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A detailed investigation on the crystallization of offretite (OFF) zeolite templated by non-toxic cetyltrimethylammonium bromide (CTABr) is reported. Various hydrothermal synthesis conditions are prepared by systematically adjusting the synthesis variables, namely crystallization time, heating temperature and amount of reactants (SiO 2 , Al 2 O 3 , K 2 O, M 2 O (M = Na+, Cs+), CTABr and H 2 O) to investigate their effects on the crystal growth of OFF zeolite. It is shown that each variable has its profound influences on the crystallization process, which further affect the properties of final zeolite products (e.g. phase purity, morphology, crystal size). Unlike classical synthesis pathway using tetramethylammonium (TMA+) as organic template, the CTABr-templating approach successfully produces large OFF single crystals (framework Si/Al ratio = 4.11) with hexagonal prism shape (ca. 9.4 × 1.8 μm2) and smooth surface. Besides that, the OFF zeolite (81.9% conversion) also shows comparable or even higher catalytic performance than other zeolites reported in this work and other works in microwave assisted-Knoevenagel reaction of benzaldehyde and ethyl cyanoacetate, offering a sustainable and facile pathway for preparing zeolitic materials for advanced applications. [Display omitted] • Offretite (OFF) zeolite is synthesized using CTABr amphiphile-templating method. • Various synthesis conditions are studied. • Large OFF single crystals with hexagonal prism shape are successfully synthesized. • CTABr serves as both structure-directing agent and mesoporogen. • The OFF zeolite shows high activity in microwave assisted-Knoevenagel reaction. [ABSTRACT FROM AUTHOR]

Nanoscale zeolites are very attractive for advanced applications such as in catalysis, adsorption, supports, sensors and carriers. Green synthesis of these materials is highly appreciated aiming to increase product yield while chemical waste and production cost can be reduced. Here we report high-yield, low-cost and green synthesis of nanosized Cs-ABW zeolite by recycling and using the non-reacted mother liquors waste solutions produced from the hydrothermal Cs-ABW zeolite synthesis. The nanocrystalline Cs-ABW solid product of each successive batch was collected and characterized while the non-reacted mother liquors were recovered and re-used for subsequent synthesis of nanozeolites. The synthesized Cs-ABW zeolite nanocrystals from three subsequent cycles possessed fairly similar properties and they exhibited excellent catalytic performance in Henry (nitroaldol) reaction of benzaldehyde and nitroethane thanks to their basic sites, (Si–O–Al)–Cs+, located at the external surface of the zeolite. This approach hence suggests a low-cost and eco-friendly preparation of Cs-ABW zeolite nanocrystals since less chemical waste is disposed while the product yield can be significantly improved which are ideal for industrial scale-up process. [ABSTRACT FROM AUTHOR]

Cs–pollucite can be a potential solid base catalyst due to the presence of (Si-O-Al)−Cs+ basic sites. However, it severely suffers from molecular diffusion and pore accessibility problems due to its small micropore opening. Herein, we report the use of new organosilane, viz. dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC), as a promising pore-expanding agent to develop the hierarchical structure in nanosized Cs–pollucite. In respect to this, four different amounts of TPOAC were added during the synthesis of hierarchical Cs–pollucite (CP-x, x = 0, 0.3, 1.0, or 2.0, where x is the molar ratio of TPOAC) in order to investigate the effects of TPOAC in the crystallization process of Cs–pollucite. The results show that an addition of TPOAC altered the physico-chemical and morphological properties of hierarchical Cs–pollucite, such as the crystallinity, crystallite size, pore size distribution, surface areas, pore volume, and surface basicity. The prepared solids were also tested in Claisen–Schmidt condensation of benzaldehyde and acetophenone, where 82.2% of the conversion and 100% selectivity to chalcone were achieved by the CP-2.0 catalyst using non-microwave instant heating (200 °C, 100 min). The hierarchical CP-2.0 nanocatalyst also showed better catalytic performance than other homogenous and heterogeneous catalysts and displayed a high catalyst reusability with no significant deterioration in the catalytic performance even after five consecutive reaction runs. [ABSTRACT FROM AUTHOR]

In this study, ultra-small MCM-41 mesoporous solids (<30 nm) were synthesized using colloidal silica and cesium hydroxide as cheap silica source and mineralizer, respectively. Four samples with a SiO 2 /Al 2 O 3 ratio of 5, 20, 30 and ∞ (designated as CsM-5, CsM-20, CsM-30 and CsM-∞, respectively) have been prepared. The effects of SiO 2 /Al 2 O 3 ratio on the formation, physico-chemical and catalytic properties of CsMCM-41 nanoparticles were studied. The results show that incorporation of high content of Al atoms into the framework reduces the ordering of the mesostructure, and hence the porosity of the solids decreases. By using CsOH as mineralizer, the morphology and the size of CsMCM-41 were also tuned from 3-D nanospheres (CsM-5: 29 nm and CsM-20: 27 nm) to hollow nanospheres with very thin walls (CsM-30: 25 nm, CsM-∞: 20 nm) when Al content was decreased. The basicity of CsMCM-41 nanoparticles was also affected by the Al and Cs contents. Hence, their catalytic behavior in the base-catalyzed reactions such as aldol condensation of heptanal with benzaldehyde, and Perkin condensation of benzaldehyde with acetic anhydride was evaluated under microwave heating conditions. CsM-20 displays the best catalytic activities among the samples studied, achieving 87.2% conversion and 78.4% selectivity to jasminaldehyde under optimum reaction conditions, while it also shows comparable catalytic performance as NaOH homogeneous catalyst in the Perkin condensation reaction under non-microwave instant heating conditions. Image 1 • One-pot synthesis of ultra-small AlMCM-41 nanoparticles (<30 nm) is reported. • Colloidal silica and cesium hydroxide are used as cheap silica source and mineralizer. • The effects of Al incorporation on MCM-41 nanoparticles are studied. • The changes in morphological and porosity properties of nanosolids are observed. • The nanoparticles exhibit good catalytic performance in aldol condensation reaction. [ABSTRACT FROM AUTHOR]

Highly active hierarchical mordenite zeolite with micro/mesoporosity (TM- n) for selective synthesis of cyclic acetals via acetylation reaction is reported. The hierarchical zeolite is synthesized using soft-templating approach with variations in octadecyltrimethoxysilane (OTMS/Al 2 O 3 ratio, n = 0.2, 0.3 and 0.4) in precursor hydrogels. The results reveal that OTMS not only creates secondary mesoporosity in zeolite framework (larger mesopore volume, external surface area, average pore diameter), but also influences the crystallization process, altering the crystal morphology, crystallinity and Si/Al ratios. Among TM- n zeolites prepared, TM-0.3 hierarchical mordenite has the optimum OTMS amount incorporated while further increasing the OTMS amount leads to the formation of ANA/GIS intergrowth. Thanks to the accessible hierarchical porosity, reduced acidity and morphological effects, the TM-0.3 hierarchical mordenite exhibits excellent catalytic performance (84.1% conversion, TOF = 0.087 s−1, 61.5% dioxolane selectivity) in acetylation of glycerol and benzaldehyde (160 °C, 20 min) better than pristine mordenite. The catalyst is reusable for five runs with minimal loss of activity (TOF = 0.087 → 0.084 s−1), making it a promising catalyst for chemical productions involving bulky molecules. In addition, comparative catalytic tests with classical homogeneous and heterogeneous catalysts, including H 2 SO 4 , HCl, CH 3 COOH, H–Y, H-LTL, Na-X, Na-A, were performed. [Display omitted] • Hierarchical mordenite is crystallized using new organosilane via soft templating method. • Octadecyltrimethoxysilane (OTMS) serves as a mesoporogen. • OTMS governs crystallization process, affecting morphology, crystallinity and Si/Al ratio. • Hierarchical modernite catalyst is very active in acetalization of benzaldehyde and glycerol. • 84.1% conversion with 61.5% selective to dioxolane is recorded at 160 °C for 20 min. [ABSTRACT FROM AUTHOR]

An investigation of nanosized potassium aluminosilicate F-type zeolite (K-F, structure code EDI) converted from rice husk ash (RHA) is reported. The crystallization process was studied in an organic template-free system under microwave radiation at 100 °C and the evolution was followed by spectroscopy and microscopy techniques. The study indicated that the crystallization rate of K-F zeolite was significantly enhanced using microwave radiation. The zeolite started to nucleate at 0.5 min and flattened cuboid shaped K-F zeolite crystals (ca. 39 nm, Si/Al = 1.26) were formed after 2 min onwards. The nanocrystalline K-F zeolite exhibited good catalytic performance in solvent-free Aldol condensation reaction between benzaldehyde and heptanal, with ca. 75% reactant conversion and ca. 67% jasminaldehyde selectivity even after fifth cycle of reaction. [ABSTRACT FROM AUTHOR]

Alanine functionalized mesoporous SBA-15 (SBA-15-Alanine) as an active and selective catalyst for Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate is reported. The catalyst is prepared by 2-step grafting approach using (3-chloropropyl)triethoxysilane (CPTES) followed by dl -alanine. The XRD, TEM and N 2 adsorption results reveal that the mesoporous characteristic of SBA-15-Alanine is retained upon modification. Furthermore, the IR, TG/DTG, CHN and TPD analyses indicate the successful functionalization of alanine, leading to the formation of bifunctional mesoporous catalyst bearing both acidic (-COOH) and basic (-NH) sites. This catalyst exhibits acid-base cooperative effect and good catalytic performance in the Knoevenagel condensation between benzaldehyde with ethyl cyanoacetate (96.7% conversion) with 100% selective to ethyl α-cyanocinnamate under novel non-microwave instant heating conditions. The SBA-15-Alanine also shows stable catalytic performance with high reusability where insignificant decline in catalytic reactivity is observed after five successive cycles, thus suggesting a promising replacement of base catalysts in condensation reactions. [Display omitted] • Alanine was successfully immobilized onto SBA-15 framework. • SBA-15-Alanine had both basic (1.44 mmol g−1) and acidic (1.29 mmol g−1) amounts. • 100% selective to ethyl α-cyanocinnamate under novel non-microwave instant heating conditions. • SBA-15-Alanine shows stable catalytic performance with high reusability. [ABSTRACT FROM AUTHOR]

A detailed study on the formation of nanosized K-MER zeolite from a template-free hydrogel system is reported. By using a new recipe and bamboo leave ash (BLA) as a reactive silica source, the K-MER zeolite crystallization time has been shortened from 15 days to 6 h at 180 °C, enabling the investigation of induction, nucleation and crystal growth of nanoscale K-MER zeolite using spectroscopy and microscopy techniques. The resulting zeolite nanorods ((45.1 ± 14.5 nm length) × (3.9 ± 1.9 nm width)) have a Si/Al ratio of 2.31 and they tend to assemble in parallel forming bulkier bundle-like secondary structure ((728 ± 171 nm length) × (251 ± 49 nm width). The nanocrystals (84.3% conversion and yield, 100% selective to ethyl 2-cyano-3-phenylacrylate (ECP)) show better catalytic performance than other homogeneous base catalysts (92–99% conversion, 82–84% yield) in Knoevenagel reaction of benzaldehyde and ethyl cyanoacetate under non-microwave instant heating condition, thus offering an eco-friendly approach for synthesizing highly selective solid base catalyst for synthesizing pure fine chemicals. Image 1 • Zeolite K-MER nanorods are prepared free of organic template. • Nucleation and crystallization of nanozeolites in template-free hydrogel are studied. • Fully crystalline zeolite nanorods (ca. 45 × 4 nm2, Si/Al = 2.31) form after 6 h. • The nanocrystals are active in Knoevenagel condensation reaction. • High solid yield makes large-scale production of highly basic nanozeolite feasible. [ABSTRACT FROM AUTHOR]