| Abstract
| - Microcalorimetric measurements were performed at 195 K for CO and N2 on zeolite H−MFI and on a siliceousMFI in order to characterize the interaction of these molecules with the Brønsted acid sites. On the siliceousMFI, the differential enthalpies of adsorption (isosteric heats) for CO and N2 were found to be essentiallyconstant with coverage at a value of 16 ± 1 kJ/mol. While the isosteric heats for N2 were slightly higher onH−MFI at coverages below one per site, the additional interaction with the Brønsted sites is less than 3kJ/mol. For CO on H−MFI, microcalorimetry provides evidence for a 1:1 adsorption complex with the acidsites in that the isosteric heats are higher on H−MFI at low coverages and approach the values for the siliceousmaterial at higher coverages. Because the calorimetric data can be fit to a two-site, Langmuir model in whichthe hydrogen-bonded CO interacts with an additional 10.5 kJ/mol, the results suggest that the Brønsted acidsites in H−MFI are essentially identical in regard to how they interact with CO.
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