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Abstract Cesium-aluminosilicate zeolite nanocrystals with ABW framework structure are synthesized free of organic template using hydrothermal approach. The crystallization process of Cs-ABW zeolite nanocrystals by varying the initial gel molar composition, heating temperature and crystallization time was studied. More detailed investigations of the formation of Cs-ABW nanozeolite using a reactive clear precursor hydrogel (4SiO 2 :1Al 2 O 3 :16Cs 2 O:160H 2 O) were then carried out. Fully crystalline Cs-ABW nanozeolites were obtained within 120 min at 180 °C and 22 bar, which is considerably faster and safer in comparison to the currently available method involving treatment at 695 °C, 1000 bar and 46 h. The Cs-ABW nanocrystals have grain shape morphology with a mean size of 32 nm and they do not agglomerate for long durations. The nanosized Cs-ABW zeolite has high alumina content (Si/Al ratio = 1.04). These nanocrystals can be prepared in high solid yield (ca. 82%) thus offering a promising route for large-scale production of highly basic zeolite nanoparticles. Graphical abstract Image 1 Highlights • Cs-ABW zeolite is prepared under low temperature (180 °C) and pressure (22 bar). • The nucleation and crystallization of nanozeolites in template-free hydrogel are studied. • Fully crystalline Cs-ABW nanocrystals are formed after 120 min. • The crystals (ca. 32 nm, Si/Al = 1.0) have grain shape morphology. • High solid yield offering large-scale production of highly basic zeolite nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: The nanoscale events in an organic-template-free gel leading to the formation of a FAU-type zeolite at 90°C were investigated by transmission electron microscopy (TEM). The study was complemented by ex situ X-ray diffraction (XRD), infrared (IR), 23Na 3Q-MAS NMR, N2 adsorption measurements and chemical analyses. It was found that the critical factor that triggers the growth process and mass transformation from amorphous into crystalline zeolite material is the attainment of a specific level of chemical evolution of the system, expressed in homogenization of the starting gel approaching stoichiometric FAU-type zeolite composition. This period was also marked by the formation and development of voids in the gel particles, containing highly hydrated material transformed later on into negative crystals. The evolution of these areas has been found to be an integral and noteworthy part of the chemical transformation of the gel that preceded the nucleation in the system. The observed transformations in the solid part of the system were induced by sodium, which progressively penetrated in the aluminosilicate matrix, breaking its structure and reorganizing the aluminosilicate species. The sodium behaviour was tracked down by a combination of local and bulk chemical analyses complemented by 23Na 3Q-MAS NMR study. During the initial stage of reaction a growth via propagation through the amorphous network co-existed with the typical solution-assisted hydrothermal crystallization. The later stages of development of the system followed the classical for zeolite-yielding systems crystallization that could be described by the autocatalytic nucleation. [Copyright &y& Elsevier]

A facile quantitative determination of the Si/Al ratio (SAR) in zeolite frameworks using IR spectroscopy is reported. From the linear regression analysis, the SAR for the medium-to-high Al content zeolites (1 < SAR < 5) correlates linearly to the corresponding intensity of the IR band at wavenumbers (950-1090 cm−1). This model has been validated with 19 zeolites with different SAR and different framework topologies (EDI, ABW, EMT, MER, LTL, LTJ, MOR, FAU, SOD, HEU, BRE, OFF, GIS, *BEA, MFI). The quantitative determination of the SAR of zeolites by IR spectroscopy is shown to be an alternative technique to the conventional ICP-OES and XRF spectroscopy techniques. Image 1 • Fast and simple method for determining the Si/Al ratio (SAR) of zeolite is developed. • The IR band at 970-1090 cm−1 can be used to determine the SAR of zeolites. • The model's accuracy is validated with ICP-OES, 29Si MAS NMR and XRF spectroscopies. • This method is applicable for medium-to-high Al content zeolites (SAR < 5). [ABSTRACT FROM AUTHOR]

• Carbamation of cellulose nanocrystals with TDI obtained at various surface DS. • Efficiency of grafting different Diels-Alder moieties onto CNCs surface assessed. • Thorough spectroscopy characterization of functionalized CNCs. The Diels-Alder reaction is a promising click chemistry for the design of advanced materials from cellulose nanocrystals (CNCs). Transferring such chemistry to cellulose nanocrystals requires the precise grafting of reactive Diels-Alder moeities under heterogeneous conditions without compromising the nanocrystals morphology. In this study toluene diisocyanate is used as a spacer to graft Diels-Alder moieties viz the furyl and protected maleimido moieties onto cellulose nanocrystals. A factorial experimental design reveals that reaction time and reactant molar ratio positively affect the grafting efficiency, as evidenced by FTIR and CHNS elemental analysis. The surface degree of substitution was analyzed via CHNS elemental analysis and XPS and found to range between 0.05 to 0.30, with a good agreement between the two techniques. 13C CP/MAS NMR confirmed that the grafted moieties and CNCs are intact after reaction. Side reactions were also observed and their impact on performing controllable click chemistry between cellulose nanocrystals is discussed. [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]

A simple and environmentally friendly route for the transformation of cellulose to porous carbon monoliths was developed. The procedure is based on freezing the cellulose solution in aqueous NaOH (−10 °C), followed by a direct regeneration of the frozen material in an ethanol bath and washing the alkaline with water. After atmospheric drying, the obtained cellulose monoliths composed mainly of cellulose II polymorph showed considerable macroporosity related to an ice-templating effect. During carbonization (500–900 °C, carbon yield >20%) the macroporosity (≈1–100 µm) was preserved together with monolithic character. The resulting monolithic carbons also showed significant microporosity, with micropore volume up to 0.25 cm3/g, depending on carbonization temperature. • A simple procedure of converting cellulose to monolithic porous carbon is developed. • The frozen cellulose-NaOH-water mixture is directly regenerated to a macroporous gel. • The gel carbonization leads to microporous and macroporous carbon monoliths. [ABSTRACT FROM AUTHOR]

Highly active and recyclable sulfated silica nanocatalyst for the synthesis of hexyl levulinate (HL) is reported. The sulfated catalysts, S n -BLA (n = 15 or 30 μL of H 2 SO 4 added), are prepared via sulfation upon amorphous bamboo leaf ash (BLA) under non-microwave instant heating condition (100 °C, 1.5 h). The spectroscopy and microscopy results reveal that silica nanoparticles (28 nm) with Brӧnsted (▪ bisulfate group) and Lewis (▪ sulfate group) acid sites are produced upon sulfation treatment. The sulfur containing acid groups covalently bound on the mesosilica surface are very active in the esterification of levulinic acid and hexanol where S30-BLA presents excellent catalytic activity (95.2% conversion, 98.0% selective to HL) at 90 °C for 7 min, which is far more superior than the previously reported catalysts. The S30-BLA catalyst is reusable with slight decrease in catalytic activity after six consecutive runs, suggesting an economical and environment-friendly route to biomass utilization. The bamboo leaves ash (BLA) biomass has been utilized as a silica source to synthesize sulfated catalyst for the conversion of levulinic acid into hexyl levulinate, a sustainable fuel additive. [Display omitted] • Highly active sulfated silica nanocatalyst for the synthesis of hexyl levulinate. • S30-BLA exhibits nanospherical shape with a size of 28 ± 7 nm. • Bisulfate and sulfate acid sites active in the esterification of levulinic acid. • Excellent catalytic activity at 90 °C for 7 min by S30-BLA. • Insignificant deterioration in catalytic reactivity after six consecutive 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]