Synthesis of nano Al OOH from aluminate solutions

Synthesis of nano γ-Al. OOH from aluminate solutions for catalytic applications Prof. Panias Dimitrios Krestou Athina, MSc 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction Construction Catalysts Packaging Bauxite Medicinal Alumina Abrasives Ceramics 3/9/2021 Transportation Electrical Conductors Machinery & Equipment SLM 2008, Belgrade National Technical University of Athens

Introduction BAYER PROCESS may contain Al(OH)3 or Al. OOH to lower the Si. O 2 concentration and control the level of phosphates for the extraction of all of the Al 2 O 3 in bauxite Al(OH)3 Calcination above 1380 K 2 Al(OH)3 α-Al 2 O 3 +3 H 2 O 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction γ- Al 2 O 3 α- Al 2 O 3 Gibbsite γ-Al(OH)3 Bayerite α-Al(OH)3 Boehmite γ-Al. OOH (energy saving, topotactic transformation into γ-Al 2 O 3) 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction γ-AlΟΟΗ Nanosized High surface area Narrow distribution in mesoporous 3/9/2021 Controlled calcination SLM 2008, Belgrade γ-Al 2 O 3 with the same microtructure as boehmite precursor National Technical University of Athens

Introduction Bayer liquor (Na. Al. O 4, Na. OH, impurities) Precipitation γ-Al. OOH rather than Al(OH)3 Calcination (γ-, η-, δ-, θ-, α-Al 2 O 3) 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction Properties Applications Microstructure 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction Properties (high surface area, mesoporosity, proper crystallite size) Applications (catalysis, adsorption) Microstructure (homogeneous, defect-free) 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Introduction Applications of γ- Al 2 O 3 • 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 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Experimental Previous research in the Laboratory of Metallurgy (NTUA) Ø Synthetic Bayer liquor (SSA) Ø Boehmite seeds Ø T<100 o. C Ø precipitation of coarse γ-Al. OOH particles by decreasing the free Na. OH 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. 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Experimental This study: Precipitation of pure nano-boehmite by the destabilization of SSA through neutralization at atmospheric conditions without γ-Al. OOH seed addition 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Experimental Reagents SSA (solution A) Acid (solution B) Mode of mixing BA AB Parameters Studied 30<T<100 o. C XRD 5<p. H<13, 6 TG 0<tag<2 weeks ssa, ps, pv, psd addition rate HNO 3, HCl, H 2 SO 4, H 3 PO 4, CH 3 COOH 3/9/2021 Characterization of precipitates calcination T SLM 2008, Belgrade by N 2 adsorption /desorption SEM, TEM National Technical University of Athens

Results-BA experiments Precipitates: well crystallised gibbsite/bayerite mixtures gibbsite/bayerite/boehmite mixtures NO PURE γ-Al. OOH with the BA experiments 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments PURE nano-crystallite γ-Al. OOH with the AB experiments 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of Temperature and p. H 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of ageing time 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of different acids 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of different acids (T 90 -p. H 7 -t 24 h) Region Ι Crystallites<50 nm Region ΙΙ Transformation of γ-Al. OOH to γ-Al 2 O 3 Region ΙΙΙ Transformations Transformation to γ-Al. OOH of higher crystallinity 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of different acids (T 90 -p. H 7 -t 24 h) SLM 2008, Belgrade National Technical University of Athens

Results-AB experiments Effect of addition rate(T 90 -ph 7 -t 0) Ab. add. 10 ml/min 7 ml/min 5 ml/min 3 ml/min 1 ml/min SLM 2008, Belgrade National Technical University of Athens

Conclusions ü Only the AB experiments resulted in γ-Al. OOH precipitation : effect of Al-species ü T & p. H: better crystallinity in less tageing ü HCl : higher specific surface area ü addition rate 5 ml/min: most promising for the precipitation of nanocrystallite γ-Al. OOH and calcined products for catalytic applications 3/9/2021 SLM 2008, Belgrade National Technical University of Athens

Thank you ! 3/9/2021 SLM 2008, Belgrade