Synthesis of L/W Composite Zeolite and Its Application in FCC Gasoline Hydro-upgrading Catalyst†

doi:10.7503/cjcu20140761

Abstract

Abstract:

A novel L/W composite zeolite was synthesized via the in situ overgrowth of L zeolite on W zeolite and the corresponding physical-chemical property was characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), Fourier transformed infrared(FTIR) spectrometry, N₂ adsorption, infrared spectroscopy of adsorbed pyridine, Raman and H₂-TPR. The results were compared with those of the mechanical mixture composed of the individual L zeolite and W zeolite. In the mechanical mixture, the L zeolite phase was morphologically separated from the W zeolite phase, while the L/W composite zeolite existed in a form of a epitaxial growth structure, with the W zeolite phase as the core and the L zeolite phase as the shell. Compared with the mechanical mixture, the composite had more appropriate pore structure and moderate aci-dity distribution, which could accelerate the diffusion of reactants and enhance the synergetic effect between Brönsted and Lewis acids. The comparison of the catalytic performances of the mechanical mixture and the composite-based Co-Mo catalysts for fluid catalytic cracking(FCC) gasoline hydro-upgrading showed that, due to the above advantages of the composite, the corresponding catalyst exhibited a lower octane number(RON) loss(ΔRON=-1.15) and higher desulfurization efficiency(HDS=93.3%).

Key words: L/W composite zeolite, Fluid catalytic cracking(FCC) gasoline, Catalytic hydrogenation

CLC Number:

O643

TrendMD:

YANG Xu, DUAN Aijun, ZHAO Zhen, JIANG Guiyuan, LIU Jian, WEI Yuechang, LI Jianmei. Synthesis of L/W Composite Zeolite and Its Application in FCC Gasoline Hydro-upgrading Catalyst^†[J]. Chem. J. Chinese Universities, 2015, 36(2): 336.

Figures/Tables 12

Table 1 Composition of the hydro-upgrading catalysts

Catalyst	Mass fraction(%)
Catalyst	L	W	L/W	γ-Al₂O₃	MoO₃	CoO
Cat.1(L)	32.0			48.0	15.0	5.0
Cat.2(W)		32.0		48.0	15.0	5.0
Cat.3(mechanical mixture)	16.0	16.0		48.0	15.0	5.0
Cat.4(L/W composite)			32.0	48.0	15.0	5.0

Fig.1 XRD patterns of different zeolites a. L/W composite; b. mechanical mixture; c. W; d. L.

Fig.2 XRD patterns of zeolite L/W products for different crystallization time a. 6 h; b. 12 h; c.24 h; d. 48 h.

Fig.3 SEM images of zeolites L(A), W(B), mechanical mixture(C) and L/W composite(D)

Fig.4 IR spectra of zeolites mechanical mixture(a) and L/W composite(b)

Fig.5 N2 adsorption-desorption isotherms of zeolites L(a), L/W composite(b), mechanical mixture(c) and W(d)

Table 2 Textural properties of the different zeolites

Zeolite	Surface area/(m²·g^-1)	Pore volume/(cm³·g^-1)	Pore size/nm
L	365.6	0.20	4.8
W	78.7	0.11	6.9
Mechanical mixture	222.5	0.15	6.0
L/W composite	324.8	0.21	7.9

Fig.6 FTIR spectra of pyridine adsorbed on zeolites L(a), W(b), mechanical mixture(c) and L/W composite(d) at 200 ℃(A) and 350 ℃(B)

Table 3 Surface acid amounts and the types of the different zeolites

Zeolite	Acid amount at 200 ℃/(μmol·g^-1)				Acid amount at 350 ℃/(μmol·g^-1)
Zeolite	L	B	L+B	B/L	L	B	L+B	B/L
L	90.0	157.3	247.3	1.74	74.4	72.3	146.7	0.97
W	12.0	23.0	35.0	1.91	11.4	14.3	25.7	1.25
Mechanical mixture	27.3	96.2	123.5	3.52	20.7	50.3	71.0	2.43
L/W composite	119.4	148.8	268.2	1.25	102.9	70.2	173.1	0.68

Fig.7 Raman spectra of catalysts L(a), W(b), mechanical mixture(c) and L/W composite(d)

Fig.8 H2-TPR spectra of catalysts L(a), W(b), mechanical mixture(c) and L/W composite(d)

Table 4 Hydro-upgrading results of FCC gasoline over catalysts*

Catalyst	P	i-P	O	N	A	RON	S/(mg·L^-1)	HDS(%)	ΔRON
Feed	6.21	36.15	27.70	8.41	21.53	91.59	429.1	/	/
L	10.97	46.79	9.06	11.83	21.34	89.35	49.8	88.3	-2.24
W	11.01	46.11	8.98	11.68	22.22	90.01	48.6	88.7	-1.58
Mechanical mixture	10.98	45.71	8.50	11.71	23.10	90.23	35.6	91.7	-1.36
L/W composite	9.69	47.31	8.57	11.05	23.37	90.44	28.6	93.3	-1.15

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