Hollow ZSM-5 Zeolite Microspheres with Improved Adsorption and Catalytic Properties

doi:10.15541/jim20150611

Abstract

Abstract:

A new kind of uniform hollow zeolite spheres were successfully synthesized by non-hard template synthetic method, which involves two key steps: firstly, the conventional hydrothermal synthesis process of zeolite spheres by using polyethylene glycol (PEG) as soft template, and then, the rapid post-alkaline-etching (PAE) technique. Structural features were characterized by XRD, N₂ isotherm, SEM, and TEM. The performance in the organic-waste-water treatment and catalytic cracking of bulky molecules were also measured. It was found that crystallinity of the product underwent a reducing tendency after alkaline etching treatment, but the mesoporosity and pore volume were promoted. The diameter and shell thickness of hollow zeolite spheres were about 600 nm and 100 nm, respectively. Moreover, such hollow structure demonstrates remarkably a threefold capability increase in adsorption of benzene molecules in methanol solution if compared with conventional zeolite spheres. Such capability can be basically kept after repeating 6 times, indicating high capability and stability in adsorption. Enhanced catalytic activities were also approved in cracking of isopropyl benzene and triisopropyl benzene.

Key words: hollow zeolite sphere, alkaline etching, adsorption, benzene, waste water, catalytic cracking

CLC Number:

TQ174

SUN Li-Li, YAN Kai, LUO Wen, ZHOU Jian. Hollow ZSM-5 Zeolite Microspheres with Improved Adsorption and
Catalytic Properties[J]. Journal of Inorganic Materials, 2016, 31(8): 834-840.

Figures/Tables 11

Fig. 1 XRD patterns of zeolite spheres (ZS) and hollow zeolite spheres (HZS)

Fig. 2 N2 isotherms and pore size distributions (inset) of zeolite spheres (ZS) and hollow zeolite spheres (HZS)

Fig. 3 SEM images of zeolite spheres (a, b) and hollow zeolite spheres (c-f)

Table1 Textural and structural properties of zeolite spheres(ZS) and hollow zeolite spheres(HZS)

Sample	Al content^a/%	S_BET^b/ (m²·g^-1)	S_meso^c/ (m²·g^-1)	V_pore^d/ (cm³·g^-1)	V_meso^c/ (cm³·g^-1)
ZS	1.74	347	152	0.21	0.09
HZS	2.01	335	167	0.37	0.29

Fig. 4 TEM images of zeolite spheres (ZS) and hollow zeolite spheres (HZS)

Fig. 5 Adsorption dynamic curves of benzene by zeolite spheres (ZS) and hollow zeolite spheres (HZS) in methanol solution

Fig. 6 Adsorption isotherms of benzene by zeolite spheres (ZS) and hollow zeolite spheres (HZS). Ce is the equilibrium concentration in the benzene/methanol solution and Qe is the amount of benzene adsorbed at equilibrium concentration

Fig. 7 Adsorption stability testing results of zeolite spheres (ZS) and hollow zeolite spheres (HZS). Relative adsorption amount is the ratio of adsorption amount in the single cycle to the adsorption amount in the first cycle

Fig. 8 TEM images and electron diffraction patterns (insert) of hollow zeolite spheres (HZS) after cycle use

Table2 Catalytic properties of zeolite spheres (ZS) and hollow zeolite spheres (HZS) in cracking reaction

Reaction	Conversion in cumene cracking /%		Conversion in triisopropylbenzene cracking /%
Catalyst	ZS	HZS	ZS	HZS
573 K	55.1	66.9	12.6	34.8
623 K	72.6	80.2	27.6	50.0
673 K	82.7	90.0	39.9	61.1
723 K	88.8	94.3	51.0	72.5
773 K	92.2	97.3	61.0	78.4

Table3 Selectivity of products by zeolite spheres (ZS) and hollow zeolite spheres (HZS) in cracking reaction of TIPB

Reaction	Selectivity of benzene: isopropylbenzene: diisopropylbenzene
Catalyst	ZS	HZS
300	11: 20: 69	13: 23: 64
350	15: 18: 67	16: 22: 62
400	19: 19: 62	19: 24: 57
450	22: 25: 55	25: 26: 49
500	28: 30: 42	28: 33: 39

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