Search

Furfural hydrogenation is one of the most important reactions for the transformation of biomass‐derived resources into high value‐added chemicals. To achieve a highly efficient catalytic activity of the reaction, catalysts with a high dispersion of metal nanoparticles (NPs) on solid supports are required. However, the development of highly efficient and stable catalysts is still challenging. Herein, the highly dispersed nickel nanoparticles (Ni NPs) supported on the hierarchical ZSM‐5 nanosheets (Z5‐NS) derived from the hierarchical ZSM‐5 nanosheets@NiAl‐layered double hydroxides (LDHs) composites were successfully fabricated. Remarkably, the fabricated Z5‐NS/Ni catalyst exhibited a high furfural conversion of 85 % with a yield of furfuryl alcohol of 60 %. This work illustrates the fabrication of highly metal dispersed on solid supports with high metal loading, which can enhance the catalytic performances in the hydrogenation of biomass‐derived compounds. [ABSTRACT FROM AUTHOR]

This work determines the deactivation mechanisms of Cu/ZSM-5 catalysts used for the conversion of 2,3-butanediol to butene as part of an alcohol-to-jet route. The deactivation of the catalyst, reflected by a drop in the rate of the limiting hydrogenation step by over 90% in 24 h at a weight hourly space velocity of 5.92 h−1, proceeds via both the agglomeration of copper particles and the obstruction of copper surfaces due to carbonaceous deposits, although the former has less impact on the decrease in the hydrogenation rate. To reduce the detrimental effect of carbonaceous deposits on catalytic activity, ZMS-5 is modified through desilication of the HZSM-5 support with NaOH and CsOH solutions to generate a hierarchical structure with mesopores. The catalyst with the CsOH-treated support generates the highest overall yield of desired olefin products and experiences the slowest deactivation. This is a result of the lower Brønsted acidity and larger mesopores found in the CsOH-treated catalyst, leading to the slower formation of carbonaceous deposits and the faster diffusion of their precursors out of the pores. [ABSTRACT FROM AUTHOR]

Diffusional limitations associated with zeolite microporous systems can be overcome by developing hierarchical zeolites, i.e., materials with a micro- and mesoporous framework. In this work, Y and ZSM-5 zeolites were modified using a surfactant-mediated hydrothermal alkaline method, with NaOH and cetyltrimethylammonium bromide (CTAB). For Y zeolite, after a mild acidic pretreatment, the effect of the NaOH+CTAB treatment time was investigated. For ZSM-5 zeolite, different concentrations of the base and acid solutions were tested in the two-step pretreatment preceding the hydrothermal treatment. The properties of the materials were studied with different physical–chemical techniques. Hierarchical Y zeolites were characterized by 3.3–5 nm pores formed during the alkaline treatment through the structure reconstruction around the surfactant aggregates. The effectiveness of the NaOH+CTAB treatment was highly dependent on the duration. For intermediate treatment times (6–12 h), both smaller and larger mesopores were also obtained. Hierarchical ZSM-5 zeolites showed a disordered mesoporosity, mainly resulting from the pretreatment rather than from the subsequent hydrothermal treatment. High mesoporosity was obtained when the concentration of the pretreating base solution was sufficiently high and that of the acid one was not excessive. Hierarchical materials can be obtained for both zeolite structures, but the pretreatment and treatment conditions must be tailored to the starting zeolite and the desired type of mesoporosity. [ABSTRACT FROM AUTHOR]

In general, hierarchical zeolite synthesis will produce waste, which will cause many problems for environmental pollution. The waste that comes from the synthesis of zeolites, such as the use of hazardous chemicals from the use of many solvents, additional templates, silica sources used, and other precursors that are not environmentally friendly. One solution to the problem is to use bio-based templates. The advantage of using this bio-based template is that it is environmentally friendly, reduces dependence on hazardous chemicals, and supports sustainability for bio-based templates such as carbohydrates, chitin, and others. The use of the previously mentioned templates in zeolite synthesis can produce hierarchical pores, high crystallinity, and catalytic properties that are not inferior to conventional zeolites obtained, and more cost-effective. The efforts are expected to fulfill the principles of green chemistry, which prioritizes the environment to provide better prospects for the synthesis of hierarchical zeolites in the future. [ABSTRACT FROM AUTHOR]

The extensive use of plastics has led to a significant environmental threat due to the generation of waste plastic, which has shown significant challenges during recycling. The catalytic hydrocracking route, however, is viewed as a key strategy to manage this fossil-fuel-derived waste into plastic-derived fuels with lower carbon emissions. Despite numerous efforts to identify an effective bi-functional catalyst, especially metal-loaded zeolites, the high-performing zeolite for hydrocracking plastics has yet to be synthesized. This is due to the microporous nature of zeolite, which results in the diffusional limitations of bulkier polymer molecules entering the structure and reducing the overall cracking of plastic and catalyst cycle time. These constraints can be overcome by developing hierarchical zeolites that feature shorter diffusion paths and larger pore sizes, facilitating the movement of bulky polymer molecules. However, if the hierarchical modification process of zeolites is not controlled, it can lead to the synthesis of hierarchical zeolites with compromised functionality or structural integrity, resulting in reduced conversion for the hydrocracking of plastics. Therefore, we provide an overview of various methods for synthesizing hierarchical zeolites, emphasizing significant advancements over the past two decades in developing innovative strategies to introduce additional pore systems. However, the objective of this review is to study the various synthesis approaches based on their effectiveness while developing a clear link between the optimized preparation methods and the structure-activity relationship of the resulting hierarchical zeolites used for the hydrocracking of plastics. [ABSTRACT FROM AUTHOR]

A series of hierarchical ZSM‐5 nanocrystalline aggregates (HNZ‐5) was synthesized using a hydrothermal method with tetrapropylammonium hydroxide as a structural guide. The HNZ‐5 samples having different Si/Al molar ratios all showed suitable hierarchical architectures and the maximum surface area was found to be 329 m2/g. The SEM image displayed the width of the individual crystal particles was ~100 nm, and its nanocrystalline clusters generated intercrystalline pores. Temperature‐programmed desorption with NH3 indicated that the total acidity of this material increased with increases in the Al3+ content to a maximum of 0.47 mmol/g at a Si/Al ratio of 15. In addition, 27Al magic angle spinning nuclear magnetic resonance spectra showed that the acid sites were associated with tetrahedral and octahedral Al sites. This HNZ‐5 was applied to the catalytic cracking of waste cooking oil model compound and gave a light olefin yield as high as 43.9 % at 550 °C. Extending the reaction time to 6000 min provided a yield of light olefins in excess of 30 %, which was higher than that achieved using traditional ZSM‐5. These data confirmed that the hierarchical pore structure of HNZ‐5 resulting from the self‐assembly of nanocrystals, together with exposed acidic sites, promoted the catalytic conversion of large molecules. [ABSTRACT FROM AUTHOR]

Mesoporous/hierarchical zeolites (HZs) are a relatively new group of materials, and interest in their application in catalysis is continuously growing. This paper presents recent achievements in the application of mesoporous zeolites in catalytic reactions of nitrogen pollutant conversion. The analysis presented includes processes such as selective catalytic reduction of NOx with ammonia (NH3-SCR, DeNOx), selective catalytic oxidation of ammonia (NH3-SCO, AMOx), and catalytic decomposition of N2O. Different zeolite topologies and methods of their modification focused on mesoporosity generation (e.g., desilication, dealumination, steaming, self-assembly techniques, and application of hard and soft templates) are reviewed and compared with respect to catalytic processes. Special attention is paid to the role of porous structure and acidity, as well as the form of deposited transition metals, in the catalytic activation of modified zeolites in the elimination of nitrogen pollutants from flue gases. [ABSTRACT FROM AUTHOR]

Various commercial zeolites, including FER, MOR, ZSM‐5, BEA, and FAU frameworks, were treated with NH4F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH4F‐treated small‐medium pore FER, MOR, and ZSM‐5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12‐membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH4F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH4F concentration on the fluoride treatment of H‐ZSM‐5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt % NH4F was optimal for fabricating open‐pore H‐ZSM‐5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H‐ZSM‐5. The catalytic activities of the open‐pore H‐ZSM‐5 were evaluated with acid‐catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open‐pore H‐ZSM‐5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85 % conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H‐ZSM‐5 (~50 % of bioethanol conversion at 34 h TOS). [ABSTRACT FROM AUTHOR]

Al, Ga and B silicate hierarchical zeolites of structural types MOR, BEA, MFI and MTW with morphology of nanorods, nanolayers or nanoparticles, due to the presence of optimal strength of Brønsted acid centers are active and highly selective catalysts for indanol dehydration in mild conditions (yield of the target product up to 99%). Ga and B silicate hierarchical zeolites with low and medium acidity show moderate yields in Beckman rearrangement of oximes. Hierarchical aluminosilicate zeolites of structural types MOR, BEA and MFI of different morphology show high activity in the process of n-hexane cracking, which allows us to consider them as promising catalysts for this reaction. Formation of the basic centers in zeolite composites with different nature and structure allows obtaining effective catalysts for the cycloaddition reactions under carbon dioxide pressure. [ABSTRACT FROM AUTHOR]

Hierarchical zeolites are highly‐desired catalysts in the petrochemical industry due to their shorter diffusion length, faster diffusion rate, and better accessibility to active acid sites compared with conventional zeolites. Herein, we report a simple amino‐acid‐assisted method to synthesize urchin‐like hollow hierarchical FER zeolites with abundant mesopores and macroporous inner cavities. An amino acid (i. e. L‐lysine) is used to facilitate the agglomeration of primary gel nanoparticles. The preferential nucleation and crystal growth at the external surfaces together with the lagged crystallization of the inner core of the agglomerates results in the formation of hollow inner cavities after the exhaustion of interior materials. Thanks to the unique hierarchical structure and more accessible acid sites, the hollow hierarchical FER zeolite exhibits improved catalytic performance over the conventional one in the skeletal isomerization of 1‐butene to isobutene. [ABSTRACT FROM AUTHOR]

Here, we report the results of our 1H nuclear magnetic resonance study of the dynamics of water molecules confined in zeolites (mordenite and ZSM-5 structures) with hierarchical porosity (micropores in zeolite lamella and mesopores formed by amorphous SiO2 in the inter-lamellar space). 1H nuclear magnetic resonance (NMR) spectra show that water experiences complex behavior within the temperature range from 173 to 298 K. The temperature dependence of 1H spin-lattice relaxation evidences the presence of three processes with different activation energies: freezing (about 30 kJ/mol), fast rotation (about 10 kJ/mol), and translational motion of water molecules (23.6 and 26.0 kJ/mol for pillared mordenite and ZSM-5, respectively). For translational motion, the activation energy is markedly lower than for water in mesoporous silica or zeolites with similar mesopore size but with disordered secondary porosity. This indicates that the process of water diffusion in zeolites with hierarchical porosity is governed not only by the presence of mesopores, but also by the mutual arrangement of meso- and micropores. The translational motion of water molecules is determined mainly by zeolite micropores. [ABSTRACT FROM AUTHOR]

Hierarchical CsAlTi-BEA zeolites, due to the presence of a high concentration of Lewis acid sites formed by tetrahedrally coordinated Ti4+ ions in the zeolite structure and the neutralization of Brønsted acid sites by Cs+ cations, exhibit high catalytic activity in the tandem reaction of cyclic carbonate formation from styrene in the presence of tert-butyl hydroperoxide under CO2 pressure. The conversion of styrene into epoxide and further into carbonate increases with the content of titanium in the samples, while the selectivity for the cyclic carbonate increases with the content of cesium. [ABSTRACT FROM AUTHOR]

The creation of mesopore through desilication method is often followed by excessive silica dissolution, especially in high silica zeolite like ZSM-48, leading to crystal destruction. Herein, the mesopore was successfully generated through desilication method. Furthermore, the amount of mesopore was carefully controlled by adjusting Organic Structure Directing Agent (OSDA) contents in the zeolite framework via partial detemplation. Compared to their parents, the relative crystallinity remains the same for all the desilicated samples. Notably, the occluded OSDA within ZSM-48 may hold another role in desilication, which may affect the density and distribution of the acid site. Low-density polyethylene (LDPE) pyrolysis test exhibits improved catalytic performance for mesoporous samples, showed by the lower observed activation energy (Eobs). It further confirms the benefits of mesopore in enhancing the diffusion of the molecules.

Herein, desilication in increasingly harsh conditions was used to introduce mesopores into two different industrial ZSM‐5 catalysts (Si/Al ratio 11 or 29). For desilicated samples, increasing BET surface areas, mesopore volumes, and Si(OH) densities were noted. Brønsted acid site (BAS) densities increased upon desilication, as formerly inaccessible BAS in blocked pores became available, while the strength of the BAS was maintained upon desilication. Using KOH instead of NaOH as desilication agent can increase the mesopore volume generated per mass loss. The correlations between desilication strength and properties were largely determined by the parent Si/Al ratio. In general the introduced mesopores increased lifetimes in the ETA conversion, while additional Si(OH) groups introduced by desilication reduce the lifetime again. The lifetime is thus determined by a complex interplay of BAS density, improved reactant transport by introduced mesopores and Si(OH) density. There were no additional aromatics formed in desilicated samples during the conversion of ethanol and the samples were, in terms of aromatic yield, outperformed by a microporous parent. However, as result of longer lifetimes less ethanol was lost due to coke formation. It is concluded that desilication should be combined with other post‐modifications to increase aromatic production and lifetime. [ABSTRACT FROM AUTHOR]

Taking the green synthesis of hierarchical zeolites catalysts via mesop orogen-free as a starting point, the research progress and challenges of steam assisted synthesis, seed assisted synthesis, and kinetic regulated crystallization methods were summarized, and the crystallization nucleation mechanisms of the three methods were discussed; finally, the future research directions and development prospects of the synthesis of hierarchical zeolites via mesop orogen-free were prospected. [ABSTRACT FROM AUTHOR]

The catalytic properties of zeolites (microporous H-Y and granular micro-mesomacroporous H-Yh) and amorphous mesoporous aluminosilicate ASM in the reaction of 1,2-phenylenediamine with acetone were studied. The main reaction product was 2,2,4-trimethyl-2,3-dihydro-1H-1,5-benzodiazepine (selectivity up to 99% at a 94% conversion of 1,2-phenylenediamine). For the synthesis of 1,5-benzodiazepine, the most effective was 0.95H-Yh, a granular zeolite with a hierarchical porous structure. The catalyst demonstrated operational stability for three cycles. [ABSTRACT FROM AUTHOR]

Zeolites are widely used in petrochemical processes and refineries due to their well‐ordered microporous network and large surface area. However, the diffusion of reactants and products is hampered by the narrow microporous channels, causing limitations. To overcome this challenge, modifying the pore structure is crucial, and the chemical etching technique is a powerful tool that introduces mesopores and macropores, consequently enhancing mass transfer and accessibility. Diverse chemical etching methods have been invented, including exposure to both acids (organic/inorganic acids), alkali (organic/inorganic alkali), and neutral etchants (e. g., ammonium fluoride). This review summarizes and assesses the chemical etching methods and their relevance to catalytic cracking reactions, methanol to hydrocarbons (MTH), and biomass conversion. The potential of zeolites with modified pore structures has motivated researchers to develop novel methods to tackle the practical challenges associated with their applications. [ABSTRACT FROM AUTHOR]

The aim of this study was the synthesis, characterization, and catalytic application of new hierarchical materials modified with tantalum and vanadium ions. These materials exhibit secondary porosity, thus allowing the reactant molecules to access the active sites of the material while maintaining the acidity and crystallinity of the zeolites. Based on the results, these systems were found to be highly active and selective in the oxidation of cyclohexene. The performance of the catalysts was compared in oxidation processes carried out by conventional and microwave-assisted methods. Microwave-assisted experiments showed that in the presence of a hierarchical FAU zeolite containing Ta, long reaction times could be shortened with increased activity and selectivity under the same residual experimental conditions. [ABSTRACT FROM AUTHOR]

In this work, Mg-, Ti- and Zn-containing composites with hierarchical beta zeolites were synthesized using an impregnation method. Acid–base properties of the composites were investigated by benzene adsorption with Fourier-transform infrared (FTIR)-spectral analysis and the catalytic properties were evaluated in the Gewald reaction using cyclopentanone or cyclohexanone, malonodinitrile and sulphur. It was shown that Mg-containing composites provide high ketone conversion and selectivity towards the desired 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile. Zn- and Ti-containing composites were less selective in this process due to the lower strength and concentration of basic sites yielding 2-cyclopentylidenemalononitrile or 2-cyclohexylidenemalononitrile, respectively, as the main reaction products. [ABSTRACT FROM AUTHOR]

Hierarchical zeolites are aluminosilicates with a crystal structure, which next to the micropores possess secondary porosity in the range of mesopores and/or small macropores. Due to their ordered structure and additional secondary porosity, they have aroused great interest among scientists in recent years. Therefore, the present work concerns the synthesis and characterization of hierarchical zeolites with secondary mesoporosity, based on commercial zeolites such as MFI (ZSM-5), BEA (β) and FAU (Y), and modified with polysaccharides such as inulin, hyaluronic acid, and heparin. All materials were characterized by various analytical techniques and applied as a platform for delivery of selected drug molecules. On the basis of X-ray diffraction (presence of reflections in the 2θ angle range of 1.5–2.5°) and low-temperature nitrogen sorption isotherms (mixture of isotherms of I and IV type) additional secondary porosity was found in the mesopore range. Additional tests were also conducted to determine the possibility of loading selected molecules with biological activity into the aforementioned materials and then releasing them in the therapeutic process. Molecules with different therapeutic options were selected for testing, namely ibuprofen, curcumin, and ferulic acid with anti-inflammatory, potentially anticancer, antioxidant, and skin discoloration activities, respectively. Preliminary studies have confirmed the possibility of using hierarchical zeolites as potential carriers for bioactive molecules, as the loading percentage of active substances ranged from 39–79% and cumulative release for ibuprofen reached almost 100% after 8 h of testing. [ABSTRACT FROM AUTHOR]

Bisphenol A (4,4-isopropylidenediphenol, BPA) is an organic compound widely used, e.g., in the production of epoxy resins, plastics, and thermal receipt papers. Unfortunately, bisphenol A has negative effects on human health, which has prompted the search for an effective method of its removal. One of the most promising methods of its elimination is photocatalytic removal. The aim of this study was to design an effective method for the photocatalytic removal of bisphenol A using, for the first time, hierarchical zeolites and ruthenium ion-modified diatom biosilica, and silver as photocatalysts and optimization of the reaction conditions: temperature, pH, and composition of the reaction mixture as well as the electromagnetic wavelength. Additionally, for the first time, the electromagnetic wavelength that would be most suitable for the study was selected. All materials used were initially characterized by XRD and low-temperature nitrogen adsorption/desorption isotherms. Ruthenium ion-modified biosilica proved to be the most effective catalyst for bisphenol A removal, which occurred at a rate higher than 99%. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is a method used in the treatment of various diseases and represents a promising alternative to classical active substance release methods. According to the United States National Institute of Health, this therapy exploits the health-promoting potential of active substances, referred to as "photosensitizers", and radiation of specific energy. Curcumin is a natural "photosensitizer" that exhibits anti-inflammatory, antioxidant, and anti-cancer effects. Despite the novelty and innovation of PDT, the method is limited by the difficulty of using "photosensitizers" such as curcumin because of its low solubility in water, which hinders the clinical application of this technique. The use of a "photosensitizer" along with suitable carriers such as hierarchical zeolites is a potential strategy to offset this difficulty. Therefore, the objective of this study was to develop the photodynamic release of curcumin from hierarchical zeolites using the classical open-circuit release method and a novel closed-circuit release technique involving light of different wavelengths. Based on the obtained data, it was possible to unequivocally state that the speed and efficiency of curcumin release from the zeolite carrier is influenced by light with a wavelength in the range of 430–525 nm (blue-cyan-green). As much as 53.24% of the active substance was released upon light exposure. [ABSTRACT FROM AUTHOR]

Zeolites are of great interest to the scientific and industrial communities due to their interesting catalytic properties, such as high specific area, shape selectivity, and thermal and hydrothermal stability. For this reason, zeolites have been intensively studied and applied in several reactions of great industrial interest. However, the size of zeolite micropores may hinder the diffusion of bulky molecules in the pore system, limiting the use of zeolites in some reactions/applications that use bulky molecules. One way to address this limitation is to generate secondary porosity (in the range of supermicropores, mesopores and/or macropores) in such a way that it connects with the existing micropores, creating a hierarchical pore system. There are different hierarchical approaches; however, most are not economically viable and are complicated/time-consuming. Alkaline treatment has been highlighted in recent years due to its excellent results, simplicity, speed and low cost. In this review, we highlight the importance of alkaline treatment in the generation of secondary porosity and the parameters that influence alkaline treatment in different zeolitic structures. The properties and catalytic performance of hierarchical zeolites prepared by alkaline treatment are extensively discussed. It is expected that this approach will be useful for understanding how alkaline treatment acts on different hierarchical structures and will thus open doors to achieve other hierarchical zeolites by this method. [ABSTRACT FROM AUTHOR]

In this article, we report the results of research the formation of silicoaluminophosphate gels under changing gel aging conditions and the influence of an aluminum source (boehmite), characterized by different properties. The samples of initial gels were characterized by XRF, X-ray diffraction, MAS NMR 27Al and 31P, and scanning electron microscopy (SEM). Products of crystallization were characterized by XRF, X-ray diffraction, MAS NMR 27Al and 31P, scanning electron microscopy (SEM), N2-physical adsorption, and IR spectroscopy with pyridine adsorption. It has been established that the chemical and phase composition of aging gels and the products of further crystallization is conditioned by the size of the crystals and the porous structure of boehmite. Methods of management the morphology and secondary porous structure of SAPO-11, including the hierarchical porous structure, are proposed based on the use of boehmits characterized by different properties and changing the aging conditions of the initial gels. SAPO—based catalyst with a hierarchical porous structure showed excellent catalytic performance in dimerization of α-methylstyrene with a high degree of conversion and selectivity for linear isomers. [ABSTRACT FROM AUTHOR]

Three types of heterogeneous Fenton catalysts based on Fe-silicalite-1 were synthesized: (1) microcrystals with an average size of 5 μm (m-FeZ); (2) a hierarchical porous sample consisting of 100–200 nm nanocrystals prepared using a dry polystyrene latex template (h-FeZ); and (3) three hierarchical porous samples consisting of 30–50 nm nanocrystals prepared by steam-assisted crystallization (n-FeZ-1,2,3). The synthesis procedure for n-FeZ-1 and n-FeZ-2 included gel pretreatment at 90°C for 72 h. This pretreatment specifically involved introducing Fe into the reaction mixture after (for n-FeZ-1) and before (for n-FeZ-2) the gel aging. The samples were tested as heterogeneous Fenton catalysts in H2O2-mediated total oxidation of ethanol. The performance of the heterogeneous catalysts was compared with a conventional homogeneous Fenton catalyst. [ABSTRACT FROM AUTHOR]

This work aimed at the green synthesis of MWW zeolites using rice husk silica as an alternative raw material. It was also performed a post-synthesis desilication procedure with NaOH and CTABr aiming to obtain MWW zeolites with improved accessibility. The set of characterization techniques (XRD, 27Al MAS NMR, N 2 physisorption, SEM, TEM, and Pyridine-FTIR) revealed the phase purity and combined structure of micro-mesopores after desilication. The zeolites were evaluated as catalysts for polystyrene pyrolysis, producing benzene, toluene and ethylbenzene, besides styrene monomers, and dimers. Without any catalyst, polystyrene produces only styrene monomers, dimers and trimers. The desilication increases the amount of Brønsted and Lewis sites and the external area, catalyzing the production of polyaromatics and naphthalene derivatives. The activation energy decreased for the catalyzed reactions, reflecting other reaction pathways. [Display omitted] • Traditional and hierarchical green MWW zeolites with phase-purity were obtained. • Hierarchical MWW zeolite shows high S ext , V meso , and amount of acidic sites. • Green MWW zeolites produced aromatics and styrene monomers, and dimers by pyrolysis. • Hierarchization of green MWW zeolite increases polyaromatics derivatives production. • The activation energy decreases for the catalyzed reactions. [ABSTRACT FROM AUTHOR]

Developing biofuels with characteristics similar to current fossil fuels and compatibility with existing petroleum infrastructure (drop-in biofuels) is gaining prominence, aligning with global efforts towards carbon-neutral economies and decarbonization of the transportation sector. The originality of the current study involves two directions: first, the use of Chlorella sp. microalgae, cultivated under simulated post-combustion gas, as a raw material for producing drop-in biofuel precursors; and second, an investigation of the catalytic activity of hierarchical zeolites in the deoxygenation and denitrogenation of volatile pyrolysis products, enhancing hydrocarbon content. To accomplish this, a micro-furnace-type temperature-programmable pyrolyzer coupled with chromatographic separation and mass spectrometry detection (Py-GC/MS) was utilized to assess the upgrading effectiveness of distinct zeolites (faujasite-type, MFI-type, and mordenite-type) on volatile pyrolysis products. All tested zeolites effectively reduced oxygenated and nitrogenated compounds in the volatile pyrolysis products, enhancing their suitability for producing renewable fuel. This supports sustainable development goals by promoting affordable, clean energy and climate action. HMor yielded the highest hydrocarbon content (98.5 %), followed by HZSM-5 (97.6 %) and HY (85.5 %). Catalytic upgrading significantly increased the concentration of aromatic hydrocarbons (at least 66.3 %), with MFI-type zeolites showing the highest selectivity for valuable BETX compounds (benzene, ethylbenzene, toluene, xylene). Hydrocarbons in the gasoline range, with up to 91.7 %, predominantly align with the needs of the transportation fuel market. The principal component analysis illustrates that using MFI-type zeolites promoted the lowest selectivity for PAHs, constituting precursors for coke formation, which is advantageous for ensuring a longer catalyst lifespan. Our results are promising and encourage the conversion of microalgal biomass into renewable fuel additives for formulating drop-in biofuels, as hydrocarbon-rich volatile pyrolysis products could be directly integrated into existing biorefineries. Thus, microalgal biomass cultivated using flue gas as the carbon source can be viewed as a versatile and promising resource for producing renewable fuel additives, contributing to developing a sustainable, low-carbon future. [Display omitted] • Converting Chlorella sp. into aromatic fuel additives aligns with the green chemistry principle. • Eco-friendly bio-oil: upgrading with zeolite catalysts removes oxygenated and nitrogenated compounds. • Catalytic upgrading enriched the pyrolysis vapors with energy-rich gasoline-equivalent hydrocarbons. • HMor-type zeolites yielded results comparable to HZSM-5 but with higher selectivity for naphthalenes. • Study at TRL 3 sets the stage for further testing, advancing microalgae pyrolysis towards low-carbon biofuels. [ABSTRACT FROM AUTHOR]

Conversion of lignin biomass to bio-oil is currently a very industrially attractive strategy due to energy shortages and resource scarcity. Combining the advantages of mesoporous structure and strong acidity, hierarchical zeolites are considered the promising catalytic materials that have attracted great attention in the field of crude oil cracking. This work reviewed the effect of biomass-derived compounds as templates on the pore structure and acidity of the molecular sieves, and evaluated the bio-oil quality of these biomass-mediated hierarchical molecular sieves acting on lignin or lignin derivatives and their selectivity. The morphology, particle size, and properties of biomass templates are intimately tied to the secondary porosity of hierarchical zeolites, enabling the creation of unprecedented structural features and properties within the hierarchical zeolite. The resulting hierarchical zeolite exhibits exceptional crystallinity and superior mesoporous connectivity. In addition, hierarchical zeolites synthesized from biomass templates are competitive in improving the catalytic performance of lignin degradation. When the acid content is high enough, the mesopore content and pore size become key parameters in determining the catalytic efficiency to selectively improve the bio-oil quality of lignin and its derivatives. Finally, a systematic and comprehensive outlook on the opportunities and challenges of biomass-mediated hierarchical zeolites in the synthesis and conversion of lignin to bio-oil was presented from several perspectives. This review intends to provide theoretical guidance for green synthesis of hierarchical zeolites and to propose a feasible strategy for the conversion of lignin into bio-oil. • Biomass-mediated hierarchical zeolites possess excellent crystallinity and mesopore connectivity. • The mechanism of synthesis of biomass-mediated hierarchical zeolites was elucidated. • The pore structure of hierarchical zeolites is a key parameter for improving the quality of lignin bio-oil. • Biomass-mediated hierarchical zeolites reduce carbon footprint and promote clean energy production. • The quality of bio-oils can be improved by technology coupling or modified substrates. [ABSTRACT FROM AUTHOR]

Nanostructured materials can be utilised as potential catalysts for the production of platform chemicals and renewable biofuels from biomass derived molecules. The formation of hierarchical meso-microporous zeolites LTL and FAU via the surfactant assisted tandem acid-base post-synthesis treatment has been investigated by time-resolved in situ synchrotron SAXS and WAXS, providing a new insight into the mechanism of the mesostructuring treatment. Based on the results of TEM and in situ synchrotron measurements, a model for the formation of the core-shell structure of LTL zeolite crystals is proposed. Complementary evaluation using FTIR, NMR and nitrogen adsorption, in conjunction with reaction studies on mesostructured zeolites, demonstrated a potential for enhanced catalytic performance of these materials owing to the increased accessibility of the active sites and reduced transport limitations. [Display omitted] • Mesostructured zeolites LTL and FAU prepared using the surfactant-templated strategy. • Formation of hierarchical LTL and FAU investigated by time-resolved in situ synchrotron SAXS and WAXS. • The generation of the core-shell structure of LTL crystals is proposed. • The accessibility of active sites of the zeolite catalysts evaluated. [ABSTRACT FROM AUTHOR]

It is shown that H-forms of hierarchical aluminosilicate zeolites MOR, BEA, and MFI exhibit catalytic activity in the process of cracking n-hexane, while the introduction of nickel nanoparticles with an average size in the range of 2.3-5.5 nm changes the reaction direction towards isomerization. This opens up the prospects in creating catalysts based on Ni-containing zeolites for the reaction of the hydroisomerization of linear hydrocarbons. [ABSTRACT FROM AUTHOR]

Selective synthesis of limonene 1,2-diol from limonene epoxide was performed over hierarchical zeolites synthesized by a top-down strategy. Acid treatment of commercial zeolite (CBV-500) induced formation of mesopores, increased Si/Al ratio and stronger Brönsted acid sites with a low penalty on microporosity and crystallinity. The highest selectivity (78%) was obtained over USYAl0.1 zeolite that presented the highest content of Brönsted acid sites among the tested materials. Furthermore, residual water of the solvent promoted the synthesis of limonene 1,2-diol. Solvent-free conditions favored isomerization rather than hydrolysis of limonene epoxide. USYAl0.1 can be used up to 5 times for limonene epoxide isomerization. The addition of water to the reaction together with zeolite structure increases selectivity to the desired limonene-1,2-diol from limonene epoxide (up to 93%). Limonene 1,2-diol synthesis is thermodynamically feasible and it is favored with several non-polar solvents. Furthermore, DFT calculations suggested that limonene epoxide is adsorbed onto trans-configuration and that the trans-diaxal diol is formed by an attack of water in anti-position with respect to the location of the epoxide. [ABSTRACT FROM AUTHOR]

The possibility of crystallizing silicalite-1 (MFI) from the pore walls of as-synthesized MCM-41 via steam-assisted crystallization (SAC) was thoroughly investigated. A kinetic study was conducted through the impregnation of as-synthesized MCM-41 with the structure-directing agent tetrapropyl-ammonium hydroxide (TPAOH). Materials obtained after different SAC treatment times (1–288 h) were characterized by XRD, nitrogen physisorption at 77 K, TGA/DTA, and SEM. The achieved results allowed us to conclude that during SAC treatment, rapid destruction of the hexagonal mesophase occurs with the enlargement of mesopores, probably by their coalescence, until achieving non-porous amorphous silica. Only thereafter is the crystallization of the MFI phase evidenced through the development of micron-sized (>10 µm) MFI structured crystals. This study suggests the probable practical impossibility of even partial crystallization of the pore walls of mesoporous materials by SAC. [ABSTRACT FROM AUTHOR]

The catalytic properties of a microporous H-ZSM-5 zeolite and a granular hierarchical H-ZSM-5h zeolite in the synthesis of basic pyridines and quinolines have been studied. A specific feature of zeolite H-ZSM-5h is the absence of a binder in the granules and the presence of micro-, meso-, and macropores in the pore structure. The H-ZSM-5h sample comprises, in addition to crystals of the original zeolite, crystals with a size of 15–100 nm. The H-ZSM-5h sample exhibits a higher activity, selectivity, and stability than those of the microporous H-ZSM-5 zeolite in all studied reactions. [ABSTRACT FROM AUTHOR]

Friedel‐Crafts alkylation is one of the most important catalytic reactions in organic chemistry. Recently, hierarchical zeolites have exhibited superior catalytic performance in such liquid‐phase batch reactions. However, for practical application, it is of significance to evaluate their catalytic performance in Friedel‐Crafts fixed‐bed alkylation. In this work, we prepare hierarchical zeolites by post‐treatment, of which the structures are confirmed by XRD patterns and N2 adsorption‐ desorption tests. Then, a fixed‐bed reactor is employed to investigate their catalytic performance in series of benzylation reactions. The results indicate that hierarchical zeolites have superior anti‐deactivation ability in the benzylation reactions, especially when react with p‐xylene or mesitylene, the BA conversion maintained nearly 100 % in 300 min, much better than that of micropore zeolites. These results suggest that hierarchical zeolites have a potential industrial application for Friedel‐Crafts fixed‐bed alkylation than conventional zeolites. [ABSTRACT FROM AUTHOR]

The catalytic properties of a number of FAU (Y) zeolite samples (microporous zeolite H-Y, granular hierarchical zeolite H-Yh, zeolite H-USYh dealuminated by high-temperature steam treatment (HTST), and zeolite H-USYh a.t. dealuminated by HTST with subsequent acid treatment) in the oligomerization of 1-pentene. The samples were characterized by X-ray fluorescence analysis, X-ray powder diffraction analysis, low-temperature nitrogen adsorption–desorption, scanning electron microscopy, and temperature-programmed desorption of ammonia. It was determined that the total yield of pentene oligomers under the studied conditions (150°С, 10 wt % catalyst, 5 h) decreases in the order H-USYh a.t. (93%) ≈ H-Yh (93%) > H-Y (74%) > H-USYh (70%). The dealuminated sample H-USYh a.t., which has the largest mesopore volume, showed high stability in 1-pentene oligomerization at 180°C. The conversion of the monomer in its presence remained unchanged during 5 cycles of operation without catalyst regeneration, and the yield of pentene oligomers after 5 cycles decreased by 39%. Microporous zeolite H-Y lost activity already after the second cycle. [ABSTRACT FROM AUTHOR]

This work shows that hierarchical zeolites are promising systems for the delivery of biologically relevant hydrophobic substances, such as curcumin. The validity of using piperine as a promoter of curcumin adsorption was also evaluated. The use of pure curcumin is not medically applicable due to its low bioavailability and poor water solubility. To improve the undesirable properties of curcumin, special carriers are used to overcome these shortcomings. Hierarchical zeolites possessing secondary mesoporosity are used as pharmaceutical carrier systems for encapsulating active substances with low water solubility. This porosity facilitates access of larger reagent molecules to the active sites of the material, preserving desirable adsorption properties, acidity, and crystallinity of zeolites. In this work, methods are proposed to synthesize hierarchical zeolites based on a commercial FAU-type zeolite. Studies on the application and adsorption kinetics of curcumin using commercial FAU-type zeolite and hierarchical zeolites based on commercial FAU-type zeolite are also included. [ABSTRACT FROM AUTHOR]

The sequential fluorination-alkaline treatment protocol has been applied for the tailoring of siliceous ZSM-5 zeolite. The original spontaneous growth of mesoporosity in alkaline medium is altered due to the antecedent fluorination step. The outcome is demonstrated by the apparent delay in the mesoporosity growth, whose essential duration for the well-defined mesoporosity is therefore extended from 30 min to 60 min. A low fluorination level decelerates the mesoporosity growth, whereas a high fluorination level enables the achievement of the mesoporosity. These impacts are closely linked with the alteration to the states of Al sites as the function of fluorination level. Compared to the states of Al sites in the pristine and steamed zeolites, the electronic and steric consequences on the environment of Al species by fluorination is proposed for the interplay with the alkaline medium for the mesoporosity growth. [ABSTRACT FROM AUTHOR]

There is considerable interest in adjusting the acidity and pore architecture of zeolites. Herein, we present solventless incorporation of zirconium (∼2–10 wt.%) in a precursor and desilicated (0.2 and 0.4 mol L−1 NaOH) H‐ZSM‐5 zeolite. Infrared and UV‐vis‐DR spectroscopy confirmed the grafting of highly dispersed Zr in all the zeolites. XRD indicated the presence of ZrO2 in zeolites with higher Zr contents. The micropore volume of the precursor zeolite decreased by ∼10 %, suggesting the presence of Zr mainly on the external surface, while it decreased more than 20 % for the desilicated sample, suggesting Zr had access to the micropores at higher Zr contents. Infrared spectroscopy after pyridine adsorption provided evidence for the Brønsted and Lewis acid sites in all zeolites, but the Brønsted acid‐to‐Lewis acid site ratio decreased by >50 % depending on the Zr and NaOH concentrations. The presence of Zr critically changed the predominant nature of the acid sites of the desilicated zeolites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two mesoporous ZSM-5 (HS-ZSM-5 and ZSM-5@SBA-15) was synthesized for co-pyrolysis. • Effect of mesopore distribution in ZSM-5 was studied in NS and HDPE co-pyrolysis. • HS-ZSM-5 with an interior mesopore was superior in improving MAHs fraction. • The co-pyrolysis conditions were further regulated to maximize MAHs production. • The synergistic mechanism between NS and HDPE over mesoporous zeolites was studied. Co-pyrolysis of biomass and plastic was conducive to aromatics-rich bio-oil production, though the significance of zeolite mesopores in co-pyrolysis was still lacking and required further investigation. Herein, a conventional ZSM-5 and its two mesoporous deviants (hollow HS-ZSM-5 and core–shell hierarchical ZSM-5@SBA-15) were synthesized and utilized as catalysts in the co-pyrolysis of neem sawdust (NS) and high-density polyethylene (HDPE). Results showed that compared to ZSM-5, both the mesoporous zeolites enhanced aromatics production. And HS-ZSM-5 with an interior mesoporous cavity performed better in improving the monocyclic aromatic hydrocarbons (MAHs) fraction. An optimization of co-pyrolysis conditions (e.g. , HDPE percentage, catalyst loading, co-pyrolysis temperature) further improved the MAHs selectivity to 33.8 area%. The synergy between NS and HDPE over mesoporous zeolites was also compared. While the aromatization between short-chain olefins was dominant in aromatics production over ZSM-5@SBA-15, the Diels–Alder reaction between NS-derived furans and HDPE-derived olefins contributed more in that over HS-ZSM-5. [ABSTRACT FROM AUTHOR]

This study highlights novel, energy-efficient, environmentally friendly and less time-consuming methods to dealuminate zeolites, by forced convective steaming and use of molecular CO 2. Zeolites with comparable (or superior) physicochemical properties than those of traditional dealumination techniques were produced. All dealuminated zeolites were tested for the hydrocracking of high-density polyethylene, showing considerably high activity and selectivity for lighter oils, particularly gasoline. The forced convective steamed zeolite revealed to be the best, given its high number of silanol groups, acidity and porosity, and lower environmental impact. Furthermore, bi-functional Ni-loaded dealuminated zeolites showed good stability and ability to be regenerated. Therefore, it is possible to generate hierarchical zeolites by dealumination with physicochemical and catalytic properties comparable to their rival technologies, following green chemistry metrics. Given the relevance of hierarchical zeolites in sustainable routes to produce chemicals and fuels, the potential of application of these newly developed catalysts is highly promising and vast. [Display omitted] • Novel, energy and environmentally friendly, zeolite dealumination methods presented. • Environmental benefits of the greener routes assessed by life cycle analysis. • Greener hierarchical zeolites showed properties similar to traditional techniques. • Dealuminated zeolites showed notable performance for the hydrocracking of plastics. • High quality liquid products in the gasoline range were produced. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ball milling of MCM-22 generates a hierarchical catalyst with improved acid site accessibility. • Controlled ball milling can preserve more acid sites compared to chemical delamination. • Brønsted acid sites in micropores are more active for 4-propylphenol cracking. • The additional mesopores reduce the rate of deactivation by formation of carbonaceous deposits. The delamination of MCM-22 using shear forces in a vibratory ball mill, rather than chemical surfactants and sonication, is illustrated. The resulting material has comparable or improved physical properties compared to chemically delaminated MCM-22 without a significant loss of acid sites. The mechanical treatment affected the initial rate of 4-propylphenol cracking to phenol and propylene, a model reaction for lignin-derived aromatics, much less than chemical delamination. It also shows improved deactivation resistance for this reaction known to experience fast deactivation by pore blockage. [ABSTRACT FROM AUTHOR]

The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH4VO3 to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, 51V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)2(HO)V=O and (SiO)3V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HYdeSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)3V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C. [ABSTRACT FROM AUTHOR]

The activity, selectivity, and stability of microporous highly dispersed zeolites (H‐Y, H‐ZSM‐5) and granulated hierarchical zeolites (H‐Yh and H‐ZSM‐5h) were studied in the synthesis of quinolines by the Skraup reaction. Texture, porous structure, morphology of crystals, acidic properties were characterized by XRD, XRF, N2 adsorption‐desorption, SEM, NH3‐TPD methods. It was found that quinoline, 2‐ and 4‐methylquinolines are the main products in the reaction of aniline with glycerol in the presence of the studied catalysts. H‐ZSM‐5h and H‐Yh catalysts are more efficient than catalysts H‐ZSM‐5 and HY and provide a yield of quinolines to 72.4 (H‐ZSM‐5h) and 60.2 % (H‐Yh) at 450 °C, 0.2 h−1, the molar ratio of aniline:glycerol=1 : 3. The high activity and selectivity of hierarchical zeolites are due to the presence of meso‐ and macropores, as well as nanocrystals of 15–100 nm size. It was reported that hierarchical catalysts exhibit higher stability in the reaction compared with microporous zeolites. [ABSTRACT FROM AUTHOR]

Advanced biofuels are required to facilitate the energy transition away from fossil fuels and lower the accompanied CO2 emissions. Particularly, jet fuel needs a renewable substitute, for which novel production routes and technology are needed that are more efficient and economically viable. The direct conversion of bio-syngas into fuel is one such development that could improve the efficiency of biomass for jet fuel processes. In this work, bifunctional catalysts based on hierarchical zeolites are prepared, tested and evaluated for their potential use in the production of actual jet fuel. The bifunctional catalysts Co/H-mesoZSM-5, Co/H-mesoBETA and Co/H-mesoY have been applied, and their performance is compared with their microporous zeolite-based counterparts and two conventional Fischer–Tropsch Co catalysts. Co/H-mesoZSM-5 and Co/H-mesoBETA showed great potential for the direct production of jet fuel as bifunctional catalysts. Besides the high jet fuel yields under Fischer–Tropsch synthesis conditions at, respectively, 30.4% and 41.0%, the product also contained the high branched/linear hydrocarbon ratio desired to reach jet fuel specifications. This reveals the great potential for the direct conversion of syngas into jet fuel using catalysts that can be prepared in few steps from commercially available materials. [ABSTRACT FROM AUTHOR]