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The environment provided by the zeolite channels has been examined in high-silica zeolites having the MFI (ZSM-5), CHA (Chabazite), MOR (Mordenite), TON (ZSM-22), MTW (ZSM-12), FER (Ferrierite), and FAU (Faujasite) structures. Calorimetric measurements of CH 4 and O 2 at ∼210 K showed that structure affects the adsorption properties in a manner which depends on the pore dimensions. The differential heats for CH 4 at low coverage were 28 kJ/mol in FER, 27 kJ/mol in TON, 25 kJ/mol in MOR, 21 kJ/mol in MFI, 20.5 kJ/mol in MTW, 19.5 kJ/mol in CHA, and 14 kJ/mol in FAU. However, calorimetric data for acetonitrile in the acidic forms of these zeolites gave heats that were independent of structure within experimental error, with differential heats for the 1:1 adsorption complexes all being 100 ( 10 kJ/mol. A possible explanation lies in the additional orientation-dependent interaction resulting from the hydrogen bonding. These topology-sensitive, orientational interactions are observable in the temperature-sensitive, methyl-proton, NMR line shapes, where it is found that the barriers to reorientation of 1:1 adsorption complexes are much higher in small-pore zeolites. The implications of these measurements to "confinement" effects in catalysis are discussed.

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The adsorption and reaction properties of an Al-free H-[Fe]ZSM-5 were examined and compared to an H-[Al]ZSM-5 sample with the same site density. H-[Fe]ZSM-5 was shown to have Brønsted-acid sites in a concentration equal to the framework Fe concentration. Differential heats of adsorption for ammonia and pyridine were shown to be identical to that obtained in H-[Al]ZSM-5, with differential heats of ~150 kJ/mol for ammonia and 200 kJ/mol for pyridine. For H-[Al]ZSM-5, adsorption of either propylene or 1-butene at room temperature results in rapid oligomerization. TPD-TGA measurements of the oligomers in H-[Al]ZSM-5 show evidence for hydride-transfer reactions, in addition to simple oligomer cracking. By contrast, it is necessary to heat H-[Fe]ZSM-5 to 370 K for rapid oligomerization of propylene and oligomerization of 1-butene occurs only slowly at 295 K. TPD-TGA measurements of the oligomers in H-[Fe]ZSM-5 show no evidence for hydride-transfer reactions and H-[Fe]ZSM-5 forms much less coke than H-[Al]ZSM-5 during steady-state reaction in 1-butene at 573 K. Adsorption measurements of 1-butene on D-[Fe]ZSM-5 suggest that the protonated complexes of 1-butene are formed but that these are relatively stable towards reaction, implying that the carbocation transition states are relatively unstable. Comments

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