The synthesis and cracking behavior of zeolite-amorphous silica-alumina composites prepared using gels with high alumina and low organic template content

Journal Article · Wed Jan 01 00:00:00 EST 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90184-J· OSTI ID:7241369

Yarlagadda, P; Lund, C R.F.; Ruckenstein, E ^[1]

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1. State Univ. of New York at Buffalo, Amherst, NY (United States)

Composites of ZSM-5 and amorphous silica-alumina have been prepared from starting gels with SiO{sub 2}/Al{sub 2}O{sub 3} molar ratios (S/A) of 10 and below and tetrapropyl ammonium (TPA)/Al{sub 2}O{sub 3} molar ratios (T/A) below 0.5. The syntheses have been followed by periodic removal of aliquots from the gel with subsequent analysis. At S/A = 10 and T/A = 0.44 mordenite formed. When the S/A ratio was reduced to 8.3, but the ratio T/A was kept at 0.45, crystallization progressed from the initial formation of P{sub c} to a mixture of P{sub c} plus ZSM-5 to finally only ZSM-5 at the end of the run. At the lower S/A ratio of 6 the P{sub c} phase persisted, in a mixture with ZSM-5, until the end of the run. At the lowest S/A ratio employed, 3.5, only P{sub c} was detected for a T/A ratio of 0.4. In all cases an amorphous silica-alumina coexisted with the zeolites. Samples were calcined and subsequently converted to the H{sup +} form of ZSM-5 and evaluated in the cracking of n-hexane. These catalysts were more active than either pure HAIZSM-5 or mechanical mixtures prepared by the addition of preformed ZSM-5 powder to an amorphous silica-alumina gel. All catalysts examined did show comparable selectivity to C6{sub 6}-C{sub 10} aromatics when compared at equal conversions. Both types of catalysts, namely those crystallized in situ and those prepared mechanically, had comparable numbers of strong acid sites as measured by the temperature-programmed desorption of ammonia.

• OSTI ID: 7241369
• Journal Information: Journal of Catalysis; (United States), Vol. 133:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
02 PETROLEUM
36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CATALYTIC EFFECTS
SYNTHESIS
COMPOSITE MATERIALS
HEXANE
CATALYTIC CRACKING
SILICON OXIDES
ZEOLITES
PHASE STUDIES
AMMONIA
AMORPHOUS STATE
AROMATICS
CATALYSTS
DESORPTION
GELS
HYDROCRACKING
MORDENITE
STOICHIOMETRY
TEMPERATURE CONTROL
ALKANES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COLLOIDS
CONTROL
CRACKING
DECOMPOSITION
DISPERSIONS
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MINERALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
SILICATE MINERALS
SILICON COMPOUNDS
SORPTION
THERMOCHEMICAL PROCESSES
400201* - Chemical & Physicochemical Properties
020400 - Petroleum- Processing
360602 - Other Materials- Structure & Phase Studies