synthesis of zeolite ferrierite in the absence of inorganic cations

ELSEVIER Microporous Materials 7 (1996) 35-40

MICROPOROUS MATERIALS

Synthesis of zeolite ferrierite in the absence of inorganic cations

Tae Jin Kim a, Wha Seung Ahn a, Suk Bong Hong b,, a Department of Chemical Engineering, Inha University, lncheon 402-751, South Korea

b Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seou1130-650, South Korea

Received 28 July 1995; accepted 13 January 1996

Abstract

An attempt is made to prepare zeolite ferrierite in inorganic ion-free media using three different types of organic structure-directing agents: 1,4-diaminobutane (DB), ethylenediamine (ED) and pyrrolidine (py). The phase purity and crystal morphology of crystalline products are strongly dependent on the type and concentration of the organic amine added in the reaction mixture. It is found that ferrierite can be successfully synthesized when the reaction mixtures have the gel compositions: (i) (90-40)DB.AI2Oa-30SiO2.370H20, (ii) (90-30)ED.A1203.(20-30)- SiO2" 370H20 and (iii) (90-40)py" A1203 • (30-40)SIO2 • 370H20.

Keywords: Ferrierite synthesis; Inorganic cation-free media; Organic structure-directing agent; Crystal morphology

1. Introduction

The medium-pore zeolite ferrierite (FER topol- ogy) is of current interest because of its exceptional selectivity for the skeletal isomerization of 1-butene [1,2]. In addition, cobalt-exchanged ferrierite is reported to be active for the selective reduction of NOx, which remains a serious environmental problem [3].

The FER framework is based on chains of 5-rings, which are linked to give [54] polyhedral units. There are two types of intersecting channels in the structure. The main channels are parallel to the orthorhombic c-axis of the crystal and are outlined by elliptical 10-rings (4.3 × 5.5 .~ in diameter), while the side channels parallel to the b-axis are formed by 8-rings (3.4x4.8 .~ in diameter). Most of the ferrierite synthesis procedures which

* Corresponding author.

0927-6513/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved PII S0927-6513 (96)00024-7

are available in the literature include the use of an organic structure-directing agent in conjunction with some inorganic cation [4-10]. Thus, repeated ion exchange and calcination steps are necessary for obtaining its catalytically active form after the synthesis is complete. Furthermore, the presence of inorganic cations such as Na ÷ or K ÷ in the reaction mixture has been claimed to prevent the successful substitution of titanium into the pure- silica ZSM-5 framework [11]. However, little attention has been directed to the hydrothermal synthesis of ferrierite in the absence of inorganic cations [12,13].

The purpose of the present study is to crystallize ferrierite using an organic structure-directing agent alone and to compare its physical properties with that of ferrierite prepared by a conventional method where both an inorganic cation (Na ÷) and an organic structure-directing agent are used. Here we report the results obtained from ferrierite

36 T.J. Kim et al./Microporous Materials 7 (1996) 35-40

synthesis performed in inorganic ion-free media using three different types of organic amines: 1,4-diaminobutane (DB), ethylenediamine (ED) and pyrrolidine (py). These amines were chosen as structure-directing agents since they are used together with some inorganic cations in the synthesis of ferrierite and its structurally related materials. Particular emphasis is placed on the influence of the type and concentration of the organic structure-directing agent used in the ferrierite synthesis on the phase purity and crystal morphology of crystalline products. Marosi et al. [12] first prepared aluminosilicate ferrierite using DB in the inorganic ion-free system. In addition, Gies and Gunawardane [13] have synthesized the aluminum-free form of ferrierite with ED and boric acid as structure-directing agents. However, the use of py in preparing ferrierite in the absence of inorganic cations has not been attempted.

silicon, aluminum or sodium in selected samples was performed by a Jarrell-Ash Polyscan 61E inductively coupled plasma (ICP) spectrometer. Thermogravimetric analyses (TGA) and differential thermal analyses (DTA) were carried out in air on a Du Pont 950 thermogravimetric analyzer and a Simatzu differential analyzer, respectively. Approximately 20 mg of samples were used at a heating rate of 10°C'min -t. The nitrogen BET surface areas were measured on a Micromeritics ASAP 2000 analyzer. The crystal size and morphology were determined by a Hitachi Model X-650 scanning electron microscope.

3. Results and discussion

3.1. Ferrierite synthesis with or without using Na + ions

2. Experimental

The following reagents were used for the ferrierite synthesis with or without using inorganic cations: NaOH (Mallinckrodt), aluminium iso- propoxide (98%, Aldrich), Ludox AS-40 silica sol (Du Pont), 1,4-diaminobutane (99%, Aldrich), ethylenediamine (99%, Junsei) and pyrrolidine (99%, Aldrich). The synthesis of ferrierite in the presence of Na + was performed by a modification of the procedure described by Plank et al. [8]. The oxide composition of the final reaction mixture was fixed to 10R" 1.5Na2 O'A1203' 30SIO2" 370H20, where R is DB, ED or py. In order to crystallize ferrierite in the absence of Na + ions, we also prepared the reaction mixture with the oxide composition nR. A1203 • 30SIO2" 370H20, where n is varied as 10<n<90. The reaction mixture prepared was agitated at room temperature for 24 h, then sealed in a 24 ml Teflon-lined autoclave and kept at 175°C, without stirring under autogenous pressure, for a given period of time. The solid phase was filtered, thoroughly washed with distilled water and dried overnight at room temperature.

X-ray powder diffraction patterns of all zeolites prepared in this work were measured on a Philips PW1710 diffractometer. Chemical analysis for

Fig. 1 shows the X-ray powder diffraction patterns of the products synthesized in the presence of three different types of organic amines, with or without using Na +. The X-ray powder diffraction patterns given in Fig. l a reveal that DB and ED give a mixed phase of ZSM-5 and ferrierite, while py directs the synthesis of ferrierite. In addition, mordenite is obtained when the reaction mixture does not contain organic amine but does contain Na ÷. Therefore, it is most likely that the phase purity of crystalline products prepared in the presence of Na ÷ ions is dependent on the type of the organic amine used. The formation of ZSM-5 as an impurity during the ferrierite synthesis is not surprising since all three organic amines used in this work can serve as organic structure-directing agents for ZSM-5 [ 14-16]. For example, Valyocsik and Rollman [5] reported that ferrierite can be crystallized simultaneously with ZSM-5 when DB is used as structure-directing agent.

Fig. lb shows the X-ray powder diffraction patterns of the samples prepared without using Na ÷ ions. An early attempt to synthesize ferrierite in the absence of inorganic cations [ 12] included the use of organic structure-directing agent in large excess. Therefore, we have performed the synthesis of ferrierite using the reaction mixture with the oxide composition 90R. AIzO 3 • 30SiOz" 370H20, where R is DB, ED and py, respectively. The

T.J. Kim et al./Microporous Materials 7 (1996) 35-40 37

~E

(a) (b)

[ *

1'0 2'o 3'o 1'0 2'o 2 theta 2 theta

Fig. 1. X-ray diffraction patterns of ferrierites prepared with or without using Na ÷ ions: synthesized from the gel compositions of (a) 10R. 1.5Na203 'A1203" 30SIO2" 370H20 and (b) 90R-A1203.30SIO2" 370H20 at 175°C for 11 days. When py was used as a structure-directing agent in the Na÷-free system, the crystallization time was 15 days. Peaks marked by an asterisk are from a ZSM-5 impurity.

X-ray powder diffraction patterns in Fig. 1 b clearly show that ferrierite can be prepared in the absence of inorganic cations, regardless of the type of the organic amines used in this work. On the other hand, the crystallization rate appears to differ according to the type of the organic amine. When monoamine (py) was used as a structure-directing agent, ferrierite with a high crystallinity was obtained after crystallization at 175°C for 15 days. In the case of diamines (DB and ED), however, 10 days of hydrothermal reaction at the same temperature was sufficient to give a similar degree of crystallinity. The X-ray diffraction patterns of ferrierites prepared with organic amines alone are slightly different in peak intensity from that of natural ferrierite; in particular, the peak observed at 20--7.8 ° is significantly weaker for the ferrierite samples synthesized in this work. This has been attributed to the difference in preferred orientation of zeolite crystallites [17]. As marked by an asterisk in Fig. lb, however, ferrierite samples prepared in Na ÷-free media contain a trace amount of ZSM-5. The amount of ZSM-5 in crystalline products is significantly increased with decreasing concen-

tration of the organic amine in the reaction mixture (vide infra).

Table 1 lists the chemical compositions of ferrierites synthesized with and without Na ÷ ions in the presence of three different organic amines. These data were obtained from combining the chemical analysis for silicon, aluminum or sodium with the water and organic contents determined by TGA and DTA. As seen in Table 1, the SIO2/A1203 ratio of sample C is slightly lower than that of sample F. This indicates that less silicious ferrierite crystals are obtained when py is used as a structure- directing agent together with Na ÷ . However, the SiO2/A120 a ratios of ferrierites prepared in Na +-free media are not significantly different in the type of the organic amine used. If all DB and ED molecules in samples D and E exist as their completely protonated forms, the overall charge of these diamines cations per unit cell for these samples is larger than the framework negative charge. Therefore, it is most likely that some portion of the diamines in these samples is not protonated and exists as a space-filling agent. However, this situation is not the case for the py


Table 1 Physical properties of ferrierites synthesized with or without using Na ÷ ions in the presence of different types of organic structure- directing agents

Sample a Structure-directing Product ¢ Unit cell composition SiO2/A120 a ratio N2 BET surface agents used b area (m2/g)

A Na ÷, DB MFI, FER - - - B Na ÷, ED MFI, FER - - - C Na ÷, py FER py4.0NaLl(Als.lSia0.9)O72 • 3.5H20 12.1 363 D DB FER DBz.9(A14.sSial.s)O72 • 3.5H20 14.0 367 E ED FER EDa.z(A14.6SiaL4)O72 • 3.8H20 13.7 345 F py FER PYa.7(A14.2Si31.s)072" 1.5H20 15.1 325

a Samples A-C, synthesized from the reaction mixture 10R- 1.5Na20' A1203 • 30SIO2" 370H20 at 175°C for 10 days; samples D-F , synthesized from the reaction mixture 90R'A12Oa'30SiO2' 370H20 at 175°C. The crystallization time was 10 days for samples D and E, and 15 days for sample F. b Abbreviations for reagents: DB, 1,4-diaminobutane; ED, ethylenediamine; py, pyrrolidine.

If more than one phase is obtained, the phase in the highest concentration is listed first.

molecules in sample F, since the number of py molecules per unit cell is smaller than that of A1 atoms per unit cell.

Fig. 2 shows the scanning electron micrographs of the fen'ierites synthesized in the presence or absence of Na ÷ ions. Significant differences in the crystal morphology of ferrierites are observed. When Na ÷ is used in conjunction with py, 10 #m

spherical aggregates consisting of very small needles are observed. However, star-shaped partic- ulates of 10-15/~m are synthesized from the reaction mixture that contains py only. In addition, irregular piles of thin rectangular plate of 45-55/~m and square plate shaped crystals with a diameter of 30 m are obtained when DB and ED are used as a structure-directing agent, respectively. A plate-like form of ferrierite crystals is also reported by Smith et al. [9]. The scanning electron micrographs given in Fig. 2 clearly show that the crystal size and morphology of ferrierite are strongly influenced by the type of organic amine used.

lO pm 60 ~m (a) (b)

25 lain 20 p.m (c) (d)

Fig. 2. Scanning electron micrographs of ferrierites with or without using Na + ions synthesized with (a) Na + and py, (b) DB, (c) ED and (d) py. The synthesis conditions used are the same as those given in Fig. 1.

3.2. Effects of R/Al203 and Si02/AI203 ratios on the synthesis of ferrierite in Na +-free media

In order to test whether ferrierite can be prepared with a reduced amount of organic amine in inorganic cation-free media, we have attempted ferrierite synthesis using the reaction mixtures of which the R/AI203 ratios were varied from 90 to 10. The X-ray powder diffraction patterns given in Fig. 3 reveal that ferrierite with a high crystallinity can be prepared, even though the R/A1203 ratio of the reaction mixture is reduced from 90 to 40. Fig. 4 shows the scanning electron micrographs of the ferrierites prepared from the synthesis mixtures with different R/A1203 ratios. In general, the lower concentration of organic amine

T.J. Kirn et aL/Microporous Materials 7 (1996) 35-40 39

(a)

,'0 ~o 2 theta

,U,

M,,,N

3O

(b)

1'o ~o 30 2 theta

(e)

AI . • _

~ 3o

2 theta

Fig. 3. X-ray diffraction patterns of ferrierites synthesized with different concentrations of (a) DB, (b) ED and (c) py in the absence of Na + ions.

Table 2 Variations of the SiO2/A120 a ratios in the synthesis of ferrierite

Organic SiOz/ml203 Crystallization amine ratio in time at u sed reaction mixture a 175°C (days)

Product b

DB

ED

PY

50 10 MFI, FER 40 10 FER, MFI 30 10 FER 20 30 amorphous 10 50 amorphous

50 10 MFI, FER 40 10 FER, MFI 30 10 FER 20 36 FER 10 50 amorphous

50 15 FER, MFI 40 15 FER 30 15 FER 20 30 amorphous I0 50 amorphous

a Gel composition: 90R- A 1 2 0 3 " x S i O 2 • 370H20. b If more than one phase is obtained, the phase in concentration is first listed.

the highest

the reaction mixture has, the smaller crystals it produces. However, no noticeable changes in crystal morphology are observed in the amine concentration range studied here. When the R/AI203 ratio of the reaction mixture is lower than 40, the phase purity of crystalline products is dependent on the type of organic amine used. For example, the X-ray diffraction pattern of the crystalline product obtained from the reaction mixture with R/A120 3 = 10 shows that ZSM-5 rather than ferrierite is the main phase when DB is used as a structure-directing agent. However, the reaction mixture containing ED remains amorphous even after crystallization at 175°C for 30 days. Most likely, there is a minimum R/AI203 ratio for the synthesis of ferrierite in inorganic cation-free media.

Table 2 summarizes the results obtained from ferrierite synthesis performed using the reaction mixture with the oxide composition 90R. AI203xS iO2"370H20 , where x is varied from 10 to 50. It is found that the SiO2/ml20 3 ratio range leading to the successful ferrierite formation is very narrow. A highly crystalline ferrierite can be obtained only from the reaction mixture


(a) 30urn (b) 30 pm

ganic cation-flee media when the reaction mixtures have the gel composit ions: (i) ( 9 0 - 4 0 ) D B - AI203 • 30SIO2 • 370H20, (ii) ( 9 0 - 3 0 ) E D - A1203 • ( 20 -30 )S IO2"370H20 and (iii) ( 9 0 - 4 0 ) p y . A I 2 O a ' ( 3 0 - 4 0 ) S i O 2 ' 3 7 0 H 2 0 . The crystal morphology and crystallization rate are strongly dependent on the type and amoun t o f the organic- structure directing agent used. A m o n g the organic amines tested here, E D is found to be the best structure-directing agent, because o f the shorter crystallization time and easy removal o f t rapped organic molecules.

w

(c) 3o ~n (d) OO ~n

Acknowledgment

This work was supported by the Korea Institute o f Science and Technology under contract No. 2N13705.

(e) 20 pm (f) 10 pm

Fig. 4. Scanning electron micrographs of ferrierites obtained from sodium-free media with different organic amine concentrations, The composition of the reaction mixture used is nR. A120 a • 30SIO2 • 370H20, where nR is (a) 70DB, (b) 40DB, (c) 30DB, (d) 80ED, (e) 60py and (f) 40py.

with SiO2/A120 3 ratio o f 30, when DB is used as structure-directing agent. ZSM-5 format ion is favored using gels with higher SiO2/A12Oa ratios, while no solid material is obtained f rom the synthesis mixtures with SiO2/Al20 3 ratios lower than 30. E D and py direct the synthesis o f ferrierite, if the reaction mixtures have the SIO2/A1203 ratios o f 20-30 and 30-40, respectively. As stated earlier, however, a longer period o f crystallization time is necessary for the ferrierite format ion with py than with ED.

4. Conclusions

The overall results o f this study reveal that ferrierite can be successfully synthesized in inor-

References

[1] H.H. Mooiweer, K.P. de Jong, B. Kraushaar-Czarnetzki, W.H.J. Stork and B.C.H. Krutzen, Stud. Surf. Sci. Catal., 84 (1994) 2327.

[2] C.-L. O'Young, R.J. Pellet, D.G. Casey, J.R. Ugolini and R.A. Sawicki, J. Catal., 151 (1995) 467.

[3] Y. Li and J.N. Armor, Appl. Catal. B, 3 (1993) L1. [4] C.L. Kibby, A.J. Perrotta and F.E. Massoth, J. Catal., 35

(1974) 256. [5] E.W. Valyoscik and L.D. Rollmann, Zeolites, 5 (1985) 123. [6] L.D. Rollmann, Ger. Often. 2 817 575 (1978). [7] J.A. Kaduk, US Pat. 4 323 481 (1982). [8] C.J. Plank, E.J. Rosinski and M.K. Rubin, US Pat.

4 016 245 (1977). [9] W.J. Smith, J. Dewing and J. Dwyer, J. Chem. Soc.,

Faraday Trans. I, 85 (1989) 3623. [10] P.A. Jacobs and J.A. Martens, Synthesis of High-Silica

Aluminosilicate Zeolites, Elsevier, Amsterdam, 1987, p. 222.

[11] G. Bellusi and V. Fattore, Stud. Surf. Sci. Catal., 69 (1991) 79.

[12] L. Marosi, M. Schwarzmann and J. Stabenow, Eur. Pat. 0 049 386 A1 (1981).

[13] H. Gies and R.P. Gunawardane, Zeolites, 7 (1987) 442. [14] Z. Gabelica, P. Cavez-Bierman, P. Bodart, A. Gourgue

and J.B. Nagy, Stud. Surf. Sci. Catal., 24 (1985) 221. [15] J. Wilkasz, E. Stobiecka and B. Dudek, Zeolites, 13

(1993) 581. [16] S. Mintova, V. Valtchev, E. Vultcheva and S. Veleva,

Zeolites, 12 (1992) 210. [17] H. Fjellvag, K.P. Lillerud, P. Norby and K. Sorby,

Zeolites, 9 (1989) 152.

synthesis of zeolite ferrierite in the absence of inorganic cations

Documents