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Mesoporous Materials (mesoporou + material)
Selected AbstractsEfficient Removal of Anionic Surfactants Using Mesoporous Functionalised Hybrid MaterialsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2009Carmen Coll Abstract A new hybrid system for surfactant removal from water has been developed using mesoporous material (MCM-41) functionalised with suitable binding groups. Solid S1, S2 and S3 were prepared by reaction of the mesoporous material with N -methyl- N, -(propyltrimethoxysilyl)imidazolium chloride, (3-aminopropyl)trimethoxysilane or 4-[(triethoxysilylpropylthio)methyl]pyridine, respectively. The functionalised materials were characterised following standard solid-state techniques. The final prepared solids consist of a siliceous MCM-41-type mesoporous support with the surface decorated by imidazolium, amine and pyridine binding groups suitable for anion coordination. Equilibrium adsorption studies of linear alkylbenzenesulfonate (LAS) using S1, S2 and S3 in water have been carried out. The obtained adsorption data were correlated with a Langmuir isotherm model that gives an acceptable description of the experimental data. The maximum surfactant uptake/binding site (mol,mol,1) and the surfactant adsorption capacity (mmol,g,1) for materials S1, S2 and S3 were calculated. S1 shows a positive-charged functionalised surface that is independent of the pH of the solution, whereas S2 and S3 are functionalised with neutral groups that need to be protonated in order to display electrostatic binding interactions with the anionic surfactants. Therefore, whereas the adsorption capacity of S1 is pH-independent, S2 and S3 display larger LAS adsorption at acidic pH. The adsorption ability at a certain pH follows the order S1 >> S3 > S2. A remarkable maximum surfactant adsorption of 1.5 mmol per gram of material was observed for S1 at neutral pH. S2 and S3 behave as poorer adsorbents and show maximum surfactant adsorption of 0.197 and 0.335 mmol per gram of material, respectively, at pH 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Krishanu Sarkar Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source] Synthesis of Rhodium Colloidal Nano-Coating Grafted Mesoporous Silica Composite and its Application as Efficient Environmentally Benign Catalyst for Heck-Type Reaction of Arylboronic AcidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2008Liang Li Abstract The synthesis and characterization of rhodium colloidal layer grafted mesoporous SBA-15 material, designated as SBA-Rh, are presented. In the preparation of this new catalyst, SBA-15 mesoporous material was used as support without any pretreatment. The SiH functional groups were introduced onto the surface which resulted in highly dispersed metal colloid layer both on the outer and inner surface of the supporting material. The material was investigated for Heck-type coupling reactions of alkenes with ayboronic in organic/water solvent. The ultrahigh specific area, large pore opening, and highly dispersed catalyst species in SBA-Rh material created one of the most active heterogeneous catalysts for such reactions. Rhodium element was not detected in the final mixture by ICP after reaction. The catalyst species showed very high stability against leaching from the matrix and can be recycled for repeated use. [source] Absolute enantioselective separation: Optical activity ex machinaJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2005Roman Bielski Abstract The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. [source] Synthesis of Ionic Liquid Functionalized SBA-15 Mesoporous Materials as Heterogeneous Catalyst toward Knoevenagel Condensation under Solvent-Free ConditionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2006Yong Liu Abstract 1-Methyl-3-propylimidazolium chloride (MPImCl) and 1-propylpyridinium chloride (PPyCl) ionic liquid functionalized SBA-15 mesoporous materials were synthesized and used as heterogeneous catalysts in Knoevenagel reactions with excellent yields and reusability. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] High-Zirconium-Content Nano-Sized Bimodal Mesoporous SilicasEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2006David Ortiz de Zárate Abstract Silica-based nanoparticulated bimodal mesoporous materials with high Zr content (43 , Si/Zr , 4) have been synthesized by a one-pot surfactant-assisted procedure from a hydroalcoholic medium using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes of Zr and Si as hydrolytic inorganic precursors. This preparative technique allows optimization of the dispersion of the Zr guest species in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N2 adsorption,desorption isotherms. The small intraparticle mesopore system (with pore sizes around 2,3 nm) is due to the supramolecular templating effect of the surfactant, while the large mesopores (around 12,24 nm) have their origin in the packing voids generated by aggregation of the primary nanometric mesoporous particles. The basicity of the reaction medium seems to be a key parameter in the definition of this last pore system. The effects induced by the progressive incorporation of Zr atoms on the mesostructure have been examined, and the local environment of the Zr sites in the framework has been investigated by UV/Vis spectroscopy. Observations based on the consequences of post-treatments of the as-synthesized materials with HCl/ethanol mixtures corroborate that the atrane method leads to Zr-rich materials showing enhanced site accessibility and high chemical homogeneity throughout the pore walls. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A Single-Source-Precursor Approach to Late Transition Metal Molybdate Materials: The Structural Role of Chelating Ligands in the Formation of Heterometallic Heteroleptic Alkoxide ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Pia Werndrup Abstract The synthesis and structural determination of three new heterometallic molybdenum complexes, one with cobalt and two with nickel and two of these with ,-diketonate ligands and one with amino alcohol ligands, are presented. The reaction of cobalt acetylacetonate with [MoO(OMe)4] provides [Co2Mo2O2(acac)2(OMe)10] (1) and [MoO(acac)(OMe)3] (4),and the reaction of nickel acetylacetonate with [MoO(OMe)4]provides [Ni2Mo2O2(acac)2(OMe)10] (2) and 4. The reaction of [Ni(ORN)2] (RN = CHMeCH2NMe2) with [MoO(OMe)4] yields [Ni2Mo2O2(ORN)2(OMe)10] (3). The two new oxomolybdenum complexes undergo ether elimination upon storage to give the corresponding dioxo complexes [MoO2(acac)(OMe)]2 (5) and [MoO2(ORN)(OMe)]2 (6). Compounds 3 and 4 could also be obtained from the reaction of stoichiometric amounts of Hacac with [MoO(OMe)4] and [MoO2(OMe)2], respectively. The local structure around the nickel atom in compound 2 in solution and compound 3 in the solid state and in toluene/hexane solution has been determined by means of EXAFS spectroscopy. The complexes are intended to be used as single-source precursors, which are attractive in coatings and for the preparation of mesoporous materials; its application for the synthesis of nickel molybdate by sol,gel processing is therefore reported. The oxide material obtained from 3 displays a uniform grain size and a large surface area. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Organically Functionalized Mesoporous Silica by Co-structure-Directing RouteADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Chuanbo Gao Abstract This article provides a brief overview of functional mesoporous silica materials synthesized by the co-structure-directing route, which is distinct from conventional synthesis strategies. In these systems, organosilane serves as the co-structure-directing agent (CSDA), which provides critical interactions between the template and organic part of the organosilane to form mesostructures, thus retaining the organic groups on the pore surface after removal of the template by extraction. i) The formation of anionic-surfactant-templated mesoporous silicas (AMSs) has been achieved by the co-structure-directing route, which leads to a variety of mesostructures, porous properties and morphologies. ii) Other co-structure-directing systems for synthesizing mesoporous silicas have also been achieved, including systems using cationic surfactants and non-surfactants, and systems using DNA for constructing nanofibers and DNA,silica liquid crystalline complexes. iii) Evidence for the regular arrangement of functional groups on the pore surface resulted from the co-structure-directing effect has been discussed. Also included is a brief description of the application, future requirements, and trends in the development of mesoporous materials by the co-structure-directing route. [source] Polysaccharide-Derived Carbons for Polar Analyte SeparationsADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Robin J. White Abstract Highly mesoporous (Brunauer,Emmett,Teller surface area, SBET,>,200,m2,g,1; mesopore volume,>,1,cm3,g,1) carbonaceous materials are prepared in a truly sustainable manner, from the naturally occurring polysaccharide alginic acid. This approach yields large mesoporous materials (pore diameter,>,14,nm) significantly without the use of a template or carbonization catalyst. The direct thermal decomposition of mesoporous forms of the acidic polysaccharide allows for an extremely flexible material preparation strategy. Materials can be prepared at any desired carbonization temperature (e.g., 200,1000,°C), possessing similar textural properties, but progressively presenting more uniform surface functionality through this temperature range, from more oxygenated surfaces at low temperatures to increasingly aromatic/graphitic-like surfaces. The high-temperature material (i.e., 1000,°C), while predominantly amorphous, presents some short range (turbostratic) ordering, providing sufficiently polarizable surfaces on which to perform challenging liquid phase separations of polar sugar analytes. [source] Template Synthesis of Hierarchically Structured Composites,ADVANCED MATERIALS, Issue 15 2008Wei Wei Abstract The subtle performance of a virus is closely related to its specific hierarchical structure, which is composed of a rigid shell and transverse, responsive, nanometer-sized channels. Virus-like structured colloids are of great interest for their potential applications, for example in drug delivery. Adequate knowledge of the structure and composition control of both colloids and mesoporous materials is significant in the design and synthesis of hierarchically structured colloids to mimic viruses. Some recent developments in the synthesis of composite colloids and mesoporous materials are summarized. Template synthesis is a major tool to control both the macroscopic morphology and microstructures of these composites, in which gel colloids and supramolecular structures from amphiphilic species are used as templates. [source] In-Situ Coating of SBA-15 with MgO: Direct Synthesis of Mesoporous Solid Bases from Strong Acidic Systems,ADVANCED MATERIALS, Issue 22 2003Y.L. Wei Basic mesoporous materials (see Figure) are synthesized directly from a strong acidic solution for the first time. This is achieved by in-situ coating of SBA-15 with basic MgO by adding acetate salt into the initial mixture of raw materials for synthesis. The synthesis and modification is performed in a one-step procedure. The magnesium acetate not only acts as the precursor of MgO, but also leads to a better order in the mesostructure. [source] Dynamic Charge Equilibration-Morse stretch force field: Application to energetics of pure silica zeolitesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2002Jan Sefcik Abstract We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to ,-quartz are within 2 kJ/mol and entropies at 298 K are within 3 J/mol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about 1 kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1507,1514, 2002 [source] A Study on the Effect of Template Chain Length on the Synthesis of Mesoporous Silica in An Acidic ConditionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Yang Yu-Xiang Hexagonal mesoporous silica materials were synthesized in an acidic medium using different chain length of the quaternary ammonium surfactants as a template. The effects of chain length on the physical property, morphology of mesoporous materials, and the temperature on synthesis of materials in CnTMBr,TEOS,HNO3,H2O (n=12,14,16,18) system were systematically studied. The synthesized products were characterized by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was found that degree of ordering, the d spacing values, and pore size all increase with an increase in the chain length of the template. The optimum synthesis temperature for mesoporous silica using C18TMBr,TEOS,HNO3,H2O system is slightly higher than the Krafft point. The temperature and pH can all affect the expandability of micelles, and so an increase in temperature and decrease in pH all lead to an increase in the pore size. It is also found that the shear flow and chain length are two key factors inducing the formation of millimeter-scaled silica ropes and micrometer-scaled rope fibers. [source] Combinatorial Electrochemical Synthesis and Screening of Mesoporous ZnO for PhotocatalysisMACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2004Thomas F. Jaramillo Abstract Summary: Automated electrochemical synthesis was used to create combinatorial libraries of mesoporous materials using tri-block copolymers as structure directing agents (SDA). An example library of 56 ZnO samples was synthesized, varying concentrations (0,15 wt.-%) of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) , EO20PO70EO20. High-throughput photoelectrochemical screening for the measurement of water-splitting photocatalysis identified peak performance at 3 wt.-% of the SDA. Lamellar structures and disordered mesopores were observed by TEM and XRD. [source] Preparation and characterization of mesoporous materials based on silsesquioxane by block copolymer templating,POLYMER INTERNATIONAL, Issue 11 2002Byeong-Gyu Park Abstract Nanoporous materials were prepared by using silsesquioxane containing three alkoxy groups and a non-hydrolysable organic moiety. The influences of pH and precursor ratios of silsesquioxane and tetraethyl orthosilicate (TEOS) on the preparation of organo-modified periodic mesoporous materials were investigated. These materials were characterized using small angle X-ray scattering, infrared spectroscopy and thermogravimetric analysis. A non-ionic triblock copolymer was used as a structure-directing agent to provide large pores with a high density of silanol groups. It was found that silsesquioxanes could form ordered nanoporous materials in the presence of TEOS by controlling the pH and the co-precursors ratio, despite their structural irregularity. © 2002 Society of Chemical Industry [source] Organic,inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology controlTHE CHEMICAL RECORD, Issue 1 2006Sung Soo Park Abstract Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host,guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic,inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic,inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0,Å by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic,inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu3+ and Tb3+) are used to modify organic,inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 32,42; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20070 [source] Structural Evolvement of Heating Treatment of Mg/Al-LDH and Preparation of Mineral Mesoporous MaterialsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2006CHEN Tianhu Abstract, Although hydrotalcite, or layered double hydroxides (LDHs), is not a common mineral, it is an important material that can be easily synthesized in laboratory. In this study, structural evolvement and BET surface area changes of heat treated Mg/Al-LDH is evaluated by XRD, TEM and N2 -BET analyses. The results indicate that the magnesium-aluminum LDH with carbonate as interlayer anion, periclase-like oxides was formed at temperatures of 400,800°C. Meanwhile, 2,3 nanometer mesoporous were formed during decomposition of LDH. However, the heat treated samples still preserve the morphology of the original LDH plates. Periclase-like formed from LDH heat treatment may re-hydrolyze and recover the structure of LDH. However, crystallinity of the recovered LDH is lower than that of the original LDH. This heat treatment will result in formation of (Mg, Al)-oxide nano-crystals and nanopores among the nano-crystals. When heating temperature exceeds 1000, the periclase-like (Mg, Al)-oxide is transformed into a composite with periclase (MgO) and spinel phases. The periclase can be re-hydrolyzed and dissolved in HCI solution. After acid treatment, the sample with a high surface area is composed of spinel nano-crystals and nanopores among them. Our results will provide a new and economic way to synthesize mesoporous materials through pathways of phase transformation of precursor materials with different composition. [source] Formation of Furfural in Catalytic Transformation of Levoglucosan over Mesoporous MaterialsCHEMCATCHEM, Issue 5 2010M. Käldström Abstract Catalytic transformations of levoglucosan (1-6-anhydro-,- D -glucopyranose) and furfural were carried out in a fixed-bed reactor at 573,K over mesoporous materials. Proton forms of MCM-41, MCM-48, SBA-15, and platinum form of MCM-48 catalysts were tested in the reaction, whereas H-Beta and quartz sand were used as reference materials. The yield of the transformation products was substantially influenced by the catalyst structures. Oxygenated species were the main liquid products, consisting mainly of aldehydes and furfural. The formation of furfural was the highest over MCM-41 catalyst followed by SBA-15, MCM-48, and H-Beta catalyst. All catalysts were to some extent deactivated due to coke formation. However, it was possible to successfully regenerate the spent catalysts without changing the structure. [source] Micelle-to-Vesicle Transition Induced by Organic Additives in Catanionic Surfactant SystemsCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006Haiqing Yin Abstract A micelle-to-vesicle transition (MVT) induced by the addition of a series of apolar hydrocarbons (n -butylbenzene, n -hexane, n -octane, and n -dodecane) to the catanionic surfactant system n -dodecyltriethylammonium bromide/sodium n -dodecylsulfate (DTEAB/SDS) has been investigated for the first time by means of rheology and turbidity measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Interestingly, a MVT can take place within certain micellar regions, which are dependent on the structure and chain length of the hydrocarbon. However, these hydrocarbons are unable to induce a MVT in another catanionic surfactant system, namely, n -dodecyltriethylammonium bromide/sodium n -dodecylsulfonate (DTEAB/SDSO3), in which the molecular interactions are weaker than in the DTEAB/SDS system. On the other hand, polar additives, such as n -octanol and n -octylamine, exhibit much higher efficiency and activity in inducing MVT than hydrocarbons in both DETAB/SDS and DTEAB/SDSO3. Moreover, DLS, TEM, and time-resolved fluorescence quenching (TRFQ) results demonstrate that the ratio of vesicles to micelles in the system can be actively controlled by addition of polar additives. Possible mechanisms for the above phenomena are presented, and the potential application of controllable micelle/vesicle systems in the synthesis of tailored bimodal mesoporous materials is discussed. [source] Highly Ordered Mesoporous Carbonaceous Frameworks from a Template of a Mixed Amphiphilic Triblock-Copolymer System of PEO,PPO,PEO and Reverse PPO,PEO,PPOCHEMISTRY - AN ASIAN JOURNAL, Issue 10 2007Yan Huang Abstract A series of highly ordered mesoporous carbonaceous frameworks with diverse symmetries have been successfully synthesized by using phenolic resols as a carbon precursor and mixed amphiphilic surfactants of poly(ethylene oxide)- b -poly(propylene oxide)- b -poly(ethylene oxide) (PEO,PPO,PEO) and reverse PPO,PEO,PPO as templates by the strategy of evaporation-induced organic,organic self-assembly (EISA). The transformation of the ordered mesostructures from face-centered (Fdm) to body-centered cubic (Imm), then 2D hexagonal (P6mm), and eventually to cubic bicontinuous (Iad) symmetry has been achieved by simply adjusting the ratio of triblock copolymers to resol precursor and the relative content of PEO,PPO,PEO copolymer F127, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen-sorption measurements. The blends of block copolymers can interact with resol precursors and tend to self-assemble into cross-linking micellar structures during the solvent-evaporation process, which provides a suitable template for the construction of mesostructures. The assembly force comes from the hydrogen-bonding interactions between organic mixed micelles and the resol-precursor matrix. The BET surface area for the mesoporous carbonaceous samples calcined at 600,°C under nitrogen atmosphere is around 600,m2,g,1, and the pore size can be adjusted from 2.8 to 5.4,nm. An understanding of the organic,organic self-assembly behavior in the mixed amphiphilic surfactant system would pave the way for the synthesis of mesoporous materials with controllable structures. [source] Mesoporous Pt,SiO2 and Pt,SiO2,Ta2O5 Catalysts Prepared Using Pt Colloids as TemplatesCHEMPHYSCHEM, Issue 5 2007Vasile I. Pârvulescu Prof. Dr. Abstract Sol-gel synthesis of silica and silica,tantalum oxide embedded platinum nanoparticles is carried out using Pt colloids as templates. These colloids are prepared by reduction with Na[AlEt3H] and stabilized with different ligands (ammonium halide derivatives, non-ionic surfactants with polyether chains, and 2-hydroxy-propionic acid). The aim of the present study is to prepare mesoporous silica embedded Pt colloids combining the "precursor concept" with the model of catalyst preparation using preformed spheres. Nanoparticles of Pt incorporated in high surface area mesoporous materials are formed after calcination. Further, it is observed that calcination of these catalysts causes partial aggregation and oxidation of the parent colloids, a process that is largely dependent on the nature of the stabilizing ligands. Several methods have been used for characterization of these materials: adsorption-desorption isotherms at 77 K, H2 chemisorption, X-ray diffraction(XRD), 29Si and 13C magic angle spinning (MAS) NMR, ammonia diffuse reflectance Fourier transform infrared spectroscopy (NH3 -DRIFT), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It is found that both metal oxide systems exhibit Brønsted acidity (weaker for silica and quite strong for silica,tantalum oxide). In addition, NH3 -DRIFT experiments demonstrate the oxidative properties of the surface. Part of the adsorbed NH4+ species is oxidized to N2O. Testing these catalysts in the reduction of NO and NO2 with isopentane under lean conditions indicate that the activity of these catalysts is indeed dependent on the size of the platinum particles, with those of size 8,10 nm demonstrating the best results. The support likely contributes to this effect, particularly after Ta incorporation into silica. [source] Removal of Copper-phthalocyanine from Aqueous Solution by Cationically Templated MCM-41 and MCM-48 Nanoporous AdsorbentsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2008Mansoor ANBIA The effect of cationic template on the adsorption of copper-phthalocyanine-3,4,,4,,,4,,,-tetrasulfonic acid tetrasodium salt [Cu(tsPc),4·4Na+] in MCM-41 and MCM-48 mesoporous materials was investigated, using cetyltrimethylammonium bromide (CTAB) as the cationic template and tetraethyl-orthosilicate as the silica source for synthesis of mesoporous materials. The properties of synthesized samples were characterized with XRD-low angle and scanning electron microscopy. The as-synthesized mesoporous samples were used for the separation of Cu(tsPc),4·4Na+ from aqueous solution, which showed very high adsorption capacity for it. [source] | |||||||||||||