Evidence of Bronsted acidity on sulfided promoted and unpromoted Mo/Al sub 2 O sub 3 catalysts

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90151-6· OSTI ID:6843766

Topsoe, N Y; Topsoe, H ^[1]; Massoth, F E ^[2]

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1. Haldor Topsoe Research Laboratories, Lyngby (Denmark)
2. Univ. of Utah, Salt Lake City (USA)

It is uncertain what effect acidity, especially protonic (Bronsted) acidity, has on typical hydrotreating reactions over molybdenum-containing, sulfided catalysts. In a study of the hydrogenation of 1-hexene, small amounts of propylene were found together with the major product, hexane. The amount of the former increased with increase in the H{sub 2}S partial pressure, leading to the supposition that H{sub 2}S increased the Bronsted acidity of the sulfided catalyst. The hydrodenitrogenation of quinoline was also found to be promoted by H{sub 2}S, which was attributed to an increase in the number of Bronsted acid sites. However, no direct evidence for the presence of Bronsted acid sites was obtained. One of the advantages of using pyridine as the probe molecule for monitoring acidity is that it can adsorb both as coordinated and protonated pyridine on Lewis and Bronsted acid sites, respectively. These adsorbed pyridine species can be easily distinguished by infrared spectroscopy. Bronsted and Lewis acid sites have been detected for oxidic promoted and unpromoted Mo/Al{sub 2}/O{sub 3} catalysts but only Lewis acidity has been found on the corresponding sulfided catalysts. It should be pointed out that most of the previous IR studies have been carried out with pyridine adsorption at relatively low temperatures (below 423 K). It occurred to the authors that since the Bronsted acidity, if it exists, must be weak, higher temperatures may be required to produce the pyridinium ion. The present not reports IR evidence of Bronsted acidity at elevated temperatures corresponding to those typically employed under hydroprocessing reactions.

• OSTI ID: 6843766
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 119:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AZINES
CALCINATION
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
COBALT
DECOMPOSITION
ELEMENTS
HETEROCYCLIC COMPOUNDS
HYDROGENATION
IMPREGNATION
INFRARED SPECTRA
METALS
MOLYBDENUM COMPOUNDS
MOLYBDENUM SULFIDES
NICKEL
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROMOTERS
PYRIDINE
PYRIDINES
PYROLYSIS
REFRACTORY METAL COMPOUNDS
SAMPLE PREPARATION
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SULFIDES
SULFUR COMPOUNDS
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS