Synthesis and Catalytic Performance of 2D HZSM-5 Nano-sheet for Ethylbenzene Production from Benzene with Dilute Ethylene

doi:10.7503/cjcu20180670

Abstract

Abstract:

2D HZSM-5 nano-sheet with different b-axis thickness and Si/Al atom ratios were synthesized by seed-induced method under the hydrothermal conditions, using tetrapropylammonium bromide as the template, ethylamine as the mineralizer, silica sol as the silicon source, aluminium chloride as the aluminium source and the 60 nm silicate-1 as the crystal seed, respectively. And the 2D hierarchical HZSM-5 nano-sheet were obtained by alkaline treatment with different sources, including NaOH treatment, tetrapropylammonium hydroxide(TPAOH) treatment, and NaOH with TPAOH co-alkaline treatment. The structure and acidity of the samples were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), Ar adsorption-desorption, ammonia temperature-programmed desorption(NH₃-TPD), X-ray fluorescence(XRF) and X-ray photoelectron spectroscopy(XPS). The effects of Si/Al atom ratio and the thickness of b-axis on the alkylation of benzene with dilute ethylene were investigated. The research results show that, under the reaction conditions of 360 ℃, 1.4 MPa, the molar ratio of benzene/ethylene is 6, and the concentration and weight hourly space velocity(WHSV) of ethylene were 15% and 1.5 h^-1, the conversion of benzene decreased slightly with the increasing of Si/Al atom ratio, the ethyl selectivity maintained above 99.2%, while the selectivity of toluene and xylene decreased from 0.11% and 0.09% to 0.05%, respectively. The HZSM-5 catalysts with different b-axis thickness were evaluated under the condition of benzene/ethylene is 1, the microscale HZSM-5 with the high silica content deactivated seriously. The conversion of benzene declined from 34.6% to 8% during 50 h, and the ethyl selectivity was 88%. While the benzene conversion of 2D HZSM-5 nano-sheet with same Si/Al atom ratio was stable at 44.0%, the ethyl selectivity reached to 94.8%, and the xylene selectivity reduced from 0.37% to 0.22%.

Key words: HZSM-5 zeolite, Acid catalysis, Ethylbenzene, Alkylation of benzene with ethylene

CLC Number:

O643.3

TrendMD:

BIAN Kai, HOU Zhanggui, DUAN Xinrui, LI Xiaoguo, CHANG Yang, CAO Hui, ZHANG Anfeng, GUO Xinwen. Synthesis and Catalytic Performance of 2D HZSM-5 Nano-sheet for Ethylbenzene Production from Benzene with Dilute Ethylene[J]. Chem. J. Chinese Universities, 2019, 40(4): 784.

Figures/Tables 12

Fig.1 SEM images of nano-sheet HZSM-5 zeolitesSi/Al atom ratio: (A) 80; (B) 120; (C) 160; (D) 200.

Fig.2 NH3-TPD profiles of HZSM-5 zeolites with different Si/Al atom ratios

Fig.3 Catalytic performance of HZSM-5 zeolites with different Si/Al atom ratiosReaction conditions: T=633 K, p=1.4 MPa, n(C6H6)/n(C2H4)=6, WHSV(C2H4)=1.5 h-1, φ(C2H4)=15%. (A) Z5-80; (B) Z5-120; (C) Z5-160; (D) Z5-200.

Table 1 Catalytic performance of HZSM-5 zeolites with different Si/Al atom ratios

Catalyst	C₆H₆ conversion(%)	Product selectivity(%)					EB+DEB yield(%)
Catalyst	C₆H₆ conversion(%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)
Z5-80	13.1	0.11	99.1	0.09	0.61	0.08	12.98
Z5-120	12.5	0.09	99.0	0.07	0.81	0.09	12.38
Z5-160	12.8	0.05	99.4	0.05	0.47	0.05	12.72
Z5-200	12.4	0.05	99.2	0.05	0.58	0.07	12.30

Table 1 Catalytic performance of HZSM-5 zeolites with different Si/Al atom ratios

Catalyst	C₆H₆ conversion(%)	Product selectivity(%)					EB+DEB yield(%)
Catalyst	C₆H₆ conversion(%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)
Z5-80	13.1	0.11	99.1	0.09	0.61	0.08	12.98
Z5-120	12.5	0.09	99.0	0.07	0.81	0.09	12.38
Z5-160	12.8	0.05	99.4	0.05	0.47	0.05	12.72
Z5-200	12.4	0.05	99.2	0.05	0.58	0.07	12.30

Fig.4 SEM images of HZSM-5 zeolites with different b-axis thicknesses (A) Z5-160-0; (B) Z5-160-0.01%; (C) Z5-160; (D) Z5-160-3%.

Fig.5 Catalytic performance of HZSM-5 zeolites with different b-axis thicknessesReaction conditions: T=633 K, p=1.4 MPa, n(C6H6)/n(C2H4)=1, WHSV(C2H4)=1.5 h-1, φ(C2H4)=15%. (A) Z5-160-0; (B) Z5-160-0.01%; (C) Z5-160; (D) Z5-160-3%.

Table 2 Catalytic performance of HZSM-5 zeolites with different b-axis thicknesses

Catalyst	C₆H₆ conversion (%)	Product selectivity(%)					EB+DEB yield(%)	Coking rate (%·h^-1)
Catalyst	C₆H₆ conversion (%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)	Coking rate (%·h^-1)
Z5-160-0	34.6	0.94	88.1	0.37	9.19	1.38	30.48	0.11
Z5-160-0.01%	41.2	0.45	93.5	0.25	4.94	0.89	38.44	0.05
Z5-160	44.0	0.45	94.8	0.22	3.69	0.81	41.71	0.05
Z5-160-3%	43.1	0.44	94.1	0.23	4.27	0.95	40.56	0.03

Table 2 Catalytic performance of HZSM-5 zeolites with different b-axis thicknesses

Catalyst	C₆H₆ conversion (%)	Product selectivity(%)					EB+DEB yield(%)	Coking rate (%·h^-1)
Catalyst	C₆H₆ conversion (%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)	Coking rate (%·h^-1)
Z5-160-0	34.6	0.94	88.1	0.37	9.19	1.38	30.48	0.11
Z5-160-0.01%	41.2	0.45	93.5	0.25	4.94	0.89	38.44	0.05
Z5-160	44.0	0.45	94.8	0.22	3.69	0.81	41.71	0.05
Z5-160-3%	43.1	0.44	94.1	0.23	4.27	0.95	40.56	0.03

Fig.6 XRD patterns of HZSM-5 zeolites via different alkaline treatmentsa. Z5-160; b. Z5-NaOH-AT; c. Z5-NaOH-TPAOH-AT; d. Z5-TPAOH-AT.

Fig.7 TEM images of HZSM-5 nano-sheet via different alkaline treatments(A) Z5-160; (B) Z5-NaOH-AT; (C) Z5-NaOH-TPAOH-AT; (D) Z5-TPAOH-AT.

Table 3 Surface areas, pore volumes and acid densities of HZSM-5 nano-sheet with different alkaline treatments

Sample	$S a BET$ / (m²·g^-1)	$V b micro$ / (cm³·g^-1)	$V c t$ / (cm³·g^-1)	Si/Al atom ratio^d	Weak acidity^e/ (μmol·g^-1)	Strong acidity^e/ (μmol·g^-1)	Total acidity^e/ (μmol·g^-1)	Relative crystallinity(%)
Z5-160	505	0.18	0.65	137	37	39	76	100
Z5-NaOH-AT	367	0.14	0.74	69	37	56	93	51
Z5-NaOH-TPAOH-AT	447	0.16	0.97	69	43	55	98	56
Z5-TPAOH-AT	429	0.16	0.50	56	40	55	95	79

Table 3 Surface areas, pore volumes and acid densities of HZSM-5 nano-sheet with different alkaline treatments

Sample	$S a BET$ / (m²·g^-1)	$V b micro$ / (cm³·g^-1)	$V c t$ / (cm³·g^-1)	Si/Al atom ratio^d	Weak acidity^e/ (μmol·g^-1)	Strong acidity^e/ (μmol·g^-1)	Total acidity^e/ (μmol·g^-1)	Relative crystallinity(%)
Z5-160	505	0.18	0.65	137	37	39	76	100
Z5-NaOH-AT	367	0.14	0.74	69	37	56	93	51
Z5-NaOH-TPAOH-AT	447	0.16	0.97	69	43	55	98	56
Z5-TPAOH-AT	429	0.16	0.50	56	40	55	95	79

Fig.8 Catalytic performance of HZSM-5 zeolites with different alkaline treatmentsReaction condition: T=633 K, p=1.4 MPa, n(C6H6)/n(C2H4)=1, WHSV(C2H4)=1.5 h-1, φ(C2H4)=15%. (A) Z5-160; (B) Z5-NaOH-AT; (C) Z5-NaOH-TPAOH-AT; (D) Z5-TPAOH-AT.

Table 4 Catalytic performance of HZSM-5 zeolites with different alkaline treatments

Catalyst	C₆H₆ conversion(%)	Product selectivity(%)					EB+DEB yield(%)	Coking rate/ (%·h^-1)
Catalyst	C₆H₆ conversion(%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)	Coking rate/ (%·h^-1)
Z5-160	44.0	0.45	94.8	0.22	3.69	0.81	41.71	0.05
Z5-NaOH-AT	40.6	0.52	91.9	0.25	5.90	1.43	37.31	0.04
Z5-NaOH-TPAOH-AT	41.1	0.36	93.4	0.20	4.76	1.24	38.67	0.05
Z5-TPAOH-AT	44.0	0.51	93.6	0.24	4.60	1.06	41.18	0.03

Table 4 Catalytic performance of HZSM-5 zeolites with different alkaline treatments

Catalyst	C₆H₆ conversion(%)	Product selectivity(%)					EB+DEB yield(%)	Coking rate/ (%·h^-1)
Catalyst	C₆H₆ conversion(%)	Toluene	EB+DEB	Xylene	C₉	$C 10 +$	EB+DEB yield(%)	Coking rate/ (%·h^-1)
Z5-160	44.0	0.45	94.8	0.22	3.69	0.81	41.71	0.05
Z5-NaOH-AT	40.6	0.52	91.9	0.25	5.90	1.43	37.31	0.04
Z5-NaOH-TPAOH-AT	41.1	0.36	93.4	0.20	4.76	1.24	38.67	0.05
Z5-TPAOH-AT	44.0	0.51	93.6	0.24	4.60	1.06	41.18	0.03

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