29Si-NMR-Untersuchungen zur Anionenstruktur von Kristallinen Tetramethylammonium-alumosilicaten und -alumosilicatlösungen

²⁹Si NMR Investigations on the Anion Structure of Crystalline Tetramethylammoniumaluminosilicates and -aluminosilicate Solutions The ²⁹Si NMR spectra of crystalline tetramethylammonium (TMA) aluminosilicates with different Si/Al ratios exhibit up to 4 sharp signals with characteristic chemical shifts which can be assigned to the central Si atom of OSi(OSi)_3?n(OAl)_n building units of double four-ring (DFR) aluminosilicate anions. The number and distributions of the Al atoms in the DFR framework can be derived from the signal intensities in connection with the results of the trimethylsilylation method [1]. A good agreement of the results of both methods has been found. The DFR can exist as monomeric unit or can be connected to polymeric structures by SiOAl bridges, but no information can be obtained about this question by the ²⁹Si NMR spectra. The investigation of the TMA aluminosilicate solutions by ²⁹Si NMR and TMS method [1] show that stable aluminosilicate anions exist in these solutions. The structure of these aluminosilicate anions is different from the structure of the crystalline TMA aluminosilicates obtained from the solutions.     

Aluminum-27 NMR studies of alcoholic (2-hydroxyethyl)trimethylammonium aluminate solutions

²⁷Al NMR spectroscopy is a power tool for investigation of the aluminate species existing in both aqueous and non-aqueous solutions. Aluminum-27 nuclear magnetic resonance (NMR) spectroscopy also can be used to determine thermodynamic properties of complexes in the solution. In this report, ²⁷Al NMR spectroscopy was used to characterize species present in alkaline alcoholic aluminate solutions. (2-Hydroxyethyl)trimethylammonium (2-EHTMA) hydroxide was used as base. In solution of CH₃OH and H₂O in a mole ratio of 64:1 it was possible to detect five signals by aluminum-27 NMR, indicating formation of [Al(OH)_4−n(CH₃OH)_n]⁽ⁿ⁻¹⁾⁺ (n = 0,1, 2, 3 and 4) species. Aluminum-27 NMR spectroscopy has also used for investigation of the species present in the ethanolic 2-HETMA aluminate solutions. The equilibrium constants for the formation of aluminate complexes were also determined for both methanolic and ethanolic aluminate solutions. Aluminum-27 NMR spectra of propanolic and butanolic 2-HETMA aluminate solutions were also studied.     

29Si-NMR-Untersuchungen zur Verteilung der Silicium-und Aluminiumatome im Alumosilicatgitter von Zeolithen mit Faujasit-Struktur

²⁹SiNMR Investigation of Silicon-Aluminum Ordering in the Aluminosilicate Framework of Faujasite-Type Zeolites The high resolution magic angle spinning ²⁹Si NMR spectra of a series of NaX and NaY zeolites with Si/Al ratios of 1.18 to 67 exhibit up to five sharp signals which could be assigned to the central silicon atoms of Si(OSi)_4–n(OAl)_n building units (n = 0–4) of the aluminosilicate framework. From the signal intensities the quantitative distribution of the building units and the Si/Al ratio of the aluminosilicate lattice have been estimated. By comparison of the building units obtained from the ²⁹Si NMR spectra with those from theoretical model structures detailed information on silicon-aluminum ordering of the zeolite framework has been derived. Except for NaX of Si/Al = 1.4 a centrosymmetrical distribution of Si and Al atoms within a double-cubooctahedra unit has been found which agrees well with the Si/Al ordering scheme proposed by Dempsey.     

Co-hydrolysis products of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions: Part 2 [1]

²⁹Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O^–)_4/2 and CH₃Si(O^–)_3/2 units, (CH₃) _n Si₈O _{20 – n} ^{/(8 – n) –} (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that ²⁹Si NMR peaks due to Si(OSi)₃(O^–) units shift to lower frequencies by replacement of the adjacent Si(O^–)_4/2 units by CH₃Si(O^–)_3/2 units, in other words, with increasing m value in Si[OSi(O^–)₃]_{3 – m} [OSi(CH₃) (O^–)₂] _m (O^–) (m=0–2). Peaks from CH₃ Si(OSi)₃ units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH₃Si(O^–)_3/2 units in the cubic octameric siloxane framework of (CH₃) _n Si₈O _{20 – n} ^{/(8 – n) –} (n=2, 3), for both of which three isomers are present, have been estimated.     

Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

Partially deuterated Ca₃Al₂(SiO₄)_y(OH)_12−4y-Al(OH)₃ mixtures, prepared by hydration of Ca₃Al₂O₆ (C₃A), Ca₁₂Al₁₄O₃₃ (C₁₂A₇) and CaAl₂O₄ (CA) phases in the presence of silica fume, have been characterized by ²⁹Si and ²⁷Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca₃Al₂(OH)₁₂ and Al(OH)₃ phases were detected. From the quantitative analysis of ²⁷Al NMR signals, the Al(OH)₃/Ca₃Al₂(OH)₁₂ ratio was deduced. The incorporation of Si into the katoite structure, Ca₃Al₂(SiO₄)_3−x(OH)_4x, was followed by ²⁷Al and ²⁹Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of ²⁷Al MAS-NMR components associated with Al(OH)₆ and Al(OSi)(OH)₅ environments. The ²⁹Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From ²⁹Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.     

Raman Spectroscopic Study of Aluminum Silicate Complexes at 20°C in Basic Solutions

Raman spectroscopic measurements were performed at ambient temperature onaqueous silica-bearing solutions (0.005 < m _Si < 0.02; 0 < pH < 14). The spectraare consistent with the formation of monomeric Si(OH)^o ₄, SiO(OH)^– ₃ andSiO₂(OH)^2– ₂ species at acid to neutral, basic, and strongly basic pH, respectively.Raman spectra of aqueous Al-bearing solutions at basic pH confirm thepredominance of the Al(OH)^– ₄ species in a wide concentration range (0.01 < m _Al < 0.1).Raman spectra of basic solutions (12.4 < pH < 14.3), containing both Al andSi, exhibit a strong decrease in intensities of SiO(OH)^– ₃, SiO₂(OH)^2– ₂, andAl(OH)^– ₄ bands in comparison with Al-free Si-bearing and Si-free Al-bearingsolutions of the same metal concentration and pH, suggesting the formation ofsoluble Al—Si complexes. The amounts of complexed Al and Si derived fromthe measurements of the Al and Si band intensities in strongly basic solutions(pH 14) are consistent with the formation, between Al(OH)^– ₄ andSiO₂(OH)^2– ₂, of the single Al—Si dimer SiAlO₃(OH)^3– ₄ according to the reactionSiO₂(OH)^2– ₂ + Al(OH)^– ₄ SiAlO₃(OH)^3– ₄ + H₂OAt lower pH ( 12.5) the changes in band intensities are consistent with theformation of several, likely more polymerized, Al—Si complexes.     

IR and29Si NMR investigation of the influence of alkaline modification on the structure of hydrothermally dealuminated Y zeolites

The change in the structure of NH₄NaY zeolite (53 % NH₄ ⁺, Si/Al = 2.37) after hydrothermal treatment at 873 K followed by modification with aqueous KOH solution at 353 K was studied by IR and²⁹Si NMR spectroscopy. It has been shown that hydrolytic cleavage of the Al-O bond of the deammoniated zeolite sites by hydrothermal treatment predominates in the framework groups Si(OAl) _n (OSi)_4–n ,n=2, 3. Molecular water adsorbed on such a sample exists as hydrogen-bonded associates with hydrogen bonds of various strengths reaching that in ice-like structures (the band at 2468 cm^–1). Treatment with an alkali results in partial regeneration of the normal bridge bonds. The exchange of the protons of the terminal silanol groups with the alkaline cation prevents those groups from participating in the regeneration process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 387–391, March, 1994.     

Gelation of Aluminosilicate Systems Under Different Chemical Conditions

Optically clear aluminosilicate gels of different chemical compositions (0–0.9 mole ratios of total Al/(Si + Al)) were prepared directly from solutions of inorganic aluminum salts, tetraethoxysilane, water and alcohol without the time-consuming sol forming. However, in these gels only 0–75% of total Al content was incorporated by chemical bonding into the gel network depending on the compositions of gels and the preparation conditions. The incorporation of aluminum atoms into the gel framework and the structure of wet gels were investigated by chemical analysis, ²⁷Al magic angle spinning nuclear magnetic resonance, and small angle X-ray scattering. The present method may be most favourable for the preparation of aluminosilicate gels with 0.30–0.70 mole ratios of total Al/(Si + Al). At lower Al content acidic catalysis is required. Above 0.70 mole ratio homogeneous gels cannot be obtained by this method. The highest aluminum incorporation in homogeneous gel structures of various mole ratios of total Al/(Si + Al) was 0.53 mole ratio of bonded Al/(Si + Al) in contradiction to 0.1 mole ratio of Al/(Si + Al) achieved by traditional melting process of glass.     

Aluminum-27 NMR study of some AlCl3−MCl molten systems

Aluminum-27 NMR was used to investigate AlCl₃–MCl (M=Li, Na, K, Butylpyridinium) molten mixtures. In AlCl₃ rich mixtures, the²⁷Al resonance line was resolved into two components corresponding to the AlCl ₄ ^– and Al₂Cl ₇ ^– species, which were shown to undergo chemical exchange line broadening. This broadening was found to be cation and temperature dependent.     

Magic-Angle-Spinning NMR (MAS-NMR) Spectroscopy and the Structure of Zeolites

After outlining the chemical features and properties which make zeolites such an important group of catalysts and sorbents, the article explains how high-resolution solid-state NMR with magic-angle spinning reveals numerous new insights into their structure. ²⁹Si-MAS-NMR readily and quantitatively identifies five distinct Si(OAl)_n(OSi)_4-n structural groups in zeolitic frameworks (n = 0, 1,….4), corresponding to the first tetrahedral coordination shell of a silicon atom. Many catalytic and other chemical properties of zeolites are governed by the short-range Si, Al order, the nature of which is greatly clarified by ²⁹Si-MAS-NMR. It is shown that, as expected from Pauling's electroneutrality principle and Loewenstein's rule, both in zeolite X and in zeolite A (with Si/Al = 1.00) there are no ? Al? O? Al? linkages. In zeolite A and zeolite X with Si/Al = 1.00 there is strict alternation of Si and Al on the tetrahedral sites. Ordering models for Si/Al ratios up to 5.00 (in zeolite Y) may also be evaluated by a combination of MAS-NMR experiments and computational procedures. ²⁹Si-MAS-NMR spectra reveal the presence of numerous crystallographically distinct Si(OSi)₄ sites in silicalite/ZSM-5, suggesting that the correct space group for these related porosilicates is not Pnma. ²⁷Al-MAS-NMR clearly distinguishes tetrahedrally and octahedrally coordinated aluminum, proving that, contrary to earlier claims, Al in silicalite is tetrahedrally substituted within the framework. In combination, ²⁹Si- and ²⁷Al-MAS-NMR is a powerful tool for monitoring the course of solid-state processes (such as ultrastabilization of synthetic faujasites) and of gas-solid reactions (dealumination of zeolites with silicon tetrachloride vapor at elevated temperatures). They also permit the quantitative determination of framework Si/Al ratios in the region 1.00 < Si/Al < 10 000. Since most elements in the periodic table may be accommodated within zeolite structures, either as part of the exchangeable cations or as building units of the anionic framework, there is immense scope for investigation by MAS-NMR and its variants (cross-polarization, multiple pulse and variable-angle spinning) of bulk, surface and chemical properties. Some of the directions in which future research in zeolite science may proceed are adumbrated.     

Aluminium‐27 NMR investigation of the influence of cation type on aluminosilicate solutions

The effects of tetraalkylammonium (TAA) and alkali metal cations on the equilibrium distribution of aluminosilicate oligomers in aqueous alkaline aluminosilicate solutions were investigated using ²⁷Al NMR spectra and their evolution with time. The results indicate that there are no differences in the initial equilibria involving solutions containing both TAA and alkali metal cations on the one hand and those containing alkali metal cations only. However, re‐equilibration of the aluminosilicate species for TAA/Na aluminosilicates is slow (usually not detectable on the time‐scale of the experiments), whereas when purely alkali metal cations are used, the spectra alter over a period of ～1 h, such that resolution is degraded substantially. In the latter case, it is suggested that the anions aggregate into larger systems, although the solutions are still clear. ²⁹Si NMR evidence for slow equilibration of silicate and aluminosilicate solutions at higher concentrations is also discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Herstellung und Anionenkonstitution von kristallinen Tetramethylammonium-alumosilicaten und -alumosilicatlösungen

Synthesis and Anion Constitution of Crystalline Tetramethylammonium-aluminosilicates and -aluminosilicate Solutions Crystalline tetramethylammonium aluminosilicates with molar constitutions of wN(CH₃)₄OH · xSiO₂ · y Al₂O₃ · zH₂O and w = 1 to 1.2; x = 1; y = 0.02 to 0.5; z = 8.1 to 9.7 has been obtained from mixtures of diluted TMA aluminate and TMA silicate solutions with different molar Si/Al ratios by concentration and cooling down of the mixtures. Investigations of the TMA aluminosilicates by means of trimethylsilylation method show that the structure of the TMA aluminosilicates consists of double fouring units in analogy to the aluminum free TMA silicates. The arrangement of the Al atoms in the double four-rings agrees in general with Loewenstein's rule and leads to five distinct types of double four-rings with different Al content and Si? Al distribution. By the methods used in this study no distinction can be made between monomeric or polymeric arrangements of the double four-ring units. The existence of aluminosilicate anions in aqueous solutions is discussed.     

Characteristic lengths and the structure of salt free polyelectrolyte solutions. A small angle neutron scattering study

We have studied salt free semi dilute polyelectrolyte solutions by small angle neutron scattering. Specific labelling associated with an extrapolation method has allowed the separation of the form factor of a single polyelectrolyte chainS ₁(q) and the structure factorS ₂(q). Two lengths are deduced from these two factors: the persistence lengthb _t which characterizes the electrostatic interactions along the chain by a fitting ofS ₁(q) with calculation of the scattering function for a wormlike chain, and fromS ₂(q),q _m ^–1 which characterizes the interactions between chains. These two lengths vary in the same way with the concentration of polyions (b _t C _p ^–1/2 ,q _m ^–1 C _p ^–1/2 ) and a constant relation exists between them: only one length is then necessary to describe the structure of polyelectrolyte soltuion on this semidilute concentration range.Laboratoire Commun CEA-CNRS.     

Reaction of Plutonium(VI) with Orthosilicic Acid Si(OH)4

Reaction of Pu(VI) with Si(OH)₄ (at concentration 0.004–0.025 mol l^–1) in a 0.2 M NaClO₄ solution at pH 3–8 is studied by spectrophotometric method. In the range of pH 4.5–5.5, PuO₂(H₂O)₄OSi(OH)₃ ⁺ complex is formed, while at pH > 6, PuO₂(H₂O)₃O₂Si(OH)₂ or hydroxosilicate complex PuO₂(H₂O)₃(OH)OSi(OH)₃ is recorded. The equilibrium constants are calculated for the reactions of formation of PuO₂(H₂O)₄OSi(OH)₃ ⁺ and PuO₂(H₂O)₃O₂Si(OH)₂ and their concentration stability constants: log K ₁ = –3.91 ± 0.17 and log K ₂ –10.5; log ₁= 5.90 ± 0.17 and log ₂ 12.6. The PuO₂(H₂O)₄OSi(OH)₃ ⁺ complex is significantly less stable than analogous complex of U(VI). Calculations of the forms of Pu(VI) occurrence at the Si(OH)₄ concentration equal to 0.002 mol l^–1 showed that the maximum fraction of the PuO₂(H₂O)₄OSi(OH)₃ ⁺ complex is 10% (pH 6.5), while the fraction of PuO₂(H₂O)₃O₂Si(OH)₂ is almost 40% (pH 8).     

27Al NMR MAS Spectral Studies Inferring the Initiation of Geopolymerization Reaction on Together Mechanochemical Grinding of Raw Materials

Chemical shifts and intensities of the ²⁷Al NMR signals provide structural information about the environment of Al nuclei in presence of an external magnetic field. This paper analyzes the structural information of the aluminum nuclei present in the precursor material after mechanochemical co‐grinding of the raw materials, namely fly ash, NaOH, and amorphous tricalcium phosphate [Ca₃(PO₄)₂], with the help of ²⁷Al MAS NMR spectral studies. The results indicate transformation of the sixfold coordination Al ions with oxygen AlQ6 present in aluminosilicate material fly ash to fourfold AlQ4 and fivefold AlQ5 in the precursor material. The variation in chemical shift is between δ 64 and 65 ppm. This indicates that, in addition to direct bonding to the oxygen atom, the Al tetrahedron is also bonded to Si as [AlQ4(4Si)]. Thus, the mechanochemical co‐grinding of the raw materials initiates a solid‐state chemical reaction among them. The addition of water alone to this precursor material results in the formation of the geopolymeric material unlike the conventional geopolymeric system which requires the addition of a highly alkaline aqueous solution to fly ash. This study helps in the determination of the reaction mechanism during the mechanochemical transformation of raw materials into the geopolymeric product by a novel process.     

Surprises in the structural chemistry of zeolites

High-resolution electron microscopy, apart from strikingly confirming the correctness of the X-ray-based models for the skeletal structure of the aluminosilicate frameworks of zeolites, points to the existence of new families of ordered, crystalline microporous solids (e.g., with composition A_xB_xC_m?xO_2m · nH₂O, where A is an exchangeable monovalent cation, B is Al or Ga, C is Si or Ge, and x, m, n are integers.) It also reveals crystalline imperfections and unexpected superlattice structures in A-type and faujasitic zeolites, and the nature of the intergrowths in, for example, $\text{ZSM-5}\text{ZSM-11}$ materials. The short-range order of Si and Al within the aluminosilicate framework may be directly explored by magic-angle-spinning NMR (MASNMR) employing ²⁹Si and ²⁷Al nuclei. This technique probes the site symmetry and environment of these atoms. Al in tetrahedral as well as in octahedral sites may be readily identified and so may the populations of groups such as Si(OAl)₄, Si(OAl)₃, (OSi), etc., so that new information is obtained pertaining to Si, Al ordering in a variety of zeolitic solids.     

29Si and 17O NMR investigations on Si−O−Ti bonds in solutions of diphenylsilanediol and titanium-tetra-isopropoxide

The structural units in diphenylsilanediol/titanium-isopropoxide solutions with molar ratio Si:Ti between 1:0.1 and 1:5 were examined by means of ²⁹Si and ¹⁷O NMR. The main component in solutions with molar ratio Si/Ti=1:0.1 is the chain-like octaphenyltetrasiloxanediol. With increasing Ti-isopropoxide content (1:0.25–1:05) Si–O–Ti units of the spirocyclic titanosiloxane Ti[O₅Si₄(C₆H₅)₈]₂ prevail in the solutions accompanied by the chain-like tetrasiloxanediol. The ²⁹Si NMR spectra of 1:1 solutions indicate a lot of different Si containing building units with chemical shifts mainly between-40 and-46 ppm. The signals with a chemical shift between-40 and-46 ppm are probably caused by Si atoms which are connected via oxygen bridges directly (Si–O–Ti) or indirectly (Si–O–Si–O–Ti) with titanium. Contrary to the 1:1 solutions only one or two different species with Si–O–Ti units are present in high Ti-alkoxide containing solutions (1:5). ²⁹Si and ¹⁷O NMR results reveal a quick hydrolysis of the Ti–O–Si bonds to titanium-oxo-hydroxo-polymers and phenylsiloxanediols or their isopropyl esters after the addition of water to the solutions. This separation into species only containing either Ti–O–Ti or Si–O–Si bonds can entail a decreased homogeneity of the reaction products on a molecular level.     

Yttrium Siloxide Complexes Bearing Terminal Methyl Ligands: Molecular Models for Ln−CH3 Terminated Silica Surfaces

Surface organometallic chemistry (SOMC) on silica materials is a prominent approach for the generation of highly active heterogenized polymerization catalysts. Despite advanced methods of characterization, the elucidation of the catalytically active surface species remains a challenging task. Alkylated rare‐earth metal siloxide complexes can be regarded as molecular models of respective covalently bonded alkylated surface species, primarily used for 1,3‐diene polymerization. Here, we performed both salt metathesis reactions of [Y(MMe₄)₃] (M = Al, Ga) with [K{OSi(OtBu)₃}] and alkylation reactions of [Y{OSi(OtBu)₃}₃]₂ with AlMe₃. The obtained complexes [Y(CH₃)[(AlMe₂){OSi(OtBu)₃}₂](AlMe₄)]₂, [Y(CH₃)[(AlMe₂){OSi(OtBu)₃}₂]‐{OSi(OtBu)₃}], [Y{OSi(OtBu)₃}₃(μ‐Me)Y(μ‐Me)₂Y{OSi(OtBu)₃}₂(AlMe₄)], and [Y(CH₃)(GaMe₄){OSi(OtBu)₃}]₂ represent rare examples of organoyttrium species with terminal methyl groups. The formation and purity of the mixed methyl/siloxy yttrium complexes could be enhanced by treating [Y(MMe₄)₃] with [K(MMe₂){OSi(OtBu)₃}₂]_n (M=Al: n=2; M=Ga: n=∞). Complexes [K(MMe₂){OSi(OtBu)₃}₂]_n were obtained by addition of [K{OSi(OtBu)₃}] to [Me₂M{OSi(OtBu)₃}]₂. Deeper insight into the fluxional behavior of the mixed methyl/siloxy yttrium complexes in solution was gained by ¹H and ¹³C NMR spectroscopic studies at variable temperature and ¹H–⁸⁹Y HSQC NMR spectroscopy.     

Evolution of the Texture and Structure of SiO2–Al2O3 Xerogels and Aerogels as a Function of the Si to Al Molar Ratio

SiO₂–Al₂O₃ aerogels and xerogels with a Si to Al molar ratio r _Si/Al varying from 0.25 to 20, were made by sol-gel process in acidic conditions at pH 2 and respectively dried by the CO₂ supercritical method and by solvent evaporation. The Al precursor was also chelated with ethylacetoacetate, which made it possible to study the structure and texture of such gels in conditions favorable to the formation of mixed Al–O–Si bonds. Nitrogen adsorption isotherms according to the Brunauer, Emmett and Teller method (BET), ²⁷Al magic angle spinning nuclear magnetic resonance (²⁷Al MAS-NMR), Fourier Transformed Infrared Spectroscopy (FTIR) and Infrared absorbance spectra after Temperature Programmed Desorption (TPD) of pyridine, showed that the Si–O infrared asymmetric stretching vibration and the Bronsted acidity relative to the Lewis acidity, depended on the ratio of Al^IV to Si atoms.     

Reactivity of Extra‐framework Species of USY Zeolites in Alkaline Medium

Zeolites of type USY (ultra‐stable Y) were obtained by steaming of NH₄NaY modification. Samples were modified by subsequent alkaline treatment in KOH solution. USY and USY‐KOH were characterised by chemical element analysis, XRD, IR, ²⁹Al and ²⁹Si MAS NMR spectroscopic measurements. Correct silicon to aluminium ratios (Si/Al) were determined by XRD and IR (double ring vibration w_DR) data whereas values calculated according to data of ²⁹Si MAS NMR and IR spectroscopy (asymmetrical TOT valence vibration w_TOT) appeared to be too high., In the latter case, the signals of the zeolite framework were strongly superimposed by that of extra‐framework silica gel (EFSi) formed during steaming. It was found that alkaline leaching induces desilication of silicon‐rich area of the zeolite framework and partial dissolution of EFSi. Silicate ions of both react with likewise dissolved extra‐framework aluminium (EFAl) to form X‐ray amorphous aluminosilicate. Consequently, the superposition of the ²⁹Si MAS NMR signals of the zeolite framework by silica gel was reduced for Q⁴(0Al) but increased for Q⁴ (2Al) and Q⁴(3Al) structure units. A reinsertion of EFAl into the zeolite framework has not been observed.