Stoichiometric adsorption complexes in H-ZSM-5, H-ZSM-12, and H-mordenite zeolites

Journal Article · Sat Dec 31 23:00:00 EST 1988 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90027-4· OSTI ID:6945196

Kofke, T J.G.; Gorte, R J; Kokotailo, G T ^[1]; Farneth, W E ^[2]

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1. Univ. of Pennsylvania, Philadelphia (USA)
2. E.I. duPont de Nemours and Company, Wilmington, DE (USA)

In order to understand the chemical properties of acid sites in zeolites, the authors have been examining the adsorption of simple molecules which can undergo classical acid-catalyzed chemistry in high-silica H-ZSM-5. For many molecules, including a series of alcohols, toluene, 2-propanamine, and 2-propanone, the authors have found that, following adsorption and evacuation, a well-defined adsorption complex corresponding to one molecule per Al site could be obtained. Furthermore, the unimolecular reactivities of the molecules in these 1 : 1 adsorption complexes were consistent with solution-phase, Bronsted acid-catalyzed chemistry and were unaffected by the Al concentration for SiO{sub 2}/Al{sub 2}O{sub 3} ratios from 38 to 520. These results imply that the active acid sites in H-ZSM-5 are identical and are present in a concentration of one/Al atom. This is consistent with conclusions reached from n-hexane cracking studies on H-ZSM-5. In order to examine the effect of solid-state structure on these acid sites, the authors extended their previous work to two other zeolites. H-ZSM-12 and H-mordenite. The adsorption of 2-propanol and 2-propanamine were chosen for study since the 1 : 1 complexes formed by these two molecules were the most distinctive in our previous adsorption studies. The authors show in this paper that 2-propanol and 2-propanamine also form clearly defined, 1 : 1 adsorption complexes with the Al site in H-ZSM-12 and H-mordenite. The reactivity of these adsorption complexes is identical to the reactivity of the 1 : 1 adsorption complexes formed by these molecules in H-ZSM-5. The complexes decompose at the same temperatures and form the same products on all three zeolites. This is strong evidence that the acid sites formed by isolated Al atoms in a zeolite lattice are chemically equivalent, independent of the structure of the lattice.

• OSTI ID: 6945196
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 115:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALCOHOLS
ALKANES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AMINES
CATALYTIC CRACKING
CHALCOGENIDES
CHEMICAL PROPERTIES
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
COMPLEXES
CRACKING
CRYSTAL STRUCTURE
DECOMPOSITION
HEXANE
HYDROCARBONS
HYDROXY COMPOUNDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MICROSTRUCTURE
MINERALS
MORDENITE
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PROPANOLS
PYROLYSIS
SILICA
SILICATE MINERALS
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SORPTIVE PROPERTIES
STOICHIOMETRY
SURFACE PROPERTIES
SYNTHESIS
THERMOCHEMICAL PROCESSES
ZEOLITES