Hydroxyl Nests Research Articles

The Peculiar H-Bonding Network of 4-Methylcatechol: A Coupled Diffraction and In Silico Study.

The crystal structure of 4-methylcatechol (4MEC) has, to date, never been solved, despite its very simple chemical formula C7O2H8 and the many possible applications envisaged for this molecule. In this work, this gap is filled and the structure of 4MEC is obtained by combining X-ray powder diffraction and first principle calculations to carefully locate hydrogen atoms. Two molecules are present in the asymmetric unit. Hirshfeld analysis confirmed the reliability of the solved structure, since the two molecules show rather different environments and H-bond interactions of different directionality and strength. The packing is characterised by a peculiar hydrogen bond network with hydroxyl nests formed by two adjacent octagonal frameworks. It is noteworthy that the observed short contacts suggest strong inter-molecular interactions, further confirmed by strong inter-crystalline aggregation observed by microscopic images, indicating the growth, in many crystallization attempts, of single aggregates taller than half a centimetre and, often, with spherical shapes. These peculiarities are induced by the presence of methyl group in 4MEC, since the parent compound catechol, despite its chemical similarity, shows a standard layered packing alternating hydrophobic and polar layers. Finally, the complexity and peculiarity of the packing and crystal growth features explain why a single crystal could not be obtained for a standard structural analysis.

Hydrothermally Ce modified HZSM-5 zeolite enhancing its strong acidity and Brønsted/Lewis acid ratio: Stably boosting ethylene/propylene ratio for cracking n-heptane

Modulating zeolite acidity by conventional metal impregnation is a challenge in preparing hydrocarbon cracking catalyst, which often eliminates its intrinsic strong acidity, resulting in reduced the hydrocarbon conversion capacity and low light olefins (C2=-C4=) yield. Here, the Ce/HZ5-HM and CeO2/HZ5-HM catalysts were readily prepared by hydrothermally modifying HZSM-5 zeolite (HZ5) with cerium salts (Ce3+) and cerium oxide (CeO2), respectively. Comparatively, Ce/HZ5-IW catalyst was obtained by modifying HZ5 with Ce3+ using the incipient wetness impregnation. It is revealed that, compared to HZ5, Ce/HZ5-HM and CeO2/HZ5-HM catalysts have an increased ratio of strong/weak (S/W) acid and Brønsted/Lewis (B/L) acid, while Ce/HZ5-IW sample has reduced strong acidity. Further, the Ce/HZ5-HM exhibits higher acid strength, acid density, and B/L value than that of CeO2/HZ5-HM sample. When applied to cracking n-heptane reaction, compared with HZ5 and Ce/HZ5-IW, heptane conversion and ethylene yield on Ce/HZ5-HM and CeO2/HZ5-HM catalysts increase by 6–11 % and 7–9 %, yielding the ratio of ethylene/propylene (E/P) more than 1. Moreover, Ce/HZ5-HM and CeO2/HZ5-HM catalysts perform a lifetime of 117 h and 150 h, with four-to-five times longer than that of HZ5 zeolite (∼29 h) and Ce/HZ5-IW catalyst (∼39 h). The characterization results demonstrate that, adopting hydrothermal method ensures more Ce3+ interacting with the silanol groups in Ce/HZ5-HM, generating the new Brønsted acid sites and makes CeOx species incorporating into the hydroxyl nest of zeolite, which can heal the defective sites and improve stabilization of acidity and framework structure of zeolite. Therefore, the above two catalysts can highlight the monomolecular cracking reaction, low coke deposit rate, long catalytic stability.

General synthesis for supported single-atom catalysts using hydroxyl nests in zeolites

Due to their well-defined geometric and electronic structures and fully exposed active sites, single-atom catalysts (SACs) exhibit significantly enhanced catalytic activity in the field of catalysis. However, the controllable synthesis...

Simple synthesis of hierarchical Co-Meso-UTL zeolite for efficient epoxidation of styrene

Co-zeolites with hierarchical porous are significantly desirable for the liquid-phase selective epoxidation of styrene that required relatively open reaction spaces. A typical UTL germanosilicate with the absence of organic structure-directing agent molecules inside pore channels suffered from severe structural collapse after ultrasonic treatment under pure water medium, originating from the unstable germanium-rich double four ring subunits. The simple strategy cleaved the weak linkage Ge-O bands and caused the irregular location of silicon-rich cfi layers. Subsequently, Co activity centers was incorporated into the framework through reacting with the abundant silanol groups located in the hydroxyl nests at room temperature. The random arrangement of mono- or multi- cfi layers induced the stacking faults and generated a large amount of intracrystal mesopores after calcination. The resultant Co-Meso-UTL catalysts favored the molecules diffusion of large-sized styrene and target products, improving the accessibility of Co active sites and exhibiting excellent catalytic performance in the styrene epoxidation reaction with single hydrogen peroxide (H2O2) oxidant. Especially, high styrene oxide product selectivity was also obtained through controlling appropriate H2O2-added content as well as reaction time, which possessed a highest turnover frequency value of 403 h−1 among the reported catalysts.

Isomorphous incorporation of tin ions into extra-large pore framework with high-stannum content as efficient Lewis acid catalyst

Germanium-rich *CTH zeolite without organic molecules located inside pore channels experienced only partial structural collapse and subsequently repaired to high-silica structure analogous to the original topology in a short time. The surprise acid-hydrolysis process has caused a large amount of framework Ge ions were removed, giving rise to abundant hydroxyl nests. Benefiting from the unexpected variation of framework structure and chemical composition, stannosilicates Sn-*CTH with extra-large pores and various Sn loadings (Si/Sn molar ratio in the range of 30-∞) were post-prepared depending on the reaction between the added (NH4)2SnCl6 species and the formed silanol groups in the hydroxyl nests. The resultant Sn-*CTH zeolites were able to release significantly the diffusion limitations encountered by the bulky substrates and oxidants, exhibiting promising activities to catalyze the Baeyer-Villiger (B-V) oxidation of ketones with single oxidant either hydrogen peroxide (H2O2) or large-sized tert-butyl hydroperoxide (TBHP). Especially, high ε-caprolactone product selectivity was also obtained in the B-V oxidation of cyclohexanone using H2O2 oxidant through reducing the H2O2/cyclohexanone molar ratio as well as controlling appropriate reaction time, which was more efficient than the traditional Sn-Beta-F catalyst.

Highly stable VSi-beta zeolite synthesized by a post-synthesis strategy for efficiently catalyzing styrene epoxidation

To enhance the doping of vanadium in zeolites and achieve high stability, the selection of vanadium precursors containing specific vanadium species can effectively overcome this crucial problem. Two series of VxSi-Beta(A) and VxSi-Beta(N) zeolites have been prepared by a two-step post-synthesis method at pH = 1 and pH = 7. The properties and environments of vanadium in samples are investigated by UV–vis, XPS, EPR, H2-TPR and 51V MAS NMR. The bonding between vanadium and framework in VSi-Beta(A) is stronger than that of VSi-Beta(N). After the two are calcined or hydrated, the vanadium species in the former are relatively stable, while the pseudo-tetrahedral V(V) species and pseudo-octahedral V(V) species in the latter are interconverted. The changes of vanadium species in the supernatant during the preparation have been investigated by 51V static NMR. At low concentration and pH = 1, there is a unique mononuclear cation (VO2+) in the aqueous NH4VO3 solution, which is favorable for the interaction with the negatively charged hydroxyl nests generated after the nitric acid dealumination, and enables the V atoms to be tightly inserted into the framework. In styrene epoxidation, the type of V(V) species in the catalyst could significantly affect its catalytic performance, and the catalytic activity and stability of VxSi-Beta(A) are superior than that of VxSi-Beta(N).

Mechanistic insights into the interaction between binders and Y-type zeolites in fluid catalytic cracking

Binders play essential roles in fluid catalytic cracking catalysts, and their interaction mechanism with zeolites remains to be explored. The effects of three binders on REUSY zeolite were investigated. The alumina sol most notably blocked the pore channels and destructed the framework of zeolites by removing the framework Al. The silica sol diffused into the silicon hydroxyl nests and form new Si-O tetrahedrons, which enhanced the structural stability and increased the number of Bronsted acid sites in zeolites, rendering the samples’ better hydrothermal stability and higher micro-reaction activity. The influence of the colloidal sol of pseudo boehmite on zeolites was between the two.

Cu(OH)2-Ni(OH)2 engulfed by zeolite-Y hydroxyl nest and multiwalled carbon nanotube for effective methanol oxidation reaction

Cu(OH)2-Ni(OH)2 supported on zeolite-Y and combined with multi-walled carbon nanotube (MWCNT), M(OH)2-Y-CNT (M = Cu, Ni) was found to be an excellent multicomponent hybrid system for methanol oxidation reaction (MOR). The formation of metal hydroxyl nest interconnected through MWCNT produced a high current density of 5.5 A/mg with significant durability up to 11.1 h. The electrochemical oxidation of methanol was found to be significant with maximum current density when the Cu:Ni ratio was 3:1. The surface hydroxyl group of zeolite-Y and -COOH functional group of MWCNT interacted strongly with Cu(OH)2 and Ni(OH)2 and provided a strong metal to surface interaction. From the temperature programme desorption (TPD) study and pyridine adsorption FTIR analysis, it was evident that both the acidity and basicity of Cu(OH)2-Ni(OH)2-Y catalyst was influenced by the MWCNT and consequently helped in MOR. Modification with MWCNT also lead to the change in the binding energy values of Cu and Ni and thereby effected the overall MOR activity of the electrocatalyst. The MOR activity of the hybrid material was tested by modifying the glassy carbon working electrode (GCE) as well in Pt working electrode. The MOR activity was found to be much better with Pt-electrode in comparison to GCE in terms of current density, durability and stability. The Pt-electrode modified with the hybrid M(OH)2-Y-MWCNT exhibited high CO tolerance in comparison to commercial Pt/ C electrocatalyst.

Atom-planting synthesis of MCM-36 catalyst to investigate the influence of pore structure and titanium coordination state on epoxidation activity

Abstract The borosilicate ERB-1 was modified as titanosilicate with microporous and mesoporous composite MCM-36 structure accommodated as epoxidation catalyst for large size molecule of reactants in the aqueous solution. Ti-MCM-36 was synthesized by swelling and pillaring the MWW layer structure with SiO2 and atom-planting method with TiCl4. The 2D 1H double quantum NMR and in-situ infrared spectroscopy confirm that the swelling process with cetyltrimethylammonium bromide and tetrapropylammonium hydroxide for the MCM-36 synthesis causes the deboronation of the ERB-1 and formation of hydroxyl nest. During the atom-planting treatment, the TiCl4 reacts with the generated hydroxyl group and consumes the hydroxyl nest to form the tetrahedral titanium in the zeolite framework as Ti–O–Si. The UV–Vis spectra show that the incorporated titanium atoms are mainly existed in the form of tetracoordinated titanium. The titanosilicate pillared Si/Ti-MCM-36 with coexistence of tetrahedral and octahedral coordination titanium species were compared with Ti-MCM-36 to investigate the coordination state of Ti species for the liquid phase epoxidation of cyclohexene, cyclooctene with tert-butyl hydroperoxide aqueous solution, decane solution or H2O2 solution. Moreover, compared with the extra-framework octahedral coordination Ti species, the framework tetrahedral coordination titanium species are more efficient for epoxidation, especially with H2O2 as oxidant. By comparing with the performance of microporous Ti-ERB-1, the microporous and mesoporous composite Ti-MCM-36 is more efficient with the increase of the reactant molecule size from 1-hexene, cyclohexene, cyclooctene and soybean oil, which shows good epoxidation activity for soybean oil within H2O2 solution.

Effect of Zeolitic Hydroxyl Nests on the Acidity and Propane Aromatization Performance of Zinc Nitrate Impregnation-Modified HZSM-5 Zeolite

A defective HZSM-5 zeolite (SiO2/Al2O3 = 55, crystal size = 300 nm) with a high density of hydroxyl nests and its patched-up counterpart obtained by pretreating the defective zeolite with (NH4)2SiF...

Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

In this study, a series of SnO2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2 and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.

Transformation of Propane over ZnSnPt Modified Defective HZSM-5 Zeolites: The Crucial Role of Hydroxyl Nests Concentration

A series of ZnSnPt supported defective MFI zeolites with different SiO2/Al2O3 ratios (30, 110, 700, and ∞) and hydroxyl nests concentration were prepared and characterized by multiple techniques including scanning electron microscopy (SEM), nitrogen physisorption, NH3-TPD, transmission electron microscopy (TEM), hydrogen temperature programmed reduction (H2-TPR), and Fourier transform infrared spectrometer (FT-IR). It was found that Brønsted acid sites (Si(OH)Al) with strong acid strength and the hydroxyl nests with weak acid strength coexisted over the defective ZSM-5 zeolites and ZnSnPt Lewis acid sites preferentially located on the hydroxyl nests. The increase in the concentration of hydroxyl nests and SiO2/Al2O3 ratios apparently improved the distribution of ZnSnPt Lewis acid sites. The hydroxyl nest incorporated ZnSnPt Lewis acid sites showed extraordinary dehydrogenation ability. Specially, operando dual beam Fourier transform infrared spectrometer (DB-FTIR) was applied to characterize the propane transformation under reaction conditions. At low SiO2/Al2O3 ratios, the propane efficiently transforms into propene and aromatics (total selectivity of 93.37%) by the cooperation of Brønsted acid sites and ZnSnPt Lewis acid sites. While at high SiO2/Al2O3 ratios, the propane mainly transforms into propene (selectivity of above 95%) and hydrogen. This study provides guidance for the preparation of highly efficient propane dehydrogenative transformation catalyst.

Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5 Zeolite Supported Zinc Catalysts

A series of defective ZSM-5 zeolites (~300 nm, SiO2/Al2O3 ratio of 55, 100, 480 and 950) were systematically studied by XRD, SEM, 29Si MAS NMR, argon physisorption, NH3-TPD and FT-IR technologies. The nature, the amount and the accessibility of the acid sites of defective ZSM-5 zeolites are greatly different from reported ZSM-5 zeolites with a perfect crystal structure. The Brønsted acid sites (Si(OH)Al) with strong acid strength and the Brønsted acid sites (hydroxyl nests) with weak acid strength co-existed over defective ZSM-5 zeolites, which leads to a unique catalytic function. Zn(C2H5)2 was grafted onto defective ZSM-5 zeolites through the chemical liquid deposition (CLD) method. Interestingly, FT-IR spectroscopic studies found that Zn(C2H5)2 was preferentially grafted on the hydroxyl nests with weak acid strength rather than the Si(OH)Al groups with strong acid strength over different defective ZSM-5 zeolites. In particular, home-built operando dual beam FTIR-MS was applied to study the catalytic performance of Zn species located in different sites of defective ZSM-5 zeolites under real n-hexane transformation conditions. Results show that Zn species grafted over hydroxyl nests obtain better dehydrogenative aromatization performance than Zn species over Si(OH)Al groups. This study provides guidance for the rational design of highly efficient alkane dehydrogenative aromatization catalysts.

Theoretical Insights into the Interaction of Oxygenated Organic Molecules and Cobalt(II) Precursor with γ-Al2O3Surfaces

The interaction of two common oxygenates, ethylene glycol (EG) and acetic acid (AA), with the main exposed (100) and (110) surfaces of γ-Al2O3 are investigated by quantifying the thermochemistry of the drying process. Using density functional theory (DFT) calculations, we determine adsorption free energies and identify the adsorption modes and sites for both molecules interacting with the (100) and (110) surfaces of γ-Al2O3 at various coverages. While the affinity of both molecules is stronger for the (100) surface after drying, EG is more strongly adsorbed on alumina surfaces than AA. EG preferentially interacts through hydrogen bonds on the hydroxyl nests of the (100) and (110) surfaces, while it may also interact through Al–O bonds on the (110) surface at low coverage. AA is predominantly deprotonated and interacts as acetate anions through hydrogen bonds on the (110) and (100) surfaces and through Al–O bonds on the (100) surface at low coverage. We then propose a quantitative comparison of the interaction of Co2+ hexaaquo precursor with the same γ-Al2O3 surfaces. The adsorption configurations of the two organic molecules which may hinder the epitaxial growth of cobalt oligomers on alumina surfaces are identified. However, the thermodynamic analysis shows that EG and AA are less stable than the Co precursors after drying. The strong stabilization of Co precursors is attributed to its epitaxial relationship with the dried alumina surfaces as found in [Angew. Chem. Int. Ed. 2015, 54, 6824–6827] and also to a favorable entropy change during the drying process (vapor release and nitrate counterion decomposition in the gas phase). We finally discuss how these effects can be circumvented by changing the conditions of preparation and drying.

Isomorphous Incorporation of Tin Ions into Germanosilicate Framework Assisted by Local Structural Rearrangement

The crystalline structure of UTL zeolite experienced an unusual orientated collapse and reconstruction within an extremely narrow time window during the structural stabilization process by nitric acid treatment at elevated temperature. Taking full advantage of this unique structural change, extra-large-pore Sn-UTL zeolites were postsynthesized via the reaction between the SnCl4 molecules and the silanols in the hydroxyl nests, which occurred concomitantly with the removal of Ge and/or Si species from the dense layer. The original UTL topology was restored thereafter, leading to a Sn-incorporated analogue. The usage of the most seriously collapsed intermediate structure, which was captured by timing during the precisely controlled acid treatment, was vital for achieving Sn-UTL zeolites with a larger amount of isolated Sn species effectively incorporated. With tetrahedrally coordinated Sn ions in the highly stabilized UTL topology consisting of intersecting 12- and 14-membered ring (MR) pore channels, Sn-UT...

Decrement of coke from phenol hydroxylation on iron on zeolite beta by employing dealuminated support

An attempt to decrease coke formation from phenol hydroxylation on iron catalyst supported on zeolite beta (Fe/HBEA) was investigated. HBEA was dealuminated by refluxing in nitric acid. The dealumination removed all framework aluminum atoms and presumably generated hydroxyl nests of the tetrahedral vacant sites which were strongly acidic. An iron catalyst supported on dealuminated zeolite beta (Fe/D-BEA) was prepared by stirring the dealuminated HBEA in a solution of Fe(NO3)2. The obtained catalyst had an Fe loading 2.60 wt%. The Fe had an oxidation state +3 and tetrahedral coordination. After loading, the zeolite structure was slightly contracted by the insertion of Fe ions into the vacant sites and calcination. The strong acid sites on D-BEA were suppressed. When Fe/D-BEA was tested in phenol hydroxylation, a steady conversion around 56 % was reached in 6 min. Catechol and hydroquinone were the major products with the mole ratio 2:1. However, cokes were still observed. The type of cokes from Fe/D-BEA was similar to those from Fe/HBEA but the amount from Fe/D-BEA was lower. Thus, the product yields from Fe/D-BEA were higher.

The role of acid sites induced by defects in the etherification of HMF on Silicalite-1 catalysts

Defects in Silicalite-1 (structure type MFI) generate acid sites in the form of (i) hydroxyl nests present inside the channels or (ii) Brønsted–Lewis acid pairs, associated with terrace step kink sites present on the external surface of zeolite crystals. The amount of the sites has been changed by controlling the thermal treatment and pH value during preparation, or by post-synthesis treatments (ionic-exchange, silylation). These sites have been quantified by NMR, XRD and FT-IR pyridine adsorption/desorption at room temperature and 150°C, and correlated with the catalytic etherification of 5-hydroxymethyl-2-furfural (HMF) with ethanol, a relevant reaction to produce diesel additives. The results show that the surface acidity of Silicalite-1 materials presents an heterogeneous distribution of Lewis and Brønsted acid sites with different degrees of strength. The amount and distribution of such active centers determine the catalytic performance in HMF etherification. It is also shown that adsorption of water, produced in situ by ethanol condensation, has a promoter effect at lower concentration and high temperature, due to the dissociation of S2R siloxanes bonds, and formation of Lewis and Brønsted acid centers with medium-high strength, responsible for the activation pathways of HMF conversion to 5-(ethoxymethyl)furfan-2-carbaldehyde (EMF) and ethyl-4-oxopentanoate (EOP), respectively.

Further Search for Hydroxyl Nests in Acid Dealuminated Zeolite Y

The removal of Al with acid solution from a zeolite framework is customarily associated with formation of framework defects known as hydroxyl nests, but their existence has not been unambiguously confirmed thus far. In a recent study on acid dealuminated Y zeolite, pre-exchanged predominantly with Cs in order to ensure maximized elimination of molecular water that can conceal hydrogen bonded OH groups, no indication has been found for the presence of hydroxyl nests.9 We present here temperature-programmed desorption (TPD) and Fourier transform infra-red (FTIR) evidence that such hydroxyl nests cannot be identified in an approximately 20% acid dealuminated and solely sodium re-exchanged zeolite NaY(-Al) that has not been exposed to temperatures above 25 °C during and after dealumination. These experimental conclusions were matched by results of combined density functional theory (DFT)-based spectroscopic study and reactive-force field molecular dynamics calculations on full periodic model zeolites. They sh...

Crystal structure analyses of two TMA silicates with ordered defects: RUB-20, a layered zeolite precursor, and RUB-22, a microporous framework silicate

Abstract Synthesis experiments in the simple system TMAOH/SiO2/H2O led at 160°C to the crystallization of two new tetramethylammonium (TMA) silicates, RUB-20 and RUB-22. The common feature of the two silicates is the presence of ordered defects within the silicate network, necessary to compensate the charge of the occluded TMA cation. RUB-20, [(CH3)4N]1.7[Si18O35(OH)4], is a layered material with a0 = 10.493(2) Å, b0 = 13.988(2) Å, c0 = 7.411(1) Å, β = 97.80(2)° and space group P21/m. It consists of ferrierite type (fer) silicate layers which possess a significant amount of defects. These defects apply only to one particular Si–O–Si bridge which is hydrolyzed to about 50% to form two additional Si–OH/Si–O- groups which point to the interlayer region of the structure. These silanol groups together with the regular terminal silanol groups of neighbouring fer layers form a system of hydrogen bonds which binds the layers together. In addition, weak ionic bonds exist between the negatively charged silicate layers and the intercalated TMA cations. RUB-22 is a zeolite-like silicate possessing a microporous framework with double-cages, housing the TMA cations. The Rietveld structure analysis revealed a pseudo monoclinic unit cell with a0 = 13.6626(2) Å, b0 = 13.2400(2) Å, c0 = 12.3009(2) Å, α = 90.003(3)°, β = 112.700(1)°, γ = 90.005(3) and space group C 1 ¯ . $C\bar 1.$ RUB-22, [(CH3)4N]4[Si32O60(OH)12], possesses an interrupted silica framework of the same topology as RUB-10, [(CH3)4N]4[Si32B4O72] (zeolite framework type RUT), however, with the difference that defects replace the [BO4]-tetrahedra. The defects can be regarded as “hydroxyl nests” surrounding a vacancy □(OH-Si)3(-O-Si) instead of B(-O-Si)4 groups. Heating the as made materials at 600°C led in the case of RUB-20 to a highly disordered zeolite of the CDO type and in the case of RUB-22 to a distorted and defective RUT-type material.

Pore Structure of USY Zeolites in Dependence on Steaming Condition

Abstract Thermo‐chemical dealumination of zeolite Y is accompanied by formation of different mesopore types. Closed mesopores in the nuclei and open pores at the crystal surface occur due to decomposition of its corresponding frameworks which are unstable in steam. Third type of lattice mesopores is formed inside the microporous bulk after removal of aluminum atoms if the remaining hydroxyl nests dehydroxylate. This process leads to a rearrangement of the zeolite framework. In contrast to the observed phenomenon, the defects are healed by migrating of ortho‐silicic acid (H4SiO4) from the surface to the hydroxyl nests under conditions of suitable steaming. Since mesopores in USY zeolites (ultra stable Y) reduce their catalytic activity and the sorption capacity, they could be minimized by a proper treatment.