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

Journal Article · Sun Jan 01 00:00:00 EST 1989 · 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), Vol. 115:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

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