Modified zeolites. Part 2.—Sorption by dealuminated, silanated mordenites

Abstract

A comparison has been made of sorption isotherms and kinetics of O₂, N₂ and Ar in each of a series of partially dealuminated mordenites before and after different extents of silanation. Before silanation partially dealuminated mordenites sorbed each gas freely but after silanation some very selective sorbents were obtained which at 77 K imbibed O₂ much more copiously than either N₂ or Ar. This selectivity was further improved when acidic H was replaced by Na in the dealuminated H-mordenites before silanation. In many of the sorbents a rapid initial uptake was followed by a slow diffusion at rates in the sequence O₂ > N₂ > Ar, which is the inverse order of their van der Waals cross-sectional diameters. The results provide evidence that after silanation the intracrystalline channels are not uniformly accessible to a given sorbate.