NiMoS/{gamma}-Al{sub 2}O{sub 3} catalysts: The nature and the aging behavior of active sites in HDN reactions

Journal Article · Thu Sep 10 04:00:00 EDT 1998 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2160· OSTI ID:659087

Zhang, L; Karakas, G; Ozkan, U S ^[1]

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1. Ohio State Univ., Columbus, OH (United States). Dept. of Chemical Engineering

The work presented in this paper is a continuation of earlier work aimed at acquiring a fundamental understanding of sulfided Ni-Mo/{gamma}-Al{sub 2}O{sub 3} catalysts in HDN catalysis. A series of temperature-programmed desorption and reduction experiments were performed over in-situ sulfided bare {gamma}-alumina support, alumina-supported monometallic Ni, Mo, and bimetallic NiMo catalysts. The TPD and TPR results were linked to the active site assignment of Ni- and Mo-associated centers in HDN reactions. Postreaction XPS and SEM characterizations were performed for catalysts used in HDN for up to 1000 h. One of the major changes during the aging of the Ni-Mo/{gamma}-Al{sub 2}O{sub 3} catalysts was the loss of some active sites associated with the Ni promoters. The decreased Ni content over the catalyst surface was consistent with the observed decrease in the hydrogenation function of the catalyst. Two possible mechanisms are suggested for the loss of Ni active sites. One is coking that spreads from the alumina support to the nickel sites. Another is segregation of some Ni atoms from the Ni-Mo-S structure due to loss of structural sulfur.

• OSTI ID: 659087
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 178; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
02 PETROLEUM
AGING
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
DENITRIFICATION
HYDROGENATION
MOLYBDENUM SULFIDES
NICKEL SULFIDES