Article

Pore structural characteristics, size exclusion properties and column performance of two mesoporous amorphous silicas and their pseudomorphically transformed MCM-41 type derivatives.

Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Mainz, Germany.
Journal of Separation Science (Impact Factor: 2.59). 01/2008; 30(18):3089-103. DOI: 10.1002/jssc.200700227
Source: PubMed

ABSTRACT Highly ordered mesoporous silicas such as, mobile composition of matter, MCM-41, MCM-48, and the SBA-types of materials have helped to a large extent to understand the formation mechanisms of the pore structure of adsorbents and to improve the methods of pore structural characterization. It still remains an open question whether the high order, the regularity of the pore system, and the narrow pore size distribution of the materials will lead to a substantial benefit when these materials are employed in liquid phase separation processes. MCM-41 type 10 microm beads are synthesized following the route of pseudomorphic transformation of highly porous amorphous silicas. Highly porous silicas and the pseudomorphically transformed derivatives are characterized by nitrogen sorption at 77 K and by inverse size-exclusion chromatography (ISEC) employing polystyrene standards. Applying the network model developed by Grimes, we calculated the pore connectivity n(T) of the materials. The value of n(T) varies between the percolation threshold of the lattice and values of n(T) > 10, the latter being the limiting value above which the material can be considered to be almost infinitely connected such that the ISEC behavior of the material calculated with the pore network model is the same when calculated with a parallel pore model which assumes an infinite connectivity. One should expect that the pore connectivity is reflected in the column performance, when these native and unmodified materials are packed into columns and tested with low molecular weight analytes in the Normal Phase LC mode. As found in a previous study on monolithic silicas and highly porous silicas, the slope of the plate height (HETP) - linear velocity (u) curve decreased significantly with enhanced pore connectivity of the materials. First results on the pseudomorphically transformed MCM-41 type silicas and their highly porous amorphous precursors showed that (i) the transformation did not change the pore connectivity (within the limits detectable by ISEC) from the starting material to the final product and (ii) the slope of the HETP versus u curve for dibutylphtalate did not change significantly after the pseudomorphic transformation.

0 Bookmarks
 · 
68 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mesostructured cellular foam silica spheres with different textual parameters were synthesized using a triblock copolymer as a template. The effects of acid concentration and aging time on the window size and morphology were discussed. Besides, the adsorption performances of lysozyme and bovine serum albumin on the blank mesostructured cellular foam with different window size and aminopropyl-modified mesostructured cellular foams were studied. The adsorption capacity and rates were shown to be dependent on the window size and surface chemical properties of the adsorbents. In particular, the mesostructured cellular foam with window size of 15.2 nm showed fast adsorption for lysozyme with adsorption capacity of 500 mg/g in 10 min. Furthermore, it has been shown that mesostructured cellular foam spheres are potential materials in the separation of biomolecules because of their chemical tunable surface and molecular sieve properties. This article is protected by copyright. All rights reserved.
    Journal of Separation Science 06/2014; · 2.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The efficacy of nanoporous inorganic MCM-41 membrane as a new separator material for electrochemical cell has been investigated. The hexagonally ordered, narrow pore structure of MCM-41 membrane serves as ion exchange channels between the anolyte and catholyte of an electrochemical cell. Besides, it also acts as the electrolyte matrix or reservoir due to the hydrophilic nature of the as-synthesized MCM-41 and along with the high surface area and pore volume density characteristics. MCM-41 membrane has been employed as separator in zinc–air electrochemical system. MCM-41 was synthesized on the zinc substrate by dip-coating method and its thickness was ca. 5μm. The Zn/MCM-41/air cell was able to produce a maximum power density of 32mWcm−2 and possessed a volumetric energy density of 300Whl−1, which are considered comparable to the published product datasheet of commercial zinc–air button cells of equivalent size.
    Fuel and Energy Abstracts 01/2011; 367(1):152-157.
  • [Show abstract] [Hide abstract]
    ABSTRACT: New generation columns, i.e. packed with superficially porous silica particles are available as trade names with following manufacturers: Halo, Ascentis Express, Proshell 120, Kinetex, Accucore, Sunshell, and Nucleoshell. These provide ultra-fast HPLC separations for a variety of compounds with moderate sample loading capacity and low back pressure. Chemistries of these columns are C(8) , C(18) , RP-Amide, hydrophilic interaction liquid chromatography, penta fluorophenyl (PFP), F5, and RP-aqua. Normally, the silica gel particles are of 2.7 and 1.7 μm as total and inner solid core diameters, respectively, with 0.5-μm-thick of outer porous layer having 90 Å pore sizes and 150 m(2) /g surface area. This article describes these new generation columns with special emphasis on their textures and chemistries, separations, optimization, and comparison (inter and intra stationary phases). Besides, future perspectives have also been discussed.
    Journal of Separation Science 12/2012; 35(23):3235-49. · 2.59 Impact Factor

Full-text (4 Sources)

View
38 Downloads
Available from
Jun 2, 2014