Abs~a~In comparison with zenlites, a variety of AI pillared clays did not prove as promising cracking catalysts, possibly because their Br6nsted sites are hidden. In the less demanding double bond shift isomerization, both catalyst types were comparable probably due to the presence of Lewis sites on both catalysts.
The changes of adsorption properties of uncalcined Al-pillared montmorillonite were studied. A soda-activated bentonite from Slovakia was reacted with polymeric hydroxoaluminium salt solutions. During storagein air at room temperature for three years, the basal spacing decreased by 0.15–0.2 nm; the specific surface area was reduced by 80% and the total pore volume by 40–60%. Adsorption experiments from ethanol-cyclohexane mixtures revealed the decreasing adsorption capacity and the increasing hydrophobicity. The changing surface character was also evident in the decrease in enthalpy of immersion in ethanol from 65.3 J/g to 8.3 J/g (sample B) and from 37.8 J/g to 5.2 J/g (sample C). The alteration probably arises from gradual formation of gibbsite-like interlayers and the redistribution of charges.
Der Einbau der Kationen [AlO4Al12(OH)24(H2O)12]7+ (Al13) und [GaO4Al12(OH)24(H2O)12]7+ (GaAl12) in Smectite führt im Gegensatz zum [GeO4Al12(OH)24(H2O)12]8+ (GeAl12) zur pillared clay‐Bildung. Mittels der Ferronmethode werden die Ursachen für dieses unterschiedliche Verhalten untersucht. Das Al13‐Kation ist während des pillaring‐Prozesses als stabil anzusehen. Beim GeAl12 erfolgt nach Protolyse eine Umwandlung in polymere Kationen unbekannter struktur, die nicht zur pillared clay‐Bildung befähigt sind. Das Phänomen der Bildung polymerer Species tritt beim GaAl12 nur im geringen Umfang auf und hat keine Auswirkungen auf die Produktbildung.
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