Synthesis Mixture Research Articles

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

Hydrothermal Crystallization of Bismuth Oxychlorides (BiOCl) Using Different Shape Control Reagents.

Bismuth oxychloride photocatalysts were obtained using solvothermal synthesis and different additives (CTAB—cetyltrimethylammonium bromide, CTAC—cetyltrimethylammonium chloride, PVP–polyvinylpyrrolidone, SDS–sodium dodecylsulphate, U—urea and TU—thiourea). The effect of the previously mentioned compounds was analyzed applying structural (primary crystallite size, crystal phase composition, etc.), morphological (particle geometry), optical (band gap energy) parameters, surface related properties (surface atoms’ oxidation states), and the resulted photocatalytic activity. A strong dependency was found between the surface tension of the synthesis solutions and the overall morpho-structural parameters. The main finding was that the characteristics of the semiconductors can be tuned by modifying the surface tension of the synthesis mixture. It was observed after the photocatalytic degradation, that the white semiconductor turned to grey. Furthermore, we attempted to explain the gray color of BiOCl catalysts after the photocatalytic decompositions by Raman and XPS studies.

Synthesis and Catalytic Performance of Aluminium‐containing Mesoporous, Spherical Silica Particles

AbstractA one‐pot synthesis of aluminium‐containing mesoporous silica particles (Al‐MSPs) utilizing polyvinyl alcohol (PVA) as steric stabilization agent is reported. PVA prevents particle agglomeration even when the ionic aluminium source is present in the synthesis mixture. Silicon and aluminium sources were utilised completely, resulting in high yield and easy adjustment of the Si/Al ratio. The Al‐MSPs showed a spherical morphology, high surface area and were active for the liquid‐phase Beckmann rearrangement of cyclohexanone to caprolactam.

The Double and Triple Role of L-(+)-tartaric Acid and Dimethyl Urea: A Prevailing Green Approach in Organic Synthesis

The deep eutectic mixtures (DESs), introduced as a novel alternative to usual volatile organic solvents for organic transformations, have attracted tremendous attention of the research community because of their low cost, negligible vapour pressure, low toxicity, biodegradability, recyclability, insensitivity towards moisture, and ready availability from bulk renewable resources. Although the low melting mixture of dimethyl urea (DMU)/L-(+)- tartaric acid (TA) is still in infancy, it is very effective as it plays multiple roles such as solvent, catalyst and/or reagent in the same pot for many crucial organic transformations. These unique properties of the DMU/TA mixture prompted us to provide a quick overview of where the field stands presently and where it might be going in the near future. To our best knowledge, no review dealing with the applications of a low melting mixture of DMU/TA appeared in the literature except the one published in 2017, describing only the chemistry of indole systems. Therefore, we intended to reveal the developments of this versatile, low melting mixture in the modern organic synthesis since its first report in 2011 by Köenig’s team to date. Hopefully, the present review article will be useful to the researcher working not only in the arena of synthetic organic chemistry but also to the scientists working in other branches of science and technology.

Hydrogen storage performance of methyl-substituted mesoporous silica with tailored textural characteristics

The present study reports a systematic analysis of morphology and hydrogen sorption capacity of mesoporous organic-inorganic silica prepared by varying the silica synthesis parameters. Cationic surfactants of different chain lengths and different proportions of functionalised precursors were introduced in the synthesis mixture. Improved hydrogen storage properties have been obtained, already below 20 bar, reaching a maximum storage capacity around 4.75 wt% at 80 bar. The textural characteristics were analysed by nitrogen sorption and small angle X-ray scattering, and the thermal stability has been characterized by thermogravimetric analysis. The materials show specific surface area between 400 and 700 m2/g and a weakly ordered mesoporosity induced by the short chain surfactant template.

Study of supramolecular self-assembly of pyridone and dihydropyridone co-crystal: Synthesis, crystal structure, Hirshfeld surface, DFT and molecular docking studies

Dihydropyridone is synthesized by the multicomponent condensation reactions (MCRs), followed by three different oxidation methods to synthesize pyridone. The 3-D self-assemblies of both the compounds were determined using the single-crystal X-ray diffraction method. Dihydropyridone products are found as a racemic mixture in synthesis and crystalized as co-crystal. Similar structural conformations are observed in both the compounds but stabilized with different non-covalent interactions. Hirshfeld surface analysis is done to analyze the various intermolecular interactions in both the structure. This study gives the clue of driving force in the self-assembly of molecules in crystal lattices. The propensity of inter-molecular contacts to construct the supramolecular assembly was further studied using DFT. The geometrical optimizations of both the compounds were done by the electronic structure method using density functional theory (DFT) to identify the active sites and explore the molecules' chemically reactive parameters. Further, both compounds were docked with Survivin Protein and Kinesin Eg5 protein to analyze the binding affinity with targeted protein.

Comment on “The solvent and zinc source dual-induced synthesis of a two dimensional zeolitic imidazolate framework with a farfalle-shape and its crystal transformation to zeolitic imidazolate framework-8” by C.-X. Jin et al., 2020, 49, 2437

In a recently published article Jin et al. described a new farfalle-shaped zeolitic imidazolate framework (ZIF-F) and its transformation into the well-known ZIF-8 in methanol. However, the shown powder diffraction patterns of ZIF-F are similar to another ZIF polymorph called ZIF-8dia, which has previously been synthesized from synthesis mixtures of different compositions.

Tuning Porosity of Reduced Graphene Oxide Membrane Materials by Alkali Activation.

The alkali-activation method allows for obtaining highly porous carbon materials. In this study, we explored the effect of activation temperature and potassium hydroxide concentration on the pore structure of reduced graphene oxide (rGO), as potential membrane material. Above 700 °C, potassium species react with the carbon plane of rGO to form nanopores. This activation process is deeply studied through DSC measurements and isothermal gravimetric analysis. The porosity of the formed materials consists of both micro- and mesopores, with most of the pores having a size smaller than 10 nm. The specific surface area and pore volume increase with increasing the potassium hydroxide/graphene oxide weight ratio (KOH/GO) up to 7 (897 m2∙g−1 and 0.97 cm3∙g−1, respectively). However, for a synthesis mixture with KOH/GO of 10, the specific surface area of the produced material drops to 255 m2∙g−1. The film-forming ability of the porous reduced graphene oxide (PRGO) was tested by drop-casting on porous silicon carbide substrates. In this case, continuous PRGO films were obtained only from dispersions with 5 g∙L−1 GO loading and KOH/GO ≤3. Such films can still have high specific surface area and pore volume (up to 528 m2∙g−1 and 0.53 cm3∙g−1) and main pore volume <10 nm. Hence, they can potentially be applied as membrane devices, but their scalability and their adhesion on the substrate under realistic filtration conditions still remain challenges.

Synthesis of corrosion-resistant MFI-type zeolite coatings by solid-conversion secondary growth without solvent

The hydrothermal synthesis for the fabrication of zeolite coatings is the most effective route and has been extensively studied, in which a large amount of water is indispensable to ensure efficient transport of nutrition. The disposal of waste solvent and chemicals remains a big challenge in practice and an alternative route is highly desired. Herein, we present an unprecedented solid-conversion secondary growth route for the fabrication of corrosion-resistant MFI-type zeolite coatings by mixing, grinding, and heating the mixture of silica source (Na 2 SiO 3 ·9H 2 O and SiO 2 ), template (TPABr) and acidity regulator (NH 4 Cl) without addition of water. The ZSM-5 zeolite seeded aluminum alloy 1060 plates were prepared by spray-coating method where water glass as a binder between seed and substrate was used to increase the adhesion of seeds to the substrate. The continuity of the coatings was investigated by manipulating the molar composition of synthesis mixture and the optimized molar composition is 1.0Na 2 SiO 3 ·9H 2 O: 1.19SiO 2 : 0.58TPABr: 1.82NH 4 Cl. The corrosion protection performance of MFI-type zeolite coatings on aluminum alloy plates was evaluated by a direct current polarization technique. The excellent corrosion-resistant was demonstrated in severely corrosive medium including in 0.5 M H 2 SO 4 aqueous solution and 0.5 M NaCl aqueous solution, which is comparable to the performance of zeolite coatings synthesized by hydrothermal synthesis. The features are also briefly discussed, which make this route highly attractive from a good perspective. ● The synthesis of MFI-type zeolite coatings by solid-conversion secondary growth route. ● Spray-coating was introduced to produce a continuous seed layer. ● Significant effect of the composition of synthesis mixture in solid-conversion method. ● MFI-type zeolite coatings are corrosion-resistant in severely corrosive medium.

Morphology, Activation, and Metal Substitution Effects of AlPO4-5 for CO2 Pressure Swing Adsorption.

Aluminophosphate, AlPO4-5, an AFI zeotype framework consisting of one-dimensional parallel micropores, and metal-substituted AlPO4-5 were prepared and studied for CO2 adsorption. Preparation of AlPO4-5 by using different activation methods (calcination and pyrolysis), incorporation of different metals/ions (Fe, Mg, Co, and Si) into the framework using various concentrations, and manipulation of the reaction mixture dilution rate and resulting crystal morphology were examined in relation to the CO2 adsorption performance. Among the various metal-substituted analogs, FeAPO-5 was found to exhibit the highest CO2 capacity at all pressures tested (up to 4 bar). Among the Fe-substituted samples, xFeAPO-5, with x being the Fe/Al2O3 molar ratio in the synthesis mixture (range of 2.5:100–10:100), 5FeAPO-5 exhibited the highest capacity (1.8 mmol/g at 4 bar, 25°C) with an isosteric heat of adsorption of 23 kJ/mol for 0.08–0.36 mmol/g of CO2 loading. This sample also contained the minimum portion of extra-framework or clustered iron and the highest mesoporosity. Low water content in the synthesis gel led to the formation of spherical agglomerates of small 2D-like crystallites that exhibited higher adsorption capacity compared to columnar-like crystals produced by employing more dilute mixtures. CO2 adsorption kinetics was found to follow a pseudo–first-order model. The robust nature of AlPO4-5–based adsorbents, their unique one-dimensional pore configuration, fast kinetics, and low heat of adsorption make them promising for pressure swing adsorption of CO2 at industrial scale.

Guided Crystallization of Zeolite Beads Composed of ZSM-12 Nanosponges

The direct route using a bifunctional amphiphilic structuring agent for the synthesis of hierarchical nanozeolites coupled with pseudomorphic transformation was used for the crystallization of hierarchized zeolite beads/hollow spheres composed of ZSM-12 (MTW structural-type) with nanosponge morphology. These beads/hollow spheres have the same average diameter of 20 µm as their counterpart amorphous mesoporous silica beads used as precursor in the starting synthesis mixture. The effects of synthesis parameters, such as stirring and treatment time at 140 °C, on the morphology, structure, and texture of the materials have been investigated using X-ray diffraction (XRD), N2 sorption, scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) techniques. Static conditions were found necessary to maintain the morphology of the starting amorphous silica beads. An Ostwald ripening phenomenon was observed with the increase in hydrothermal treatment time leading to the dissolution of the interior of some beads to form core shell beads or hollow spheres with larger crystals on the outer surface. These ZSM-12 beads/hollow spheres possess higher porous volume than conventional ZSM-12 zeolite powder and can be used directly for industrial applications.

Single-Step Synthesis of 2D Mesoporous C60/Carbon Hybrids for Supercapacitor and Li-Ion Battery Applications

Abstract The design of advanced carbon-based electrodes with unique electronic, electrical and textural properties is crucial for the development of high-performance energy storage devices. Here, we report on the fabrication of ordered mesoporous fullerene/carbon hybrids through nanotemplating approach by mixing the fullerene precursor in chloronaphthalene with different amount of sucrose using SBA-15 as a template. The characterization data reveal that the prepared materials exhibit an ordered structure with much better textural parameters than pure mesoporous fullerene. The surface properties can be controlled with the simple adjustment of the sucrose molecules in the synthesis mixture. The prepared materials are used as electrodes for supercapacitance and Li-ion battery applications. The optimized sample offers the specific capacitance of 213 F/g at 0.5 A/g which is much higher than that of activated carbon, MWCNT, ordered mesoporous carbon and mesoporous C60. The same sample also delivers the discharge capacities of 1299 mAh/g at 0.1 A/g, demonstrating the best Li-ion battery performance. These data reveal the importance of carbon coating on the mesoporous fullerene for energy storage devices as it facilitates the easy electron transport between the fullerene molecules and further supports the accessibility and diffusion of the electrolytes due to high specific surface area.

Dual template synthesis of SAPO-18/34 zeolite intergrowths and their performances in direct conversion of syngas to olefins

Abstract SAPO-18/34 zeolite intergrowths are synthesized in dual-template method with TEAOH and TEA as co-templates. The physical and chemical properties of the zeolite intergrowths are characterized by using XRD, ICP-AES, N2 adsorption-desorption, SEM, TEM and FT-IR. Moreover, the catalytic performances of the zeolite intergrowths in the conversion of syngas to olefins (STO) are studied by combining with ZnCrOx oxide to construct bi-functional catalysts. Equal amount of TEA and TEAOH in the synthesis mixture and proper silicon content (0.02

Milling Activation for the Solvent‐Free Synthesis of the Zeolite Mordenite

Milling by a planetary mill was applied as a pretreatment of a reagent mixture for the solvent‐free synthesis of the zeolite mordenite. This method was compared with both manual grinding and standard hydrothermal synthesis. The comprehensive characterization of the obtained products was complemented by thorough studies of activated synthesis mixtures before crystallization steps (by Magic Angle Spinning Nuclear Magnetic Resonance and Scanning Electron Microscopy). This experimental approach gave insight into processes behind the synthesis mixture activation by milling. The characteristics of solvent‐free zeolite product were comparable with material obtained by the classic hydrothermal route. The automated milling activation made the crystallization possible due to higher energetic impact in comparison to manual grinding. The solvent‐free process allowed minimization of the contribution of water to a role of the agent catalyzing silica transformation; as a result, less than 5 % water (compared to the classical synthesis) was necessary to perform the crystallization.

Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH3 oxidation.

The Synthesis of YNU-5 Zeolite and Its Application to the Catalysis in the Dimethyl Ether-to-Olefin Reaction.

During prior investigations of the synthesis of the novel zeolite YNU-5 (YFI), it was found that a very slight amount of an impurity phase contaminated the desired zeolitic phase. This impurity was very often ZSM-5 (MFI). The phase composition was determined to be sensitive to the water in the synthesis mixture, and it was possible to obtain a pure phase and also to intentionally generate a specific impurity phase. In the present work, trials based on the dimethyl ether-to-olefin (DTO) reaction using a fixed-bed downflow reactor were performed to assess the effect of the purity of YNU-5 on its catalytic performance. Dealuminated pure YNU-5 exhibited rapid deactivation due to coking at time on stream (TOS) values exceeding 5 min. Surprisingly, this deactivation was greatly suppressed when the material contained a trace amount of ZSM-5 consisting of nano-sized particles. The formation of ZSM-5 nanoparticles evidently improved the performance of the catalytic system during the DTO reaction. The product distributions obtained from this reaction using highly dealuminated and very pure YNU-5 resembled those generated by 12-ring rather than 8-ring zeolite catalysts. The high selectivity for desirable C3 and C4 olefins during the DTO reaction over YNU-5 is beneficial.

Crystallization of as-Mesocellular Silica Foam into Hierarchical TS-1 Zeolites by Conventional Hydrothermal and Dense-Gel Routes for Oxidation Reactions.

Crystallization of as-mesocellular silica foam (as-MCF) into TS-1 zeolites by conventional hydrothermal and dense-gel routes is reported. The TS-1 synthesized through the dense-gel route (TS-1-d) showed higher meso-macroporosity (0.311 vs 0.233 cm3/g), smaller particle size (130 vs 305 nm), and enhanced external surface area (86 vs 31 m2/g) than that synthesized under conventional hydrothermal conditions (TS-1-h). These might suggest that an organic template from as-MCF acted as mesoporogen in the dense-gel synthesis; however, segregation of the organic template and the synthesis mixture occurred in the conventional hydrothermal synthesis. The obtained TS-1 from the crystallization of as-MCF showed an enhanced framework Ti. The turnover frequencies (h–1) of TS-1-d toward hydroxylation of phenol and oxidation of dibenzothiophene (DBT) were 2 and 5 times, respectively, higher than those by TS-1-h. The DBT conversion by TS-1-d reached >99.0%, while it was only 63% by TS-1-h, suggesting the potential of TS-1-d for deep desulfurization of the fuels. Consequently, the crystallization of as-mesoporous materials through the dense-gel route is a promising approach to prepare TS-1 zeolites with smaller particle sizes and enhanced mesoporosity.

Creation of Al‐Enriched Mesoporous ZSM‐5 Nanoboxes with High Catalytic Activity: Converting Tetrahedral Extra‐Framework Al into Framework Sites by Post Treatment

AbstractZSM‐5 zeolite nanoboxes with accessible meso‐micro‐pore architecture and strong acid sites are important in relevant heterogeneous catalysis suffering from mass transfer limitations and weak acidities. Rational design of parent zeolites with concentrated and non‐protective coordination of Al species can facilitate post‐synthetic treatment to produce mesoporous ZSM‐5 nanoboxes. In this work, a simple and effective method was developed to convert parent MFI zeolites with tetrahedral extra‐framework Al into Al‐enriched mesoporous ZSM‐5 nanoboxes with low silicon‐to‐aluminium ratios of ≈16. The parent MFI zeolite was prepared by rapid ageing of the zeolite sol gel synthesis mixture. The accessibility to the meso‐micro‐porous intra‐crystalline network was probed systematically by comparative pulsed field gradient nuclear magnetic resonance diffusion measurements, which, together with the strong acidity of nanoboxes, provided superb catalytic activity and longevity in hydrocarbon cracking for propylene production.

Creation of Al-Enriched Mesoporous ZSM-5 Nanoboxes with High Catalytic Activity: Converting Tetrahedral Extra-Framework Al into Framework Sites by Post Treatment.

ZSM‐5 zeolite nanoboxes with accessible meso‐micro‐pore architecture and strong acid sites are important in relevant heterogeneous catalysis suffering from mass transfer limitations and weak acidities. Rational design of parent zeolites with concentrated and non‐protective coordination of Al species can facilitate post‐synthetic treatment to produce mesoporous ZSM‐5 nanoboxes. In this work, a simple and effective method was developed to convert parent MFI zeolites with tetrahedral extra‐framework Al into Al‐enriched mesoporous ZSM‐5 nanoboxes with low silicon‐to‐aluminium ratios of ≈16. The parent MFI zeolite was prepared by rapid ageing of the zeolite sol gel synthesis mixture. The accessibility to the meso‐micro‐porous intra‐crystalline network was probed systematically by comparative pulsed field gradient nuclear magnetic resonance diffusion measurements, which, together with the strong acidity of nanoboxes, provided superb catalytic activity and longevity in hydrocarbon cracking for propylene production.

Separation Processes to Provide Pure Enantiomers and Plant Ingredients.

Enantiomer separation and the isolation of natural products from plants pose challenging separation problems resulting from the similarity of molecules and the number of compounds present in synthesis or extract mixtures. Furthermore, limited theory is available to predict productivities for possible alternative separation techniques. The application and performance of chromatography- and crystallization-based processes are demonstrated for various case studies devoted to isolating valuable target compounds from complex initial mixtures. In all cases, the first emphasis is set to determine the process-specific phase equilibria to identify feasible process options. For all examples considered, yields and productivities are evaluated and compared for different scenarios. Guidelines to approach and solve similar separation tasks are given.