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Mietek Jaroniec - One of the best experts on this subject based on the ideXlab platform.

  • studies of intrawall porosity in the hexagonally ordered mesostructures of sba 15 by small angle x ray scattering and Nitrogen Adsorption
    Applied Surface Science, 2010
    Co-Authors: Stanislaw Pikus, Mietek Jaroniec, Ewa B Celer, Leonid A Solovyov, Maciej Kozak
    Abstract:

    Abstract Ordered mesoporous silicas (OMSs) such as SBA-15 ( p 6 mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 °C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and Nitrogen Adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 °C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 °C, respectively.

  • polypyrrole based Nitrogen doped carbon replicas of sba 15 and sba 16 containing magnetic nanoparticles
    Journal of Physical Chemistry C, 2008
    Co-Authors: Pasquale F Fulvio, Mietek Jaroniec, Chengdu Liang, Sheng Dai
    Abstract:

    Polypyrrole-based ordered mesoporous carbons (OMCs) were synthesized via chemical vapor infiltration of pyrrole into pores of the SBA-15 and SBA-16 silica templates containing iron(III) chloride catalyst (FeCl3). After carbonization of polypyrrole at 800 °C and etching of the silica templates with hydrofluoric acid solution, Nitrogen-doped and graphitic OMCs with incorporated magnetic nanoparticles were obtained. These materials were analyzed by CHNS elemental analysis, thermogravimetry (TG), Nitrogen Adsorption, small and wide angle powder X-ray diffraction (XRD), Raman spectroscopy, scanning, and transmission electron microscopy (TEM). The resulting carbon replicas retained the crystallographic symmetry of the silica templates: namely, P6mm in the case of the SBA-15 template, and Im3m in the case of the SBA-16 template. The uniformity, size, and volume of ordered mesopores in the carbon replicas were affected by structural properties of the templates used as shown by analysis of Nitrogen Adsorption isot...

  • mesoporous carbons synthesized by soft templating method determination of pore size distribution from argon and Nitrogen Adsorption isotherms
    Microporous and Mesoporous Materials, 2008
    Co-Authors: J Choma, Joanna Gorka, Mietek Jaroniec
    Abstract:

    The applicability of Kruk–Jaroniec–Sayari (KJS) pore size analysis method developed for siliceous materials with cylindrical mesopores is discussed for novel channel-like mesoporous carbons obtained by soft-templating synthesis. It was shown that a simple replacement of the statistical film thickness curves (t-curves) for argon and Nitrogen on the silica surface by the corresponding t-curves on the carbon surface makes this method applicable for pore size analysis of carbons with cylindrical mesopores. A simple way to obtain t-curves for argon and Nitrogen Adsorption on a nongraphitized carbon surface is discussed.

  • ordered mesoporous silica with large cage like pores structural identification and pore connectivity design by controlling the synthesis temperature and time
    Journal of the American Chemical Society, 2003
    Co-Authors: Jivaldo Do Rosario Matos, Mietek Jaroniec, Michal Kruk, Lucildes Pita Mercuri, Lan Zhao, Tomoaki Kamiyama, Osamu Terasaki, Thomas J Pinnavaia
    Abstract:

    FDU-1 silicas with large cage-like pores (diameter about 10 nm) were synthesized under acidic conditions from tetraethyl orthosilicate in the presence of a poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer template B50−6600 (EO39BO47EO39). High-resolution transmission electron microscopy and small-angle X-ray scattering provided strong evidence that FDU-1 silica synthesized under typical conditions is a face-centered cubic Fm3m structure with 3-dimensional hexagonal intergrowth and is not a body-centered cubic Im3m structure, as originally reported. Samples synthesized in a wide range of conditions (initial temperatures from 298 to 353 K; hydrothermal treatment at 333−393 K) exhibited similar XRD patterns and their Nitrogen Adsorption isotherms indicated a good-quality cage-like pore structure. The examination of low-pressure Nitrogen Adsorption isotherms for FDU-1 samples, whose pore entrance diameters were evaluated using an independent method, allowed us to conclude that...

  • a model independent analysis of Nitrogen Adsorption isotherms on oxidized active carbons
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
    Co-Authors: Jerzy Choma, Mietek Jaroniec
    Abstract:

    Abstract A series of commercial active carbons was oxidized in the liquid-phase using various oxidizing agents such as hydrogen peroxide, perchloric acid and nitric acid. Low temperature Nitrogen Adsorption was used to monitor the changes in the surface properties and porous structure of active carbons occurring during oxidation process. A quantitative characterization of these changes was done on the basis of Adsorption Potential Distributions (APDs) obtained from Nitrogen Adsorption isotherms. The characteristic minima appearing on these distributions allowed to evaluate the specific surface area and the micropore volume, which subsequently were used to estimate the average micropore width. It was shown that the oxidation of active carbons with hydrogen peroxide, perchloric acid and nitric acid at room temperature did not cause a substantial change in the resulting APDs. This is not the case for active carbons oxidized with nitric acid at the boiling temperature. The latter oxidation caused a significant deterioration of the porous structure of active carbons in addition to the distinct changes in their surface functionality, which is evidenced by a significant difference in the structural parameters evaluated from the APDs for unmodified and strongly oxidized samples.

Michal Kruk - One of the best experts on this subject based on the ideXlab platform.

  • ordered mesoporous silica with large cage like pores structural identification and pore connectivity design by controlling the synthesis temperature and time
    Journal of the American Chemical Society, 2003
    Co-Authors: Jivaldo Do Rosario Matos, Mietek Jaroniec, Michal Kruk, Lucildes Pita Mercuri, Lan Zhao, Tomoaki Kamiyama, Osamu Terasaki, Thomas J Pinnavaia
    Abstract:

    FDU-1 silicas with large cage-like pores (diameter about 10 nm) were synthesized under acidic conditions from tetraethyl orthosilicate in the presence of a poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer template B50−6600 (EO39BO47EO39). High-resolution transmission electron microscopy and small-angle X-ray scattering provided strong evidence that FDU-1 silica synthesized under typical conditions is a face-centered cubic Fm3m structure with 3-dimensional hexagonal intergrowth and is not a body-centered cubic Im3m structure, as originally reported. Samples synthesized in a wide range of conditions (initial temperatures from 298 to 353 K; hydrothermal treatment at 333−393 K) exhibited similar XRD patterns and their Nitrogen Adsorption isotherms indicated a good-quality cage-like pore structure. The examination of low-pressure Nitrogen Adsorption isotherms for FDU-1 samples, whose pore entrance diameters were evaluated using an independent method, allowed us to conclude that...

  • determination of pore size and pore wall structure of mcm 41 by using Nitrogen Adsorption transmission electron microscopy and x ray diffraction
    Journal of Physical Chemistry B, 2000
    Co-Authors: Michal Kruk, Mietek Jaroniec, Osamu Terasaki, Yasuhiro Sakamoto, Ryong Ryoo, Chang Hyun Ko
    Abstract:

    Highly ordered MCM-41 materials were synthesized using single or mixed alkyltrimethylammonium and alkyltriethylammonium surfactants of alkyl chain lengths from 12 to 22. As determined using combined Adsorption/powder X-ray diffraction (XRD) analysis, the obtained samples exhibited pore sizes from 3.2 to 4.8 nm with about 0.3 nm increments. Nitrogen Adsorption isotherms for the samples under study exhibited remarkably sharp capillary condensation steps. The Adsorption isotherm for the highly ordered 4.8 nm MCM-41 featured a narrow hysteresis loop with parallel Adsorption and desorption branches. This behavior is probably a feature of Nitrogen Adsorption in ideal cylindrical pores of this size and is distinctly different from the previously reported behavior of MCM-41 with pore sizes in the range 4−5.5 nm, which had triangular hysteresis loops on their Nitrogen Adsorption isotherms. All MCM-41 materials had remarkably narrow pore size distributions, which showed that fine-tuning of the pore size is easily a...

  • standard Nitrogen Adsorption data for characterization of nanoporous silicas
    Langmuir, 1999
    Co-Authors: Mietek Jaroniec, Michal Kruk, James P Olivier
    Abstract:

    The Nitrogen Adsorption isotherm measured at 77 K in the relative pressure range from about 5 × 10-7 to 0.988 for a macroporous silica is reported in a tabular form. The isotherm data are in good agreement in the high-pressure range with the reference data published by Gregg and Sing and by Kiselev and Aristov and provide an extension of the latter data to the low-pressure region, for which a reliable reference isotherm was not availalable in the literature. Application of the currently reported reference Adsorption isotherm is discussed. The data can be used in comparative analysis (αs-plot or t-plot) to evaluate the external surface area, micropore volume, primary mesopore volume, and total surface area as well as to analyze surface properties of silica-based materials. The Adsorption isotherm can also be applied as a statistical film thickness curve in the calculation of the mesopore size distribution.

  • Nitrogen Adsorption study of surface properties of graphitized carbon blacks
    Langmuir, 1999
    Co-Authors: Michal Kruk, Mietek Jaroniec, William R Betz
    Abstract:

    Surface and structural properties of commercially available Carbopack graphitized carbon blacks with specific surface areas from 6 to 225 m2/g were studied using Nitrogen Adsorption in a wide range of pressures. Specific surface areas, total pore volumes, and pore size distributions were evaluated. It was observed that the carbons with lower specific surface areas exhibited a higher degree of graphite crystallinity. Low-pressure Adsorption data were carefully examined in order to obtain information about surface heterogeneity of the samples in terms of Adsorption potential distributions, high-resolution θ-plots, and Adsorption energy distributions. It was shown that the graphitized carbon blacks under study exhibited relatively high surface homogeneity, which increased with an increasing degree of graphite crystallinity. An examination of the θ-plots and Adsorption potential distributions allowed us to draw a conclusion that the average Adsorption energy decreased with a decrease in the degree of crystall...

  • tailoring surface and structural properties of mcm 41 silicas by bonding organosilanes
    Journal of Physical Chemistry B, 1998
    Co-Authors: Christopher P Jaroniec, Mietek Jaroniec, Michal Kruk, Abdelhamid Sayari
    Abstract:

    Large pore MCM-41 silica with the pore diameter of 5.0 nm was chemically modified by bonding monomeric-type ligands, such as trimethylsilyl, butyldimethylsilyl, and octyldimethylsilyl, as well as polymeric-type 3-aminopropylsilyl, (hexanoyl-3-aminopropyl)silyl, and octylsilyl ligands. The obtained materials were characterized using elemental analysis, high-resolution thermogravimetry (TGA), and Nitrogen Adsorption at 77 K in a wide range of pressures. Surface coverages of bonded ligands were between 2.5 and 3.0 μmol/m2. It was shown that pore diameters of the samples studied decreased systematically with the increase in size of ligands. The modified materials exhibited narrow and monodisperse pore size distributions, indicating that the chemical bonding procedure did not diminish the structural ordering of the MCM-41 support. TGA data showed that the surface affinity to water was strongly dependent on the structure and functionality of the bonded species. Nitrogen Adsorption data provided additional infor...

Abdelhamid Sayari - One of the best experts on this subject based on the ideXlab platform.

  • polyamidoamine dendrimers prepared inside the channels of pore expanded periodic mesoporous silica
    Advanced Functional Materials, 2005
    Co-Authors: Jan P K Reynhardt, Abdelhamid Sayari, Yong Yang, Howard Alper
    Abstract:

    Polyamidoamine dendrimers up to the fourth generation have been grown with unprecedentedly high loading within the channels of pore-expanded (10.6 nm) MCM-41 silica. In-depth characterization using Nitrogen Adsorption, solid-state NMR, FTIR, thermogravimetry, and elemental analysis showed that the dendrimers grow inside the channels with an average yield better than 99 %. The pore size and structure of the support have been found to be determining factors as to how much dendrimer growth can be achieved.

  • tailoring surface and structural properties of mcm 41 silicas by bonding organosilanes
    Journal of Physical Chemistry B, 1998
    Co-Authors: Christopher P Jaroniec, Mietek Jaroniec, Michal Kruk, Abdelhamid Sayari
    Abstract:

    Large pore MCM-41 silica with the pore diameter of 5.0 nm was chemically modified by bonding monomeric-type ligands, such as trimethylsilyl, butyldimethylsilyl, and octyldimethylsilyl, as well as polymeric-type 3-aminopropylsilyl, (hexanoyl-3-aminopropyl)silyl, and octylsilyl ligands. The obtained materials were characterized using elemental analysis, high-resolution thermogravimetry (TGA), and Nitrogen Adsorption at 77 K in a wide range of pressures. Surface coverages of bonded ligands were between 2.5 and 3.0 μmol/m2. It was shown that pore diameters of the samples studied decreased systematically with the increase in size of ligands. The modified materials exhibited narrow and monodisperse pore size distributions, indicating that the chemical bonding procedure did not diminish the structural ordering of the MCM-41 support. TGA data showed that the surface affinity to water was strongly dependent on the structure and functionality of the bonded species. Nitrogen Adsorption data provided additional infor...

  • application of large pore mcm 41 molecular sieves to improve pore size analysis using Nitrogen Adsorption measurements
    Langmuir, 1997
    Co-Authors: Kruk M And, Mietek Jaroniec, Abdelhamid Sayari
    Abstract:

    MCM-41 siliceous molecular sieves were used to test the applicability of the Kelvin equation for Nitrogen Adsorption in cylindrical pores of the size from 2 to 6.5 nm. It was shown that the Kelvin equation for the hemispherical meniscus, corrected for the statistical film thickness, is in quite good agreement with an experimental relation between the pore size and the capillary condensation pressure. The agreement can be made quantitative in the pore size range from ca. 2 to 6.5 nm, if a simple correction to the Kelvin equation is introduced. The required statistical film thickness curve (t-curve) was calculated using Nitrogen Adsorption data for large pore MCM-41 samples and the obtained results were extrapolated using an Adsorption isotherm for a macroporous silica gel. Moreover, an accurate analytical representation of the t-curve was found. Since both the corrected Kelvin equation for cylindrical pores and the t-curve have simple analytical forms, they can conveniently be used in a variety of methods ...

Frank Lipnizki - One of the best experts on this subject based on the ideXlab platform.

  • analysis of membrane fouling by brunauer emmet teller Nitrogen Adsorption desorption technique
    Scientific Reports, 2020
    Co-Authors: Tiina Virtanen, Gregor Rudolph, Anastasiia Lopatina, Basel Alrudainy, Herje Schagerlof, Liisa Puro, Mari Kallioinen, Frank Lipnizki
    Abstract:

    Membrane fouling is the major factor limiting the wider applicability of the membrane-based technologies in water treatment and in separation and purification processes of biorefineries, pulp and paper industry, food industry and other sectors. Endeavors to prevent and minimize fouling requires a deep understanding on the fouling mechanisms and their relative effects. In this study, Brunauer-Emmett-Teller (BET) Nitrogen Adsorption/desorption technique was applied to get an insight into pore-level membrane fouling phenomena occurring in ultrafiltration of wood-based streams. The fouling of commercial polysulfone and polyethersulfone membranes by black liquor, thermomechanical pulping process water and pressurized hot-water extract was investigated with BET analysis, infrared spectroscopy, contact angle analysis and pure water permeability measurements. Particular emphasis was paid to the applicability of BET for membrane fouling characterization. The formation of a fouling layer was detected as an increase in cumulative pore volumes and pore areas in the meso-pores region. Pore blocking was seen as disappearance of meso-pores and micro-pores. The results indicate that the presented approach of using BET analysis combined with IR spectroscopy can provide complementary information revealing both the structure of fouling layer and the chemical nature of foulants.

Castro R Contreras - One of the best experts on this subject based on the ideXlab platform.

  • effect of mesoporous carbon support nature and pretreatments on palladium loading dispersion and apparent catalytic activity in hydrogenation of myrcene
    Journal of Catalysis, 2019
    Co-Authors: Castro R Contreras, Boris Guicheret, Bruno F Machado, Camila Riveracarcamo, M Curiel A Alvarez, Valdez B Salas, Mirco Ruttert, Tobias Placke, Favre A Reguillon
    Abstract:

    Abstract The influence of the carbon support characteristics on Pd loading, dispersion and activity in Pd/C catalysts has been analyzed. Several carbon nanomaterials, including multi-walled CNTs, Nitrogen-doped CNTs, sulfur-doped CNTs, large- and small-diameter nanofibers, few-layer graphene, and a fibrous carbon have been produced, functionalized, defunctionalized and characterized using several techniques (e.g., Nitrogen Adsorption, Raman spectroscopy, XPS, TGA, and elemental analysis). These supports present different surface chemistry, arising from different features (defect concentration, inter-defect distances, long-range order, and orientation of the graphene layers) and specific surface areas. The most relevant parameters were obtained by characterization of the materials by Raman, XPS, Nitrogen Adsorption, and XRD. Twenty-four palladium catalysts with the same nominal loading (2%w/w) were prepared by wet impregnation using an acetone solution of Pd nitrate. These 24 catalysts were characterized by ICP, XRD, XPS and TEM. The final Pd loading varied between 1 and 2%w/w and the Pd particle size ranged from 1.5 to 3.3 nm, depending on the nature of the support. The parameters influencing both Pd loading and dispersion are discussed, and their very high activity for the myrcene complete hydrogenation are reported.

  • Effect of mesoporous carbon support nature and pretreatments on palladium loading, dispersion and apparent catalytic activity in hydrogenation of myrcene
    'Elsevier BV', 2019
    Co-Authors: Castro R Contreras, Boris Guicheret, Bruno F Machado, M Curiel A Alvarez, Valdez B Salas, Mirco Ruttert, Tobias Placke, Favre A Reguillon, C. Rivera-cárcamo, L. Vanoye
    Abstract:

    The influence of the carbon support characteristics on Pd loading, dispersion and activity in Pd/C catalysts has been analyzed. Several carbon nanomaterials, including multi-walled CNTs, Nitrogen-doped CNTs, sulfur-doped CNTs, large- and small-diameter nanofibers, few-layer graphene, and a fibrous carbon have been produced, functionalized, defunctionalized and characterized using several techniques (e.g., Nitrogen Adsorption, Raman spectroscopy, XPS, TGA, and elemental analysis). These supports present different surface chemistry, arising from different features (defect concentration, inter-defect distances, longrange order, and orientation of the graphene layers) and specific surface areas. The most relevant parameters were obtained by characterization of the materials by Raman, XPS, Nitrogen Adsorption, and XRD. Twenty-four palladium catalysts with the same nominal loading (2%w/w) were prepared by wet impregnation using an acetone solution of Pd nitrate. These 24 catalysts were characterized by ICP, XRD, XPS and TEM. The final Pd loading varied between 1 and 2%w/w and the Pd particle size ranged from 1.5 to 3.3 nm, depending on the nature of the support. The parameters influencing both Pd loading and dispersion are discussed, and their very high activity for the myrcene complete hydrogenation are reported