Surface molybdenum species and acid sites on nitrided molybdena-alumina catalysts

Nagai, Masatoshi; Miyata, Akira; Kusagaya, T.; Omi, Shinzo

doi:10.1007/978-94-009-1565-7_17

Cited by 6 publications

(6 citation statements)

References 27 publications

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“…Transition-metal nitrides are active during hydrodesulfurization (HDS) − and hydrodenitrogenation ,,− and are reported to have a turnover frequency higher than commercial Co−Mo 8,15 and Ni−Mo 20 sulfide catalysts on the basis of the CO and O 2 adsorption. Recently, novel bimetallic nitrides and oxynitrides such as Co−Mo, − Fe−Mo, , Ni−Mo, , and V−Mo ,, were studied with respect to the catalytic activity and properties of the samples when synthesizing by temperature-programmed nitriding of the bimetallic oxides and a mixture of the monometallic oxides.…”

Section: Introductionmentioning

confidence: 99%

Characterization and HDS Activity of Cobalt Molybdenum Nitrides

2001

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The characterization of cobalt molybdenum nitrides with various cobalt contents has been studied using XRD, TEM, XPS, and temperature-programmed reactions with NH 3 . The hydrodesulfurization of thiophene on the cobalt molybdenum nitride was carried out using a differential microreactor at atmospheric pressure. The XRD analysis of Co( 50)973 indicated that Co 3 Mo 3 N was formed from the nitriding of a CoMoO 4 precursor prepared from Co(NO 3 ) 2 ‚6H 2 O and (NH 4 ) 6 Mo 7 O 24 ‚4H 2 O but not from the mixture of CoO and MoO 3 . Co-(10-25)973 had a high surface area of 120-129 m 2 g -1 , but Co(50)973 had that of 12 m 2 g -1 . The BET surface area was related to the molybdenum ions (Mo 2+ and Mo 3+ ) and cobalt ion (Co 3+ ) in the bulk sample. The XPS and elemental analyses of Co(50)973 showed that the bulk composition was Co 3 Mo 3 N‚N 0.2 and the surface composition was Co 3 Mo 3 N‚N 2 . The cobalt molybdenum nitride Co(0-35)973 was more active than cobalt molybdenum sulfide on basis of catalyst weight in the hydrodesulfurization of thiophene at 623 K.

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Section: Introductionmentioning

confidence: 99%

Characterization and HDS Activity of Cobalt Molybdenum Nitrides

2001

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“…Recently, molybdenum nitrides and carbides have been reported to have high activities for hydrodesulfurization and hydrodenitrogenation. − A nitrided Mo/Al 2 O 3 catalyst was reported to be about 3 times more active than the sulfided and reduced Mo/Al 2 O 3 catalysts in the HDN of carbazole 4 and pyridine . Furthermore, the alumina-supported molybdenum nitrides were more active than sulfided Mo/Al 2 O 3 catalysts for the HDS's of thiophene, benzothiophene and dibenzothiophene 6,8,9,12 and also to be extremely selective for the C−S bond breakage of dibenzothiophene to form biphenyl .…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the alumina-supported molybdenum nitrides were more active than sulfided Mo/Al 2 O 3 catalysts for the HDS's of thiophene, benzothiophene and dibenzothiophene 6,8,9,12 and also to be extremely selective for the C−S bond breakage of dibenzothiophene to form biphenyl . To elucidate the relationship between the properties of unsupported molybdenum nitrides and the activities in hydrotreating reactions, characterization has been carried out to study the adsorption/desorption of CO ,,− and O 2 , 3,7,12 TPR, ,− , XRD, ,,,− ,, XPS, ,, and NEXAFS. , The molybdenum and adsorbed nitrogen species on the unsupported molybdenum nitrides after nitriding have been studied for understanding of the active sites for the reactions. However, characterization of the nitrided molybdena-alumina rather than the unsupported molybdenum nitrides is not fully understood; whether low loading molybdenum oxides on Al 2 O 3 are nitrided, what is the nitriding degree of the molybdenum atom on Al 2 O 3 , and the relationship between the surface molybdenum species and adsorbed nitrogen species on the nitrided molybdena−alumina.…”

Section: Introductionmentioning

confidence: 99%

“…For unsupported nitrided samples, the distribution of molybdenum species was elucidated based on the release of nitrogen during TPR. In previous papers, − the combination of TPR and XRD enlightened the relationship between nitrogen desorption and the structure of molybdenum nitrides of the samples; γ-Mo 2 N was not changed while desorbing ammonia and nitrogen below 1000 K, and γ-Mo 2 N was changed to Mo metal via β-Mo 2 N 0.78 while desorbing nitrogen above 1000 K during TPR. Also, several nitrogen components for nitrogen desorption were deconvoluted and related to the molybdenum species of the samples.…”

Section: Introductionmentioning

confidence: 99%

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XPS and TPR Studies of Nitrided Molybdena−Alumina

2000

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The relationship between the surface molybdenum species and adsorbed nitrogen species on nitrided 1.0−18.7% MoO3/Al2O3 was elucidated by XPS and temperature-programmed reduction (TPR). The MoO3/Al2O3 samples were nitrided by temperature-programmed reaction with NH3. From the XPS analysis, Mo3+ and Mo4+ ions were predominant on the surface of the nitrided Mo/Al2O3 samples. From the TPR measurement, the ammonia desorption was due to nitrogen species adsorbed on alumina. The nitrogen desorption was due to two kinds of nitrogen desorption from the structures of γ-Mo2N and β-Mo2N0.78 and four kinds of nitrogen desorption from NH X species adsorbed on MoO2, Mo3+ ion (γ-Mo2N), Mo2+ ion (molybdenum nitride on alumina such as highly dispersed molybdenum nitride), and alumina.

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“…Nitrides and oxynitrides, especially those containing Si and Al, are used as high‐temperature ceramics. Transition‐metal nitrides are also interesting in terms of their electrical, magnetic, superconducting, catalytic, and mechanical properties . Oxynitrides have recently attracted attention as new functional materials for use in white light‐emitting diode (LED) phosphor applications .…”

Section: Introductionmentioning

confidence: 99%

Colored amorphous silica‐based powder with TiN nanocrystals precipitated by ammonolysis of Ti–Si–O ternary glass

2018

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Coloration of amorphous silica powder containing titania was investigated by nitridation in an ammonia flow. The oxide precursors were obtained by the hydrolysis of a mixture of tetraethyl orthosilicate (TEOS) and tetrabutoxy titanium (TBT). The color changed with the amount of TBT in the mixture, the hydrolysis pH and the ammonolysis temperature. The original white color of the 8 mol% TBT powder hydrolyzed under basic pH conditions changed to pale goldenrod at 700°C, then to dark olive green at 800°C, and further darkened with increasing ammonolysis temperature. A steel-blue color appeared at 900°C for the powder obtained with 3 mol% TBT, and increased in darkness at 1000°C. A similar bluish color was observed for powders obtained by acidic hydrolysis after ammonolysis above 900°C, and this was independent of the amount of titania, although the chroma decreased with increasing firing temperature for the powder with 3 mol% TBT. The ammonolysis powder products were characterized using X-ray diffraction (XRD), electron probe micro analysis (EPMA), transmission electron microscopy-electron energy-loss spectroscopy (TEM-EELS), scanning transmission electron microscopy-high-angle annular dark-field imaging (STEM-HAADF) and Ti-K edge X-ray absorption fine structure (XAFS). The color change was related to both precipitated TiN nanocrystals and residual titanium in the amorphous silica matrix. The TiN exhibited a goldish reflection and also plasmonic absorption from light blue to gray depending on the TiN crystallite size. The plasmonic absorption and resonance of nanocrystalline TiN will be useful similarly to that of gold in nanotechnology for various kinds of energy application.

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Surface molybdenum species and acid sites on nitrided molybdena-alumina catalysts

Cited by 6 publications

References 27 publications

Characterization and HDS Activity of Cobalt Molybdenum Nitrides

Characterization and HDS Activity of Cobalt Molybdenum Nitrides

XPS and TPR Studies of Nitrided Molybdena−Alumina

Colored amorphous silica‐based powder with TiN nanocrystals precipitated by ammonolysis of Ti–Si–O ternary glass

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