Xianji Guo

Nanjing University, Nanjing, Jiangsu Sheng, China

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Publications (5)8.79 Total impact

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    ABSTRACT: This paper reports the one-step ambient-temperature synthesis of porous vanadosilicates by using tetraethyl orthosilicate as a silicon source, V2O5 powder as a vanadium source, and long-chain n-alkylamine (C8–C12) as a structure directing agent. The texture of the materials was characterized by powder X-ray diffraction, N2 adsorption–desorption isotherms, transmission electron microscopy, and thermogravimetric and differential thermal analysis. The pore size of the vanadosilicates depended largely upon the chain length of n-alkylamine. The n-alkylamine with longer carbon chain was advantageous for the formation of the larger pores. The Si/V ratio was another key factor affecting pore size of the vanadosilicates. When n-dodecylamine was employed as a structure directing agent, only mesopore structure vanadosilicates were obtained. However, when n-decylamine was used, the pore diameter of the vanadosilicates underwent a change from mesoporous scale to super-microporous scale through changing the Si/V molar ratio. The vanadosilicates exhibit a large BET specific surface area and a good thermal stability. The Si/V molar ratios of both mesoporous and super-microporous vanadosilicates with the relatively uniform pore channels could be reached 10.0 or even below. The vanadosilicates with a Si/V ratio in the range of 8.5–12 synthesized by using either n-dodecylamine or n-decylamine have a high thermal stability beyond 823 K. The nature of vanadyl species in the vanadosilicates was investigated with the use of several characterization techniques. It was determined by Raman, H2-TPR and ESR that both VVOx and VIVOx species were coexisted in the calcined vanadosilicates. The VVOx species occurred mainly in a form of monomeric tetrahedral vanadyl species on the pore wall, having one VO bond and three bridging VOSi bonds linked with the framework. The V4+ centers were in an isolated octahedrally-coordinated VIVOx mode. It was interesting to find that only a small part of VIVOx species existed in the as-synthesized vanadosilicates, while a large part of VIVOx species were formed upon calcination in air.
    Microporous and Mesoporous Materials 01/2007; 106:246-255. · 3.37 Impact Factor
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    ABSTRACT: The first chromia-pillared layered lanthanum niobic acid was prepared by an ion-exchange route, in which n-hexylamine-pre-expanded lanthanum niobate reacted with chromium(III) acetate [Cr(OAc)3] aqueous solution under reflux condition, and the ion-exchanged product was calcined at 450 °C in air flow. The structure of the novel pillared material was examined by means of various analytical techniques, such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential analysis (TG/DTA), nitrogen adsorption–desorption, and transmission electron micrographs (TEM). The chromia-pillared layered lanthanum niobic acid exhibited a porous layered structure with a BET (Brunauer-Emmett-Teller) surface area of 89 m2·g−1 and an interlayer distance of 1.31 nm. The layered structure could be retained up to 550 °C.
    Solid State Ionics 01/2006; 177(15):1293-1297. · 2.05 Impact Factor
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    ABSTRACT: A novel well-ordered super-microporous layered material, silica-pillared niobic acid, was synthesized by a guest-exchange route and structurally characterized by powder X-ray diffraction (XRD), infrared absorption spectroscopy (IR), thermogravimetric and differential thermal analysis (TG/DTA), transmission electron micrographs (TEM), nitrogen adsorption method and ammonia-temperature-programmed desorption (NH3-TPD). The obtained silica-pillared layered niobic acid had a supergallery of 1.78nm, a large BET surface area of 250m2g−1, and a high thermal stability exceeding 973K.The pillared layered material was also found to be an efficient solid acid catalyst for the vapor-phase Beckmann rearrangement of cyclohexanone oxime. When 1-hexanol was fed with cyclohexanone oxime, this solid catalyst exhibited a 100% conversion of the oxime with a selectivity of ε-caprolactam beyond 85% at a reaction temperature of 613K and a WHSV of 0.17h−1 in terms of cyclohexanone oxime, and there was no significant change of the conversion and selectivity within 6h.
    Microporous and Mesoporous Materials - MICROPOROUS MESOPOROUS MAT. 01/2005; 80(1):269-274.
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    ABSTRACT: The intercalation behaviour of titanium(IV) (triethanolaminato)-isopropoxide (abbreviated as TEAIP) in a series of layered protonic metal oxides was investigated. Two novel inorganic–organic hybrid nanocomposites have been obtained.
    Inorganic Chemistry Communications 08/2004; 7(8):946–948. · 2.02 Impact Factor
  • Xianji Guo, Wenhua Hou, Qijie Yan, Yi Chen
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    ABSTRACT: This paper reviews the recent progress in the synthesis and application of pillared transition metal oxides during the last decade, mainly concerning the synthetic methods, structures, physical properties and catalytic applications of the layered transition metal oxides pillared by inorganic oxides. The factors and their affecting regularity in the process of preparation, and some important results obtained in the catalytic application studies are summarized. Finally, a prospect on the potential new directions in this research area is also presented.
    Chinese Science Bulletin 48(2):101-110. · 1.37 Impact Factor

Publication Stats

8 Citations
8.79 Total Impact Points

Institutions

  • 2004–2007
    • Nanjing University
      • Department of Chemical Engineering
      Nanjing, Jiangsu Sheng, China
  • 2006
    • Zhengzhou University
      • Department of Chemistry
      Cheng, Henan Sheng, China