Mechanochemically assisted hydrothermal synthesis of Sn-substituted MFI-type silicates

Figures & data

Figure 1. XRD patterns of a mixture of the amorphous Sn(OH)₄ powder and fumed silica for the Si/Sn molar ratio of 20; (a) before the mechanochemical treatment; (b) after grinding for 12 h, g(SiO₂–SnO₂)₁₂; (c) after grinding for 24 h, g(SiO₂–SnO₂)₂₄ (all patterns are vertically offset for clarity).

Figure 2. UV-vis spectra of a mixture of the amorphous Sn(OH)₄ powder and fumed silica for the Si/Sn molar ratio of 20; (a) before the mechanochemical treatment; (b) after grinding for 12 h, g(SiO₂–SnO₂)₁₂; (c) after grinding for 24 h, g(SiO₂–SnO₂)_24.

Figure 3. Sn 3d_3/2 and 3d_5/2 XPS spectra of (a) before the mechanochemical treatment; (b) after grinding for 24 h, g(SiO₂–SnO₂)_24.

Figure 4. XRD patterns of Sn-MFI silicates Sn-S_MC obtained by changing the HCl/Si molar ratio: (a) 0.20; (b) 0.25; (c) 0.30; (d) 0.35; (e) 0.36; (f) 0.37; (g) 0.38 (all patterns are vertically offset for clarity).

Figure 5. SEM images of Sn-MFI prepared with various HCl/Si molar ratios: (a) 0.20; (b) 0.25; (c) 0.30; (d) 0.35; (e) 0.36; (f) 0.37. The scale bar shown in (f) is common for all images. The insets are 2-fold magnified images for observing the surface roughness of the solid particles.

Figure 6. UV-vis spectra of Sn-MFI silicates Sn-S_MC prepared at various HCl/Si molar ratios: (a) 0.20; (b) 0.25; (c) 0.30; (d) 0.35; (e) 0.36; (f) 0.37; (g) 0.38 (all spectra are vertically offset for clarity).

Figure 7. FTIR spectra of Sn-MFI silicates Sn-S_MC obtained at various HCl/Si molar ratios: (a) 0.20; (b) 0.25; (c) 0.30; (d) 0.35; (e) 0.36 (all spectra are vertically offset for clarity).

Table 1. The Sn content, BET surface area, and the external surface area of Sn-S_MC.

HCl/Si	Sn content (wt%)	S BET (m^2/g)	S ext (m^2/g)	V total (mL/g)	V micro (mL/g)	d ave ^a (nm)	Crystallite size (nm)^b
0.20	1.9	462	26	0.31	0.17	380	61
0.25	2.0	454	4	0.24	0.19	610	60
0.30	2.5	459	11	0.23	0.18	940	49
0.35	3.1	495	79	0.28	0.18	1180	32
0.36	3.1	527	86	0.31	0.19	1080	32

^aParticle diameters determined by averaging over more than 130 particles in SEM images (Figure 5).

^bCalculated with the Scherrer equation from the half-width of the XRD patterns shown in Figure 4.

Figure 8. Nitrogen sorption isotherms of Sn-MFI silicates Sn-S_MC obtained at various HCl/Si molar ratios: (a) 0.20; (b) 0.25; (c) 0.30; (d) 0.35; (e) 0.36.

Figure 9. FTIR spectra using CD₃CN as a probe molecule for (a) Sn-S_MC (HCl/Si = 0.20); (b) Sn-S_MC (HCl/Si = 0.36); (c) Sn-S_HT (HCl/Si = 0.19).