MFI Topology Research Articles

Methyl mercaptan-to-hydrocarbons: Effect of topology of zeolite catalysts

The conversion of methyl mercaptan was examined over zeolites with MFI, FAU, BEA, MOR, CHA and MWW topology and Si/Al ratio between 10 and 19. At 450 °C, over all catalysts, the reagent has been primarily consumed into hydrocarbons and H2S. The crucial variables affecting the hydrocarbon distribution over zeolites were mainly their pore size/architecture and the amount of the acid sites. Over 3D H-ZSM-5, H-β and H-MOR zeolite, many aromatics and only few olefins were produced. In contrast, and analogous to methanol-to-hydrocarbons process, H-SSZ-13 and H-MCM-22 zeolite (containing cages and small pores) mainly produced C2-C3 olefins.

Breaking the stability limit of zeolite-based alkane dehydrogenation catalysts

Metal catalysts confined inside zeolite micropores or crystals are widely applied in the chemical industry because of their distinctive catalytic functions, especially with regard to the conversion of small and stable alkane molecules [1,2]. Silicalite-1 (S-1), a pure silica zeolite with an MFI topology, has a robust framework capable of withstanding harsh thermal and chemical conditions. Recently, S-1-based catalysts have demonstrated significant advantages in the construction and stabilization of various active metal centers and have attracted considerable attention for their potential in alkane dehydrogenation reactions. The absence of acidic sites prevents various acid-catalyzed side reactions, rendering S-1 a promising candidate for high-temperature reactions such as non-oxidative propane dehydrogenation (PDH). Sun et al. revealed that encapsulating subnanometer bimetallic PtZn clusters in S-1 resulted in a high propylene selectivity of 99%, with no catalyst deactivation even after 200h in the PDH reaction [3]. However, sustaining high stability at high conversion rates is still challenging for PDH reactions, and commercial processes are still based on Pt- and Cr-based catalysts, which need frequent regeneration.

Impact of Sn Lewis Acid Sites on the Dehydration of Cyclohexanol.

The impact of Sn on the concentration and strength of acid sites in Al containing zeolites with MFI topology and their catalytic activity for the dehydration of cyclohexanol in the aqueous phase has been investigated. The materials maintain constant Al concentrations and consequently Bro̷nsted acid site (BAS) concentrations, while exhibiting an increasing concentration of Sn Lewis acid sites (LAS). The presence of water alters LAS(Sn), leading to weak BAS(Sn) that increases the concentration of water in the zeolite micropore, while leaving the rate of dehydration of cyclohexanol unchanged. The TOF increases with the concentration of BAS(Al) in close contact with framework LAS(Sn), referred to as BAS(Pair). The increase in the Arrhenius pre-exponential factor, without affecting the activation barrier (E a), leads to the hypothesis that the proximity of both sites allows for a later transition state induced by the polarization of the C-O bond, leading in turn to a higher transition entropy.

Catalytic pyrolysis of straight-run light oil to light olefins: Role of molecular structure and catalytic materials

The development of straight-run light oil catalytic pyrolysis to light olefins process is an important approach of achieving the transformation and upgrading of the current oil refining industry. However, the industrialization of the catalytic pyrolysis process for straight-run light oil has been slow. Herein, we investigated the decomposition of complex straight-run light oil into different structural units and further examined their effects on light olefins production. The results indicated that the yields of light olefins cracked over MFI zeolite were about 45 % and 30 % for alkane structure and cycloalkane ring structure, respectively. Further analysis showed that the olefin structure could theoretically be cracked to 100 % light olefins, but in fact, 40 % of the light olefins were lost due to the transfer of 10 % hydrogen. Subsequently, the effects of zeolite topology and acid properties on the cracking of different structural units were further analyzed. It was found that zeolites with MTT and MFI topologies contributed to the catalytic pyrolysis of chain and cycloalkane ring structures, respectively, because appropriate pore size helped diffusion of hydrocarbon molecules and inhibited side reactions such as hydrogen transfer. Compared with MFI zeolite, the light olefins yield produced by chain structure cracking over MTT zeolite increased by 5.83 %-10.54 %. In addition, it was discovered that zeolites with total and strong acids in the range of 0.2–0.4 mmol/g and 0.1–0.2 mmol/g, respectively, were beneficial for the cracking of light alkanes in straight-run light oils to light olefins. This work provides useful insights into the fundamental understanding and development of straight-run light oil catalytic pyrolysis to light olefins process.

Highly hydrophobic zeolite ZSM-8 with perfect framework structure obtained in a strongly acidic medium

The synthesis of zeolites in a strongly acidic medium is a new and nearly unexplored chemistry field. In addition to the previously reported silicalite-1 and the several clathrasils, this paper elaborates that one more material of unique properties could be successfully crystallized in the strongly acidic fluoride medium. A pure-silica zeolite ZSM-8 has been obtained using tetraethylammonium ion as a structure-directing agent. Rietveld refinement proves that ZSM-8 is of the MFI topology, i.e., it is another silicalite-1 but different in framework distortions. Moreover, the discrete and uniform crystals of the acidic-medium synthesized pure-silica ZSM-8 possess a substantially perfect framework structure and thus hydrophobic surfaces. This remarkable character renders the material an ideal adsorbent for discriminating molecules on the polarity basis, which is desired in developing green separation processes. C3H8, CH4, and CO2 are chosen as examples respecting their different polarities and tested for the adsorptive parameters.

Selective Alkylation of Benzene with Methanol to Toluene and Xylene over H-ZSM-5 Zeolites: Impact of Framework Al Spatial Distribution

The alkylation of benzene with methanol can effectively generate high-value-added toluene and xylene out of surplus benzene, which is now achieved primarily using solid acids like H-ZSM-5 zeolites as catalysts. In this work, two H-ZSM-5 samples with distinct framework aluminum (AlF) distributions, but otherwise quite similar textural and acidic properties, have been prepared by employing tetrapropylammonium hydroxide (TPAOH) and n-butylamine (NBA) as organic structure-directing agents (OSDAs). Systematical investigations demonstrate that AlF is preferentially located at the intersections in MFI topology when TPAOH is adopted. In contrast, less AlF is positioned therein as NBA is utilized. Density functional theory (DFT) calculations reveal that the transition-state complexes cannot be formed in the straight and sinusoidal channels due to their much smaller sizes than the dynamic diameters of transition states, whereas there are adequate spaces for the formation of transition states at the intersections. Benefitting from abundant AlF at the intersections, which provides more acid sites therein, H-ZSM-5 synthesized from TPAOH is more active relative to the counterpart obtained from NBA. At a WHSV of 4 h−1 and 400 °C, the former catalyst gives a 52.8% conversion, while the latter one affords a 45.9% conversion. Both catalysts display close total selectivity towards toluene and xylene (ca. 84%). This study provides an efficient way to regulate the distribution of acid sites, thereby enhancing the catalytic performance of H-ZSM-5 zeolite in the titled reaction.

Revealing Active Sites and Reaction Pathways in Methane Non-Oxidative Coupling over Iron-Containing Zeolites.

Non-oxidative coupling of methane is a promising route to obtain ethylene directly from natural gas. We synthesized siliceous [Fe]zeolites with MFI and CHA topologies and found that they display high selectivity (>90 % for MFI and >99 % for CHA) to ethylene and ethane among gas-phase products. Deactivated [Fe]zeolites can be regenerated by burning coke in air. In situ X-ray absorption spectroscopy demonstrates that the isolated Fe3+ centers in zeolite framework of fresh catalysts are reduced during the reaction to the active sites, including Fe2+ species and Fe (oxy)carbides dispersed in zeolite pores. Photoelectron photoion coincidence spectroscopy results show that methyl radicals are the reaction intermediates formed upon methane activation. Ethane is formed by methyl radical coupling, followed by its dehydrogenation to ethylene. Based on the observation of intermediates including allene, vinylacetylene, 1,3-butadiene, 2-butyne, and cyclopentadiene over [Fe]MFI, a reaction network is proposed leading to polyaromatic species. Such reaction intermediates are not observed over the small-pore [Fe]CHA, where ethylene and ethane are the only gas-phase products.

Revealing Active Sites and Reaction Pathways in Methane Non‐Oxidative Coupling over Iron‐Containing Zeolites

AbstractNon‐oxidative coupling of methane is a promising route to obtain ethylene directly from natural gas. We synthesized siliceous [Fe]zeolites with MFI and CHA topologies and found that they display high selectivity (>90 % for MFI and >99 % for CHA) to ethylene and ethane among gas‐phase products. Deactivated [Fe]zeolites can be regenerated by burning coke in air. In situ X‐ray absorption spectroscopy demonstrates that the isolated Fe3+ centers in zeolite framework of fresh catalysts are reduced during the reaction to the active sites, including Fe2+ species and Fe (oxy)carbides dispersed in zeolite pores. Photoelectron photoion coincidence spectroscopy results show that methyl radicals are the reaction intermediates formed upon methane activation. Ethane is formed by methyl radical coupling, followed by its dehydrogenation to ethylene. Based on the observation of intermediates including allene, vinylacetylene, 1,3‐butadiene, 2‐butyne, and cyclopentadiene over [Fe]MFI, a reaction network is proposed leading to polyaromatic species. Such reaction intermediates are not observed over the small‐pore [Fe]CHA, where ethylene and ethane are the only gas‐phase products.

Evaluating the efficacy of zeolites synthesized from natural clay for the methanol-to-hydrocarbon process.

Introducing sustainability into advanced catalytic material design is essential to address growing environmental concerns. Among them, synthesizing inorganic zeolite materials from non-traditional sources (like natural clay) offers several advantages, contributing to sustainability and environmental stewardship. With this objective, we used kaolin to synthesize zeolites with different topologies: SSZ-13 (8-MR with CHA topology), ZSM-5 (10-MR with MFI topology), and Beta (12-MR with BEA topology) (MR: member ring), where a simple and flexible synthetic protocol was adopted without any significant changes. All these zeolites were subjected to catalytic performance evaluation concerning the industrially relevant methanol-to-hydrocarbon (MTH) process. Herein, the kaolin-derived zeolites, especially ZSM-5, led to superior performance and demonstrated enhanced catalyst deactivation-resistant behavior compared to their zeolite counterparts prepared from traditional synthetic routes. Various characterization tools (including under operando conditions) were employed to understand their reactions and deactivation mechanisms. Overall, making zeolites from non-traditional sources presents a pathway for sustainable and environmentally friendly material production, offering benefits such as reduced resource dependence, lower energy consumption, and tailored physicochemical properties beneficial to catalysis. In a broader context, such a research approach contributes to the transition toward a more sustainable and circular economy.

Reduction of non-methane hydrocarbons in cooking oil fumes via adsorption on MFI: Effect of zeolitic framework composition

The growth of public awareness of hazard from gaseous pollutants emitted by cooking activities spawned the implement of new laws & regulations as well as new technologies for cooking oil fumes emission control. Considering the emission characteristics of large air volume and intermittence of cooking fumes, in this work, TS-1 was firstly applied as an efficient adsorbent for enriching the low-concentrated complex humid volatile organic compounds (VOCs) from cooking oil fumes. In order to illustrate the superiority of Ti-O-Si framework as a cooking VOCs adsorbent, zeolites with the same MFI topology to TS-1 but different framework compositions of Si-O-Al (ZSM-5) and Si-O-Si (silicalite-1, hereinafter referred as S-1) were also investigated for comparison. Related characterizations were performed to reveal the difference among three zeolites. It was found that textural properties, surface silanol density and defect content significantly affect the adsorption site accessibility, water resistance as well as organophilicity of zeolites adsorbents, all of which play a decisive role in the adsorption process of cooking oil fumes. Both TS-1 and S-1 present much stronger water resistance than commercial ZSM-5 due to lacking hydrophilic Si-OH-Al groups (S-1 > TS-1 > ZSM-5), while TS-1 shows better organophilic property than both S-1 and ZSM-5 (in an order of TS-1 > ZSM-5 > S-1) due to the physical and electrical interaction between Ti-contained framework and organic molecular. These characteristics jointly make the zeolite with Ti-O-Si framework be a good adsorbent candidate for VOCs elimination from cooking fumes.

One‐pot Synthesis of Hierarchical, Micro‐macroporous Zeolites with Encapsulated Metal Particles as Sinter‐resistant, Bifunctional Catalysts

AbstractWe report a new one‐pot synthesis procedure for hierarchical zeolites with intracrystalline macropores and metal particles encapsulated within the zeolitic walls. The synthesis allows to prepare macroporous zeolites of MFI topology with different heteroatoms (silicalite‐1, ZSM‐5 and TS‐1) and different encapsulated noble metal particles, such as gold, platinum and palladium. The hierarchically structured zeolites contain large macropores with diameters around 400 nm, which are well distributed and interconnected and should significantly enhance mass transport properties. The encapsulation of metal nanoparticles within the zeolitic walls leads to remarkable sinter resistance of the particles. Encapsulated gold nanoparticles (2.6 nm) do not significantly change in size during an 18‐hour treatment at 600 °C under air, while non‐encapsulated gold particles sinter heavily during the same treatment. Catalytic experiments for the direct epoxidation of propene with hydrogen and oxygen show that both catalytic functions of a macroporous TS‐1 sample that encapsulates gold particles are accessible and active. This catalyst displays high activity, although PO selectivity could still be improved. These materials show great potential for use in catalytic applications, due to their bifunctional nature, high sintering resistance, shape selective properties and hierarchical structure.

A Facile Method to Synthesize b-Oriented Silicalite-1 Thin Film.

Silicalite-1 thin film was prepared with the following batch composition—3TPAOH:25TEOS:1450H2O:100EtOH—and synthesized using the hydrothermal technique. Silicalite-1 colloidal crystals were successfully coated on the surface of the silica substrate by the dip-coating method. The investigation of silicalite-1 thin film with organic structure-directing agents (SDA), using a seeding technique with various colloidal seed concentrations, number of dip-coating steps, and crystallization time, were systematically discussed and obtained interesting results. Silicalite-1 powder and Silicalite-1 membrane, the patterns of which showed a unique characteristic crystallography of MFI topology, were characterized by XRD, which indicated the preferred orientation along the b-axis perpendicular to the substrate surface. The morphology and crystal size aspect of Silicalite-1 were also examined by a scanning electron microscope (SEM).

Machine learning accelerated high-throughput screening of zeolites for the selective adsorption of xylene isomers.

The production of widely used polymers such as polyester currently relies upon the chemical separation of and transformation of xylene isomers. The least valuable but most prevalent isomer is meta-xylene which can be selectively transformed into the more useful and expensive para-xylene isomer using a zeolite catalyst but at a high energy cost. In this work, high-throughput screening of existing and hypothetical zeolite databases containing more than two million structures was performed, using a combination of classical simulation and deep neural network methods to identify promising materials for selective adsorption of meta-xylene. Novel anomaly detection techniques were applied to the heavily biased classification task of identifying structures with a selectivity greater than that of the best performing existing zeolite, ZSM-5 (MFI topology). Eight hypothetical zeolite topologies are found to be several orders of magnitude more selective towards meta-xylene than ZSM-5 which may provide an impetus for synthetic efforts to realise these promising materials. Moreover, the leading hypothetical frameworks identified from the screening procedure require a markedly lower operating temperature to achieve the diffusion seen in existing materials, suggesting significant energetic savings if the frameworks can be realised.

Chromic acid dealumination of zeolites

Commercial zeolites with CHA, MFI, and LTL framework topology are subjected to acid treatment with chromic acid (H 2 CrO 4 ) solutions with concentrations ranging between 0.1 and 10 w /%. As chromic acid forms polymeric species as a function of concentration, specific effects are obtained with these three zeolites, differing by their framework topology, pore size, Si/Al ratios and crystal size. The etched zeolites are characterized by X-ray diffraction, SEM, TEM, N 2 physisorption, ICP-AES, 27 Al and 29 Si MAS NMR, 29 Si{ 1 H} cross-polarization spectra, EDX. Their acidic properties are probed with pyridine and d 3 -acetonitrile by in situ FTIR. Results indicate that the 8 MR (CHA) and 10 MR (MFI) zeolites are more resistant to acid treatment with chromic acid than the 12 MR (LTL) zeolite. This paves the way for rational control of zeolite dealumination since adjusting chromic acid concentration will generate anions appropriate for treating a particular zeolite. • CHA, MFI, and LTL zeolites are subjected to treatment with chromic acid (H 2 CrO 4 ). • Chromic acid forms polymeric species as a function of concentration. • CHA and MFI zeolites resist more to the chromic acid treatment than the LTL zeolite. • Tuning the acid concentration yields anions apt for treating a particular zeolite.

Preparation of Fe@MFI and CuFe@MFI composite hydrogenation catalysts by reductive demetallation of Fe-zeolites

Selective hydrogenation catalysts play a key role in many industrial processes, but they are primarily based on supported noble metals, such as Pt and Pd, which are usually dispersed in nanoparticles. However, the production and recovery of these noble metal nanoparticles is a very energy-consuming and expensive procedure. Accordingly, replacing these metals by other inexpensive, transition metals such as Fe and Cu without sacrificing the activity and selectivity, will necessarily reduce their production costs. Moreover, zeolites as a support provide the advantage of shape selectivity to the desired product. In this study, we develop an alternative method for preparing hydrogenation catalysts composed of metallic nanoparticles encapsulated into zeolite frameworks through reductive demetallation of Fe-zeolites or Cu/Fe-zeolites with MFI topology. Particularly, the process of reductive demetallation is described using temperature-programmed reduction (TPR) and Mössbauer spectroscopy data. The reductive demetallation of Fe-MFI, consisting of Fe extraction from the zeolite framework and formation of Fe0 nanoparticles, starts at the temperatures above 800 ℃ and finishes at 1030 ℃, when sintering occurs strongly. In contrast, introduction of second metal leads to the decrease in the reduction temperature, as process of CuFe@MFI formation finishes at 800 ℃. Both Fe@MFI and CuFe@MFI show activity in p-nitrotoluene hydrogenation to p-toluidine. Conversion of the substrate grows with increase in the Cu and Fe loading. Thus, this synthesis method of encapsulation of Fe0 nanoparticles and Fe0-Cu0 bimetallic nanoparticles into the zeolite micropores through reductive demetallation of Fe-zeolites can be used to prepare hydrogenation catalysts.

Gripper-like Silicon Species for Efficient Synthesis of Crystalline Metallosilicates with Spatially Homogeneous Heteroatoms in the Framework

Heteroatoms determine the functionalities of zeolites. Facile and effective incorporation of heteroatoms into the framework of zeolites remains an important and challenging goal. We report a strategy for efficient and simple synthesis of crystalline metallosilicates with spatially homogeneous distribution of heteroatoms and free of extra-framework metal species via the crystal dissolution and crystallization process (CDC process). This method succeeds in the synthesis of a wide range of crystalline metallosilicates with the MFI topology including TS-1, Al-MFI, Fe-MFI, Sn-MFI, and Nb-MFI zeolites as well as with other topologies such as TS-2, Ti–Al–beta zeolite, and so forth. The gripper-like silicon species, which is condensed matter of silicon species in Q2 and Q3 states (detected by 29Si NMR), was identified for the first time to be the key to the effective incorporation and spatially homogeneous distribution of heteroatoms during the CDC process. Such silicon species could bond heteroatoms efficiently to form stable and isolated Si–O–M structural units in the synthetic sol, and such structural units remain unchanged under the “protection” of silicon species during the whole liquid-phase transformation and crystallization process. In addition, the gripper-like silicon species could be obtained not only by dissolving the crystal under high basicity but also by dissolving/polymerizing amorphous silicon species under the same conditions. The CDC process for synthesizing crystalline metallosilicates with spatially homogeneous distribution of heteroatoms in the framework by controlling the state of silicon species opens up a new perspective for the synthesis of heteroatomic zeolites.

Evaluation for the Removal Efficiency of VOCs and Heavy Metals by Zeolites-Based Materials in the Wastewater: A Case Study in the Tito Scalo Industrial Area

The current study was designed to demonstrate the efficiency of selected zeolites in the immobilization of heavy metals and volatile organic compounds from water in the industrial area of Tito Scalo (Basilicata Region in Southern Italy). The efficiency of zeolite materials has been evaluated by analyzing real water samples, by a multi-technique approach. Gas chromatography (GC) and inductively coupled plasma optical emission spectrometry (ICP-OES) were selected for the detection of volatile organic compounds (VOCs) and heavy metals respectively, and then by thermal analysis (TG, DTA) and X-ray powder diffraction (XRD) to verify the presence of contaminants in the structural channels of the adsorbents. ZSM-5 zeolite (MFI topology) was suitable for volatile organic compounds, showing removal efficiencies 87%. 13X (FAU topology) was more selective for in situ abatements of heavy metals, with efficiencies up to 100%. After VOCs and heavy metals removal, structure refinements of loaded zeolites highlighted variations of both lattice parameters and extraframework content confirming the pollutants immobilization in the framework microporosities. The occurrence of these species was also confirmed by DTA curves showing different phenomena explained on the basis of the nature and number of extraframework species hosted in the zeolite micropores.

Effect of zeolite topology on NH3-SCR activity and stability of Cu-exchanged zeolites

The catalytic activity and stability of Cu-exchanged zeolites Cu-ZSM-5 (MFI topology), Cu-TNU-9 (TUN), Cu-FER (FER) and steamed Cu-Y (FAU) were evaluated in the selective catalytic NO reduction by ammonia (NH3-SCR). The NH3-SCR activity of the investigated catalysts strongly depended on the feed composition, i.e., the presence of H2O (5.0 Vol.-% of H2O). The catalysts revealed high stability during 24 h of NH3-SCR reaction, also in the presence of water vapour. DR UV–vis and FT-IR with probe molecules (CO or NO) showed the presence of isolated Cu+/Cu2+ and aggregated copper oxide species. Although Cu-ZSM-5 is less active than Cu-TNU-9 in catalysing NO oxidation to NO2, both catalysts revealed similar activity in the NH3-SCR reaction. Applying Rapid-Scan FT-IR spectroscopy and 2D COS analysis the reaction mechanism of NH3-SCR on Cu-exchanged zeolites was investigated. It is proposed that NH3-SCR over the studied Cu-exchanged catalysts proceeds via [Cu(OH)(NH3)2(NO)]+ intermediates followed by the reduction of Cu(II) to Cu(I). The differentiated speciation of copper sites is reflected in their various susceptibility for the reduction and finally affects the catalytic activity and stability of the zeolitic catalysts. The formation of the [Cu(OH)(NH3)2(NO)]+ mixed ligand species is governed by the competition between the O2− and NH3 ligands. Also the stability of the forms initiating NH3-SCR, i.e., [Cu(NH3)4]2+, [Cu(OH)(NH3)3]+ and [Cu(NH3)2]+, is ruled by the confine interaction of ammonia molecules, which can be both adsorbed on a protonic site and ligated to copper sites with the framework oxygen atoms.

Role of Recrystallization in Alkaline Treatment on the Catalytic Activity of 1‐Butene Epoxidation

AbstractTwo alkylol amines, which were ethanolamine (EOA) and triethanolamine (TEOA), were used to posttreat nanosized titanium silicalite‐1 (TS‐1) to improve its catalytic activity for 1‐butene epoxidation. Comparative studies were conducted to clarify the influences of the EOA and TEOA concentrations on the physicochemical properties through detailed characterization. EOA treatment can dissolve the framework Si, [SiO4], on the external surface of TS‐1, generating some macropores. TEOA serves as structure‐directing agent to form MFI topology other than the dissolution of [SiO4], and promotes the recrystallization of [SiO4], forming new TS‐1 particles over the external surface. The two treatments can both improve the catalytic activity of 1‐butene epoxidation, but the samples treated with TEOA exhibit better catalytic stability. This can be attributed to the characteristic recrystallization of [SiO4] in the case of TEOA treatment, stabilizing the structure of TS‐1 and maintaining more framework Ti and intercrystal space.

Studies on the synthesis of ZSM-5 by interzeolite transformation from zeolite Y without using organic structure directing agents

Abstract In this work, a study of the interzeolite transformation from a parent zeolite Y (FAU topology) into zeolite ZSM-5 (MFI topology) was carried out, without using organic structure directing agents, by addition of SiO2 to adjust the composition of the starting gel. Depending on the SiO2/Al2O3 molar ratio, zeolite Y can be present in amounts equivalent to those of seed-assisted syntheses. Zeolite Y was successfully transformed in ZSM-5, but a rigorous control of OH−/SiO2 and Na+/SiO2 molar ratios is necessary to avoid incomplete transformation and/or contamination by layered silicates, such as magadiite and kenyaite. For hydrothermal treatment duration lesser than 12 h, the phase dissolution of the Y zeolite is observed, resulting in amorphous phase after 24 h. From 48 h, nucleation and growth of ZSM-5 crystals, with increasing crystallinity up to 120 h, is observed. During the interzeolite transformation, FTIR spectra show the disappearance of the band at 568 cm−1 and the appearance of a band at 545 cm−1, assigned to the 5-membered double rings of ZSM-5. Scanning electron microscopy images suggest that the crystallites of zeolite Y condense and absorb silicate species from solution to form larger aggregates of ZSM-5 zeolite. These structural and morphological changes are accompanied by textural changes detected in nitrogen adsorption isotherms. These results suggested that a combined solution mediated and solid-state transformation mechanism is probably occurring. Since these zeolites do not possess any other structural features in common, RBU approach seems to be more adequate to describe this specific interzeolite transformation.