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Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and steam-assisted-crystallization method is used to synthesize hierarchically porous zeolite ZSM-5 with varied Si/Al malar ratios. X-ray diffraction (XRD), N2 physisorption, NH3-temperature programmed desorption (TPD), scanning electronic microscopic (SEM) measurement and Fourier transform infrared (FT-IR) are employed to characterize the structure and acidity of both hierarchically porous zeolites and their conventional counterparts. The method is found to be applicable to ZSM-5 with molar ratios of Si/Al from 20 to 180. The ZSM-5 zeolites are used as catalysts for benzene methylation at 460 °C to investigate the effect of additional porosity and Si/Al ratios. At low Si/Al ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. It is found that hierarchical porosity markedly enhances the utility of zeolite and the selectivity towards xylenes via improved mass transport at higher Si/Al ratios. Under an optimized hierarchical ZSM-5 catalyst, xylene selectivity reaches 34.9% at a Si/Al ratio of 180.

Average diffusivity linear driving force (AD-LDF) and concentration-dependent diffusivity linear driving force (CDD-LDF) approximations are introduced to simplify the precise model describing the concentration-dependent micropore diffusion in bidisperse sorbents, and are compared with the precise model in predicting the dynamics of a sorption process under two different perturbations (i.e., step change perturbations and sinusoidal wave perturbation) with different concentrations imposed at the exterior surface of the bidisperse sorbent. The performance of the two approximations is validated by the precise model and experiments. The AD-LDF performs better in step adsorption and CDD-LDF does better in step desorption. Under sinusoidal wave perturbation, the CDD-LDF performs better. The different levels of consistency of the two approximations with the precise model are attributed to the different definitions of the diffusivities.

A bottom-up approach is developed to synthesize Sn, Ce, Mn, or Co promoted NixMg1−xO catalysts enclosed by Tasker III type polar (1 1 1) facets. Sn and Co are evenly distributed on NixMg1−xO, whereas Ce and Mn segregate as separate oxides. X-ray diffraction (XRD), N2 physisorption, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopic (TEM) measurements are carried out to understand the structure/composition of both fresh and spent catalysts. H2-Temperature Programmed Hydrogenation (TPH), XPS and Thermogravimetric analysis (TG) are employed to elucidate the types of coke formed on the spent catalysts. Mn does not show obvious enhancement to catalytic stability towards Cβ formation, and a lower activity is observed as it separates from catalyst surface and causes agglomeration of NixMg1−xO(1 1 1) platelets. Cβ and whisker carbons are found for Ce-promoted NixMg1−xO(1 1 1) catalyst, for Ce segregates as CeO2. Both Sn and Co are distinguished to enhance the coke-resistant properties of NixMg1−xO catalyst in CH4-CO2 dry reforming, as they inhibit the formation of Cβ. Activation energy (Ea) measurements show that Sn lowers the activity of Ni surfaces, while Co does not passivate the intrinsic activity of Ni surfaces. Under more critical reaction conditions with CH4/CO2 ratio of 3 and diluent gas free, Co is found to enhance the lifespan of NixMg1−xO (1 1 1) catalyst.

Synthesis of hierarchically porous zeolites has drawn intensive interest because of their improved catalytic performance. It is highly desirable to find ways to generate these materials in a low-cost and scalable way for their commercial applications. A solvent evaporation route has been established to synthesize hierarchically porous titanosilicalite-1 (TS-1). In the protocol, hexadecyltrimethoxysilane was added to an ethanolic solution of titanium isopropoxide, tetraethyl orthosilicate and tetrapropylammonium hydroxide, i.e. the embryo solution of TS-1. The solution was subjected to solvent evaporation-induced self-assembly to afford an ordered dry gel. Subsequent steam-assisted crystallization converted the dry gel into a hierarchically porous TS-1. X-ray powder diffraction (XRD), UV–visible diffusive reflectance spectroscopy, N2 physisorption and electron microscopic characterizations have been employed to elucidate the structure. Ti is incorporated into the tetrahedral sites of the MFI structure and mesopores around 20 nm penetrating the crystalline framework are formed. Hexadecyltrimethoxysilane plays a key role in creating mesopores as well as increasing the crystal size. The hierarchically porous TS-1 exhibits improved activity in styrene oxidation and phenol hydroxylation. Copyright © 2014 John Wiley & Sons, Ltd.

The epichlorohydrin-N,N-dimethyl-1,3-diaminopropane copolymer (PCA) has been introduced for the first time as a meso-template to successfully synthesize a hierarchical ZSM-5 zeolite (PCA-ZSM-5) with mesopores of 7–50 nm in diameter by using small-sized nanoblocks. However, when its structural analogue epichlorohydrin–dimethylamine polyamine (PCS) is used, the obtained ZSM-5 zeolite (PCS-ZSM-5) has lower mesoporosity than ZSM-5 nanocrystallite aggregates (NCA-ZSM-5) synthesized without the meso-template. The templating effect of the two employed cationic polymers (PCS and PCA) on the synthesis of hierarchical ZSM-5 is valuable and interesting to be evaluated, because they are easily available and have common structural characteristics that their macromolecular structure will be largely endangered by the decomposition of quaternary ammonium groups in the long polymer chain. PCA entrapped in the zeolite partially retains its cationic charges and macromolecular structure under hydrothermal conditions and thus has a significant templating effect on the synthesis of hierarchical ZSM-5, which is benefited from the cationic centers widely separated by more than 3 carbons in PCA. However, PCS decomposes severely into small amine molecules, due to the short separation of cationic centers. Further investigation into the templating effect of PCA shows that the small-sized and negatively charged nanoblocks can easily wrap and assemble with PCA and transform into hierarchical ZSM-5 templated by PCA. However, when using large-sized zeolite seeds to synthesize ZSM-5, PCA shows a negligible templating effect because PCA with limited charge density and low accessibility of cationic charges has insufficient interactions with zeolite seeds. The catalytic activities of PCA-ZSM-5 and NCA-ZSM-5 for acetalization of cyclohexanone with methanol are inferior to that of PCS-ZSM-5 with the highest number of acid sites, but the catalytic activities for aldol condensation of benzaldehyde with n-butyl alcohol follow the order of PCA-ZSM-5 > NCA-ZSM-5 > PCS-ZSM-5, consistent with the order of mesoporosity.

Three short-chain organosilanes, i.e., 3-aminopropyltrimethoxy-silane (APTMS), [3-(2-aminoethyl)aminopropyl]trimethoxysilane (AEAPTMS) and phenylaminopropyltrimethoxysilane (PHAPTMS), were used for the synthesis of hierarchically micro-/mesoporous ZSM-5 zeolites by steam-assisted crystallization of silanized dry gels. Corresponding to the different moieties of organosilanes, the obtained hierarchically porous ZSM-5 zeolites have different degrees of mesoporosity and exhibit spherical morphology composed of small nanounits. Among the three organosilanes, PHAPTMS with a bulky cross-section is the most excellent mesopore directing agent. Tracking the structural evolution of PHAPTMS-ZSM-5 during crystallization shows that a large number of mesopores are produced in the initial steaming, but it is confirmed that it does not occur due to the presence of PHAPTMS. This initial mesoporosity is mostly preserved by the PHAPTMS molecules which inhibit the growth of the crystalline phase and suppress the high mobility of aluminosilicate species under the steam atmosphere.

A facile solvothermal route is established to generate Ni x Mg 1 − x (OH)(OCH 3 ) platelet covered by (001) facets. Thermolytic decomposition of Ni x Mg 1 − x (OH)(OCH 3 ) is topotactic and leads to the formation of Ni x Mg 1 − x O solid solution enclosed by reactive Tasker III type (111) facets. Both Mg and Ni are found to be distributed evenly in the solid solution. The reduced Ni x Mg 1 − x O platelet is a stable catalyst in CH 4 -CO 2 dry reforming for a 100 h test.

The α-Mn2O3 nanocrystals with uniform morphology prepared by calcining a self-assembly Mn3O4 precursor show higher activity toward CO oxidation. Operando Raman spectroscopy is used to probe the near-surface structure of α-Mn2O3 nanocrystals during the adsorption and oxidation of CO for the first time. A surface phase-transformation from α-Mn2O3 to MnO-like species, as evidenced by the formation of a single band at 498 cm–1, was observed only at or above 300 °C in the presence of CO. This modification is probably due to the loss of lattice oxygen at high temperatures that leads to the surface reconstruction. Very interestingly, a reversible phase-transformation was observed with decreasing the temperature to 25 °C. The shift of the symmetric stretching of Mn2O3 groups (632 → 649 cm–1) due to the adsorption of CO was observed even at room temperature. In addition, the results of the temperature-programmed desorption of O2 (TPD-O2) and temperature-programmed surface reaction (TRSR) indicate that the oxidizin...

Mesoporous silica with covalently bound salicylic acid molecules incorporated in the structure was synthesized with a one-pot, co-condensation reaction at room temperature. The as-synthesized material has a large surface area, uniform particle size, and an ordered pore structure as determined by characterization with transmission electron microscopy, thermal gravimetric analysis, and infrared spectra, etc. Using the strong fluorescence and metal coordination capability of salicylic acid, functionalized mesoporous silica (FMS) was developed to track and extract radionuclide contaminants, such as uranyl [U(VI)] ions encountered in subsurface environments. Adsorption measurements showed a strong affinity of the FMS toward U(VI) with a Kd value of 105 mL/g, which is four orders of magnitude higher than the adsorption of U(VI) onto most of the sediments in natural environments. The new materials have a potential for synergistic environmental monitoring and remediation of the radionuclide U(VI) from contaminate...

As one of the naturally abundant elements, carbon can present in different molecular structures (allotropes) and thus lead to various physical/chemical properties of carbon-based materials which have found wide applications in a variety of fields including electrochemistry, optical, adsorption and catalysis, etc. On the other hand, its different allotropes also endow carbon-based materials with various morphostructures, which have been recently explored to prepare oxides and zeolites/zeotypes with tailored structures. In this review, we mainly summarize the recent advances in using carbon materials as hard templates to synthesize structural materials. Specifically, we focus on the development in the synthetic strategies, such as endotemplating, exotemplating approaches and using carbon materials as chemical reagents for the synthesis of metal carbides or nitrides, with an emphasis laid on the control of morphostructure. Meanwhile, the applications of the obtained materials will be highlighted, especially, in the field of heterogeneous catalysis where enhanced performances have been achieved with the materials derived from carbon-templated methods.

Metastable magnesium hydroxymethoxide [Mg(OH)(OCH3)] powder with nanosheet morphology was derived from a direct bottom-up synthesis using magnesium acetate tetrahydrate as precursor under solvothermal conditions, with benzyl alcohol as structure-directing agent. The synthesis is driven by esterification of magnesium acetate to the corresponding methyl acetate, namely, ligand exchange and esterification of CH3COO– with CH3O–. A MgO powder featuring a Tasker III type (111) surface as its main exposed surface was produced after decomposition of the as-prepared Mg(OH)(OCH3) intermediate. X-ray diffraction (XRD) shows that the as-formed intermediate is Mg(OH)(OCH3), and methyl acetate is identified in the mother liquor by GC–MS measurements. XRD, SEM, and TEM images also show that the surface of the MgO nanosheets is covered by a Tasker III (111) surface. The vanadia supported on this MgO (111) nanosheet surface is more active than the conventional MgO-supported system for the oxidative dehydrogenation of ethylbenzene with carbon dioxide, which is attributed to the oxygen-rich nature and intermediate basicity of the MgO (111) surface.

A solvent evaporation route to produce hierarchically porous zeolites with an oriented MFI nanocrystalline structure has been developed, and the method is scalable and low cost. In this method, hexadecyltrimethoxysilane is added to an ethanol solution containing zeolitic precursors. A dry gel is formed during the evaporation process. Subsequent hydrothermal treatments produce the hierarchically porous zeolite. High resolution transmission electron microscopy (HRTEM) studies suggest that misoriented zeolite nuclei are produced in the early stages of the hydrothermal treatment, but further reactions lead to single crystal-like aggregates composed of intergrowth nanocrystals with a mean interparticle pore diameter of 12 nm. Almost all Al atoms exist in tetrahedral sites, as confirmed by 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). Variable temperature hyperpolarized (HP) 129Xe NMR spectroscopy suggests a fast molecular diffusion process from the interconnection between micro- and mesopores...

Silanized dry gel prepared by solvent evaporation was subjected to steam treatment to synthesize hierarchically porous zeolite Beta. With well dispersed sodium cations (Na+) in ethanol solution and dry gel, zeolite Beta with high degree of crystallinity can be obtained by the steam-assisted crystallization method. Two types of organosilanes, short-chain phenylaminopropyltrimethoxysilane (PHAPTMS) and long-chain hexadecyltrimethoxysilane (HDTMS), were applied to prepare the silanized dry gel and inhibit the crystallization of zeolite Beta. PHAPTMS does not generate appreciable mesopores, whereas HDTMS can successfully create abundant mesopores ranging from 3 to 10 nm, which indicates a greater spatial separation effect of the long-chain moiety than the short-chain counterpart.

One-dimensional V2O5 nanowires have been synthesized inside the channels of mesoporous silica SBA-15 through chemical approach, which involves aminosilylation of silanol groups on the silica surface, anchoring of isopoly acid, H6V10O28. by neutralization of basic amine groups, and thermal decomposition. The formation and physicochemical properties of the nanowires were monitored and studied by TG-DTA, variable temperature in situ XRD, TEM, N2 sorption measurements and UV-Vis DRS. The results indicate that V2O5 nanowires formed within SBA-15 channels belong to orthorhombic polycrystal domains. The oxygen-to-metal charge transfer band of V2O5 nanowires shows a blue shift in comparison with bulk V2O5, which clearly exhibits the quantum size effect of nanowires.

Metal and metal oxide nanoparticles supported on high surface area materials are widely used in industry for fuel and chemical production and for environmental pollution control, but preventing nanosized particle sintering has remained a great challenge. In this paper, we report that Ni−Cu alloy nanoparticles can be effectively stabilized in cubic mesostructured silica (SBA-16) following a conventional impregnation and thermal treatment process. The three-dimensional interconnected cage structure of the mesoporous SBA-16 allows good accessibility of reactant gas molecules to the metal nanoparticles and confines these particles within its nanosized cages. This confinement hinders metal nanoparticle migration and sintering under harsh conditions. A new class of regenerable metal-based adsorbents which can remove sulfur impurities from warm syngas stream down to less than 60 parts per billion by volume (ppbv) is described. This same confinement strategy is expected to have impact for minimizing sintering or ...

The purpose of this review is to highlight developments in self-assembled nanostructured materials (i.e., mesoporous and nanoparticle-based materials) and their catalytic applications. Since there are many available reviews of metal-based nanoparticles as catalysts, this review will mainly focus on self-assembled oxide-based catalytic materials. The content includes: (1) design and synthetic strategies for self-assembled mesoporous catalysts, (2) polyoxometalate (POM)-based nanocatalysts, (3) dendrimer-based nanocatalysts, and (4) shaped nanomaterials and catalytic applications. We show that controlled assembly of molecules, crystalline seeds, and nano building blocks into organized mesoscopic structures or controlled morphologies is an effective approach for tailoring porosities of heterogeneous catalysts and controlling their catalytic activities.

A mesoporous carbon prepared from sucrose was successfully employed as a hard template to produce hierarchical silicalite-1, thus providing a very simple and inexpensive route to desirable zeolite catalysts from widely available raw materials. The porous carbon was prepared by hydrothermal treatment of a mixture of sucrose and ammonia followed by carbonization of the mixture in N2 at high temperatures. The porous carbon produced by this method was subsequently applied as a hard template in the synthesis of mesoporous silicalite-1 and removed by combustion after synthesis. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAD), thermal gravimetry (TG), differential scanning calorimetry (DSC), N2 physisorption measurements, Hg porosimetry and CHN elemental analysis techniques were applied to investigate the porous carbon template as well as the mesoporous zeolite single-crystal material. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

MgO(111) nanosheets can be prepared via a facile wet chemical process. The MgO(111) nanosheets possessing the exposed (111) plane as a main surface have a thickness typically between 3 and 5 nm. Study of MgO(111) nanosheets by in situ diffuse reflectance Fourier transform (DRIFT) spectroscopy suggests that hydroxyl groups, oxygen vacancies, and surface oxygen anions exist on the surface and the (111) surface may be stabilized by hydroxyl groups. DRIFTS and temperature-programmed desorption (TPD) studies of CO2 adsorption reveal that there are large amounts of medium basic sites which can be attributed to the high concentration of surface O2- Lewis basic sites. DRIFTS and temperature-programmed reaction studies (TPRS) of methanol have demonstrated that, in contrast to commercial MgO, MgO(111) nanosheets are highly reactive toward the decomposition of methanol. Methanol can be decomposed and the surface C = O species formed can be oxidized readily at low temperature by the high concentration of oxygen anions on the surface of MgO(111) nanosheets, which demonstrates that these nanosheets have potential application in fuel cells and methanol-based alternative energy technologies.

Gold nano-particles confined in the walls of mesoporous silica (GMS) catalysts were successfully prepared by a novel and simple technique utilizing thioether functional groups in the walls of mesoporous silica to anchor HAuCl4. Calcination of the materials removed organic moieties and reduced thegold salt to gold nano-particles. In this procedure, the thioethergroups were introduced into the silicawall via a co-condensation of tetraethyl orthosilicate (TEOS) with 1,4-bis(triethoxysily)propane tetrasulfide. These gold containing mesoporous catalysts have unusually high surface area and porevolume. The catalysts were evaluated for the solventfree liquid phase oxidation of benzyl alcohol bymolecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 403 K, 15 atm and 5 h in an autoclave. The 1.5% GMS catalyst was also evaluated for oxidation of alcohols using toluene as solvent under flowing oxygen at atmospheric pressure at 353 K in a two-necked flask. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled three times without significant loss of activity. # 2007 Elsevier B.V. All rights reserved.

We report the synthesis and characterization of a series of new mesoporous zeolite and zeotype materials made available by combining new and improved procedures for directly introducing carbon into reaction mixtures with the fluoride route for conventional zeolite synthesis. The mesoporous materials were all prepared by hydrothermal crystallization of gels adsorbed on carbon matrices which were subsequently removed by combustion. The procedures presented here resulted in mesoporous zeolite and zeotypes materials with MFI, MEL, BEA, AFI and CHA framework structures. All samples were characterized by XRPD, SEM, TEM and N2 physisorption measurements. For the zeolite materials it was found that mesoporous MFI and MEL structured single crystals could indeed be crystallized from fluoride media using an improved carbon-templating approach. More importantly, it was found that mesoporous BEA-type single crystals could be crystallized from fluoride media by a newly developed procedure presented here. Thus, we here present the only known route to mesoporous BEA-type single crystals, since crystallization of this framework structure from basic media is known to give only nanosized crystals as opposed to mesoporous single crystals. For the zeotype materials it was found that highly crystalline mesoporous materials of AFI and CHA structure types could be synthesized using a newly developed procedure.

A route to generate hierarchically porous zeolite ZSM-11 has been paved via solvent evaporation induced self-assembly assisted by hexadecyltrimethoxysilane to produce a preformed dry gel, followed by its subsequent transformation into zeolite via steam-assisted-crystallization. The crystallization in dry gel has been found to undergo an orientated attachment growth mechanism whereby hexadecyltrimethoxysilane directs the formation of auxiliary mesopores and inhibits the fusion of primary nucleates. Measurements such as XRD, SEM, TEM, N2-physisorption, and TEM for an inverse replica of Pt derived from hierarchical ZSM-11 have been conducted to characterize the textural properties of the material. Ammonia temperature-programmed-desorption (NH3-TPD) measurements and infrared spectra using probe molecules such as pyridine (Py-IR) and 2,4,6-collidine (Coll-IR) have been collected to investigate the acidic properties as well as the accessibility of the acid sites. The hierarchical ZSM-11 possesses more acid sites on the mesopore surfaces that are accessible towards large probe molecules such as 2,4,6-collidine. This improvement together with the enhanced pore-connectivity brings about an increase in 1,3,5-triisopropylbenzene cracking activity and benzene selectivity with respect to a conventional counterpart.

MgO kristallisiert im Kochsalzgitter und hat üblicherweise die Mg(100) Ebene an der Oberfläche. Die Mg(111) Ebene besteht aus alternierenden Monoschichten von Sauerstoffanionen und Magnesiumkationen und hat große katalytische Aktivität beispielsweise bei der Claisen-Schmidt-Kondensation. Die bis jetzt bekannten Herstellungsmethoden für MgO(111) Oberflächen waren aufwendig oder uneffektiv. Bei der neuen Herstellungsmethode für (111) Nanoflächen wird eine Mischung von Wasser und Methanol zu einer Lösung von Magnesiummethylat in Methanol mit einer stoichiometrische Menge von 4-Nitro- oder 4-Methoxybenzylalkohol zugegeben und unter überkritischen Bedingungen auf 265 Grad C erhitzt. Nach Ablassen des Lösungsmitteldampfes entsteht ein weißes Pulver, das bei 500 Grad C kalziniert wird. Mehrere transmissionselektronenmikroskopische Bilder zeigen die Strukturen der MgO Nanoplättchen.

Tungsten-substituted mesoporous SBA-15 materials have been synthesized by using a direct co-condensation sol–gel method. These resultant materials have been characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), 29Si MAS NMR and UV–Visible spectroscopy. Results of these analysis indicated that these materials had high surface area, uniform hexagonal channels and thick framework walls which were similar to that of SBA-15 and the tungsten species were highly dispersed in the silica-based framework structure. The tungsten-substituted mesoporous SBA-15 materials were used as catalysts for 1-butene metathesis for the first time, and they showed excellent catalytic performance. Such outstanding catalytic performance should be attributed to the proper content of tungsten species and its high dispersion.

Imidazole type ionic liquid 1-hexadecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methylimidazolium ruthenium hexachloride were used to fabricate the well-ordered hexagonal mesoporous silica (under acidic and basic conditions), and Ru–SiO 2 , respectively. Small angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 adsorption–desorption were employed to characterize the structure. The mesoporosity of the silica matrix is preserved after calcination of organic templates. The pore diameter of silica prepared from acidic media (2.20 nm) was smaller and less ordered than that of silica from basic solution (2.74 nm). Further, the mesoporous structure of Ru–SiO 2 was found to be preserved after calcination, however, RuO 2 nanoparticles formed in the matrix of mesoporous silica upon calcination.

Thermally stable mesoporous tetragonal zirconia with high surface area (153 m2/g at 700 °C) has been prepared by using bifunctional ethylene diamine as both precipitating agent for ZrOCl2 to ZrO(OH)2 and colloidal protecting agent for the ZrO(OH)2 nanoparticles. The zirconia sample was found to possess the tetragonal crystal phase exclusively. This approach avoids traditional bases such as NH3, NaOH and expensive surfactants and copolymers, which are usually employed as templates for the synthesis of high surface area and thermally stable metal oxides. Pt nanoclusters of size ∼20–30 A have been prepared in a single step chemical reduction method in aqueous media. The Pt nanoclusters have been deposited on mesoporous (pore size ≈ 35–45 A) hydrous zirconia by adopting the ‘precursor’ route. The Pt nanoclusters have been found almost evenly dispersed in the hydrous zirconia matrix without aggregation. The ethylene diamine likely serves as a link between the support (ZrO(OH)2) and Pt nanoclusters. The Pt/ZrO2 catalyst has been found to be highly active for 1-hexene hydrogenation reactions with a turnover frequency of about 20,000 h−1. All systems have been characterized by TEM, EDX, SEM, X-ray diffraction, N2 adsorption–desorption isotherms and TGA.

Three-dimensional (3D) mesoporous tungsten oxide single crystals has been prepared by using aminosilylized 3D mesoporous SBA-15 as the template and characterized by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. The product is an array of hexagonally ordered nanorods linked by nanosized bridges to form a 3D open framework as an inverse replica of SBA-15.

A series of highly efficient hybrid gold nanoparticle/mesoporous-silica catalysts were synthesized and employed for the solvent-free aerobic oxidation of cyclohexane to cyclohexanol and cyclohexanone under moderate reaction conditions. The catalysts were characterized by XRD, N2 adsorption/desorption, TEM and ICP-AES, which shows the active species are monodispersed gold nanoparticles.

A new approach was developed to fabricate nanowires of mixed oxides MoO3-V2O5 inside the channels of mesoporous silica SBA-15. The method involves functionalization of the channel surface of SBA-15 with aminosilane groups, immobilization of Keggin-type molybdovanadophosphoric acids through an acid-base interaction, and heat treatment. The immobilization of the heteropolyacid containing mixed addenda makes the molar ratio of the loaded components controllable. The formation of the MoO3-V2O5 nanowires inside the channels was monitored by variable temperature in situ XRD. The materials obtained by heat treatment at 400 °C for 5 h were characterized by TEM, N2-sorption measurements, laser Raman spectra and UV-Vis diffuse reflectance spectra. Further heat treatment of the MoO3-V2O5 nanowires inside the SBA-15 channels at higher temperature (700 °C) destroys the framework integrity of SBA-15 by complete sublimation of MoO3 through the SBA-15 channel walls.

Bis(1,5-cyclooctadiene) nickel [Ni(COD)2] was employed as a nickel precursor to prepare nickel oxide nanoparticles upon high-surface-area mesoporous silica. Under protection of argon, Ni(COD)2 was dissolved in tetrahydrofuran (THF) to react with surface silanols of mesoporous silica SBA-15, which formed a black powder after completion of the surface reaction. Calcination of the powder produced ultrafine NiO inside the mesoporous silica matrix, which was evidenced by X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy and thermogravimetric analysis. The thermogravimetric analysis suggests that NiO formation is a result of surface nickel species calcination, whereas structural characterization clearly show that NiO nanoparticles of

A new method is developed to obtain crystalline nanowires of WO 3 using mesoporous silica SBA-15 as template. The method includes aminosilylation of the surface silanols within SBA-15 channels, anchoring of the heteropoly acid (HPA) to the grafted amine groups, thermal decomposition of the HPA, and removal of the silica framework with HF. The formation of the crystalline nanowires is monitored by the in situ XRD technique. TEM images intuitively confirm that the nanowires are uniform in diameter and HRTEM images further indicate that each nanowire belongs to single crystal although the growth orientations of these nanowires are different.

NiO nanosheet with high-energy (111) polar surface was prepared in high yield under mild conditions using nickel acetate tetrahydrate as starting material via thermal decomposition of intermediate ...

The aim of this paper was to propose a creep-fatigue life prediction model based on multiple regression analysis of the existing experimental data. Three different factors including temperature, hold time, and total strain range, were taken into consideration in this model. The prediction capacity of the present model was verified through comparison between predicted results and existing experimental data of different materials with different testing conditions. A good agreement was found between the predicted results and the experimental data.

N-o-Methylphenylferrocenesulfonamide was synthesized from the reaction of ferrocenesulfonyl chloride with o-toluidine. The structure was determined by single-crystal diffraction. Crystal data: monoclinic, P21/c, with unit cell dimensions of a=10.436(2), b=12.377(3), c=12.6431(3) A, and β=107.42(1)°, V=1558.1(6) A3, Z=4. The most stable structure of the complex in theory was obtained by the Hartree–Fock SCF of gaussian 98W, and the two results have been compared.

The tetrairon(III)-substituted polytungstates [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV)) were immobilized on (3-aminopropyl)triethoxysilane-modified SBA-15 and showed an excellent catalytic performance for solvent-free aerobic oxidation of long-chain n-alkanes using air as the oxidant under ambient conditions through a classical free-radical chain autoxidation mechanism.

A simple procedure applying crystallization of zeolites around a combustible carbon matrix generated in situ from sugar deposited onto mesoporous silica gel offers good perspectives for the large-scale preparation of mesoporous zeolites.

Platelet-like CeO2 mesocrystals, constituted of 4–5 nm fused nanoparticles with interparticular voids along a common [002] axis, have successfully been synthesized through a benzyl alcohol-assisted solvothermal synthesis, followed by a topotactical transformation at 400 °C. The resulting CeO2 mesocrystal superstructure is enclosed by Tasker III type {100} facets. H2-TPR suggested that the as-made CeO2 mesocrystal surfaces are covered by reactive oxygen vacancies. Such oxygen vacancies can activate oxygen at low temperatures (

As one of the naturally abundant elements, carbon can present in different molecular structures (allotropes) and thus lead to various physical/chemical properties of carbon-based materials which have found wide applications in a variety of fields including electrochemistry, optical, adsorption and catalysis, etc. On the other hand, its different allotropes also endow carbon-based materials with various morphostructures, which have been recently explored to prepare oxides and zeolites/zeotypes with tailored structures. In this review, we mainly summarize the recent advances in using carbon materials as hard templates to synthesize structural materials. Specifically, we focus on the development in the synthetic strategies, such as endotemplating, exotemplating approaches and using carbon materials as chemical reagents for the synthesis of metal carbides or nitrides, with an emphasis laid on the control of morphostructure. Meanwhile, the applications of the obtained materials will be highlighted, especially, in the field of heterogeneous catalysis where enhanced performances have been achieved with the materials derived from carbon-templated methods.

A large-sample-volume constant-flow magic angle sample spinning (CF-MAS) NMR probe is reported for in situ studies of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. In our approach, the reactants are introduced into the catalyst bed using a fixed tube at one end of the MAS rotor while a second fixed tube, linked to a vacuum pump, is attached at the other end of the rotor. The pressure difference between both ends of the catalyst bed inside the sample cell space forces the reactants flowing through the catalyst bed, which improves the diffusion of the reactants and products. This design allows the use of a large sample volume for enhanced sensitivity and thus permitting in situ(13)C CF-MAS studies at natural abundance. As an example of application, we show that reactants, products and reaction transition states associated with the 2-butanol dehydration reaction over a mesoporous silicalite supported heteropoly acid catalyst (HPA/meso-silicalite-1) can all be detected in a single (13)C CF-MAS NMR spectrum at natural abundance. Coke products can also be detected at natural (13)C abundance and under the stopped flow condition. Furthermore, (1)H CF-MAS NMR is used to identify the surface functional groups of HPA/meso-silicalite-1 under the condition of in situ drying. We also show that the reaction dynamics of 2-butanol dehydration using HPA/meso-silicalite-1 as a catalyst can be explored using (1)H CF-MAS NMR.

We report the design and synthesis of nanosized Zn(x)Zr(y)O(z) mixed oxides for direct and high-yield conversion of bio-ethanol to isobutene (~83%). ZnO is addded to ZrO(2) to selectively passivate zirconia's strong Lewis acidic sites and weaken Brönsted acidic sites, while simultaneously introducing basicity. As a result, the undesired reactions of bio-ethanol dehydration and acetone polymerization/coking are suppressed. Instead, a surface basic site-catalyzed ethanol dehydrogenation to acetaldehyde, acetaldehyde to acetone conversion via a complex pathway including aldol-condensation/dehydrogenation, and a Brönsted acidic site-catalyzed acetone-to-isobutene reaction pathway dominates on the nanosized Zn(x)Zr(y)O(z) mixed oxide catalyst, leading to a highly selective process for direct conversion of bio-ethanol to isobutene.

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H3PW12O40 (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and thus provide good model systems to investigate the structure dependence of the catalytic properties. The HPA on mesoporous silicalite-1 shows enhanced catalytic activity for 1-butene isomerization, while HPA on conventional silicalite-1 exhibits low activity. To elucidate the structural difference, supported HPA catalysts are characterized using a variety of techniques, including 31P magic angle spinning nuclear magnetic resonance, and are shown to contain a range of species on both mesoporous and conventional zeolites. However, contrary to studies reported in the literature, conventional NMR techniques and chemical shifts alone do not provide sufficient information to distinguish the dispersed and aggregated surface species. The dispersed phase and the nondispersed phase can only be unambiguously and quantitatively characterized using spin-lattice relaxation NMR techniques. The HPA supported on mesoporous zeolite contains a fast relaxation component related to the dispersed catalyst, giving a much higher activity,more » while the HPA supported on conventional zeolite has essentially only the slow relaxation component with very low activity. The results obtained from this work demonstrate that the combination of spinning sideband fitting and spin-lattice relaxation techniques can provide detailed structural information on not only the Keggin structure for HPA but also the degree of dispersion on the support.« less

Mesoporous silica SBA-15 has been used to synthesize its negative replicas of crystalline transition metal oxides, Cr 2 O 3 , WO 3 , V 2 O 5 , MnO 2 and CuO. After removing the silica templates, the detailed structures of the produced nanoparticles, nanorods and 3D porous single crystals were investigated by using high resolution transmission electron microscopy (HRTEM). Formation mechanisms of these replicas were studied based on the HRTEM observations of the series specimens with different experimental conditions. Surface structures of the nanorods were revealed by HRTEM surface profile imaging so that the morphologies of the nanorods in these materials could be investigated in order to reveal the sizes and shapes of mesopores in the silica templates. When the whole inner space in SBA-15 is filled by metal oxides, the products become 3D porous single crystals, which is a new class of self-supported nanoparticle catalysts.

Three-dimensional porous chromium oxide single crystals have been prepared by aminosilylation of the surface silanols of the template, SBA-15, anchoring of dichromic acid to the grafted amine groups, thermal decomposition of inorganic and organic compounds, and removal of the silica framework with HF.

A hierarchical ZSM-5 zeolite with uniform mesopores has been synthesized by self-assembly of zeolite seeds capped with carboxyl-ended organosilane. The carboxylate anion enhances the inorganic–surfactant interaction and enables the formation of mesopores.

α-Fe2O3 nanowires were prepared using mesoporous silica SBA-15 as a template and showed a remarkable catalytic activity for the hydroxylation of phenol with 30% H2O2 in aqueous solution at 343 K.

Bi-metallic VOx–SbOx/SBA-15, which may be used as a site-isolated model catalyst, is successfully prepared by a two-stage grafting method using a vanadium matallocene and SbCl5 as precursors.