Browsing by Author "Trombe, Jean-Christian"

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    Modified Zeolites Part 1.—Dealuminated Mordenites and their Silanation
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Barrer, Richard M.; Trombe, Jean-Christian
    A series of partially dealuminated H-mordenites having different ratios SiO2/Al2O3 has been prepared from Na-mordenite by various treatments with acid. From these a series of dealuminated Na-mordenites has been made by treating the corresponding H-mordenites with dilute NaOH. The loss of water, including that from the groups [graphic omitted] and the “nests” of hydroxyls, H4O4, has been investigated as a function of temperature for the dealuminated forms. This showed at 360°C the existence of some OH groups not originating from [graphic omitted]. Such groups were attributed to —OH originating from nests. The silanation of the dealuminated H- and Na-mordenites was investigated quantitatively. In the mordenites free of zeolitic water the ratios H2(evolved)/SiH4(chemisorbed) were always between 1.5 and 2 and each ratio usually remained reasonably constant over the course of a run. This suggested a rather constant ratio of primary chemisorption to secondary reaction during many runs. The ratio increased above 2 only if zeolitic water was also present. No evidence was found for a significant amount of the reaction [graphic omitted] in which SiH4 interacts with intact “nests”, H4O4, to regenerate defect-free framework. The Elovich equation appeared able to represent the kinetics of chemisorption of SiH4.
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    Modified zeolites. Part 2.—Sorption by dealuminated, silanated mordenites
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Barrer, Richard M.; Trombe, Jean-Christian
    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.