A MICROCALORIMETRIC COMPARISON OF THE EFFECT OF N-ALKANE PREADSORPTION ON THE ADSORPTION OF ARGON AND NITROGEN ON SILICALITE-I

The n-alkanes of different lengths were preadsorbed to selectively blo ck part of the micropores of a MFI-type zeolite, Silicalite-I. The por osity available to argon and nitrogen was then studied by quasi-equili brium adsorption microcalorimetry and volumetry at 77 K and compared t o what was found for the bare zeolite. Indeed, although partial adsorp tion of n-alkanes does not alter the value of the differential enthalp ies of adsorption for both argon and nitrogen, the n-butane preadsorpt ion diminishes the adsorption capacity by inducing inaccessible volume s in the micropore network. Moreover, the microcalorimetric experiment s clearly show that n-butane is not evenly distributed in the zeolite channel network while the longer n-alkanes used are.