Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies
Abstract
X-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO{sub 4}.nH{sub 2}O, {alpha}-AMoO{sub 4}, {beta}-AMoO{sub 4}; A=Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the {alpha}-phases to tetrahedral in the {beta}-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the {beta}-AMoO{sub 4} compounds (following a kinetics of first order) at temperatures between 200 and 350{degrees}C. This is facilitated by the similarities that the AMoO{sub 4}.nH{sub 2}O and H{sub 2} at temperatures between 400 and 600{degrees}C, forming gaseous water oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing {alpha}-NiMoO{sub 4} and {beta}-NiMoO{sub 4} to H{sub 2}S, both metals get sulfided and a NiMoS{sub x} phase is formed. For the {beta} phase of NiMoO{sub 4} the sulfidation of Mo is more extensive than for the {alpha} phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.
- Authors:
-
- Brookhaven National Lab., Upton, NY (United States)
- Centro de Quimica, Caracas (Venezuela)
- Publication Date:
- Research Org.:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Org.:
- USDOE Office of Energy Research, Washington, DC (United States)
- OSTI Identifier:
- 555287
- Report Number(s):
- BNL-64970
ON: DE98001656; TRN: 98:000152
- DOE Contract Number:
- AC02-76CH00016
- Resource Type:
- Technical Report
- Resource Relation:
- Other Information: PBD: [1998]
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE; 66 PHYSICS; NICKEL OXIDES; MOLYBDENUM OXIDES; SULFIDATION; COBALT OXIDES; X-RAY DIFFRACTION; ABSORPTION SPECTRA; CATALYSTS; OXIDATION; PHASE STUDIES
Citation Formats
Chaturvedi, S, Rodriguez, J A, Hanson, J C, Albornoz, A, and Brito, J L. Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies. United States: N. p., 1998.
Web. doi:10.2172/555287.
Chaturvedi, S, Rodriguez, J A, Hanson, J C, Albornoz, A, & Brito, J L. Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies. United States. https://doi.org/10.2172/555287
Chaturvedi, S, Rodriguez, J A, Hanson, J C, Albornoz, A, and Brito, J L. 1998.
"Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies". United States. https://doi.org/10.2172/555287. https://www.osti.gov/servlets/purl/555287.
@article{osti_555287,
title = {Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies},
author = {Chaturvedi, S and Rodriguez, J A and Hanson, J C and Albornoz, A and Brito, J L},
abstractNote = {X-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO{sub 4}.nH{sub 2}O, {alpha}-AMoO{sub 4}, {beta}-AMoO{sub 4}; A=Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the {alpha}-phases to tetrahedral in the {beta}-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the {beta}-AMoO{sub 4} compounds (following a kinetics of first order) at temperatures between 200 and 350{degrees}C. This is facilitated by the similarities that the AMoO{sub 4}.nH{sub 2}O and H{sub 2} at temperatures between 400 and 600{degrees}C, forming gaseous water oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing {alpha}-NiMoO{sub 4} and {beta}-NiMoO{sub 4} to H{sub 2}S, both metals get sulfided and a NiMoS{sub x} phase is formed. For the {beta} phase of NiMoO{sub 4} the sulfidation of Mo is more extensive than for the {alpha} phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.},
doi = {10.2172/555287},
url = {https://www.osti.gov/biblio/555287},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 31 00:00:00 EST 1998},
month = {Thu Dec 31 00:00:00 EST 1998}
}