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This study proposed a strategy for the production of lactide from biomass-derived carbohydrate with excellent yield, involving sugar to racemic lactic acid conversion over Sn-containing Beta zeolite and racemic lactic acid to lactide conversion over H-Beta zeolite. Structural characteristics of the resulting lactide and extensive applicability for various substrates are also presented.

A core-shell nanozeolite@enzyme bi-functional catalyst is prepared by using nanozeolite β as acidic core and immobilized Candida antarctica lipase B (CALB) as enzyme shell for the purpose of dynamic kinetic resolution (DKR), and polydiallyldimethylammonium chloride (PDDA) is used as interlayer to compart core and shell. The activities of core and shell in bi-functional catalyst are modulated to achieve the matching between racemization and kinetic resolution (KR) rates in DKR, i.e., a slow racemization rate on core while a fast KR rate on shell. Nanozeolite β with intermediate SiO2/Al2O3 ratio provides proper acid amount for racemization step. A relatively thick layer of PDDA not only improves the activity of CALB by its coverage for surface acidic sites but also limits the accessibility and diffusion of substrate towards the acidic core. The CALB shell with larger immobilized amount and higher enzyme activity offers enhanced driving force of DKR process, leading to higher conversion, selectivity and yield. The preparation and activity modulation of core-shell catalyst provide an ideal method to improve the catalytic performance of bi-functional catalyst., (Copyright © 2014 Elsevier Inc. All rights reserved.)

A core-shell nanozeolite@enzyme bi-functional catalyst is constructed, which greatly improves selectivity and stereoselectivity of products in dynamic kinetic resolution of aromatic secondary alcohols compared with mixed catalysts, especially those involving small acyl donors.

A clear and deep understanding of protein adsorption on porous surfaces is desirable for the reasonable design and applications of porous materials. In this study, the effect of surface micropores on protein adsorption was systematically investigated by comparing adsorption behavior of cytochrome c (Cyto-c) and Candida antarctica Lipase B (CALB) on porous and non-porous nanozeolites silicalite-1 and Beta. It was found that micropore openings on the surface of nanozeolites played a key role in determining adsorption affinity, conformations, and activities of proteins. Both Cyto-c and CALB showed higher affinity to porous nanozeolites than to non-porous ones, resulting in greater conformational change of proteins on porous surfaces which in turn affected their bio-catalytic performance. The activity of Cyto-c improved while that of CALB decreased on porous nanozeolites. Recognition of certain amino acid residues or size-matching secondary structures by micropore openings on the surface of nanozeolites was proposed to be the reason. Moreover, the pore opening effect of porous nanozeolites on protein behavior could be altered by changing protein coverage on them. This study gives a novel insight into the interaction between proteins and microporous materials, which will help to guide the rational fabrication and bio-applications of porous materials in the future., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Four types of nanozeolite (NZ) particles (Silicalite S-1, BEA, Silicalite S-1-DT, and BEA-DT) with different physicochemical properties have been used for preparation of the new glucose oxidase (GOD) biosensor. Cyclic voltammetric studies were carried out with four different Pt/NZ electrodes, and it was found that the electrode prepared with BEA-DT NZ showed the highest electroactivity. These cyclic voltammograms (CVs) were compared with the CVs of four Pt/NZ-GOD electrodes. The presence of the oxidoreductase (GOD) on the electrode surface was the reason for the shifting of the potential peaks and corresponding currents. The magnitudes of the cathodic peak of Pt/NZ-S-1-GOD and Pt/NZ-S-1-DT-GOD electrodes had the highest values. The surface concentration (I*) of the adsorbed electroactive species (NZ-GOD) on the electrode was estimated according to the Brown-Anson model. The pH effect on the cathodic peak potential of Pt/NZ-GOD electrodes was investigated. The influence of different nanozeolites on sensitivity of GOD biosensors was studied. The most sensitive biosensor was obtained with NZ-S-1-DT, which had a porous surface, a higher degree of hydrophobicity, and a relatively high negative charge. The sensitivity of this electrode was 1.8044 μA L mmol(-1), the concentration limit was 0.8 mmol L(-1) glucose, and the linear correlation was from 2 to 18 mmol L(-1) glucose., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The extensive applications of nanoparticle materials in biomedical and biotechnological fields trigger the rapid development of nanotoxicology, because nanoparticles are reported to cause more damage than larger ones when human exposure to them. In the present manuscript, we prepared a series of zeolite nanocrystals with different frameworks, sizes, compositions and shapes, and provided the first report on their toxic difference. As our results, the toxicities of zeolite nanoparticles depend on their size, composition and shape when they are exposed to HeLa cells. The pure-silica nanozeolite silicalite-1 displays nontoxicity, but aluminum-containing nanozeolites, such as ZSM-5, LTL, and LTA, show a dose-dependent toxic manner. The different shapes of nanozeolites can lead to different cytotoxicities, while the influences of the surface charge differences of various nanozeolites on their toxicities are unconspicuous. More importantly, caspase-3 activity and LDH released assays showed that the toxic nanozeolites seem to induce cell necrosis rather than cell apoptosis by the damnification for the cell membranes. These results are expected to direct the applications of nanozeolites with different structures and shapes in biomedicine and clinic science., (Copyright © 2011 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

The electrochemical properties of cytochrome c (cyt c) immobilized on multilayer nanozeolite-modified electrodes have been examined in aqueous and nonaqueous solutions. Layers of Linde type-L zeolites were assembled on indium tin oxide (ITO) glass electrodes followed by the adsorption of cyt c, primarily via electrostatic interactions, onto modified ITO electrodes. The heme protein displayed a quasi-reversible response in aqueous solution with a redox potential of +324 mV (vs NHE), and the surface coverage (Gamma*) increased linearly for the first four layers and then gave a nearly constant value of 200 pmol cm(-2). On immersion of the modified electrodes in 95% (v/v) nonaqueous solutions, the redox potential decreased significantly, a decrease that originated from changes in both the enthalpy and entropy of reduction. On reimmersion of the modified electrode in buffer, the faradic response immediately returned to its original value. These results demonstrate that nanozeolites are potential stable supports for redox proteins and enzymes.

Given the importance of secreted proteins as a source for early detection and diagnosis of disease, secreted proteins have been arousing considerable attention. However, the analysis of secreted proteins represents a challenge for current proteomic techniques. One of the difficulties in secretomic study is to concentrate proteins from large volume of growth media, particularly, the low abundant and low molecular weight proteins (molecular weight <30 kDa). Herein, we describe a novel strategy for harvesting secretory proteins. In this approach, proteins secreted from the human hepatocellular carcinoma cell line were enriched by zeolite LTL nanocrystals, followed by 1-D SDS-PAGE for protein fractionation and then by LC-ESI-MS/MS for protein identification. In total, 1474 unique proteins were confidently identified, including 505 low molecular weight proteins, and covered a broad range of pI and molecular weight. Furthermore, this study not only offered an efficient and powerful method for the enrichment of secretory proteins but also allowed in-depth study of secretome of hepatocellular carcinoma cells. The reported work is expected to represent one of the most comprehensive secretomic analyses so far.

An on-chip microreactor was proposed toward the acceleration of protein digestion through the construction of a nanozeolite-assembled network. The nanozeolite microstructure was assembled using a layer-by-layer technique based on poly(diallyldimethylammonium chloride) and zeolite nanocrystals. The adsorption of trypsin in the nanozeolite network was theoretically studied based on the Langmuir adsorption isotherm model. It was found that the controlled trypsin-containing nanozeolite networks assembled within a microchannel could act as a stationary phase with a large surface-to-volume ratio for the highly efficient proteolysis of both proteins at low levels and with complex extracts. The maximum proteolytic rate of the adsorbed trypsin was measured to be 350 mM min-1 microg-1, much faster than that in solution. Moreover, due the large surface-to-volume ratio and biocompatible microenvironment provided by the nanozeolite-assembled films as well as the microfluidic confinement effect, the low-level proteins down to 16 fmol per analysis were confidently identified using the as-prepared microreactor within a very short residence time coupled to matrix-assisted laser desorption-time-of-flight mass spectrometry. The on-chip approach was further demonstrated in the identification of the complex extracts from mouse macrophages integrated with two-dimensional liquid chromatography-electrospray ionization-tandem mass spectrometry. This microchip reactor is promising for the development of a facile means for protein identification.

An enzymatic microreactor has been fabricated based on the poly(methyl methacrylate) (PMMA) microchchip surface-modified with zeolite nanoparticles. By introducing the silanol functional groups, the surface of PMMA microchannel has been successfully modified with silicalite-1 nanoparticle for the first time due to its large external surface area and high dispersibility in solutions. Trypsin can be stably immobilized in the microchannel to form a bioreactor using silica sol-gel matrix. The immobilization of enzyme can be realized with a stable gel network through a silicon-oxygen-silicon bridge via tethering to those silanol groups, which has been investigated by scanning electron microscopy and microchip capillary electrophoresis with laser-induced fluorescence detection. The maximum proteolytic rate constant of the immobilized trypsin is measured to be about 6.6 mM s(-1). Using matrix assisted laser desorption and ionization time-of-flight mass spectrometry, the proposed microreactor provides an efficient digestion of cytochrome c and bovine serum albumin at a fast flow rate of 4.0 microL min(-1), which affords a very short reaction time of less than 5 s.

An enzyme-immobilized nanozeolite-assembled electrode was prepared by controlled assembly of nanometer-sized Linder type-L zeolite (nano-LTL-zeolite) on an indium tin oxide (ITO) glass electrode surface, and subsequent immobilization of cytochrome c. Cyclic voltammetric (CV) and amperometric experiments showed that, relative to other reported electrodes, the enzyme-immobilized electrodes possess fast electron-transfer rates (2.2 s(-1)), a broad linear range (15-540 micromol L(-1)), a low detection limit (3.2 nmol L(-1)), a remarkably long lifetime (5 months), and high stability in the pH range 5-10. These characteristics could be due to the fact that nanozeolites assembled on ITO have high immobilization ability and facilitate interaction with enzymes. The function controllability of these enzyme electrodes, resulting from the facile manipulability of nanozeolite-assembled layers, may provide a possibility to rationally design biosensors.

Metal-ion-immobilized zeolite nanoparticles have been applied for the first time to isolate phosphopeptides from tryptic beta-casein digest; the phosphopeptides enriched on the modified zeolite nanoparticles could be effectively identified by MALDI-TOF-MS/MS.

Catalytic upcycling of polyolefins into high‐value chemicals represents the direction in end‐of‐life plastics valorization, but poses great challenges. Here, we report the synthesis of a tandem porous catalyst via a micelle cascade assembly strategy for selectively catalytic cracking of polyethylene into olefins at a low temperature. A hierarchically porous silica layer from mesopore to macropore is constructed on the surface of microporous ZSM‐5 nanosheets through cascade assembly of dynamic micelles. The outer macropore arrays can adsorb bulky polyolefins quickly by the capillary and hydrophobic effects, enhancing the diffusion and access to active sites. The middle mesopores present a nanoconfinement space, pre‐cracking polyolefins into intermediates by weak acid sites, which then transport into zeolites micropores for further cracking by strong Brønsted acid sites. The hierarchically porous and acidic structures, mimicking biomimetic protease catalytic clefts, ideally match the tandem cracking steps of polyolefins, thus suppressing coke formation and facilitating product escape. As a result, light hydrocarbons (C1‐C7) are produced with a yield of 443 mmol gZSM‐5−1, where 74.3 % of them are C3‐C6 olefins, much superior to ZSM‐5 and porous silica catalysts. This tandem porous catalyst exemplifies a superstructure design of catalytic cracking catalysts for industrial and economical upcycling of plastic wastes. [ABSTRACT FROM AUTHOR]

Zeolite synthesis under acidic conditions has always presented a challenge. In this study, we successfully prepared series of ZSM‐5 zeolite nanosheets (Z‐5‐SCA‐X) over a broad pH range (4 to 13) without the need for additional supplements. This achievement was realized through aggregation crystallization of ZSM‐5 zeolite subcrystal (Z‐5‐SC) with highly short‐range ordering and ultrasmall size extracted from the synthetic system of ZSM‐5 zeolite. Furthermore, the crystallization behavior of Z‐5‐SC was investigated, revealing its non‐classical crystallization process under mildly alkaline and acidic conditions (pH<10), and the combination of classical and non‐classical processes under strongly alkaline conditions (pH≥10). What's particularly intriguing is that, the silanol nest content in the resultant Z‐5‐SCA‐X samples appears to be dependent on the pH values during the Z‐5‐SC crystallization process rather than its crystallinity. Finally, the results of the furfuryl alcohol etherification reaction demonstrate that reducing the concentration of silanol nests significantly enhances the catalytic performance of the Z‐5‐SCA‐X zeolite. The ability to synthesize zeolite in neutral and acidic environments without the additional mineralizing agents not only broadens the current view of traditional zeolite synthesis but also provides a new approach to control the silanol nest content of zeolite catalysts. [ABSTRACT FROM AUTHOR]

Multiple and complex crystallization process of zeolite including complementary single‐molecule condensation and particle assembly, and alternately dominant nucleation and growth behavior, plays the critical role in zeolite crystallization but meanwhile makes us hard to study the respective effects. Herein, we strip nuclei from the synthetic solution and find that high‐ordered nucleus (subcrystal) is the premise to ignite high‐speed growth of zeolite crystal. The high‐ordered subcrystals with the size of only 6–10 nm possess regular aperture structure and microporous area similar to zeolite nanocrystal. Interestingly, a unitary oriented aggregation process of the subcrystals towards nanosheets is well observed and characterized where single‐molecule addition process is greatly repressed. If a wider range of zeotype nuclei can be expanded, a new synthetic strategy of zeotype materials with heterogeneous framework and active sites may be expected, which may novelize zeolite catalytic properties. [ABSTRACT FROM AUTHOR]

For zeolite catalysts, the regulation of active site and pore structure plays an important role in the enhancement of their catalytic performance. In this work, a one‐pot and organic template‐free co‐regulation route is proposed to straightforwardly synthesize basic mesoporous ZSM‐5 zeolites with adjustable alkaline‐earth metal species. The synthesis pathway combines two decisive strategies: 1) the seed‐induced interface assembly growth method and 2) the acidic co‐hydrolysis/condensation of aluminosilicate species and alkaline‐earth metal (e.g. Mg, Ca, Sr, or Ba) sources. It is interesting that the mesoporous structure was self‐evolved through particle‐attached seed‐interfacial crystallization without the assistance of any template. Meanwhile, the incorporation of alkaline‐earth metals species is homogeneous and highly dispersed in the solid products during the whole crystallization process, and finally generate the superior basicity. Catalysis tests of the as‐synthesized samples displayed their novel performance in the typical base reaction of Knoevenagel condensation, even for bulky substrates owing to the enhanced diffusion arising from the meso/microporous network. This finding opens new possibilities for facile, cost‐effective, and environmentally friendly synthesis of mesoporous high‐silica zeolites with tunable acid/base properties, and deepens our understanding of the particle‐attached crystallization. [ABSTRACT FROM AUTHOR]

Diffusion limitation in micropores of zeolites leads to a demand for optimization of zeolite morphology and/or porosity. However, tailoring crystallization processes to realize targeted morphology/porosity is a major challenge in zeolite synthesis. On the basis of previous work on the salt-aided, seed-induced route, the template effect of seeds on the formation of micropores, mesopores and even macropores was further explored to selectively achieve desired hierarchical architectures. By carefully investigating the crystallization processes of two typical samples with distinct crystal morphologies, namely, 1) nanocrystallite-oriented self-assembled ZSM-5 zeolite and 2) enriched intracrystal mesoporous ZSM-5 zeolite, a detailed mechanism is proposed to clarify the role of silicalite-1 seeds in the formation of diverse morphologies in a salt-rich heterogeneous system, combined with the transformation of seed-embedded aluminosilicate gel. On the basis of these conclusions, the morphologies/porosities of products were precisely tailored by deliberately adjusting the synthesis parameters (KF/Si, tetrapropylammonium bromide/Si and H2O/Si ratios and type of organic template) to regulate the kinetics of seed dissolution and seed-induced recrystallization. This work may not only provide a practical route to control zeolite crystallization for tailoring crystal morphology, but also expands the knowledge of crystal growth mechanisms in a heterogeneous system. [ABSTRACT FROM AUTHOR]

A clear and deep understanding of zeolite crystallization with the addition of organosilane is desirable for the reasonable design and preparation of hierarchical zeolites. Herein, the effects of different organosilanes on zeolite crystallization were systematically studied. It was found that organosilane plays the role of an inhibitor in the silanization-based zeolite preparation, and this inhibition effect was determined by its participation degree. An organosilane with a high participation degree can result in the prolongation of nucleation and growth periods of zeolite as well as the variation of product properties. More importantly, a dynamic participation pathway of organosilane is proposed, that is, the growth of zeolite is accompanied by the continuous removal of organosilane, leading to an increase of product crystallinity as well as the decrease of mesoporosity. This study gives a new insight into the role that organosilane plays in zeolite crystallization, which will help to direct the rational selection of organosilane and design of crystallization condition for the optimal synthesis of hierarchical zeolites. [ABSTRACT FROM AUTHOR]

Sowing the seeds: A sub‐micron single‐crystal‐like ZSM‐5 catalyst with enriched intracrystal mesopores is synthesized through a facile organic structure‐directing agent‐free and seed‐induced route. The special crystal structure leads to significantly improved catalytic activity, well‐preserved shape selectivity, and slow deactivation in the isomerization of o‐xylene to p‐xylene. [ABSTRACT FROM AUTHOR]

Thin zeolite films with thicknesses from several hundred nanometers to a few micrometers have been fabricated through electrophoretic deposition (EPD) in acetylacetone (Acac) and/or isopropyl alcohol (IPA). Various types of nanosized zeolites with different Si/Al ratios ranging from 1.6 (zeolite LTA) to nearly infinity (silicalite-1) were applied to prepare the EPD suspensions and showed different behaviors in EPD. The EPD rate of zeolite particles in non-aqueous medium was much higher than that in aqueous system mainly due to the high voltage applied, and consequently the whole process was usually completed in a few seconds. It was found that the Al/(Si + Al) ratios of zeolites and the chemical/physical properties of the EPD medium were two crucial factors which affected the thickness and density of the zeolite films prepared by EPD. The zeolite films fabricated through EPD could be effectively densified by secondary growth to prepare compact zeolite membranes. [Copyright &y& Elsevier]

Ultrathin nanozeolite films were prepared on the surface of Pt and glass carbon electrodes using nanoscale zeolite particles as building block via a layer-by-layer (LbL) technique or by a secondary growth method. Compared to conventional zeolite-modified electrodes, the nanozeolite film modified ones (nanoZMEs) prepared by these methods exhibit good membrane morphologies with controllable thickness in nanometer scale and large zeolite/electrode contact areas due to the nanoscale zeolite film attached directly to the electrode. Ag+, Cd2+ and Pb2+ were selected as examples to evaluate the electrochemical performance of nanoZMEs with designed thickness. With the same thickness of zeolite layer, nanoZMEs prepared by the LbL technique possess short preconcentration and response time, while nanoZMEs fabricated through the secondary growth method exhibit high accumulation ability and ion exchange selectivity. It is found that besides the inherent ion exchange selectivity of the zeolite layer, the transport rate of ions in the zeolite layer toward the electrode surface is an important factor that affected the electrochemical selectivity of the ZMEs. [Copyright &y& Elsevier]

Zeolite nanoparticles with various organosilanized surfaces have been synthesized in situby a one-step approach which provides not only a functionalized surface for diverse host–guest interactions but also an attractive path for preparation of monodispersed template-free zeolite nanoparticles. [ABSTRACT FROM AUTHOR]

Frontispiece: Co-hydrolysis and Seed-Induced Synthesis of Basic Mesoporous ZSM-5 Zeolites with Enhanced Catalytic Performance Keywords: basic zeolite; Knoevenagel condensation; mesoporous zeolite; non-classical crystallization; seed-induced synthesis EN basic zeolite Knoevenagel condensation mesoporous zeolite non-classical crystallization seed-induced synthesis 1 1 1 05/18/20 20200515 NES 200515 B Basic mesoporous ZSM-5 b with adjustable alkaline-earth metal species has been subtly synthesized with the "meeting" of seed and co-hydrolysis method. Basic zeolite, Knoevenagel condensation, mesoporous zeolite, non-classical crystallization, seed-induced synthesis. [Extracted from the article]

[Display omitted] It is a Holy Grail to realize the goal-oriented synthesis of zeotype crystals via direct thermodynamic/kinetic control of crystallization in the simplest inorganic system. Especially, the most commonly used counter cations (i.e., Na+ and K+) are in turn believed to play merely the role of balancing charges and stabilizing frameworks, which make the simple ion-based morphology/porosity control remain big challenges. We re-examined the role of Na+ and K+ to fine-tune the classical/nonclassical crystallization process in a seed-induced system with the simplest composition (Si/Al sources, inorganic alkali, and H 2 O), and proposed an "ion switch" strategy. By analyzing the multiple growth curves, tracking the precursor evolution, and observing epitaxial crystallization behavior, a distinctive "ion switch"-worked nonclassical mechanism was uncovered. By the "ion switch" strategy, ZSM-5 mesocrystals were fine-regulated with diverse architecture from single crystal to nanocrystallite assembly and intracrystal mesopore-enriched crystal. Such simple ions-controlled crystallization was achieved through microstructure heterogeneity of zeolitic building-blocks triggered by different counterions and their corresponding assembly behavior from oriented attachment to random deposition. Furthermore, this protocol can be extended to a wider H 2 O/SiO 2 range, mixed Na+/K+ systems, and other alkali metal ions from Li+ to Cs+, and ZSM-5 mesocrystals with extended morphologies can be obtained. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, a microwave-assisted two-step hydrothermal procedure was proposed successfully to prepare various zeolite nanocrystals (e.g., silicalite-1, ZSM-5, LTL, BEA and LTA) with controllable size, morphology and SiO2/Al2O3 ratio. The effects of the starting gel composition (such as water content, alkalinity and ratio of SiO2/Al2O3) as well as the hydrothermal synthesis condition (temperature and time) on the size of the zeolite nanocrystals have been studied in detail. It is found that high synthesis temperature and long reaction time benefit the growth of all the referred zeolite nanocrystals. However, the effects of the gel composition are very complex to different kinds of nanozeolites. For the nanozeolites crystallized in low alkalinity systems (e.g., ZSM-5, BEA and LTA), both increasing the alkalinity and decreasing the water content accelerate their nucleation process and thereby result in the decrease of their crystal size. On the contrary, for those prepared in high alkalinity systems (e.g., LTL and silicalite-1), an inversed trend could be observed. Moreover, the change of SiO2/Al2O3 ratio in the starting gel greatly affects the size of nanozeolite ZSM-5 and LTL, but slightly influences that of nanozeolite BEA. These results would provide a solid foundation to fully exploit the traditional and untraditional applications of various nanozeolites. [Copyright &y& Elsevier]

Abstract: ZSM-48 zeolite samples with a series of SiO2/Al2O3 ratios were synthesized in the hydrothermal system of Na2O–SiO2–Al2O3–H2N(CH2)6NH2 (HDA). The samples were characterized by X-ray powder diffraction, N2 adsorption, scanning electron microscopy, temperature-programmed desorption of ammonia, thermo-gravimetric analysis and chemical analysis. Both the OH−/SiO2 and SiO2/Al2O3 ratios played key roles for the formation of pure ZSM-48. C4-olefin cracking reactions were carried out on these ZSM-48 zeolites to produce propylene. Compared with currently used HZSM-5 zeolite, HZSM-48 zeolite exhibits a more excellent selectivity for the aimed olefins, especially for those with lower SiO2/Al2O3 ratios. The difference of catalytic performance of HZSM-48 and HZSM-5 zeolites for the cracking of C4-olefin can be attributed to their different acidities. The influences of reaction temperature and liquid hour space velocity on the catalytic performance of the HZSM-48 catalysts were investigated. The reasons for the deactivation of HZSM-48 zeolite in C4-olefin cracking reactions were also studied. [Copyright &y& Elsevier]

A mild alkaline modification treatment to both Lewis and Brønsted acid sites of Zr-Al-Beta zeolite, leading to its superior catalytic performance and resistance to coking in MPV reduction of furfural. • Zr-Al-Beta promoted by alkali-metal ions possess good stability and tolerance to carbon deposits. • Detailed characterizations demonstrated modification of alkali-metal ions on acid sites. • Alkaline ion modified Zr-Al-Beta high-selectively convert furfural under high concentration. • Alkaline treatment to zeolites was proved possibility of potential application. Zirconium-substituted zeolites prepared by post-synthetic procedure have demonstrated excellent performance in the upgrading process of biomass platform compounds owing to the unique Lewis acid character. However, many pressing questions still surround these materials, especially relating to specific conversion, catalyst stability and substrate scalability. In the present study, a simple alkaline treatment to the Zr-Al-Beta zeolite in alcoholic solution of alkali metal hydroxide was conducted. The modification of alkali-metal ions on both Lewis acid sites and Brønsted acid sites in Zr-Al-Beta was evidenced by XPS and FT-IR spectroscopy (CO and pyridine). The untreated materials displayed poor product selectivity and high coke deposit in the Meerwein-Ponndorf-Verley reduction of furfural and isopropanol; however, the treatment of alkali-metal ions promoted their catalytic performance with improved recalcitrance to deactivation and coking significantly. Both the type of alkali-metal ions and the concentration of alkaline solution influenced the catalytic performance, which were found to correlate to the acidity and textual properties. The optimum reaction result (97.3% yield of furfuryl alcohol at 99.6% conversion of furfural) can be obtained on 0.025 M-Na+-Zr-Al-Beta with high tolerance to the furfural concentration. [ABSTRACT FROM AUTHOR]

A series of Zr–Al-MWW zeolites with different Zr state and layer-stacking structure are successfully synthesized via direct grafting zirconocene dichloride onto the external silanols of three kinds of MWW zeolites, i.e. MCM-22 with multilayered structure, ITQ-2 (through layer delaminated route) and OL-MWW (by direct hydrothermal synthesis) with oligolayered structure. The structure, porosity and state of grafted Zr species are distinctly different among the three Zr–Al-MWW zeolites. Zr-OL-MWW possesses the highest content of single Zr atoms with an ideal micro-meso-macro pore system, while Zr-MCM-22 and Zr-ITQ-2 contain two kinds of Zr species (ZrO 2 clusters and single Zr atoms) coexisting in various proportions. The high dispersion of single Zr atoms on OL-MWW can be assigned to the large amount of external silanols of OL-MWW. The as-prepared three bi-functional Zr–Al-MWW zeolites are used for the cascade Meerwein-Ponndorf-Verley (MPV) reduction and etherification (ETH) reaction. Among them, Zr-OL-MWW shows dramatically higher conversion of cinnamaldehyde and yield of 1-cinnamyl 2-propyl ether than Zr-MCM-22 and Zr-ITQ-2, owing to the higher catalytic activity of Lewis acid centers from single Zr atoms, as well as more integrated framework Al sites as Brønsted acid centers with good accessibility. This study offers a simple and efficient strategy to construct Lewis-Brønsted acidic zeolites with exposed heteroatom sites and integrated framework structure, which will provide especial potential in the catalytic conversion of macromolecules. Bi-functional Zr–Al-MWW zeolites, i.e. Zr-MCM-22, Zr-ITQ-2 and Zr-OL-MWW were synthesized by direct grafting of zirconocene dichloride onto the external silanols of three zeolite matrixes, and applied in the Lewis-Brønsted cascade reaction. [Display omitted] • Bi-functional Zr–Al-MWW zeolites were synthesized by a direct grafting strategy. • Zr site state correlated to the matching between the amount of external silanols and the content of grafted Zr species. • Oligolayered MWW nanosheet with abundant external silanols produced more single Zr sites than multilayered MWW zeolite. • The ideal hierarchical porosity, integrated Al sites and exposed singe Zr sites provided superior catalytic performance. [ABSTRACT FROM AUTHOR]

Review: 122 refs. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical structured ZSM-5 zeolite of c-axis-oriented nanorods has been prepared by a zeolite-seed-assisted hydrothermal synthesis method without any type of mesoscale template. The final product has loose aggregation which consists of rod-like nanocrystals with widths of about 20–30nm, formed by the oriented aggregation model. The nitrogen physisorption suggested that the hierarchical structured ZSM-5 zeolite had higher mesopore volume and external surface area than the sample prepared conventionally. Due to the shortened microporous channel and opening mesopore, the prepared HZSM-5 catalyst presents high catalytic activity and stability for the alkylation of phenol with isopropanol. [ABSTRACT FROM AUTHOR]

Abstract: A series of MCM-22 zeolites were prepared by hydrothermal synthesis and subsequent dealumination by oxalic/citric acid leaching and steaming. The structural and acidic properties of the prepared samples were characterized by methods of XRD, ICP-AES, 27Al MAS NMR, pyridine-adsorbed IR and NH3-TPD. The results indicated that the sample treated by oxalic acid (MCM-22O) has the lowest aluminum content while the samples treated by steam have little change of the aluminum content. Unusually, sample MCM-22O possessed the strongest acidity among the dealuminated samples in spite of its lowest content of aluminum. It may be due to its least content of extraframework aluminum, which may lead to the weakening of acidity. Additionally, the prepared zeolites were mixed with a methanol synthesis catalyst and then applied in the process of syngas to dimethyl ether. Citric acid treated sample performed best with the least generation of byproducts, which have been well related to its structural and acidic properties. [Copyright &y& Elsevier]

Hollow zeolite microcapsules with spherical and various non-spherical shapes were fabricated through a novel strategy involving the crystallization of mesoporous silica (MS) particles. This conversion process was achieved by vapor phase transport treatment of MS particles which were pre-seeded by nanozeolite via the electrostatic assembly technique. The capsule shell was composed of closed packed zeolite crystals growing from the initial seeds by consuming the silica “nutrition” in the internal MS cores. The effects of seed size and seed type on the transformation of MS particles were investigated in detail. More importantly, guest species (e.g. Fe2O3 and Ag nanoparticles) which had been incorporated in the mesopores of the MS particles could be spontaneously encapsulated inside the generated capsules during the MS consumption process, thus, hollow zeolite capsules with functionalized interiors could be easily fabricated. [Copyright &y& Elsevier]