Nucleation of FAU and LTA Zeolites from Heterogeneous Aluminosilicate Precursors Matthew D. Oleksiak 1, Jennifer A. Soltis 2,4, Marlon T. Conato, 1,3 R. Lee Penn 2, Jeffrey D. Rimer 1* 1 University of Houston, Department of Chemical and Biomolecular Engineering, Houston, TX USA 2 University of Minnesota, Department of Chemistry, Minneapolis, MN USA 3 University of the Philippines, Institute of Chemistry, Diliman, Quezon City Philippines 4 Current Address: Pacific Northwest National Lab, Physical and Computational Sciences Directorate, Richland, WA 99354 USA * Correspondence sent to: jrimer@central.uh.edu SUPPORTING INFORMATION Table of Contents Page S1. Powder X-Ray Diffraction S2 S2. Light Scattering Measurements S7 S3. Transmission Electron Microscopy Measurements S8 List of Figures Figure S1: Time-elapsed XRD patterns of composition C2 heated at 65 C. Figure S2: Time-elapsed XRD patterns of composition C3 heated at 65 C. Figure S3: Time-elapsed XRD patterns of composition C4 heated at 65 C. Figure S4: Time-elapsed XRD patterns of composition C5 heated at 65 C. Figure S5: Time-elapsed XRD patterns of composition C6 heated at 65 C. Figure S6: Time-elapsed XRD patterns of composition C7 heated at 65 C. Figure S7: Time-elapsed XRD patterns of composition C8 heated at 65 C. Figure S8: Time-elapsed XRD patterns of composition C9 heated at 65 C. Figure S9: Time-elapsed XRD patterns of composition C1 heated at 65 C using S2 S3 S3 S4 S4 S5 S5 S6 S6 LUDOX SM-30 as the silica source. Figure S10: Representative DLS correlation function of LUDOX AS-40 particles. Figure S11: DLS measurements of samples before and after heating in the presence of alumina. Figure S12: Arrhenius plot for dissolution rates presented in Figure 5. Figure S13: Particle size distribution of the sample in Figure 4A. S7 S8 S8 S9 S1
List of Figures (continued) Figure S14: Time-elapsed DLS measurements of LUDOX AS-40 particles aged at 25 C. Figure S15: Time-elapsed EFTEM of a C3 sample heated at 65 C with Si and Al mapping. Figure S16: EDS of composition C3 heated at 65 C for 2.5 h. Figure S17: EDS data corresponding to Area 1 in Figure 9. Figure S18: HRTEM of composition C3 heated at 65 C for 9 h. Figure S19: SAED pattern of composition C3 heated at 65 C for 9 h. Figure S20: STEM image of the particle selected for the EDS line scan in Figure 3C Figure S21: Picture of the TEOS-based growth solution after heating for 24 hours at 65 C S9 S10 S11 S11 S12 S12 S13 S13 S1. Powder X-Ray Diffraction Systematic studies of zeolite crystallization were performed at 65 C for various times using synthesis solutions with a molar composition of x SiO 2 : y Al 2 O 3 : 10 NaOH: 173 H 2 O. The following figures contain time-elapsed powder XRD patterns of zeolites showing the evolution of zeolite phase behavior over time. Figure S1. X-ray diffraction patterns for a growth solution with a C2 molar composition. These samples were heated at 65 C for 2, 4, 6, 8, 10, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 10 h of heating. S2
Figure S2. X-ray diffraction patterns for a growth solution with a C3 molar composition. These samples were heated at 65 C for 0, 6, 12, 24, and 168 h. The first zeolite phase detected was LTA, followed by a LTA-to-FAU intercrystalline conversion that was completed after ca. 24 h of heating. Figure S3. X-ray diffraction patterns for a growth solution with a C4 molar composition. These samples were heated at 65 C for 2, 4, 6, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 12 h of heating. S3
Figure S4. X-ray diffraction patterns for a growth solution with a C5 molar composition. These samples were heated at 65 C for 2, 3, 4, 6, 12, 24, and 168 h. Initially a mixture of FAU and LTA was formed, followed by the disappearance of LTA in favor of a fully crystalline FAU sample. Figure S5. X-ray diffraction patterns for a growth solution with a C6 molar composition. These samples were heated at 65 C for 2, 4, 6, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 12 h of heating. S4
Figure S6. X-ray diffraction patterns for a growth solution with a C7 molar composition. These samples were heated at 65 C for 2, 4, 6, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 12 h of heating. Figure S7. X-ray diffraction patterns for a growth solution with a C8 molar composition. These samples were heated at 65 C for 2, 4, 6, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 6 h of heating. S5
Figure S8. X-ray diffraction patterns for a growth solution with a C9 molar composition. These samples were heated at 65 C for 2, 3, 4, 6, 12, 24, and 168 h. The only zeolite phase that formed was FAU after ca. 3 h of heating. Figure S9. X-ray diffraction patterns for a growth solution with a C1 molar composition prepared with LUDOX SM-30 (i.e., 8 nm colloidal particles) as the silica source. These samples were heated at 65 C for 6, 10, 12, and 24 h. The only zeolite phase that formed was FAU after ca. 10 h of heating. S6
S2. Light Scattering Measurements Samples for DLS were prepared in the following manner. The growth solution was equally divided into 12-mL plastic centrifuge tubes (ca. 10 ml each), which were placed in a water bath regulated at the appropriate temperature. Samples were removed from the bath at periodic times and quenched in an ice bath for 30 seconds. Aliquots of each growth solution (10 drops) were diluted in 12 ml of DI-water and filtered with a 0.45 m membrane to achieve an adequate count rate for DLS measurements (e.g. 20 to 150 kcps). The DLS measurements were performed at 25 C assuming a viscosity and refractive index of pure water, which is reasonable given the large degree of dilution needed to achieve a particle volume fraction of ca. 3% for these studies. The correlation function was measured for duration of 2 minutes. Figure S10. Example correlation function obtained from a DLS measurement of LUDOX AS-40 particles diluted in DI water showing the correlation coefficient as a function of delay time. An average of three measurements yielded a particle size of 24.3 ± 0.1 nm that was obtained using the method of cumulants.. S7
Figure S11. Hydrodynamic diameter D H of LUDOX AS-40 particles suspended in an Al-free solution with a C3 molar composition (3.9 SiO 2 :0 Al 2 O 3 :10 NaOH:173 H 2 O ). Time-elapsed measurements were performed at 25 C. The size of the colloidal particles decreased by ca. 6% during room temperature aging. Figure S12. An Arrhenius plot of the dissolution rates plotted in Figure 5 of the manuscript reveals a linear trend with apparent activation energy E A = 87.2 kj/mole. Data points (symbols) are the average of 3 separate measurements; the solid line is a linear regression; and error bars equal two standard deviations. S3. Transmission Electron Microscopy Measurements Synthesis solutions prepared with molar compositions C1 and C3 were analyzed by TEM prior to and after heating at 65 C for various times. All heated samples were removed from the oven, quenched to room temperature, and immediately redispersed in DI water. Samples with composition C1 were dialyzed using previously reported methods. 1 TEM micrographs revealed an increase in particle size with time, which is consistent with DLS measurements. The particle diameter in TEM micrographs was 30 to 60 nm; therefore, the 150-nm size measured by DLS for the corresponding sample was attributed to particle aggregation. This is qualitatively consistent with the visual appearance of increased turbidity upon the addition of alumina to a suspension of 25-nm LUDOX particles. EFTEM images showed that the spatial separation of Si and Al regions within precursors persists with initial heating time where Si-rich particles are surrounded by an Al-rich solution. S8
Figure S13. Histogram showing the particle size distribution of 43 particles in Figure 4A. The average particle size was 27 ± 3 nm. Figure S14. EFTEM images of solids extracted from synthesis solutions with a C1 molar composition. The samples were heated for various times at 65 C. EFTEM elemental mapping shows (top row) Al distributed around the particles and (bottom row) Si-rich solid particles. After 2.5 h of heating the sample remained heterogeneous in elemental composition. S9
Figure S15. Solids extracted from a growth solution with a C1 molar composition that was aged for 24 h at room temperature. The solution was prepared using LUDOX SM-30 as the silica source. During TEM analysis, EDS line scans across single particles were obtained to assess the spatial distribution of silicon, aluminum, and oxygen in the particle (see Figure 3). Analyses of multiple samples revealed a pseudo core-shell structure consisting of a Si core and an Al shell. It appears that the shell is not uniform for all particles, as evidenced by EDS line-scan profiles showing an asymmetrical Al content surrounding the Si core. For a sample that was heated for 2.5 h, we performed EDS analysis at focused beam locations along particle cross-sections. Interestingly, we observed a wide range of Si/Al ratio that varied from 2 to 70, as shown in Figure S15. S10
Figure S16. EDS analysis of precursors extracted from a C3 growth solution heated at 65 C for 2.5 h. The discrete spatial locations with corresponding Si/Al ratio (listed in parentheses) are as follows: 13 (2.1), 9 (69.0), 10 (11.4), 11 (6.3), 12 (2.5), 3 (14.1), and 4 (23.7). In Figure 9, the average EDS values for different areas of a C1 sample were reported. In Figure S16 we show representative EDS measurements used to obtain the average Area 1 composition. Scans 1.1 and 1.4 contain areas with lattice fringes while scans 1.2 and 1.3 focus primarily on amorphous material. The lower Si/Al value for the crystalline domains is consistent with aluminum incorporation during crystal growth and the redistribution of Si and Al during crystallization. Figure S17. Atomic percentage (left axis) and Si/Al ratio (right axis) from an EDS scan of Area 1 in Figure 9B. The average of these measurements is presented in Figure 9C. S11
Figure S18. HRTEM image of a particle extracted from a C1 molar composition after heating for 9 h at 65 C: (A) Low magnification image and the corresponding (B) magnified image of the area labelled by the white box. Lattice fringes (white circle) were observed on the edge of the particle, suggesting that crystals nucleate on the exterior surface of amorphous core-shell precursors. Figure S19. SAED pattern of the area highlighted in Figure 8 reveals the presence of crystalline domains. S12
Figure S20. Scanning transmission electron microscope (STEM) image of the sample used to obtain an EDS line scan of core-shell precursor particles. The red line indicates the path selected for the line scan. The fact that the image appears slightly out of focus is attributed to weak scattering of electrons by low-z elements, which decrease the definition at particle edges, and interaction volume effects. Moreover, the particle size appears larger than those depicted in TEM images (e.g., Figure 3A) due, in part, to lateral drift during the measurement. As such, the core and shell dimensions in Figure 3C are not exact. The STEM analysis, however, does confirm the heterogeneous distribution of Si and Al in the core and shell domains, respectively. Figure S21. Picture of a growth solution prepared with TEOS silica source after the mixture was heated for 24 hours at 65 C. The biphasic solution contains a thin upper layer comprised of non-hydrolyzed TEOS, confirming the slow release of silica into the aqueous solution during zeolite crystallization. S13