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The crystallization mechanism of zeolites remains unclarified to date because of lack of effective techniques in characterizing the local structures of amorphous precursors under synthetic conditions. Herein

Small-pore zeolites are gaining increasing attention owing to their superior catalytic performance. Despite being critical for the catalytic activity and lifetime, postsynthetic tuning of bulk Si/Al ratios of small-pore zeolites has not been achieved with well-preserved crystallinity because of the limited mass transfer of aluminum species through narrow micropores. Here, we demonstrate a postsynthetic approach to tune the composition of small-pore zeolites using a previously unexplored strategy named pore-opening migration process (POMP). Acid treatment assisted by stabilization of the zeolite framework by organic cations in pores is proven to be successful for the removal of Al species from zeolite via POMP. Furthermore, the dealuminated AFX zeolite is treated via defect healing, which yields superior hydrothermal stability against severe steam conditions. Our findings could facilitate industrial applications of small-pore zeolites via aluminum content control and defect healing and could elucidate the structural reconstruction and arrangement processes for inorganic microporous materials.

AFX zeolite is a small-pore zeolite that has attracted significant attention because of its potential as a high-performance catalyst for the selective catalytic reduction of NOx by ammonia (NH3-SCR). Long time and high cost for the synthesis of AFX zeolite, however, limit the practical applications of this small-pore zeolite. Herein, we report an ultrafast synthesis route that can yield highly crystalline AFX zeolite in as short as 12 min. The ultrafast synthesis was realized on the basis of interzeolite conversion, where FAU zeolite was employed as a source of silicon and aluminum. Moreover, the addition of acid-leached seeds was found to be crucial for promoting the crystallization of AFX zeolite while effectively eliminating the formation of byproducts. Detailed studies of the original and acid-leached seeds revealed that acid leaching could cause structural alterations to the original seeds, thereby significantly enhancing the seeding effect. Secondary nucleation occurred when the acid-leached seeds were added, which is assumed to be one of the primary reasons for the accelerated crystallization rate. Based on the ultrafast synthesis, continuous-flow synthesis of AFX zeolite in 10 min was also demonstrated. The ultrafast and continuous-flow synthesis of AFX zeolite is expected to facilitate the large-scale production and broad applications of AFX zeolite.

ERI zeolite is a small-pore zeolite that has been rarely explored as a catalyst in the selective catalytic reduction of NOx with ammonia (NH3-SCR) as the performance has been considered to be limited by its insufficient hydrothermal stability. We herein report that a fast-synthesized ERI zeolite, which can be synthesized in only 2 h at a high temperature (210 °C), shows much enhanced hydrothermal stability than the conventional ERI zeolite due to the presence of less silanol defects. The fast-synthesized ERI zeolite with an optimal copper loading (equaling a Cu/Al ratio of 0.20) is demonstrated to be highly active in the NH3-SCR, which even rivals Cu-SSZ-13 – the benchmark NH3-SCR catalyst. Various characterization techniques are employed to characterize the copper species in the fast-synthesized ERI zeolite in order to understand its high hydrothermal stability and NH3-SCR activity. The results indicate that the copper species sitting at different locations exhibit variant hydrothermal stability and NH3-SCR activity, suggesting the importance of the interplay between the copper species and the zeolite host. With a deep understanding into the structure-activity relationship, this work presents that the fast-synthesized ERI zeolite holds potential to emerge as a robust NH3-SCR catalyst for emission control.

The STW-type zeolite is significantly attractive for developing novel enantioselective syntheses/separation of chiral compounds because it is the only chiral zeolitic microporous material whose enantioenriched synthesis has been achieved. Besides the conventional industries where zeolites are used, STW should have diverse industrial applications such as in the pharmaceutical and food industries. However, the toxic and caustic fluoride required for synthesizing STW severely hinders its commercialization by mass production. Here, we report the first example of fluoride-free STW synthesis, where the two roles of fluoride-formation of a zeolitic framework rich in tetravalent T-atoms and promotion of double 4-membered ring unit formation-were substituted by dry gel conversion and Ge addition, respectively. The obtained STW was highly crystalline, with a similar micropore volume and thermal stability as those of original fluoride-based STW. Our approach is promising not only for the fluoride-free synthesis of enantiomeric STW but also for general fluoride-free syntheses.

R2O3-B2O3 binary glasses (R denotes rare-earth elements or Y) were fabricated in a very wide composition region using a levitation technique. The maximum R2O3 content of light rare-earth compounds reached 63 mol % and decreased with a decrease in the ionic radius of R3+. The thermal, optical, vibrational, and structural properties were investigated, particularly for 50R2O3-50B2O3 glasses. The glass transition temperature increased with a decrease in the ionic radius of R3+, while the thermal stability was not affected by the glass composition. The packing density increased with a decrease in the ionic radius of R3+ due to lanthanoid contraction. Raman scattering and Fourier transform infrared spectra revealed that, in the rare-earth-rich glasses, no conventional three-dimensional networks consisting of corner-sharing BOn (n = 3 or 4) units existed because all B atoms were formed as isolated BO3 units. The simple environment around B atoms in the glasses led to additional IR transmittance regions, irrespective of the kinds of R. The total correlation functions obtained from high-energy X-ray diffraction measurements were analyzed using the pair-function method and compared with those of various RBO3 crystalline phases. It was suggested that the local structure around R resembles the ν-NdBO3-type crystal structure, and the O coordination number of R ranged from 6.5 to 7.7, smaller than that of the crystalline phase. The glass-forming ability depending on R was discussed based on the structural similarities between the melt, glass, and crystalline phases.

The development of inexpensive inorganic ion-exchangers for the purification of environmental pollutants is a social demand. Amorphous aluminosilicates with a relatively high homogeneous Al environment are prepared by a feasible co-precipitation method, i. e., mixing an acidic aluminum sulfate solution and basic sodium silicate solution, which exhibit excellent ion-exchange selectivity for Cs+ and Sr2+ . The Kd value for Sr2+ was comparable with that of zeolite 4A. The local structures and ion-exchange behavior of the amorphous aluminosilicates are systematically investigated. The ion-exchange property of the amorphous aluminosilicates can be tuned by changing the interaction between the exchangeable cation and the amorphous aluminosilicates. Also, the amorphous aluminosilicates can adsorb bulky cations that zeolites hardly adsorb due to the limitation of the miropore size of zeolites.

La2O3-Ga2O3 binary glass exhibits unusual optical properties owing to its high oxygen polarizability and low vibration energy. These optical properties include high refractive indices and a wide transmittance range. In this study, we performed classical molecular dynamics simulations on La2O3-Ga2O3 glass synthesized by an aerodynamic levitation technique. We have obtained structural models that reproduce experimental results, such as NMR, high-energy X-ray diffraction, and neutron diffraction. Based on our analysis, the structural features were clarified: 5-, 6-coordinated Ga, edge-sharing GaOx-GaOx polyhedral linkages, and oxygen triclusters. Additionally, the vibrational density of states was calculated by diagonalization of the dynamical matrix derived from the structural models and the results were compared with Raman scattering spectra. The mode analysis of the Raman spectra revealed that the principal bands at 650 cm-1 were mainly attributed to the stretching modes of the bridging and nonbridging oxygens. Meanwhile, the shoulder bands at the highest frequency of 750 cm-1 were mainly attributed to the stretching modes of the bridging oxygens and oxygen triclusters. The structural models obtained in this study well describe the characteristic local structures and vibrational properties of the La2O3-Ga2O3 glass.

Improving the stability of porous materials for practical applications is highly challenging. Aluminosilicate zeolites are utilized for adsorptive and catalytic applications, wherein they are sometimes exposed to high-temperature steaming conditions (∼1000 °C). As the degradation of high-silica zeolites originates from the defect sites in their frameworks, feasible defect-healing methods are highly demanded. Herein, we propose a method for healing defects to create extremely stable high-silica zeolites. High-silica (SiO

The local environment of aluminum in xLa2O3–(100 − x)Al2O3 (LA) and yY2O3–(100 − y)Al2O3 (YA) glasses is investigated using 27Al MAS NMR and Raman scattering spectroscopy in the glass forming range, i.e., 27 ≤ x ≤ 50 and 26 ≤ y ≤ 37.5, respectively. The results suggest that four-fold Al ([4]Al) is predominant in both glasses, with a content of approximately 90% in LA glasses and 60% in YA glasses; the remaining percentages are made up of five- ([5]Al) and six-fold ([6]Al) Al. In LA glasses, the fraction of [4]Al increases slightly with an increase in the La2O3 content, whereas, in YA glasses, the distribution of Al species does not change. Raman scattering spectroscopy reveals that, in LA glasses, the amount of non-bridging oxygen increases with an increase in x; moreover, [5]Al and [6]Al both increase with a decrease in x for x ≤ 40. Comparing with alkali earth aluminate glasses, we discuss the relationship between the fundamental structure of the AlO4 network and two parameters (the ratio of the number of oxygen atoms to that of Al and field strength).

A mild alkaline treatment with the assistance of surfactants has proved to be an effective way to introduce uniform mesopores into zeolites, yielding hierarchical materials with superior catalytic performance. Accelerating this process may open new opportunities in the scale-up of this new class of materials. In this study, we present an ultrafast surfactant-templating (UST) approach achieved within only a few minutes for the fast production of mesoporous ultra-stable Y (USY) zeolites by combining several favorable factors including high treating temperature, reactors featuring fast heating, and optimized reagent composition. Temperatures in the range of 150–220 °C yielded high quality materials, while too high temperatures (260–280 °C) produced inferior samples. The use of a flow reactor allowed for completing the UST in just one minute, which evidences the remarkable structural flexibility of zeolites that can reorganize in such a short time to accommodate a large amount of intracrystalline mesoporosity, without compromising their integrity or main properties. C. P. is grateful to the Chinese Scholarship Council and the Ministry of Education, Culture, Sports, Science and Technology, Japan for a MonbuKagakusho Scholarship. N. L. acknowledges funding from the University of Alicante, through the “Programa de captación y retención de talento” (ref. UATALENTO17-05). C. A Trujillo acknowledges the Universidad Nacional de Colombia and Ecopetrol for the support of the Laboratorio de Catálisis Heterogénea. Z. L. acknowledges the Japan Society for the Promotion of Science (JSPS) for financial support (a Grant-in-Aid for Young Scientists: 18K14049).

Designing efficient synthesis methodologies, without using expensive organic structure-directing agents (OSDAs), for industrially important zeolites is of high significance not only to realize thei...

An aging process, a pre-treatment at low temperature (typically, below 100 °C) prior to high temperature-hydrothermal treatments, can suppress impurity-phase formation, reduce synthesis time, control particle sizes, and so on. It is found that Na+ has the important role for dissolution and/or precipitation of aluminosilicate species in the aging process before the nucleation of LEV type zeolite. The dissolution of silicate species and the precipitation of aluminosilicate species are promoted during the aging when Na+ is present in the reaction mixture. The high energy X-ray total scattering measurement reveals that formation of 4-membered rings in precipitated aluminosilicate species. The induction periods in the hydrothermal treatments depend on formed aluminosilicates, and appropriate aging processes to form suitable aluminosilicates are considered to be necessary for the rational design of zeolite synthesis.

Post-synthesis treatment is an effective way to modify zeolites to acquire desirable properties. Here, we present an ultrafast post-synthesis treatment to prepare core-shell structured zeolite, which is composed of a ZSM-5 core and a silicalite-1 shell. The pure silica shell, which is aimed to remove the Bronsted acid sites associated with the framework Al on the external surface of aluminosilicate core, was formed unprecedentedly within several minutes by our method. Complementary techniques, such as XRD, TG/DTA, SEM, TEM, ICP, and XPS, were employed to verify the successful coverage of the silicalite-1 shell onto the ZSM-5 core. By adjusting the treating period, temperature, and reactant compositions, the thickness of the shell can be easily tuned. Further, this ultrafast process enabled the establishment of a continuous flow reaction system, which could allow the mass production of core-shell structured zeolite catalysts.

La2O3–B2O3 binary glasses were prepared by containerless processing using a levitation technique. The bulk glass-forming region in a B-rich composition was extended compared to that using conventional melt-quench techniques. Furthermore, additional glass formation was realized in an La-rich composition. The glass transition temperature and crystallization temperature of La-rich glasses are much higher than those of B-rich glasses. Both B- and La-rich glasses were colorless and transparent and had a high refractive index with low wavelength dispersion in the visible region. With the increase of the La2O3 content, the optical absorption edge in the ultraviolet (UV) region shifts to a long wavelength. An additional infrared (IR) transmittance window was observed in La-rich glasses, indicating that the La-rich borate glasses are expected to be used in optical components in a wide wavelength region. Local structural analyses using 11B magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and Raman scattering spectra revealed that every B-atom in La-rich glasses formed a planar trigonal BO3 unit and these BO3 units were entirely isolated. The evident difference from B-rich glasses where B-atoms formed a complex network structure with BO3 and BO4 units caused the characteristic physical and optical properties of La-rich glasses.

During AEI zeolite synthesis using acid treated FAU (AcT-FAU), we found the recrystallization of high-silica FAU with high crystallinity and Si/Al ratio of 6.1 using N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (DMDMPOH) after 2 h, followed by the crystallization of AEI via FAU-to-AEI interzeolite conversion at a longer synthesis time. In order to understand the formation mechanism of high-silica FAU and generalize its direct synthesis, we have investigated this synthesis process. An analysis of the short-range structure of AcT-FAU revealed that it has an ordered aluminosilicate structure having a large fraction of 4-rings despite its low crystallinity. The changes in the composition of the products obtained at different synthesis times suggested that DMDMP+ plays a certain role in the stabilization of the FAU zeolite framework. Moreover, the results of thermogravimetric analysis showed that the thermal stability of DMDMP+ changed with the zeolite conversion. To the best of our knowledge, this is the first study to clarify the structure-directing effect of DMDMP+ on FAU zeolite formation.

N2O is typically present as a trace gas in chemical processes, but its emission causes serious environmental issues. We herein demonstrate that ion-exchanged mordenite zeolites (framework code: MOR) can exhibit high capacities for N2O adsorption under ambient conditions. In particular, a natural MOR zeolite gives an adsorption capacity as high as 0.34 mmol-N2O per g-zeolite (1 atm, 25 °C), representing the best performing material among all zeolite-based adsorbents reported so far. The results contribute toward a comprehensive understanding of the structure–activity relationship and offer insights to establishing a zeolite-based adsorption system for enriching or removing N2O.

La

The inevitable use of FAU-type zeolites and long synthesis time bottleneck the mass production of SSZ-39 zeolite, a next-generation catalyst for selective catalytic reduction of NOx by ammonia (NH3-SCR). Herein, fast synthesis of SSZ-39 zeolites directly from colloidal silica and sodium aluminate is achieved with various reactant compositions, including a cost-effective low organic structure-directing agent-consuming condition and a scarcely reported KOH-containing condition. The reactant alkalinity and NaOH content are critical to the phase selectivity and fast crystallization, and partially replacing Na+ with K+ can eliminate the formation of gmelinite impurity. With optimized conditions, synthesis can be completed within 4 h without aging process in an autoclave, and even within 80 min by fast heating in a tubular reactor. Outstanding hydrothermal stability and NH3-SCR activity of the Cu-exchanged samples prove such fast and direct synthesis route a promising way to efficiently produce high-quality SSZ-39 zeolites for further applications.

Herein, we demonstrate a novel strategy of two-stage synthesis for the ZSM-5 nanoparticles that have tetrahedrally coordinated Al atoms in their framework. The particle size is significantly decreased at low temperatures during the synthesis; however, high temperatures are required for the successful incorporation of the Al atoms into the zeolite framework. Because of the rapid heating and cooling of the specially-designed tubular reactor with high thermal conductivity, suppression of the Ostwald ripening and incorporation of Al into the framework are simultaneously accomplished.

Zeolite Y is one of the most important catalysts that are used in catalytic processes such as fluidic catalytic cracking (FCC). This zeolite can be degraded during the FCC process, particularly under high-temperature steaming conditions; however, the degradation mechanisms have not been fully elucidated yet and previous studies have mainly focused on dealumination behaviors. In this study, we performed high-temperature treatments under steaming conditions to prepare a series of degraded zeolite Y samples, which were carefully investigated through techniques such as argon adsorption, high-energy X-ray total scattering, and transmission electron microscopy. A non-linear correlation between the crystallinity and micropore volume was observed. We propose that the degradation mechanism involved the formation of a dense amorphous layer, which the argon molecules cannot infiltrate into, on the surface of the crystals during high-temperature steaming treatment.

The Al location in zeolites can have massive influences on the zeolite properties because it directly correlates with the cationic active sites. Herein, the synthesis of IFR zeolites with controlled Al distribution at different tetrahedral sites (T sites) is reported. The computational calculations suggest that organic structure-directing agents (OSDAs) used for zeolite synthesis can alter the energetically favorable T sites for Al. Zeolite products synthesized under identical conditions but with different OSDAs are found to have altered fractions of Al at different T sites in accordance with the energies derived from the zeolite-OSDA complexes. Our finding thus provides evidence for the ability of OSDAs to direct Al into more energetically favorable T sites, thereby offering rational synthetic guidelines for the selective placement of Al into specific crystallographic sites.

The effect of the temperature and borate structure on the thermal conductivity of the molten CaO-B2O3 binary system was investigated. The thermal conductivity was measured from 1573 K to approximately the liquidus temperature using a transient hot-wire method, and was found to decrease with increasing temperature. The temperature dependence of the thermal conductivity in the molten oxide system was interpreted in terms of the lifetime of phonon-like excitations and Maxwell relaxation times. The short-range order borate structure was investigated through magic angle spinning (MAS) and triple-quantum MAS (3Q-MAS) NMR. Although the content of 4-coordinated boron was not significantly affected by the addition of CaO, structural changes associated with the fraction of 3-coordinated boron in ring and non-ring sites were observed. The Raman spectra showed that the intermediate range order borate structure was changed from boroxyl rings to chain-type metaborate units at higher CaO concentrations. The thermal conductivity decreased with decreasing BO1.5/CaO ratio, owing to the depolymerization of the borate network. This article is protected by copyright. All rights reserved.

We present herein an ultrafast, organic structure-directing agent (OSDA)-free synthesis of mordenite zeolite in a tubular reactor capable of fast heating. Using a typical Na2O/SiO2/Al2O3 system, the synthesis time was shortened to 10 min, which is much shorter than the time required by conventional methods (tens of hours). The addition of milled seeds, which have a smaller crystal size (200 nm), was found to be more effective in enhancing the crystallization than the micrometer-sized raw seeds (2 μm). The fast-synthesized mordenite possesses properties similar to those of mordenite synthesized by conventional methods in terms of crystallinity while having a comparably small crystal size. In addition, the effects of the alkalinity and SiO2/Al2O3 ratio of the initial reactant mixture on the crystallization rate were evaluated, but no significant effects were observed. On the contrary, the yield and SiO2/Al2O3 ratio of the product were dependent on the alkalinity and SiO2/Al2O3 ratio of the initial reactant mixture. Based on these observations, the crystallization behavior of mordenite, obtained from an ultrafast, OSDA-free synthesis method, is discussed.

La

Shortening the synthesis time of SSZ-16 (AFX type) zeolite from several days to 2 h has been achieved using an ultrafast synthesis route involving N,N,N′,N′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium (TEBOP) as an organic structure-directing agent (OSDA) in a tubular reactor assisted by seed crystals. Recently, copper exchanged SSZ-16 has been looked upon as one of the few equivalents to SSZ-13 for the selective catalytic reduction of NOx with ammonia (NH3-SCR) from automobile exhausts. Hydrothermal stability is one of the crucial properties for any zeolites that compete for automobile applications. All the samples prepared were analyzed using sophisticated physio-chemical techniques and those prepared from TEBOP were subjected to SCR of NOx reactions. The rapid crystal growth induced by high synthesis temperature bestowed the ultrafast prepared SSZ-16 with high crystallinity and hydrothermal stability as well as enhanced SCR of NOx activity even when aged at 800 °C. Compared to 1,1′-(1,4-butanediyl)bis-4-aza-1-azoniabicyclo[2.2.2]octane dibromide (DABCO), TEBOP was found to be desirable as an OSDA for high crystallinity and hydrothermal stability.

Silicoaluminophosphates are a class of crystalline microporous materials that have been widely used as catalysts and adsorbents. Two representative silicoaluminophosphates, SAPO-CHA (also called SAPO-34) and SAPO-AFI (also called SAPO-5), were synthesized in a tubular reactor within 10 and 5 min, respectively. The addition of a milled seed with small crystal size, the pretreatment of Al and Si sources by mechanical milling, and the employment of a high temperature condition were found to be the critical factors that contributed to the enhancement of crystallization rate of SAPO-CHA. The fast-synthesized SAPO-CHA possesses only isolated Si(OAl)4 species, indicating a great potential in catalytic applications. SAPO-CHA and SAPO-AFI usually appear as a pair of competing phases during the synthesis of SAPO-CHA/SAPO-AFI because of similarities in chemical compositions and formation conditions. Here, we show that, owing to the feature of rapid heating, the tubular reactor demonstrated itself as a facile and pre...

Methane exists in massive quantity on the Earth, and considerable efforts have been made to develop effective methods to convert chemically inert methane into value-added products. Recently, cobalt-exchanged ZSM-5 zeolite has been found to be a competent catalyst for non-oxidative methylation of benzene using methane as a methylation agent. Herein, cobalt-exchanged ZSM-11 zeolite, with close topological structure to that of ZSM-5 zeolite, was discovered to be capable of catalyzing non-oxidative methylation of benzene with methane for the first time. ZSM-5 and ZSM-11 zeolites both with Si/Al molar ratio of ca. 36 and 18 were synthesized. However, higher cobalt loadings were obtained on ZSM-11 zeolites, and cobalt-exchanged ZSM-11 catalysts displayed superior toluene production rates and turnover frequencies. In addition, low silica zeolite catalysts possessed higher methylation selectivity. Diffuse reflectance visible–near infrared spectra revealed that divalent cobalt cations on the ion exchange sites existed mainly in two different coordination states, and the cobalt cation on the α site, coordinating weakly to the framework oxygen atoms, was supposed to be the active site because of the positive correlation of its concentration and the methane activation performance. Since more α-type Co2+ could be created in ZSM-11 zeolites than in ZSM-5 zeolites with the same Si/Al molar ratio, it was concluded that cobalt-exchanged ZSM-11 catalyst was a promising candidate for the non-oxidative methylation of benzene with methane.

MFI zeolites exchanged with various cations have gained a great deal of attention as catalysts. Increase in the ion-exchange capacity of zeolites can improve their catalytic properties by introducing more active sites; however, the ion-exchange capacity of MFI zeolites is limited by maximum aluminum content in the structure. To improve the ion-exchange capability of the MFI zeolites beyond the upper limit of the aluminosilicate MFI zeolites, we propose herein an approach to incorporate Zn(ii) in the zeolitic framework, because Zn in the framework sites generates two negative charges per atom. Using zincoaluminosilicate gels prepared via co-precipitation, organic-free synthesis of zincoaluminosilicate MFI zeolites was achieved. The obtained zincoaluminosilicate MFI zeolites had high Zn contents comparable to those in the initial zincoaluminosilicate gels with both Zn and Al in the zeolite framework. In contrast, the use of conventional sources of Si, Al, and Zn resulted in zeolites with extra-framework zinc oxide species. The obtained Zn-substituted MFI zeolites were shown to possess higher ion-exchange capacity compared to aluminosilicate MFI zeolites. It was also revealed that the zincoaluminosilicate MFI zeolites have high affinity for the divalent cation compared to the aluminosilicate analog, likely due to the two negative charges in close proximity. Because of these higher ion-exchange efficiencies, especially for divalent cations, the obtained zincoaluminosilicate MFI zeolites are expected to be efficient platforms for several important catalytic reactions.

Thermal conductivity of molten Na 2 O–B 2 O 3 –SiO 2 system was measured at various temperatures and for different compositions using the hot-wire method. It was observed that thermal conductivity decreases at higher temperatures. The calculated one-dimensional Debye temperature implies that the change of the phonon mean free path dominantly affects the thermal conductivity in the present measurements. Using solid state 11 B and 29 Si MAS NMR, the structure of the oxide system was confirmed. A conflicting effect of the R ratio (Na 2 O/B 2 O 3 ) on thermal conductivity was observed. For R below 0.5, owing to the increase in 4-coordinated boron, thermal conductivity increases with increasing R ratio. However, for R above 0.5, thermal conductivity decreases with increasing R ratio as a result of the depolymerization of silicate networks and the increase in non-bridging oxygen (NBO). Finally, the effect of the K ratio (SiO 2 /B 2 O 3 ) on thermal conductivity was considered. A higher K ratio causes an increase in thermal conductivity as a result of the increase in the total amount of the silicate structure and a more effective mixing between silicon and 4-coordinated boron.

Nanoporous silicas having some periodicity, high surface area (up to 1230 m(2) g(-1)), and pore diameters near the boundary between micro- and mesopores are synthesized using aromatic compounds bearing anionic end-groups as novel structure-directing agents (SDAs) that can facilitate multiple interactions between SDAs, co-SDAs and silica frameworks orthogonally.

Zeolites containing Zn in their frameworks are promising materials for ion-exchange and catalysis because of their unique ion-exchange capabilities and characteristic Lewis acidity. However, expensive organic compounds often required in their synthesis can prevent their practical uses. Here, a facile organic-free synthesis route for new zincoaluminosilicate zeolites having MOR topology, in which both Zn and Al are substituted in the framework, is demonstrated for the first time. The use of homogeneous zincoaluminosilicate gels prepared by a co-precipitation technique as raw materials is vital for the successful incorporation of both Zn and Al into the zeolite frameworks as revealed by several characterization techniques including solid-state NMR and UV-vis spectroscopy, and ion-exchange experiments. The obtained zincoaluminosilicate zeolites had high Zn contents comparable to those in the initial zincoaluminosilicate gels. In contrast, the uses of conventional sources of Si, Al, and Zn resulted in zeolites with very low contents of framework Zn or zeolites with extra-framework zinc oxide-species. FT-IR measurements using probe molecules and ion-exchange experiments suggested that there are two different environments of Zn in the zeolite frameworks. The obtained zincoaluminosilicate zeolites showed a higher ion-exchange efficiency for divalent cations such as nickel compared to the aluminosilicate analog. It is expected that the present co-precipitation technique is efficient for the incorporation of Zn (and other metals) into a variety of zeolite frameworks. To show its extended applicable scope, the synthesis of zincoaluminosilicate *BEA zeolite is also demonstrated.

An alkanolamine, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, is used as an organic structure-directing agent (OSDA) to synthesize aluminophosphate (AlPO-5) and silicoaluminophosphate (SAPO-5...

In order to verify an alternative metallurgical process of phosphorus removal for solar grade silicon (SOG-Si), slag treatment of metallurgical grade silicon (MG-Si) was conducted followed by acid leaching in the present study. MG-Si containing certain amount of phosphorus and calcium was equilibrated at 1723 and 1773 K with several compositions of the CaO-CaF2 slags and phosphorus in molten silicon was confirmed to be removed into slag phase also by reducing reaction as a form of phosphide ion, P3-, in addition to the phosphate ion, PO43-. These contents were separately determined by a wet chemical analysis method developed by ourselves. Although the distribution ratio of phosphorus could not exceed the highest reported values of 3, subsequent leaching brought about considerably high fraction of P removal. The removal fraction of 95.6% was attained when 5 g of silicon was treated with 10 g of the slag at 1773 K followed by the acid leaching, which would be much higher than that expected by the ordinary oxidizing slag treatment. Although the possibility of reducing dephosphorization by slag treatment was clarified, more effective condition should be pursued by changing slag composition, calcium content of silicon, temperature, etc.

The hydrothermal synthesis of zeolites carried out in batch reactors takes a time so long (typically, on the order of days) that the crystallization of zeolites has long been believed to be very slow in nature. We herein present a synthetic process for ZSM-5, an industrially important zeolite, on the order of seconds in a continuous flow reactor using pressurized hot water as a heating medium. Direct mixing of a well-tuned precursor (90 °C) with the pressurized water preheated to extremely high temperature (370 °C) in the millimeter-sized continuous flow reactor resulted in immediate heating to high temperatures (240–300 °C); consequently, the crystallization of ZSM-5 in a seed-free system proceeded to completion within tens of or even several seconds. These results indicate that the crystallization of zeolites can complete in a period on the order of seconds. The subtle design combining a continuous flow reactor with pressurized hot water can greatly facilitate the mass production of zeolites in the future.

The local structure of phosphorus and silicon in the molten CaO–SiO2–PO2.5 slag system was investigated by magic angle spinning nuclear magnetic resonance (MAS-NMR). The 31P MAS-NMR spectra revealed that phosphorus was present primarily as the monophosphate complex ion PO43−, with a small amount of diphosphate ion also present. Their relative ratio to total phosphorus was independent of the phosphate concentration of the sample. In the case of the 29Si MAS-NMR, the mean number of the non-bridging oxygen atoms associated with tetrahedrally coordinated silicon decreased as the phosphate concentration increased at a fixed CaO/SiO2 ratio. This indicates that the nonbridging oxygen atoms around the silicon were replaced by bridging oxygen atoms around the phosphorus as the phosphate concentration in the samples increased. To elucidate the basicity dependence of the structure of slag, the relationship between the structure and optical basicity was also investigated. The relative ratio of Qn (Qn means the silicon atoms tetrahedrally bonded with “n” number of bridging oxygen atoms) strongly depends on the optical basicity. These optical basicity dependencies of the structures of phosphorus and silicon can be explained clearly by the basicity equalization concept (Duffy and Ingram, 1976) [12].

Organic structure-directing agents (OSDAs) have been widely used for the synthesis of zeolites. In most cases, OSDAs are occluded in zeolites as an isolated cation or molecule geometrically fitted within the zeolite cavities. This is not the case for zeolite beta synthesized by using tetraethylammonium (TEA(+)) cation as an OSDA, in which a cluster/aggregate of ca. six TEA(+) cations is occluded intact in the cavity (i.e., the channel intersection) of zeolite beta. The structure direction of TEA(+) in such a nontypical, clustered mode has remained elusive. Here, zeolite beta was hydrothermally synthesized using TEA(+) in the absence of other alkali metal cations in order to focus on the structure-directing behaviors of TEA(+) alone. The solid products formed throughout the hydrothermal synthesis were analyzed by an array of characterization techniques including argon adsorption-desorption, high-energy X-ray total scattering, Raman and solid-state NMR spectroscopy, and high-resolution transmission electron microscopy. It was revealed that the formation of amorphous TEA(+)-aluminosilicate composites and their structural, chemical, and textural evolution toward the amorphous zeolite beta-like structure during the induction period is vital for the formation of zeolite beta. A comprehensive scheme of the formation of zeolite beta is proposed paying attention to the clustered behavior of TEA(+) as follows: (i) the formation of the TEA(+)-aluminosilicate composites after heating, (ii) the reorganization of aluminosilicates together with the conformational rearrangement of TEA(+), yielding the formation of the amorphous TEA(+)-aluminosilicate composites with the zeolite beta-like structure, (iii) the formation of zeolite beta nuclei by solid-state reorganization of such zeolite beta-like, TEA(+)-aluminosilicate composites, and (iv) the subsequent crystal growth. It is anticipated that these findings can provide a basis for broadening the utilization of OSDAs in the clustered mode of structure direction in more effective ways.

We herein present a top-down methodology to prepare nanosized zeolites with tunable size by combining post-synthesis milling and fast recrystallization of several minutes (10 min for SSZ-13 and 5 min for AlPO4-5). A continuous-flow recrystallization process is demonstrated to further enhance the overall product efficiency.

Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region and its refractive index nd was as high as 1.94. The measured Young’s modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta5+ ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.