Phase Transformations in Alkaline and Acid Leached Y Zeolites Dealuminated by Steaming

Abstract

The steaming of zeolite Y (here at 873 K for 7 hours) leads to the formation of an amorphous aluminium aluminosilicate in addition to the dealuminated zeolite (DAY). An alkaline treatment of DAY causes the transformation of the non‐framework phase into an alkali aluminosilicate and the partial desilication of the DAY framework. The alkali aluminosilicate is decomposed by a moderate acid leaching under the formation of silica gel. The 29Si MAS NMR and IR spectra of DAY and its chemically treated modifications are superimposed by the signals of the crystalline zeolite framework and the amorphous non‐framework materials whereas XRD measurements only characterize the current state of the framework.

Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited

“…The occurrence of extraframework silica-gel is the reason why Si/Al ratios calculated in DAY samples with TOT mode (4) and NMR data (5) (see italics in Table 1) appear to be principally too high. Both IR and NMR signals are strongly superimposed by contributions of those characteristic of Si(0Al) and Si(1Al) species [85][86][87].…”

Hierarchization of USY Zeolite by NH4OH. A Postsynthetic Process Investigated by NMR and XRD

“…34−40 XRD quantifies the fraction of the materials exhibiting Bragg crystallinity, while 29 Si magic angle spinning (MAS) NMR detects crystalline as well as amorphous nonframework material. 41 Recently, the creation of silanol nests and hydroxyl nets associated with Al−OH in the framework of Y zeolite after alkaline treatment has been observed by using 27 Al{ 1 H} transfer of populations in double resonance (TRAPDOR) experiments. 42 Moreover, healing of hydroxyl nests as a consequence of realumination during the treatment was proven by various NMR studies, 42−44 although Lutz et al did not observe a reinsertion of extraframework Al into the zeolite framework.…”

“…Such understanding could lead to improved postsynthesis treatments targeting the desired properties of the transformed materials. Solid-state nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) are well-established tools for the characterization of zeolites and zeotype materials. − XRD quantifies the fraction of the materials exhibiting Bragg crystallinity, while 29 Si magic angle spinning (MAS) NMR detects crystalline as well as amorphous nonframework material . Recently, the creation of silanol nests and hydroxyl nets associated with Al–OH in the framework of Y zeolite after alkaline treatment has been observed by using 27 Al{ 1 H} transfer of populations in double resonance (TRAPDOR) experiments .…”

Fabrication of SAPO‐34 with Tuned Mesopore Structure

“…In this case, combinational characteristics of different pore regimes improve the diffusion of molecules and enhance stability of material. Several approaches like demetalation including element extraction from zeolite framework,5 endo or exo‐soft and hard templating,6 carbon employment7 through space confined synthesis and templating methods have been proposed.…”

“…[3,4] In this case, combinational characteristics of different pore regimes improve the diffusion of molecules and enhance stability of material. Several approaches like demetalation including element extraction from zeolite framework, [5] endo or exo-soft and hard templating, [6] carbon employment [7] through space confined synthesis and templating methods have been proposed. hibiting (CGI) effect but also modified the morphology of the crystals and improved CSD (crystal size distribution) along with induction of mesopores into the porous structure.…”