Synthesis of Monolith Hierachical ZSM-5 Zeolite Composed of Nanocrystals by Vapor-phase Transformation Method

doi:10.15541/jim20150171

Abstract

Abstract:

A monolith ZSM-5 composed of nano-sized MFI crystals was prepared from a dry gel by a vapor-phase transformation method, in which the dry gel was obtained from a mixture of sodium carboxymethylcellulose and a precursor yielding ZSM-5 zeolite crystals. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N₂ adsorption-desorption, in-situ IR spectra of pyridine and FT-IR. Organic Si- or/and Al-species replace the classic inorganic Si- or/and Al-species to take part in the construction of MFI zeolite frameworks. And the long chain organic groups, which connect with the Si- and Al-species, disturb the normal growth of the zeolites crystals in the manner of the so called “bond block”. The evenly nano-sized zeolite crystals with the sizes of 100-150 nm are therefore formed and then subsequently self-assembly form a monolith ZSM-5. A mesoporous system which centers around 2-20 nm is therefore introduced into the as-synthesized hierachical zeolites samples. As compared with the references catalysts, the monolith ZSM-5 zeolite composed of nano-sized crystals displays an enhanced conversion of isopropylbenzene because of the dramatically increased external surface areas and mesopores volume as tested by the catalytic cracking of isopropylbenzene.

Key words: ZSM-5, vapor-phase transformation, nano-zeolite, hierachical pores, bond block

CLC Number:

TQ426

ZHENG Jia-Jun, ZHANG Hong-Yan, PAN Meng, LI Biao, ZHANG Qiu, KONG Qing-Lan, LIU Zhi-Ping, LI Rui-Feng. Synthesis of Monolith Hierachical ZSM-5 Zeolite Composed of Nanocrystals by Vapor-phase Transformation Method[J]. Journal of Inorganic Materials, 2015, 30(11): 1161-1166.

Figures/Tables 8

Fig. 1 XRD patterns of the samples (1) ZSM-5(A); (2) ZSM-5(B); (3) ZSM-5(C)

Fig. 2 FT-IR spectra of sample of ZSM-5 zeolite (A): (1) ZSM-5(A); (2) ZSM-5(B); (3) ZSM-5(C); (B): (a) CMC-Na; (b) the precursor gel with CMC-Na; (c) ZSM-5 contained CMC-Na; (d) ZSM-5 has been removed the concealed CMC-Na

Fig. 3 SEM images of sample ZSM-5 zeolite (1) and (2): ZSM-5(A); (3) ZSM-5(B); (4): ZSM-5(C)

Scheme 1 Schematic representation of the process which CMC-Na affects the formation of monolith ZSM-5 consists of nanocrystals

Fig. 4 N2 adsorption-desorption isotherm and pore size distribution curve (inset) of the samples (1) ZSM-5(A); (2) ZSM-5(B); (3) ZSM-5(C)

Table 1 Physical structural properties of the samples

Samples	S_BET /(m²·g^-1)	S_mic /(m²·g^-1)	S_ext /(m²·g^-1)	S_meso /(m²·g^-1)	V_mic /(cm³·g^-1)	V_meso /(cm³·g^-1)	Acidity (Py)*/ (μmol·g)^-1		B/L (Py)	Total acidity /(μmol·g^-1)
Samples	S_BET /(m²·g^-1)	S_mic /(m²·g^-1)	S_ext /(m²·g^-1)	S_meso /(m²·g^-1)	V_mic /(cm³·g^-1)	V_meso /(cm³·g^-1)	Brönsted	Lewis	B/L (Py)	Total acidity /(μmol·g^-1)
ZSM-5(A)	467	362	105	25	0.13	0.10	191	280	0.7	471
ZSM-5(B)	423	396	27	15	0.15	0.03	279	173	1.6	452
ZSM-5(C)	443	438	5	9	0.16	0.02	240	163	1.5	403

Fig. 5 Infrared spectra of pyridine absorbed at 200℃ (1) ZSM-5(A); (2) ZSM-5(B); (3) ZSM-5(C)

Fig. 6 Cracking of isopropyl benzene at 300℃ (1) ZSM-5(A); (2) ZSM-5(B); (3) ZSM-5(C)

References 24

[1]	PÉREZ-RAMÍREZ J, CHRISTENSEN C H, EGEBLAD K, et al. Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design.Chem. Soc. Rev., 2008, 37: 2530-2542.
[2]	VAN DONK S, JANSSEN A H, BITTER J H, et al.Generation, characterization, and impact of mesopores in zeolite catalysts.Catal. Rev., 2003, 45(2): 297-319.
[3]	TAO Y S, KANOH H, ABRAMS L, et al.Mesopore-modified zeolites: preparation, characterization, and applications.Chem. Rev., 2006, 106(3): 896-910.
[4]	TAO Y S, KANOH H, KANEKO K.Synthesis of mesoporous zeolite A by resoreinol-formaldehyde aerogel templating.Langmuir, 2005, 21(2): 504-507.
[5]	TAO Y S, KANOH H, KANEKO K.ZSM-5 monolith of uniform mesoporous channels.J. Am. Chem. Soc., 2003, 125(20): 6044-6045.
[6]	CAMBLOR M A, CORMA A, VALENCIA S J.Characterization of nanocrystalline zeolite Beta.Micropor. Mesopor. Mater., 1998, 25(1/2/3): 59-74.
[7]	LANDAU M V, TAVOR D, REGEV O, et al.Colloidal nanocrystals of zeolite β stabilized in alumina matrix.Chem. Mater., 1999, 11(8): 2030-2037.
[8]	SCHOEMAN B J, BABOUCHKINA E, MINTOVA S, et al.The Synthesis of discrete colloidal crystals of zeolite Beta and their application in the preparation of thin microporous films. J. Porous Mater., 2001, 8(1): 13-22.
[9]	ZHANG Q, TAN W, ZHENG J J, et al.Hierachical zeolite-zeolite composite prepared by a vapor phase transport method.J. Inorg. Mater., 2014, 29(9): 985-990.
[10]	WANG D J, LIU Z N, XIE Z K.Preparation of binder-free utrafine ZSM-5 zeolite monoliths by vapor-phase transformation method.J. Inorg. Mater., 2008, 23(3): 592-596.
[11]	WANG D J, ZHU G B, ZHANG Y H, et al.Template-free secondary growth preparation of zeolite foams with controllable macropores.J. Inorg. Mater., 2005, 20(3): 635-640.
[12]	ZHAO Q Q, QIN B, ZHENG J J, et al.Core-shell structured zeolite-zeolite composites comprising Y zeolite cores and nano-b zeolite shells: synthesis and application in hydrocracking of VGO oil.Chem. Eng. J., 2014, 257(1): 262-272.
[13]	WANG L, PANG F L, WANG A, et al.Preparation and structure characterization of sodium carboxymethylcellulose/montmorillonite nanocomposites. J. Chin. Ceram. Soc., 2010, 38(9): 1820-1825.
[14]	XUE Z T, MA J H, HAO W M, et al.Synthesis and characterization of ordered mesoporous zeolite LTA with high ion exchange ability.J. Mater. Chem., 2012, 22: 2532-2538.
[15]	LV J, ZHANG G C, MA Z Q, et al.Continuous-flow synthesis of submicron and nano-zeolites in capillary microchannel reactor.J. Inorg. Mater., 2011, 26(12): 1304-1308.
[16]	ZHENG J J, ZENG Q H, YI Y M, et al.The hierarchical effects of zeolite composites in catalysis.Catal. Today, 2011, 168(1): 124-132.
[17]	ZHENG J J, WANG G S, PAN M, et al.Hierarchical core@shell zeolite composite ZSM-5@SAPO-34 fabricated by using ZSM-5 as the nutrients for the growth of SAPO-34.Micropor. Mesopor. Mater., 2015, 206: 114-120.
[18]	ZHENG J J, YI Y M, WANG W L, et al.Synthesis of bi-phases composite zeolites MFZ and its hierarchical effects in isopropylbenzene catalytic cracking.Micropor. Mesopor. Mater., 2013, 171: 44-52.
[19]	ZHENG J J, ZHANG X W, ZHANG Y, et al.Structural effects of hierarchical pores in zeolite composite.Micropor. Mesopor. Mater., 2009, 122(1/2/3): 264-269.
[20]	ZHENG J J, ZENG Q H, ZHANG Y Y, et al.Hierarchical porous zeolite composite with a core-shell structure fabricated using β-zeolite crystals as nutrients as well as cores. Chem. Mater., 2010, 22(22): 6065-6074.
[21]	EMEIS C A.Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts.J. Catal., 1993, 141(2): 347-354.
[22]	SIMON-MASSERON A, MARQUES J P, LOPES J M, et al.Influence of the Si/Al ratio and crystal size on the acidity and activity of HBEA zeolites. Appl. Catal. A: Gen., 2007, 316: 75-82.
[23]	CHICA A, CORMA A.Hydroisomerization of pentane, hexane, and heptane for improving the octane number of gasoline. J. Catal., 1999, 187(1): 167-176.
[24]	ARRIBAS M A, MARTÍNEZ A. Simultaneous isomerization of n-heptane and saturation of benzene over Pt/Beta catalysts.(The influence of zeolite crystal size on product selectivity and sulfur resistance). Catal. Today, 2001, 65(2/3/4): 117-122.