Laboratoire Catalyse & Spectrochimie October 17, 2012 Carry le Rouet, France Zeolite formation a particular case of hydrothermal crystallization Valentin Valtchev ENSICAEN, Université de Caen, CNRS 6 bd du Maréchal Juin, 14050 Caen, France http:/www-lcs.ensicaen.fr
Outlines I. Zeolites general information II. Zeolite formation - questions to be answered III. Zeolite nucleation in alkali metal containing hydrogel systems Example: LTL-type nucleation V. Zeolite growth Example: LTL-type zeolite growth VI. Concluding remarks 2
Zeolites basic characteristics Crystalline microporous solids Chemical composition: (Mn+)x/n [AlxSiy-xO2y].zH2O (Si4+O4) = (Al3+O4) + M+ M H, Li, Na, K, Cs, Ba, Ca, Mg, organic cation Microporous crystals able to display molecule recognition, discrimination, and organization properties with a resolution of less than 1 Å. Pore size : 3 20 Å Pore systems : 1-, 2- and 3dimensional pore systems Classification IUPAC (h 0 0) (h k 0) b a
Zeolites basic characteristics 201 Framework type Framework composition (Si, Al, Ge, Ga, Ti, Fe, B, P,..) High specific surface area (300 900 m2 g-1) Channel systems with different size and geometry Controllable hydrophilic / hydrophobic properties Acid and base properties Very high thermal stability (> 1000 C) Very high chemical stability Ion exchange properties 4 The total length of the channels of 1 g MFI-type zeolite is 4 times the distance Earth Sun. MFI
Fluid Catalytic Cracking Catalysts and catalysts consumption Market: 15 20 billions US$ per year
Control of zeolite crystal size External surface / Micropore surface ratio
Control of zeolite crystal morphology Zeolite Beta (BEA) c BEA + BAB polymorphs Tetragonal P4122 <100> 6.6 x 6.7 Å [001] 5.6 x 5.6 Å a BEA Slow growth rate of pinacoidal face Rapid growth rate of pinacoidal face Development of a crystal face privileges the access to a particular channel. O. Larlus & V. Valtchev, Chem. Mater. 2005,17, 881-888
Zeolite formation - nucleation Gel composition Structure directing agent Mineralizing agent Nature and ratio between framework cations (Si, Al, Si, Ge, Ga, P, Ti, Zn, ) Impurities Temperature Time Stirring Aging Supersaturation: Δµs =µs - µc µs chemical potential of a molecule in solution µc chemical potential of a molecule in the bulk crystal Δµ = k T ln S K Boltzmann constant T - absolute temperature S - supersaturation ratio Nucleation: Δµ > 0 Zeolite nucleation in alkali metal rich aluminosilicate hydrogel systems : 8 V. Valtchev & K. Bozhilov J. Phys. Chem. B (2004) 108, 15587-15599 Langmuir (2005) 21, 10724-10729 J. Am. Chem. Soc. (2005), 126, 13624 13631 J. Am. Chem. Soc. (2009), 131, 10127-10139 Kossel, W. Nachr. Ges. Wiss Göttingen, Math.-Physik. Kl. (1927) 135 Stranski, I.N. Physik. Chem. 136 (1928) 259
Zeolite A nucleation in a TMATMAcontaining colloidal system (c) 1400 (f) 1200 Intensity 1000 f 800 600 e d c b a 400 (d) 200 0 5 15 25 35 2 Theta, degrees Synthesis time : (a) - 5 min, (b) 1 day, (c) 3 days, (d) 4 days, (e) 5 days, (f) 7 days 9 S. Mintova, N. H. Olson, V. Valtchev & T. Bein, Science 1999, 283, 958 45
General scheme of zeolite formation Structure directing agent: Na+, K+, Organic cations,.. Mineralizing agent: OH- ; FFramework building units: TO4 = SiO4 ; AlO4 Solvent: H2O Low temperature (20 200 C) hydrothermal crystallization. 10 Schematic presentation of the zeolite synthesis process showing the evolution of nucleation and growth rates.
Motivation Questions to be answered: -Which stage of gel evolution are the viable nuclei formed at? -What is the spatial and temporal locations of the nucleation events? Gel formation 11 Re-organization and nucleation Growth
Effect of the composition of the gel structure 12 Zeolite A Zeolite X Zeolite P ZSM-5 Zeolite L Zeolite Beta
A question to be answered: What are the factors controlling the number of nuclei in a zeolite yielding system? Crystal size Comparative study of zeolite L crystal size formation Number of nuclei Micron crystals 13 Nano crystals
Crystal growth kinetics of zeolite L Nano 24 h 16 h 10 20 30 Two theta ( ) 40 4h 3h 2.5 h 2h 0h 50 Gel A: 0.5K2O:0.05Al2O3:1.0SiO2:20H2O 14 20 h Intensity (a.u.) Intensity (a.u.) Micron 10 20 30 Two theta ( ) 40 18 h 14 h 10 h 8h 4h 0h 50 Gel B:0.3K2O:0.09Al2O3:1.0SiO2:16H2O
0,0 15 Nanocrystals 24 h 16 h 4h 3h 2.5 h 2h 0h 0,2 0,4 0,6 0,8 Relative pressure (P/P0) 1,0 Adsorbed Volume (cm3g-1) STP Adsorbed volume (cm3g-1) STP Nitrogen adsorption isotherms Microcrystals 24 h 12 h 8h 4h 2h 0h 0,0 0,2 0,4 0,6 0,8 Relative pressure (P/P0) 1,0
Crystal growth kinetics Nano Micron 24 h 3h 2h 1h Intensity (a.u.) Intensity (a.u.) 20 h 7h 6.5 h 6h 4h 0h 200 16 300 400 500-1 Raman shift (cm ) 600 200 Raman study 400-1 Raman shift (cm ) 600 2h 0h
Physical features of z. L precursor gels N2 adsorption (0.3K2O:0.09Al2O3:1.0SiO2: 16.0H2O) micron-sized crystals Hydrothermal treatment (h) 0 4 5 6 7 8 9 18 20 S BET (m²g-1) Micropore area (m²g-1) External surface area (m²g -1) Total pore Volume (cm³g-1) Micropore volume (cm³g-1) 30 25 30 30 25 25 310 310 370 5 5 10 5 10 15 290 290 350 25 20 20 25 15 10 20 20 20 0.15 0.13 0.11 0.08 0.06 0.02 0.15 0.15 0.17 0.00 0.00 0.00 0.00 0.00 0.01 0.11 0.11 0.14 N2 adsorption (0.5K2O:0.05Al2O3:1.0SiO2: 20.0H2O) nano-sized crystals 17 Hydrothermal treatment (h) 0 1 2 2.5 3 3.5 4 8 24 S BET (m²g-1) Micropore area (m²g-1) External surface area (m²g -1) Total pore Volume (cm³g-1) Micropore volume (cm³g-1) 240 185 110 80 465 480 460 510 505 20 20 25 30 290 310 285 310 315 220 165 85 50 175 170 175 200 190 0.8 1.0 0.9 0.2 0.4 0.5 0.5 0.5 0.5 0.00 0.00 0.00 0.01 0.10 0.13 0.13 0.13 0.13 TEM TEM
TEM study Ludox HS-30 18 Aerodisp W1226
TEM study Nano 0 h 19 Micro 0 h Initial gels yielding nano- (left) and micron- (right) sized crystals.
TEM study Nano 1h 20 Micro 4h Induction period: nano- (left) and micron- (right) sized crystals.
TEM study Nano LTL 3h 21 Micro LTL 20h
Gel morphology Gel chemistry Gel A mother liquor: Si 940 ppm Al 5850 ppm K 258300 ppm gel A: 0.5K2O:0.05Al2O3:1.0SiO2:20H2O Solid phase gel B: 0.3K2O:0.09Al2O3:1.0SiO2:14H2O 22 L. Itani, K. N. Bozhilov, G. Clet, L. Delmotte, V. Valtchev Chemistry A European Journal 2011, 17, 2199 2210
Chemical homogenization of the systems Pogress of reaction (%) 100 80 60 x n (Gel A) x m (Gel 40 B) 20 0 0 500 Time (min) 1000 1500 The chemical homogenization is reckoned to be defined by, the progress of the reaction in terms of approaching the stoichiometric zeolite L composition. By definition = (ct-c0)/(c0-cf), where ct is the K/Si ratio at a specific reaction time t, c 0 at the beginning of the reaction, and cf is the final stoichiometric K/Si ratio of 0.4. 23
Nanosized zeolite L precursor SiO2 / K2O = 1.0 24
Micron-sized zeolite L precursor SiO2 / K2O = 0.25 SiO2 / K2O = 0.25 25
Conclusions The polymerization reaction at room temperature predetermines to a great extent the reaction pathway during hydrothermal treatment: The morphological characteristics of initial gels remained unchanged throughout the induction period. The gel composition changed gradually to reach values close to the final zeolite composition. The size of the final zeolite crystals can be directed by careful and systematic control of the starting gel chemistry, which enables synthesis of nanometer- or micronsized zeolite particles with uniform crystal size distribution. 26
Mechanism of zeolite growth as a function of supersaturation
Mechanism of zeolite growth as a function of supersaturation Supersaturation evaluation as a function of time for zeolite A synthesis: (b-d) correspond to time interval 1, 2 and 3, respectively.
Aggregation around a crystallization center 29
Aggregation around a crystallization center 30
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LTL-type zeolite growth Cancrinite cages Haxagonal (001) face Terrace 1.4 nm Prismatic (100) face Terrace - 1.2 nm Terrace - 1.6 nm
Zeolite L crystal morphology View along <001> H2O C LTL-type P6/mmm [001] 7.1 x 7.1 Å 1 SiO2 : 0,25 K2O : 0,08 Al2O3 : x H2O O. Larlus & V. Valtchev, Chem. Mater. 2004,16, 3381 H2O C 1 SiO2 : 0,25 K2O : 0,08 Al2O3 : x H2O 33
Effect of zeolite crystal morphology on film orientation C 34
Summary A) Zeolite crystal size Determines the ration external / internal surface area. Nanocrystals: useful tool for preparation of complex polycrystalline zeolite macrostructures. B) Zeolite crystal morphology Preferential development of a desired crystal face: - privileges the access to a particular channel system; - determines the number of pore opening per unit crystal surface. Important factor in the preparation of complex functional surfaces comprising extended zeolite layers. C) Structured zeolite materials Materials with new functionality Synergy between different type of materials Extend the area of application of microporous materials 35
Acknowledgements Colleagues Postdocs PhD students Svetlana Mintova Christian Fernandez S. Roy Chowdhury L. Tosheva Normandy: Halloween November, 2011 F. Gaslain O. Larlus Lubomira Tosheva L. Tosheva F. Guillou Thomas Bein Y. Bouizi Y. Bouizi Krassimir Bozhilov N. Mahé Y. Mathieu Jean-Pierre Gilson F. Gao A. Jacob Georgi Vayssilov L. Lakiss A. Darwiche Maguy Jaber Zh. Qin L. Itani Javier Perez-Ramirez M. El Roz A. Palcic Avelino Corma X. Zou Tatsuya Okubo K.G. Haw Sponsors: CNRS, TOTAL, Grace Davison, IFP, CNES, CEA, DGA, ANR,.. 36