The inactivity of extra framework aluminum in the cracking of 2,3-dimethylbutane on USHY

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1994.1342· OSTI ID:47970

Bamwenda, G R; Zhao, Y X; Wojciechowski, B W ^[1]

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1. Queen`s Univ., Kingston, Ontario (Canada)

Activity and selectivity in the cracking of 2,3-dimethylbutane on steam-stabilized ultrastable HY (USHY), and on the same steamed USHY after extraction using (NH{sub 4}){sub 2} SiF{sub 6}, have been studied at 400{degrees}C. Based on the data presented here, a detailed mechanism is proposed for the cracking of 2,3-dimethylbutane on the two catalysts. The mechanism accounts for the kinetics and the selectivity behavior observed and shows that extra-framework aluminum (EFAI) does not participate in the cracking of 2,3-dimethylbutane under these experimental conditions. Kinetic parameters obtained from the fit of experimental conversion data, and the initial product selectivities, show that monomolecular and bimolecular reactions are active on both catalysts. These quantitative measures show that extraction of EFAI from the steamed catalyst result in a small increase in the total initial rate of reaction. The authors take this to indicate that new sites are activated by the removal of the EFAI. At the same time, product species are more strongly adsorbed on the extracted catalyst. As a result, a small increase in the rate of catalyst decay was noted on the extracted catalyst. The increase in initial rate of conversion is therefore negated at longer times on stream by the increase in the rate of catalyst decay. Selectivity data show that bimolecular reactions involving carbenium ions and feed molecules are dominant on both catalysts. No significant change in product distribution was observed upon removal of the extraframework aluminum. It was concluded that the extraction of the EFAI increases the number of available sites without changing their acidity distribution. Such behavior would be expected if the role of the EFAI is one involving purely mechanical blocking of feed accessibility to a random selection of active sites. 27 refs., 6 figs., 5 tabs.

• OSTI ID: 47970
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 150; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
40 CHEMISTRY
ALKANES
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CRACKING
ZEOLITES