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Sustainable plant-derived N-oleyl-1,3-diaminopropane surfactant micelles cross-linked by divinylbenzene (DVB) have been intercalated in the pores of mesostructured silica and the resulting functionalized mesophases were used to immobilize heavy metal ions through complexation by the diamine head groups. Two methods were used to form the composite surfactant–silica compositions. In the “pre-assembly” approach, the unsaturated amine micelles were first cross-linked in aqueous solution and subsequently used as a structure-directing agent to form the composite silica–polymeric amine mesophase. In the second “post-assembly” approach, the unsaturated amine micelles were used to template the silica mesophase and then cross-linked in situ with DVB within the pores of the composite mesophase. The accessibility of the amine functional groups in the mesophases prepared by both assembly methods was demonstrated through the uptake of Cu(ii) and Pb(ii) ions from aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: The low-temperature synthesis (90°C) of nanoparticle forms of a pure phase smectic clay (saponite) and zeolite (cancrinite) is reported, along with phase mixtures thereof. A synthesis gel corresponding to the Si:Al:Mg unit cell composition of saponite (3.6:0.40:3.0) and a NaOH/Si ratio of 1.39 affords the pure phase clay with disordered nanolayer stacking. Progressive increases in the NaOH/Si ratio up to a value of 8.33 results in the co-crystallization of first garronite and then cancrinite zeolites with nanolath morphology. The resulting phase mixtures exhibit a compound particulate structure of intertwined saponite nanolayers and cancrinite nanolaths that cannot be formed through physical mixing of the pure phase end members. Under magnesium-free conditions, pure-phase cancrinite nanocrystals are formed. The Si/Al ratio of the reaction mixture affects the particle morphology as well as the chemical composition of the cancrinite zeolite. Ordinarily, cancrinite crystallizes with a Si/Al ratio of 1.0, but a silicon-rich form of the zeolite (Si/Al=1.25) is crystallized at low temperature from a silica-rich synthesis gel, as evidenced by 29Si NMR spectroscopy and XEDS-TEM. Owing to the exceptionally high external surface areas of the pure phase clay (875m2/g) and zeolite end members (8.9–40m2/g), as well as their unique mixed phase composites (124–329m2/g), these synthetic derivatives are promising model nanoparticles for studies of the bioavailability of poly-aromatic hydrocarbons immobilized in silicate bearing sediments and soils. [Copyright &y& Elsevier]

Abstract: The synthesis of saponite in the presence of bis(triethoxysilyl)methane (BTESM) as an organosilicon reagent results in the replacement of up to 33.3% of the oxygen atoms in the tetrahedral sheet by bridging methylene groups. The methylene-functionalized saponites represent a new form of covalently bonded organoclay that truly is isomorphic with purely inorganic saponite made under equivalent reaction conditions from sodium silicate as the silicon source. The isoelectronic and isolobal relationship between methylene and bridging oxygen centers is essential for methylene saponite formation. Bridging ethylene groups are not incorporated into the Kagome net of the basal surfaces due to a mismatch in bridging group size. The textural properties of the methylene saponites are similar to those for purely inorganic magnesium saponite made under equivalent synthetic conditions in the absence of BTESM. Layer stacking disorders afford large surface areas (∼550 to 650m2/g), making the methylene saponites attractive candidates for use as adsorbents and functional fillers for polymer composites. [Copyright &y& Elsevier]

Abstract: Large-pore mesoporous silica with 3D wormhole framework structures (denoted MSU-J) are prepared through a supramolecular hydrogen-bonding assembly pathway from low-cost sodium silicate as the silica source and commercially available mono- and tri-amine Jeffamine and Surfonamine surfactants as structure-directing porogens. The calcined mesostructures exhibit large pore sizes (up to 8.2nm), surface areas (632–1030m2/g) and pore volumes (0.5–2.0cm3/g), depending on the surfactant chain length and synthesis temperature (25–65°C). The textural properties of these new wormhole mesostructures are comparable to those of hexagonal SBA-15 derivatives and large pore MCM-48. However, unlike the SBA-15 structure type, wherein the 3D pore network is formed by connecting 1D cylindrical mesopores through micropores, MSU-J mesophases have wormhole framework structures containing fully interconnected 3D mesopores that can minimize the diffusion limitations often encountered in adsorption and chemical catalysis. Also, unlike large pore MCM-48, which requires cost-intensive tetraethylorthosilicate as a silica source and the use of a co-surfactant as a pore expander under strong acid conditions, MSU-J mesostructures are assembled from low-cost sodium silicate in the presence of a single Jeffamine or Surfonamine porogen at near-neutral pH. [Copyright &y& Elsevier]

Abstract: We show for the first time that the NH+ 4 exchanged form of ZSM-5 zeolite is as effective as the H+ form of the catalyst for the regioselective conversion of toluene to mononitrotoluene (MNT) using 90% nitric acid as the sole nitrating agent. The auto-ionization of the acid in the absence of protons on the zeolite surface is sufficient for the formation of reactive nitronium ions. We also find that the regioselectivity for the formation of p-MNT is substantially increased over both forms of the zeolite catalyst by first intercalating the acid in the zeolite micropores prior to the introduction of toluene. For instance, the isomer ratio is increased from values in the range 1.3–2.3 under conventional batch reaction conditions to values of 1.8–8.9 when the acid is sequestered in the zeolite. The sequestration of nitric acid in both ion exchanged forms of the zeolite confines more of the nitration reaction to the regioselective environment of the micropores and reduces the extent of reaction in homogeneous toluene solution. However, the ammonium form of the zeolite is preferred over the protonated form when the Si/Al ratio of the zeolite allows for the presence of at least one ammonium ion per unit cell (Si/Al ⩽ 40), because under these conditions far less benzaldehyde and other undesired reaction products are formed in comparison to the protonated form of the zeolite at the same Si/Al ratios. The ability of NH+ 4-ZSM-5 derivatives to limit the formation of unwanted toluene oxidation products is not well understood, but the observed selectivity may be related to the replacement of ammonium ions by protons, the formation of ammonium nitrate, and the buffering of nitric acid within the micropores of the zeolite. [Copyright &y& Elsevier]

Abstract: We report the properties of a porous synthetic clay (saponite, denoted SAP) for the reinforcement of rubbery and glassy epoxy polymers. Remarkably, reinforcement properties superior to those of organo-montmorillonite can be achieved without the need for a surface organic modifier, as evidenced by the improvements in tensile strength, modulus and toughness at temperature above and below the glass transition temperature of the polymer. The disordered stacking of clay platelets ∼50nm in lateral dimension gives rise to aggregated tactoids with a BET surface area of 920m2/g, an average BJH pore size of 5.0nm, and a pore volume of 1.98cm3/g. These unique textural properties facilitate the dispersion of the tactoids into the polymer matrix and allow reinforcement of the polymer matrix in the absence of an organic modifier. [Copyright &y& Elsevier]

A novel three-step assembly pathway is reported for the formation of a mesostructured alumina with framework pore walls made of crystalline, lathlike γ-Al[sub 2]O[sub 3] nanoparticles, in the initial supramolecular assembly step of the pathway a mesostructured alumina with a wormhole framework morphology and amorphous pore walls is assembled through the hydrolysis of Al[sub 13] oligocations and hydrated aluminum cations in the presence of a nonionic diblock or triblock poly(ethylene oxide) surfactant as the structuredirecting porogen. The walls of the initial mesostructure are then transformed in a second hydrolysis step at a higher temperature to a surfactant-boehmite mesophase, denoted MSU-S/B, with a lathlike framework made of boehmite nanoparticles. A final thermal reaction step topochemically converts the intermediate boehmitic mesophase to a mesostructure with crystalline γ-Al[sub 2]O[sub 3] pore walls, denoted MSU-γ, with retention of the lathlike framework morphology. The boehmitic MSU-S/B intermediates formed from the chloride salts of aluminum incorporate chloride anions into the mesostructure. Chloride ion incorporation tends to disorder the nanoparticle assembly process, leading to a broadening of the slit-shaped framework pores in the final MSU-γ phases and to the introduction of intra- and inter-particle textural mesopores. However, the well-ordered MSU-γ phases made from aluminum nitrate as the preferred aluminum reagent exhibit narrow framework pore size distributions and average pore sizes that are independent of the surfactant size and packing parameter, in accord with a lathlike framework assembled from nanoparticles of regular size and connectivity. The high surface areas (∼300-350 m²/g) and pore volumes (∼0.45-0.75 cm³/g) provided by these mesostructured forms of γ-Al[sub 2]O[sub 3] should be useful in materials and catalytic applications where the availability of surface Lewis acid... [ABSTRACT FROM AUTHOR]

A novel three-step assembly pathway is reported for the formation of a mesostructured alumina with framework pore walls made of crystalline, lathlike γ-Al[sub 2]O[sub 3] nanoparticles. In the initial supramolecular assembly step of the pathway a mesostructured alumina with a wormhole framework morphology and amorphous pore walls is assembled through the hydrolysis of Al[sub 13] oligocations and hydrated aluminum cations in the presence of a nonionic diblock or triblock poly(ethylene oxide) surfactant as the structure-directing porogen. The walls of the initial mesostructure are then transformed in a second hydrolysis step at a higher temperature to a surfactant-boehmite mesophase, denoted MSU-S/B, with a lathlike framework made of boehmite nanoparticles. A final thermal reaction step topochemically converts the intermediate boehmitic mesophase to a mesostructure with crystalline γ-Al[sub 2]O[sub 3] pore walls, denoted MSU-γ, with retention of the lathlike framework morphology. The boehmitic MSU-S/B intermediates formed from the chloride salts of aluminum incorporate chloride anions into the mesostructure. Chloride ion incorporation tends to disorder the nanoparticle assembly process, leading to a broadening of the slit-shaped framework pores in the final MSU-γ phases and to the introduction of intra- and interparticle textural mesopores. However, the well-ordered MSU-γ phases made from aluminum nitrate as the preferred aluminum reagent exhibit narrow framework pore size distributions and average pore sizes that are independent of the surfactant size and packing parameter, in accord with a lathlike framework assembled from nanoparticles of regular size and connectivity. The high surface areas (∼300-350 m²/g) and pore volumes (∼0.45-0.75 cm[sup 3]/g) provided by these mesostructured forms of γ-Al[sub 2]O[sub 3] should be useful in materials and catalytic applications where the availability of surface Lewis acid... [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the mercury binding properties of thiol functionalized mesoporous hydroxyl molecular sieves (HMS). Mesostructure syntheses of the HMS silicia molecular sieves; Details on the adsorbent characterization of the sieves; Results of the study.

Studies the pillaring of Mg3Al layered double hydroxides (LDHs) by the title polyoxometalates (POMs) through the use of ion exchange reaction of LDH-hydroxide and -adipate precursors with the POM anion at ambient or refluxing temperatures. Pillaring reaction, formation of a poorly ordered impurity phase.

Examines the properties of and composition of a series of Mg2+1-xAl3+x layered double hydroxide (LDH) intercalated by carbonate, hydroxide, chloride, and sulfate anions. Thermal properties; Structural properties; Basic properties.

Demonstrates a biomimetic templating approach to the synthesis of lamellar silicas. Basis of the procedure; Production of porous lamellar silicas with vesicular particle morphology.

Demonstrates a neutral templating route for preparing molecular sieves based on hydrogen-bonding interactions and self-assembly between neutral primary amine micelles and neutral inorganic precursors. Production of ordered mesoporous materials with thicker framework walls, smaller x-ray scattering domains and improved textural mesoporosities; Recovery of the cost-intensive template.

Reports on an example of nanosized mesoporous aluminosilicate with the hydrothermal stability and acidity needed for the cracking of high molecular weight hydrocarbons. Use of protozeolitic aluminosilicate nanoclusters in the construction of acidic pore walls and starch as a porogen.

2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially. Environ. Toxicol. Chem. 2011;30:2748-2755. © 2011 SETAC [ABSTRACT FROM AUTHOR]

Abstract: PMMA–mesoporous silica nanocomposites were prepared for the first time through in situ batch emulsion polymerization of methyl methacrylate in the presence of large pore MSU-F silica with a mesocellular foam structure (24.8nm average cavity size) and subsequent compression molding of the polymer–silica nanoparticle mixtures. For composites containing 5.0wt % silica, the onset decomposition temperature and the temperature at 10% weight loss for the nanocomposite increased 41°C and 50°C, respectively, in comparison to pure PMMA. The glass transition temperature of the nanocomposite increased 9.3°C, as determined by differential scanning calorimetry. In addition, the storage modulus determined by dynamic mechanical analysis increased 17% and 80% at 50°C and 100°C, respectively. Substantial improvements in tensile strength (+50%) and modulus (+72%), were achieve at 10wt % nanoparticle loading. Composites made by compression molding of physical mixtures of PMMA and MSU-F silica powders provide less improvement in thermal stability, glass transition temperature and mechanical properties in comparison to the composites made through in situ batch emulsion polymerization. Unlike previously reported composites made from nanoclays, the silica composites reported here show improvements in both thermal stability and mechanical reinforcement. [Copyright &y& Elsevier]

Abstract: Mesoporous forms of silica with wormhole framework structures prepared from tetraethylorthosilicate (denoted MSU-J-TEOS) or from sodium silicate (denoted MSU-J-SS) and an amine surfactant as the structure-directing porogen are highly effective reinforcing and toughening agents for rubbery and glassy epoxy polymers. The improvements in tensile strength and modulus provided by MSU-J silicas with a large average framework pore size (e.g., 5.9 and 21.3nm) are superior to those provided by the corresponding silicas made from the same TEOS or SS precursors but with smaller framework pore sizes (e.g., 4.2 and 5.2nm). The improved performance of the larger pore structures is realized even though the surface areas (∼670m2/g) are substantially lower than the surface areas of the smaller pore analogs (812–1025m2/g), most likely, because of more efficient polymer impregnation of the particle mesopores. In comparison to the MSU-J-TEOS silica assembled from TEOS, MSU-J-SS silica made from SS exhibits a more uniform pore distribution and smaller particles. These latter textural features lead to improved tensile strength and modulus without compromising the strain-at-break for both rubbery and glassy epoxy polymers. The exceptional strength and toughness provided by MSU-J-SS silica in comparison to MSU-J-TEOS silica are correlated with the high degree of dispersion of the mesophase particles in the epoxy matrix for the more effective distribution of stress and the deflection of microcracks. [Copyright &y& Elsevier]

Abstract: Palygorskite, a silicate clay with a pleated 2:1 layered structure, has a lath-like particle morphology that makes it an attractive candidate for the formation of polymer nanocomposites. Here, we report the properties of palygorskite in pristine and silylated forms for the reinforcement of rubbery and glassy epoxy matrices. Three silylation reagents were used for surface modification of the mineral, namely, γ-aminopropyltrimethoxysilane (APTMS), N-dodecyltriethoxysilane (DTES), and 1,1,1,3,3,3-hexamethyldisilazane (HMSZ). The silylated palygorskite derivatives provided better dispersions in rubbery epoxy matrices than the pristine mineral, affording improvements in mechanical properties at low loadings levels of 2 and 5% (w/w). But at higher loadings where increases in the viscosity of the pre-polymer helps to stabilizes the mineral dispersion, little or no differences were observed for the reinforcement benefits provided by the pristine and silylated forms of palygorskite. Glassy epoxy nanocomposites formed from both pristine and silylated palygorskite exhibited marginal improvements in tensile properties regardless of the mineral loading level, suggesting that the tensile strength of the pleated sheet silicate may be approaching that of the polymer matrix. [Copyright &y& Elsevier]

Abstract: The stereoselective hydrogenation of phenyl acetylene and 1-phenyl-1-hexyne at 298K and atmospheric pressure of H2 over Pd catalysts supported on mesostructured silica was studied. The catalysts were prepared by the impregnation of HMS and MSU-X silicas with 3-D wormhole framework structures and MCM-41 silica with a 1-D hexagonal framework using a toluene solution of Pd(acac)2 to obtain a metal content close to 1wt.%. All the supports were characterised by nitrogen adsorption–desorption isotherms at 77K and XRD. The catalysts were characterized by H2 chemisorption and TEM measurements. The reactions were found to be zero order with respect to the phenyl acetylene and 1-phenyl-1-hexyne concentration. Each catalyst presented a different catalytic performance. The 1%Pd/HMS catalyst was the most active in comparison with the 1%Pd/MSU-X and 1%Pd/MCM-41 catalysts. This superior performance in the case of the HMS support was attributed to the presence of interconnected framework channels and textural mesoporosity that can increase the accessibility of the Pd centers to a greater extent than the more monolithic MSU-X and MCM-41 supports. All catalysts displayed high selectivity to styrene and cis-1-phenyl-1-hexene compounds. [Copyright &y& Elsevier]

Directly assembled wormhole mesostructures with high level functionalized mercaptan (MP-HMS) have been shown to be effective mercury(ll) (Hg2+ trapping agents. Sorption of Hg2+ onto MP-HMS was investigated using X-ray absorption spectroscopy (XAS) to identify the structural coordination of the adsorbed Hg. Samples with different fractions of mercaptan functionalized groups (i.e., x = 0.1 and 0.5) with various Hg/S molar ratios ranging from 0.05 to 1.4 were investigated. XAS analysis indicates that adsorbed Hg first coordination shell is best fitted with an Hg-O path and an Hg-S path. The Hg-S atomic distance (RHg-s) remained relatively constant while the Hg-S coordination numbers (CN) decreased as Hg/S loading increased. For the Hg-O path, both the CN and the RHg-o increased with increasing Hg loading. XAS results suggest that at low Hg loadings, adsorbed Hg2+ forms mostly monodentate sulfur complexes (-S-Hg-OH) with the sulfur functional groups on the MR-H MS surfaces. At high Hg loadings, the Hg coordination environment is consistent with the formation of a double-layer structure of Hg attached to sulfur binding sites (-S-Hg-O-Hg-OH). [ABSTRACT FROM AUTHOR]

The conversion of diphenylamine (DPA) and α-methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20 (∼57%)<2% Al-MCM-41 (∼85%)<2% Al-HMS, 2% Al-MSU-G (∼90%) when the reaction was carried out under stoichiometric reaction conditions at 90 °C. The DCDPA yields obtained with the mesostructured catalysts are the highest reported to date for this technologically important antioxidant. A heteropolyacid catalyst, H3PW12O40·xH2O (PW12) supported on mesostructured wormhole HMS and lamellar/vesicular MSU-G silica, also was examined as a catalyst for DCDPA production. The supported catalyst systems, however, afforded lower maximum yields of DCDPA (∼73–80%) in comparison to the mesostructured aluminosilicate catalysts. The exceptionally high yields of alkylated products obtained with the mesoporous aluminosilicate catalysts in comparison to the F-20 clay and the supported PW12 catalysts are attributable in part to intermediate acid strengths that minimize completing dimerization reactions of the AMS alkylating agent. Also, the pore structures of the mesostructured catalysts facilitate access to active sites on the framework walls and provide more efficient transport of reagents to framework reaction centers. Also, the regular mesoporosity of the aluminosilicate catalysts makes these structures less prone to pore plugging and to the masking of acidity through the adsorption of the high molecular weight reaction products. [Copyright &y& Elsevier]

Diprotonated forms of polyoxypropylene diamines of the type α,ω-[NH3CHCH3CH2(OCH2CHCH3)xNH32+ with x=2.6, 5.6, and 33.1, have been intercalated into montmorillonite and fluorohectorite clays and subsequently evaluated for the formation of glassy epoxy–clay nanocomposites. The intercalated onium ions functioned concomitantly as a clay surface modifier, intragallery polymerization catalyst, and curing agent. Depending on the chain length of the diamine, different orientations of the propylene oxide chains were adopted in the clay galleries, resulting in basal spacings from ∼14 A˚ (lateral monolayer, x=2.6) to ∼45 A˚ (folded structure, x=33.1). The initial clay basal spacings were correlated with the formation of intercalated and exfoliated clay–epoxy nanocomposites with improved mechanical properties and high thermal stabilities. In comparison to clay–monoamine intercalates, the use of diamine intercalates greatly reduced the plasticizing effect of the alkyl chains on the polymer matrix, resulting in improved mechanical properties while at the same time reducing the cost and time needed for nanocomposite fabrication. [Copyright &y& Elsevier]

Presents research which prepared a family of mesoporous molecular sieves. Structure and thermal and hydrothermal stabilities of the sieves; Construction of the vesicle shells; Traits of the framework structure; Incorporation of catalytic metal ion centers.

A comparative evaluation of ten catalysts for biomass pyrolysis was performed using poplar (DN-34) as the feedstock. Five of the catalysts consisted of HZSM-5 with different silica:alumina ratios (SAR, 23, 30, 55, 80 and 280). The other five catalysts were sulfated zirconia (SO4 2− ZrO 2 ), 20% SO4 2− ZrO 2 dispersed on a mesoporous MCM-41 silica support, Al–MSU–S alumnosilicate exhibiting a foam-like mesopore structure, Al–MSU–S aluminosilicate exhibiting wormhole mesopores, and a bauxite waste product known as red mud. Analytical pyrolysis in tandem with GC/MS showed that all of the catalysts except for HZSM-5 resulted in low aromatic chemical production. Highly acidic sulfated zirconia catalysts were not selective to aromatics and produced significant coke and non-condensable gases. Mesoporous MSU–S catalysts exhibiting high pore volume and acidity also gave high gas and coke yields. Among the HZSM-5 catalysts evaluated, those with the lowest SAR provided the highest yields of total aromatics and the lowest levels of undesired coke. [ABSTRACT FROM AUTHOR]

Abstract: Polymeric mesocomposite membranes were prepared via wet phase inversion processes by incorporating surfactant-templated mesoporous silica particles, denoted MSP-1, into polysulfone matrices formed with and without PEG as a molecular porogen. Transmission electron microscopy and N2 adsorption–desorption measurements showed higher surface area (354m2/g), smaller average pore size (53nm), and larger pore volume (2.92cm3/g) with a narrower pore size distribution (26nm width at half-maximum) for surfactant-templated mesoporous silica particles compared to those of precipitated commercially available mesoporous silica, HiSil. The distinct morphological changes induced by PEG and by MSP-1 were redundant from the membrane performance point of view as they translated into similar performance gains that were not additive, pointing to the potential use of mesoporous additive as an alternative porogen. The higher hydrophilicity and unique structural features of MSP-1 resulted in enhanced performance of the prepared membranes compared to MSP-free controls and HiSil-based mesocomposites. Mechanical properties of mesocomposites and neat polysulfone membranes were comparable. Electron microscopy coupled with flux and rejection measurements were used to investigate the influence of polymer content, MSP loading, and the presence of porogen on the structure and separation properties of mesocomposite membranes. Mesocomposite membranes showed increased water flux and dextran rejection. For ultrafiltration membranes the figure of merit, operationally-defined as the product of water flux and rejection of 12kDa dextran, increased by the factor of 2.8 (for membranes cast with a porogen) and 6.3 (in the absence of porogen) upon incorporation of the mesoporous additive at the loading of 10wt%. Enhancement factors were 3.7 and 11.2 for less permeable membranes cast from mixtures with higher (20wt%) polymer content. Fouling tests with humic acid solutions demonstrated that mesocomposite membranes experienced lower flux decline and showed higher rejections. [Copyright &y& Elsevier]

Zeolites with uniform intracrystal mesopores, designated MSU-MFI, were prepared using silane-modified polymers as mesopore-generating agents. X-ray diffraction analysis of this catalyst showed Braggs peaks representative of MFI structure. Catalyst characterization by nitrogen physisorption revealed a mesoporous structure with high surface area, pore size and volume. The MSU-MFI catalysts developed in this study were selective toward aromatic chemical production from poplar pyrolysis vapour. Yields of generalized products and aromatics were comparable to those obtained from conventional microporous ZSM-5 analogs as demonstrated by pyroprobe-gas chromatography/mass spectrometry and thermogravimetric analysis. While ZSM-5 was more selective to smaller C6 aromatics and naphthalenes, MSU-MFI catalysts were more selective to C8 and C9 monoaromatics. The incorporation of gallium(III) ions in MSU-MFI using the incipient wetness method increased aromatic yields by up to 15% over Ga-free catalysts and decreased the coke production by up to 6% (p < 0.05). Due to high yields and low coke formation, Ga-MSU-MFI offers an improved option for making non-oxygenated aromatic chemicals from photosynthetic biomass. [ABSTRACT FROM AUTHOR]

Abstract: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), the prototypical aryl hydrocarbon receptor (AhR) ligand, exhibits immune suppression in vivo and in vitro. Suppression of primary humoral immune responses in particular has been well characterized as one of the most sensitive functional immune endpoints in animals treated with TCDD. Previous studies have used purified TCDD to elucidate the mechanisms by which TCDD and dioxin-like compounds (DLC) impair IgM production by B cells, but did not represent the route by which animals and humans are likely to be exposed environmentally. In the studies reported here, mice were treated with TCDD adsorbed onto a well-defined synthetic silica phase of known purity and physical properties, followed by sensitization with sheep erythrocytes to initiate a humoral immune response. We found that surfactant-templated mesoporous forms of amorphous silica provided an ideal combination of purity, dispersibility and textural properties for immobilizing TCDD. TCDD-adsorbed silica distributed to the spleen and liver after oral administration as assessed by induction of cyp1a1 gene expression. Most notably, TCDD delivered in the adsorbed state on amorphous silica and as a solute in corn oil (CO) produced similar suppression of the anti-sheep red blood cell immunoglobulin M antibody forming cell (sRBC IgM AFC) response at equivalent doses of TCDD. These results suggest that TCDD immobilized on silicate particles found in soils distributes to the spleen and suppresses humoral immunity. [Copyright &y& Elsevier]

Abstract: The complete understanding of the properties of a material goes in close relationship with a correct description of their structure. This is particularly true for mesoporous silica that exhibits different shapes and sizes of the porous framework as well as different degrees of crosslinking of the silica network itself. These variations can affect drastically the specific properties of these materials as well as their hydrothermal resistance. Hydrothermal resistance and adsorption properties are governed by the surface structure, but the later parameter is not frequently studied because it can be difficult to characterize. Therefore a simple parameter such as surface roughness could be helpful in relating the properties of materials with their surface structure. The direct determination of surface roughness is impossible, but it has been demonstrated that a single mathematical parameter, the surface fractal dimension Ds, can be related within a certain limit with surface roughness. Here we demonstrate using nitrogen adsorption data that a correlation can be drawn between the values of the surface fractal dimension Ds used as a gauge of the surface roughness and the structural evolution of a series of mesoporous silicas. Among the different adsorption models for obtaining Ds that are available nowadays, we selected the one proposed by Avnir and Jaroniec. We demonstrate in this report that there exists a real correlation between the evolution of Ds, when applied to a series of samples prepared under different synthesis conditions, with the evolution of their structure and properties. By example, this study allowed us to link the range of hydrothermal resistance of different mesoporous silicas (e.g. the HMS, MSU, MCM, SBA families of silicas) with their surface roughness. Moreover, we found that HMS silica, a very resistant material toward hydrothermal treatment, exhibits actually the lowest surface roughness. We could demonstrate too how different synthesis parameters such as temperature, can modify this surface roughness, hence the final properties of the mesoporous silica. Finally, we show that this method can even be applied to water ellipsoporometry and help to follow the crystallization of thin layers of metal oxide. Bearing in mind that Ds is a parameter that can readily be determined using the existing software – based on different models – associated with most commercial adsorption equipment, we urge the broader use of the Ds parameter for the structural characterization of surface roughness in mesoporous materials and metal oxide thin layers. [Copyright &y& Elsevier]

Abstract: In the present study two synthetic mesoporous carbons, a highly ordered CMK-3 sample with hexagonal structure and a disordered mesoporous carbon (denoted DMC) were investigated for the sorption of Remazol Red 3BS (C.I. 239) dye in comparison to three commercial activated carbons and a HMS mesoporous silica with a wormhole pore structure. The structural, porosity and surface characteristics of the materials were evaluated using XRD, TEM, N2 porosimetry, FT-IR spectroscopy and zeta-potential measurements. Optimal dye sorption occurred at pH ∼2. Equilibrium sorption data followed the Langmuir model and showed that the two synthetic mesoporous carbons exhibit higher sorption capacities (q max ∼500–580mg/g at 25°C) in comparison to the commercial activated carbons which possessed either microporous (Takeda 5A and Calgon carbon) or combined micro-/mesoporous (Norit SAE-2) structures and to the HMS mesoporous silica. Thermodynamic parameters as the change in free energy, enthalpy, and entropy of sorption were also estimated. Kinetic studies were carried out and showed a rapid sorption of dye in the first ca. 30min while equilibrium was reached after ca. 3h. The sorption kinetics of dye was best described by a second-order kinetic model. A surfactant enhanced carbon regeneration (SECR) technique was used to regenerate the dye-loaded carbon sorbents. [Copyright &y& Elsevier]

Abstract: Ti(IV)-functionalized derivatives of mesostructured HMS and MCM-41 silica with 3D wormhole and 1D hexagonal framework structures, respectively, were examined as catalysts for the oxidation of 4-tert-butyltoluene to 4-tert-butylbenzaldehyde using tert-butylhydroperoxide (TBHP) and aqueous hydrogen peroxide as oxidizing agents in acetonitrile solution. In an effort to achieve optimal site-isolation of reactive Ti(IV) centers, functionalization was carried out through the grafting of titanocene dichloride to the framework walls of the pre-assembled mesostructures, followed by calcination. Clear evidence for the undesirable clustering of Ti(IV) centers with increasing Ti(IV) loading was obtained by UV–Vis spectroscopy. Thus, the Ti(IV)-loading in the silica framework was limited to values below 8mol%. Maximal 23.6% and 21.8% conversions of 4-tert-butyltoluene to 4-tert-butylbenzaldehyde with >99% selectivity were observed for 4.8% Ti-HMS and 4.8% Ti-MCM-41 catalysts using TBHP as the oxidant. Substantially lower conversions were obtained with H2O2 as the oxidant due to clustering of Ti(IV) centers under reaction conditions and the catalyzed disproportionation of H2O2 by those clusters. A 2.0% Ti-HMS derivative prepared by direct assembly from tetraethylorthosilicate and tetraisopropylorthotitanate, denoted Ti-HMS(DS), was less active than Ti(IV)-functionalized mesostructures prepared by post-assembly grafting reaction with titanocene dichloride. Direct assembly places too much Ti(IV) at inaccessible positions within the framework walls, whereas grafting ensures optimal access to site-isolated Ti(IV) sites at the pore surfaces. [Copyright &y& Elsevier]

Abstract: Advanced heterogeneous catalysts for olefin metathesis were prepared by supporting Re(VII) oxide on (i) mesostructured γ-aluminas with lath-like and scaffold-like morphologies and (ii) organized mesoporous alumina with wormhole-like pore structure. The thermal spreading method was found to be very suitable technique for preparation of a highly active catalyst. In the case of dec-1-ene metathesis, Re(VII) oxide catalysts supported on mesoporous aluminas exhibited a high activity and selectivity independently of the type of catalyst support. For metathesis of olefin functional derivatives, namely p-allylanisole and diethyl diallylmalonate, the activity of Re(VII) catalysts with optimum amount of Re(VII) being 9.0wt% (with Me4Sn as co-catalyst) was found to depend on the catalyst pore size. Catalyst prepared from mesoporous aluminas with pore sizes at least 4.0nm exhibited much higher conversions of substrates compared with catalysts of 3.5nm pores. [Copyright &y& Elsevier]

Abstract: The in situ upgrading of biomass pyrolysis vapors with two mesoporous aluminosilicate materials (MSU-SBEA) assembled from zeolite Beta (BEA) seeds was tested in the present study, in comparison to conventional Al-MCM-41 and to non-catalytic biomass pyrolysis. The first sample (MSU-S/HBEA) exhibited an hexagonal mesopore structure while the second one (MSU-S/WBEA) possessed a wormhole-like mesopore structure with high textural porosity. The catalytic tests were performed on a fixed-bed reactor, the reaction temperature was 500°C and the feed was a lignocellulosic biomass based on beech wood. The use of the MSU-S catalytic materials led to significantly lower organic phase in the produced bio-oil and also to higher coke and char yields, compared to non-catalytic pyrolysis and to the use of Al-MCM-41 which induced a small increase in the yields of liquid oil and coke. Pyrolysis gases were also affected by all mesoporous catalysts. The MSU-S catalytic materials were very selective towards polycyclic aromatic hydrocarbons (PAHs) and heavy fractions, while they produced negligible amounts of acids, alcohols and carbonyls, and very few phenols. The MSU-S materials appeared to possess stronger acid sites than Al-MCM-41, resulting in enhanced yields of aromatics, PAHs and coke, as well as propylene in the pyrolysis gases. [Copyright &y& Elsevier]

Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO2)1-x(LSiO1.5)x, where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with worm hole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S ≤ 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBut)2. At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands. [ABSTRACT FROM AUTHOR]

A mesostructured γ-alumina with a lathlike framework morphology, denoted MSU-γ, has been prepared according to previously described methods through the reassembly and crystallization of a mesostructured alumina precursor with initially amorphous framework walls and used as a support for the catalytic hydrodesulfurization (HDS) of dibenzothiophene (DBT). The alumina support was loaded with molybdenum and cobalt ions via incipient wetness impregnation methods and then converted to the active sulfide form by reaction with H2S. HDS reactions of DBT were carried out at 400 °C and 400 psi to achieve a DBT conversion of 69–77% and a biphenyl (BP) product selectivity of 60–64% after a reaction time of 3 h, indicating that most of the DBT could undergo desulfurization while limiting excessive hydrogen consumption through aromatic hydrogenation. Although the dispersion of the active Mo/Co sulfide phase supported on lathlike MSU-γ alumina remained very high after several hours on stream, the conversions most likely were limited by a loss of surface area and porosity under HDS conditions. [Copyright &y& Elsevier]

FDU-1 silicas with large cage-like pores (diameter about 10 nm) were synthesized under acidic conditions from tetraethyl orthosilicate in the presence of a poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer template B50-6600 (EO[sub 39]BO[sub 47]EO[sub 39]). High-resolution transmission electron microscopy and small-angle X-ray scattering provided strong evidence that FDU-1 silica synthesized under typical conditions is a face-centered cubic Fm3m structure with 3-dimensional hexagonal intergrowth and is not a body-centered cubic lm3m structure, as originally reported. Samples synthesized in a wide range of conditions (initial temperatures from 298 to 353 K; hydrothermal treatment at 333-393 K) exhibited similar XRD patterns and their nitrogen adsorption isotherms indicated a good-quality cage-like pore structure. The examination of low-pressure nitrogen adsorption isotherms for FDU-1 samples, whose pore entrance diameters were evaluated using an independent method, allowed us to conclude that low-pressure adsorption was appreciably stronger for samples with smaller pore entrance sizes. This prompted us to examine low-pressure adsorption isotherms for a wide range of samples and led us to a conclusion that the FDU-1 pore entrance size can be systematically enlarged from about 1.3 nm (perhaps even lower) to at least 2.4 nm without an appreciable loss of uniformity by increasing the temperature of the hydrothermal treatment or the initial synthesis. Further enlargement of pore entrance size was achieved for sufficiently long hydrothermal treatment times at temperatures of 373 K or higher, as seen from the shape of nitrogen desorption isotherms. This allowed us to obtain samples with uniform pore sizes, high adsorption capacity, and with pore entrances enlarged so much that their size was similar to the size of the pore itself, resulting in a highly open porous structure. However, in the latter case, there was evidence that the pore... [ABSTRACT FROM AUTHOR]

Examines the effectiveness of framework sodium and local framework structure in determining the hydrothermal stability of MCM-41 mesostructures. Role of sodium ions in limiting the hydrothermal stability of the mesostructure; Device used in analyzing the MCM-41 mesostructures; Retention of residual sodium in the sodium silicate MCM-41.