Differences in Structural, Textural, and Catalytic Properties of Montmorillonite Pillared with (GaAl₁₂) and (AlAl₁₂) Polyoxycations

Abstract

This paper reports the preparation of a pillared montmorillonite using the mixed oligomer [GaO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ . Pillaring was performed with a starting solution having a molar ratio of Al 3+ /Ga 3+) 12, which is equivalent to the stoichiometric ratio of this polyoxycation. To determine the optimum conditions for obtaining the desired product, we varied the OH -/ (Al 3+ + Ga 3+ ) molar ratio in the range 1.5-2.5, which also produced variations in the pH of the oligomeric solution. The most favorable conditions were found to be OH -/(Al 3+ + Ga 3+ ) ) 2.0 and pH ) 3.7. The presence of mixed polyoxycations in the pillars of the synthesized materials was confirmed by NMR studies. The thermal stability and catalytic behavior of these materials in the hydrocracking and hydroisomerization of n-heptane have been compared with those of the material obtained from the same montmorillonite by pillaring with the [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ polyoxycation. The structure of the material pillared with the mixed polyoxycation shows higher thermal stability and retains 65% of its generated microporosity, up to 700 °C. This material also has greater stability in the number and strength of the Lewis acid sites of its pillars, resulting in higher selectivity for the isomerization of n-heptane.

From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis

“…The possibility of making bifunctional Pt/PLS catalysts has been illustrated by using test reactions such as the hydroisomerization and hydrocracking of n-alkanes. [118][119][120][121][122][123][124] These studies, in general, showed that there is a direct correlation between the Brøn-sted acidity of the PLS and the hydroisomerization/ hydrocracking activity, and furthermore it is possible to achieve on these materials a good balance between hydrogenation-dehydrogenation and the cracking functions.…”

Density functional theory of adsorption in pillared slit-like pores

“…In recent years a number of researchers have investigated adsorption in synthetic pillared clays [1][2][3][4][5][6]. The synthesis of pillared clays was originally suggested by Barrer and McLeod [7], who inserted specific molecules into clay minerals to prop apart the aluminosilicate sheets, thereby producing larger pores than those found in natural clays.…”

Sintesis Lempung Terpilar Polikation Alumunium Sebagai Adsorben Indigo Karmina

“…Lempung terpilar Al mempunyai stabilitas termal yang cukup tinggi mencapai suhu 700°C [6]. Jarak antar lapis yang dihasilkan berkisar antara 12-18 Å yang dipengaruhi oleh kondisi sintesisnya [5].…”

“…Kemungkinan lain yakni terjadi kerusakan pilar alumina oksida akibat kenaikan suhu. Hal ini didukung oleh penelitian [6,8] yang juga menghasilkan difraktogram yang menurun dengan kenaikan suhu yang menunjukkan bahwa pilar Al menurun dengan kenaikan suhu.…”