Porous ceramics of sulfated zirconia prepared by sol-gel process associated to liquid crystals as pore template

Reference	Presenter	Authors (Institution)	Abstract
17-030	Marinalva Aparecida Alves-Rosa	Alves-Rosa, M.A.(Instituto de Química/UNESP); Moris, C.H.(nstituto de Química/UNESP); Freitas, F.G.(Universidade Estadual de Santa Cruz); Santilli, C.V.(Instituto de Química/UNESP); Pulcinelli, S.H.(Instituto de Química/UNESP);	Catalysts of sulfated zirconia have been applied in several catalytic reactions that involve acid sites and need enhanced surface and porous characteristics. The catalytic performance of the porous ceramic catalysts is greatly dependent on the oxide synthesis and the processing method used to introduce porosity. Liquid Crystal Templates (LCT) are widely used to produce nanostructured materials with controlled porosity. In this work porous sulfated zirconia were prepared by using the sol-gel process associated to LCT, and the ${\mathrm{Zr}}^{4+}:{\mathrm{SO}}_4^{2-}$molar ratio evaluated from the LCT gel to the final ceramic powders. Polarized Light Microscopy and Small Angle X-Ray Scattering (SAXS) analysis of the 8 days aged LCT wet gel revealed the hexagonal as the prevalent mesophase. The thermal treatment of the LCT wet gel resulted in sulfated ${\mathrm{ZrO}}_2$ ceramic powders, in which Infrared (FTIR) spectra exhibited bands around 1050-1207 ${\mathrm{cm}}^{-1}$ assigned to links of  ${\mathrm{SO}}_4^{2-}$groups and ${\mathrm{ZrO}}_2$. X-Ray Powder Diffraction (XRPD) patterns showed a mixture of monoclinic and tetragonal phase of zirconia in which the tetragonal phase rises and the crystallite sizes decrease in function of sulfate amount. The lattice fringe distances observed by Selected-Area Electron Diffraction patterns (SAED) and high resolution TEM confirmed the mixture of tetragonal (2.9 Å) and monoclinic (4.9 Å) crystalline phases corresponding to (101) and (100) atomic plane, respectively. The LCT generated higher pores size diameter in the sample without sulfate (5.7 nm) decreasing as the sulfate content increases (4 – 3 nm) with surface areas up to 146 ${\mathrm{m}}^2/\mathrm{g}$. The scanning and transmission electronic micrographs (SEM and TEM) elucidated the pores walls as platelets of irregular format and the presence of mesopores, respectively. The porous structure combined to the presence of sulfate ions in the zirconia surface allows the application of the materials as heterogeneous catalysts.
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