Conformation of intrazeolitic choline ions and the framework topology of zeolite hosts

Abstract

A close relationship between the conformation of choline and the structure type of zeolites crystallized using this organic species was found.

A Cooperative OSDA Blueprint for Highly Siliceous Faujasite Zeolite Catalysts with Enhanced Acidity Accessibility

“…O nt he contrary,asingle magnetic environment was observed in FAU-S4, which may reflect certain mobility of trans and gauche Ch + in its sod cage and supercage, respectively (see later). 29 Si MAS NMR spectra in Figure 1B primarily include five resolved signals,n amely Si(0Al…”

“…[25][26][27][28] Hong et al further verified, with Raman spectroscopy,t he coexistence of two Ch + types within different zeolites,n amely gauche and trans conformer (Figure S1). [29] In terms of FAU topology,specifically,asmall fraction of trans Ch + conformer (8 %) has been detected in the sod cage in addition to the predominant occupancyo fgauche conformer in the supercage (Entry 5, Table S1). [29] In contrast, as ac onventional OSDAf or medium high-silica FAUs ynthesis (Si/Al = 4.5), CE was found to locate in supercages only,i nt he form of ac ationic complex with Na + (entry 10, Table S1).…”

A Cooperative OSDA Blueprint for Highly Siliceous Faujasite Zeolite Catalysts with Enhanced Acidity Accessibility

“…Chemie supercage.O nt he contrary,asingle magnetic environment was observed in FAU-S4, which may reflect certain mobility of trans and gauche Ch + in its sod cage and supercage, respectively (see later). 29 Si MAS NMR spectra in Figure 1B primarily include five resolved signals,n amely Si(0Al…”

Phase Transformation Behavior of a Two‐Dimensional Zeolite

“…[2] As shown in Figure 2a,o nt he other hand, PST-9, obtained after 2days of heating at 150 8 8Cinthe choline-Rb + -Na + mixed-SDAsystem, is completely transformed to EU-12 when heated for additional 5days in the crystallization medium. [12] However,ascorroborated by the relative intensities of the two Raman bands around 710 and 760 cm À1 ,s hown in Figure 2b,f rom the symmetric CÀNs tretching mode (n s (CÀ N)) of gauche and trans choline conformers,r espectively, [12a] the gauche/trans conformer ratio in solid products separated during PST-9/EU-12 synthesis at 150 8 8Cr apidly decreases with increasing crystallization time to 2days,t hat is,u ntil PST-9 fully crystallizes.This can be rationalized by taking into account the narrow 8-ring channels of PST-9 within which the trans conformer, thinner than the gauche conformer, may be easily encapsulated. This asymmetric quaternary ammonium cation is known to exist primarily as a gauche conformer in the solid, liquid and gas phases, because of the stabilization by non-specific,e lectrostatic interactions between the electronegative oxygen atom of the OH group and the positive charge distributed over its head [(CH 3 ) 3 N + CH 2 ]group.…”

“…This asymmetric quaternary ammonium cation is known to exist primarily as a gauche conformer in the solid, liquid and gas phases, because of the stabilization by non-specific,e lectrostatic interactions between the electronegative oxygen atom of the OH group and the positive charge distributed over its head [(CH 3 ) 3 N + CH 2 ]group. [12] However,ascorroborated by the relative intensities of the two Raman bands around 710 and 760 cm À1 ,s hown in Figure 2b,f rom the symmetric CÀNs tretching mode (n s (CÀ N)) of gauche and trans choline conformers,r espectively, [12a] the gauche/trans conformer ratio in solid products separated during PST-9/EU-12 synthesis at 150 8 8Cr apidly decreases with increasing crystallization time to 2days,t hat is,u ntil PST-9 fully crystallizes.This can be rationalized by taking into account the narrow 8-ring channels of PST-9 within which the trans conformer, thinner than the gauche conformer, may be easily encapsulated. It is also remarkable that repeated K + ion exchange of ChRbNa-PST-9 led to ad isappearance of the n s (C À N) band around 710 cm À1 ( Figure S9).…”