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PHYSICS (546 journals)            First | 1 2 3 4 5 6 | Last

Journal of Research in Physics     Open Access  
Journal of Rheology     Full-text available via subscription   (Followers: 4)
Journal of Romance Studies     Full-text available via subscription   (Followers: 2)
Journal of Sandwich Structures and Materials     Hybrid Journal   (Followers: 1)
Journal of Scientific Research     Open Access   (Followers: 1)
Journal of Semiconductors     Full-text available via subscription   (Followers: 2)
Journal of Sensors     Open Access   (Followers: 7)
Journal of Sol-Gel Science and Technology     Hybrid Journal   (Followers: 2)
Journal of Solid State Lighting     Open Access  
Journal of Solid State Physics     Open Access  
Journal of Spectroscopy     Full-text available via subscription  
Journal of Superconductivity and Novel Magnetism     Partially Free   (Followers: 1)
Journal of Synchrotron Radiation     Hybrid Journal   (Followers: 1)
Journal of Testing and Evaluation     Full-text available via subscription   (Followers: 10)
Journal of the American Society for Mass Spectrometry     Hybrid Journal   (Followers: 17)
Journal of the Brazilian Society of Mechanical Sciences     Open Access   (Followers: 1)
Journal of the ICRU     Hybrid Journal  
Journal of the Korean Physical Society     Partially Free   (Followers: 1)
Journal of Theoretical and Applied Physics     Open Access   (Followers: 1)
Journal of Tissue Engineering     Open Access   (Followers: 4)
Journal of Ultrasound in Medicine     Full-text available via subscription   (Followers: 3)
Journal of Vibration and Control     Hybrid Journal   (Followers: 16)
Journal of Visualization     Hybrid Journal   (Followers: 2)
Journal of Zhejiang University SCIENCE A     Hybrid Journal  
Jurnal Penelitian Sains (JPS)     Open Access  
Language Learning Journal     Hybrid Journal   (Followers: 12)
Lasers in Surgery and Medicine     Hybrid Journal  
Latvian Journal of Physics and Technical Sciences     Open Access  
Learning Technologies, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Les Houches Summer School Proceedings     Full-text available via subscription  
Letters in Mathematical Physics     Hybrid Journal   (Followers: 3)
Light : Science & Applications     Open Access  
Living Reviews in Relativity     Open Access  
Living Reviews in Solar Physics     Open Access  
Lubrication Science     Hybrid Journal  
Macalester Journal of Physics and Astronomy     Open Access  
Machining Science and Technology: An International Journal     Hybrid Journal   (Followers: 2)
Magnetic Resonance Materials in Physics, Biology and Medicine     Hybrid Journal   (Followers: 1)
Magnetics Letters, IEEE     Hybrid Journal   (Followers: 3)
MAPAN     Hybrid Journal  
Mass Spectrometry Reviews     Hybrid Journal   (Followers: 17)
Matéria (Rio de Janeiro)     Open Access   (Followers: 1)
Materials & Design     Hybrid Journal   (Followers: 29)
Materials at High Temperatures     Full-text available via subscription   (Followers: 4)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 12)
Materials Research     Open Access   (Followers: 7)
Materials Research Bulletin     Hybrid Journal   (Followers: 17)
Materials Science     Hybrid Journal   (Followers: 7)
Materials Science and Engineering: A     Hybrid Journal   (Followers: 33)
Materials Science and Engineering: B     Hybrid Journal   (Followers: 17)
Materials Science and Engineering: C     Hybrid Journal   (Followers: 16)
Materials Science and Engineering: R: Reports     Hybrid Journal   (Followers: 11)
Matériaux & Techniques     Full-text available via subscription   (Followers: 1)
Mathematical Physics, Analysis and Geometry     Hybrid Journal   (Followers: 1)
Mathematics and Mechanics of Solids     Hybrid Journal   (Followers: 2)
Meccanica     Hybrid Journal   (Followers: 1)
Mechanics of Advanced Materials and Structures     Hybrid Journal   (Followers: 3)
Mechanics of Materials     Hybrid Journal   (Followers: 12)
Mechanics of Time-Dependent Materials     Hybrid Journal   (Followers: 1)
Mechanics Research Communications     Hybrid Journal   (Followers: 2)
Metamaterials     Hybrid Journal   (Followers: 2)
Micro and Nano Systems Letters     Open Access   (Followers: 3)
Microfluidics and Nanofluidics     Hybrid Journal   (Followers: 9)
Microporous and Mesoporous Materials     Hybrid Journal   (Followers: 3)
Modern Instrumentation     Open Access   (Followers: 3)
Modern Physics Letters A     Hybrid Journal   (Followers: 1)
Modern Physics Letters B     Hybrid Journal  
Molecular Diversity     Hybrid Journal  
Moscow University Physics Bulletin     Hybrid Journal  
Multibody System Dynamics     Hybrid Journal   (Followers: 1)
NANO     Hybrid Journal   (Followers: 7)
Nano Letters     Full-text available via subscription   (Followers: 43)
Nano Reviews     Open Access   (Followers: 15)
Nanoscale and Microscale Thermophysical Engineering     Hybrid Journal   (Followers: 3)
Nanoscale Research Letters     Open Access   (Followers: 4)
Nanotechnology Magazine, IEEE     Full-text available via subscription   (Followers: 14)
Natural Science     Open Access   (Followers: 9)
Nature Communications     Hybrid Journal   (Followers: 41)
Nature Materials     Full-text available via subscription   (Followers: 42)
Nature Physics     Full-text available via subscription   (Followers: 24)
NDT & E International     Hybrid Journal   (Followers: 13)
NEUTRINO     Open Access  
Neutron News     Hybrid Journal  
New Journal of Physics     Open Access   (Followers: 7)
Niels Bohr Collected Works     Full-text available via subscription  
Noise & Vibration Worldwide     Full-text available via subscription   (Followers: 5)
Noise Notes     Full-text available via subscription   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin     Hybrid Journal   (Followers: 4)
Nuclear Engineering and Design     Hybrid Journal   (Followers: 12)
Nuclear Medicine and Biology     Hybrid Journal   (Followers: 1)
Nuclear Receptor     Full-text available via subscription   (Followers: 1)
Open Journal of Biophysics     Open Access   (Followers: 1)
Open Journal of Fluid Dynamics     Open Access   (Followers: 3)
Open Journal of Microphysics     Open Access  
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 4)
Organic Electronics     Hybrid Journal   (Followers: 3)
PAJ: A Journal of Performance and Art     Hybrid Journal   (Followers: 11)
Particle Physics Insights     Open Access   (Followers: 2)

  First | 1 2 3 4 5 6 | Last

Journal Cover Microporous and Mesoporous Materials
   [5 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1387-1811
     Published by Elsevier Homepage  [2573 journals]   [SJR: 1.306]   [H-I: 93]
  • [Ti,Zr]-pillared montmorillonite – A new quality with respect to Ti-
           and Zr-pillared clays
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): K. Bahranowski , W. Włodarczyk , E. Wisła-Walsh , A. Gaweł , J. Matusik , A. Klimek , B. Gil , A. Michalik-Zym , R. Dula , R.P. Socha , E.M. Serwicka
      Mixed titanium–zirconium pillared montmorillonite [Ti,Zr]-PILC and reference Ti-PILC and Zr-PILC were synthesized and characterized with XRD, XRF, diffuse reflectance UV–Vis, XPS and Raman spectroscopies, thermal analysis, N2 adsorption/desorption at −196°C, NH3 TPD–MS, and FTIR monitored pyridine adsorption. Results indicate that pillars in [Ti,Zr]-PILC represent quasi-amorphous mixed Ti–Zr oxide, of short range order similar to that of a zirconium titanate phase. The size of intercalated mixed Ti–Zr cationic species is intermediate between that of Ti and Zr polycations. A new evidence is presented on the nature of pillars and their relationship to the clay sheets. It is demonstrated that in Ti-PILC material titanium sites present at the clay/pillar interface assume tetrahedral coordination, while in [Ti,Zr]-PILC they retain coordination number higher than 4. Textural studies suggest that mixed Ti–Zr-pillars are structurally better defined and more uniform than those formed upon intercalation of the Ti-pillaring sol, and resemble in this respect pillars derived from zirconium oligocations. Measurements of surface acidity prove that a new quality appears in the surface chemistry of oxide props present in [Ti,Zr]-PILC. Although, similarly as in the case of Ti-PILC and Zr-PILC references, the acidity is predominantly of the Lewis type, the [Ti,Zr]-PILC sample possesses a significant population of Lewis acid sites which are much stronger than those present in the reference materials. Results of this study show that uniqueness of structural, textural and surface acid–base properties of mixed titanium–zirconium pillared montmorillonite render this material very attractive from the point of view of potential applications in sorption and catalysis.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Modeling the influence of the operating conditions upon the sorption rate
           and the yield in the adsorption of lead(II)
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): L. Largitte , P. Lodewyckx
      Alkaline activated carbon from Coconut (Cocos nucifera) shells and acid activated carbon from Bois carré (Citharexylum fruticosum L.) seeds have been prepared and tested for the sorption of lead. The efficiency of the adsorption depends on the value of the rate constant k, relative to the sorption rate, and, depends also on the value of the equilibrium constant K, relative to the sorption yield. Higher are these constants, higher the adsorption efficiency. Moreover, the adsorption results depend on the operating conditions. So, the influence of temperature, initial pH, initial lead concentration and adsorbent dose on the rate constant and on the equilibrium constant are investigated onto these two activated carbons. The results show, for the activated carbon from Bois carré seeds, that increasing the temperature increases the sorption rate and decreases the adsorption capacity, increasing the pH increases the sorption rate while the sorption capacity remains constant, increasing the lead initial concentration decreases the sorption rate and increases the sorption capacity and increasing the adsorbent dose decreases the sorption capacity while the sorption rate passes through a maximum. Moreover, the study shows that linear equations describing the behavior of the rate constant and the equilibrium constant upon the operating parameters can be found. The knowledge of these equations will permit to determine the optimum operating conditions and to predict the sorption results under these operating conditions range (temperature, initial pH, initial concentration, adsorbent dose) without having to refer to supplementary experiments.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • BTX sorption on Na-P1 organo-zeolite as a process controlled by the amount
           of adsorbed HDTMA
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Barbara Szala , Tomasz Bajda , Jakub Matusik , Katarzyna Zięba , Beata Kijak
      The main objective of the study was to utilize fly ash by transforming it into Na-P1 zeolite. The obtained synthetic zeolite has been modified with a HDTMA surfactant in amounts of: 0.2, 0.4, 0.6, 0.8 and 1.0 of external cation exchange capacity (ECEC). The process reported hereunder was designed at room temperature (20°C) and a low solid/solution ratio (1:2). Infrared spectroscopy (FTIR) was used to determine the quantity of the adsorbed surfactant on the crystallites’ surface. The normalized intensity of the selected bands was compared with CHN results. The results revealed a very strong correlation between spectroscopic and chemical analyses and enabled the preparation of calibration curves. The sorption properties of organo-zeolites towards benzene, toluene, p-xylene (BTX) were evaluated. The results showed that the modification of the Na-P1 zeolite by HDTMA improves the sorption properties in terms of benzene and toluene and that 1.0 ECEC modification proved to be the best sorbent of those compounds. Xylene was adsorbed in the greatest quantity, however, sorption efficiency from aqueous solutions does not depend on the amount of surfactant used. Experiments proved that it is possible to remove more than 95% of toluene and xylene and more than 85% of benzene contaminants from aqueous solutions.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Encapsulation of copper and zinc oxide nanoparticles inside small diameter
           carbon nanotubes
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Dennis Großmann , Axel Dreier , Christian W. Lehmann , Wolfgang Grünert
      Copper and zinc oxide nanoparticles have been reproducibly deposited into carbon nanotubes (CNT) of 6–7nm internal diameter via simple impregnation techniques with different metal salts followed by thermal decomposition of the precursors and reduction in H2 in case of Cu. Oxygen functionalization via a gas-phase method involving thermal shocks was a critical step while traditional functionalization with nitric acid resulted in failures. Intra-CNT location of CuO particles could be proven by STEM images, and was examined by TEM for materials prepared by various routes. It was found that Cu and Zn oxide nanoparticles could be deposited throughout the whole interior CNT space. The filling capacity depended on the preparation conditions, on conditions of subsequent precursor decomposition, and on the inner diameter of the CNTs. After the reduction of the CuO nanoparticles, XRD, XAFS, and N2O reactive frontal chromatography indicated a bimodal particle size distribution due to the presence of agglomerates outside the CNTs. To enhance selectivity for endohedral location, a washing step with HNO3 with the inner CNT space blocked by xylene was applied to selectively remove aggregates in the outer space. Based on the best procedures for introduction of CuO and ZnO, a bimetallic CuZnO@CNT sample was prepared via a consecutive preparation route.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Incorporation of Al at ZSM-5 hydrothermal synthesis. Tuning of Al pairs in
           the framework
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Veronika Pashkova , Petr Klein , Jiri Dedecek , Věnceslava Tokarová , Blanka Wichterlová
      The effect of Si- (TEOS, Tixosil and Na-silicate), Al- (AlCl3, Al(NO3)3, NaAlO2, Al(OH)3 and metallic Al) and Na-reactants (NaCl, NaOH, Na3PO4, NaAlO2) in the presence of TPAOH was investigated with regard to the networking of Si and Al atoms in gels and incorporation of Al atoms and their distribution in the hydrothermally synthesized ZSM-5 framework. At Si/Alprod from 12 to 60 the Al–Si–Si–Al sequences (Al pairs) in one 6MR and single Al atoms located in different rings were the most populated (>99% of total Al), reaching 4–70% of the Al atoms in Al pairs in 6MRs adjacent to TPA+. It has been shown that Na+ ions stabilize single SiAlO4 − units in Si–Al gels network and lead to a high relative degree of Al incorporation and high population of single Al atoms charge-balanced by TPA+ and Na+ ions. The occurrence of Al pairs in 6MRs is suggested to be controlled by the positive charge on the N atom of TPA+ resulting from its polarization by OH− and other anions present. The decreasing polarization ability of OH− >Cl− ∼PO4 3− >NO3 − anions present next to OH− reduces the charge on N+ and results in a decreasing population of Al pairs and increasing population of single Al atoms located in the vicinity of TPA+ ions.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Synthesis of hierarchical porous silicalite-1 and its catalytic
           performance in Beckmann rearrangement
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Chengyang Yin , Rui Ni , Xia Bao , Yonghong Chen
      Hierarchical porous silicalite-1 with micropores and mesopores was successfully synthesized via dry gel conversion route using tetrapropylammonium hydroxide (TPAOH) and polyvinyl alcohol (PVA) as microporous and mesoporous templates, respectively. The obtained hierarchical porous silicalite-1 was characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characteristics of the samples are comparable with conventional silicalite-1. The influence of the PVA on the hierarchical porous properties of the samples was investigated. The hierarchical porous silicalite-1 showed higher activity and selectivity than conventional silicalite-1 in vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam under reaction condition.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Modulation of folic acid bioaccessibility by encapsulation in
           pH-responsive gated mesoporous silica particles
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Édgar Pérez-Esteve , Ana Fuentes , Carmen Coll , Carolina Acosta , Andrea Bernardos , Pedro Amorós , María D. Marcos , Félix Sancenón , Ramón Martínez-Máñez , José M. Barat
      A study on the controlled release of folic acid (FA) from pH-responsive gated mesoporous silica particles (MSP) is reported. The MCM-41 support was synthesized using tetraethyl orthosilicate (TEOS) as hydrolytic inorganic precursor and the surfactant hexadecyltrimethylammonium bromide (CTAB) as porogen species. Calcination of the mesostructured phase resulted in the starting solid. This solid was loaded with FA to obtain the initial support S0. Moreover, this FA-loaded material was further functionalized with 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (N3) in order to obtain the gated polyamine-functionalised material S1. Solids S0 and S1 were characterized using standard solid state procedures. It was found that the functionalization process and the inclusion of FA on the pores did not modify the mesoporous structure of the starting material. FA delivery studies in water with solids S0 and S1 were carried out in water at pH 2 and 7.5. S0 was not able to completely inhibit FA delivery at acidic pH yet a rapid FA release at neutral pH was observed in few minutes. In contrast, S1 was tightly capped at pH 2 and displayed a sustained delivery of FA when the pH was switched to 7.5. In the second part of the study, FA loading and functionalization of S1-like supports was optimized. In particular, solids loaded with FA in phosphate buffered saline (PBS) and capped with N3 in acetate buffer at pH 2 exhibited a delivery capacity up to 95μg FA/mg solid. Finally, FA release from the selected optimized supports was studied following an in vitro digestion procedure. The results showed that amine-capped MSP were not only able to hinder the release of the vitamin in gastric fluids (pH 2), but were also capable of deliver progressively the FA in presence of a simulated intestinal juice (pH 7.5) offering a suitable mechanism to control the bioaccessibility of the vitamin.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • The buckling deformation and mechanical properties of aerogels prepared
           with polyethoxydisiloxane
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Guodong Jiang , Maohong Fan , Xiaodong Shen , H. Gordon Harris , Saeed Danaei Kenarsari
      The high-polymeric degree or molecular-weight of self-made polyethoxydisiloxane (PEDS) was successfully used to synthesize aerogels with several advantageous mechanical characteristics, compared with those based on conventional tetraethylorthosilicate (TEOS) aerogel preparation methods. The first advantage is their lower initial values of bulk modulus (K 0), compared with those prepared via the two-step method; this is due to release of internal stress during the shrinkage of wet gel. Secondly, a collapse index n of −0.125 is obtained by the collapse law; this implies a new buckling destruction model. This is different from those prepared via the two-step method, and suggests that a hierarchical filament structure, formed by the connection of nano-particles, constitutes the solid skeleton of pores. In this paper, average aerogel pore sizes between 16.0 and 39.3nm are analyzed by the combination of Mercury Intrusion Porosimetry (MIP) and Nitrogen Adsorption–Desorption (NAD). The microstructure and morphology of the aerogels are demonstrated by Transmission Electron Microscopy (TEM) and Field Emission Scan Electron Microscopy (FE-SEM).
      Graphical abstract image Highlights

      PubDate: 2014-10-11T09:28:02Z
       
  • Sensing and magnetic removal of Hg(II) using core–shell structured
           nanocomposite grafted with fluorescence “Off–On” probe
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Yang Jing-po , Lu Fei , Chen Jing , Yang Jin-di
      This paper reported the preparation, characterization, Hg(II) sensing and removal performance of a core–shell structured nanocomposite grafted with rhodamine derived probe. The inner core was composed of superparamagnetic Fe3O4 nanoparticles and responsible for magnetic removal. The outer shell was composed of silica molecular sieve MCM-41 having large surface area and highly ordered tunnels. The Hg(II) sensing probe was derived from rhodamine 6G which showed emission “Off–On” effect towards Hg(II), owing to structural transformation from a non-emissive one to a highly emissive one. The nanocomposite was fully characterized by electron microscopy images, XRD analysis, thermogravimetric analysis and N2 adsorption/desorption isotherms. It was found that nanocomposite emission increased with increasing Hg(II) concentrations, showing emission “Off–On” effect. In addition, this nanocomposite owned high selectivity and fast response towards Hg(II) owing to its large surface area and highly ordered tunnels.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Effect of distribution of phase transfer catalysts in the microreactor
           shells on the catalytic oxidation of dibenzothiophene
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Juxiang Yang , Daodao Hu , Wei Li , Xing Yang
      Two kinds of microreactors using the porous and imperforate poly(acrylamide-co-methacrylic acid) (P(AM-co-MAA)) microgels as cores and the phase transfer catalysts (the complex between 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride (AEM) and K2{W(O)(O2)2 (H2O)}2 (W2)) as shell, were respectively prepared. The prepared microreactors were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectrophotometer (EDX). The results indicated that the P(AM-co-MAA)/AEM/W2 microreactor with porous core has the turtle shell-like surface but that with imperforate core has smooth surface. The following results regarding the oxidation of dibenzothiophene (DBT) catalyzed by the two kinds of microreactors were obtained. Although amount of phase transfer catalysts loaded in the microreactors with the turtle shell-like surface is obviously higher than that of the microreactors with smooth surface, the catalytic efficiency of the microreactors with the turtle shell-like surface is obviously lower than that of the microreactors with smooth surface. The results imply that the effect of the distribution of phase transfer catalysts in the core–shell microreactors on the catalytic efficiency is more remarkable than that of the loaded amount of catalysts.
      Graphical abstract image

      PubDate: 2014-10-11T09:28:02Z
       
  • Aldehyde-functionalized mesostructured cellular foams prepared by
           copolymerization method for immobilization of penicillin G acylase
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Zhenyuan Gao , Wangcheng Zhan , Yunsong Wang , Yun Guo , Li Wang , Yanglong Guo , Guanzhong Lu
      Aldehyde-functionalized mesostructured cellular foams (A-MCFs) were successfully prepared by copolymerization of vinyl groups on the surface of vinyl-functionalized mesostructured cellular foams (V-MCFs) with methacrolein, and used for covalent immobilization of penicillin G acylase (PGA). Effects of functionalization with the organo-functional groups on the physicochemical properties of V-MCFs and A-MCFs, and the enzymatic activity and the operational stability of the immobilized PGA were investigated. A-MCFs-15% sample retains the characteristic ultra-large and continuous 3D mesoporous structure of MCFs with high surface area and large pore volume, which is beneficial for immobilization of PGA and diffusion of substrates and products, and thus results in high enzymatic activity of the immobilized PGA. PGA is immobilized covalently on A-MCFs sample via the reaction to produce Schiff’s base between the free amino groups of lysine residues of PGA and the aldehyde groups on the surface of A-MCFs, which greatly increases the operational stability of the immobilized PGA. PGA/A-MCFs-15% sample shows the initial enzymatic activity of 9531Ug−1 and retains 87% of its initial activity after recycled for ten times.
      Graphical abstract image

      PubDate: 2014-10-06T09:18:04Z
       
  • Incorporation of a dioxomolybdenum(VI) complex in a ZrIV-based
           Metal–Organic Framework and its application in catalytic olefin
           epoxidation
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Patrícia Neves , Ana C. Gomes , Tatiana R. Amarante , Filipe A. Almeida Paz , Martyn Pillinger , Isabel S. Gonçalves , Anabela A. Valente
      The complex [MoO2Cl2(bpydc)] (1) (H2bpydc=2,2′-bipyridine-5,5′-dicarboxylic acid) has been incorporated into a ZrIV-based Metal–Organic Framework (UiO-67) by partial replacement of 4,4′-biphenyldicarboxylic acid (H2bpdc) in the solvothermal synthesis by the complex [MoO2Cl2(H2bpydc)]. The resultant material, designated as UiO-67-MoO2Cl2(bpydc) (3), was isotypical with the parent UiO-67 framework as shown by powder X-ray diffraction (PXRD). MOF 3 was also characterised by elemental and thermogravimetric analyses, FT-IR spectroscopy and 13C{1H} MAS NMR, N2 adsorption, and scanning electron microscopy. MOF 3 catalyses the epoxidation of cis-cyclooctene (Cy8) and limonene (Lim) with tert-butylhydroperoxide as oxidant. When using α,α,α-trifluorotoluene as cosolvent at 75°C, very good epoxide selectivity was observed: 100% for Cy8 at 97% conversion, and 90% for Lim at 67% conversion. The catalyst was recovered, characterised, and used in consecutive batch runs. Drops in catalytic activity between runs were attributed to catalyst deactivation (caused by structural breakdown) rather than molybdenum leaching. Stability tests showed that protic media (due to the solvent and/or oxidant) and higher reaction temperatures (55–75°C) prompted the loss of crystallinity and structural degradation. The related MOF UiO-67-bpdc (2) is more stable than 3. The reduced stability of 3 may be related to the incorporation of the bpydc2− organic linker in the framework, as well the existence of a high number of missing-linker defects.
      Graphical abstract image

      PubDate: 2014-10-06T09:18:04Z
       
  • Selective catalytic oxidations of cyclohexene, thioether and geraniol with
           hydrogen peroxide. Sensitivity to the structure of mesoporous
           niobosilicates
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Agnieszka Feliczak-Guzik , Agata Wawrzyńczak , Izabela Nowak
      Catalytic properties of niobosilicates were tested in the oxidation reactions with aqueous H2O2 using cyclohexene, methyl phenyl sulphide and geraniol as model substrates. The catalytic performance of niobosilicates was found sensitive to the type of matrix, niobium source and location of niobium. Structural and textural parameters of the materials synthesized and the location of niobium were monitored during the catalytic reactions. Different catalytic activities of the catalysts prepared with different niobium precursors were related to different location of niobium in the matrix. Highly ordered, 3D caged cubic mesoporous silicates containing niobium, NbFDU-1, and 2D hexagonal mesoporous niobosilicates, NbSBA-15, showed good activities and selectivities.
      Graphical abstract image

      PubDate: 2014-10-06T09:18:04Z
       
  • Dispersible mesoporous carbon nanospheres as active electrode materials
           for biomolecular sensing
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Shenghai Zhou , Jin Li , Feng Zhang , Tianyi Zhang , Hao Huang , Wenbo Song
      Mesoporous carbon electrode materials have attracted attention in analytical chemistry and materials science, particularly in the electrochemical determination of biomolecules, because of their open-pore structure, large surface area, and high electrochemical activity. In this study, novel mesoporous carbon nanospheres (MCNSs) with open-pore structure, which is beneficial in preparing dispersible phases of powders for sensor fabrication, were designed and synthesized using a facile soft template approach. The accessibility of the MCNS-based active electrode material was demonstrated by simultaneous determination of dopamine, ascorbic acid, and uric acid at physiological pH. The dispersibility of MCNS was manifested by the improved stability and reproducibility of the fabricated electrochemical sensor. Meanwhile, another two similar nanospheres, namely, carbon nanospheres without open-pore structure and electrochemically inert mesoporous silica nanospheres, were also fabricated to determine the origin of the catalytic activity of the MCNSs. The high activity of the MCNS-based electrode materials can be attributed to their nanoporous structure and conductive carbon skeleton that contains high degree of defects. In addition, highly open nanopores allowed easy access of the targets to the defective sites on the nanopore walls, thereby enhancing catalytic activity and reducing response time.
      Graphical abstract image

      PubDate: 2014-10-06T09:18:04Z
       
  • High-yield selective conversion of carbohydrates to methyl levulinate
           using mesoporous sulfated titania-based catalysts
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Eric C. Njagi , Homer C. Genuino , Chung-Hao Kuo , Saminda Dharmarathna , Anton Gudz , Steven L. Suib
      Mesoporous sulfated-metal oxides and mixed-metal oxides prepared by a facile coprecipitation method employing titanium oxysulfate–sulfuric acid complex as a precursor of both titanium and sulfate are highly active and selective for direct methanolysis of carbohydrates to methyl levulinate. The most active sulfated TiO2–ZrO2 catalyst selectively converted fructose to methyl levulinate with a remarkably high yield (71%) after 1h at 200°C. Significant amounts of methyl levulinate were also obtained from sucrose (54%) and glucose (23%) after 1h at 200°C. The used catalyst was easily recovered and recycled without any loss of selectivity although activity decreased due to humin deposition on the surface. The spent catalysts were easily rejuvenated through calcination in air. The formation of ethers during dehydration was negligible suggesting that methanol can be recycled after distillation.
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      PubDate: 2014-10-06T09:18:04Z
       
  • Fabrication and electrochemical performance of nanoporous carbon derived
           from silicon oxycarbide
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Liqun Duan , Qingsong Ma , Lin Mei , Zhaohui Chen
      Microporous and mesoporous silicon oxycarbide derived carbons (SiOC-DCs) were obtained by chlorination with post treatment in ammonia (NH3) using a commercially available polymethyl(phenyl)siloxane resin. In this paper, attentions were focused on the structural evolution and electrochemical performance of SiOC-DCs as a function of pyrolysis temperature. Results showed that the geometry and macrostructure of SiOC-DCs, as well as the carbon ribbons were finely inherited from SiOC. The SiOC-DCs porosity and crystallinity depends mainly on the pyrolysis temperature. Post treatment by NH3 could further increase the sample porosity, and had little affection on the carbon crystallinity. The final SiOC-DCs samples exhibit excellent electrochemical performance as electrodes for supercapacitors, with a relatively high specific capacitance value up to 148.7Fg−1 and good capacitance retention ratio up to 94.3% after 2000 charge–discharge cycles at a current density of 1Ag−1 with KOH aqueous solutions as electrolyte. Increasing pyrolysis temperature would lead to a continual decline of specific capacitance.
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      PubDate: 2014-10-06T09:18:04Z
       
  • Silica and alumina based functional materials: Substructures, adsorption
           and gas chromatographic properties
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): V.I. Zheivot , E.V. Parkhomchuk , K.A. Sashkina , E.A. Melgunova , V.I. Zaikovskii , E.M. Moroz
      Modification of nano- and adsorption textures of alumina and silica as well as study of their chemical surface properties have been made. The use of specific templates as structure directing agents allowed varying their textural characteristics and obtaining macroporous and mesoporous functional materials with preferred influence of the substructures on the chromatographic properties of the materials. As packings of chromatographic columns structured materials gave an opportunity to carry out gas chromatographic analysis of mixtures faster than their unstructured analogs. In some cases, the efficiency of columns packed by such materials was just over than those packed by nontemplated counterparts. Modification of silica and alumina by carbonization allowed varying the chemical nature of initial surface and expanding the number of functional materials based on them. It was shown that adsorption potential of dispersion (non-specific) interaction of n-paraffins with carbonized silica and alumina was much higher compared to that of the noncarbonized materials. Some examples of successful application of the studied materials in practical gas chromatography are presented.
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      PubDate: 2014-10-06T09:18:04Z
       
  • Pore-size tuning and optical performances of nanoporous gold films
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): A.Y. Chen , S.S. Shi , Y.D. Qiu , X.F. Xie , H.H. Ruan , J.F. Gu , D. Pan
      Through pulse electrochemical dealloying (PED) and chemical dealloying (CD), a variety of nanoporous gold (NPG) films of 100nm thickness with a wide range of pore size (4–140nm) were prepared. The coarsening mechanism of pore and the effect of residual Ag on optical performances were investigated. The pore size was tuned by controlling the dissolution rate of active Ag atoms and surface diffusion rate of noble Au atoms along the alloy/solution interfaces. The maximum pore size of 140nm was obtained by surfactant-assisted chemical dealloying (SA-CD) and the minimum pore size of 4nm was achieved by PED. It is found that the surface diffusivity of gold in PED is about 0.4–2×10−20 m2 s−1, four orders of magnitude smaller than that in SA-CD (2.4×10−16 m2 s−1). Finally, optical performances of the NPG films were investigated by UV–vis and surface-enhanced Raman scattering (SERS) spectra. The results reveal that the NPG film with a pore size of 8nm fabricated by PED exhibits higher surface-plasmon absorption and the strongest SERS effect.
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      PubDate: 2014-10-06T09:18:04Z
       
  • Paving the way for surface modification in one-dimensional channels of
           mesoporous materials via plasma treatment
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Jie Gao , Xiang Zhu , Zijun Bian , Tian Jin , Jun Hu , Honglai Liu
      Plasma technology, an efficient and important approach for the surface modification, has been widely adopted for the treatment on the exposed surface of planar substrates. In this work, plasma treatment was demonstrated to be an effective way for the internal surface modification in one-dimensional channels of mesoporous SBA-15 particles, which is not a general planar substrate. Upon the plasma treatment in O2 atmosphere, the silanol groups on the surface of channels were intensively activated, as a result, large amounts of amine groups (2.56mmol (APTS)/g(sample)) can be effectively grafted within a very short time (2h). The highly dispersed amine groups inside the channels can be facilely revealed by the location of in-situ coordinated Ag nanoparticles. Moreover, the amine-modified SBA-15 via the plasma treatment exhibited a better CO2 adsorption capacity (1.26mmol/g) comparing with the traditional amine-modified SBA-15. Thus, our new approach may pave the way towards the rational modification and effective activation for porous materials, which would be meaningful for functionalization applications.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Structural stability of metal organic frameworks in aqueous media –
           Controlling factors and methods to improve hydrostability and hydrothermal
           cyclic stability
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Najam ul Qadir , Syed A.M. Said , Haitham M. Bahaidarah
      Metal organic frameworks (MOFs) have recently emerged as a center of attention among the class of more traditional porous materials including zeolites, activated carbons, and silica gels, due to their significantly larger pore volumes and tunability of pore geometry. A large amount of literature exists incorporating the gas adsorption and separation characteristics of MOFs; however, only a limited portion has been dedicated to the water adsorption properties of these novel materials. Water adsorption capacities of MOFs are known to substantially exceed those of traditional porous materials, due to which they are continuously gaining increasing attention for potential applications in water desalination and purification, dehumidification, and adsorption cooling technologies. However, a vast majority of these materials is characterized by structural degradation on either immediate or prolonged exposure to moist environments, resulting in partial or complete deterioration of water adsorption characteristics of the framework. This article reviews the various structural parameters which control the dimensional stability of MOFs in aqueous media, as well as different strategies which have been reported in literature for improving the hydrothermal resistance of these materials for potential applications in the industrial sector.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Impact of acids on the structure and composition of Linde Type A zeolites
           for use in reverse osmosis membranes for recovery of urine-containing
           wastewaters
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Heather L. Jamieson , Huidan Yin , Aaron Waller , Afsaneh Khosravi , Mary Laura Lind
      On the International Space Station (ISS) there are low pH, urine containing wastewaters that need to be recycled. We evaluated the effects of synthetic ISS wastewater on Linde Type A (LTA) zeolites to assess their applicability in membrane separations to produce potable water. Specifically, we studied the impact of the four acid-producing components found in the wastewater: chromium(VI) oxide, potassium phosphate monobasic, sodium phosphate monobasic dihydrate and sulfuric acid. We characterized effects of the acids on crystal structure, bonding, surface morphology and solid phase composition of the LTA zeolites. After 24h of exposure to synthetic wastewater brine (pH 1.94), the zeolites sustained some damage with extensive structural degradation occurring after 128h. The crystal structure of the LTA particles completely degraded in all acid-type solutions with a pH below 1 and in phosphate solutions with a pH below 5. The structural degradation resulted from the removal of aluminum from the zeolite framework. Additionally, we observed that phosphate caused changes in bonding of the zeolite, through removal of silicon from the framework and formation of aluminum phosphate precipitates. Ultimately, we found that the presence of acidic anions (specifically dihydrogen phosphate anions that catalyzed aluminum and silicon removal), rather than pH, was the most significant factor causing degradation of LTA in dihydrogen phosphate-containing solutions. Our results indicate that Linde Type A zeolites are inappropriate for use with low-pH, dihydrogen phosphate containing solutions.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Mesoporous titania with anatase walls by flash induction calcination
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Karine Assaker , Taissire Benamor , Laure Michelin , Bénédicte Lebeau , Claire Marichal , Marie-José Stébé , Jean-Luc Blin
      Induction heating has been used to thermally treat mesostructured TiO2 with hexagonal 2D structure prepared by a combined Liquid Crystalline Template (LCT) and Evaporation Induced Self-Assembly (EISA) synthesis method. Induction treatment induces the decomposition of the structuring agent P123 and the formation of anatase. Highly ordered mesoporous titania with a semi crystalline framework can be obtained very fast, i.e. 5min at 460°C or 15min at 300°C. The recovered materials have similar structural, textural properties and photoactivity towards the decomposition of methyl orange than the mesostructured TiO2 obtained after ethanol extraction followed by a calcination at 400°C in a conventional furnace.
      Graphical abstract image Highlights

      PubDate: 2014-10-01T09:14:39Z
       
  • Size effects of extraframework monovalent cations on the thermal stability
           and nitrogen adsorption of LSX zeolite
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Minghui Fan , Jihong Sun , Shiyang Bai , Hamida Panezai
      The Li-LSX zeolite was synthesized via ion exchange method with Na-LSX zeolite as a starting material, and its structural properties were characterized using FT-IR, SEM and TG-DSC techniques. The results showed that the water adsorption capacity of Li-LSX was enhanced but its thermal stability was decreased compared with that of Na-LSX. Meanwhile, combined with in situ HTXRD patterns, the parallel exothermal DSC profiles demonstrated that cationic radius and adsorbed water in FAU framework had remarkable influence on the thermal stability of Li-LSX and Na-LSX. In addition, the amount of N2 adsorbed on Li-LSX at room temperature (298K) was around 19.76g/cm3, which was higher than that of Na-LSX (5.42g/cm3). Whereas, N2 adsorption–desorption isotherm of Li-LSX at 77K showed the BET surface area (778.0m2/g) and relevant pore volume (0.40cm3/g) were higher than those of Na-LSX (622.5m2/g and 0.33cm3/g), respectively. These results suggested that the N2 adsorption capacities of LSX zeolites at 77K could be determined mainly according to their porosity; while, at 298K, the adsorption capacities depended on both the N2–cation interaction and their porosity. Therefore, it was concluded that the charge density and cationic radius (Na+ and Li+) had a remarkable influence on their adsorption performance, structural parameters (textural parameters) and their stability.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Relationships between the water content of zeolites and their cation
           population
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Serena Esposito , Antonello Marocco , Gianfranco Dell’Agli , Bruno De Gennaro , Michele Pansini
      The weight percent water content of various cation-exchanged forms of zeolites X and Y, two samples of natural clinoptilolite, and a synthetic analcime were studied. A simple linear relation was established between the weight percent water content of various cation-exchanged zeolite samples and the quantity V eq cat which is the volume of a single hypothetical equivalent cation, representing the cation population of a zeolite. This goal was fulfilled by setting up a simple model of the zeolite in which the volume of its cavities and channels is occupied by water molecules and by the exchangeable cations. The proposed model indicates the presence of void volumes (the portion of the cavities and channels occupied neither by cations nor water molecules) and allows its evaluation. The linear relation found in this work may be used to estimate the water content of various cation exchanged forms of zeolites.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Applications of TiO2 nanotube arrays in environmental and energy fields: A
           review
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Qingxiang Zhou , Zhi Fang , Jing Li , Mengyun Wang
      TiO2 nanotube arrays, novel TiO2-based nanomaterials with unique chemical and physical properties, have been demonstrated to serve as multifunctional materials which show great promise in addressing many challenges in both environmental and energy technology fields. They have exhibited extraordinary catalytic abilities in several cases: in the degradation of environmental inorganic and organic pollutants to less toxic compounds, water splitting, and in the reduction of atmospheric CO2 levels by incorporation of CO2 into hydrocarbons, among others. Moreover, the wide absorption spectrum characteristics and distinct electrochemical properties of modified TiO2 nanotube arrays make them excellent candidates for use in solar cells and sensitive sensors for trace compounds, etc. This review focuses on the recent applications of TiO2 nanotube arrays in removal of pollutants, environmental analytical chemistry, water splitting, solar cells and CO2 conversion.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Magnetic modification of acid-activated kaolin: Synthesis,
           characterization, and adsorptive properties
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Z. Gao , X. Li , H. Wu , S. Zhao , W. Deligeer , S. Asuha
      Maghemite (γ-Fe2O3) nanoparticles were synthesized onto the surface of acid-activated kaolin (AAK), prepared by calcination and acid activation of a coal bearing kaolin, by immobilizing an Fe–urea complex ([Fe(NH2CONH2)6](NO3)3) and subsequent calcination. The obtained samples were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), vibrating sample magnetic measurements, and transmission electron microscopy (TEM). The results confirm the formation of ferromagnetic γ-Fe2O3 nanoparticles, approximately 18nm in size, onto the AAK surface. The obtained γ-Fe2O3/AAK nanocomposite has a high Brunauer–Emmett–Teller (BET) surface area of 99.4m2/g and possesses ferromagnetic characteristics with a maximum magnetization of 26.5emu/g. The adsorption ability of γ-Fe2O3/AAK nanocomposite was investigated using methylene blue (MB) as a typical pollutant. Owing to its high surface area, the γ-Fe2O3/AAK nanocomposite showed higher removal efficiency for MB than for parent kaolin, with a maximum adsorption capacity of 50.2mg/g. The adsorption kinetics of MB fit well with the pseudo-second-order kinetic model, and the equilibrium data can be well described by the Langmuir adsorption model.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Enhancement of hydrogen storage capacity and hydrostability of
           metal–organic frameworks (MOFs) with surface-loaded platinum
           nanoparticles and carbon black
    • Abstract: Publication date: 15 January 2015
      Source:Microporous and Mesoporous Materials, Volume 202
      Author(s): Jihoon Kim , Shinyoung Yeo , Jae-Deok Jeon , Seung-Yeop Kwak
      Metal–organic frameworks (MOFs) have generated considerable interest as a potential candidate for hydrogen storage, owing to their extremely high surface-to-volume ratio and low density. However, practical applications have been limited because of low hydrogen storage capacity at room temperature, and of moisture sensitivity of MOFs. To improve hydrogen storage capacity at room temperature and hydrostability under ambient conditions, platinum (Pt) nanoparticles were introduced on the outer surface of MOF-5, Zn4O(1,4-benzenedicarboxylate)3 that was then coated with hydrophobic microporous carbon black (CB) to generate a CB/Pt/MOF-5 composite. To study the chemical composition, morphology, crystallinity, and properties of the synthesized material, various techniques were employed including wide-angle X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma emission spectrometry, high-resolution transmission electron microscopy, and N2 adsorption–desorption analysis. The characterization analyses confirmed the formation of a novel composite designated as CB/Pt/MOF-5 with a highly crystalline structure, and large specific surface area and pore volume. The hydrogen storage capacity (0.62wt.%) of CB/Pt/MOF-5 was superior to that of pristine MOF-5 (0.44wt.%) by 41%; furthermore, CB/Pt/MOF-5 displayed excellent hydrostability under ambient conditions. Overall, these findings indicate that MOF-5 with improved hydrogen storage capacity and hydrostability was successfully synthesized by introducing Pt nanoparticles and a carbon black layer.
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      PubDate: 2014-10-01T09:14:39Z
       
  • A novel method for synthesis of Co–Al layered double hydroxides and
           their conversions to mesoporous CoAl2O4 nanostructures for applications in
           adsorption removal of fluoride ions
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Xin Zhao , Liangmiao Zhang , Pan Xiong , Wenjing Ma , Na Qian , Wencong Lu
      Facile micro-emulsion methods have been developed to synthesize mesoporous Co–Al hydroxide carbonates with rodlike and hexagonal sheetlike morphologies. A series of samples with different molar ratio of cobalt/aluminum were prepared to investigate the impact of cobalt content. Employing transmission electron microscopy, X-ray diffraction analysis and Fourier transformed infrared spectra, the morphology, structure and composition of the products were investigated. Characterized by gas-sorption measurements, the specific surface area of the calcined S-10 sample with the rodlike morphology was as high as 379m2/g, which provided this material porosity properties and outstanding fluoride removal efficiency as high as 95.6%. The sorptive removal capacity of fluoride from aqueous solutions by the precursors and their corresponding annealed products was investigated in a batch mode. Also, the adsorption kinetics and isotherms were discussed.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Enhanced photodegradation of pentachlorophenol in a soil washing system
           under solar irradiation with TiO2 nanorods combined with municipal sewage
           sludge
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Zeyu Zhou , Yaxin Zhang , Hongtao Wang , Tan Chen , Wenjing Lu
      A novel remediation method for soil contaminated with hydrophobic chlorinated aromatic pollutants (HCAPs) was developed using TiO2 nanorods combined with municipal sewage sludge in surfactant solution. The target contaminant washed into surfactant solution from polluted soil can be rapidly removed under natural sunlight irradiation. The photocatalyst synthesized by TiO2 combined with municipal sewage sludge by a hydrothermal process shows excellent ability in this situation. The TiO2 nanorods appear on the surface of municipal sewage sludge, which offers a new way of solving waste municipal sewage sludge disposal problem and of producing high-activity photocatalyst. The nanocomposite was characterized by SEM, X-ray diffraction, and UV–Vis DRS. Results showed that the new nanocomposite was better than the original TiO2 catalyst. Using the proposed method in this study, the target contaminant can be removed by up to 97% after 30min of irradiation in natural sunlight, whereas the surfactant loss was only 27%.
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      PubDate: 2014-10-01T09:14:39Z
       
  • The impact of electrostatics in bulk Linde Type A zeolites
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Bjørnar Jensen , Tatiana Kuznetsova , Bjørn Kvamme , Richard Olsen
      Extensive Molecular Dynamics (MD) simulations were performed to study the behavior of water and methane in Linde Type A (LTA) zeolites with sodium and potassium used as counter-ions (LTA-4A and LTA-3A zeolites). Diffusivity of water was calculated for both systems, using the Mean Square Displacement (MSD) approach to quantify the impact of different counter-ions. Water in LTA zeolite with potassium as counter-ions was found to have diffusivity an order of magnitude lower than that of water in LTA-4A zeolite. The impact of the counter-ions is further clarified by the use of heat maps detailing the spatial distribution of water. Simulations in interfacial systems containing zeolite in contact with methane showed an unusual behavior of the counter-ions, prompting a detailed study of the impact of Coulombic forces in zeolites. Thus we have calculated and visualized the electrostatic gradients and studied the sensitivity of water diffusion with respect to scaling of partial charges in the zeolite framework. It was found that the outcome was highly system dependent, with the diffusivity showing a pronounced dependence varying from being increased to reduced to only intra-cavity diffusion. We concluded that it is crucial to ensure correct termination with corresponding charge distribution in interface regions. Furthermore, if one aims to investigate the ingress of water and other components into zeolite, it will be crucially important to combine the correct termination of the zeolite framework with a scaling of partial charges in the interfacial region. In conclusion we emphasize the vital role of fitting dispersive and electrostatic force fields together against experimental results, especially in the context of MD simulations.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Pillaring of bentonite clay with Al and Co
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Francine Bertella , Sibele B.C. Pergher
      This work describes the synthesis and characterization of mixed Al/Co pillared clays. The materials were prepared using different Co concentrations: 10%, 25%, 50%, 75% and 100%. The samples were analyzed by XRD, N2 physisorption, chemical analysis (AA), 27Al NMR, FTIR and EPMA. The use of small amounts of Co (10% and 25%) resulted in the formation of pillared clays, and the material containing 25% cobalt exhibited superior characteristics compared to an Al pillared clay (basal spacing of 18Å and BET surface area higher than 300m2/g). The 27Al NMR results confirmed the formation of mixed Al/Co pillars; the ratio of the AlVI/AlIV signal intensities decreased, indicating that the AlVI content decreased while the Co content increased. Thus, the Co ions isomorphically substituted for Al in the Keggin ion structure (pillaring agent). When the Co content was 50%, 75% and 100%, pillared clays did not form. Therefore, it is possible to obtain clays with mixed Al/Co pillars for Co contents of up to 25%.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Thermal conductivity of monolithic assemblies of SBA-15 ordered mesoporous
           silica particles
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Yassine Belmoujahid , Magali Bonne , Yves Scudeller , Donald Schleich , Yves Grohens , Bénédicte Lebeau
      The thermal conductivity of ordered mesoporous silicas SBA-15 type made up of primary micron size rod-shaped particles, with different states of aggregation and processed as monoliths without any binder has been studied. In particular, the influence of the post-synthesis thermal treatment of materials on the structural and textural characteristics and on the effective thermal conductivity was investigated. Thermal conductivity results were compared with observations by electronic microscopy and to the physicochemical data (X-ray diffraction, nitrogen adsorption/desorption volumetric measurements, 29Si and 13C solid-state NMR). It was observed that the elimination of the surfactant on the one hand, and the dehydroxylation of the silica network on the other hand, are partly responsible for variations in thermal conductivity. Thermal conductivity values in the range of 32–46mWm−1 K−1 was also found dependent on the morphology of particle aggregates that strongly impacts the macroporosity. Good thermal stability of the silica mesostructures was also observed up to 900°C with low thermal conductivity of about 46mWm−1 K−1. These properties make these materials very promising for thermal insulation applications over a large temperature range (room temperature up to 900°C).
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      PubDate: 2014-10-01T09:14:39Z
       
  • Synthesis and characterization of analcime using quartz syenite powder by
           alkali-hydrothermal treatment
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Xi Ma , Jing Yang , Hongwen Ma , Changjiang Liu , Pan Zhang
      Analcime was successfully synthesized for the first time via a hydrothermal treatment of quartz syenite powder and NaOH solution. The experiments were carried out at the temperature from 240°C to 260°C for 2–8h using different concentrations of NaOH solution and mass ratio of NaOH/syenite. The as-prepared samples were characterized by X-ray fluorescence, X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The results indicate that the crystalline analcime can be prepared using natural quartz syenite as an economic raw material.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Porosity characterization of SBA-15 silicas with thermoporosimetry of
           water and n-alkanes – The effect of the probe liquid nature
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): D. Majda , W. Makowski , M. Mańko , K. Mlekodaj , A. Michalik-Zym , B.D. Napruszewska , M. Zimowska , E.M. Serwicka
      Thermoporosimetry, based on DSC measurements of melting point depression of water, n-hexane and n-heptane confined in mesopores has been used for determination of the pore size distribution, average pore diameter and pore volume of series of SBA-15 mesoporous silicas. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of n-nonane. In general, the pore sizes and pore volumes determined using water and alkanes TMP reveal the same tendency as those calculated with other methods, although the absolute values show some differences. In particular, pore diameters found from water and n-hexane TPM experiments are in most cases smaller in comparison with the results obtained from other methods. On the other hand, in the case of solids with largest pores, the pore diameters found on the basis of n-heptane TPM are significantly overestimated. The values of the pore volume corresponding to the integral intensity of the TPM PSD peaks are smaller than those calculated with other methods. The possible reasons for the observed deviations are discussed. For the first time important differences in the behavior of n-hexane and n-heptane in TPM experiments are reported and attributed to different packing of C6 and C7 alkane molecules in the solidified state due the alternations in the properties of odd and even numbered hydrocarbon chains.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Zeolite Y adsorbents with high vapor uptake capacity and robust cycling
           stability for potential applications in advanced adsorption heat pumps
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Xiansen Li , Shankar Narayanan , Vladimir K. Michaelis , Ta-Chung Ong , Eric G. Keeler , Hyunho Kim , Ian S. McKay , Robert G. Griffin , Evelyn N. Wang
      Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, 27Al/29Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick’s 2nd law and D–R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Use of HZSM-5 modified with citric acid as acid heterogeneous catalyst for
           biodiesel production via esterification of oleic acid
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Sara S. Vieira , Zuy M. Magriotis , Maria Filipa Ribeiro , Inês Graça , Auguste Fernandes , José Manuel F.M. Lopes , Sabrina M. Coelho , Nadiene Ap.V. Santos , Adelir Ap. Saczk
      In this study, the efficiency of citric acid as dealumination agent was evaluated in the case of zeolite HZSM-5 by varying the experimental conditions, namely concentration (0.5, 1.0 and 2.0molL−1) and treatment temperature (60 and 80°C). The effect of the CA treatment on structural, textural and acidity properties of the starting HZSM-5 material was monitored using XRD, N2 sorption and FTIR (pyridine and collidine) measurements. Heptane and methylcyclohexane cracking model reactions were used to evaluate the catalytic behavior of the modified materials, in terms of acid strength and active sites accessibility. The modified catalysts were tested in the esterification reaction, using oleic acid as reagent and different oleic acid/methanol molar ratios. All the results show the beneficial effect of the citric acid treatment on the physicochemical properties of the final materials, with an improvement of the external acidity, a crucial parameter for the reaction considered, i.e. the oleic acid esterification.
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      PubDate: 2014-10-01T09:14:39Z
       
  • Intracellular pH-operated mechanized mesoporous silica nanoparticles as
           potential drug carries
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Li Chen , Zhe Zhang , Xuemei Yao , Xiaofei Chen , Xuesi Chen
      A series of pH-operated mechanized mesoporous silica nanoparticles (MMSNs) were fabricated and used as drug delivery for intracellular acid-triggered release. Firstly, adamantine (AD) was anchored on the surface of mesoporous silica nanoparticles (MSNs) by a pH-sensitive intermediate linker. Then, pH-operated MMSNs were prepared by the supramolecular interaction between adamantine (AD) and β-cyclodextrin (β-CD). Doxorubicin (DOX), as a drug model, was loaded into MMSNs. The pH-dependent release behavior of loaded-DOX in vitro revealed that there was only a small amount of loaded-DOX released in PBS solution at pH 7.4, while up to about 90% of loaded-DOX could be quickly released in PBS solution at pH 5.5. Compared with pH-insensitive ones, pH-operated MMSNs displayed a faster drug release behavior and a higher cellular proliferation inhibition efficacy toward tumor cells. These features suggested that pH-operated MMSNs DOX could efficiently load and delivery DOX into tumor cells, leading to an enhanced inhibition of tumor cell proliferation. Therefore, these pH-operated MMSNs will be of advantage as promising carriers for drug acid-triggered release in cancer therapy application.
      Graphical abstract image Highlights In this article, intracellular pH-operated mechanized mesoporous silica nanoparticles (MMSNs) based on host-gust interaction between adamantine and β-cyclodextrin were fabricated and used for acid-triggered release of anticancer drug.

      PubDate: 2014-10-01T09:14:39Z
       
  • Synthesis and application of ZSM-5/SAPO-34 and SAPO-34/ZSM-5 composite
           systems for propylene yield enhancement in propane dehydrogenation process
           
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Marjan Razavian , Shohreh Fatemi
      Two types of zeolitic composite systems with binary hierarchical structures comprising ZSM-5 and SAPO-34 molecular sieves were synthesized employing different procedures. Obtained products were served as catalytic carriers for propane dehydrogenation reaction so as to promote the physicochemical properties of ZSM-5 support, enhance the propylene yield and reduce the formation of light compounds. ZSM-5/SAPO-34 was fabricated in a series hydrothermal procedure employing pre-heated ZSM-5 suspension followed by secondary growth of SAPO-34 layer whereas SAPO-34/ZSM-5 was synthesized using tetrapropylammonium bromide exchanged-SAPO-34 crystals and pre-reacted ZSM-5 slurry in a hydrothermal one-step process. The products were characterized by XRD, FESEM, EDS, FTIR, NH3-TPD, and N2 adsorption–desorption techniques to investigate the textural and structural properties of composite architectures. The catalytic performance of the bimetallic Pt-Sn-based composites were evaluated in propane dehydrogenation reaction and compared with those of physical mixture and single ZSM-5-derived catalysts. Either of composites represented improved catalytic performance due to the synergetic effect between ZSM-5 and SAPO-34, which promoted the catalytic properties of the samples. Catalytic reactivity of the composite catalysts was strongly dependent on the synthesis method and employed zeolite/zeotype ratio. Best result was acquired for Pt–Sn-based SAPO-34/ZSM-5 (Si/Al=60) brand-new efficient composite with improved stability, boosted conversion and significant selectivity towards light olefins, propylene in particular.
      Graphical abstract image Highlights

      PubDate: 2014-10-01T09:14:39Z
       
  • Adsorption of dyes in aqueous solutions by chitosan–halloysite
           nanotubes composite hydrogel beads
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Qi Peng , Mingxian Liu , Jianwen Zheng , Changren Zhou
      Composite hydrogel beads containing chitosan and halloysite nanotubes (HNTs) with a well defined structure were prepared by the dropping and pH-precipitation method. The influence of HNTs on the appearance, diameter, microstructures, and thermal stability of the chitosan beads was characterized. The composite hydrogels exhibit slightly increased diameter and improved thermal stability. A rough surface and high concentration of the nanotubes in the bead core are found in the composite beads. The hydrogel beads were employed as absorbents for removal of methylene blue and malachite green from aqueous solutions and the fundamental adsorption behavior was studied. Both Langmuir isotherm and Freundlich isotherm models can fit the isotherm absorption data well. The addition of HNTs can significantly increase the adsorption rate of chitosan beads for the two dyes. Moreover, with the increase of the amount of hydrogel beads in the dye solution, the removal ratio of dyes increases but the absorption amount per unit absorbent weight gradually reduces. The adsorption kinetics closely follows pseudo-second order model. The regeneration experimental shows that the adsorption ability of all the beads can be recovered especially for methylene blue. So the chitosan–HNTs composite hydrogels can be potentially used for the removal of dyes from wastewater.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Fabrication of palladium–titania nanofiltration membranes via a
           colloidal sol–gel process
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Yuanyuan Cai , Xianfu Chen , Yi Wang , Minghui Qiu , Yiqun Fan
      Titania nanofiltration (NF) membranes with a molecular weight cut-off (MWCO) of ∼1000Da impregnated with noble metal Pd have been fabricated via the colloidal sol–gel route. The process of calcination under air atmosphere before reduction under hydrogen atmosphere was utilized for complete removal of organics, and the as-prepared Pd-doped TiO2 materials were denoted as PdO-TiO2 and Pd-TiO2, respectively. XRD patterns and TEM images confirmed that, under the air atmosphere, the Pd doping restrained TiO2 grain growth and A→R transformation, which may be due to the substitution of Pd2+ into the TiO2 lattice, suggesting that the release of deformation energy stabilized the anatase phase. Combining N2 adsorption–desorption results, the PdO-TiO2 materials with a Pd concentration of 30dwb% and a calcination temperature of 400°C were optimized with a pore size of 1.7nm. After hydrogen reduction, the inhibitory effect of Pd doping on phase transformation was weakened, with a looser pore structure achieved for the Pd-TiO2 materials with a pore size of 2.4nm, indicating the inhibitory effect of PdO, Pd0 and Pd2+, the three chemical states of elemental Pd, on TiO2 crystal growth and A→R transformation improved in turn. Finally, the Pd-TiO2 NF membranes were fabricated with a water permeability of ∼10L/(m2 hbar), showing high ion retention rates, while the undoped TiO2 membranes exhibited much lower retention properties.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Thermally induced phase transformation of Pb-exchanged LTA and
           FAU-framework zeolite to feldspar phases
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): A.S. Radosavljevic-Mihajlovic , A.S. Kremenovic , A.M. Dosen , J.Z. Andrejic , V.T. Dondur
      Thermally induced phase transformations of Pb-exchange LTA and FAU zeolites were from ambient temperature to 1300°C. Both frameworks collapse into amorphous intermediate products after heating between 600 and 650°C. Prolonged heating of the intermediate product over 1100°C results in the formation of disordered Pb-feldsparLTA [a =8.414 (4)Å, b =13.048 (4)Å, c =7.169 (4)Å, β =115.35° (3)] and Pb-feldsparFAU [a =8.422 (4)Å, b =13.054 (4)Å, c =7.173 (4)Å, β =115.37° (3)] phases. The phase conversions within the investigated temperature range were followed by thermal (DTA, TGA, and DSC), XRPD, and Raman methods.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Controllable synthesis of hierarchical beta nanozeolites from tailorable
           seeds
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Wenjuan Sun , Li Wang , Xiangwen Zhang , Guozhu Liu
      Hierarchical beta nanozeolites were controllably synthesized by tailoring seeds (or protozeolitic units, nanocrystals) grafted with phenylaminopropyltrimethoxysilane (PHAPTMS). The investigation of beta zeolite crystallization reveals that it proceeds through condensed-step mechanism, gradually growing in size along two populations of particles and evolving in internal structure. Based on the zeolitic seeds formation process, there were two roles of organosilane: the more-like mesoporogen agent in short precrystallization time and the growth inhibitor after the formation of secondary particles with significant amounts of terminal silanol groups. It was also found that both the mesopore properties and the crystal size of the prepared hierarchical beta nanozeolites were also strongly dependent on the properties of seeds. Moreover, the mechanisms for the formation of hierarchical beta nanozeolites, including size of the nanoseeds as well as its nature on the final crystal size, pore characteristics, crystallinity, and morphology were proposed and discussed in detail.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Phase transformation and morphology control of zeolite LZ-277 with
           alkaline media in Na2O–Al2O3–SiO2–H2O system
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Bo Ren , Jihong Sun , Shiyang Bai
      Zeolite LZ-277 has been synthesized from inorganic gel system via a hydrothermal method involving structure-directing agents. The structural features and textural properties of the obtained samples were extensively characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), N2 adsorption–desorption isotherms and thermogravimetric analysis/differential thermal analysis (TGA/DTA) techniques. In an effort to obtain pure zeolite LZ-277 with desert rose-like spherical morphology, we have systematically investigated the influence of pH value of starting gel on the crystallization performance. It was found that the amorphous phase, formed under low alkalinity conditions, could be transformed to pure zeolite LZ-277 by increasing the pH value of the starting gel to 11.8. However, an additional phase of FAU-type zeolite was generated when the pH value was increased to 12.8, and the sodalite crystal structure was eventually produced when the pH value reached 13.3. In addition, in order to evaluate its potential application, the thermostability of ammonium-exchanged LZ-277 was preliminary investigated using ion exchange methods, XRD, TEM and TGA/DTA analyses.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Mapping nanocavities in plugged SBA-15 with confined silver nanostructures
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Rafael L. Oliveira , Mozaffar Shakeri , Johannes D. Meeldijk , Krijn P. de Jong , Petra E. de Jongh
      Silver nanostructures inside the pores of SBA-15 and plugged SBA-15 were synthesized and imaged, providing for the first time quantitative information about the nanocavity dimensions and plug distributions in plugged SBA-15.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • The effects of the Fenton reaction are limited by zeolites in vitro
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Julien Fromonot , Pierre Suchon , Laurie Bruzzese , Nathalie Kipson , E. Fenouillet , Bernard Mallet , Régis Guieu , Oliver Schäf
      We report the effects of zeolite pore systems in limiting the oxidation of ascorbic acid (vitamin C) in plasma using the mixing of FeCl2 and H2O2 (“Fenton solution”) as an oxidant. We tested three homemade zeolites and nineteen natural zeolites. Six polar zeolites were effective in restricting the oxidation of vitamin C and the majority of them acted by chelation of ferrous/ferric chloride. Faujasite (FAU13x) was the most active ROS scavenger. On the other hand, two natural zeolites, Goosecreekite and Stilbite (GOOnat and STInat), inhibited the oxidation of vitamin C by action on the reduction of hydrogen peroxide concentration to form H2O. Our hypothesis suggests that effective zeolites have the advantage of never being saturated in the time. Here, for the first time, we identified a substrate (zeolite) which acts directly on the two substrates (Fe2+/H2O2) to limit ROS formation.
      Graphical abstract image

      PubDate: 2014-10-01T09:14:39Z
       
  • Tuning properties of silicalite-1 for enhanced ethanol/water pervaporation
           separation in its PDMS hybrid membrane
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Naixin Wang , Jida Liu , Jie Li , Jing Gao , Shulan Ji , Jian-Rong Li
      The silicalite-1/PDMS hybrid membranes have been widely studied in alcohol perm-selective pervaporation separations. However, the poor compatibility between silicalite-1 particles and PDMS has already rebated the separation performance of these hybrid membranes. In this paper, two approaches were investigated to improve/tune the compatibility of the silicalite-1 particles and PDMS matrix. Firstly, silicalite-1 crystal particles with different sizes were synthesized. The effects of the particle size on the compatibility between silicalite-1 and PDMS were investigated. It was found that smaller silicalite-1 crystals (about 100nm) have a better compatibility with PDMS matrix, thereby an enhanced separation performance of their hybrid membranes. Subsequently, the surface of silicalite-1 particles were modified through three kinds of silane coupling agents with different functional groups, which was confirmed to be feasible in increasing the compatibility with PDMS. In ethanol/water pervaporation separation, a higher selectivity was achieved in the PDMS hybrid membrane with TMDS-modified small silicalite-1 crystals. Moreover, silicalite-1 crystals provide many separate channels, so that the separation performance of the hybrid membrane has dramatically increased.
      Graphical abstract image

      PubDate: 2014-09-25T09:06:29Z
       
  • The influence of layered double hydroxide composition on the morphology,
           porosity and capacitive properties of nitrogen-doped carbon materials
           prepared via chemical vapor deposition
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Aleksandra Pacuła , Paweł Nowak , Wacław Makowski , Robert P. Socha
      Porous N-doped carbon materials of various morphologies are prepared via chemical vapor deposition (CVD) at 700°C using acetonitrile as carbon and nitrogen source and MgAl, MgCoAl, CoAl layered double hydroxides (LDHs) as template and catalyst precursors. The physicochemical properties of the carbon materials are characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, thermogravimetric analysis, elemental analysis, nitrogen sorption and n-nonane thermodesorption, whereas their electrochemical performance is evaluated in 6M KOH by means of cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscopy. The choice of LDHs strongly affects the grain morphology and micropore/mesopore contribution in the synthesized carbon materials, which determines their capacitive performance. The application of Co-free LDHs leads to the carbon material consisting of irregular aggregates of plate-like particles highly doped with nitrogen (9.7wt%) and having high specific surface area (863m2 g−1) and high capacitance (130Fg−1). On the other hand, the use of Co-containing LDHs results in the carbon materials predominantly made of carbon nanotubes (grown on metallic Co nanoparticles) less doped with nitrogen (2.4–3.1wt%) and having lower specific surface area (193–225m2 g−1) and lower capacitance (15–30Fg−1).
      Graphical abstract image Highlights

      PubDate: 2014-09-21T08:57:11Z
       
  • N-enriched ACF from coal-based pitch blended with urea-based resin for CO2
           capture
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Noel Díez , Patricia Álvarez , Marcos Granda , Clara Blanco , Ricardo Santamaría , Rosa Menéndez
      N-enriched activated carbon fibers were successfully prepared from a coal derived pitch blended with urea–formaldehyde resin. The mixture was melt-spun, stabilized, carbonized and activated with KOH, giving rise to microporous carbon fibers with high nitrogen content (up to 2.2%). Nitrogen functional groups were mostly identified as quaternary N, and the content in this nitrogen group decreased with the degree of activation. N-enriched fibers activated under mild conditions (KOH/fiber=5/1) showed the highest CO2 uptake (3.4mmol CO2 g−1 at 25°C and 1atm). Due to their high alkalinity, the N-enriched fibers showed high CO2 adsorption rates and good selectivities for CO2/N2 and CO2/CH4 separation. After saturation with CO2, the fibers could be easily regenerated and maintained their performance over several adsorption–desorption cycles.
      Graphical abstract image

      PubDate: 2014-09-21T08:57:11Z
       
  • Effects of adding alcohols on ZSM-12 synthesis
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Sinthuran Jegatheeswaran , Chin-Min Cheng , Chil-Hung Cheng
      This work systematically studies on adding alcohols to alter the crystal growth behavior of ZSM-12, using 1-propanol (1P), 2-propanol (2P), ethylene glycol (EG), 1,3-propanediol (PD), 1,6-hexanediol (HD), diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TTEG) as co-solvents. The effects of co-solvent content, temperature, and excess mineralizer content were studied as well. Except 2P, all other co-solvents are observed to tune the crystal morphology into a discrete round-shape. Except DEG and TTEG, all other co-solvents promote the crystallization rate of MTW phase, verified by larger zeolite crystal size in SEM images. The observation is corroborated with the formation of cristobalite, possibly via Ostwald ripening mechanism. The finding enlightens us using a lower synthesis temperature to attain high purity MTW phase, with an adequate amount of co-solvents. It is noteworthy that using HD as co-solvent facilitate the anisotropic growth of MTW crystals along the b-axis (2θ of 8.5°), possibly due to the effect of co-solvent’s hydrophobicity as well as the backbone length. The blue shift of symmetric and asymmetric Si-O vibration modes in FTIR spectra implies that TEG and HD are incorporated within the ZSM-12 pore structure. This work provides potential synthetic route to form anisotropic ZSM-12 membranes with preferred orientation.
      Graphical abstract image

      PubDate: 2014-09-21T08:57:11Z
       
  • Acid properties and catalysis of USY zeolite with different
           extra-framework aluminum concentration
    • Abstract: Publication date: 1 January 2015
      Source:Microporous and Mesoporous Materials, Volume 201
      Author(s): Xin Pu , Nai-wang Liu , Li Shi
      USY zeolite was treated by the citric acid. The properties and catalysis of the USY zeolite were studied. The X-ray diffraction has been used to identify and quantify extra framework aluminum (EFAL) in USY zeolite by EFAL extraction using citric acid. The acid character changed depending on the EFAL concentration. The Lewis acid sites can be obtained from the Si/Al ratio. The removing of trace olefins was carried out over kinds USY zeolites with different amount of EFAL. The catalytic performance was correlated with the Lewis acid sites of USY.
      Graphical abstract image

      PubDate: 2014-09-21T08:57:11Z
       
 
 
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