to the surface effect, namely, that the interface between the molybdenum substrate and the strong and brittle TiC film acts as a strong dislocation source. The compressive stress in the TiC film will also help the start of plastic deformation at lower external stresses. (author)

Sulfidation behavior of Fe20Cr alloys

International Nuclear Information System (INIS)

Pillis, Marina Fuser

2001-01-01

Alloys for use in high temperature environments rely on the formation of an oxide layer for their protection. Normally, these protective oxides are Cr 2 O 3 , Al 2 O 3 and, some times, SiO 2 . Many industrial gaseous environments contain sulfur. Sulfides, formed in the presence of sulfur are thermodynamically less stable, have lower melting points and deviate much more stoichiometrically, compared to the corresponding oxides. The mechanism of sulfidation of various metals is as yet not clear, in spite of the concerted efforts during the last decade. To help address this situation, the sulfidation behavior of Fe20Cr has been studied as a function of compositional modifications and surface state of the alloy. The alloys Fe20Cr, Fe20Cr0.7Y, Fe20Cr5Al and Fe20Cr5Al0.6Y were prepared and three sets of sulfidation tests were carried out. In the first set, the alloys were sulfidized at 700 deg C and 800 deg C for 10h. In the second set, the alloys were pre-oxidized at 1000 deg C and then sulfidized at 800 deg C for up to 45h. In the third set of tests, the initial stages of sulfidation of the alloys was studied. All the tests were carried out in a thermobalance, in flowing H 2 /2%H 2 S, and the sulfidation behavior determined as mass change per unit area. Scanning electron microscopy coupled to energy dispersive spectroscopy and X-ray diffraction analysis were used to characterize the reaction products. The addition of Y and Al increased sulfidation resistance of Fe20Cr. The addition of Y altered the species that diffused predominantly during sulfide growth. It changed from predominant cationic diffusion to predominant anionic diffusion. The addition of Al caused an even greater increase in sulfidation resistance of Fe20Cr, with the parabolic rate constant decreasing by three orders of magnitude. Y addition to the FeCrAl alloy did not cause any appreciable alteration in sulfidation resistance. Pre-oxidation of the FeCrAl and FeCrAlY alloys resulted in an extended

Synthesis and characterization of MoS2/Ti composite coatings on Ti6Al4V prepared by laser cladding

Science.gov (United States)

Yang, Rongjuan; Liu, Zongde; Wang, Yongtian; Yang, Guang; Li, Hongchuan

2013-02-01

The MoS2/Ti composite coating with sub-micron grade structure has been prepared on Ti6Al4V by laser method under argon protection. The morphology, microstructure, microhardness and friction coefficient of the coating were examined. The results indicated that the molybdenum disulfide was decomposed during melting and resolidification. The phase organization of composite coating mainly consisted of ternary element sulfides, molybdenum sulfides and titanium sulfides. The friction coefficient of and the surface roughness the MoS2/Ti coating were lower than those of Ti6Al4V. The composite coating exhibits excellent adhesion to the substrates, less surface roughness, good wear resistance and harder surface.

Crystalline silicon films sputtered on molybdenum A study of the silicon-molybdenum interface

Energy Technology Data Exchange (ETDEWEB)

Reinig, P.; Fenske, F.; Fuhs, W.; Schoepke, A.; Selle, B

2003-04-15

Polycrystalline silicon films were grown on molybdenum (Mo)-coated substrates at high deposition rate using the pulsed magnetron sputtering technique. Our study investigates the silicon-molybdenum interface of these films to elucidate stimulating mechanisms for an ordered crystalline silicon thin film growth. Both Auger electron spectroscopy and Rutherford backscattering reveal that at a substrate temperature as low as T{sub S}=450 deg. C during the deposition process intermixing of Si and Mo at the Si-Mo interface takes place leading to a compositional ratio Mo:Si of about 1:2. By Raman spectroscopy hexagonal {beta}-MoSi{sub 2} could be identified as the dominant phase in this intermixed region. The dependence of the resulting thickness of the reacted interface layer on the deposition conditions is not fully understood yet.

Crystalline silicon films sputtered on molybdenum A study of the silicon-molybdenum interface

International Nuclear Information System (INIS)

Reinig, P.; Fenske, F.; Fuhs, W.; Schoepke, A.; Selle, B.

2003-01-01

Polycrystalline silicon films were grown on molybdenum (Mo)-coated substrates at high deposition rate using the pulsed magnetron sputtering technique. Our study investigates the silicon-molybdenum interface of these films to elucidate stimulating mechanisms for an ordered crystalline silicon thin film growth. Both Auger electron spectroscopy and Rutherford backscattering reveal that at a substrate temperature as low as T S =450 deg. C during the deposition process intermixing of Si and Mo at the Si-Mo interface takes place leading to a compositional ratio Mo:Si of about 1:2. By Raman spectroscopy hexagonal β-MoSi 2 could be identified as the dominant phase in this intermixed region. The dependence of the resulting thickness of the reacted interface layer on the deposition conditions is not fully understood yet

Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst

International Nuclear Information System (INIS)

Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Michal; Skupinski, Wincenty

2011-01-01

Highlights: → A novel catalyst H 3 PO 4 /MoO 3 /SiO 2 was characterized and used in nitration. → On the surface domains of phosphomolybdic acid (HPM) are obtained. → Dinitrotoluene is obtained with very high yield i.e. 96 wt.% in mild conditions. → Dinitrochlorobenzene is obtained with only twelve-fold excess of nitric acid. → It is sulfuric acid free and solvent free nitration of aromatic compounds. - Abstract: A new catalyst, H 3 PO 4 /MoO 3 /SiO 2 , was prepared by modification of MoO 3 /SiO 2 using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds.

Study of molybdenum(VI) dimerization equilibrium in strongly acidic medium

International Nuclear Information System (INIS)

Esbelin, E.

2000-01-01

Molybdenum (VI) was investigated spectro-photometrically in non complexing and strongly acidic medium for the first time by Krumenacker. Cationic species of molybdenum were identified by electrophoresis on cellulose paper in highly acidic solutions. From these early results using absorption spectrophotometry, Krumenacker postulated the condensation of molybdenum in this medium. He studied the polymeric species by measuring diffusion coefficients and identified the polymeric form as a dimer. He described the system by equations (1) and (2). Cruywagen later added two equations (3) and (4) to supplement the description of the system. The aim of this work was to re-examine the conditional dimerization equilibrium between the various species of molybdenum(VI) in strongly acid medium by focussing on the influence of the medium. All Mo solution concentrations were analyzed by ICP-AES. Absorbance of the solutions were measured with a VARIAN model CARY5 spectrophotometer in double beam mode with air as reference; blank solutions contained all reagents except molybdenum. The quartz cell path length was 1 mm. The dimerization of monomeric molybdenum(VI) was investigated spectro-photometrically at perchloric acid concentrations of 0.5, 1.0, 2.0 and 3 M at 25 deg C. Two absorption bands at 215 and 245 nm were observed and attributed to monomeric and dimeric forms respectively. The variations in the conditional molar absorption coefficient of molybdenum with total molybdenum(VI) concentration is indicative of several molybdenum forms involved in the total absorbance. Dimerization equilibrium is defined by equation (5). By using the additivity of absorbance and mass conservation of molybdenum, a descriptive equation of the 'spectrochemical' system is developed. This equation is linearized into two forms (6) et (7). From them, two refinement methods were used to estimate the conditional dimerization constant K' d for various medium concentrations. This numerical procedure offers

Sulfide intrusion and detoxification in seagrasses ecosystems

DEFF Research Database (Denmark)

Hasler-Sheetal, Harald; Holmer, Marianne

Sulfide intrusion in seagrasses represents a global threat to seagrasses and thereby an important parameter in resilience of seagrass ecosystems. In contrast seegrasses colonize and grow in hostile sediments, where they are constantly exposed to invasion of toxic gaseous sulfide. Remarkably little...... strategies of seagrasses to sustain sulfide intrusion. Using stable isotope tracing, scanning electron microscopy with x-ray analysis, tracing sulfur compounds combined with ecosystem parameters we found different spatial, intraspecific and interspecific strategies to cope with sulfidic sediments. 1...... not present in terrestrial plants at that level. Sulfide is not necessarily toxic but used as sulfur nutrition, presupposing healthy seagrass ecosystems that can support detoxification mechanisms. Presence or absence of those mechanisms determines susceptibility of seagrass ecosystems to sediment sulfide...

Study to improve the quality of a Mexican straight run gasoil over NiMo/γ-Al2O3 catalysts

International Nuclear Information System (INIS)

Dominguez-Crespo, M.A.; Diaz-Garcia, L.; Arce-Estrada, E.M.; Torres-Huerta, A.M.; Cortez de la Paz, M.T.

2006-01-01

Four NiMo catalyst supported on Al 2 O 3 with different textural properties have been studied in the hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) of a Mexican straight run gasoil (SRGO). All reactions were carried out at three different temperatures 613, 633, and 653 K. Alumina supports were analysed by pyridine FTIR-TPD and nitrogen physisorption in order to determine their surface acidity and textural properties, respectively. TPR studies of the NiMo catalysts were analysed to correlate their hydrogenating properties. Metallic particles were characterized (after sulfidation) using transmission electron microscopy (TEM). Catalytic activities are discussed in relation to the physicochemical properties of NiMo catalysts. The importance of textural properties on coke deposition has been emphasized. The results of catalytic activity of these materials varied depending on dispersed MoS particles and pore distribution in final catalysts. The optimum pore diameter was found around 80 A for HDS and HDN

Study to improve the quality of a Mexican straight run gasoil over NiMo/γ-Al 2O 3 catalysts

Science.gov (United States)

Domínguez-Crespo, M. A.; Díaz-García, L.; Arce-Estrada, E. M.; Torres-Huerta, A. M.; Cortéz-De la Paz, M. T.

2006-11-01

Four NiMo catalyst supported on Al 2O 3 with different textural properties have been studied in the hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) of a Mexican straight run gasoil (SRGO). All reactions were carried out at three different temperatures 613, 633, and 653 K. Alumina supports were analysed by pyridine FTIR-TPD and nitrogen physisorption in order to determine their surface acidity and textural properties, respectively. TPR studies of the NiMo catalysts were analysed to correlate their hydrogenating properties. Metallic particles were characterized (after sulfidation) using transmission electron microscopy (TEM). Catalytic activities are discussed in relation to the physicochemical properties of NiMo catalysts. The importance of textural properties on coke deposition has been emphasized. The results of catalytic activity of these materials varied depending on dispersed MoS particles and pore distribution in final catalysts. The optimum pore diameter was found around 80 Å for HDS and HDN.

Femtosecond laser surface structuring of molybdenum thin films

Energy Technology Data Exchange (ETDEWEB)

Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

2015-10-30

Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

A molybdenum disulfide/carbon nanotube heterogeneous complementary inverter.

Science.gov (United States)

Huang, Jun; Somu, Sivasubramanian; Busnaina, Ahmed

2012-08-24

We report a simple, bottom-up/top-down approach for integrating drastically different nanoscale building blocks to form a heterogeneous complementary inverter circuit based on layered molybdenum disulfide and carbon nanotube (CNT) bundles. The fabricated CNT/MoS(2) inverter is composed of n-type molybdenum disulfide (MOS(2)) and p-type CNT transistors, with a high voltage gain of 1.3. The CNT channels are fabricated using directed assembly while the layered molybdenum disulfide channels are fabricated by mechanical exfoliation. This bottom-up fabrication approach for integrating various nanoscale elements with unique characteristics provides an alternative cost-effective methodology to complementary metal-oxide-semiconductors, laying the foundation for the realization of high performance logic circuits.

WATER-GAS SHIFT KINETICS OVER IRON OXIDE CATALYSTS AT MEMBRANE REACTOR CONDITIONS; A

International Nuclear Information System (INIS)

Carl R.F. Lund

2001-01-01

This report covers the second year of a project investigating water-gas shift catalysts for use in membrane reactors. It has been established that a simple iron high temperature shift catalyst becomes ineffective in a membrane reactor because the reaction rate is severely inhibited by the build-up of the product CO(sub 2). During the past year, an improved microkinetic model for water-gas shift over iron oxide was developed. Its principal advantage over prior models is that it displays the correct asymptotic behavior at all temperatures and pressures as the composition approaches equilibrium. This model has been used to explore whether it might be possible to improve the performance of iron high temperature shift catalysts under conditions of high CO(sub 2) partial pressure. The model predicts that weakening the surface oxygen bond strength by less than 5% should lead to higher catalytic activity as well as resistance to rate inhibition at higher CO(sub 2) partial pressures. Two promoted iron high temperature shift catalysts were studied. Ceria and copper were each studied as promoters since there were indications in the literature that they might weaken the surface oxygen bond strength. Ceria was found to be ineffective as a promoter, but preliminary results with copper promoted FeCr high temperature shift catalyst show it to be much more resistant to rate inhibition by high levels of CO(sub 2). Finally, the performance of sulfided CoMo/Al(sub 2)O(sub 3) catalysts under conditions of high CO(sub 2) partial pressure was simulated using an available microkinetic model for water-gas shift over this catalyst. The model suggests that this catalyst might be quite effective in a medium temperature water-gas shift membrane reactor, provided that the membrane was resistant to the H(sub 2)S that is required in the feed

Study on the influence of nickel and Al{sub 2}O{sub 3} support on MoS{sub 2} as hydrodenitrogenation catalysts

Energy Technology Data Exchange (ETDEWEB)

Hein, J.; Hrabar, A.; Gutierrez, O.Y.; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Catalysis Research Center

2012-07-01

Alumina-supported Mo and Ni-Mo catalysts as well as an unsupported NiMo catalyst were characterized and tested in the hydrodenitrogenation (HDN) of quinoline in the presence of dibenzothiophene (DBT). The supported catalysts had a well dispersed MoS{sub 2} phase with an average stacking degree around two and slabs length below 10 nm. The unsupported NiMo sulfide catalyst exhibited long, multistacked MoS{sub 2} slabs and contained segregated Ni{sub x}S{sub y} phases. The formation of the Ni-Mo-S phase in both Ni containing catalysts was verified by X-ray absorption spectroscopy, whereas the concentration of coordinatively unsaturated sites was higher for the supported Mo and Ni-Mo catalysts than for the unsupported one. All catalysts were active in the HDN of quinoline and hydrodesulfurization of DBT. The catalytic activity increased in the order Mo/Al{sub 2}O{sub 3} < NiMo/unsupported < Ni-Mo/Al{sub 2}O{sub 3}. Thus, the influence on the catalytic activity of the promoter metal Ni is more important than the presence of a support due to the formation of the Ni-Mo-S phase (more active than MoS{sub 2}). (orig.)

30 CFR 250.504 - Hydrogen sulfide.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.504 Section 250.504... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Completion Operations § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in...

30 CFR 250.604 - Hydrogen sulfide.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.604 Section 250.604... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Workover Operations § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in...

Carbon steel protection in G.S. (Girlder sulfide) plants. Iron sulfide scales formation conditions. Pt. 1

International Nuclear Information System (INIS)

Bruzzoni, P.; Burkart, A.L.; Garavaglia, R.N.

1981-11-01

An ASTM A 516 degree 60 carbon steel superficial protection technique submitted to a hydrogen-water sulfide corrosive medium at 2 MPa of pressure and 40-125 deg C forming on itself an iron sulfide layer was tested. Studies on pH influence, temperature, passivating mean characteristics and exposure time as well as the mechanical resistance of sulfide layers to erosion are included. (Author) [es

Neutron scattering and models: molybdenum

International Nuclear Information System (INIS)

Smith, A.B.

1999-01-01

A comprehensive interpretation of the fast-neutron interaction with elemental and isotopic molybdenum at energies of le 30 MeV is given. New experimental elemental-scattering information over the incident energy range 4.5 r a rrow 10 MeV is presented. Spherical, vibrational and dispersive models are deduced and discussed, including isospin, energy-dependent and mass effects. The vibrational models are consistent with the ''Lane potential''. The importance of dispersion effects is noted. Dichotomies that exist in the literature are removed. The models are vehicles for fundamental physical investigations and for the provision of data for applied purposes. A ''regional'' molybdenum model is proposed. Finally, recommendations for future work are made

FY16 Status Report for the Uranium-Molybdenum Fuel Concept

International Nuclear Information System (INIS)

Bennett, Wendy D.; Doherty, Ann L.; Henager, Charles H.; Lavender, Curt A.; Montgomery, Robert O.; Omberg, Ronald P.; Smith, Mark T.; Webster, Ryan A.

2016-01-01

The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. Uranium-Molybdenum fuel has the potential to provide superior performance based on its thermo-physical properties. With sufficient development, it may be able to provide the Light Water Reactor industry with a melt-resistant, accident-tolerant fuel with improved safety response. The Pacific Northwest National Laboratory has been tasked with extrusion development and performing ex-reactor corrosion testing to characterize the performance of Uranium-Molybdenum fuel in both these areas. This report documents the results of the fiscal year 2016 effort to develop the Uranium-Molybdenum metal fuel concept for light water reactors.

FY16 Status Report for the Uranium-Molybdenum Fuel Concept

Energy Technology Data Exchange (ETDEWEB)

Bennett, Wendy D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Doherty, Ann L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Montgomery, Robert O. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Omberg, Ronald P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Mark T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Webster, Ryan A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-09-22

The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. Uranium-Molybdenum fuel has the potential to provide superior performance based on its thermo-physical properties. With sufficient development, it may be able to provide the Light Water Reactor industry with a melt-resistant, accident-tolerant fuel with improved safety response. The Pacific Northwest National Laboratory has been tasked with extrusion development and performing ex-reactor corrosion testing to characterize the performance of Uranium-Molybdenum fuel in both these areas. This report documents the results of the fiscal year 2016 effort to develop the Uranium-Molybdenum metal fuel concept for light water reactors.

30 CFR 250.808 - Hydrogen sulfide.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.808 Section 250.808... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Production Safety Systems § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S...

A highly sensitive method for detection of molybdenum-containing proteins

International Nuclear Information System (INIS)

Kalakutskii, K.L.; Shvetsov, A.A.; Bursakov, S.A.; Letarov, A.V.; Zabolotnyi, A.I.; L'vov, N.P.

1992-01-01

A highly sensitive method for detection of molybdenum-containing proteins in gels after electrophoresis has been developed. The method involves in vitro labeling of the proteins with the radioactive isotope 185 W. The method used to detect molybdenum-accumulating proteins in lupine seeds, xanthine dehydrogenase and another molybdenum-containing protein in wheat, barley, and pea seedlings, and nitrate reductase and xanthine dehydrogenase in bacteroides from lupine nodules. Nitrogenase could not be detected by the method. 16 refs., 5 figs

Molybdenum(6) complexing with ethylenediaminedisuccinic acid from PMR spectroscopy data

International Nuclear Information System (INIS)

Larchenko, V.E.; Kovaleva, I.B.; Mitrofanova, N.D.; Martynenko, L.I.

1989-01-01

Methods of high resolution PMR spectroscopy and pH potentiometry are used to study molybdenum(6) complexing with ethylenediaminedisuccinic acid in aqueous solutions. It is shown that molybdenum(6) interacts with ethylenediaminedisuccinic acid in the narrow range of pH values 4.0-6.5, where MoO 3 H 2 L 2 - and MoO 3 HL 3- complexes with asymmetrical structure are formed. Composition and structure of molybdenum(6) ethylenediaminedisuccinates and ethylenediaminetetraacetates are compared

Mechanochemical reduction of copper sulfide

DEFF Research Database (Denmark)

Balaz, P.; Takacs, L.; Jiang, Jianzhong

2002-01-01

The mechanochemical reduction of copper sulfide with iron was induced in a Fritsch P-6 planetary mill, using WC vial filled with argon and WC balls. Samples milled for specific intervals were analyzed by XRD and Mossbauer spectroscopy. Most of the reaction takes place during the first 10 min...... of milling and only FeS and Cu are found after 60 min. The main chemical process is accompanied by phase transformations of the sulfide phases as a result of milling. Djurleite partially transformed to chalcocite and a tetragonal copper sulfide phase before reduction. The cubic modification of FeS was formed...... first, transforming to hexagonal during the later stages of the process. The formation of off-stoichiometric phases and the release of some elemental sulfur by copper sulfide are also probable....

Comparison of early stages of precipitation in molybdenum-rich and molybdenum-poor maraging stainless steels

International Nuclear Information System (INIS)

Andersson, M.; Stiller, K.; Haettestrand, M.

2004-01-01

Full text: The precipitation hardening process in the molybdenum-rich Sandvik alloy 1RK91, with composition 12.8Cr-8.6Ni-2.3Mo-1.7Cu-1.2Ti-0.7Al (at. %), has previously been investigated with APFIM, energy-filtering transmission electron microscopy, and conventional transmission electron microscopy. The initial ageing response corresponds to Ni 3 (Al, Ti)-type precipitates, nucleating on copper clusters after only five minutes of ageing at 475 o C. After several hours of ageing, the precipitation hardening also includes contribution from molybdenum-rich quasicrystalline precipitates of icosahedral symmetry (R'), and another nickel-rich phase of type L1 0 . This complex precipitation behaviour, in combination with a resistance to coarsening of R', results in a continuous increase in material hardness for up to several hundred of hours of ageing. A significant difference in ageing response has been observed between the Sandvik alloy 1RK91 and molybdenum-poor alloy Carpenter 455 with composition 12.3Cr-7.9Ni-0.3Mo-1.8Cu-1.3Ti-0.1Al (at. %). During ageing at 475 o C, the hardness of Carpenter 455 saturates with a subsequent softening after just a few hours. The reason for the discrepancy in the ageing behaviour of the two steels is not well understood, since the precipitation reactions in Carpenter 455 have not been thoroughly surveyed. Therefore, the precipitation hardening process of Carpenter 455 has been studied, by using three-dimensional atom probe and energy-filtering transmission electron microscopy. The results have been compared with the precipitation hardening process of 1RK91 in order to explain the difference in ageing response of the two steels. Special interest has been devoted to understand the influence of molybdenum in the precipitation process of 1RK91. Refs 3 (author)

Room temperature synthesis of ReS2 through aqueous perrhenate sulfidation

Science.gov (United States)

Borowiec, Joanna; Gillin, William P.; Willis, Maureen A. C.; Boi, Filippo S.; He, Y.; Wen, J. Q.; Wang, S. L.; Schulz, Leander

2018-02-01

In this study, a direct sulfidation reaction of ammonium perrhenate (NH4ReO4) leading to a synthesis of rhenium disulfide (ReS2) is demonstrated. These findings reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS2. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The results indicated the formation of a lower symmetry (1Tʹ) ReS2 with a low degree of layer stacking.

Manufacture of good-weldable low oxygen molybdenum by powder metallurgy

International Nuclear Information System (INIS)

Hiraoka, Yutaka; Okada, Masatoshi; Akiyama, Takashi; Yamafuchi, Yasuo.

1984-01-01

In general most of commercial molybdenum is produced by the powder metallurgy method and is utilized as a superior heat-resisting material in many fields. Moreover, molybdenum is expected to be used as the first-wall components of JT-60 (JAERI Tokamak-60). However, one of major problems on molybdenum, particularly on powder metallurgy molybdenum, is that any sound welded joint is hard to be obtainable. In many cases weld pores are formed on welding and, therefore, ductility of the welded joint is severely degraded. The object of the present work is to get a sound welded joint without any weld pores by reducing impurity levels in the material. The materials were produced by modifying one or several parts in the ordinary manufacturing process of powder metallurgy molybdenum. Oxygen, nitrogen, carbon and other principal metallic impurities were chemically analysed. The above materials were then subjected to electron-beam-welding by using a melt-run technique, and the soundness of the welded joints was examined by optical microscopy. (author)

Ion exchange resin fouling of molybdenum in recovery uranium processess

International Nuclear Information System (INIS)

Zhang Guowei; Zhao Guirong

1990-09-01

The relationship between anion exchange resin fouling and molybdic acid polymerization was studied. By using potentiometer titration and laser-Raman spectroscopy the relationship of molybdic acid polymerization and the pH value of solution or the molybdenum concentration was determined. It was shown that as the concentration of initial molybdenum in solution decreases from 0.2 mol/L to 0.5 mmol/L, the pH value of starting polymerization decreased from 6.5 to 4.5. The experimental results show that the fouling of 201 x 7 resin in the acidic solution is mainly caused by the adsorbing of Mo 3 O 26 4- ion and occupying the exchange radical site of the resin. Under the leaching conditions the molybdenum and phosphate existing in the leaching liquor can form 12-molybdo-phosphate ion. It also leads to resin fouling. The molybdenum on the fouled resin can synergically be desorbed by mixed desorbents containing ammonium hydroxide and ammonium sulfate. The desorbed resin can be used for uranium adsorption and the desorbed molybdenum can be recovered by ion exchange method

Molybdenum isotope fractionation during acid leaching of a granitic uranium ore

Science.gov (United States)

Migeon, Valérie; Bourdon, Bernard; Pili, Eric; Fitoussi, Caroline

2018-06-01

As an attempt to prevent illicit trafficking of nuclear materials, it is critical to identify the origin and transformation of uranium materials from the nuclear fuel cycle based on chemical and isotope tracers. The potential of molybdenum (Mo) isotopes as tracers is considered in this study. We focused on leaching, the first industrial process used to release uranium from ores, which is also known to extract Mo depending on chemical conditions. Batch experiments were performed in the laboratory with pH ranging from 0.3 to 5.5 in sulfuric acid. In order to span a large range in uranium and molybdenum yields, oxidizers such as nitric acid, hydrogen peroxide and manganese dioxide were also added. An enrichment in heavy Mo isotopes is produced in the solution during leaching of a granitic uranium ore, when Mo recovery is not quantitative. At least two Mo reservoirs were identified in the ore: ∼40% as Mo oxides soluble in water or sulfuric acid, and ∼40% of Mo hosted in sulfides soluble in nitric acid or hydrogen peroxide. At pH > 1.8, adsorption and/or precipitation processes induce a decrease in Mo yields with time correlated with large Mo isotope fractionations. Quantitative models were used to evaluate the relative importance of the processes involved in Mo isotope fractionation: dissolution, adsorption, desorption, precipitation, polymerization and depolymerization. Model best fits are obtained when combining the effects of dissolution/precipitation, and adsorption/desorption onto secondary minerals. These processes are inferred to produce an equilibrium isotope fractionation, with an enrichment in heavy Mo isotopes in the liquid phase and in light isotopes in the solid phase. Quantification of Mo isotope fractionation resulting from uranium leaching is thus a promising tool to trace the origin and transformation of nuclear materials. Our observations of Mo leaching are also consistent with observations of natural Mo isotope fractionation taking place during

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes.

Science.gov (United States)

Hassan, Ayaz; Ticianelli, Edson A

2018-01-01

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes

Directory of Open Access Journals (Sweden)

AYAZ HASSAN

2018-04-01

Full Text Available ABSTRACT Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC anodes are revised for the following catalyst systems: (1 a carbon supported PtMo electrocatalyst submitted to heat treatments; (2 Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C; (3 ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4 Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Modeling Sulfides, pH and Hydrogen Sulfide Gas in the Sewers of San Francisco

DEFF Research Database (Denmark)

Vollertsen, Jes; Revilla, Nohemy; Hvitved-Jacobsen, Thorkild

2015-01-01

An extensive measuring campaign targeted on sewer odor problems was undertaken in San Francisco. It was assessed whether a conceptual sewer process model could reproduce the measured concentrations of total sulfide in the wastewater and H2S gas in the sewer atmosphere, and to which degree...... such simulations have potential for further improving odor and sulfide management. The campaign covered measurement of wastewater sulfide by grab sampling and diurnal sampling, and H2S gas in the sewer atmosphere was logged. The tested model was based on the Wastewater Aerobic/Anaerobic Transformations in Sewers...... (WATS) sewer process concept, which never had been calibrated to such an extensive dataset. The study showed that the model was capable of reproducing the general levels of wastewater sulfide, wastewater pH, and sewer H2S gas. It could also reproduce the general variability of these parameters, albeit...

Characterization, non-isothermal decomposition kinetics and photocatalytic water splitting of green chemically synthesized polyoxoanions of molybdenum containing phosphorus as hetero atom

International Nuclear Information System (INIS)

D’Cruz, Bessy; Samuel, Jadu; George, Leena

2014-01-01

Highlights: • CPM nanorods were synthesized by applying the principles of green chemistry. • The isoconversional method was used to analyze the effective activation energy. • The appropriate reaction models of the two decomposition stages were determined. • Photocatalytic water splitting was investigated in the presence of platinum co-catalyst. - Abstract: In here, the green synthesis and thermal characterization of a novel polyoxoanions of molybdenum containing phosphorus as hetero atom are reported. The composition and morphology of the nanorods were established by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) techniques. Thermal properties of the nanoparticles were investigated by non-isothermal analysis under nitrogen atmosphere. The values activation energy of each stage of thermal decomposition for all heating rates was calculated by Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunnose (KAS) methods. Invariant kinetic parameter (IKP) method and master plot method were also used to evaluate the kinetic parameters and mechanism for the thermal decomposition of cetylpyridinium phosphomolybdate (CPM). Photocatalytic water oxidation mechanism using CPM catalyst in the presence of platinum (Pt) co-catalyst enhances the H 2 evolution and was found to be 1.514 mmol/g/h

Characterization, non-isothermal decomposition kinetics and photocatalytic water splitting of green chemically synthesized polyoxoanions of molybdenum containing phosphorus as hetero atom

Energy Technology Data Exchange (ETDEWEB)

D’Cruz, Bessy [Department of Chemistry, Mar Ivanios College, Thiruvananthapuram 695015 (India); Samuel, Jadu, E-mail: jadu_samuel@yahoo.co.in [Department of Chemistry, Mar Ivanios College, Thiruvananthapuram 695015 (India); George, Leena [Catalysis and Inorganic Chemistry Division, National Chemical Laboratory, Pune 411008 (India)

2014-11-20

Highlights: • CPM nanorods were synthesized by applying the principles of green chemistry. • The isoconversional method was used to analyze the effective activation energy. • The appropriate reaction models of the two decomposition stages were determined. • Photocatalytic water splitting was investigated in the presence of platinum co-catalyst. - Abstract: In here, the green synthesis and thermal characterization of a novel polyoxoanions of molybdenum containing phosphorus as hetero atom are reported. The composition and morphology of the nanorods were established by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) techniques. Thermal properties of the nanoparticles were investigated by non-isothermal analysis under nitrogen atmosphere. The values activation energy of each stage of thermal decomposition for all heating rates was calculated by Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunnose (KAS) methods. Invariant kinetic parameter (IKP) method and master plot method were also used to evaluate the kinetic parameters and mechanism for the thermal decomposition of cetylpyridinium phosphomolybdate (CPM). Photocatalytic water oxidation mechanism using CPM catalyst in the presence of platinum (Pt) co-catalyst enhances the H{sub 2} evolution and was found to be 1.514 mmol/g/h.

Sulfide Intrusion and Detoxification in the Seagrass Zostera marina

DEFF Research Database (Denmark)

Hasler-Sheetal, Harald; Holmer, Marianne

2015-01-01

Gaseous sulfide intrusion into seagrasses growing in sulfidic sediments causes little or no harm to the plant, indicating the presence of an unknown sulfide tolerance or detoxification mechanism. We assessed such mechanism in the seagrass Zostera marina in the laboratory and in the field...... as sulfate throughout the plant. We conclude that avoidance of sulfide exposure by reoxidation of sulfide in the rhizosphere or aerenchyma and tolerance of sulfide intrusion by incorporation of sulfur in the plant are likely major survival strategies of seagrasses in sulfidic sediments....

Fracture toughness of 6.4 mm (0.25 inch) Arc-Cast molybdenum and molybdenum-TZM plate at room temperature and 300 oC

International Nuclear Information System (INIS)

Shields, J.A. jr.; Lipetzky, P.; Mueller, A.J.

2001-01-01

The fracture toughness of 6.4 mm (0.25 inch) low carbon arc-cast (LCAC) molybdenum and arc-cast molybdenum-TZM alloy plate were measured at room temperature and 300 o C using compact tension specimens. The effect of crack plane orientation (longitudinal vs. transverse) and annealing practice (stress-relieved vs. recrystallized) were evaluated. Depending upon the test temperature either a standard K IC or a J-integral analysis was used to obtain the toughness value. At room temperature, regardless of alloy, orientation, or microstructure, fracture toughness values between 15 and 22 MPa m 1/2 (14 and 20 ksi in 1/2 ) were measured. These K IC values were consistent with measurements by other authors. Increasing temperature improves the toughness, due to the fact that one takes advantage of the ductile-brittle transition behavior of molybdenum. At 300 o C, the fracture toughness of recrystallized LCAC and arc-cast TZM molybdenum were also similar at approximately 64 MPa m 1/2 (58 ksi in 1/2 ). In the stress-relieved condition, however, the toughness of arc-cast TZM (91 MPa m 1/2 / 83 ksi in 1/2 ) was higher than that of the LCAC molybdenum (74 MPa m 1/2 / 67 ksi in 1/2 ). (author)

Influence of Chromium and Molybdenum on the Corrosion of Nickel Based Alloys

International Nuclear Information System (INIS)

Hayes, J R; Gray, J; Szmodis, A W; Orme, C A

2005-01-01

The addition of chromium and molybdenum to nickel creates alloys with exceptional corrosion resistance in a diverse range of environments. This study examines the complementary roles of Cr and Mo in Ni alloy passivation. Four nickel alloys with varying amounts of chromium and molybdenum were studied in 1 molar salt solutions over a broad pH range. The passive corrosion and breakdown behavior of the alloys suggests that chromium is the primary element influencing general corrosion resistance. The breakdown potential was nearly independent of molybdenum content, while the repassivation potential is strongly dependant on the molybdenum content. This indicates that chromium plays a strong role in maintaining the passivity of the alloy, while molybdenum acts to stabilize the passive film after a localized breakdown event

Recovery of Tungsten and Molybdenum from Low-Grade Scheelite

Science.gov (United States)

Li, Yongli; Yang, Jinhong; Zhao, Zhongwei

2017-10-01

With most high-quality tungsten ores being exhausted, the enhancement of low-grade scheelite concentrates processing has attracted a great deal of attention. The objective of this study is to develop a method to maximize the recovery tungsten and molybdenum from a low-grade scheelite via a new acid leaching process followed by solvent extraction. Under optimal conditions (350 g/L H2SO4, 95°C, and 2 h), approximately 99.8% of tungsten and 98% of molybdenum were leached out. In the subsequent solvent extraction process, more than 99% of the tungsten and molybdenum were extracted with a co-extraction system (50% TBP, 30% HDEHP, and 10% 2-octanol in kerosene) using a three-stage cross-flow extraction. The raffinate can be recycled for the next leaching process after replenishing the H2SO4 to the initial value (approximately 350 g/L). Based on these results, a conceptual flowsheet is presented to recover tungsten and molybdenum from the low-grade scheelite.

Change of mechanical properties of molybdenum after chemical heat treatment

International Nuclear Information System (INIS)

Skuratov, L.P.; Yatsimirskij, V.K.; Kirillova, N.V.

1987-01-01

Gaseous media (argon, ammonia, nitrogen-hydrogen-ammonia mixture) are studied for their effect on mechanical characteristics of molybdenum at temperatures up to 1000 deg C. It is established that the highest hardening occurs when molybdenum is esposed in the nitrogen-hydrogen medium, while the highest lost of strength takes place in the ammonia medium. An increase of the ammonia concentration in nitrogen-hydrogen-ammonia mixture promotes regular increasing of the deformation rate. With ammonia concentration of 33.3% the gaseous mixture acts the same as pure ammonia. Change of physical-and-mechanical properties of molybdenum under the action of nitrogen-containing gaseous media is associated with formation of molybdenum compounds with nitrogen. During nitriding in ammonia an internal (volume) nitriding proceeds while in the medium of nitrogen-hydrogen mixture surface nitride layers form

Effect of H2S on Pyridine HDN over Ir, Mo and Ir-Mo/Al2O3 Sulfide Catalysts

Czech Academy of Sciences Publication Activity Database

Vít, Zdeněk; Cinibulk, Josef

2002-01-01

Roč. 77, č. 1 (2002), s. 43-49 ISSN 0133-1736 R&D Projects: GA AV ČR IAA4072103 Keywords : HDN * Mo sulfide * iridium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.398, year: 2002

Environmental Benign Process for Production of Molybdenum Metal from Sulphide Based Minerals

Science.gov (United States)

Rajput, Priyanka; Janakiram, Vangada; Jayasankar, Kalidoss; Angadi, Shivakumar; Bhoi, Bhagyadhar; Mukherjee, Partha Sarathi

2017-10-01

Molybdenum is a strategic and high temperature refractory metal which is not found in nature in free state, it is predominantly found in earth's crust in the form of MoO3/MoS2. The main disadvantage of the industrial treatment of Mo concentrate is that the process contains many stages and requires very high temperature. Almost in every step many gaseous, liquid, solid chemical substances are formed which require further treatment. To overcome the above drawback, a new alternative one step novel process is developed for the treatment of sulphide and trioxide molybdenum concentrates. This paper presents the results of the investigations on molybdenite dissociation (MoS2) using microwave assisted plasma unit as well as transferred arc thermal plasma torch. It is a single step process for the preparation of pure molybdenum metal from MoS2 by hydrogen reduction in thermal plasma. Process variable such as H2 gas, Ar gas, input current, voltage and time have been examined to prepare molybdenum metal. Molybdenum recovery of the order of 95% was achieved. The XRD results confirm the phases of molybdenum metal and the chemical analysis of the end product indicate the formation of metallic molybdenum (Mo 98%).

Reduction of molybdate to molybdenum blue by Klebsiella sp. strain hkeem.

Science.gov (United States)

Lim, H K; Syed, M A; Shukor, M Y

2012-06-01

A novel molybdate-reducing bacterium, tentatively identified as Klebsiella sp. strain hkeem and based on partial 16s rDNA gene sequencing and phylogenetic analysis, has been isolated. Strain hkeem produced 3 times more molybdenum blue than Serratia sp. strain Dr.Y8; the most potent Mo-reducing bacterium isolated to date. Molybdate was optimally reduced to molybdenum blue using 4.5 mM phosphate, 80 mM molybdate and using 1% (w/v) fructose as a carbon source. Molybdate reduction was optimum at 30 °C and at pH 7.3. The molybdenum blue produced from cellular reduction exhibited absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of electron transport system such as antimycin A, rotenone, sodium azide, and potassium cyanide did not inhibit the molybdenum-reducing enzyme. Mercury, silver, and copper at 1 ppm inhibited molybdenum blue formation in whole cells of strain hkeem. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of molybdenum and phosphate modified kaolin in electrochemical treatment of paper mill wastewater

International Nuclear Information System (INIS)

Ma Hongzhu; Wang Bo; Wang Ying

2007-01-01

Pulp and paper mill wastewater is characterized by very high chemical oxygen demand (COD) values that inhibit the activity of microorganisms during biological oxidations. The electrochemical degradation of pulp and paper mill wastewater catalyzed by molybdenum and phosphate (Mo-P) modified kaolin with graphite as anode and cathode was investigated. The catalyst was characterized by XRD, XPS and SEM spectra and the effects of pH, metal ion and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found out that the modified kaolin loaded with Fe 3+ had higher electrochemical catalytic activity in the electrochemical degradation of paper mill wastewater at pH 4. A 96% COD removal efficiency was obtained in 40 min of electrochemical treatment of the wastewater at current density 30 mA cm -2 . A possible mechanism for degradation of the mill wastewater constituents was also proposed

Low cycle fatigue behavior of titanium carbide coated molybdenum

International Nuclear Information System (INIS)

Nishi, Hiroshi; Oku, Tatsuo; Kodaira, Tsuneo; Kikuyama, Toshihiko

1985-09-01

Sintered molybdenum coated by TiC is used for the first wall such as a troidal fixed limiter and a magnetic limiter plate in JT-60, that is being operated at JAERI presently. This report describes the low cycle fatigue behavior of sintered molybdenum and the influence of TiC coating on fatigue strength. The low cycle fatigue test was conducted at room temperature and 500 0 C. The test results was also analyzed by fractographic observation, metallography and element analysis using EPMA. The low cycle fatigue strength of the molybdenum coated by TiC at 500 0 C is decreased compared with the one at room temperature. (author)

Synthesis and characterization of MoS2/Ti composite coatings on Ti6Al4V prepared by laser cladding

Directory of Open Access Journals (Sweden)

Rongjuan Yang

2013-02-01

Full Text Available The MoS2/Ti composite coating with sub-micron grade structure has been prepared on Ti6Al4V by laser method under argon protection. The morphology, microstructure, microhardness and friction coefficient of the coating were examined. The results indicated that the molybdenum disulfide was decomposed during melting and resolidification. The phase organization of composite coating mainly consisted of ternary element sulfides, molybdenum sulfides and titanium sulfides. The friction coefficient of and the surface roughness the MoS2/Ti coating were lower than those of Ti6Al4V. The composite coating exhibits excellent adhesion to the substrates, less surface roughness, good wear resistance and harder surface.

Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

Science.gov (United States)

Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

2015-08-01

The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Molybdenum peroxo complex. Structure and thermal behavior

Energy Technology Data Exchange (ETDEWEB)

Segawa, Koichi; Ooga, Katsumi; Kurusu, Yasuhiko

1984-10-01

The molybdenum peroxide (Mo-y) prepared by oxidation of molybdenum metal with hydrogen peroxide has been studied to determine its structure and thermal behavior. Temperature programmed decomposition has been used to study the thermal stability of Mo-y. Two distinct peaks, I and II, of decomposition processes are discernible in Mo-y. Peak I corresponds to the elimination of water of crystallization and peak II to the decomposition of a peroxide ion of Mo-y. IR and UV examinations support the results of the thermal analysis. The IR band at 931 cm/sup -1/ and the UV band at 381 nm show the same thermal behavior. Both bands are attributable to the peroxide ion of Mo-y. Spectroscopic studies show that Mo-y has the tetrahedral coordination derived from the single molybdenum complex, which has double bond oxygens attached to Mo atom and has a symmetric type of peroxide ion with one water of crystallization.

Production of Molybdenum-99 using Neutron Capture Methods

Energy Technology Data Exchange (ETDEWEB)

Toth, James J; Greenwood, Lawrence R; Soderquist, Chuck Z; Wittman, Richard S; Pierson, Bruce D; Burns, Kimberly A; Lavender, Curt A; Painter, Chad L; Love, Edward F; Wall, Donald E

2011-01-01

Pacific Northwest National Laboratory (PNNL), operated by Battelle, has identified a reference process for the production of molybdenum-99 (99Mo) for use in a chromatographic generator to separate the daughter product, technetium-99m (99mTc). The reference process uses the neutron capture reaction of natural or enriched molybdenum oxide via the reaction 98Mo(n,γ)99Mo. The irradiated molybdenum is dissolved in an alkaline solution, whereby the molybdenum, dissolved as the molybdate anion, is loaded on a proprietary ion exchange material in the chromatographic generator. The approach of this investigation is to provide a systematic collection of technologies to make the neutron capture method for Mo-99 production economically viable. This approach would result in the development of a technetium Tc99m generator and a new type of target. The target is comprised of molybdenum, either natural or enriched, and is tailored to the design of currently operating U.S. research reactors. The systematic collection of technologies requires evaluation of new metallurgical methods to produce the target, evaluation of target geometries tailored to research reactors, and chemical methods to dissolve the irradiated target materials for use in a chromatographic generator. A Technical specification for testing the target and neutron capture method in a research reactor is also required. This report includes identification of research and demonstration activities needed to enable deployment of neutron capture production method, including irradiations of prototypic targets, chemical processing of irradiated targets, and loading and extraction tests of Mo99 and Tc99m on the sorbent material in a prototypic generator design. The prototypical generator design is based on the proprietary method and systems for isotope product generation. The proprietary methods and systems described in this report are clearly delineated with footnotes. Ultimately, the Tc-99m generator solution provided by

Electron transfer to sulfides:

International Nuclear Information System (INIS)

Meneses, Ana Belen; Antonello, Sabrina; Arevalo, Maria Carmen; Maran, Flavio

2005-01-01

The problem of characterizing the steps associated with the dissociative reduction of sulfides has been addressed. The electrochemical reduction of diphenylmethyl para-methoxyphenyl sulfide in N,N-dimethylformamide, on both glassy carbon and mercury electrodes, was chosen as a test system. The electrode process involves the slow heterogeneous outer-sphere electron transfer to the sulfide, the fast cleavage of the C-S bond, the reduction of the ensuing carbon radical, and the self-protonation triggered by the generation of the strong base Ph 2 CH - . The latter reaction is rather slow, in agreement with the large intrinsic barriers characterizing proton transfers between CH-acids and carbon bases. The dissociative reduction was studied in the presence of an exogenous acid. The results, obtained by convolution analysis, point to a stepwise DET mechanism in which the ET step is accompanied by rather large reorganization energy. Similar results were obtained on both electrode materials. Analysis of the heterogeneous electron transfer and associated C-S bond cleavage indicate that the reduction of this and other sulfides lies between the stepwise dissociative electron transfers leading to the formation of stiff π* radical anions and those going through the intermediacy of loose σ* radical anions

Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs

NARCIS (Netherlands)

Klatt, Judith M.; Haas, Sebastian; Yilmaz, Pelin; de Beer, Dirk; Polerecky, Lubos

We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2S: (i) H2S accelerated the recovery of

Extraction of molybdenum with TBP-dodecane mixture in nitric medium. Application to uranium refining

International Nuclear Information System (INIS)

Donnet, Louis

1993-01-01

Uranium ores may contain high quantities of molybdenum which represents an undesirable impurity in the uranium conversion process. Thus it is necessary to check carefully its extraction and its stripping during the purification step. The purpose of this study was to investigate the molybdenum behaviour during this step. We have developed a radiochemical method for the determination of the molybdenum concentration in each phase. This method used gamma radiation of technetium 99m issued from molybdenum 99 disintegration. After a systematic study of all the extraction parameters, we have proposed mechanisms accounting for molybdenum extraction and we have calculated the constants for the different equilibria. In particular, we have furnished new data concerning the extraction of polymerised molybdenum species with tri butyl phosphate. We have also determined the polymerization constants of molybdenum in the aqueous phase. The influence of uranium and phosphate ions on the molybdenum behaviour during the extraction and stripping has been investigated. We have shown that the extraction of molybdenum was not modified by uranium but improved in the presence of phosphate ions. In the general case, we have shown that uranium, phosphate ions and the ageing of the solvent have an unfavourable effect on stripping. We have explained this result by the evolution of the complex in the organic phase to an un-stripped polymeric form. In conclusion, our study has allowed to explain the behaviour of molybdenum during the purification process, and the role of impurities present in the industrial solutions. It would serve as a guide to improve the exploitation for a better molybdenum-uranium separation. (author) [fr