Synthesis and Characterization of Hierarchical Mordenite Zeolite

doi:10.15541/jim20170236

Abstract

Abstract:

Hierarchical MOR zeolite nanocrystallines with mesoporous architecture composed of 2~4 nm pores were synthesized via a simple hydrothermal route by adding surfactant CTAB as mesoporous template in the absence of organic co-solvent and zeolite seeds, in which the mesoporous volume and external surface area could be adjusted by changing the amount of CTAB. The largest external surface area and mesoporous volume were 191 m²/g and 0.17 cm³/g. Adsorption of mesitylene on the MOR zeolitic samples showed that only a small amount of adsorption could be found in the microporous mordenite, but a large amount of adsorption in hierarchical mordenite which presented the characteristics of typical IV isotherm indicating a mesoporous structure. Catalytic properties of the MOR zeolitic samples were investigated by benzylation reaction of mesitylene and benzyl chloride. Compared with the traditional microporous mordenite, the reaction conversion on the hierarchical mordenite increased ~7 times and the reaction apparent rate constant increased ~19 times. This property is due to the expansive external surface areas and mesopores volume in the hierarchical mordenite zeolite which can effectively improve accessibility of the bulky reactants to acid sites and mass transfer rate of big products, and greatly promote the catalytic efficiency of bulky molecules.

Key words: CTAB, hierachical pores, benzylation, mordenite, mesitylene adsorption

CLC Number:

TQ426

DAI Guang, XIAO Huan, HAO Wen-Ming, MA Jing-Hong, LI Rui-Feng. Synthesis and Characterization of Hierarchical Mordenite Zeolite[J]. Journal of Inorganic Materials, 2018, 33(4): 397-402.

Figures/Tables 7

Fig. 1 XRD spectra of MOR zeolites synthesized with different amounts of CTAB

Table 1 Texture parameters of zeolites MOR synthesized C-MOR(n)(n = 0, 1, 2, 3)

Samples	S_BET/(m²•g^-1)	S_mic/(m²•g^-1)	S_ext/(m²•g^-1)	V_mic/(cm³•g^-1)	V_meso/(cm³•g^-1)	RC*/%	Crystal size/nm
C-MOR(0)	485	452	33	0.18	0.04	100
C-MOR(1)	501	404	97	0.16	0.10	98.1	51.3
C-MOR(2)	497	368	127	0.16	0.12	87.8	46.1
C-MOR(3)	485	294	191	0.12	0.17	81.3	37.3

Fig. 2 N2 adsorption/desorption isotherms (a) and DFT pore size distribution (b) of zeolites C-MOR(n) (n =0, 1, 2, 3)

Fig. 3 SEM images of C-MOR(n). n =0(a), 1(b), 2(c), 3(d)

Fig. 4 Adsorption isotherms of mesitylene on C-MOR(n) (n = 0, 1, 2, 3) samples at 308 K

Fig. 5 NH3-TPD profiles of C-HMOR(n) (n = 0, 1, 2, 3)

Fig. 6 Catalytic activities of C-MOR(n) (n = 0, 1, 2, 3) zeolites in the benzylation of mesitylene

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