Platinum clusters supported in zeolite LTL: Influence of catalyst morphology on performance in n-hexane reforming

Journal Article · Sun Oct 25 04:00:00 EST 1998 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2229· OSTI ID:289434

Jentoft, R E; Gates, B C ^[1]; Tsapatsis, M ^[2]; Davis, M E ^[3]

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1. Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science
2. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemical Engineering
3. California Inst. of Tech., Pasadena, CA (United States)

KLTL zeolite-supported platinum catalysts were synthesized from aqueous tetraammineplatinum(II) nitrate solutions and nonacidic KLTL zeolite crystallites, including some with dimensions as little as 300 x 500 {angstrom}. The zeolite crystallites had various morphologies, some being predominantly disk-shaped particles and some predominantly mosaics of rod-like domains with a range of c-dimension lengths. The activity and selectivity of each catalyst were evaluated for dehydrocyclization of n-hexane in the presence of H{sub 2} to form predominantly benzene at conversions of typically 45--90%. The data presented here provide a detailed characterization of the deactivation of such catalysts in the absence of sulfur. EXAFS data show that the platinum in each catalyst was present in clusters of about 20 atoms each, on average. Electron micrographs show that the platinum clusters were nearly evenly dispersed on the surfaces of the zeolite crystallites, including the intracrystalline and extracrystalline surfaces. The catalytic performance was virtually independent of the zeolite channel length, but activity, selectivity, and resistance to deactivation were found to be correlated with the ratio of the surface area external to the crystallite domains to that within the intracrystalline pores. The catalyst performance is dependent on this ratio (which is related to the zeolite morphology) as follows: in comparison with the others, the catalysts with the relatively low fractions of platinum outside the intracrystalline pores are more active, more selective for benzene formation, and more resistant to deactivation.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-87ER13790; FG02-89ER45384; AC02-76CH00016
• OSTI ID: 289434
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 179; ISSN JCTLA5; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
BENZENE
CATALYSTS
CATALYTIC EFFECTS
DEACTIVATION
DEHYDROCYCLIZATION
HEXANE
MORPHOLOGY
PLATINUM
PORE STRUCTURE
SYNTHESIS