Synthesis of high-silica ZSM-5 with seeds in the presence of ethanol and amine

Mendonça, T. R. D.; Santos, J. R.; Sarmento, L. R. A.; Silva, D. C. M.; Cysneiros, O. M. S.; Silva, A. O. S.

doi:10.1590/0366-69132019653752705

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Articles • Cerâmica 65 (375) • Jul-Sep 2019 • https://doi.org/10.1590/0366-69132019653752705 copy

Synthesis of high-silica ZSM-5 with seeds in the presence of ethanol and amine

Síntese da ZSM-5 de alto teor de sílica com sementes na presença de etanol e aminas

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The possibility of crystallization of ZSM-5 with high Si/Al ratio was evaluated through the combined use of crystallization seeds and organic compounds that are not conventional directing agents for ZSM-5 (ethanol, methylamine, ethylamine, propylamine, butylamine, isopropylamine and diethylamine) in order to find a less toxic and costly route of synthesis. In addition, the influence of the stirring during the crystallization step on the properties of the ZSM-5 obtained in these synthesis conditions was verified. The obtained zeolites were analyzed by X-ray diffractometry in order to understand the effects of the templates. The analyses of NH₃-TPD, nitrogen adsorption, SEM, and TG/DTA were performed for the samples with better crystallinity. The procedure was successfully employed for the synthesis of MFI samples using propylamine as an alternative structure-directing agent. Its mean crystallite size ranged from 23 to 24 nm and was efficient in the cracking reaction of n-hexane.

Keywords:
ZSM-5; seed crystals; high silica; amines; ethanol

Table I Main parameters used in the synthesis of ZSM-5 under static conditions.

Sample	Gel composition (molar base)	Alternative	SDA/SiO₂	OH/SiO₂	Time
Sample	Al₂O₃:SiO₂:Na₂O:H₂SO₄:H₂O	SDA^a	molar ratio	molar ratio	(h)
Z2	1.0:150:51.70:40.45:3000	ETH	1.0	0.15	15
Z3	1.0:150:51.70:40.45:3000	ETH	3.0	0.15	21
Z4	1.0:150:51.70:36.70:3000	ETH	1.5	0.2	21
Z5	1.0:150:51.70:36.70:3000	ETH	3.0	0.2	21
Z6	1.0:150:48.42:33.42:3000	MET	0.1	0.2	21
Z7	1.0:150:48.42:33.42:3000	IPA	0.1	0.2	21
Z8	1.0:150:48.42:33.42:3000	BUT	0.1	0.2	24
Z9	1.0:150:48.42:33.42:3000	PRO	0.1	0.2	18
Z10	1.0:150:48,42:33,42:3000	ETI	0.1	0.2	21
Z11	1.0:150:48.42:33.42:3000	DIE	0.1	0.2	18
Z12	1.0:150:48.42:40.92:3000	PRO	0.1	0.1	21
Z13	1.0:150:48.42:40.92:3000	PRO+ETH	0.1+0.5	0.1	18
Z14	1.0:150:48.42:40.92:3000	PRO	0.2	0.1	21

Table II Main parameters used in ZSM-5 synthesis with stirring during crystallization.

Sample	Gel composition (molar base)	Alternative	SDA/SiO₂	OH/SiO₂	Time
Sample	Al₂O₃:SiO₂:Na₂O:H₂SO₄:H₂O	SDA^a	molar ratio	molar ratio	(h)
Z3-S	1.0:150:51.70:40.45:3000	ETH	3.0	0.15	21
Z5-S	1.0:150:51.70:36.70:3000	ETH	3.0	0.2	21
Z9-S	1.0:150:48.42:33.42:3000	PRO	0.1	0.2	18
Z12-S	1.0:150:48.42:40.92:3000	PRO	0.1	0.1	21
Z13-S	1.0:150:48.42:40.92:3000	PRO+ETH	0.1+0.5	0.1	18
Z14-S	1.0:150:48.42:40.92:3000	PRO	0.2	0.1	21

Table III Solid yield, mean crystallite size, relative crystallinity and phase distribution for samples synthesized under static conditions.

Sample	Solid yield^a	Crystallite size	Crystallinity	Product phase^b
Sample	(%)	(nm)	(%)	Product phase^b
Z2	88	23	72	Z
Z3	82	23	95	Z/M
Z4	73	22	90	Z/M
Z5	88	23	96	Z/M
Z6	79	23	39	Z/M
Z7	99	22	23	Z/M
Z8	76	23	79	Z/M
Z9	65	23	105	Z/M
Z10	67	23	56	Z/M
Z11	69	25	75	Z/M
Z12	89	23	97	Z/M
Z13	78	24	107	Z/M
Z14	76	23	113	Z/M

Table IV Solid yield, mean crystallite size, relative crystallinity and phase distribution for samples synthesized under stirring.

Sample	Solid yield^a	Crystallite size	Crystallinity	Product phase^b
Sample	(%)	(nm)	(%)	Product phase^b
Z3-S	87	22	8	Z/C
Z5-S	71	21	32	Z/C
Z9-S	77	17	62	Z/M
Z12-S	85	20	36	Z/C
Z13-S	89	17	78	Z/M/C
Z14-S	86	17	85	Z/C

Table V Textural properties obtained by adsorption of N2 and acidity measurements determined by NH3-TPD.

Sample	S_BET ^a	S_E ^b	S_Mic ^c	V_T ^d	V_Mic ^e	D^f	HF^g	Acid amount		S/W ratio^h
	S_BET ^a	S_E ^b	S_Mic ^c	V_T ^d	V_Mic ^e	D^f		(μmol.g^-1)
	(m².g^-1)	(m².g^-1)	(m².g^-1)	(cm³.g^-1)	(cm³.g^-1)	(nm)		W^h	S^h
Z5	285	187	98	0.25	0.04	6.3	0.10	179	102	0.57
Z9	285	126	158	0.25	0.07	7.5	0.12	234	118	0.50
Z12	244	98	145	0.14	0.07	6.8	0.20	235	122	0.52
Z13	340	205	135	0.20	0.06	4.7	0.18	225	132	0.59
Z14	316	125	191	0.16	0.09	4.4	0.22	255	298	1.17

Table VI Conversion, coke content, and distribution of products for the cracking of n-hexane.

Cracking product	Z5	Z9	Z12	Z13	Z14
Conversion^a (%)	45	73	64	67	65
Coke content^b (%)	1.4	1.9	2.6	4.0	3.0
Distribution of products (wt%)
Methane	2	3	3	3	2
Ethane	10	9	9	9	10
Ethene	12	16	15	16	15
Propane	16	18	18	18	18
Propene	35	29	29	29	31
≥C4	25	25	29	25	26
Total (%)	100	100	100	100	100

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