Organized mesoporous silico-nickelates (OMSiNi) and silico-lanthano-nickelates (OMSiLaNi): Crystallogenesis vs. morphogenesis and microporosity vs. pore anisotropy (Journal article)

Katsoulidis, A. P./ Tsaousi, E. T./ Armatas, G. S./ Petrakis, D. E./ Pomonis, P. J.

In this work organized mesoporous silico-nickelates (OMSiNi) and silico-lanthano-nickelates (OMSiLaNi) have been studied. The synthesis took place in one step using of poly-acrylic acid (Pac), complexed with cetyl-trimethyl-ammonium-bromide (C(16)TAB) towards a mesostructured flexible backbone on which hydrolysis of tetra-etllyl-ortho-silicate (TEOS) and Ni(NO(3))(2), or Ni(NO(3))(2) + La(NO(3))(3), takes place at increasing pH values. The loading of nickel up to 10%, and nickel plus lanthanum up to 5% each, increases with the pH values (=5.5, 7.5, 9.5) where the materials were isolated and the same effect has the increase of the temperature of the preparation bath from RT to 323 K. The surface area of the OMSiNi and OMSiLaNi solids, containing the lower amounts of metals, was determined in the range similar to 1100 and similar to 970 m(2)/g, respectively, and drops as the Ni and/or the Ni + La loading increases. The OMSiNi materials exhibits organized mesoporosity of MCM-41 type in nanometer scale (XRD) and remarkable morphologenesis of the Ni-doped silicate mass in micrometer scale (SEM). The introduction of La in the group OMSiLaNi results in gradual deterioration of organized porosity and destruction of morphogenesis. Both OMSiNi and OMSiLaNi solids contain NiO crystallites of 3-6 nm size (XRD) while the samples with high La content prepared at 323 K show extensive crystallogenesis of perfect NiO crystals of micrometer size (SEM). The pore anisotropy b was determined in the range 7 < b < 56,000 and is lower in the samples prepared at higher temperature and containing higher amounts of metal(s). The % microporosity of the solids is related to the log b by a relationship log b = log b(0) - k(% micro) where k is a parameter related inversely to the width of the micropore range of distribution. An explanation of this is proposed based on the assumption that the introduction of micropores, in conjunction with the width of their distribution, result in numerous interruptions of mesopore channels and as a result b decreases exponentially. (C) 2009 Elsevier Inc. All rights reserved.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: organized mesoporous silico-nickelates,organized mesoporous silico-lanthano-nickelates,nickel oxide,lanthanum oxide,crystal growth,self-assembly,microporosity,pore anisotropy,electron-spin-resonance,molecular-sieves,catalytic-activity,containing mcm-41,carbon-dioxide,ethylene dimerization,gas-chromatography,supported nickel,bet equation,hydrogenation
URI: https://olympias.lib.uoi.gr/jspui/handle/123456789/8707
ISSN: 1387-1811
Link: <Go to ISI>://000266061500026
http://ac.els-cdn.com/S1387181109001206/1-s2.0-S1387181109001206-main.pdf?_tid=bf939f1f5117acb46ceb47fefcef5b6e&acdnat=1333035546_f96aa5f69aaf6b381b0d2c5069eaa4b6
Publisher: Elsevier
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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