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Synthesis of nano γ- AlOOH from aluminate solutions for catalytic applications

Synthesis of nano γ- AlOOH from aluminate solutions for catalytic applications. Prof. Panias Dimitrios Krestou Athina , MSc . Introduction. Bauxite. Alumina. Introduction. BAYER PROCESS. to lower the SiO 2 concentration and control the level of phosphates .

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Synthesis of nano γ- AlOOH from aluminate solutions for catalytic applications

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  1. Synthesis of nanoγ-AlOOH from aluminate solutions for catalytic applications Prof. PaniasDimitrios KrestouAthina, MSc SLM 2008, Belgrade National Technical University of Athens

  2. Introduction Bauxite Alumina SLM 2008, Belgrade National Technical University of Athens

  3. Introduction BAYER PROCESS to lower the SiO2 concentration and control the level of phosphates may contain Al(OH)3 or AlOOH for the extraction of all of the Al2O3 in bauxite Al(OH)3 Calcination above 1380K 2Al(OH)3α-Al2O3 +3H2O SLM 2008, Belgrade National Technical University of Athens

  4. Introduction (energy saving,topotactic transformation into γ-Al2O3) SLM 2008, Belgrade National Technical University of Athens

  5. Introduction SLM 2008, Belgrade National Technical University of Athens

  6. Introduction SLM 2008, Belgrade National Technical University of Athens

  7. Properties Applications Microstructure Introduction SLM 2008, Belgrade National Technical University of Athens

  8. Applications (catalysis, adsorption) Properties (high surface area, mesoporosity, proper crystallite size) Microstructure (homogeneous, defect-free) Introduction SLM 2008, Belgrade National Technical University of Athens

  9. Introduction • Applications of γ- Al2O3 • catalyst or catalyst support in heterogeneous catalysis • adsorbent in purification and bleaching processes • composite reinforcement • membrane in separation processes of industrial waste streams and food • in biomedical and chemical processes absence of defects Enhanced performance: homogeneous microstructure uniform size distribution NANO-METER or SUB-MICROMETER sized particles SLM 2008, Belgrade National Technical University of Athens

  10. Experimental Previous research in the Laboratory of Metallurgy (NTUA) Synthetic Bayer liquor (SSA) Boehmite seeds T<100oC precipitation of coarse γ-AlOOH particles by decreasing the free NaOH More information: D. Panias, A. Asimidis, I. Paspaliaris, Hydrometallurgy 15-29 (2001) 59. C.Skoufadis, D.Panias, I Papsaliaris, Hydrometallurgy 57 (2003) 68. D. Panias, Hydrometallurgy 203 (2004) 74. D. Panias, A. Krestou, Powder Technology 163-173 (2007) 175. SLM 2008, Belgrade National Technical University of Athens

  11. Experimental This study: Precipitation of pure nano-boehmite by the destabilization of SSA through neutralization at atmospheric conditions without γ-AlOOH seed addition SLM 2008, Belgrade National Technical University of Athens

  12. Experimental 0<tag<2weeks ssa, ps, pv, psd by N2 adsorption /desorption 30<T<100oC XRD calcination T addition rate Reagents Parameters Studied Characterization of precipitates Mode of mixing 5<pH<13,6 TG SEM, TEM SSA (solution A) AB BA Acid (solution B) HNO3, HCl, H2SO4, H3PO4, CH3COOH SLM 2008, Belgrade National Technical University of Athens

  13. Results-BA experiments Precipitates: well crystallised gibbsite gibbsite/bayerite mixtures gibbsite/bayerite/boehmite mixtures NO PURE γ-AlOOH with the BA experiments SLM 2008, Belgrade National Technical University of Athens

  14. Results-AB experiments PURE nano-crystallite γ-AlOOH with the AB experiments SLM 2008, Belgrade National Technical University of Athens

  15. Results-AB experiments Effect of Temperature and pH SLM 2008, Belgrade National Technical University of Athens

  16. Results-AB experiments Effect of ageing time SLM 2008, Belgrade National Technical University of Athens

  17. Results-AB experiments Effect of different acids SLM 2008, Belgrade National Technical University of Athens

  18. Results-AB experiments Effect of different acids (T90-pH7-t24h) Region Ι Region ΙΙ Region ΙΙΙ Transformation of γ-AlOOH to γ-Al2O3 Transformations Crystallites<50nm Transformation to γ-AlOOH of higher crystallinity SLM 2008, Belgrade National Technical University of Athens

  19. Results-AB experiments Effect of different acids (T90-pH7-t24h) SLM 2008, Belgrade National Technical University of Athens

  20. Results-AB experiments Effect of addition rate(T90-ph7-t0) Ab. add. 10ml/min 7ml/min 5ml/min 3ml/min 1ml/min SLM 2008, Belgrade National Technical University of Athens

  21. Conclusions Only the AB experiments resulted in γ-AlOOH precipitation : effect of Al-species • T & pH: better crystallinity in less tageing • HCl : higher specific surface area • addition rate 5ml/min: most promising for the precipitation of nanocrystalliteγ-AlOOH and calcined products for catalytic applications SLM 2008, Belgrade National Technical University of Athens

  22. Thank you ! SLM 2008, Belgrade

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