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Synthesis of Ferrierite-Type Zeolite in the Presence of a Catalytic Amount of Pyrrolidine and Sodium Bis(2-ethyhlhexyl) Sulfosuccinate
Journal of Colloid and Interface Science 236, 47–51 (2001) doi:10.1006/jcis.2000.7390, available online at http://www.idealibrary.com on
Synthesis of Ferrierite-Type Zeolite in the Presence of a Catalytic Amount of Pyrrolidine and Sodium Bis(2-ethyhlhexyl) Sulfosuccinate Ranjeet Kaur Ahedi,∗,1 A. N. Kotasthane,∗ B. S. Rao,∗ Abhijit Manna,† and B. D. Kulkarni† ∗ Catalysis Division, †Chemical Engg. Division, National Chemical Laboratory, Pune 411 008, India E-mail: [email protected], [email protected], [email protected]. Received February 8, 2000; accepted December 18, 2000
knowledge on the synthesis of ferrierite microporous materials in aqueous media in the presence of an anionic surfactant, AOT. In this paper we report the synthesis of FER topology in the presence of an anionic surfactant, AOT. The presence of a catalytic amount of AOT has been found to have a profound effect on the crystallite size, morphology, and habit. The major advantage of this synthesis method is that the template required is reduced almost six times. Ferrierite produced by this method exhibits properties similar to the one synthesized by the conventional route and thus hazardous effects of organo-amine compounds are reduced to a certain extent.
Synthesis of ferrierite (FER) type zeolite with varying Si to Al ratios in the presence of a catalytic amount of pyrrolidine and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in aqueous media is reported. The surfactant moieties direct pyrrolidine molecules in a particular fashion, resulting in a sixfold decrease in the required amount of template as compared to conventional procedure, for FER crystallization. The product obtained was highly crystalline and pure. In the presence of AOT alone, ferrierite co-crystallized with the ZSM-5 phase, indicating AOT is not acting as a structuredirecting agent and a small concentration of pyrrolidine (∼2 wt%) template is essential for the ferrierite crystallization. A scanning electron micrograph showed uniformity in crystals (average 2– 3 µm) consisting of broad plate type morphology. The crystal structure of FER (AOT/Py) maintains structural integrity until about 1000◦ C. FER (AOT/Py) has been further characterized by employing XRD, XRF, IR, and TG/DTA techniques. °C 2001 Academic Press Key Words: anionic surfactant (AOT); microdroplet formation; reduced template (pyrrolidine).
EXPERIMENTAL
Reactants The reactants used were sodium silicate (28.9 wt% SiO2 and 8.4 wt% Na2 O), Al2 (SO4 )3 · 16H2 O (Loba Chemie), pyrrolidine (99% SRL), and sodium bis(2-ethylhexyl) sulfosuccinate, i.e., AOT (Sigma) an anionic surfactant with two nonpolar tails.
INTRODUCTION
Formulation of the Hydrothermal System
After the first report on zeolite synthesis using amines and quaternary ammonium cations by Barrer and Denny (1), templated synthesis of zeolite materials with high organic amines reduces the crystallization period. Kumar et al. (3) successfully synthesized a number of zeolites in a shorter crystallization time using promoting media. The use of surfactant molecules during zeolite crystal growth can also have drastic effects. Recently, a number of reports describing the synthesis of surfactant/ inorganic composite materials using a variety of cationic and anionic surfactant species have appeared in the literature (4, 5). Dutta et al. (6) studied the influence of reverse micelles on the growth of zincophosphates (ZnPO system) using AOT in a nonaqueous medium. Synthesis of microporous materials in aqueous as well as nonaqueous mediums is also well established. A number of reports describing various preparative methods for obtaining ferrierite microporous materials (7–13) are available in the literature. There is, however, no report to the best of our 1
Typical synthesis involved the mixing of 52.5 g of sodium silicate in 30 g of distilled water and 1.0 g of AOT dissolved in 2 ml of pyrrolidine and 10 g distilled water under stirring. The gel was stirred for 1 h, and then Al2 (SO4 )3 · 16H2 O (2.4 g dissolved in 30 g of distilled water) was added. To the gel, 20 g of distilled water was finally added. This gel was stirred for another 1 h and heated in a stainless steel Parr (model 4842, 300 ml) autoclave in the temperature range 413–433 K for 40– 60 h. The samples with SiO2 /Al2 O3 ratios ranging between 30 and 80 were synthesized in a similar manner. The crystalline solid obtained was filtered, washed, dried at 383 K, and then identified by XRD. The as-synthesized sample was subjected to calcination in air up to 823 K to yield the Na form, which was then converted to its active form by multiple ion exchange treatments with (2 M) ammonium nitrate solution and calcined at 773 K for 5 h. The initial gel composition was 20Na2 O : 6.6pyrrolidine : 66SiO2 : Al2 O3 : 0.47AOT : 1600H2 O.
To whom correspondence should be addressed. 47
0021–9797/01 $35.00
C 2001 by Academic Press Copyright ° All rights of reproduction in any form reserved.
48
AHEDI ET AL.
CHARACTERIZATION
The extent of crystallization and phase purity was evaluated by recording X-ray diffractograms using CuK α radiation (Rigaku, ˚ The morphology and the habit D III Max VC, λ = 1.5404 A). of the crystalline phase of the FER product were examined on a Stereoscan 440, Cambridge, U.K., electron microscope. The chemical composition of the products in their Na form was established by wavelength dispersive XRF (3070, Rigaku) using lithium tetraborate as the flux. The thermoanalytical measurements were performed on the automatic TG/DTA (SETRAM 92) under flowing air (3 dm3 h−1 ) at a heating rate of 10 K min−1 . Framework FTIR spectra were recorded on a Perkin–Elmer 16 PCFT-IR instrument in the range 1300 to 400 cm1 . The BET surface area was determined on an Omnisorb 100CX Coulter in P/P0 between 0.006 and 0.3. RESULTS AND DISCUSSION
Synthesis Table 1 summarizes the physico-chemical properties of ferrierite synthesized using the pyrrolidine/AOT system. Ferrierite (AOT/Py) samples with SiO2 /Al2 O3 ratios in the range 30 to 80 were synthesized. Figures 1a–1c represent the XRD patterns for ferrierite synthesized with a SiO2 /Al2 O3 ratio of 48 and 68 and with low AOT (Table 1, samples 3, 4, and 7, respectively) in their calcined forms. The samples were found to be highly crystalline and pure. Ferrierite samples with high output SiO2 /Al2 O3 ratios could be synthesized (Table 1, sample 4) by this method. The yields were found to be comparable to the sample synthesized by the conventional route (Table 1, sample 1). However, when the SiO2 /Al2 O3 ratio was increased to 250 and above, ferrierite crystallized with low yields. When AOT alone was used in the synthesis gel, a mixed phase, i.e., FER + ZSM-5, resulted (Table 1, sample 5), indicating that a catalytic amount (0.02 mol) of pyrrolidine was essential for ferrierite synthesis. Ferrierite crystallized in 0.02 mol of pyrrolidine alone but with poor yield (Table 1, sample 8). However, the addition of AOT TABLE 1 Physico-chemical Properties of Ferrierite Synthesized in the Presence of AOT SiO2 /Al2 O3 Sample no. gel product
AOT (mol)
Pyrrolidine (mol)
1 2 3 4 5
66 40 66 80 60
32 30 48 68 —
— 0.0025 0.0025 0.0025 0.0025
0.1197 0.0253 0.0253 0.0253 —
6 7 8
60 60 60
50 52 30
0.0009 0.0017 —
0.0253 0.0253 0.0253
Product FER FER FER FER FER + ZSM-5 FER FER FER
Surface Yield area (%) (m2 /g) 60 60 65 62 60
251.4 260.8 258.3 252.7 —
60 65 62
256.9 250.5 248.1
FIG. 1. X-ray diffraction patterns for ferrierite (AOT/Py) with SiO2 /Al2 O3 : (a) 48, (b) 68, and (c) low AOT.
under similar conditions led to an increase in yield and improved the output SiO2 /Al2 O3 (Table 1, sample 3). The concentration of AOT varied in the range 0.0009–0.0025 and the effect was studied. Pure ferrierite could be crystallized, even in low concentrations of AOT (Table 1, sample 6). Role of AOT When the crystallization was carried out in the absence of pyrrolidine (Table 1, sample 5), ZSM-5 co-crystallized with
SYNTHESIS OF FERRIERITE-TYPE ZEOLITE
49
Framework IR Spectra Figure 5, (a)–(c), displays the framework IR spectra of the samples 4, 3, and 2 (Table 1) synthesized in the AOT/Py
FIG. 2. Schematic representation of microdroplet formation in the gel system containing water/AOT/pyrrolidine and salts. The pyrrolidine molecules are concentrated in and around the stern layer.
ferrierite, indicating that AOT is not acting as a structuredirecting agent. The concentration of surfactant (AOT) was above the CMC (critical micelle concentration) value. The formation of a milky emulsion indicated the formation of microdroplets, which are beyond the range (larger size) of microemulsion. The core of a microdroplet is the nonpolar region and the stern layer is the polar region. The polar–polar and nonpolar– nonpolar interactions orient the pyrrolidine molecule in a particular fashion, as shown in Fig. 2. This type of arrangement may increase the interaction between pyrrolidine and silicate and/or aluminum species. Thus, the excess quantity of pyrrolidine molecules required as “space filler” was avoided due to microdroplet formation. This may be the reason for the very small amount of pyrrolidine required during the FER crystallization. SEM Figure 3a displays the scanning electron micrograph for the FER sample (Table 1, sample 3) synthesized in the presence of AOT. It can be seen that the crystals exhibit rectangular plate type morphology. Smith et al. (14) also reported a platelike morphology for ferrierite crystals. Figure 3b shows the magnified image of the sample. From the SEM it may be assumed that the crystallization started between parts of the stern layer of the microdroplets and pyrrolidine molecules of the stern layer monitor the crystal growth. So the droplets act as a mimic of crystallization and space filler for the reaction system and not as a template for the ferrierite system (Fig. 4). Figure 3c represents the sample synthesized in the absence of a surfactant (Table 1, sample 1). When we compare the SEM (Figs. 3a and 3c), it is clear that we get crystals with a uniform morphology using AOT.
FIG. 3. (a) Scanning electron micrograph of ferrierite (AOT/Py) sample 3; (b) scanning electron micrograph of ferrierite (AOT/Py) sample 3; (c) scanning electron micrograph of ferrierite sample synthesized in the absence of AOT (sample 1, Table 1).
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AHEDI ET AL.
FIG. 4. Schematic representation of probable crystal space between two microdroplets.
FIG. 6. TG/DTA curves for samples 2 and 3.
system. The spectra were found to be similar to those obtained for the pyrrolidine system alone. A characteristic absorption band around 1218 cm−1 (due to Si–O symmetric stretching) was observed. The absorbance around 580 cm−1 confirms the presence of distorted double (DDR-5) five-membered rings (15) present in the ferrierite framework. The absorbance around 1071, 723, and 480 cm−1 can be assigned to the internal vibration of tetrahedral silica (16). The IR spectra for all the samples synthesized were identical except the strongest band corresponding to asymmetric stretching was found to shift to a lower frequency for the sample with a low SiO2 /Al2 O3 ratio. This must be due to the change occurring in the force constant of the T–O bond by aluminum insertion. Thermoanalytical Measurements (TG/DTA) Representative thermoanalytical (TG/DTA) curves are presented for samples 2 and 3 in their as-synthesized forms in Fig. 6, (a) and (b), respectively. The TG curve indicates a continued weight loss of ∼2.0 wt% mainly due to the dehydration occurring from the FER cavities in the low-temperature range. The DTA curve obtained in the air atmosphere reveals significant changes, which are mainly due to the oxidative decomposition of the occluded AOT/Py. A strong exotherm around 760 K and a weak exotherm around 873 K is attributed to the oxidative decomposition of the AOT/Py moieties occluded in the framework. Further, no major transformations were observed in the DTA curve, which indicate structural stability up to 1200 K of the FER system. CONCLUSIONS
FIG. 5. Framework region IR spectra of the samples 4, 3, and 2 (Table 1), respectively.
Ferrierite zeolite has been synthesized hydrothermally using catalytic amounts of pyrrolidine and anionic surfactant AOT in good yields. Large crystals of ferrierite with uniform particle
SYNTHESIS OF FERRIERITE-TYPE ZEOLITE
size were obtained. Ferrierite with higher output SiO2 /Al2 O3 ratios could be crystallized without any impurity phase. The use of hazardous amine (pyrrolidine) is reduced considerably by this method. ACKNOWLEDGMENT R.K.A. thanks CSIR, New Delhi, for a Senior Research Fellowship.
REFERENCES 1. Barrer, R. M., and Denny, P. J., J. Chem. Soc. 971 (1961). 2. Lok, B. M., Cannan, T. R., and Messina, C. A., Zeolites 3, 282 (1983). 3. Kumar, R., Bhaumik, A., Ahedi, R. K., and Ganpathy, S., Nature 381, 298 (1996). 4. Huo, Q., Margolise, D. I., Ciesla, V., Feng, P., Gier, T. E., Sieger, P., Leon, R., Petroff, P. M., Sch¨uth, F., and Stucky, G. D., Nature, 368, 317 (1994).
51
5. Myatt, G. J., Budd, P. M., Price, C., Hollway, F., and Carr, S. W., Zeolites, 14, 190 (1994). 6. Dutta, P. K., Jakupia, M., Salvati, L., Reddy, K. S. N., and Ansari, R. R., Surf. Stud. Sci. Catal. 84, 235 (1994). 7. Kibby, C. L., Perotta, A. J., and Massoth, F. E., J. Catal. 35, 256 (1974). 8. Kibby, C. L., Rosinski, E. J., and Rubin, M. K., U.S. Patent 4,016,245, 1977, assigned to Mobil Oil Corp. 9. Nanne, J. M., Post, M. F. M., and Stork, W. H. J., EPA 12 473, 1979, assigned to Shell Int. Res. 10. Fjellvag, H., Lillerud, K. P., Norby, P., and Sorby, K., Zeolites 9, 152 (1989). 11. Jin, Y. S., Auroux, A., and Vedrine, J. C., Appl. Catal. 37, 1 (1989). 12. Jacobs, P. A., and Martens, J. A., in “Synthesis of High Silica Aluminosilicate Zeolites,” Vol. 33, p. 218. Elsevier, Amseterdam, 1987. 13. Ahedi, R. K., and Kotasthane, A. N., J. Porous Mater. 4, 171 (1997). 14. Smith, W. J., Dewing, J., and Dwyer, J., J. Chem. Soc. Faraday Trans. 1 85, 3623 (1989). 15. Jacobs, P. A., Bayer, H. K., and Valyon, J., Zeolites 1, 161 (1981). 16. Flanigen, E. M., Khatami, H., and Szymanski, H., Adv. Chem. Ser. 101, 201 (1971).
Synthesis of Ferrierite-Type Zeolite in the Presence of a Catalytic Amount of Pyrrolidine and Sodium Bis(2-ethyhlhexyl) Sulfosuccinate Ranjeet Kaur Ahedi,∗,1 A. N. Kotasthane,∗ B. S. Rao,∗ Abhijit Manna,† and B. D. Kulkarni† ∗ Catalysis Division, †Chemical Engg. Division, National Chemical Laboratory, Pune 411 008, India E-mail: [email protected], [email protected], [email protected]. Received February 8, 2000; accepted December 18, 2000
knowledge on the synthesis of ferrierite microporous materials in aqueous media in the presence of an anionic surfactant, AOT. In this paper we report the synthesis of FER topology in the presence of an anionic surfactant, AOT. The presence of a catalytic amount of AOT has been found to have a profound effect on the crystallite size, morphology, and habit. The major advantage of this synthesis method is that the template required is reduced almost six times. Ferrierite produced by this method exhibits properties similar to the one synthesized by the conventional route and thus hazardous effects of organo-amine compounds are reduced to a certain extent.
Synthesis of ferrierite (FER) type zeolite with varying Si to Al ratios in the presence of a catalytic amount of pyrrolidine and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in aqueous media is reported. The surfactant moieties direct pyrrolidine molecules in a particular fashion, resulting in a sixfold decrease in the required amount of template as compared to conventional procedure, for FER crystallization. The product obtained was highly crystalline and pure. In the presence of AOT alone, ferrierite co-crystallized with the ZSM-5 phase, indicating AOT is not acting as a structuredirecting agent and a small concentration of pyrrolidine (∼2 wt%) template is essential for the ferrierite crystallization. A scanning electron micrograph showed uniformity in crystals (average 2– 3 µm) consisting of broad plate type morphology. The crystal structure of FER (AOT/Py) maintains structural integrity until about 1000◦ C. FER (AOT/Py) has been further characterized by employing XRD, XRF, IR, and TG/DTA techniques. °C 2001 Academic Press Key Words: anionic surfactant (AOT); microdroplet formation; reduced template (pyrrolidine).
EXPERIMENTAL
Reactants The reactants used were sodium silicate (28.9 wt% SiO2 and 8.4 wt% Na2 O), Al2 (SO4 )3 · 16H2 O (Loba Chemie), pyrrolidine (99% SRL), and sodium bis(2-ethylhexyl) sulfosuccinate, i.e., AOT (Sigma) an anionic surfactant with two nonpolar tails.
INTRODUCTION
Formulation of the Hydrothermal System
After the first report on zeolite synthesis using amines and quaternary ammonium cations by Barrer and Denny (1), templated synthesis of zeolite materials with high organic amines reduces the crystallization period. Kumar et al. (3) successfully synthesized a number of zeolites in a shorter crystallization time using promoting media. The use of surfactant molecules during zeolite crystal growth can also have drastic effects. Recently, a number of reports describing the synthesis of surfactant/ inorganic composite materials using a variety of cationic and anionic surfactant species have appeared in the literature (4, 5). Dutta et al. (6) studied the influence of reverse micelles on the growth of zincophosphates (ZnPO system) using AOT in a nonaqueous medium. Synthesis of microporous materials in aqueous as well as nonaqueous mediums is also well established. A number of reports describing various preparative methods for obtaining ferrierite microporous materials (7–13) are available in the literature. There is, however, no report to the best of our 1
Typical synthesis involved the mixing of 52.5 g of sodium silicate in 30 g of distilled water and 1.0 g of AOT dissolved in 2 ml of pyrrolidine and 10 g distilled water under stirring. The gel was stirred for 1 h, and then Al2 (SO4 )3 · 16H2 O (2.4 g dissolved in 30 g of distilled water) was added. To the gel, 20 g of distilled water was finally added. This gel was stirred for another 1 h and heated in a stainless steel Parr (model 4842, 300 ml) autoclave in the temperature range 413–433 K for 40– 60 h. The samples with SiO2 /Al2 O3 ratios ranging between 30 and 80 were synthesized in a similar manner. The crystalline solid obtained was filtered, washed, dried at 383 K, and then identified by XRD. The as-synthesized sample was subjected to calcination in air up to 823 K to yield the Na form, which was then converted to its active form by multiple ion exchange treatments with (2 M) ammonium nitrate solution and calcined at 773 K for 5 h. The initial gel composition was 20Na2 O : 6.6pyrrolidine : 66SiO2 : Al2 O3 : 0.47AOT : 1600H2 O.
To whom correspondence should be addressed. 47
0021–9797/01 $35.00
C 2001 by Academic Press Copyright ° All rights of reproduction in any form reserved.
48
AHEDI ET AL.
CHARACTERIZATION
The extent of crystallization and phase purity was evaluated by recording X-ray diffractograms using CuK α radiation (Rigaku, ˚ The morphology and the habit D III Max VC, λ = 1.5404 A). of the crystalline phase of the FER product were examined on a Stereoscan 440, Cambridge, U.K., electron microscope. The chemical composition of the products in their Na form was established by wavelength dispersive XRF (3070, Rigaku) using lithium tetraborate as the flux. The thermoanalytical measurements were performed on the automatic TG/DTA (SETRAM 92) under flowing air (3 dm3 h−1 ) at a heating rate of 10 K min−1 . Framework FTIR spectra were recorded on a Perkin–Elmer 16 PCFT-IR instrument in the range 1300 to 400 cm1 . The BET surface area was determined on an Omnisorb 100CX Coulter in P/P0 between 0.006 and 0.3. RESULTS AND DISCUSSION
Synthesis Table 1 summarizes the physico-chemical properties of ferrierite synthesized using the pyrrolidine/AOT system. Ferrierite (AOT/Py) samples with SiO2 /Al2 O3 ratios in the range 30 to 80 were synthesized. Figures 1a–1c represent the XRD patterns for ferrierite synthesized with a SiO2 /Al2 O3 ratio of 48 and 68 and with low AOT (Table 1, samples 3, 4, and 7, respectively) in their calcined forms. The samples were found to be highly crystalline and pure. Ferrierite samples with high output SiO2 /Al2 O3 ratios could be synthesized (Table 1, sample 4) by this method. The yields were found to be comparable to the sample synthesized by the conventional route (Table 1, sample 1). However, when the SiO2 /Al2 O3 ratio was increased to 250 and above, ferrierite crystallized with low yields. When AOT alone was used in the synthesis gel, a mixed phase, i.e., FER + ZSM-5, resulted (Table 1, sample 5), indicating that a catalytic amount (0.02 mol) of pyrrolidine was essential for ferrierite synthesis. Ferrierite crystallized in 0.02 mol of pyrrolidine alone but with poor yield (Table 1, sample 8). However, the addition of AOT TABLE 1 Physico-chemical Properties of Ferrierite Synthesized in the Presence of AOT SiO2 /Al2 O3 Sample no. gel product
AOT (mol)
Pyrrolidine (mol)
1 2 3 4 5
66 40 66 80 60
32 30 48 68 —
— 0.0025 0.0025 0.0025 0.0025
0.1197 0.0253 0.0253 0.0253 —
6 7 8
60 60 60
50 52 30
0.0009 0.0017 —
0.0253 0.0253 0.0253
Product FER FER FER FER FER + ZSM-5 FER FER FER
Surface Yield area (%) (m2 /g) 60 60 65 62 60
251.4 260.8 258.3 252.7 —
60 65 62
256.9 250.5 248.1
FIG. 1. X-ray diffraction patterns for ferrierite (AOT/Py) with SiO2 /Al2 O3 : (a) 48, (b) 68, and (c) low AOT.
under similar conditions led to an increase in yield and improved the output SiO2 /Al2 O3 (Table 1, sample 3). The concentration of AOT varied in the range 0.0009–0.0025 and the effect was studied. Pure ferrierite could be crystallized, even in low concentrations of AOT (Table 1, sample 6). Role of AOT When the crystallization was carried out in the absence of pyrrolidine (Table 1, sample 5), ZSM-5 co-crystallized with
SYNTHESIS OF FERRIERITE-TYPE ZEOLITE
49
Framework IR Spectra Figure 5, (a)–(c), displays the framework IR spectra of the samples 4, 3, and 2 (Table 1) synthesized in the AOT/Py
FIG. 2. Schematic representation of microdroplet formation in the gel system containing water/AOT/pyrrolidine and salts. The pyrrolidine molecules are concentrated in and around the stern layer.
ferrierite, indicating that AOT is not acting as a structuredirecting agent. The concentration of surfactant (AOT) was above the CMC (critical micelle concentration) value. The formation of a milky emulsion indicated the formation of microdroplets, which are beyond the range (larger size) of microemulsion. The core of a microdroplet is the nonpolar region and the stern layer is the polar region. The polar–polar and nonpolar– nonpolar interactions orient the pyrrolidine molecule in a particular fashion, as shown in Fig. 2. This type of arrangement may increase the interaction between pyrrolidine and silicate and/or aluminum species. Thus, the excess quantity of pyrrolidine molecules required as “space filler” was avoided due to microdroplet formation. This may be the reason for the very small amount of pyrrolidine required during the FER crystallization. SEM Figure 3a displays the scanning electron micrograph for the FER sample (Table 1, sample 3) synthesized in the presence of AOT. It can be seen that the crystals exhibit rectangular plate type morphology. Smith et al. (14) also reported a platelike morphology for ferrierite crystals. Figure 3b shows the magnified image of the sample. From the SEM it may be assumed that the crystallization started between parts of the stern layer of the microdroplets and pyrrolidine molecules of the stern layer monitor the crystal growth. So the droplets act as a mimic of crystallization and space filler for the reaction system and not as a template for the ferrierite system (Fig. 4). Figure 3c represents the sample synthesized in the absence of a surfactant (Table 1, sample 1). When we compare the SEM (Figs. 3a and 3c), it is clear that we get crystals with a uniform morphology using AOT.
FIG. 3. (a) Scanning electron micrograph of ferrierite (AOT/Py) sample 3; (b) scanning electron micrograph of ferrierite (AOT/Py) sample 3; (c) scanning electron micrograph of ferrierite sample synthesized in the absence of AOT (sample 1, Table 1).
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AHEDI ET AL.
FIG. 4. Schematic representation of probable crystal space between two microdroplets.
FIG. 6. TG/DTA curves for samples 2 and 3.
system. The spectra were found to be similar to those obtained for the pyrrolidine system alone. A characteristic absorption band around 1218 cm−1 (due to Si–O symmetric stretching) was observed. The absorbance around 580 cm−1 confirms the presence of distorted double (DDR-5) five-membered rings (15) present in the ferrierite framework. The absorbance around 1071, 723, and 480 cm−1 can be assigned to the internal vibration of tetrahedral silica (16). The IR spectra for all the samples synthesized were identical except the strongest band corresponding to asymmetric stretching was found to shift to a lower frequency for the sample with a low SiO2 /Al2 O3 ratio. This must be due to the change occurring in the force constant of the T–O bond by aluminum insertion. Thermoanalytical Measurements (TG/DTA) Representative thermoanalytical (TG/DTA) curves are presented for samples 2 and 3 in their as-synthesized forms in Fig. 6, (a) and (b), respectively. The TG curve indicates a continued weight loss of ∼2.0 wt% mainly due to the dehydration occurring from the FER cavities in the low-temperature range. The DTA curve obtained in the air atmosphere reveals significant changes, which are mainly due to the oxidative decomposition of the occluded AOT/Py. A strong exotherm around 760 K and a weak exotherm around 873 K is attributed to the oxidative decomposition of the AOT/Py moieties occluded in the framework. Further, no major transformations were observed in the DTA curve, which indicate structural stability up to 1200 K of the FER system. CONCLUSIONS
FIG. 5. Framework region IR spectra of the samples 4, 3, and 2 (Table 1), respectively.
Ferrierite zeolite has been synthesized hydrothermally using catalytic amounts of pyrrolidine and anionic surfactant AOT in good yields. Large crystals of ferrierite with uniform particle
SYNTHESIS OF FERRIERITE-TYPE ZEOLITE
size were obtained. Ferrierite with higher output SiO2 /Al2 O3 ratios could be crystallized without any impurity phase. The use of hazardous amine (pyrrolidine) is reduced considerably by this method. ACKNOWLEDGMENT R.K.A. thanks CSIR, New Delhi, for a Senior Research Fellowship.
REFERENCES 1. Barrer, R. M., and Denny, P. J., J. Chem. Soc. 971 (1961). 2. Lok, B. M., Cannan, T. R., and Messina, C. A., Zeolites 3, 282 (1983). 3. Kumar, R., Bhaumik, A., Ahedi, R. K., and Ganpathy, S., Nature 381, 298 (1996). 4. Huo, Q., Margolise, D. I., Ciesla, V., Feng, P., Gier, T. E., Sieger, P., Leon, R., Petroff, P. M., Sch¨uth, F., and Stucky, G. D., Nature, 368, 317 (1994).
51
5. Myatt, G. J., Budd, P. M., Price, C., Hollway, F., and Carr, S. W., Zeolites, 14, 190 (1994). 6. Dutta, P. K., Jakupia, M., Salvati, L., Reddy, K. S. N., and Ansari, R. R., Surf. Stud. Sci. Catal. 84, 235 (1994). 7. Kibby, C. L., Perotta, A. J., and Massoth, F. E., J. Catal. 35, 256 (1974). 8. Kibby, C. L., Rosinski, E. J., and Rubin, M. K., U.S. Patent 4,016,245, 1977, assigned to Mobil Oil Corp. 9. Nanne, J. M., Post, M. F. M., and Stork, W. H. J., EPA 12 473, 1979, assigned to Shell Int. Res. 10. Fjellvag, H., Lillerud, K. P., Norby, P., and Sorby, K., Zeolites 9, 152 (1989). 11. Jin, Y. S., Auroux, A., and Vedrine, J. C., Appl. Catal. 37, 1 (1989). 12. Jacobs, P. A., and Martens, J. A., in “Synthesis of High Silica Aluminosilicate Zeolites,” Vol. 33, p. 218. Elsevier, Amseterdam, 1987. 13. Ahedi, R. K., and Kotasthane, A. N., J. Porous Mater. 4, 171 (1997). 14. Smith, W. J., Dewing, J., and Dwyer, J., J. Chem. Soc. Faraday Trans. 1 85, 3623 (1989). 15. Jacobs, P. A., Bayer, H. K., and Valyon, J., Zeolites 1, 161 (1981). 16. Flanigen, E. M., Khatami, H., and Szymanski, H., Adv. Chem. Ser. 101, 201 (1971).