Preparation and Characterization of HZSM-5/SAPO-11 Composite Molecular Sieves and Their Catalytic Properties in Isobutane Aromatization†

doi:10.7503/cjcu20160369

Abstract

Abstract:

HZSM-5/SAPO-11 composite molecular sieves with different silicon contents were synthesized hydrothermally via in situ overgrowth of SAPO-11 on ZSM-5 pretreated by polydiallyldimethylammonium chloride(PDDA), and were characterized by means of XRD, SEM, TEM, FTIR and NH₃-TPD. The catalytic activity, stability and BTEX(benzene, toluene, ethylbenzene and xylenes) selectivity of HZSM-5/SAPO-11 in isobutane aromatization were also investigated. All the results were compared with those of ZSM-5, SAPO-11, and the mechanical mixtures of ZSM-5 and SAPO-11 and showed that the ZSM-5/SAPO-11 composites were composed of ZSM-5 covered by about 20 nm SAPO-11 round crystals, that modulation of ZSM-5/SAPO-11 acidity by altering Si content could effectively enhance the synergetic aromatization effect between strong and weak acids and restrain the cracking of iso-butane and the generation of C9⁺, thus the liquid yield and stability of aromatization were superior to HZSM-5 and mechanical mixtures when the Si content reaches 0.6 significantly.

Key words: HZSM-5/SAPO-11 Composite molecular sieve, Isobutane, Aromatization

CLC Number:

O643

TrendMD:

ZHANG Ruizhen, WEN Shaobo, XING Pu, ZHAO Xin, WANG Zhixiang, HAN Peide, ZHAO Liangfu. Preparation and Characterization of HZSM-5/SAPO-11 Composite Molecular Sieves and Their Catalytic Properties in Isobutane Aromatization^†[J]. Chem. J. Chinese Universities, 2017, 38(1): 126.

Figures/Tables 8

Fig.1 XRD patterns(A) and micro-region XRD patterns(B) of different catalysts a. HZSM-5; b. SAPO-11-0.6; c. MZS-0.6; d. CZS-0.2; e. CZS-0.4; f. CZS-0.6; g. CZS-0.8.

Fig.2 FTIR spectra of different catalystsa. HZSM-5; b. MZS-0.6; c. CZS-0.6; d. SAPO-11-0.6.

Fig.3 SEM[(A)—(D)] and TEM[(E), (F)] images and EDS analysis[(G), (H)] of molecular sieves HZSM-5(A), SAPO-11-0.6(B) and CZS-0.6(C—H)

Fig.4 NH3-TPD spectra of different catalysts(A) a. HZSM-5; b. SAPO-11; c. CZS-0.6; d. MZS-0.6. (B) a. SAPO-11-0.2; b. SAPO-11-0.4; c. SAPO-11-0.8; d. SAPO-11-0.6. (C) a. CZS-0.2; b. CZS-0.4; c. CZS-0.8; d. CZS-0.6.

Fig.5 Isobutane conversions(A) and average liquid yields(B) over different catalysts for 8 h a. HZSM-5; b. CZS-0.2; c. CZS-0.4; d. CZS-0.6; e. CZS-0.8; f. MZS-0.6.

Fig.6 Selectivity of C1, C2 alkanes in the gas hydrocarbon and C5—C9+ in liquid aromatics a. MZS-0.6; b. HZSM-5; c. CZS-0.2; d. CZS-0.4; e. CZS-0.6; f. CZS-0.8.

Fig.7 Conversions of iso-butane aromatization over different catalysts for 32 h(A) a. HZSM-5; b. MZS-0.6; c. CZS-0.6. (B) a. HZSM-5; b. CZS-0.2; c. CZS-0.4; d. CZS-0.6; e. CZS-0.8.

Fig.8 Liquid yields of iso-butane aromatization over different catalysts for 32 h(A) a. HZSM-5; b. MZS-0.6; c. CZS-0.6. (B) a. HZSM-5; b. CZS-0.2; c. CZS-0.4; d. CZS-0.6; e. CZS-0.8.

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