Acidity, catalytic activity, and deactivation of H-gallosilicate (MFI) in propane aromatization: Influence of hydrothermal pretreatments

Journal Article · Thu Feb 01 04:00:00 EST 1996 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1996.0052· OSTI ID:263706

Choudhar, V R; Kinage, A K; Sivadinarayana, C; Devadas, P ^[1]

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1. National Chemical Lab., Pune (India); and others

Effect of various hydrothermal pretreatments [at different temperatures (400-800{degrees}C) and concentrations of steam (13-80 mol%) or with liquid water at 150{degrees}C under autogenous pressure] to H-gallosilicate (MFI) zeolite (bulk Si/Ga = 33 and Na/Ga = 0.1) on its acidity/acid strength distribution (determined by chemisorption and step-wise thermal desorption of pyridine from 100-400{degrees}C), acid function (studied by acid catalyzed model reactions viz. isooctane cracking for external acidity and o-xylene isomerization and toluene disproportionation for internal or intracrystalline acidity), and deactivation due to coking in propane aromatization (at 550{degrees} and time-on-stream of 8.5 {+-} 0.5) has been thoroughly investigated. With the increase in the severity of hydrothermal treatment to the zeolite, its crystallinity, framework (FW) Ga (observed by {sup 71}Ga and {sup 29}Si MAS NMR and FTIR), acidity (measured in terms of the pyridine chemisorbed at 400{degrees}C and activity in the model reactions), and catalytic activity in the propane aromatization are decreased, but its deactivation due to coking and shape selectivity are increased appreciably. These effects are attributed to the extensive degalliation of the zeolite due its hydrothermal treatments. Its product selectivity, dehydrogenation/cracking (D/C) activity ratio, and aromatics/(methane + ethane) mass ratio in the propane aromatization are also influenced by its hydrothermal treatments, depending upon the conversion. 25 refs., 18 figs., 3 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 263706
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 158; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
40 CHEMISTRY
AROMATIZATION
CATALYSTS
CATALYTIC CRACKING
CATALYTIC EFFECTS
CHEMISORPTION
COKING
DEHYDROGENATION
GALLIUM COMPOUNDS
HYDROTHERMAL SYNTHESIS
ISOMERIZATION
NUCLEAR MAGNETIC RESONANCE
OCTANE
OXIDATION
PH VALUE
PROPANE
PYRIDINE
REDUCTION
SILICATES
SORPTIVE PROPERTIES
TOLUENE
XYLENES
ZEOLITES