DETERMINATION OF SILICON-ALUMINIUM ORDERINGS IN MORDENITE AND ITS ALUMINIUM DEFICIENT FORMS USING HIGH-RESOLUTION MAGIC-ANGLE-SPINNING 29Si-NMR

Abstract

A series of chemically dealuminated mordenites were investigated by 29Si and 27Al NMR spectroscopy. High-resolution magic-angle-spinning (HRMAS) solid state 29Si NMR lines with varying intensity were observed at δ=−95, −105 and −110 ppm. When it is assumed that the Al atoms are located exclusively in the 4-membered rings of the structure, these variations can be explained by assigning the resonance lines to silicon atoms surrounded by 2, 1 and 0 Al atoms respectively. The 27Al NMR spectrum yields quantitative information on the amount of octahedrally coordinated aluminium formed during various chemical treatments of Na-mordenite.

Understanding Aluminum Location and Non-framework Ions Effects on Alkane Adsorption in Aluminosilicates: A Molecular Simulation Study

“…60 In this structure the eight Al atoms are located in the 4-rings, in complete conformity with the suggested preferential sitting of aluminum provided by previous crystallographic, experimental, and theoretical work. 43,44,[62][63][64][65] To study the effects of the cations on the adsorption behavior, we checked the snapshot of this structure with adsorbed methane at 323 K and 1 kPa, and compared with the adsorption in pure silica structure. The results are shown in Figure 8.…”

Hypothetical Structures of Magadiite and Sodium Octosilicate and Structural Relationships Between the Layered Alkali Metal Silicates and the Mordenite- and Pentasil-Group Zeolites

“…The formation of defect sites in the mordenite and pentasil structures appears to be related to the presence of internal silanol sites within the crystals of these materials (Debras et al, 1983;Nagy et aL, 1982). The proposed blocks shown in Figure 4C can be generated from the type-B blocks present in the idealized structure of ZSM-5 (Jansen et aL, 1984) by the addition of Si2Os(ONa)2 units, as shown in Figures 4B and 4C.…”

A Computational Method To Characterize Framework Aluminum in Aluminosilicates

“…Methane shows the highest adsorption in structure 16 (Al atoms replace Si4, Si18, Si31, Si42, Si80, Si93, Si105, and Si115), and the lowest for structure 6 (Al atoms replace Si3, Si18, Si32, Si42, Si79, Si93, Si106, and Si115). [16,19,[31][32][33][34] The method is transferable to other protonated aluminosilicate structures, as shown in Figures 3 and 4 for H-FERand H-TON-type zeolites, respectively. In this structure the eight Al atoms are located in the 4-rings, in complete conformity with the suggested preferential sites of aluminum provided by previous crystallographic, experimental, and theoretical work.…”