Sphere-like Hierarchical Y Zeolite Fabricated by Steam-assisted Conversion Method

doi:10.15541/jim20180361

Abstract

Abstract:

Sphere-like hierarchical Y zeolite was synthesized by a “steam-assisted conversion (SAC)” procedure. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption, solid-state nuclear magnetic resonance (NMR) spectra, and Fourier transform infrared (IR) spectroscopy. Results observed by SEM displayed that the as-synthesized Y zeolite was sphere-like polycrystalline aggregates composed of primary crystals with size of about 50-300 nm. These results exhibited that some polycrystalline aggregates were hollow Y zeolite spheres. Combined with characterization results of FT-IR, ²⁹Si NMR, SEM, and TEM, a mechanism illustrating formation of the hollow Y zeolite polycrystalline spheres was proposed.

Key words: hierarchical, polycrystalline aggregates, hollow sphere, steam-assisted conversion

CLC Number:

TQ174

DU Yan-Ze, YANG Xiao-Na, NING Wei-Wei, KONG Qing-Lan, QIN Bo, ZHENG Jia-Jun, LI Wen-Lin, LI Rui-Feng. Sphere-like Hierarchical Y Zeolite Fabricated by Steam-assisted Conversion Method[J]. Journal of Inorganic Materials, 2019, 34(2): 225-232.

Figures/Tables 11

Fig. 1 XRD patterns of the samples

Fig. 2 SEM images of the as-synthesized YS-x samples(a, b) YP-5.18; (c, d) YS-4.14; (e, f) YS-5.18; (g, h) YS-6.21; (i, j) YS-7.25; (k, l) YS-8.28

Fig. 3 SEM images of the as-synthesized Y zeolite yielding from the gel precursor with different Si/Al ratio(a-d) YS-8.28; (e-g) YS-6.21; (h) YS-5.18; (i) YH-5.18

Fig. 4 TEM image of YS-5.18 (a), TEM image (b) and the corresponding reversed-phase TEM image (c)

Fig. 5 FT-IR spectra of the samples(a) YS-x (solid curves) and the corresponding dried gel precursors YP-x (dotted curves); (b) YS-5.18 and YP-5.18

Fig. 6 SEM images and EDS analysis of the as-synthesized Y zeolite yielding from gel precursor with different Si/Al ratio(a) YS-4.14; (b) YS-5.18; (c) YS-6.21; (d) YS-7.25

Fig. 7 29Si MAS NMR spectra(a) YS-5.18; (b) YP-5.18

Table 1 Quantification by 29Si MAS NMR for sample YS-5.18 and the corresponding dried gel precursor YP-5.18

Sample	*Q1%	Q2%	Q3%	Q4%	Q5%	Si/Al
YS-5.18	18.2	30.8	31.4	13.9	5.7	1.65
YP-5.18	19.7	36.5	7.3	1.3	0	1.27

Scheme 1 Schematic representation of the process for the formation of the sphere-like hierarchical Y zeolite composed of the loosely aggregating nanocrystallites

Fig. 8 N2 adsorption-desorption isotherms (a) and pore size distribution curves (b)

Table 2 Physical structural properties of the samples

Samples	S_BET /(m²•g^-1)	S_mic /(m²•g^-1)	S_ext /(m²•g^-1)	V_mic /(cm³•g^-1)	V_total /(cm³•g^-1)
YS-4.14	739	698	41	0.26	0.34
YS-5.18	837	792	46	0.30	0.40
YS-6.21	791	740	51	0.28	0.38
YS-7.25	730	570	160	0.19	0.31
YH-5.18	735	714	21	0.27	0.35

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