Physical characterization of molybdenum oxycarbide catalyst; TEM, XRD and XPS

Delporte, Pascale; Meunier, Fre ́de ́ric; Pham‐Huu, Cuong; Vennéguès, P.; Ledoux, Marc J.; Guille, J.

doi:10.1016/0920-5861(94)00166-y

Cited by 214 publications

(183 citation statements)

References 23 publications

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“…MoO 3 transforms into MoO x C y H z in H 2 /C n H 2n+2 (x ≥ 2) at 623 K and MoO x C y H z will be further carburized to ␣-MoC 1−x at high temperatures. The whole process from MoO 3 to ␣-MoC 1−x is topotactic [54][55][56][57] and the formation of MoO x C y H z is believed to be the key step to form ␣-MoC 1−x [57]. While the present results show that ␣-MoC 1−x can be produced directly from the reaction between n-C 4 H 10 and MoO 3 /HZSM-5 through MoO 2 /HZSM-5.…”

Section: Evolution Of the Molybdenum Phases On Mo/hzsm-5contrasting

confidence: 47%

Relationship between the molybdenum phases and the conversion of n-butane over Mo/HZSM-5

Yuan

Hamid

et al. 2002

Journal of Molecular Catalysis A: Chemical

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Section: Evolution Of the Molybdenum Phases On Mo/hzsm-5contrasting

confidence: 47%

Relationship between the molybdenum phases and the conversion of n-butane over Mo/HZSM-5

Yuan

Hamid

et al. 2002

Journal of Molecular Catalysis A: Chemical

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“…The H1.68MoO3 phase dis appeared completely at 598 K. Pt/MoO3 heated to 998 K showed diffraction lines at 2θ 38.1 and 44.3 . The formation of an unidentified compound, with diffraction lines at around 38 and 44 , has been observed in the reduction product of MoO3, and these diffraction lines have been assigned to a Mo2O oxide 38) , MoO with a face centered cubic lattice 39), 40) , and the molybdenum oxyhydride MoOxHy phase 10) , which is analogous to molybdenum oxycarbide MoOxCy. Wehrer et al reported that the presence of hydrogen in this compound was hardly possible because thermal treatment at 973 K in a flow of He did not change the XRD pattern, and they proposed the presence of a reduced molybdenum oxide with composition near to MoO 27), 28) .…”

Section: Reduction Of Na-loaded Moo3mentioning

confidence: 99%

Reduction of MoO<sub>3</sub> to Porous Molybdenum Oxides and Its Catalytic Properties for Alkane Isomerization

Matsuda

Ohno

Sakagami

et al. 2007

J. Jpn. Petrol. Inst.

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The catalytic activity of partially reduced Pt/MoO3 for alkane isomerization was investigated. The surface area of Pt/MoO3 was markedly enlarged by H2 reduction to a maximum after reduction at 673 K for 12 h. Enlargement of the surface area was caused by formation of pores with diameters of 0.6-3 nm. The catalytic activity of partially reduced Pt/MoO3 for heptane isomerization increased with reduction temperature, and reached a maximum at 723 K. The catalytic activity for 2-propanol dehydration was very similar to that of heptane isomerization. The isomerization and dehydration activities of partially reduced Pt/Na _ MoO3 rapidly decreased with increasing content of Na. In contrast, the hydrogenation of cyclohexene was promoted on catalysts containing Na. The isomerization and dehydration activities were related to the number of acid sites, determined by NH3-TPD. Therefore, the isomerization activity of partially reduced Pt/MoO3 depends on the activity as an acid catalyst. H2 reduction at 673 K enlarged the surface areas of H1.55MoO3 and Pt/MoO3, but not the surface area of MoO3. H1.55MoO3 and Pt/MoO3 reduced at 673 K had comparable activity for pentane isomerization, and were much more active than MoO3 reduced at 673 K, even after considering the differences in surface areas. Molybdenum oxyhydride, MoOxHy, was formed after the decomposition of hydrogen molybdenum bronze in the reduction of H1.55MoO3 and Pt/MoO3. On the other hand, MoO3 was reduced to MoO2 without the formation of hydrogen bronze. These results show that surface area and isomerization activity were improved by the formation of MoOxHy from HxMoO3.

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“…During the reduction process different phases are formed, one of which is the molybdenum oxycarbide (MoO x C y ) [4][5][6][7]. The reduction of MoO 3 is the crucial step in the formation of active catalysts for the isomerization of alkanes and has been widely studied.…”

Section: Introductionmentioning

confidence: 99%

Effect of the particle size on the activity of MoOxCy catalysts for the isomerization of heptane

et al. 2005

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Molybdenum trioxide samples having apparent particle sizes (APS) of 5 and 20 l.m were partially reduced under flow of a mixture of H 2 /n-heptane during 4 h. X-ray diffraction and Raman spectroscopy showed the typical structural transformation of MoO 3 into MoO x C y and MoO 2 . These structural changes occur preferentially on the {0k0} planes. After the reduction treatment the resulting materials, having surface areas of 23 and 53 m 2 /g, were evaluated in the isomerization of n-heptane at 643 K and 18.5 bar. The catalyst with an APS of 20 l.m showed a maximum conversion around 70%, while for the catalyst with an APS of 5 l.m the maximum conversion was 34%. The lower activity of the 5 l.m MoO x C y catalyst seems to be related to a faster rate of formation of oxygen vacancies and rearrangement of the lattice into a more stable and less active structure in the case of small-size particles, due to a higher concentration of terminal Mo=O bonds along the a-and b-axes, which facilitate the electrophilic attack by hydrogen on the (010) plane.

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Physical characterization of molybdenum oxycarbide catalyst; TEM, XRD and XPS

Cited by 214 publications

References 23 publications

Relationship between the molybdenum phases and the conversion of n-butane over Mo/HZSM-5

Relationship between the molybdenum phases and the conversion of n-butane over Mo/HZSM-5

Reduction of MoO<sub>3</sub> to Porous Molybdenum Oxides and Its Catalytic Properties for Alkane Isomerization

Effect of the particle size on the activity of MoOxCy catalysts for the isomerization of heptane

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