The Experts below are selected from a list of 324948 Experts worldwide ranked by ideXlab platform
Sonja Eijsbouts - One of the best experts on this subject based on the ideXlab platform.
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Electron Tomography Reveals the Active Phase–Support Interaction in Sulfidic Hydroprocessing Catalysts
ACS Catalysis, 2017Co-Authors: Sonja Eijsbouts, Jana Juan-alcaniz, Leon C. A. Van Den Oetelaar, Jaap A. Bergwerff, Joachim Loos, Anna Carlsson, Eelco T. C. VogtAbstract: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 details on the morphology of MoS2 crystallites and their interaction with the Al2O3 and TiO2 support particles. The three-dimensional (3D) reconstruction shows that the Active Phase is mainly present as MoS2 single slabs of various shapes aligned with the support. It becomes clear that the surface of the support particles is, in fact, only partly covered by the Active Phase and the pores remain accessible for reactant molecules.
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on the flexibility of the Active Phase in hydrotreating catalysts
Applied Catalysis A-general, 1997Co-Authors: Sonja EijsboutsAbstract:Abstract This review deals with the structure of the Active Phase in sulfidic Co Mo and Ni Mo hydrotreating catalysts. Various models describing the catalyst and its interaction with the reaction environment are discussed in the light of the evolution of the Active Phase during the catalyst life cycle. Special attention is paid to the contribution of Mossbauer Emission Spectroscopy (MES), Extended X-ray Absorption Fine Structure (EXAFS), High Resolution Transmission Electron Microscopy (HR-TEM) and Molecular Modeling to the unraveling of the Active Phase structure. It is concluded that MoS 2 sintering and Co 9 S 8 (Ni 3 S 2 , NiS) segregation during the catalyst life cycle force the shift of the actual reaction mechanism from that involving a single site or an ensemble of sites to that of a close cooperation between segregated components. The adsorption of reactants can take place in many diferent ways, through the heteroatom or through the ring, on the Mo sites as well as on the Co (Ni) sites. The exact state of each Active site depends on the reaction environment. If the catalyst is S deficient, the classical adsorption mechanism involving the S vacancy is dominant. With a fully sulfided catalyst surface the adsorption takes place through S S bonds. The catalyst is a dynamic evolving system adapting itself to its ever changing reaction environment. Each catalyst component fulfills multiple functions in determining the catalyst structure as well as its interaction with the reactant molecules.
Eelco T. C. Vogt - One of the best experts on this subject based on the ideXlab platform.
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Electron Tomography Reveals the Active Phase–Support Interaction in Sulfidic Hydroprocessing Catalysts
ACS Catalysis, 2017Co-Authors: Sonja Eijsbouts, Jana Juan-alcaniz, Leon C. A. Van Den Oetelaar, Jaap A. Bergwerff, Joachim Loos, Anna Carlsson, Eelco T. C. VogtAbstract: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 details on the morphology of MoS2 crystallites and their interaction with the Al2O3 and TiO2 support particles. The three-dimensional (3D) reconstruction shows that the Active Phase is mainly present as MoS2 single slabs of various shapes aligned with the support. It becomes clear that the surface of the support particles is, in fact, only partly covered by the Active Phase and the pores remain accessible for reactant molecules.
Brian M. Mercer - One of the best experts on this subject based on the ideXlab platform.
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Differences in women presenting in latent and Active Phase of labor
American Journal of Obstetrics and Gynecology, 2003Co-Authors: Jennifer L. Bailit, Leroy J. Dierker, Brian M. MercerAbstract:Phase OF LABOR JENNIFER BAILIT, LEROY DIERKER, BRIAN MERCER, MetroHealth Medical Center, Case Western Reserve University, Obstetrics/Gynecology, Cleveland, OH OBJECTIVE: Women presenting in latent Phase are at increased risk for Cesarean (CD) than those presenting in Active Phase. We sought to evaluate patient, labor, management and outcome differences between those presenting in latent Phase and Active Phase. STUDY DESIGN: We evaluated all low-risk singleton, term women with vertex presentations, presenting in Active Phase (AP: contractions with or without ROM > = 4 cm) or latent Phase (LP: contractions with or without ROM
Qinghe Yang - One of the best experts on this subject based on the ideXlab platform.
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Effect of structure and stability of Active Phase on catalytic performance of hydrotreating catalysts
Catalysis Today, 2018Co-Authors: Hong Nie, Qinghe YangAbstract:Abstract For environmental protection and efficient utilization of oil resources, higher requirements for the selectivity, activity and stability of hydrotreating catalysts are proposed. To effectively solve this issue, the influence of structure and stability of Active Phase on catalytic performance of hydrotreating catalysts was reviewed. It was realized that the Active Phase structure essentially depends on the extent of metal-support interaction, and can be properly designed by adjusting catalyst preparation parameters (e.g. support properties and metal precursors in the impregnating solution) and sulfidation conditions (e.g. pressure, temperature and gas composition). As the hydrotreating conditions for gasoline, diesel and residue become severer, the Active Phase structures need much higher stability. The selectivity of gasoline hydrodesulfurization can be notably increased by selective post-treatment of the Active Phase structure. Well-dispersed Active Phase slabs with moderate metal-support interaction are needed for highly Active and stable CoMo and NiMo diesel catalysts. New generation NiMo catalyst by strengthening metal-support interaction exhibits better residue hydrodesulfurization activity and stability.
L Daza - One of the best experts on this subject based on the ideXlab platform.
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nickel and cobalt as Active Phase on supported zirconia catalysts for bio ethanol reforming influence of the reaction mechanism on catalysts performance
International Journal of Hydrogen Energy, 2010Co-Authors: R Padilla, M Benito, L Rodriguez, A Serrano, G Munoz, L DazaAbstract:Abstract Steam reforming of ethanol for hydrogen production was investigated on Co/ZrO2 and Ni/ZrO2 catalysts promoted with lanthana. Catalysts were prepared by impregnation method and characterized by XRD and TPR. TPD-R experiments were also carried out to determine the role of Active Phase on reaction mechanism. The results suggest that adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Then, the adsorbed acetaldehyde may evolve by different mechanisms, depending on the nature of Active Phase. On one hand, in cobalt-based catalyst, acetaldehyde could be reformed directly. By acetaldehyde thermal decomposition, methyl and formaldehyde groups are obtained. By coupling of methyl groups, ethane can be obtained. At medium temperature range, WGS reaction contribution is noteworthy. On the other hand, in nickel-based catalyst, acetone was detected in a higher temperature range as the main intermediate reaction product, which indicates that acetaldehyde is transformed into acetone by decarbonylation of acetaldehyde leading to H2 and CO2 formation. In addition, acetone can also be reformed to give both H2 and CO2. Contrary to cobalt-based catalyst, ethylene was detected at intermediate range temperature which suggests that it was formed by ethanol dehydration reaction. Ethylene polymerization could easily explain coke formation, which must be avoided. Steam reforming reaction was studied at S/C ratio of 4.84 and 700 °C, to verify the activity, selectivity and stability of the catalysts. Ethanol conversion reached 100% and catalysts were very stable for almost 50 h on stream. No significant differences were detected in both catalysts. Nevertheless, TPO experiments performed on used samples demonstrate a higher carbon production on nickel based catalyst that can be correlated to ethanol dehydration contribution on it reaction pathway.
